Computer modeling of the heattransfer in a powershift transmission

clutch under slippage/'

by

PAUL WARREN JOHNSON#

B.S., Kansas State University, 1984

A MASTER'S THESIS

submitted in partial fulfillment of the

requirements for the degree

MASTER OF SCIENCE

Department of Mechanical Engineering

KANSAS STATE UNIVERSITYManhattan, Kansas

1987

Approved by:

tejor Professor

TABLE OF CONTENTS A11207 306SD7

Chapter Page

I. INTRODUCTION 1

OBJECTIVE . 2

II. APPROACH 3

DEVELOPMENT OF CLUTCH HEAT TRANSFER MODEL . . 3

Description of Clutch 3

Lumped Clutch Analysis 5

Formulation of Instantaneous Clutch HeatTransfer Model 9

III. TEST EQUIPMENT 11

Transmission 11

Engine 11

Instrumentation 11

Data Acquisition System and Software 12

IV. PRELIMINARY TESTING 14

Purpose of Preliminary Testing 14

Measurement of Oil Flow Rate 14

Direct Method 14

Turbine Flowmeter 18

Summary of Preliminary Oil Flow Rate Testing 20

Measurement of Oil and Reaction Clutch PlateTemperatures 21

Installation of Thermocouples 21

Effect of Shroud and Flowmeter on ReactionClutch Plate Temperature Measurements .... 26

n

Page

Effect of Circumferential Location ofThermocouples on Reaction Clutch PlateTemperature Measurements 26

Effect of Axial Location of Thermocoupleson Reaction Clutch Plate TemperatureMeasurements 30

Effect of Radial Location of Thermocoupleson Reaction Clutch Plate TemperatureMeasurements 34

Effect of Circumferential Location ofThermocouples on Oil Exit TemperatureMeasurements 34

Effect of Axial Location of Thermocoupleson Oil Exit Temperature Measurements .... 35

Effect of Radial Location of Thermocoupleson Oil Exit Temperature Measurements .... 36

Errors in Temperature Measurements 37

V. TESTING TO EXPERIMENTALLY DETERMINE CLUTCH HEATTRANSFER COEFFICIENTS 39

Test Setup and Procedure 39

Clutch Oil Flow Rate 44

Reaction Clutch Plate Temperatures 69

Clutch Heat Transfer Coefficient 75

VI. PREDICTED REACTION CLUTCH PLATE TEMPERATURESDURING "INCHING" USING TRANSIENT CLUTCH HEATTRANSFER MODEL 88

VII. CONCLUSIONS 100

VIII. RECOMMENDATIONS 102

LIST OF REFERENCES 103

NOMENCLATURE 104

APPENDIX A 105

111

LIST OF FIGURES

Figure Page

1 Cross Section of Shaft Assembly 4

2 Schematic of Reaction and FrictionClutch Plates 7

3 Oil Flow Rate Through Open Clutch ]g

4 Oil Flow Rate Through Closed Clutch .... 19

5 Thermocouple Placement for ReactionClutch Plate Temperature Measurement ... 22

6 Thermocouple Placement Around ReactionClutch Plate Circumference 28

7 Circumferential Reaction Clutch PlateTemperature Distribution 29

8 Axial Reaction Clutch Plate TemperatureDistribution 31

9 Axial Reaction Clutch Plate TemperatureDistribution 33

10 (a-h) Average Steady State Flow Rate(Engaged Clutch) 45

11 (a-e) Oil Flow Rate Through Engaged Clutch ... 55

12 <a-e) Oil Flow Rate & Oil Exit Temperature ... 62

13 (a-e) Temperature Profiles With Step Heat Input . 70

14 (a-e) Experimental Heat Transfer Coefficients . . 80

15 (a-e) Experimental / Predicted Reaction ClutchPlate Temperatures 91

IS Predicted Heat Transfer Coefficients ... 98

IV

LIST QF PLATES

Plate Page

1 Shroud i7

2 Oil Exit Temperature Thermocouple in Hole ... 17

3 Oil Exit Temperature Thermocouple in Slot ... 24

4 Reaction Clutch Plate for TemperatureMeasurement 24

5 Thermocouple Leads in Cylinder Wall Grooves . . 25

6 Axial Hole Locations in Clutch Cylinders .... 25

7 Test Setup From Left Hand Side 40

8 Test Setup From Right Hand Side 41

9 Test Setup for Direct Oil Flow RateMeasurement 42

10 Computer and Instrumentation Cabinet 43

11 Thermocouple Leads Threaded Out of Clutch ... 73

12 Thermocouple Leads Threaded Through Shroud ... 73

CHAPTER I

INTRODUCTION

Powershift transmissions are used in off-road vehicles and

can be shifted "on-the-go" to different gear (speed) ratios

while transmitting full power. When a shift is initiated by

the vehicle operator, clutches in the transmission must slip

momentarily in order to provide a smooth transition from one

vehicle speed to another. This is necessary for operator

comfort as well as to minimize shock loads on the vehicle.

A powershift transmission has two directional clutches (one

for "forward" and the other for "reverse") as well as

several speed clutches. The direction a vehicle is

traveling depends upon which directional clutch is engaged.

Vehicle speed is determined by the transmission speed ratio

obtained when a given set of speed clutches are engaged.

The vehicle will change speed if a different set of speed

clutches are engaged. Since this shift to a new speed ratio

may occur at full engine power, the clutch plates will slip

for a period of time until fully engaged. Some clutch

slippage is desired to provide a smooth shift transition.

But slippage causes the clutch plate temperature to increase

rapidly since the clutch has to absorb the engine horsepower

as well as the vehicle kinetic energy. Unfortunately, the

life of the clutch plates is inversely related to the

temperature rise. In other words, the higher the

1

temperature rise, the shorter the life of the clutch plates.

This research attempts to simulate and model the heat

transfer, which occurs in the clutch when the vehicle

transmission clutch is being "inched". "Inching" means that

the vehicle is moving slowly, or is being "inched" forwards

or backwards one inch at a time. The directional clutches

are slipped to permit these slow vehicle speeds at high

engine speeds (for greater hydraulic control, engine output

torque, and vehicle maneuverability). An example of such a

vehicle is the forklift. It must be able to maneuver in

close quarters with a heavy payload.

OBJECTIVE

The objective of the research presented in this thesis

was to develop and experimentally verify a transient heat

transfer model which predicts the temperature, as a function

of time, in the reaction clutch plates of a powershift

transmission when "inching" takes place at a constant rate

of energy dissipation (heat input). In order to accomplish

this objective, it was necessary to develop a suitable

experimental test setup.

CHAPTER II

APPROACH

The approach used in this research was to first derive a

heat transfer model for the type of clutch used in

powershift transmissions. Next, an experimental test setup

was constructed. Then, the oil flow rate through the clutch

(the oil is for cooling purposes) and the reaction clutch

plate temperatures were measured for various operating

conditions and heat transfer coefficients were calculated

using the experimental data. Finally, the heat transfer

coefficients and heat input data were substituted into a

"lumped parameter" transient model. The reaction clutch

plate temperatures were then computed and compared to the

experimentally measured reaction clutch plate temperatures

in order to evaluate the accuracy of the transient model.

DEVELOPMENT OF CLUTCH HEAT TRANSFER MODEL

Description of Clutch

Figure 1 is a cross section of the clutch and shaft

assembly which includes a specially fabricated shroud to

collect oil from the clutch mounted in place. Use of a

sealed bearing and the shroud assembly isolate the oil

flowing through the forward directional clutch and direct

the oil out of the transmisssion housing to a flowmeter for

1. Clutch Shaft Assembly2. Clutch Piston3. Clutch Piston Return Spring4. Reaction Clutch Plate5. Friction Clutch Plate6. Clutch Plate Retainer7. Bearing (sealed or open)

8. Forward Gear9. Shroud (added for testing purposes)

Figure 1. Cross Section of Shaft Assembly

flow rate measurement. The clutch contains ten steel

reaction clutch plates and ten composite friction clutch

plates. A pattern of grooves in the surface of the friction

clutch plates affects the oil flow between the clutch

plates, and thus the cooling of the clutch plates. In an

open clutch (a disengaged clutch), the friction clutch

plates spin freely along with the reaction clutch plates. In

a locked up clutch, the clutch piston clamps the clutch

plates together (there is no relative velocity between

friction clutch plates and reaction clutch plates). This

clamping force is the supply oil pressure acting on the

piston area minus the return spring force. Frictlonal heat

is generated within the clutch when the clutch plates are

allowed to slip (now there is relative velocity between the

clutch plates) and when clamping force is applied to the

clutch by the clutch piston. The clutch is engaged by

moving the directional spool in the valve body from the

neutral position to the forward position. The oil pressure

behind the clutch piston (which causes the clamping force)

can be controlled by positioning the "inching" spool valve

at the proper location.

Lumped Clutch Analysis

In order to correctly develop a lumped parameter clutch

heat transfer model, the Fourier number and Biot number must

meet certain requirements.

Figure 2 is a sketch of one of the steel reaction clutch

plates and one of the composite friction clutch plates for a

typical powershift transmission clutch. Since the friction

material contains asbestos, it was assumed that the friction

material is an insulator, and that the heat entering any of

the composite clutch plates can be neglected. Two reaction

clutch plate thicknesses were used during this research,

"thin" plates measuring 0.070 in. and "thick" plates

measuring 0. 125 in.

The Fourier number ( Fo ) is the ratio of the heat

conduction rate to the rate of thermal energy storage in a

solid. For a step or constant heat input it is defined as:

Fo = a t / L a (1)

where:

a = reaction clutch plate thermal diffusivity, ft 2 /hrt = clutch slip time to steady state plate temperature, secL = reaction clutch plate half thickness, in

As will be seen later in this thesis, the reaction clutch

plate temperatures were measured using thermocouples

imbedded in the "thick" reaction plates. The clutch slip

time to reach steady state reaction plate temperature was

typically no less than 8 seconds. These conditions result

in a Fourier number of 38.

Some researchers have studied the case of heat input into

a clutch through a rotating flywheel [13. In this case, the

5-Cr- OO (T3 4->

•i- -r- (13

+J S_ r—(J <U 3T- +J </)

S_ (O c

oII

O i—i- Q.+->

u x:•i- <_>

s_ +->

liui4j.X9 l.l0 < L|3q.n[3

I/)

3CD GJ

"^ ^

ou a>o s_

B 2-S_ 3CD

c ra

o i

—

• 1

—

a.+->

u JZra uai +jOS 3

XJ=(0

(0

OS

-=

—uon

a-3CI

reaction clutch plate surface temperature is considered

equal to the reaction clutch plate centerline temperature

when the Fourier number is greater than 3. Although this is

not the same case as in this research, it does provide a

basis for comparison.

The Biot number provides a measure of the temperature drop

in the reaction clutch plate relative to the temperature

difference between the surface and the fluid. If Bi << 1,

the resistance to conduction within the reaction clutch

plate is much less than the resistance to convection across

the boundary layer 121. The Biot number ( Bi ) is defined as:

Bi = H L / k (2)

where:

H = heat transfer coefficient, btu/hr-in a -FL = reaction clutch plate half thickness, ink = reaction clutch plate thermal conductivity, btu/hr/ft/F

If the reaction plate is to be considered to have a

uniform temperature (no temperature gradient in the x

direction) during the clutch slip time, then Bi <= 0.1 . As

will be seen later in this thesis, the heat transfer

coefficient values encountered during this research were

typically around 3 to 4. These results give Biot numbers of

0.09 and 0.12 , thus use of a lumped model is justified.

This is an important point because the convective heat

transfer occurs due to the reaction clutch plate surface

temperature and not the reaction clutch plate centerline

temperature (see Figure 2). The reaction clutch plate

temperature values used in all the calculations within this

thesis are centerline temperatures.

A special computer program, using the forward difference

method, was used to calculate reaction clutch plate surface

temperatures and reaction clutch plate centerline

temperatures (see Figure 2). Experimental test data was used

to calculate the heat input into the clutch. It was assumed

that all the heat was absorbed by the reaction clutch

plates, and that no heat was absorbed by the oil flowing

through the clutch or the friction clutch plates. These

assumptions resulted in the maximum possible reaction clutch

plate temperature using the given heat input. The difference

obtained between the surface temperature and the centerline

temperature was no greater than 20 F during the temperature

transient.

