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CLEARINGH OUSEAD 4515A 0or , , ,, it,,, , , 6.7000

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IT MAY BZ 2ELEASED TO THlE GENERAL PUBLIC-.,

4 DOCUMENT No D6-58362TN -

TITLE Bulk Modulus investigatibn - Hydraulic FluidStJiness - -

MODEL General

ISSENO. TO: ,,0)( 4 k/WDATVI-

Distribution of this document is unlimited; it may be release"to the general public.

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< PREPARED By'-,-,- , . ,-' '.j.. JA... .I.Iy.8 *J' C&SSan

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TABLE OF CONTENTS

Poge

I. ABSTRACT 3

I!. SUMMARY 4

III. INTRODUCTION 11

IV. DISCUSSION 12

A. Description of Test 14B. Test Procedure 21

C. Test Results 25

V1 CONCLUSIONS 82

Vi. REFERENCES 83

-APPENDIX 84-

A. Derivations & Calculations 85

B. Miscellaneous 90LIST OF ILLUSTRATIONS 113

LIST OF ACTIVE PAGES 116

REVISIONS 118

~D6-58%362TN

REV SYM WDAWNO. D-86TPAGE 2 6-70006-700

I. ABSTRACT

iIsothermal secant bulk modulus data was obtained from-simulated hydraulic systems-and

compared with referenced data ./Reference sources have beeh the only available data

from which to select bulk modulus valiues for system and component design. Thereforedefinite need existed for additional informda o design values are presently selected

arbitrarily or from experience. Often these va~ues-are r modified for -certain

system design and vary greatly with the experience of the designer. This study-was made

to compare the amount of fiuid compressibility existing within a typical airplane hydraulic

system and within a standard bench test system. Additional comparisons were made with

published reference sources.

0

REV SYM M'W A'P No. D6-58362TNPAGE

3 6-7000

~IL. S bMARY

This study vas nade to compare the amount of fluid compressibility

existing within a typical airplane hydroulic system and within astandard bench test system. Additional comparison vas made with

published reference sources. As these reference sources have been

the only available data from which to select bulk modulus (compressi-

bility factor) values for system and component design, a definite

need for additional information exists because presently these values

are often arbitrarL I--modified for system design and vary Vith the

experience of the designer.

Bulk modulus, a measure of fluid compressibility, is an important

fluid -property in the design of systems employing fluid for force

transmission and motion control. The fluid, acting 6s a spring in a

spring-mass system affects such system factors as response time, force

available from limited stroke actuators, and stability of servocontrolled

bydraulic systems.

The form of bul. modulus most commonly found in reference sources is

the isothermal secant bulk modulus. It is defined as the total change

in fluid pressure divided by the total change in fiuid volume per unit

volume under pressure at a constant temperature. It iL expressed by

the following relation:

~P

REV SYM ,; 90 D6-58362TN

PAGE 46-7000

i , i

It is defined graphicslly as the slope of the line connecting two

pressures of a pressure versus A V/V curve (Figure 1). For our

-7 J

Figure 1 Definition of Secant Bulk I-bduius

: coompufttions, one pressure was equal to zero.

tiIn this investigation tw'o laborator Systems were employed to develop

iI fluid compressibility, a simulated flight control (hydraulic) system-

aI nd a conventionel static bench system. The Pressure-Volume-Temperature

S method was used in both systems --'o obtain the bulk modulus data. Wi~h

this method a change in oil volume is measured for a given pressure change,

yielding a sta tic bulk modulus value.

The fluids used in this study w'ere M,1IL-H-5606B., WSX-6885, end Skjdrol

500A. The WSX-6885 fluid is under eonsideration for use in the Super-

sonic Transport. The MIL-11-5606B and Skydrol 500A are production fluids

in general use in military and commercial aircraft.

R EVSYM 'lA'AF A 1 4o D6-58362TN

- I5

5 6-7000

<AFor the three fluids tested, the bench values compared with the published

data within acceptable margins. Ccparisons of the .hydraulic 'system

data resulted in different trends for the three luids. With the

SMfl-H-5606B fluid, the initial values were the highest,, the four hour

* values, the lowest (Figure .2 ). For both the WSX-6885 and Skydroi 500A

fluids, the initial values were the highest, followed by the '4 hour

and 18 hour values in decreasing order (Figure 3, ). With a 100 psi

dormant period test section pressure, the bulk modulus values were

repeatable within the range of test tolerances for both WaX-6885 and:

Skydrol 500A fluids.

In order to determine if system cycling will restore the value of bulk

modulus to its initial value following dormant unpressurized periods,

I two full stroke -cycles were conducted after data was taken et four

rholrs. Followihg bulk modulus measurements, two more cycles end measure-

ments were made. In three of the four tests conducted with WSx-6885

and Skydrol 500A fluids, complete recovery from the lower four hour

values to the initial values was made following the four cycles.

The air content of the fluid and its variation with cycling was investi-

gated by the use of a Seaten Wilson "Aircmeter." A negligible difference

existed between cycled and tuicycled fluid.

The bulk modulus of a flowing fluid was also obtained. In determining

this bulk modulus, the wave speed of a distrxbance induced in the fluid

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is measured and combined with the fluid density and tubing correction -

4factors to obtain an adiabatic bulk modulus as expressed by t4he reltion: '

- (See Apfieni*A)

vhere "a" is the wave speed.

Based on the data obtained, the following conclusions are realizea.

1. For system conditions involving dormant unpressurized periods, as

in utility systems, the fluid bulk modulus is initially Io but

approaches the published value within the first moments of system

actuation.I

2. Dissolved and entrained air or gas remaining within a hydraulic

system iihich is continuously pressurized has no appreciable effect

on the fluid bulk modulus and consequently the system stiffness.

This effect applies to prima-y flight control- systems -and to systems

in wihich the actuator remains presaurized but inactive over extended

time periods.