Formulation of Instantaneous Clutch Heat Transfer Model

An instantaneous heat balance around the clutch, assuming

a lumped parameter model, gives the equation:

m CCp(Tout) Tout - Cp(T,„) T, M ] =

HAK(Tp L(, TE -TM6 « M ) (3)

where

:

A = total reaction clutch plate surface area, in 2

Cp(T) = specific heat of oil at temperature T, btu/lb/FGPM = volumetric oil flow rate through clutch, gal/min

H = heat transfer coefficient, btu/hr-in 2 -FK = conversion factor, 60

m = GPM * RHO(T) * 231 / 1728= mass oil flow rate through clutch, lb/min

RHO(T) density of oil at temperature T, lb/ft 3

Tim = temperature of oil entering clutch, F

T0U T = temperature of oil exiting clutch, F •

Tmeam = «5 (Tin + Tout)= arithmetic mean oil temperature, F

Tplatb = reaction clutch plate temperature, F

Substituting for Tmean and solving for the heat transfer

coefficient H results in Equation 4 below:

H = 8. 0208 *

GPM CRHO(Tout) Cp(Tout) Tout - RH0(T, M ) C P (T IM ) T, M ]

(4)A C Tp latb ~ .5 (Tout * Tim) ]

It should be noted that H is actually an average heat

transfer coefficient for the entire clutch. All the

temperature terms in Equation 4 are experimental data points

taken at specific points in time. The oil flow rate, oil

density and oil specific heat are calculated from other

instantaneous measurement values. These "instantaneous"

terms were used to calculate experimental values for the

heat transfer coefficient H.

10

CHAPTER III

TEST EQUIPMENT

Transmission

A Funk 2133 series powershift transmission was used in

this research. It is a 2000 series "short drop" transmission

with three speeds in both forward and reverse. The forward

directional clutch was used for all the tests conducted

during this research. The friction clutch plates used

during this research had asbestos friction material with

grooves in the friction material to allow flow of oil for

cooling and lubricating purposes. A stall bar was connected

to the transmission output shaft to prevent the reaction

clutch plates of the forward directional clutch from

turning. This was necessary since thermocouples were

mounted in some of the reaction clutch plates.

Engine

The engine used to supply power to the transmission was a

Caterpillar model 3204 DI-T. This 4 cylinder turbocharged

dlesel engine has a maximum horsepower of approximately 120

HP. The high idle speed was set at 2650 RPM.

Instrumentation

The following engine and transmission functions were

monitored:

11

1) Engine speed: Airpax magnetic pickup, Hoffer ACC-7Bsignal conditioner

2) Transmission input gear speed: Airpax magneticpickup, Daytronics model 9141 horsepower module, 0-3000RPM, 0-5 VDC

3) Transmission output torque: Sensotec model 41/572-05load cell, Daytronics model 9170 strain gage conditioner0-5000 FT-LB, 0-5 VDC, 2 HZ low pass filter

4) Forward directional clutch oil pressure: Pace Wianckomodel P7D-10PSID-7S5 transducer, Pace Wiancko model CD10carrier demodulator, 0-300 PSI, 0-5 VDC

5) Lube in oil pressure: Sensotec model A 10/1036-17transducer, 0-100 PSI, 0-5 VDC

6) Pump oil flow rate: Potter model 435 turbine flowmeter,Hoffer ACC-7B signal conditioner

7) Lube in oil flow rate: Potter model 429 turbineflowmeter, Hoffer ACC-7B signal conditioner

8) Forward directional clutch oil flow rate: Hoffer modelH01/2X1/4-. 1-4. 5-B-1MC3P-MS turbine flowmeter, HofferACC-27 modulated carrier conditioner/converter,Daytronics model 840 frequency to voltage converter,0-1500 HZ, 0-5 VDC

9) Lube in oil temperature: type T thermocouple,Transmation model 3610T transmitter, 0-250 F, 0-5 VDC

10) Forward directional clutch flowmeter temperature:type K thermocouple, Transmation model 3610T transmitter0-500 F, 0-5 VDC

11) Clutch reaction plate temperatures (8 locations):type K thermocouples, Transmation model 3S10T isolatedtransmitters 0-1500 F, 0-5 VDC

Data Acquisition System and Software

A Zenith 151 PC with one hard disk drive and one floppy

disk drive was used for data acquisition and analysis. The

engine and transmission instrumentation was interfaced to

12

the Zenith by a MetraByte DASH-16 expansion board and a

MetraByte CTM-05 expansion board. The DASH-16 is a multi-

function high speed analog/digital I/O expansion board. It

was used to sample 15 conditioned 0-5 VDC signals at an

A/D clock frequency of 150 HZ (one scan through the 15

inputs every 0.1 seconds). The CTM-05 is a multi-function

counter-timer and digital I/O expansion board. It was used

to measure engine speed and flowmeter frequencies by

counting the signal pulses over a period of time.

The software developed for this research permitted

monitoring engine/transmission functions, acquiring data and

analyzing data. The programming was done in Microsoft GW-

BASIC, and followed the MetraByte DASH-16 and CTM-05

programming manuals.

13

CHAPTER IV

PRELIMINARY TESTING

Purpose of Preliminary Testing

As previously stated, the objective of this research was

to develop a transient heat transfer model for the clutch of

a powershift transmission. This model requires using an

average heat transfer coefficient H as defined by Equation

4. According to Equation 4, H then is a function of the oil

flow rate through the clutch, reaction plate temperatures,

specific heat of the oil, density of the oil and clutch

plate surface area. Thus the purpose of the preliminary

testing was to determine oil flow rates through the clutch

as well as to determine temperature variations within the

clutch for different engine and transmission operating

conditions. These tests were necessary in order to better

understand how the clutch behaves, and also to discover any

complications affecting a measurement of the variables

needed for calculation of the heat transfer coefficient H.

Measurement of Oil Flow Rate

Direct Method

The oil flow rate through the forward directional

clutch was first determined by direct measurement for

various operating conditions. These conditions are listed

14

below.

1

)

Engine speed

2) Friction clutch plate speed

3) Initial stackup clearance between all of the clutchplates

4) Pressure behind clutch piston (open and closedclutches)

5) Temperature of oil entering clutch

6) Temperature of reaction clutch plates

The temperature of the oil entering the clutch was held

between 170 F to 180 F during all tests within this

research. Figure 3 shows the oil flow rate through an open

(zero clutch piston pressure) clutch. The transmission

output shaft was locked up by using a stall bar to prevent

the transmision cylinder gears from turning. Thus the

reaction clutch plates were stationary and only the

friction plates were rotating.

Figure 3 shows the total oil flow possible through the

open clutch and was obtained using a sealed bearing

installed to prevent oil, from the clutch, from flowing

through the bearing (see Figure 1). Thus all oil exiting

the four lubricant orifices in the clutch shaft must pass

through the clutch. The oil flow was collected by

installing a special shroud (see Plate 1) around the

clutch cylinder. A 1" I. D. hose connected the shroud to

an electric pump which evacuated the oil from the shroud

15

0082

o ca3 z

« < X

C22

OB

83

OSXUJ03

• * X asxU-l

OB

C3ItJ

UJQ.a

UJa.a

z« 4 X _j

IX

in

U

toIf]

to

« < X 09

mIT)

aXj;XUJ

UJ "

C_)

zXasXUJ

• 4 X 3a _lCJ

—JIX

a.

asCJ

1 1 h —1

—

« <

r

X

«4 X

«

h

1-o1-

•

X

• « X

«

1

X1—•J-)

<

-i

x -

»—

009Z

'00t?Z.

00Z2

"' 000£

009T

00sr,

—

CJ~ —c_

—0£ _i

00H '— UJ

a ZUJ UJUJ

•'

• 006F ~ o

UJ C3.— __j

<X a•• 200r _J or.

J_t——

c UJ" 008 t— .—~

cc1 OS

CJ:=

• 00921a

o_j

•—

i

Ll_

h-CJ _Ji—

,

1—

1

"'00fr ac C3

002infO*

.-•')

UJ

U

(WdDj 3iey flou iro naima

16

Plate 1. Shroud

Plate 2. Oil Exit Temperature Thermocouple

in Hole17

and pumped it into a container. The time and volume of

oil to fill the container were measured in order to

calculate the oil flow rate through the clutch. As

expected, the clutch oil flow rate increased with

increasing friction clutch plate speed.

The two lower curves in Figure 3 show the effect that

clutch plate stack-up clearance has upon oil flow rate.

Note that these two curves are for clutch shafts using an

open bearing. This was done to maintain the transmission

as designed (the transmission does not normally use any

sealed bearings).

The oil flow rate measurements made by the direct method

are compared to the oil flow rate measurements obtained

using the turbine flowmeter in the next two sections of

this thesis. This was done to verify the accuracy of both

methods of oil flow rate measurement.

Turbine Flowmeter

A turbine flowmeter was next installed in the shroud

oil exit line and the flow rate test to determine the

total flow possible through the clutch was repeated.

These results are also plotted in Figure 3.

Figure 4 shows the oil flow rate through the friction

clutch plate grooves in a locked up clutch. The oil flow

rate through the clutch is proportional to engine speed

18

H h

T 328T

33/

r

33° r

335!

20H

astr

n

03 rr atuCO

f 033 r

336 _ ^

UJ

328

00 J, CO

1—« _j

333 rz~~-

t:

33?

00 fN CO tO CN •:-

iwd3j 3i.yy ttcnj ire Hcum;

19

because the oil pump is driven by the engine. The

transmission output shaft is locked up as in all testing

but now the torque converter is stalled. None of the

clutch plates are slipping or rotating, therefore the only

flow possible is through the grooves in the friction

clutch plates. Hydraulic pressure filling the cavity

inside the clutch forces the oil to flow through these

clutch plate grooves. These results show the amount of

oil flow through the friction clutch plate grooves alone.

Results discussed later in the thesis will show the total

amount of oil flow through all of the clutch plates.

Combining these two results will show the amount of oil

flow over the reaction clutch plate surfaces versus the

amount of oil flow through the friction clutch plate

grooves.

Summary of Preliminary Oil Flow Rate Testing

No significant change in oil flow rate was detected

between the direct method of flow rate measurement and the

turbine flowmeter method of flow rate measurement, even

though addition of the flowmeter increased the resistance

to' flow in the oil exit line from the clutch. The oil

flow rates shown in Figure 3 were measured both directly

and by the turbine flowmeter, both methods giving

essentially the same results.

20

Measurement of Oil and Reaction Clutch Plate Temperaturmperatures

Installation of Thermocouples

The temperature of the steel reaction clutch plates and

the temperature of the oil exiting the clutch were

measured using type "K" chromel-alumel thermocouple wires

inserted into "thick" and "thin" reaction plates,

respectively (see Appendix A for all material properties

and dimensional specifications). Reaction clutch plate

temperatures were obtained by drilling a hole through the

circumference of the plate to the center line of the plate

(see Figure 5). The thermocouple wires were first spot

welded together and then held in place within the drilled

hole by ceramic cement. The glass braid thermocouple wire

insulation was previously treated with epoxy to prevent

the insulation ends from fraying while being handled. The

insulation of the alumel lead was trimmed back to allow

insertion of the complete chromel lead (wire plus

insulation) and the alumel lead (wire without insulation)

into the drilled hole. This was done to electrically

isolate the thermocouple leads from each other, even

though the thermocouple transmitters are already isolated

units. The thermocouple leads were threaded along the

clutch cylinder and out the shroud as shown in Plate 5.

Two spline teeth were ground off the reaction plates at

each of the six thermocouple positions to compensate for

21

-&-=-

TOP VIEW

Thermocouple Wire

Figure 5. Thermocouple Placement for ReactionClutch Plate Temperature Measurement

22

the flow restriction caused by the thermocouple wires.

The temperature of the oil exiting the clutch was

measured near the outer edge of the reaction clutch plate.

A hole was drilled through the circumference of the plate

towards the center of the plate. The thermocouple was

again inserted into the drilled hole, but first a hole was

drilled through the reaction clutch plate perpendicular to

the plate surface (see Plate 2). One side of the hole was

beveled to promote oil flow through the hole in the plate.

This hole is located near the outer edge of the reaction

plate. The thermocouple junction is located at the center

of the hole, but one of the thermocouple wires extends

past the hole further into the plate. This serves to

support the thermocouple wires and also to isolate the

thermocouple junction at the center of the drilled hole

and away from any plate temperature effects. A second

method of oil temperature measurement was also attempted

by cutting a recess in the reaction clutch plate outer

circumference. The thermocouple junction was then located

within this recess (see Plate 3).

The drilled hole method of oil exit temperature

measurement is the preferred method of temperature

measurement (for reasons discussed later) and is therefore

used for all such measurements within this research.

23

Plate 3. Oil Exit Temperature Thermocouplein Slot

Plate 4. Reaction Clutch Plate for Temperature Measurement24

Plate 5. Thermocouple Leads in Cylinder Wall Grooves

Plate 6. Axial Hole Locations in Clutch Cylinders25

Effect of Shroud and Flowmeter on Reaction Clutch PlateTemperature Measurements

The shroud was placed around the clutch during some of

the temperature tests to collect the oil for flow rate

measurement. Insertion of the turbine flowmeter into the

system causes a restriction in the oil exit line, as

mentioned previously. It was expected that this

restriction would reduce the oil flow rate through the

clutch, therefore causing higher reaction clutch plate

temperatures. In order to determine whether the oil flow

restriction was a significant factor, the flowmeter was

replaced by a pump connected to the shroud to evacuate the

oil from the shroud (this is the direct method of oil flow

rate measurement discussed earlier). No significant

reaction clutch plate temperature differences were noticed

between these two tests, therefore it was concluded that

the reaction clutch plate temperatures are not adversely

affected by the insertion of the flowmeter into the oil

exit line.

Effect of Circumferential Location of Thermocouples onReaction Clutch Plate Temperature Measurements

The purpose of this test was to determine if the

reaction clutch plate temperature varied in the

circumferential direction under constant clutch slip

conditions. A reaction clutch plate with six thermocouple

26

wires, as shown in Figure 6 and Plate 4, was placed in the

center (reaction clutch plate 5) of the forward

directional clutch pack. The clutch normally contains 10

reaction plates and 10 friction plates, with plate 5

located at the center of the clutch pack. Figure 7 shows

typical reaction clutch plate temperature rises measured

around the plate circumference. Temperature rise is the

increase in reaction clutch plate temperature caused by a

heat input at the plate surface. Mathematically, the

temperature rise is the final reaction clutch plate

temperature at clutch slip time t minus the initial

reaction clutch plate temperature at time zero. The

temperature rise is used to prevent the temperature of the

oil entering the clutch (which can fluctuate during the

tests) from affecting the final reaction clutch plate

temperature results. The lower temperature rises shown in

Figure 7 correspond to those thermocouples near an oil

exit hole in the clutch cylinder. Similarly, the higher

temperature rises correspond to those thermocouple

locations further from an oil exit hole. There are 6 oil

exit holes drilled through the clutch cylinder wall (1

every 60 degrees), and the holes have three different

axial locations (see Plate 6). These holes permit the oil

to exit the clutch cylinder and return to the transmission

sump (or to be collected by the shroud, as was the case

for most of the tests during this research). Thus the

27

ThermocouplePosition

6

ThermocouplePosition

5

ThermocouplePosition

1

ThermocouplePosition

4

ThermocouplePosition

ThermocoupleC. Position

Figure 6. Thermocouple Placement Around ReactionClutch Plate Circumference

28

to

a_

Uj

ou

<3'

—

j

I—zz

CD,—

,

1—CO—

1

aUJCtZ

za:

UJ

a:

0:1 _J

es to

(JJ 3Siy 'dW31 31H1J MCiniC N o r 1 G t? 3 M

UJ

-CJ

CJ

UJa:

29

variation of plate temperature rise around the plate

circumference is determined by the location of hole

placement in the clutch cylinder wall. This observation

has significant impact on where the reaction clutch plate

temperature rise measurements should be made to obtain

an average temperature rise to be used in heat transfer

coefficient calculations. The heat transfer coefficient

value could be either high or low depending upon the

location chosen. As will be seen later in this thesis, the

temperature rise used in the calculation of the average

heat transfer coefficient was the average of six

thermocouple measurements equally spaced around the

circumference of one reaction clutch plate. Plate 4 shows

the six thermocouple wires leading from this reaction

clutch plate.

Effect of Axial Location of Thermocouples on ReactionClutch Plate Temperature Measurements

The reaction clutch plate temperature rise also varies

axially through the clutch pack due to the same reasons

stated above (location of oil exit holes in clutch

cylinder). Sample results are shown in Figure 8. One

investigator C4] has shown that clutch plate spline

friction reduces the force applied to each succeding

plate, moving away from the piston. Thus reaction plate 10

(next to the retainer) should have less heat input than

30

a

ro

T 0t

CJ

ast—

UJ

UJ

2: u_

— a:

* o £F

as

u_

uj 3srd *dW3i 3idid Haima Noriayad

31

plate 1 (next to the piston). But in Figure &, reaction

plate 2 has the minimum temperature. It was concluded

that the oil flow through the clutch must be greater here

than elsewhere in order to maintain this lower plate

temperature. It was not determined whether spline friction

is a significant factor in the clutch tested.

The maximum reaction clutch plate temperature

difference can be defined as:

Tp LUTE ™ Tft v a

AT M „ X = (5)Tp V g

where

:

Tp L a

t

c = maximum measured reaction clutch platetemperature, F

Tp v o = average of the axial reaction clutch platetemperature measurements, F

Typically, the maximum clutch plate temperature

difference is 145C. Similarly, the minimum reaction plate

temperature difference, ATmin, can also be defined and

is typically 20*/. Thus the axial temperature variations

within the clutch are significant and must be considered

along with the circumferential temperature variations.

Figure 9 shows the axial plate temperature distribution

at nine reaction clutch plate positions. These positions

are the same as those in Figure 8. In order for the oil to

exit the clutch through the oil exit holes in the cylinder

32

o

21

rx.

m si .0 3(N. 1/3 rM 33Ki KI ro Kl

(jj 3sry *dW3i 3iaid H^imo Nonoy^y

Q

r—CCCCLU3_

9 o i_

CC CJ

-y-r-«^

33

wall, the oil must flow along the cylinder wall through

the slots cut in the wall (see Plate 5). Unfortunately,

the axial oil flow rate along this side of the cylinder

wall, and out the corresponding oil exit holes, was

reduced significantly because the nine thermocouple wires

restricted the oil passageway. Thus the data in Figure 9

probably contains some error, however it does have the

same trend as the results shown in Figure 8.

Reaction clutch plate 5 was selected as the "best" axial

location for the reaction clutch plate temperature rise

measurements used to calculate values for the average heat

transfer coefficient-

Effect of Radial Location of Thermocouples on ReactionClutch Plate Temperature Measurements

The reaction clutch plate temperature rise was also

expected to vary as a function of the thermocouple radial

position (that is, to vary according to how deep the hole

in the plate was drilled for the thermocouple). This

effect was not pursued in the course of this research

since the lumped model assumed requires only the average

plate temperature.

Effect of Circumferential Location of Thermocouples on OilExit Temperature Measurements

The temperature of the oil exiting the clutch also

34

varies around the reaction clutch plate circumference. The

oil exit temperature was measured using a "thin" reaction

clutch plate located at plate position 6 (plate position 1

is next to the clutch piston). It was noticed that the oil

exit temperature was equal to or greater than the plate

centerline temperature when the thermocouples were placed

directly in front of an oil exit hole, for example,

circumferential position 1. When the thermocouples were

moved to a location more distant from the oil exit holes,

such as circumferential positions 2 or 3, then the plate

temperature was greater than the oil exit temperature,

which was expected.

The reaction clutch plate used to measure the oil exit

temperature, needed to calculate the heat transfer

coefficient, was rotated so that the thermocouple was

located at circumferential position 2 (see Figure 6).

Effect of Axial Location of Thermocouples on Oil ExitTemperature Measurements

The temperature of the oil exiting the reaction clutch

plates in the axial direction is expected to be similar to

the axial clutch plate temperature variation discussed

above. This effect was not pursued in the course of this

research.

Reaction clutch plate 6 was the axial location chosen

for the oil exit temperature measurements used in the

35

average heat transfer coefficient calculation.

Effect of Radial Location of Thermocouples on Oil ExitTemperature Measurements

The preferred method of measuring the temperature of

the oil exiting the clutch is to use a thermocouple

located within a hole drilled through the plate surface,

as discussed previously (see Plate 2). This method

isolates the thermocouple junction from any outside

temperature affects. However, at the same time, it also

causes an error in the oil exit temperature measurement.

Since the hole cannot be located at the outer edge of the

plate, the true temperature of the oil exiting the clutch

cannot be measured, but rather an average of the oil

temperature on the plate surface. Some researchers have

studied how the oil flows over the surfaces of rotating

clutch plates C3J. They concluded that the oil travels

over smooth clutch plate surfaces in an outward spiral

movement. From this, it was concluded that for this

research the error in the oil exit temperature measurement

is small since the path that the oil travels over the

plate surface is long relative to the diameter of the hole

drilled through the plate surface.

On the other hand, a thermocouple located within the

recess of the reaction clutch plate, as previously

mentioned (see Plate 3) may be cooled by oil flowing along

36

the clutch cylinder wall, or by an oil flow vortex within

the recess cavity. Even so, oil exit temperature

measurements by thermocouples located within the recess of

the reaction clutch plate compared favorably to those

using a thermocouple placed in a drilled hole in the

reaction clutch plate.

The drilled hole method of oil exit temperature

measurement was the method used within this research for

all such oil exit temperature measurements.

Errors in Temperature Measurements— — — — — — — — — — — — — — —— _ _

_

__ _

The total error in these temperature measurements is not

certain. Drilling holes into the reaction clutch plates

for thermocouple installation causes errors in temperature

measurement. The drilling process creates a "high" spot

on the plate surface because the drill bit deforms the

metal around the hole. More heat is generated on the

"high" spot, thereby causing high plate temperatures

around the hole. The thermocouples are cemented into the

drilled hole by a ceramic cement. The thermal

conductivity of the cement is different than that of steel

(ceramic cement has a thermal conductivity of 3.4 compared

to a steel conductivity of 300) and therefore insulates

the thermocouple from the reaction clutch plate. This

causes a low reaction clutch plate temperature reading.

37

There are errors between different thermocouple

measurements because each thermocouple has its respective

transmitter. Although the transmitters were all

calibrated at the same points, each transmitter has a

calibration error of 1. 5 F. An attempt to verify the

accuracy of the temperature measurements and transmitters

was made by switching the thermocouple leads to different

transmitters, and also by rotating the reaction plate used

for plate temperature measurement to a different position

within the clutch cylinder. None of these changes

resulted in different temperature profiles nor affected

the temperatures reached at the plate positions by any

large degree.

Finally, there is a quantization error due to the 12

bit A/D converter within the ZENITH computer.

38

CHAPTER V

TESTING TO EXPERIMENTALLY DETERMINE CLUTCH HEAT TRANSFERCOEFFICIENTS

Test Setup and Procedure

Plates 7 and 8 show the engine/transmission test setup.

The transmission plumbing is as specified by Funk

installation drawings.

Plate 9 shows the container used to determine average

clutch flow rates by direct measurement. The oil was

evacuated from the clutch shroud using an auxiliary pump and

pumped into the container. The container oil level was

determined by reading the burette on the side of the

container. The oil level in the container was controlled by

a manual valve underneath the container which allowed

dumping the oil from the container into the transmission

sump. The sump was initially overfilled (with four gallons

of oil) so that the five gallon container could be filled

for volume measurement without emptying the sump. The

elapsed time measurements ranged from 30 to 130 seconds.

Plate 10 shows the computer and instrumentation cabinet.

Data collection was initiated at the same time the

transmission clutch was engaged by flipping a switch which

sends a 5 volt DC signal to the computer and 115 volts AC to

a solenoid. The solenoid operates the directional spool

valve in the transmission valve body to shift the

39

Plate 7. lest Setup From Left Hand Side

40

QJ-a

-a

•r-

a:

e5s-

on

CO

41

Plate 9. Test Setup for Direct Oil Flow Rate Measurement

4Z

Plate 10. Computer and Instrumentation Cabinet

43

transmission from neutral into forward.