3. Acceptable correlation was obtained between our bench measurements.

and published data for M2-H-5606B and wSX-6885 fluids. With Skydrol

500A an accurate assessment y;as difficult to realize due to the in-

consistency of the published data available.

4. The system measurements produced initial values which compared very

favorably with the bench results for the three fluids tested.

0

A IA~bNO D6-58.',.i2TN _REV SYM

PAGE7006-7000

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i • 5. The system measurements following pressurized dormant periods

yielded the mst accurate correlation with the initial system -

values .nd subsequently the bench and published values.

-6. The method employed to measure the bulk modulus of a flowing fluid

also produced acceptable results for both WSX-6885 and Skydrol 500A

fluids.

I -I

.- D6-58362TNREV SYM 4lEflN NO.N

6-7000[

IIII. INWhotNCfo

This investigttion arose from the need to obtain ad tion&. 1ru ,i.

on bulk modulus of a fluid in a hydraulic systm, as the vlue of

bulk modaulus used in calculations is often arbitrary or selected -'o

the basis of experience. Bulk modulus is a measure of the cor4gessibwl.b

of a fluid, and is an important fluid property in system design as it Afftts

such system factors as response tim, force available from livited strcae

actuators and stability of hydraulic servos and servo.controlled byx#&lic

systems. The data compiled in this docmwnt should provide an insiot

into the behavior of bulk modulus under actual operating conditions.

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Iswoirml necet bulk molaus, am *1 .evel tam or bulk m~l n

A meare of fluid stiffness., is the wmt coeoly found form in reftmeeo

surcis. It is defined as the total ehange in fluid pressure dividet by

the total change in fluid volu per unit volm under pressure at constant

* tm t eraturt. The Iquation for this form of bulk modulus is

VtGraphically, it is defined as the slope of the line conAecting two pressue

of a pressure versus AV/V Curve (Figure 4).

In this investigtion, fluid isotherzal secant bulk modulus values were

obtained for three fluids at various temperatures and pressures.

,Mesaurements vere made both in a standard bench fixture and in a hydraulic

sevo-actuator system The purpose of using two systems was to investigate

any variations in bulk modulus obtained vith fluid contained vithin a

siwsated flight control system and values obtained in conventional

static tests. The fluids used wre KL-1-56of0, WSX-M8., and Mydrol 50(.

The WUX-(5 fluid is under consideration for use in the Supersonic

Transport vhile the other two are production fluids in general use in

military and comrcial aircraft.

noe Pressure-Volue-Temperature method vas used to obtain the data.

This method yields the volume change for a pressure change eerted on a

given initial fluid volume. The values obtained can be substituted in

the relation above to obtain the bulk modul value.

AO :s4 iN D6-58362TN

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, A. Description of Test$The bench fixture consisted of a coil of tubing as the test section and

a hand pump and associated equipment (Figures 5 through 7). This

system has been used in previous tests at Boeing for the measurement

of fluid bulk modulus values. The hydraulic system employed a servo-

controlled single-ended actuator loaded by a torsion bor. The test

section comprised the actuator to servo-valve tubing and is pressurized

by a hand pump connected to the head end of the actuator (Figures 8

through 10). l easurement procedures are identical for both systems.

In selecting the tubing as the test section instead of the actuator,

the following criteria were used. In using the actuator with ,he head

end comprising the test cavity, the piston seal leakage and structural

compliance of the actuator could not be accurately determined for

all conditions investigated. The leakage is directly related to the

bore-to-seal clearance. This clearance is affected by pressure, struc-

tural compliance of the barrel, longitudinal position of the seal in

the barrel, and the seal wear. In addition, a suitable m,!ans of locking

the piston-rod was necessary. The use of tubing alleviates these pro-

blems rs a leak-tight chamber could be attained between two valves and

the compliance of the tubing could be determined mathematically. Because

the test section comprised the rod end to servo-valve tubing, it was

assumed that the fluid in this section and in the actuator is subjected

to nearly identical conditions. Therefore, the bulk modulus values

obtained are representative of the fluid bulk modulus in the actuator.

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In addition to the above static values, the bulk odulus was also obtained

for a flowing fluid by means of wave speed measurements. For measure-

ment of the bulk modulus, a section of tubing approximately 100 feet in

length was incorporated in the servo-actuator system adjacent to the

pump. This section was equipped with a solenoid valve for testing of

WSX-6305 and a pressure control servo-valve for Skydrol 500A fluids.

Pressure transducers were incorporatea in each en! of the test section

to determine the elapsed wave travel time of the disturbance created

by closure of the valves. (Figure .ond 12). The wave travel

Itime was utilized to determine the wave speed of the disturbance. The

heating and cooling effect generated by compression and expansion waves

occurs very rapidly end may be considered an adiabatic process.2'3

Therefore, the wave speed in conjunction with the fluid density and

tubing correction factors yields an adiabatic bulk modulus when sub-

stituted into the relecion

(See Appendix A)

in which "a" is the wave speed of the disturbance.

B. Test Procedure jThe data was taken under the following conditions for the three fluids Iunder consideration.

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In order to determine if system cycling vilU restore the value of bulk

modulus to its initial value following dormant unpressurised periods, tvo

full stroke cycles. vere conducted after data vas taken at four hours.

Following bulk modulus measurements, two more cycles and isasuroments

were made. This sequence was performed at 100 7 and 350 F and at

100 7 and 200 F for WX-6885 and Skydrol 500A fluids repectively vith

measurements being made at 1000 and 3000 psi.

Bulk modulus mesurents vere made three times at each taerature and

series of pressures. for each specific fluid. System cycling was

conducted for fifteen minutes prior to the initial measurements.

FoliowirW a four hour dOrsnt period at zero pressure, the bulk modulus

uesurements were repeated. A final measurement vas made after a second

dormant period of 18 to 11h hours. This procedure was folloed for all

three fluids Qnd, iz addition, was repeated for WSX-6885 and S Idro 500A

with a pressure of 100 psi on the test section 4uring the dorxant periods.