Clutch Oil Flow Rate

Figure 10a is a summary of the average steady state clutch

oil flow rate through the forward directional clutch under

slippage at different friction clutch plate speeds. The

flow was measured directly by filling the container

described previously. The transmission "inching" valve was

first preset in order to realize a desired clutch piston

"apply" pressure. Then the valve was shifted from neutral

into forward causing the directional clutch to slip under

constant clutch piston "apply pressure". About 15 seconds

were allowed for the clutch to fully engage and the clutch

oil flow rate to stabilize. The flow was then measured over

a period of 30 - 45 seconds. The temperature of the oil

entering the clutch was maintained between 170 F and 180 F.

Comparing the difference in oil flow rates between the

engaged clutch in Figure 10a and the open (or non-engaged)

clutch in Figure 3, it can be noted that for low clutch

pressures, the oil flow rates shown in Figure 10a are

greater than the oil flow rates shown in Figure 3. The oil

flow rate through the clutch actually increases when the

clutch is engaged.

Figure 10a, which shows the steady state oil flow rate

through a clutch under slippage, can now be combined with

44

ro(XI IX i

—

II M ena. ii ii

a_ a. oii

Q-

00 r^ °*in ^*II ^ II

Q_ 1 1 Q.

T 309Z

flflfrZ

•206.

0002.

' 303 r

00S?r

209

001?

00o (X

LJr—

X>_l

a

a

UJ

UJ

IX

Q_ u_tr

306 r^~*

_j

a r_3

UJUJ UJ

000t10 <X

1—u CO1—ex v_

008 aUL_ <x

UJx: 1

—

<_> CO

CSJ 31

CD

a;UJ:>

UJ

CJ

(WdDJ 3idd MOU 110 M31013 'SAU

45

Figure 4, which shows the oil flow rate through the friction

clutch plate grooves, to determine the oil flow rate over

the surface of the reaction clutch plates. Comparison of

these two figures show that the oil flow rate through the

grooves is typically 15-20% of the total oil flow rate.

Therefore, &Q-&5'/. of the oil flows over the surface of the

clutch plates.

Figure 10a is actually a summary of Figures lOb-lOh. Upon

inspection, these figures show the individual data points

used to obtain Figure 10a. The lines through the data

points were obtained by linear regression. The lines showing

the average clutch oil flow rates in Figure 10a extend to

the maximum clutch plate speed possible for the clutch

piston pressures shown. The engine is at full throttle at

this point, so no greater friction clutch plate speeds are

possible. The clutch oil flow rate initially decreases with

increasing pressure behind the clutch piston as shown in

Figure 10a. Since the oil pump is driven by the engine, the

pump flow is proportional to engine speed. Increasing the

clutch piston pressure causes the torque converter speed

ratio to decrease. Therefore to maintain a constant friction

clutch plate speed under increasing clutch piston pressure,

the engine speed must increase. Thus in Figure 10a the

change of slope with increasing clutch piston pressure is

due to the change in pump oil flow rate.

The maximum oil flow rate through an open directional

46

S\

OL

inCM

11

a:

s e \

i1

—

a, © e

B9 ©

S ©£>

© ex

-I

0D\

i

e\

©©to

1

—

1

UiOSr>ininLUa;

-ai-•-?

U1-

3_lU

1 !

tns>i

UJfMCM

+

a<aaa

ex

u

sa_to

0092

00fr<:

0033

3332

308 r

009 r

"'03M

032r

030r

309

009

00ir

"• 303

o

U

CJ<xCJ^.UJ

UJ

a:

2^ UJa_ I-<H ce<

—

t—m

aUJ >~

UJ C3

cl- czui UJ

UJ CO

h-cc UJ_l ua. X

ccX uju >^— CL-O_J •

CJ _fl

S3*"

UJ0£3CJi—

i

u_

IWdDJ 31ti<J flOU 110 W3ini3 'DAtf

47

,0©

SiCM CM'

LOCL-

^IN a.PJ OS

H -*

IW K1DC aa3 i

<fl UJto ifl

lU p-

«

K »

i. —3 •r

ar- C75

OT r%—

*

COa. sXu ui—^ 3C_j Q-

"1

(Wdsj 3iay rtou iro wcirm *dah

48'

309c:

00frZ

30z;;

000£

02sr

009 r

00M

mz\

300t

039

009

00fr

00ZU

c_J

bCJ

UJ

<xCO

UJ

UJ

cc:

CD

X ua_ 1—

K cc— 1—

COC3UJ >—

UJ QQ_ CX00 UJ

1—

UJ mt—CX UJ_J CJ

a. Xae

X UJCJ ;>

I— <X

li

CD

in

-na.

._, cki a.

.Xu

XUJ% «3"

3 aw 1

VI tuUJ 3DD£ CC0_ •

00Za tt~si —

.

—

«

S30_ •

JZC_I II

1—

^ X_' a.u ts.

3032

'• 23t£

20£2

2033

328*

323 r

22frT

322:

339

033

32fr

302 _j

cwdsj jiyy rtou iro noima *0Atf

49

u3

UJ

(X

UJI—'X

ar. UJa_ I—QC X•~ t—

C/3

aUJ >—

UJ aQ_ Xcn UJ

t—

UJ 'ji

»—

ac UJ_j cr

i. nCE

X UJu >t— XZD

1•

CJ -a33"~

UJQ£3t3

in in

-o0.

sa Ka- Q_

OSII

4LUEC <r3 53in 1

lO UJUJ eaas m2-

r\z:o +f-w si-^ K10-

So 11

h-3 X

- 3093

03!?3

3033

3003

309 f

30ST

00 '7 I

'303f

000T

309

033

30b

003 _j

ro

UJxx

UJf—a:

a

o,

—

X UJi. i—ac X•

—

1-t/3

aUJ >—

UJ a0_ XCO UJ

HUJ W.—

X UJ_J XQ_ ex

ccX UJu >i— XX>

CJ •Si•—1

UJOSXC3

cud3] 3iay moij no uoima 'dah

50

—

•

COJ-

O) X<T a.K

•*

LUCE. *ra ea</> i

10 UJUJ sa: 00a. •

INzo *t-to s•—1 tna_ •

XCJ u1—

3 X_l a.e_> 13

0332

"20172

"0022

3002

_: "008r

009 r

00i?r

002 r

000T

008

009

00!r

'• 002 _j(_>

3CO

(J

aUJ

a:

UJ

UJ

ccac

:*o_Jii.

_J—^

o*—

1

s: UJ0_ t-QC C3Z

—

1—co

aUJ >-

UJ aa. (XCO UJ

t—UJ cot—<X UJ

1 COQ_ <x

0£3C UJC_> >i— <X

33KI-

LOIN* CS."

G3

UJ

(wjdj 3idy moij no wainij *oab

51

ma.

ro s:m n_

K.:

-(

UJac <r3 cy

W i

-O UjUJ wits T-a.

aaza +<-

in K1—i f-i

a_

=CJ u-3 n-J a.

3336

00176

(3336

0306

33ST

33sr

-30H

33zr

330f

'" 323

02&

303

a.

339 oUjUJ

CO

UJ;—

en_,a.

u

CJ

J1to

in

CJ

aUJCJac

UJ.—

X

a

aLu

to

a

CO

UJCJ3

a:ce:

UJ;>X

UJQC,

£3

(WdDJ 31dH «0"1J 110 WGimO *3AH

52

in in .•a

ineu

CO Xm 0_

asu

•*

u;x <r3 cain l

in UJUJ •—»

as C--"

a_ •

cr2.a *f-OT TJ—

1

cr0_

—

i

ECJ B

t-Z3 s;-J 0.o CSi

T03S2

00U

33^6

3003

009 [

339 r

"00!?

00ZT

333r

308

039

301?

002.

(WdDJ 3iay M01J "110 HOimO 'OAd

53

u

CJ

C3

lU

UJ

ex.

a.—

1

z: UJo_ ,—

IX CT.

<— .—

tfl

aUJ >-

u Q:j_ £Cco UJ

t~UJ 1/3

f-<x UJ_j C3

Q_ fT*

CKj; UJCJ >J— a:_D

OS

CO

clutch (previously shown by Figure 3) is 3.4 gpm at a

friction clutch plate speed of 2400 rpm. The oil flow

through an engaged clutch with 23 psi behind the clutch

piston results in over 3.7 gpm (see Figure 10a) at a clutch

plate speed of 2400 rpm. It was noticed that a small

pressure behind the clutch piston actually increased the

flow through the clutch. However, Increasing the clutch

piston pressure beyond a certain point reduced the flow as

expected. A possible explanation for this behavior is that

the open clutch restricts flow by causing the clutch plates

to flutter or vibrate, thus causing turbulent flow regimes.

Engaging the clutch by pressurizing the clutch piston

slightly then causes the flow over the plate surface to

become laminar. However, the pressure behind the piston is

not yet great enough to restrict the flow by clamping the

clutch pack very tightly.

Figures 11a - lie show the oil flow rate, as measured by

the turbine flowmeter, through the forward directional

clutch as a function of time for a step input of heat. The

clutch is slipped at a constant friction clutch plate speed

and a constant clutch piston pressure during the slip time.

Note that the oil flow rate initially increases to a maximum

value during the time period when the clutch pack is

closing. Results from the steady state oil flow rate tests

(see Figure 10a where some of the oil flow rates are greater

than those in Figure 3) indicate that this data is correct,

54

:<*. —

«

to** S a. C>(

\ a. •—as to z

f» —

*

& m 1

* *ra

* » UJ s.

* U3•-

*J» to ®> a '.o

Ul Ul s>

\ Ui X. toa. a, Oi" • VI

• fr u

La u

Kr- i- BX S •

*. * -J _j fll

:

a. u c»

**

';,

'••;.

iV•

Xu

'

..*

v"* *

:S-

A

1 1 1 1 1

—

—

i

1 1 »— ———(-

sir

si

n

3!

\r -

r j

r% », "?. «; '°. C*. _ <5J:m CM CM* (VI CM* r^i O!' CM

h-=>_JuGUJugCDz'^J

XC3

.

—

3CJ oUJ QCcn X*— f—

Lu UJ21 H1-™* XJ- •X

a_ ^-^ o_i _Jin u_

X _Jo •—

»

t- a;d—I •

c_> c•—

•"•

UJX3CJ

(Wd3) 31tiM MOIJ no Hoirm

55

<

J'

DL •—

'C **• 2.K» •-*

ra 1

c^ <K<=- T*

—

i

W sK nj :» r-

t/-. <Ba tfl

bj IU aaUJ K 05a. a. «r10

s Iu. or- .— ccc 3 •-J -J <s£. o CM

J

J

/

rs »« A «r Kl CV ^ ca(N* CM* CM* N (NT IV N* IM

0\ CO, fN 'JD

(WdDJ JltiH MQ1J HO M31H13

56

U

2!

0!

1? -

3-J<_>

QLUatx'-3

2.UJ

£CJ

^* 3•_) C3UJ 01to 2'

—

i—

UJ UJ

c 1-— (Xi- Q-:

a. **—

-i o_j _JOT u.

T*1

<_) t—

i

UJOS

t3

\

$

A

wt: .u rsi

a. *—

as ro z-« —

^

CO i

jr, 1 C£•* 31—

«

UJ S,BE =Z

I J3 t-'/J

a 0)Uj 111 r-3

uj 'X CM0. a. IXin

X u

U.i L.)

r- I~ c<x r: •»

s

Et

r r

01

» «-

oh-ZJ_JCJ

aUJcsacta=UJ

(^>• 3c_> OLU OSOO Zlw» l-

UJ LUs: J—*—

*

>-.

t— >il

Q_ ^—

i

o-J _Ju-. u.

r _l_ -^

fS 'C io *»-. r-. 1*4 _ taOM- CM* pir Cv c-T CM CM (^

UJOSJZ)

[UdD) Jiyy rtoid iro Hoimo

57

t

.*

'I

i

*-»

m11 o. cma- —X. —

*

zUl -^

>a 1

(M 1 Qt«r 3^—% bJ •n.

K ^3a r> 1—

in «Da toUi UJ COUJ ac ina. 0. o>UI

X aw CJ<— t- cX 3 9_! -J <3a_ o UI

>

£1

31

sr

fr -

o

CJ

aUJtS<x032UJ

cu

.— znu aUJ acen

-T-

IN(V.' CM CM Cm cm 3*

—

.

'XI-- «a_ -*

x: _J

r- O

'-JJ

=3

(WdOJ 3IHH M01J 110 MOiniO

58

V

/

msc a. CN1

0. —at .-73 z

in —•*

SI i

•n a ccaa X—% It; >.

* 31 Z3 »-

to OBQ </>

U» Ui aUj OS Kl.' a. Oltn

X It

tu o1- e— ca; 3 *_l _j o»0_ o at

V

>

f\ <0. «, «! K». CSI

cm" f« ex CM CM CM— OB ej as /% to{M CM «* -<* -? -V

Et

2!

[I

V -

or-:d_JuaUJoa:OzUJ

~a— Z3

'_) alu Xto -—i*— KUJ LUs: I——i <Xh- X

c~

o

u

UJ

c?

CWdD) 3itfcJ sou no M3imo

59

and not caused by an error in the flowmeter response of the

test setup. The flowmeter itself is not in error, but rather

the time required for the flowmeter to detect a transient

within the shroud may cause a response error. The flowmeter

is about two feet down stream from the shroud. The fluid

boundary layer prevents physical contact of the plate

surfaces during this time, and even seems to augment the

flow. As mentioned above, one possible explanation for this

change in flow may be a transition from turbulent to laminar

flow across the plate surfaces. Figure 11a shows this

phenomena in the greatest detail because the clutch engaged

more slowly here, because of lower clutch piston pressure

than in Figures lib - lie.

Another possible explanation is that this momentary flow

rate increase, occuring when the clutch piston is engaged,

is the result of excess oil being squeezed from between the

clutch plates and from within the cavity inside the clutch

plates, thereby reducing the volume within the clutch

cylinder < see Figure 1). The sealed bearing prevents any

oil flow path out of the clutch except through the clutch

plates. With only about 0. 100 inches of total clutch plate

stackup clearance in the clutch (or about 0.005 inches

between each clutch plate), the decrease in clutch volume

occuring when the clutch is engaged is insignificant

(consider the flow increase versus clutch engagement time

involved in Figure 11a).

60

At some finite clutch pressure, as shown in Figure 11a

(also shown in Figures lib- lie), the oil flow rate rapidly

decreases to a minimum value. The clutch piston pressure at

which this oil flow rate decrease occurs is not known.

However, the clutch piston pressure has increased to such an

extent that the reaction clutch plate and friction clutch

plate surfaces finally do contact, resulting in frictional

heating of the reaction clutch plate. Figures 12a - 12e

show the oil exit temperature and oil flow rate as functions

of time. Comparing the oil exit temperature against the oil

flow rate determines the point in time at which heat was

input into the reaction clutch plates. The oil flow rate

then increases, and in Figures lid - lie, the flow rate

reaches another local maximum value, after which the flow

rate decreases. This flow increase is due to factors which

shall be discussed in the paragraphs which follow.

The oil flowing through the clutch turbine flowmeter,

located downstream from the clutch, contains a considerable

amount of entrained air, even when the clutch is disengaged.

The air, caused by turbulence within the clutch, is mixed

into the oil as the oil flows between the clutch plates.

This air causes the turbine flowmeter to read high. An

effort was made to estimate this error by filling a beaker

with oil that had exited the flowmeter. At low engine

speeds with the transmission in neutral, the oil contained

about 2% air. This percentage was determined by allowing

61

(wjdj 3iay moij iro uoimo

toC-J* ox-

s» en

J. *<X

J V(V,

k

—

h

—

H

3*

fl-

oe

Q

a.

£

Uia.

10CM

LaX.

UJat

<_)

I-=>

o

i

3£

to

t-a:

U>a. ujx »-Ui «

~* aX. _lUJ u.

o o• x

CI

zr

rr

3r

6QC

— i—

UJ Lu

9 E

)—

—J

XUJ

a

UJ>—

\\

f

m IS SI SI mm u: 9 UJ 51 LO ca nar K> m W C^> —

'

—

•

i/j

CM

UJ

3CJ

(J) 3aniua3dW3i irx3 iro

62

va<jd] 3idH MQirf no uoimo

\r> «r !•*« CM ~, S>cn- CM CM CM" CN CM

i*— ) t JN^—1 < « *— t

—

1- I——

i

1 \ >

1 ^ Cina. M

• „ *X a. *•ii 1

J V£ X *

taCM

1

KV

U

UJ

=5

1

>-

OBas.

U»0. UJ

ata 3C W-

UJ <x

1 > Wa.

-» o•* * X X 1 X. _>

»* *x

UJt- 1-

3 e9

UJ U.

-J —1 .

f x*—JC

—Je* o o

m xe x

• ">I *x „

"

m x

f <I X *

X _

4, „** *>x

..

i -!?V *>v

*... 1'

)

* x **1 1 1 1

5-

-i < 1

El

l\

n

•• ar

33 ea CO a caw s w 03 U)m K> CM CM •-•

131/5

UJocZ3

^-— —o <xUJ us0) UJ

(. 2Z

9 S_1CO

5 £

CJ

UJ LU

XUJ

o"<3

UJt—<xa;

:*a

uj aaniuyjdwji irxa ~iro

UJt£—>*

CD>—

•

u.

63

i«d3) 3iaa mou iro woimo

r £T

ZF

ca m a ca en BQ« in 10 ca LO ca ca<* Kl KI N cn — —

i

LO

UJ 3ynidy3dW3L l r X3 110

64

[ ?

3 z:

LJc=:

Z3^* h-u or.

UJ a:to in*"*

0.-i_

UJ UJc f—>-—

1

t- 1

—

1—

1

Q_ X—

i

UJ—

i

to —1•—

1

£ oUi— <*s

LuO Ha:OS

:s

o_jU-

oCN

Uj

twdsj 3iuy «oiJ iro Mjinio

CM" CM* CM* —"

1 1-

~~v~—7$—i—i—.—

*

1 —

h

1 * XB ' ^ x

.1

itX

.!* ,"stoa. t-M

• sx x Q- *—

V 'X v CE — z Lu

/ xx </5 —

•

K£ x r; en 1 ZD% 8V <* U (j£ 1—

% X * s OC

g^x

UJ v. oc -

e6

tx 3 Uj

\xx u 3 r- a. UJ

x* to2: 1—

a;

a O v X UJ uj sa t- ae

I r~ 3te

X'—i a

i

x u X _iX% UJ o UJ u.l- c

x^ 5x _ a-

3 *_i enCj a Q o

A x**X «, o XX .

\. Xx «.

* ?» *x

xx

«. *x» X _

I v**s

£ *x• X

< * X

\ \•-

\ 2*.

x>t Ke X .°* 3e X'•-. *

X " . * 11 H 1

X e1

i1 1 (

-:r

!

:

ar

S r-

UJOS

^~-I—u ex.

UJ a:UJ UJ'—

'

0.s:

UJ UJi- r—1—

1

1— i—.—

i

a. X*"" UJ. j

to•—

1

T" oCJ1— •a

1 UJ'—

I

j—

CXa:

3CD_JU-

Si

a

aCN

UJDC

[JJ 3yniUd3dW3l 11X3 ~1IG

65

(Wd'oj 3ia^ ftou iro uoirm

cx-tocx- c^"

(N

11 ' a 1 1— 1

—

1 1 5»——(- H 1

1 >--

I*s (O

s t, s a_ (X9. a. *—

J ©

%.*as en 2 UJ

|SJ

1/3

1 3% z.* 1/] u as t-1 I*

SI x a:

1 —1 Lu v. as1 *x ex 3 UJc

X

11 3 r- a. tu% to 02 X t-a tfl Lu (X

B «* Lu Ul IS 1— Ql*• Lui as to1

X

a. Q_ O) h i% in —. a

fi X U X _Je

\,xUJ u UJ u_

f^ t- r- cX * cc _, • -J -J ..

%x*

_J _j oo •—• —

<

f

X. CJ cs CD a

e x

1x ^

l

*x

XX

x*x_e X .,

:

o

i1"* X

»>

-

a X.

1 "i . T

'>

VV

%X "

>°e

.<

X eX e_

X \. 1X

1 1 1 H —11 1- 1

£1

I'.

rr

m

/ s:

3 l-J

'•k

UJsxzz

LUCO UJ'

' Q_

UJ UJ

1—

1

1— t—^~l

Q_ X_J

UJ

Ul1—

I

U oh- =cJ

_j UJi—<X&£

J2O.—

.

U_

S3 <s n S33 W SJ«r Kl M

O

aCM

UJ

uj 3«nia«3dW3i irx3 no

66

the air bubbles to settle out of the oil and observing the

resulting decrease of oil level within the beaker.

Increasing the engine speed to high idle resulted in

approximately 354 air. Lightly engaging the clutch caused the

plates to be squeezed together and the plate temperature to

increase. Foam began to appear on the surface of the oil

within the beaker but the quantity of foam was difficult to

measure because it dissipated rapidly. The oil at this point

contained at least 554 air, and even some oil vapor. Tests

documented in Reference 3 indicate that up to 1454 air may be

dissolved in a typical transmission fluid. Therefore, a

"solid" layer of oil does not exist between the friction

clutch plates and reaction clutch plates, but rather the

space is filled with a mixture of oil and air [33.

During the tests which were conducted it was determined

that the measured reaction clutch plate temperature can

exceed 500 F when the clutch is slipped over a period of

several seconds. When this is the case, a considerable

amount of vapor appears in the oil stream. The oil is heated

as it flows over the reaction clutch plate surfaces and also

through the grooves in the friction clutch plates. Since

the oil gives off increasing amounts of vapor with

increasing temperature, two-phase flow can become

significant at these higher clutch plate temperatures. And,

since the turbine flowmeter used was calibrated for liquid

only, it is likely that two-phase flow accounts for some of

67

the increase in oil flow rate shown in Figures 11a - lie and

Figures 12a -12e.

The oil flow rate shown in Figure 12e (also shown in

Figures 12a - 12d) increases to a local maximum point, after

which the oil flow rate decreases. At this local maximum

point, the oil/air/vapor mixture is stabilized in quality,

so the oil flow rate as measured by the turbine flowmeter no

longer increases. This maximum flow point does not seem to

occur at any specific reaction clutch plate temperature.

After the maximum flow point is reached, the oil flow rate

then decreases, as shown in the last portion of the curve in

Figure 12e.

In summary, it is believed that the true oil flow rate

does not increase with time, but rather is either constant

or else decreases with increasing reaction clutch plate

temperature. The error in oil flow rate measurement could be

significantly reduced by measuring the oil flow rate

upstream from the clutch. Relocation of the flowmeter to

allow this is possible. However, extensive modification of

the test setup will be required. Accurate oil flow rate

measurement is critical since the oil flow rate directly

affects the heat transfer coefficient calculation in

Equation 4.

68

Reaction Clutch Plate Temperatures

The temperature of the oil exiting the clutch is plotted

with the reaction clutch plate centerline temperature in

Figures 13a - 13e for a step heat input. The plate

centerline temperature lags the oil exit temperature during

the first two seconds of clutch engagement. This is because

the heat into the reaction clutch plate is first generated

at the plate surface (where the oil exit temperature

thermocouple is located) and then conducted to the center of

the plate (where the reaction clutch plate thermocouple is

located). Initially, during this step heat input, the plate

surface temperature will be greater than the plate

centerline temperature because of the thermal energy storage

due to the mass of the plate. Since the temperature of the

oil exiting the clutch is dependant upon the reaction clutch

plate surface temperature, the oil temperature measurement

has a faster response than the plate centerline temperature

measurement to any heat input. Also, the thermocouple used

for plate centerline temperature measurement is insulated

from the reaction clutch plate because it is held in place

by a ceramic cement which is less heat conductive than the

steel reaction clutch plate material.

In Figure 13e (as well as in Figures 13a - 13d) after the

first few seconds of clutch engagement, the reaction clutch

plate temperature becomes greater than the oil exit

temperature. Thus convective heat transfer from the

69

UJii

—

i

r<fl i—

s: 0- CM ocd. — CK.

OS m z U UJ(N —

t

a: a.in 1 z: c—

i

II 0£ r- UJ*x £ CX i-—

1

UJ >s Xen -3 UJ UJ

11 3 f- T_ I-to qg 3T- a:

a Ifl Lu _jUJ Li- m I— Q_UJ ft: ioa_ a. C^i r- ZCO -^ O

31 ii >; —%

UJ u UJ I—1— 1— c o<x 3 9

,i 'X

I—1 O) -^ 'Jj

J_ (-• a O XL

11

It

r r

sr

32

cXUJE0_UJ(—

toUJ

CJUJ

k 2UJ

UJ

—

.