NO D6-58362TNREV SYM >

PAGE 24!6-7000

Rteaded cycling vith 14-3606B vex also conducted for perids.d

T and 14 hours. ftlk modulus masurw t r* we t a t atui

of 200 F and pressures of 2000, 3000, 4000, and 5000 peL. The domat

periods ere conducted at zero pressure. Folloving the fttead e all -

the system vex drained and refilled witb now H1L-5606 fluid sad the

bulk nodulus measuremnats repested nder the previously mextbodeI

procedure.

C. Test Results

1. Bench and System Tests

In cmparing the bulk modulus relues obtained with MIL-H-5kf63, the

bench data and system data for uamycled fluid yielded cmves of the

same general slope. The system values exceeded the bench values

(Figure 13 ). Although the numerical values are noticeably

different, the deviation did not exceed T-5 percent (Figure i| ).

In comparing this data with published data from The Boeing Design

Manual, the difference in curve eloe is consderable (Yi pre TO .

However, the waxinum deviation between the bench and published data x

vres loss than 8 percent (Figu).

In coaparison of the hydraulic system data, the initial wslues were the

highet; the four hour values, the lowest (Figures 16 throug 22 )

The 18 to 114 hour values were between the initial and four houX data

with the exception of two cases in which these values Vere lebstben

the four hour values (Figures 18 and 19 ).

Althou&h the fluid volumes in the bench arA system test difftwed

by factor of roitely three, the AV's reord4 d4ffewd

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-Yid 6 A V/V- of 317. -A similar. A V of' 11.7 cc f'.1 the system vith

oinitial voum f30 cyedda 4 v/v of' 2.96. Although the date

taken exhibit sofae repentability, particularly good. vwhen comparing ini-

tial with initial, etc., an- exnplanation for the variance with time is

not apprent (Figuf es 23 throughb 28). One possibility is that air comes

out of' solution during the dormant peroscausing the bulk modulus to

decrease. WHith subsequent pressurizations (0-2000 .rsi initially) the

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-j by the 18 to 114 hour diata. -'I may also explain the increase in slope

oblai.-ed- with 4 hour and 16 to i14 hour -datea. Cbservance of' this trend

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Aior in Inter I.WSX-6835 and Sk-drol 5001kess

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- similar so the accuracy obtained was deemed sufficient. The deviat1.ion

bet:ce-i the nc~. anid published data reached a maxi;mun of' . ecn

st 10 F h f' 7 percent at 350 F (F!Iur 31)

The systcem data f'or ISX-C3135 elxhiuited a slightly different, trend than

,,te;L--H-56&,6B data. The initial values were the highest1, with the

4 and 18 hour data follo-w.ing- in decreasing order (Figures32 and 33).

- This data was for zero section zressure during the dormanlt periods.

* Wi.th c. nressure of' 100 psi on. the test section during the dormant

periods, the bulk moaulus measurementS yielded data that was

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repeatable within test tolerances (Ptgures 34 and 35 ) A possible

ezplan tion for these results, in accordance with the reason twen-w.i, to°istat ther. -us ins olution ith the 21%i uih

preion-y t00t" i into resure Inumpriag -the variation of the bul modulug wjtb f

tim , the effect of prepssrization -during dox'.nt..perioda can leo .be

-6ee0A ith the 18 hoQ- tilus ,e mging little fr* the initial wales

4 pa~30. through 41 )

Fluid cying fo wowing a four Jhour dormnt period yielded greatlydifferent results for each, teUperture. At 100 the four hour dat

decreased as-erpected, further decreased following two cycles, .and

increasied after two additinal. cycles (Figue 4~. The slo1 of the

curVes :also changed. At -359 F the slope of the -curves, changee

slightly ith cycling wvith the values reumaining essentially unchanged

The bench daita obtained vith Skydrol 500A fluid was compared vith

.published data from three sources -as sufficient single source-datawas not-aiailable (Figures 42 and 43 ). This data vas obtained

from The -Boeing Design.Manual and from tvo separate Monsanto sources,

jDuw to the inconsistency of this deta vhen compared, the deviatioas

betven bench. and published data were not calculated as they vould be

.meaningleas. This inconsistency is not unconmon vhen bulk modulus

data from various sources is compared 'and further coeplicates the

pioblea of determining the most correct value.

The system Ata for Skydrol 500A exhibited a trend similar to the WEM-

.6885 date. With zero test section pressure during the dormant periods,

* t the initial ,a:ues were the greUtest followed in decreasing order

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test section prsessure d'uing the domwAt periods, the bulk voidju JL~td

vas repeatable within the accuracy of test nMMretdts (yijiSe ,q46.

and 47]). C~qaring this data vith the WM-68 4ata i11utm&t +thg

sililar tns4 mentioned prewiousl. This cmpftsm also Uztse

that due to the similr results vith pr*usurisstion the ga& Ok

could Possibly be rek.tse4d with fl.uids other than MUS-6885 szd

%drol 5"C. ftzuintiz of the vari~ation of bulk modulus vif* t1W

for Mgrdrol 500A also *bows the effact of pressritionL with t2~a

and 18 hour values varying little fom the initial values (?'4gurs

48 through 51 )

For Mydrol 5MQ1., cycling follvizaing the four hour dormant peito yie1*3e

similar results at both 100 F and 200P. The four hour data 4.oj'assd

marktedly from the initial date. Nearly eo,~1ete recovery oc*=l'2a

following two cycles, with complete recovery after two additional

cycles (Figures 52 and'3 ) At both tenersturee, the slop of

the four 'hour curvac increased sharply but decreased with cycIUng

to alo~ely approximto the initial curve slope.