<x_' ocCO UJ

XL £CJ UJ

£310 10

<-J

33

Csi

3LO

h

33.n

a) *dW3i 3iuid woimo Noriotoy ? iro

70

c

3

\1

UJOS—« -T)

LO i—s a. INJ xcu — 01(XL ^r z UJ UJ

m '—1 a; a.ca 1 Z3 Xc*-j ii a: 1- UJ<y X x t-—

i

UJ S auC£ ZD UJ UJ

u 3 t- a_ 1—00 03 X. Xa CO UJ _l

UJ UJ S3 t- a-UJ ct CDa. Q_ •3" i- zCO —

*

aX a< —

i

UJ t_> UJ i—i- 1- C CJx X> « _i X_j -J CD •—

«

Uj0. CJ Q> a ac

£!

Zl

rr

er

s s ca s'O ca CO SIr>~> K) OJ CM

ijj *dW3i aiaid noinio NorioH3y ? no

71

r _j

Z-J

a.

exUJXQ-UJh-co

CO_ LUCJ _JUJ •—i

CO U.'—

1

oac

UJ 0_z:p—

i

UJt— ±L

3G_ h->—

i

<X_J Qc.

in UJ0.

r. 21CJ UJt— l—Z3

i

•

CJ _oM-,

UJac3C3

UJIX

™i 3to 1—

X «_ OX a:a_ — X.<C m z UJ U-

«• —

*

K 0-ca 1 3 X10 ii K .— UJ*j- X <x t-*•% LU "^ BC

K 3 UJ Ujii ^) »- Q- r-

01 03 X SQ Ifl UJ _JLU Uj <S I— a_UJ as r^j

0. a. rs 1— zW —i o

~z_ u X <—

•

UJ CJ UJ 1—

r— h- c ;j

CC 3 9 —i CC

UJ 'dW3i 3itHd MJiHlD N0ri3d3d ? 110

72

- tr

if

E

:

ar

i—

i

in

u

UJ

0_UJ

in

^ UJCJ .—

1

UJ 1—

1

to U_•

—

ol£

U- Q_

CL

UJ

ro

OS

UJOS

•-* 3V) r~

X 0. M Xa. — asm —

»

"S, UJ UJm —

*

re a.ra 1 :s et* ii as r- u>«r X. oc i~—

i

UJ •>. XOS ^3 u UJ

U J3 1— ou 1-;r> cr? r. <x

a to UJ _iI4J UJ tsa t— a_UJ uc 03>X. a_ CD I— 2.m —

^

C3X. U X —

i

iw o UJ 1—

t- i— e '_)

oc 3 • _J K_J _J CD —

»

U;a. U a a ii

s s s ca IS a10 ca UJ ra •n ca mUJ LO «• <r n to CXI

zr

21

n

u

C_J

=3a.

ac

—

UJI—

to,— UJCJ !

UJ —

>

(/) '4-

<— o0£

L^ J—SI»—

i

UJ.-- E

IDi. 1

—

t—

,

d_l acCO UJ

a_

uj 'dW3i 3iy-id Hoimo NoriDtoy s iro

-o

LU

C3•—

i

U_

73

UJX

—

<

-3CO .—

s a_ c^ aco_ •— XX 0] 2 LU u

\n —i OS 3-a 1 3 £m ii x r— Lus 31 <X 1-—< UJ S X

ae 3 UJ UJii => t- a. t—

m C3 £ Ha tn Uj _lUJ UJ ea h" a.Uj as toH. ru en h- zm i—

i

aT\ li X i—

i

UJ (J UJ r—r— t- c UX 3 V _: a._j -J CD —i UJa. u C3 a X

X 9V iV

<s» Si Sl SJLO C3 LO 3J Lfl

Ul UO «=- «i- ro

£1

2 1

[ [

2 r

a:

UJ

en

a:

CO

UJ 1—

1

C/] Ll.

V *— aas

UJ ii_

as1—

1

UJ

E1—

0_ h-—i (X

1 OS

7 Ul UJ

CJ U_'

"3

CM

UJ *c!W3i 31dld H3ini3 N0H3ti3y 9 110

74

reaction clutch plate surface occurs because of the

temperature difference between the plate surface temperature

and the oil temperature. Because the oil carries the input

heat out of the clutch, the plate temperature was expected

to be greater than the oil temperature.

Clutch Heat Transfer Coefficient

Equation 4 was derived earlier in this thesis using the

assumption of a lumped parameter clutch model. However,

various other assumptions can be made to determine the

relative importance of the different parameters in Equation

4.

If it is assumed that T P L A

T

i is approximately equal to

Tout then Equation 4 becomes:

HI = 16.042 *

GPM CRHQ(Tout) C, (Tout) Tout - RH0(T IM ) C P (T, M ) T, „

]

(6)A ( To U T ~ Tl * )

Or, if it assumed that Tout is approximately equal to T P

L

„ T i

then Equation 4 becomes:

H2 = 16.042 GPM *

CRH0(Tp L « Te ) Cp(Tp LBTe ) TPLBTe - RH0(T IN ) Cp(T IM ) T, „

]

— . (7)A ( Tp u a t e ~ Tt m )

If Tim is approximately the same temperature as T P

L

« T (this

75

is true for an open clutch and also for slip times close to

zero in an engaging clutch) then the oil properties may be

factored out of Equation 6 to yield Equation 8 below.

16.042 GPM RHO(Tout) C P ( T u t )

H3 = (8)

The equations above assume that the reaction clutch plate

centerline temperature is equal to the reaction clutch plate

surface temperature. Heat transfer then occurs due to the

temperature difference between reaction clutch plate surface

temperature and oil fluid temperature. Since the heat

generation (proportional to torque times speed) occurs at

the plate surface, the heat will be convected away from the

plate surface by the oil. Thus it can be expected that the

reaction clutch plate temperature will be noticeably higher

than oil exit temperature. Equation 4 contains no

assumptions other than a lumped clutch model. Equations 6-8

contain different assumptions in order to determine the

effects of those assumptions by comparing various computed

heat transfer coefficients. Thus the various parameters

which affect the heat transfer coefficient may be examined

more closely.

Heat transfer coefficients for the clutch were calculated

using Equation 4 and Equations 6 - 8. These equations used

experimentally measured values of clutch oil flow rate, oil

inlet and outlet temperatures and reaction clutch plate

76

temperatures.

As discussed previously, the reaction clutch plate

temperature used for the calculation was measured using a

"thick" plate and the axial plate location chosen was at the

center of the clutch pack (reaction clutch plate 5). The

plate temperature was measured using six thermocouples

inserted into the circumference of the plate (see Plate 4).

The plate temperature value used in the heat transfer

calculation was the average of these six plate temperatures.

The temperature of the oil exiting the clutch was measured

using a "thin" reaction clutch plate located at plate

position 6 (plate position 1 is next to the clutch piston).

This plate was rotated so that the thermocouple was at

circumferential position 2. The drilled hole method of

oil exit temperature measurement was the method used for all

such oil exit temperature measurements.

The thermocouple wires were threaded out of the clutch

(see Plate 11), through the shroud (see Plate 12) and out of

the transmission. The sealed bearing was installed, and then

the shroud, discussed previously, was placed around the

clutch cylinder to collect the oil flowing through the

clutch. A turbine flowmeter was placed in the shroud oil

exit line to measure clutch oil flow rate. Figure 11 shows

how the oil flow rate changes as the clutch pack closes and

then engages. A step change in heat input into the clutch

plates begins upon clutch engagement (the actual heat input

77

Plate 11. Thermocouple Leads Threaded Out of Clutch

Plate 12. Thermocouple Leads Threaded Through Shroud

78

is not a perfect step change since the clutch piston is

pressurized over a finite interval of time).

Calculated values for three of the heat transfer

coefficients defined <H , H2, and H3) are shown as functions

of time in Figures 14a - 14e. These coefficients were

calculated using Equations 4, 7 and 8, respectively. The

heat transfer coefficient HI is not shown in these figures

because the results for HI are nearly identical to those for

H2. Equation 4 is the basic heat transfer coefficient

equation, and Equations 6 - 8 each contain assumptions that

simplify the heat transfer coefficient expression. This was

done to determine which of the parameters dominate or are

temperature sensitive in Equation 4. Note that in Figure

14a (as well as in Figures 14b - 14e) all of the heat

transfer coefficients have the same shape as the oil flow

rate through the clutch, previously shown in Figure 11a.

The parameters involving temperature in Equation 4 simply

shift the heat transfer curves up or down. Thus it can be

concluded that the oil flow rate through the clutch is the

most important single factor involved in the heat transfer

coefficient calculation. In fact, if the oil flow rate and

the initial reaction clutch plate temperature were the only

known conditions within the clutch, a computer model could

accurately predict the reaction clutch plate temperatures

(this would be the same as using H3, Equation 8, for the

heat transfer coefficient).

79

«X a. csr^ *-

an Ul z(^ —*

l/J 1

—

*

N K«r £-* Uj s-.

oc =}1 2 1-

in asa wUi U) 5BUJ 0! U)a. a. r*01

X *

W ur- »- c<x Zi_j _J r*

tu o a

Kl

5 1.

•» ?

• I

rt

3T

U

» 2UJ

tni—

UJ—io•—1

u_luUJoCJ

UJu_</}

zen

UJX

—. <x

3» •S) SJ WL <s in si \n », U5 sa w. aaoo* IV rv to CD' irt \n T t K»* HT CM P*'

XX UJ—

i

X_J —

1

to rr.

UJX Q_CJ X»— UJx>_J •

o c<?"•

UJ>*:

C3

{J-3lNI-iW/niaj 'JJ3C3 H3JSNHyi J.H3H

80

</j

X. a. CMa_ •—

K <r iK! -1

IS 1

c-m 1 ccKT X—

«

UJ •sT£ 3

1 3 fr-

-o CE)

Q UJUJ UJ SJlu oc (35

a. a. »n

X aUJ o»~ t- c<x 3 •_J _J c»

au t_) CI

cm31

:a.

in U»i CO, to. C9ID rv r\* to :o in U1

to, U). in.cm

(J-£iNI->JH/rU8J 'JJ303 M3JSNbf^l JLH3H

81

acm

vir

sr

rr

ar

fr -

en!—rz.

UJ•—

«

o

UJoooxUJU-to

>xac

«-— i—C_>

UJ i—to ex

—

UJX.

UJ3Z _J1—

»

ex1— 1-

z.X. UJ—

1

X1

1—

1

LO txUJ

T. a.t_> XI— UJ3

]

_o

X)C5

44 if

• T

4 x4 X «

4 x •

s N44

4

I',

:<

' ••

m -;

4*4 1

••

•«^- 4 y •

en i44 i «

•I/] ii cc 4 y •«c

UJr 4

44

yyy

«••

a

asr-

44

4

•••

ir; CD 4x

XX

4)

aUJ

09u. «

444

•«•

lu X 0^ 4 y •a. a. (N 4

4 \ *•

UT 4 •

UJX U

444

|

••

«1— 1— c. 4 •a; =3 V 4

4>:

X4>«

_- _i » 4 XQ_ CJI a

1

4 XX

••

4 X «4 X •4 x• X4 X4 X

••

4 X

\ Ii x

4 X* .

*4 X

•

«•

X X X 4 S4" X

X4 X

«

• « X4 X4 X« 3<

«: *?J x

••

* X4

4 >*

4) X4] X •4 * .

47 X 44)

4)

4

«4

44

444

44

X 4>

X *X *X •

x •

' •X »X •X •

44 X •4 X _

K K <4 X «

4 X^ •4 X „ •4 X •4 X . •4 X*4* X« X •

4 >4 •-,<

44> X4 4K« X

» 4 X% 4 X* 4 X

* 4 X*

J £* 4 X

14«. x

4 X* 4 X

i— 1 1

*—!

I,

4 X1 1 —1 1 1 1

l\

r r

01

tn

2.UJ

UJo

9 Q£UJu.

s^

UJ r-

b ^ x

—• cc

UJ

en

u

SJ UO 5) ^, 3) "J. S00

'

r\* (V 03 to' 1/3 in?3CM

uXUJ

UJ

cr

t j-ziNr-yH/niaj 'JJ3Cj d3JSNayi iH3w

82

4 > * T< v «4 X «4 X «

4 X *Ifl

44 V

«r. a_ CM X «

as z.