In cycling with WB-6885 and fydrol 500A the MWui which vas not

initially in the test section and subjected to the praxsuriSatjW~-.

during msurci and to test te~eratures durixg the dqr*M periods

enters the test section. After two cyc3es a portion of this f1204

reimins in the toot section. 'Assuming no axing, aprjty

5 cubic Inehes of fresh fluid rei~ans in the test section

(voluse ~- 94 cubi* inches) (Figure .54; ) As an be *eea, this

volui* of 'oil. is exchanged with each paiLr of fall strok,# eycles.

his fluid could possibly alter the bulk modulus ValUws obtained

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due to its different temperature and possibly different eottentof dissolved and entrained air.

2. Wave Speed Neasurarents with a Flowing Fluid

In analyzing the test data, bulk modulus values were computed based

on the wave speeds obtained from oscillograph recordings. The

wave speed is affected by temperature but is not a function of

flow rate (Figures 55 and 56 ). An average bulk modulus was

ccauted for identical flow rate and temperature conditions.

These values are compared with published data and tabulated

(Figures 57 and 58 ). Adiabatic tangent bulk modulus ditta

for WSX-6885 fluid was ottained from information available within

Boeing (Figures 59 and 60 ). Comparable data for Skydrol 500A

was obtained from Monsanto publications (Figures 60 and 61

L2

The maximum deviations of test data to published data was 15.6

percent at 100 F for WSX-6885 and 13.8 percent at 100 F for

Skydrol 500A (Figures 57 and 58 ). The following discussion

may in part explain these deviations.

In determining the bulk modulus by this method, the most accurate

value would be obtained from a single instantaneous disturbance.

This would be the ideal case and would theoretically be a vertical

pressure trace on the oscillograph recording at time zero. A

disturbance of this type is not possible due to hardware

limitations. However, this condition can be approached by

utilizing the most rapidly closing valve obtainable. A rapidly

cloaing valve is one which has a closure time of less than 2L/a,V)

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this being the time required for the disturbance to transverse the

length of the line and return. Construction of the valves utilized

for these measurements prohibited determining the closure time. However,

an estimpte of this time may be obtained by observing the pressure traces.

This was comlicated by the fact that .ump ripple was superimposed on

these traces.

In testing with WSX-6335, the percentage of air in the fluid was obtained

by use of the Seaton-Wilson "Airometer." Fluid samples of new and

cycled fluid .:ere taken, the cycled fluid being drawn fro= the system

follo:ing 2- minures of cycling nn, after the 4; and 18 hour dormant

periodS at a temnernture of I01? ?. The new fluid yielded an average

cf 6.75 percent air. .in th.e c>,-led fluid, the air content ranged

from C.5 to 0 percent (Figure 63 ). Cycling the fluic did not appre-4

ciably change the air cont,-nz as can be seen. Both dissolved andK z.trt.'i:5 . . air is reflected in these measurpments. However, as the

samnles could not be evaluated Lmmediately upon removal from the system,

it is susnected that the entrvir.2d air migrated to the fluid surface

and ;as relea:-d. An in.ication cf this was the formaLicn (f an air

bubblc ,bevo the sape is a prcviously full contciner. .'o, the value.

obtained are rrobably mo'-t reresr.ntctive of the air dis.,colved in -he

fluid.

o

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I *63

D6-583621 N81

V. CONCLUSIONS

Based on the data obtained, the following conclusions are realized.

1. Acceptable correlation was obtained between our bench measurements and pub-

lished data for MIL-H-5606B and WSX6885 fluid. An accurate assessment of

the Skydrol 500A data was difficult due to the inconsistency of the published

dato available.

2 The system measurements produced initial values which compared very favorabl/

with the bench results for MIL-H-5606B and WSX-6885 fluids The data obtained

with Skydrol 500A bracketed the initial values with the curve having a slightly

greater slope.

3. The system measurements folloving pressurized dormant periods yielded the most

accurate correlation .,ith the initial system values and subsequently the bench

and published values.

4. in measurements for a flowing fluid, the method employed also produced accep-

table results for both WSX-6885 and Skydrol 500A fluids.

5. For conditions of continuous demand and pressurized dormant periods, which

exist in flight control systems operations, the fluid bulk modulus does not vary

appreciable from published data obtained by the Pressure-Volume-Temperature

method

6. For aircraft operating periods with the system unpressurized, as in utility systems,

the fluid bulk modulus is low initially but approaches the published value within

0 the first moments of system actuation. Therefore, for design purposes, the pub-

lishel value would be the most accurate.

REV SYM f ,/i/VG NO D6-58362TN

PAGE

82 6-7000o

VI. REFERENCES

1. "Isothermal Secant and Tangent Bulk Modulus of Selected Hydraulic Type

Fluids to 750 F and 10,000 psig," Vern Hopkins, Donnel R. Wilson, Calvin

Blaze, Midwest Rese .rch Institute presented at ASME Lubricction Symposium,

June 3-5, 1063.

2. "High Intensity Altrosonics," Basil Brown, John E. Goodman, D. Van Nostrand

Company, Inc., New Jersey, 1'65

3. "Mechanics of fluids," Irving H. Shames, McGraw-Hill Book Company, Inc.,

New Yo-'., 1062

4 "Fluid Mechanics," Victor L. Streeter, McGraw-Hill Book Company, Inc.,

New York, 1q62

5. Boeina Document D6-1 726TN, Physical and Chemical Evaluation of Candidate

Hydraulic Fluids for Super onic Aircraft (Se.ternber 8, 1964 through January 31,

1967), March 9, 1967.

6. Boeing Document Do-51225TN, "Analytical Method of Obtaining Fluid Tangent

Bulk Modulus fom a Sincde Seccnt Bulk Modulus Value by Least Squares Curve

Fit," August 10, 1967.

7 Monsanto Technical Bullti No. AV-1, "Skydrol 500A and Skydrol 7000 Fire

Resistant Aircraft Hydraulic Fluids, revised July, 1064.

R E V S Y M _ _ _ _ _ _ _ _j _ 4 o D 6 -5 83 6 2 T N

AL83 6-7000

{) APPENDICES

IN.D -86T/E S MPA-F

8 6 700

APPENDIX A

Derivations and Calculations

$ I

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OPN=IX B

Miscellaneous

RESMASir~~fN,.D-86T

PAG 9067 0

1- 0

C 0 M P A N Y

St. Louis: Missoar;

Septceibor 16', 196 N *).

1 :il:zon ra~ntbnEa:ncrn Dept.

2iE I;cinxg Coap any

UWilzon:

L.it:C! --o D~cing ro;Zuestd 1 -t we Supply your co=-anyto-~ Ca-ta :**.l.tinZ to SkYdrol 500Ak, Skydrol 50013 and 56306.,

-~ Socical2.yyou retstdvisco.-ities, densities, p~-&3zsr viscos-i-ies, balk mnoduli, a.nd va-por prcisuras i'or,

i3c odu.cts. in addition you requeLsted air Solubility-:I siz d of sound dat%-a for .- '$kydro1 500.1. Attcehcd to

th~letter our~ a num.ber of' data saeets on which you *illiad tha rccquastcd inf'orzation. If' we can be of any-

further service to you on -his subject please lot us know,

Vary truly yours,

P. H. Lanacelfeld

/cc

cc; 11r. jarry johnzoii:atariol Ln~inering Dlept.

Enalzearing Staf.t

D6-58362TN

1666

Page 1

MONSANTO COMPANY-. * : ORGANIC DIVISION RESEARCH DEPARTMENT

-Msellaneous Monsanto Data on.Skydrol 500 and MI-H-566

.slydl ,500 MIL-H-5606A B A B

l" V"LSO S:,t -CS- at -40F 562 761 471 46900., 100.9 105. 4 103.6 97.1

.OO , 11.70 11 .79 14.56 14.31"20F 3.91 3.96 5.24 5.23

2. Denaitr m/n.at -40OF 1.1213 1.1203 O.q042 0.9109o F 1.102o3 1..19o 0.8881. o. 8 #84

10 , o1.0545 1.0532 o.8487 o.8542

210°F 1.002-5 1.0010 o.8051 o.8104

XpsL.-at 1009F 264 278 229 229era . 2000? 22J 186 179

dSeart 0-7 300 -? 165 17 139 139

M . ?P'es~su Viscos-i.ty,> S at 2 Kpsig 13.9 13.4' 19.8 17.3

(100.p) 4 16.5 15.0 25.9 21.06 Kpsig 19.4 16.8. 34.8 25.5

5. Vapor Pressure,, =ng at .50° 1.2 3.0 o. 0.8 -

150°F 15.2 44 6.9 42250P 77 235 30.5 77

. D. R. iller

D6-58362TN92

I Af.11 *..

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* -

SAN.

9/T~f PAO~~l~ - -

ORGANIC DIVISION RESEARCH DEPARTMNT. "' " "

Xiscellaneous Monsanto Data on Scydrol 5O0)\ ' 2 . -

6. Air Solubility in Skydrol 500A at 100*F -

Vol. % air (68*F, 1 atm. abs.) 0.54 p(psia)

PPM (wgt.) air = 6.4 p(psia)

Estimated accuracy of constants +5%

Measurement range 14.7 to 115 psia

7. Sonic Velocity of Skydrol 500A at atmospheric pressure

(meters/sec.) = 1435 - 3.25 tFC= 1493 - 1.81 - '

Estimated accuracy of constants + 1%

Measurement range 0 - 100 0C

8. Sonic Velocity of Skydrol 500A at 100°Fj meters/sec.

Sample Air-Saturated at 1000F andPressure, psig 0 psi; ,(as-il ~ .... -

0 1310 -

100 - 13121000 ' 1335 13402000 13.1 13673000 1387 13974000 1415 14255000 144 1453

D. R. Miller

V/

D6-58362TN93

!.i ....

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II7, 6-58362TN

"TECHNIQUES FOR MEASURING ANDREMOVING AIR FROM HYDRAULIC

CONTROL SYSTEMS"

V. G. Magorien, Chief EngineerSeaton-Wilson Mfg. Co., Inc.Burbank, California

Presented before the ZZnd annual meeting of the National Conference onFluid Power, October ZO -21, 1966

P-5362T N95

TABLE OF CONTENTS

I- -AMPLE.Ar'R TESTS . . .. . . . . . . . . . . . . .

SFORMS OF AIR . ...... ..

JV. ADDITIONAL DATA ON DISSOLVED AIR . . . . . . . . 2

-. DESCRIPTION OF AIR MEASURING EQUIPMENT . . . . . . 3

V1 DESCRIPTION OF AIR SEPARATIOW EQUIPMENT * , , . , , 4

VII RESULTS OF AIR REMOVAL . . . . .. , . , .... 4

VIII CONCLUSIONS C * * * * . . . . . . .. . . . . . .5

APPENDIX . . . . . . . . . . . . . . . . . . . 7

LIST OF ILLUSTRATIONS

,FIG. I -TEST CYLINDER

FIG. 1I FLUSHING CYCLES VS AIR CONTENTF IG. ii CURVES OF OIL VOLUMES REQUIRED TO PRODUCE

VARIOUS CYL IN E . PRESSURES

FIG. IV BULK MODULUS r VARIOUS AIR CONTENTS

ItG. V AIR CONTENT GENERATED FROM DISSOLVED AIRFIG. VI ILLUSTRATION OF THE THREE FORMS OF AIR

.FIG. VII" DISSOLVED GAS CONTENT OF VARIOUSHYDRAULIC FLUIDS

FIG, VI Il A-400 "AIRE-OMETER"FIG. IX AD-4001 "AIRE-OMETER"FIG. X SAF-OO1 "SEPARATE-AIRE"FIG. XI SCHEMATIC OF CLOSED RESERVOIR TEST SYSTEM

.FIG. XII SYSTEM DISSOLVED AIR CONTENT VS RUNNING TIME

'FIG. XIII CYLINOER AIR CONTENT WHEN FLUSHED WITHUNSATURATED OIL

D6-58362TN

"TECHNIQUES FOR MEASURING AND REMOVING AIR

Fr,0M HYDRAULIC CONTROL SYSTEMS"

I GENERAL

IT IS A GENERALLY ACCEPTED FACT, THAT HYDRAULICS US AN

iXCELLENT METHOD OF POWER TRANSMISSION. THE PRIME REASON FOR

THIS ACCEPTANCE IS IT'S INHERENT STIFFNESS. DUE TO THE VERY

HIGH BULK MODULUS OF MOST FLUIDS, THE POSITIVEs PRECISE

POSITIONING OF A RAM OR A SHAFT SHOULD BE A CERTAINTY; BUT IS

IT?