4

4

XXX

««

•-') 4 X «G3 1

44

sx

(M ii 21 4 ««#

U.

444 \ «

•

u 3 1—44

• X

*•

«UJ 03 4 X «

aUJ UJ SI

44

4

XXX

«

•UJ BE d 4 X *X. a. 0]

44 g

<n

J«

UJcCJ

u 444

«•

1- r- c 4 «X V 4

4 'x* «_j —

i

« 4 X «0- O 3 4

4XX

«»

4 >: «44 X

«4 X «4 X «4 X «4 Te «

4 «4 x" *

44 i?

«4 X *4 X «4 :; «44 \ «

«4 X «

OJ Kl 4 X *E — X 4

44

X

*x• t X

44 x* •?4 x «

4 X «4

. \: **

\ xx

* X

« X4J X

44

*«

4)•«•

•«

* J*

« \ i4 X •

4»

4

4 X

* ft »4 X •

: i .•

5 \ •4 X*

4 • X4 1 X

• 4 X* 4 X

• « X*

* : $•

•i $4 X

• « x

—

*«

4

i 1-—»-

4 ?<4 X

: I4 X

X

i 1 1 1

z\

rr

21

UJyj

CQ

UJ

u

o

—. X

a_ uj

03 siCO*

1/7,

tor-2

XUJ

<3"

LJ

u-ziNr-iiH/nigj 'jjsoo dajsNayi lhbh

83

tOn a. CMcu *—

fC at zIfl —

*

oa 1

UO 11 ocS3 z:—

*

UJ n.K .3

u 3 i—LO 33

a 'J?

UJ UJ eaUJ cc Kla. a. Ojin

sUJ o/— 1- (j

a:—J

•

0- O cj

CM

*

*x .*

X: •X <

*x . *X »

I •X «

*x*

X •*x

*

x*X

*3<

2 • *

Xo< •

ii V« X <

« X« X« X

« X< X

* **

: s\ \ \« X. <

.' X*

: x*.

. W'£ X

•h >t XX

•« $« X

« X« X< X

to 5J UJ, OB irt

<v N" CO CO' LO

£f

r r

fr —

en

u

to

UJaCJ

etc

UjU.CO2cr-

ate

r~ H-C.J

UJ ,—

CO ac*— uj

—UJ£ _i—

i

Xh- i—

a_ UJ

u-ziNr-yH/rusj* 'JJ300 ajJSNHai lhjh

UJ

UJ

a—

»

34

Equation 4, used to calculate the heat transfer

coefficient H, does not give satisfactory results during the

initial clutch slip time (the first two or three seconds)

because of temperature and oil flow rate measurement errors.

Because all of the initial temperature values (the

temperature values during the first several seconds of

clutch engagement) used in Equation 4 are nearly the same,

the overall error associated with these temperature

measurements becomes larger when they are subtracted and

divided as required by Equation 4. It may be recalled that

the thermocouple transmitters alone each have an error of

1. 5 F. Furthermore, the difference between the temperature

of the oil exiting the clutch and the reaction clutch plate

temperature ranges from only five degrees to twenty degrees.

And since the temperature of the oil entering the clutch

remains constant, this means that the difference between the

temperature of the oil entering the clutch and the

arithmetic mean oil temperature ranges from under 10 degrees

when the clutch is initially engaged, to over 200 degrees

difference at the end of the clutch engagement. Thus the

shape of the heat transfer coefficient curve during this

initial clutch slip time should be determined by Equations 6

- 8 instead of Equation 4 (see Figures 14a - 14e). However,

Equation 4 does give more accurate heat transfer coefficient

values after these first several seconds of clutch slip time

(once the temperature differences become large enough to

85

reduce the amount of error involved in the calculation).

Before testing was begun, the reaction clutch plate

temperature was expected to approach a steady state

temperature value since the heat input to the clutch

remained constant over the clutch slip time. However, the

plate temperature values in Figure 13e (and also in Figures

13a - 13d) do not reach a steady state temperature, but

rather increase at a constant rate. Therefore, the heat

transfer coefficients in Figure 14e (and also in Figures 14a

- 14d) should decrease (have a negative slope) with

increasing clutch slip time. In order for the heat

transfer coefficient to decrease, the oil flow rate through

the clutch (shown in Figure lie) should also decrease, as

discussed previously. Note, however, that in Figures 14d -

14e the heat transfer coefficients do finally decrease after

a certain maximum point is reached. This decrease occurs

when the oil exiting the clutch becomes somewhat stabilized

with regard to the amount of air entrainment and oil vapor

within the oil flow. It is believed that this negative slope

is indicative of what accurate values for the experimental

heat transfer coefficient should be. This decrease in flow

as a function of clutch slip time is shown in Figures lid

lie.

In order to improve predicted heat transfer coefficient

values, it may prove desireable to include in Equation 4

such factors as the engine speed and torque converter speed

86

ratio (or clutch plate speed), and clutch piston pressure

(or heat generation). Furthermore, the gear train

efficiency was not accounted for in the torque measurement.

An efficiency of 9&7. would likely be satisfactory. This

factor is not entirely negligible since 254 of a maximum heat

generation of 1400 btu/hr/in fl could raise the computed

plate temperature by several degrees. However, none of

these factors are directly included in the present model

(Equation 4). Also, the distance between the clutch and the

turbine flowmeter causes a time lag in the flowmeter

response.

87

CHAPTER VI

PREDICTED REACTION CLUTCH PLATE TEMPERATURES DURING"INCHING" USING TRANSIENT CLUTCH HEAT TRANSFER MODEL

The transient clutch heat transfer model used to predict

reaction clutch plate temperatures during "inching"

operation is derived below. First, assuming conservation

of energy gives:

Qoe M <t)-QcoKv<t)=Q9TORSD (t) (9)

Then substituting for QcoMv(t) and QIT0 , C g(t) gives:

Q. CM (t) - H A CT(t) - T* eAM (t)] =

C T(t + At) - T(t) ]

RHO C P A L (10)At

Finally, substituting for T* B „ * < t ) (note that this

definition assumes that the temperature of the oil exiting

the clutch is equal to the reaction clutch plate

temperature) and rearranging Equation 10 gives:

T(t-»- At) =

AtT(t) {Q". tN (t) - 0.5 H C T(t) - T, M J) (11)

RHO CP L

where:A = total reaction clutch plate surface area, in 8

CP = specific heat of steel reaction clutch plate,btu/lb/F

H = heat transfer coefficient, btu/hr-in 8 -F

83

L = reaction clutch plate half thickness, in0«««<t) = heat generated at reaction clutch plate surface

at time t, is proportional to torque times speedbtu/hr

Q'aEM<t) = heat flux per unit surface area, btu/hr/in a

QcoNv(t) = heat convected from reaction clutch platesurface at time t, btu/hr

Q«romo<t) = heat stored by reaction clutch plate at time t,btu/hr

RHO = density of steel reaction clutch plate, lb/ft a

T(t) = reaction clutch plate temperature at time t, FT(t+dt) = reaction clutch plate temperature at time

t+dt, FTim temperature of oil entering clutch, F

T« E a

n

< t ) = 0.5 [Ti„ + T(t)] = arithmetic mean oiltemperature at time t, F

At = time increment, sec

A computer program, which solves Equation 11 iteratively,

was written to calculate reaction clutch plate temperatures

using experimentally obtained heat transfer coefficient

values and heat flux values. The computer program, by the

forward difference method, uses known quantities at time t

to calculate a future reaction clutch plate temperature at

time t+dt. It was originally planned that the heat transfer

coefficients, as functions of time, would be obtained from

Equation 4. However, it was previously concluded that the

present experimental heat transfer coefficient results

(obtained through Equations 4 and 6-8) are unsatisfactory

(due to oil flow rate measurement errors). Thus the

experimentally determined heat transfer coefficients were

not used in the computer model. Rather, the heat transfer

coefficient values were assumed to be constants, chosen to

achieve the same steady state reaction clutch plate

89

temperatures as was experimentally measured. The heat flux

used came from actual experimental data, therefore is was a

function of time.

Predicted reaction clutch plate temperatures are compared

to measured reaction clutch plate temperatures in Figures

15a - 15e in order to verify the accuracy of assuming that

the heat transfer coefficients are constant. Achievement of

the same steady state reaction clutch plate temperatures

(experimental temperatures and computed temperatures)

verifies that the proper heat transfer coefficient value was

substituted into the computer model, Equation 11. The

assumed heat transfer coefficient value used is shown in

each of the figures.

The assumed heat transfer coefficient constants (shown in

Figures 15a - 15e) are 25'/. - 50% greater than the

experimental heat transfer coefficients (shown in Figures

14a - 14e). It was expected that the experimental heat

transfer coefficient values would be greater than the

assumed values because, as was previously concluded, air and

oil vapor caused inaccurate turbine flowmeter measurements,

thus causing high experimental heat transfer coefficient

values.

In Figure 15e, the computed reaction clutch plate

temperature is greater (by up to 35 degrees) than the

measured reaction clutch plate temperature during the

initial portion of the exponential temperature curve. This

90

wac a_ CMn_ — t-x. U1 3 i

CM ~

i

r^ «-n 1

— UJ—*

11 OS Z 3*£• X —i _J to~» UJ V, 1 'X UJ

0£ 3 ac > 311 3 i— x _J

W CD s _J Xa UJ _d x cUJ UJ aa <— 1—

uj X W cc 3 aa. a_ CM UJ UJm S3 JZ t—

JZ u • --

1

CJUJ u ea en —

,

t- i— c UJ acc z* (V ii a_ Uj_l _i O) X aca. o a E UJ a.

£1

21

t t

0!

I -

CO

en

UJa_

UJ

UJ—a;_j0-

X.o3CJ

U'XUJ

uj 3yniay3dW3i 3itnd Hcimo hoilohbh

aUJi—u

u UJ

t -X

UJ

XI—

C/j ft:

UJ

xUJ

u

SI SJ OB 33ea 10 a U3«r ,-o ro CM

—

H

33 S3

UjOSX:::

91

o•T

3C0_OS

ca

U

atu

CO

a.

1*1

n

UJ

in

UJ

z1

OSX=31—

CE

S3

i

N

1

y.XNXi—

UJx_iCX>_jtX1—

UJXJ_)<x>

• e Uja.mUJ

K

Xu

an

ii

S3UJx.

K

ca

r—CJ

li— <— c UJ a31 3 » a 0. UJ-J _J n ;< as.

1 8 a_ CJ a X UJ a.S

n a 1 -

13 1

'€>

1e1 I! e

!g«

1w\i\%

ll\ e\ o\ °

\l\ e

\*\ *\ f\ o\ 8

s\ %

\

1 1 1

—

a

£

\

+-

I

1 1i -t

--

Zt

r r

2r

1/3

mto EB

SI

UJ

UJ3£

X.

cc

u

u

COliJ

h-ccUSLUQ-

UJ

UJt-tx

X.

I"C_)

a;UJct:

aUJ

di—

UJ^_

U-i

x

1£

C2

92

£. a. (v

a. — LL,

OS to 3; 1

•^r »-* IN (0a 1

—

.

UJW U x. 21 3•» x. —i _) to—i Lu \ 1 X Lu

as J3 X. > ^11 3 1— X . l

CO OD "s _l Xa OT 3 a: >UJ UJ •S3 t— 1—

UJ as PJ cc u. C3a. O- rs, UJ UiCT CO s 1

—

z u —

»

uLu CJ CO as —

.

1— i— c UJ C331 ;s V li n_ UJ_J -j t--i ^ aca. o a K UJ a_

2!

[ I

11

uUJto

UJ:--"r-<X:-:

UJQ-s:UJ

cc

r

•o

uccUJas:

aUJ

UJ

UJ

en :cUJ~0-

CJ X.— UJ_r

u o

ca ca -aLO ca in1/3 \n ^r

1/5

£3

ijj 3yniay3dW3i 3itnd woimo Noricasy

93

s 0. CN0_ — 'J-

JC —

i

3E 1

W i—

.