TRUE, ONE CANNOT SAY THE SYSTEM IS "STIFF" UNLESS IT IS

COMPLETELY FLUSHED OF AIR; HOWEVERt ONCE THAT IS ACCOMPLISHED,

THE SYSTEM SHOULD BE "SOLID." THE WO)RD SHOULD IS USED BECAUSE

THE STIFFNESS OF A SYSTEM IS RARELY MEASURED IN A QUANTITATIVE

MANER. THIS OVERSIGHT MIGHT BE EXPLAINED AWAY BY CALLING IT

AN INTERFACE PROBLEM. THAT IS, IT IS THE POINT WHERE THE

DESIGNER LEAVES OFF AND THE TECHNICIAN TAKES OVER. Too OFTEN,

IT IS THE RESPONSIBILITY OF THE TECHNICIAN TO KNOW WHEN TO

STOP FILLING AND FLUSHING. IT IS SOMEWHAT ANTI-CLIMACTICAL

TO GATHER A LARGE NUMBER OF MEASUREMENTS ON INDIVIDUAL COM-

PONENTS; AND THEN, AT THE LAST MOMENTs NOT MEASURE THAT WHICH

WAS DESIRED IN THE FIRST PLACE!

iHE PURPOSE OF THiS REPORT IS TO DESCRIBE TECHNIQUES ANDDEVICES FOR MEASURING AND REMOVING AIR IN ORDER TO INSURE A

STIFF, HIGH RESPONSE SYSTEM.

I SAMPLE AIR TESTS

IN CROER TO OBTAIN DATA WHICH WOULD BE BOTH SIMPLE, YET

MEANINGFUL, A CONVE.TIONAL, DOUBLE-ENDED ACTUATOR (SEE FIG. I)WAS CCN;ECTED TO A I GPM, 3000 PSi, MiL-1--5606, HYDRAULIC

SYSTEM. IT WAS THEN INSTRUMENTED WITH A DEVICE WHICH WOULD

MEASURE THE COMPRESSIBILITY OF ANY AIR-OIL MIXTURE. THE

MECHANICS OF THE INSTRUMENT WILL BE EXPLAINED LATER.

STARTING WITH AN EMPTY ACTUATOR) FLUSHING BEGAN AT LOW PRESSURE;

I. E., APPROXIMATELY .300 PSIG. THE CYLINDER WAS CYCLED 8Y

MEANS OF A FOUR-WAY VALVE WITH FLOW PASSING THROUGH AN

.032 DIAMETER ORIFICE AT THE CYLINDER PORT. THE PURPOSE OF

THE ORIFICE WILL BE EXPLAINED LATER. AFTER EVERY SIX CYCLES,

THE TEST STAND WAS SHUT DOWN AND AN AIR MEASUREMENT TAKEN.

A GRAPH WAS MADE, ILLUSTRATING THE DECREASE OF AIR VERSUS

FLUSHIJG CYCLES. (SEE FIG. II.)

IN ADOIT:ON, THE CYLINDER WAS PERIODICALLY PRESSURIZED TO

100, 2000 AND 3000 PSIG. THE AMOUNT OF FLUID REQUIRED TO

ACHIEVE THESE PRESSURES WAS MEASURED AND RECORDED. (SEE FIG.II I.)

THE EFFECTIVE BULK MODULUS @ 3000 PSIG WAS THEN COMPUTED FOR

-i - D,,3362T N-9/

FOR VARIOUS AIR CONTENTS USING THE VALUES OBTAINED. (SEE FIG. IV.)NEEDLESS TO SAY, IT WAS QUITE STARTLING TO DISCOVER THAT, WITH

A. CONTENT OF. ONLY .1% OF COMPRESSIBLE AIR9 THE THEORETICAL

BULK 'MODULUS WAS CUT IN HALF! THE FIRST INCLINATION IS -TO TAKE

"")" -LAcE tROH THE FACT THAT, AT THE LEAST, CAREFUL FLUSHING HAD

ZROU.GHT THE COMPRESSIBLE AIR CQhTENT DOWN T0.0.2 %. UNFOR-TUNATELY9 THIS VALUE DD NOT REMAIN AT 0.2%. AFTER FLUSHING,

THE-TEST STAND PRESSURE WAS INCREASED TO 1000 PSIG. THE

PURPOSE OF THE ORIFICE, UPSTREAM OF THE CYLINDER, WAS TO SIMU-

-'LATE THE AREA OF Al. .032 DIAMETER VALVE OPENING. AFTER ONE-

-H'ALf CYCLEj AN AIR MEASUREMENT WAS MADE AND FOUND TO BE 0.8%!AFTER. THE SECOND CYCLE, IT WAS 1.60 AND SO ON. (SEE FIG. V.)IN'SHORT, DISSOLVED AIR CAME OUT OF SOLUT!ON AND COLLECTED IN

--THE ACTUATOR. IT IS THIS FORM OF AIR WHICH NEGATES NORMAL FILL

-AND FLUSH TECHNIQUES. BEFORE CONTINUING WITH DESCRIPTIONS OF

AIR MEASURING AND AIR SEPARATING DEVICESt SOME DEFINITIONS ARE

IN ORDER.

ii FORMS OF AIR

FREE AfR: FREE AIR IS THAT WHICH IS TRAPPED$ BUT NOT

TOTALLY IN CONTACT WITH A FLUID. IT IS

NEITHER ENTRAINED NOR VISSOLVED. AN EXAMPLE

OF FREE AIR WOULD BE AN "AIR-POCKET" IN A

SYSTEM.

ENTRAINED AIR: ENTRAINED AIR IS THAT WHICH IS SUSPENDED IN

A FLUID AND NORMALLY EXISTS IN THE FORM OFSMALL BUBBLES.

DISSOLVED AIR: DISSOLVED AIR IS THAT WHICH ENTERS INTO

SOLUTION WITH A FLUID. SINCE IT IS NEITHER

FREE NOR ENTRAINED AIR, IT DOES NOT BEHAVE

ACCORDING TO BOYLE'S LAW. IT DOESV HOWEVER,

OBEY HENRY'S LAW, WHICH STATES THAT "THE

WEIGHT OF GAS DISSOLVED IS PROPORTIONAL TO

THE PRESSURE. t IT CAN BE REMOVED BY TWO

DIFFERENT MEANS: SUBJECTING THE FLU!D TO A

REDUCED PRESSURE AND/OR RAISING THE FLUID

TEMPERATURE. ITS PRESENCE OR ABSENCE DOES

NOT AFFECT THE VOLUME OF THE FLUID.

A PICTORIAL EXAMPLE OF THE THREE FORMS OF AIR IS SHOWN IN

FIG. VI.

IV ADDITIONAL DATA ON DISSOLVED AIR

SEATON-WILSON HAS MADE DISSOLVED AIR MEASUREMENTS ON SEVERAL,

COMMON, HYDRAULIC FLUIDS AND THE RESULTS ARE SHOWN IN FIG. VIi.

IT SHOULD BE EMPHASIZED THAT NEITHER THE PRESENCE NOR THE

ABSENCE OF DISSOLVED AIR AFFECTS THE VOLUME OF THE 0IL; AND

D6j-8362TN

-2-

TEST OATA SIEMS TO INDICATE THAT THERE IS NO EFFECT ON BULK

00 ,"MODULUS, PROVIDING THE AIR IS IN SOLUTION. THESE FACTS, AT

FIRST, APPEAR PARADOXICAL; HOWEVER, IF DUE VISUALIZES A

CONTAINER FILLED TO THE BRIM WITH MARBLES, WHICH REPRESENT THE

OIL MOLECULES, IT IS POSSIBLE TO POUR IN FLUID, REPRESENTI4G

AIR? AROuND THEM, OR REMOVE THE FLUID WITH NO CHANGE IN VOLUME.

THE .rEIGhT OF THE CONTAINER CHANGES, BUT NOT THE VOLUME. THE

APPEA,RANCE AND DISAPPEARANCE OF DISSOLVED GASES , IN THE FORM

OF ENTRAINED AIR, IS AN INTERESTING, BUT ELUSIVE, PHENOMENON.

ACCELERATING FLUID THROUGH AN ORIFICE CAUSES A LOCAL, STATIC

PRESSURE DROP. IF THE PRESSURE DROPS BELOW ATMOSP;ERIC

PRESSUR-E, DISSOLVED GAS APPEARS IN THE FORM OF TINY BUBBLES.

PROVIDING THESE BUBB3LES DO NOT CONGLOMERATE INTO LARGER

aUBBLES, Au() THE VELOCITY OF THE FLUID IS KEPT LOW, MOST OF

THE AIR B 'UBLES ARE READSORBED DOWNSTREAM WHERE THE STATIC

PRESSURE IS GREATER THAN ATMIOSPHERIC. THIS PHENO',EtJON AGREES

WITH 'FENRY'S LAW. THERE IS AN EXCEPTION TO THIS CONDITION,

HOWEVER; AND THAT IS, AS THE FLUID IS ACCELERATED CLOSE TO

ITS S3 NIC VELOCITY, THE AIR BUBBLES EXPAND TO LARGER SIZES

AND ARE RELUCTANT TO GO BACK INTO SOLUTION DESPITE SUBSEQUENT

EXPOSURE TO HIGHER PRESSURES. Too, EROSION OF MATERIALS HAS

BEEN KNOWN TO TAKE PLACE IN THE VICINITY OF BUBBLE GROWTH. IT

IS NOT THE PURPOSE OF THIS REPORT, HOWEVER$ TO INVESTIGATE

ER3S ION.

V 3ESCRIPTION OF AIR IEASURING EQUJIPMENT

SItCE AIR CAN EXIST IN EITHER COMPRESSIBLE OR INCOMPRESSIBLE

FCRM.5 IT IS NECESSARY TO HAVE TWO, DISTINCTLY DIFFERENT MEANS

OF MEASURING ITS PRESENCE. To FILL THESE NEEDS, SEATON-ILSON

MANUFACTURING COMPANY HAS DEVELOPED TWO INSTRUMENTS:

A. A-4")O "AIRE-O;"ETER" (SEE FIG. VIII.)

TiIS DEVICE IS USED TO MEASURE COMPRESSIBLE AIR

COtTENT. IN PRINCIPLE, IT TAKES ADVANTAGE OF AIR'S

COMPRESSIBILITY. THE AIR IN A CLOSED SYSTEM IS

PRESSURIZED TO A PREDETERMINED LEVEL, EITHER WITH

ITS OWN FLUID OR FROM AN EXTERNAL SUPPLY. AFTER! "ZEROING-OUT '" THE INSTRUMENT, THE PRESSURE IS RELIEVED

AND THE COMPRESSED FLUID IS ALLOWED TO EXPAND INTO A

MANOMETER TUBE, WHERE IT IS MEASURED. ' Y MEANS OF

BOYLE'S LAW, THE AMOUNT OF TRAPPED AIR .AN BE CALCU-

LATED.