CM CO31 1

— UjCM :l LK 21 ZJ«W r "-I

I en--i Uj •s 1 CC UJ

as 3 i; ^ Z2U =i t— X _J

CO en s _J ena co jj a: >UJ UJ a i— t—UJ :£ on X' z a0. a. en UJ UJCO 33 21 r—

x. u • —

.

uU^ u IN :n —

«

r~ i— c UJ a<I _J • M a_ UJ_j _J CD X OS0_ u C3 X. UJ a-

£1

31

r r

01

& -

£ i-

U3

=3

X

I-cx

a_

EUr-

C-J

ZoI—CJa:UJ31

r—

i

UJ

o U-i

U-l j£

co-->

N,UJs _J

•—1 s_J i—

i

CO sk:

Ujx o_CJ X.-- Uj_r_j •

u -r

5

UJ 3yflltiy3dW31 3lBld M31H10 NOriDtOM

94

ms a_ r-<

Q_ — J_OS en 3C I

m —

<

(N Jj5a I

— UJIrt ii K z 3go £ —

»

_l in—

i

UJ N, i X UJ0£ | i: > l_t

ii 3 t— r ,

l/J ca \ _J cca O 3 ec j>UJ UJ 3j i— t—LU D£ to 03 ~ aa. a. 09 UJ UJw cc i- !—

E II •—

i

uu ej LO a; -—1

i- h- c UJ a(X 3 o U o_ UJ_i _J a» X asa. CJ C3 £ UJ a_

£1

£1

tr

» -

u

to

-~

t—X!j_J

UJI—I

——zz

i

ua:

ac

• lj

CO Q_

—« x

CO

—x

UJ

C3

UJ 3iiniBi!3dW31 3itTid HOimO N0H3c!3y

95

was expected for three reasons. First, the heat transfer

model used does not allow any heat to enter the friction

plates, since the friction material is assumed to be an

insulator. Second, the thermocouple measuring the reaction

clutch plate temperature is held in place by ceramic

cement, which has a lower thermal conductivity than the

steel reaction clutch plate material. Third, the heat

transfer coefficient used in the computer model is a

constant, while the experimental heat transfer coefficient

is believed to decrease as a function of reaction clutch

plate temperature (this is the expected result if the oil

flow rate measurement errors could have been corrected).

The results shown in Figures 15a - 15e allow evaluation of

the experimental heat transfer coefficient values since the

experimental results should agree with the computer results.

Comparison between the heat transfer values used in the

computer model and the heat transfer values obtained

experimentally show the amount of error involved in the

experimental heat transfer coefficient results. The heat

transfer coefficient H (calculated using Equation 4) in

Figures 14a - 14e comes the closest to the heat transfer

coefficient values used in the computer model (after H

reaches its lowest values, several seconds after the clutch

has begun slipping). The experimental heat transfer

coefficient values would be more accurate, and would even

compare favorably to the heat transfer coefficient values

96

substituted into the computer model, if the experimental

heat transfer coefficient values did not increase with time

(caused by oil flow rate measurement errors).

The heat transfer coefficients used in the computer model

(these heat transfer coefficient values are constants) are

shown in Figure 16 for friction clutch plate speeds of 1400

rpm. These results indicate that as long as the friction

clutch plate speed remains constant, the heat transfer

coefficient is a linear function of clutch piston pressure.

The experimental reaction clutch plate temperatures lag

the predicted reaction clutch plate temperatures in Figures

15a - 15e. This error is due in part to the assumption that

no heat enters the friction clutch plates. In order to

improve the clutch heat transfer model, a second computer

program was written using the inverse heat conduction method

to calculate the actual heat input into the reaction plates.

The inverse heat conduction computer program uses the

experimental reaction clutch plate temperatures as input

data, and calculates the heat input required to achieve

those temperatures. The heat into the friction clutch

plates is equal to the total heat generated minus the heat

into the reaction plate minus the heat convected to the oil.

Thus, through a thermodynamic heat balance around the

clutch, the temperature of the friction clutch plates may be

computed. The fraction of heat input into the friction

plates will be a small percentage of the total heat

97

a.

f-

T 3^ —

39

t-

as

0»

K

33

N COto to'

P-4

co-cato

re

(j-2iNr-yM/niaj "JJ303 yjjsNtm i«3H

a.CO

z.

UJUJ

Dt/3

WUJ

u_u_UJa

J_C_>

za UJ

u_CO

Q_2CXQ_

d§aUJh-UaUJ

ea

UJQi

CD

98

generated because the asbestos friction material acts as an

insulator. This portion of the heat transfer into the

friction clutch plate is not entirely negligible CI]. This

last step concerning the inverse heat conduction model was

not completed because of the inability to adequately

determine the oil flow rate through the clutch, which

convects the heat away from the clutch.

99

CHAPTER VII

CONCLUSIONS

1

)

A test setup has been developed which can be used to

study the heat transfer characteristics of the clutches in a

powershift transmission.

2) Changing the transmission oil circuit to allow

measurement of the oil flow rate upstream from the clutch,

rather than downstream from the clutch, as in this research,

should eliminate the oil flow rate measurement errors

caused by air and vapor in the oil stream.

3) The true oil flow rate through the clutch, during

tests which simulated "inching", does not increase with

time, but rather is either constant or else decreases with

increasing plate temperature.

4) The uncertainty of the measured values of oil flow rate

through the clutch during tests simulating "inching"

prevented accurate determination of the clutch heat transfer

coefficient.

5) The oil flow rate through the clutch has a far greater

affect on the clutch heat transfer coefficient than either

clutch plate temperature or oil temperature.

6) Accurate determination of the oil flow rate through the

clutch should permit accurate calculation of the amount of

heat convected from the clutch plates, and thus accurate

calculation of clutch plate temperatures during simulated

100

"inching".

7) The average heat transfer coefficient should decrease

with increasing clutch slip time because the reaction

clutch plate temperature values increase at a constant rate

as time increases.

fl) The heat transfer coefficient is a linear function of

clutch piston pressure for constant friction clutch plate

speeds.

9) There are significant temperature variations, axially,

radially and circumferentially, within the clutch that

should be considered when measured temperatures are used in

heat transfer coefficient calculations.

101

CHAPTER VIII

RECOMMENDATIONS

1) The oil flow rate should be measured upstream from the

clutch where air in the oil is minimal, thus allowing

accurate determination of oil flow rate. The shroud can

then be eliminated as well as the flow restriction caused by

the insertion of a turbine flowmeter downstream from the

clutch. Elimination of the shroud is also desireable in that

it will facilitate installation of thermocouple leads, and

reduce any flow restriction caused by the leads.

2) The temperature variations, axially and radially,

within the clutch should be more thoroughly investigated in

order to locate temperature measurement points which, when

averaged, would give representative temperature values for

the overall clutch.

102

LIST OF REFERENCES

CI] Tataiah, K. , "An Analysis of Automatic TransmissionClutch-Plate Temperatures, " SAE paper number 72Q287

C2] Fundamentals of Heat Transfer. Incropera, F. P. andDeWitt, D. P., 1st Edition, John Wiley & Sons, Inc., 1981

C3] Schade, C. W. , "Effects of Transmission Fluid on ClutchPerformance, " SAE paper number 710734

C4] Newcomb, T. P. and Merritt, H. E. , "Effect of SplineFriction on the Torque Capacity and Interface TemperaturesReached During a Multi-Disc Clutch Engagement, " Journal ofMechanical Engineering Science vol. 4 no. 4 1962

103

NOMENCLATURE

a Reaction clutch plate thermal dlffusivity,ft a /hr

A Total reaction clutch plate surface area, in*Cp Specific heat of steel reaction clutch plate,

btu/lb/FCP (T) Specific heat of oil at temperature T, btu/lb/FGPM Volumetric oil flow rate through clutch, gal/minH Heat transfer coefficient, btu/hr-in* -Fk Reaction clutch plate thermal conductivity,

btu/hr/ft/FK Conversion factorL Reaction clutch plate half thickness, in

m Mass oil flow rate through clutch, lb/minQiM (t) Heat generated at reaction clutch plate surface

at time t, btu/hrQ'acN<t) Heat flux per unit surface area, btu/hr/in 2

QcoMv<t) Heat convected from reaction clutch platesurface at time t, btu/hr

QsTonio(t) Heat stored by reaction clutch plate at time t,

btu/hrDensity of steel reaction clutch plate, lb/ft 3

Oil density at temperature T, lb/ft 3

Time, secAverage of the axial reaction clutch platetemperature measurements, FTemperature of oil entering clutch, FTemperature of oil exiting clutch, FReaction clutch plate temperature, FArithmetic mean oil temperature, FArithmetic mean oil temperature at time t, FReaction clutch plate temperature at time t, FReaction clutch plate temperature at time t+dt, FTime increment, secMaximum reaction clutch plate temperaturedifference, F

AT« t n Minimum reaction clutch plate temperaturedifference, F

RHORHO(T)t

Ta v a

T,„To u T

Tp uriTh canT „ E , M ( t )

T(t)T(t+dt)AtAT M « x

104

APPENDIX A

MATERIAL PROPERTIES AND DIMENSIONS

Value Definition

k = 3.41 Thermal conductivity of OMEGA CC cement@ 500 F, btu-in/hr/ft a /F

k = 25 Thermal conductivity of steel, btu/hr/ft/Fk = 300 Thermal conductivity of steel, btu-in/hr/f

t

a /F

RHO = 490 Density of steel, lb/ft*RHO = 54.9 Density of oil @ 60 F, lb/ft 3

Cp = 0. 11 Specific heat of steel, btu/lb/FC P = 0.45 Specific heat of Conoco C3 oil & C, btu/lb/FCp = 0.47 Specific heat of Conoco C3 oil @ 68 F, btu/lb/FCP = 0.79 Specific heat of Conoco C3 oil @ 400 C, btu/lb/F

L = 0.035 "Thin" Reaction clutch plate half thickness, inL = 0.0625 "Thick" Reaction clutch plate half thickness, inA = 219. 5 Total reaction clutch plate surface area,

10 plates, in*

K = 60

m = GPM * RH0(T) * 231 / 1728The am = 0. 5 (Ti M Tout

)

Tnttu (t) = 0.5 [T IM + T(t) ]

OMEGA thermocouple wire, HH-K-24Borg-Warner SD 1053 clutch plate friction material

105

ACKNOWLEDGEMENTS

I would like to express my gratitude to Dr. Ralph 0.

Turnquist for serving as my major advisor during the course

of my graduate study. His guidance and assistance helped to

bring this work to a successful conclusion. I would like to

thank Dr. Nairn Azer and Dr. Mark Schrock for serving on my

graduate committee. I would also like to thank Dr. Byron

Jones for his consulting services, and Gary Thornton and

Brian Bramel for constructing the test equipment.

106

COMPUTER MODELING OF THE HEATTRANSFER IN A POWERSHIFT TRANSMISSION

CLUTCH UNDER SLIPPAGE

by

PAUL WARREN JOHNSON

B.S., Kansas State University

AN ABSTRACT OF A MASTER'S THESIS

submitted in partial fulfillment of the

requirements for the degree

MASTER OF SCIENCE

Department of Mechanical Engineering

KANSAS STATE UNIVERSITYManhattan, Kansas

1987

ABSTRACT

The objective of the research presented in this thesis was

to develop and experimentally verify a transient heat

transfer model which predicts the temperature, as a function

of time, in the reaction clutch plates of a Funk 2133 series

powershift transmission when "inching" takes place at a

constant rate of energy dissipation (heat input).

The test setup developed consists of three main

components: a transmission (the object under study), an

engine, and a data acquisition system.

Preliminary testing consisted of measuring the oil flow

rate through the clutch and measuring temperatures within

the clutch. The oil flow through the forward directional

clutch was collected by installing a special shroud around

the clutch cylinder. The oil flow rate was then measured two

different ways: either directly (by measuring time and oil

volume) or by turbine flowmeter. The temperature

distributions within the clutch were investigated and the

reaction clutch plate temperatures were found to change in

the axial, radial and circumferential directions. The

temperature of the oil exiting the clutch was also measured.

A heat transfer model was developed, and experimental

results were used to calculate the clutch heat transfer

coefficient. The heat transfer coefficient values and the

heat flux into the clutch were then used in a computer model

to predict reaction clutch plate temperatures.

Because of difficulties in measuring the oil flow rate

accurately, due to air and oil vapor within the oil, the

experimental heat transfer coefficients, and thus the

predicted reaction clutch plate temperatures, are in error.

It is recommended that the test setup be modified to

permit measurement of clutch oil flow rate upstream from the

clutch, instead of downstream as in this research. This

should be done before any further research is attempted.