B. AD-4-001 "AIRE-OMETER" (SEE FIG. IX.)

THIS DEVICE IS USED TO MEASURE DISSOLVED AIR CONTENT*

IN PRINCIPLE, IT TAKES ADVANTAGE OF THE FACT THAT

GAS WILL COME OUT OF SOLUTION WHEN EXPOSED TO A

VACUUM. A SMALL FLUID SAMPLE IS TITRATED

D6-58362TN

-3- 99

I FROM THE UPPER RESERVOIR INTO THE LOWER TUBE, USUG

MERCURY AS THE WORKING MEDIUM, AND THEN EXPOSED TO A

VACUUM. AFTER THE GASES HAVE ESCAPED, THE AIR-FLUID

MIXTURE IS PRESSURIZED TO ATMOSPHERIC PRESSURE AND

THE VOLUME OF GAS MEASURED.

VI DESCRIPTION OF AIR SEPARATION EQUIPMENT

To REMOVE ALL THREE FORMS OF AIR? SEATON-W4ILSON HAS DEVELOPED

AN AUTOMATIC AIR SEPARATOR. (SAF-IC01 "SEPARATE-AIRE")(SEEFIG. X.)

SINCE DEGASSING CAN ONLY BE ACCOMPLISHED IN THE PRESENCE OF

A VACUUM; YET, A NEGATIVE HEAD IN A RESERVOIR RESULTS IN

PUMP CAVITATION, THE FLUID MUST BE PROCESSED IN A SEPARATE

CONTAINER. AFTER THE FLUID HAS BEEN DEGASSED, IT-MUST THEN

BE PUMPED BACK UP TO SYSTEM RETURN PRESSURE. TO ACHIEVE THIS,

THE "SEPARATE-AIRE" USES AN ASPIRATOR TO BOTH DEGAS AND JET-

PUMP THE PROCESSED FLUID UP TO SYSTEM RETURN PRESSURE. THE

"SEPARATE-AIRE" IS PLACED IN A SYSTEM IN PARALLEL TO THE LOAD,

AND THUS OPERATES AT SYSTEM PRESSURE. (SEE FIG. Xi.) UNLESS

"VALVTD-OFF I FROM THE SYSTEM, IT WILL MAKE A CONTINUAL BLEED

OR DRAIN ON THE HYDRAULIC HORSEPOWER PROVIDED BY THE PUMP.

FLUIDS TO BE DEGASSED, IS INTRODUCED FROM THE RETURN SIDE OF

THE HYORAULIC CIRCUIT. SINCE UNSATURATED FLUID IS ASPIRATED

N % INTO THE SAME STREAM, WHICH IS CREATING THE VACUUM) MIXING

OCCURS. THE DEGASSING PROCESS CAN NOW BE SEEN TO BE A PARA-

SITIC ONE, AND A CURVE OF DISSOLVED AIR CONTENT VERSUS

RUNNING TIME OF A "SEPARATE-AIRE"t IS AN EXPONENTIAL ONE.

(SEE FIG. XII FOR DISSOLVED GAS CONTENT OF OPEN AND CLOSED

SYSTEMS.)

AFTER THE DEGASSING CHAMBER HAS FILLED WITH AIR, FLOAT SWITCHES

ARE USED TO SENSE THE END OF THE CYCLE. THE ASPIRATOR SOLENOID

VALVE IS SHUT OFF I AND THE VENT SOLEN4OID VALVE OPENED.

DEGASSING FLOW IS ALLOWED TO CONTINUE, AND SINCE IT IS NO

LONGER BEING A4-PIRATED, FILLING OCCURS. THE AIR IS COMPRESSED

TO A PRESSURE SLIGHTLY ABOVE ATMOSPHERIC PRESSURE AND VENTING

BEGINS AGAIN THROUGH A CHECK VALVE: FLOAT SWITCHES SENSE WHEN

TOTAL PURGING HAS BEEN ACCOMPLISHED AND THE ASPIRATOR IS

REACTIVATED TO REPEAT THE ENTIRE CYCLE.

VII RESULTS OF AIR REMOVAL

THE HYDRAULIC CYLINDER, DESCRIBED ABOVE, WAS TESTED WHILE

ASSEMBLED IN A SYSTEM WHOSE SCHEMATIC IS SHOWN IN FIG. XI.ALL OF THE COMPRESSIBLE AIR MVAqIIREMENTSI SHOWN IN FIGS. II,

IIl AND IV WERE MADE WITY AN A-400 "AIRE-OMETWR." ToEVALUATE THE EFFECTS Of AIR REMOVAL, THE AIR-OIL SEPARATORt

DESCRIBED ABOVE , WAS ALLOWED TO OPERATE FOR EIGHT$ 15 MINUTECYCLES. THE RESERVOIR FLUID WAS COVERED BY A FLOATING PISTON

D6-58362TN

4 100

-4-

J 4

AND THE DISSOLVED AIR CONTENT OF THE FORMER WAS MEASURED DY

l MEANS OF AN AD-4001 "AIRE-OMETER." A CURVE OF DISSOLVED AI'R

CONTENT VERSUS RUNNING TIME IS SHOWN IN FIG. X1I. THE ACTUATOR

WAS THEN RECYCLED AT LOW PRESSURES, AS BEFORE, AND AIR MEASURE-

MENTS WERE TAKEN EVERY SIX CYCLES. (SEE FIG. Xiii.)

IT IS WORTH NOTING THAT THE NUMBER OF FLUSHING CYCLES REQUIRED

TO ACHIEVE A SPECIFIC LEVEL OF AIR CONTENT DIMINISHED.

THE SYSTEM PRESSURE WAS THEN RAISED, AS BEFORE, TO 1000 PSIG.

TEN CYCLES WERE MADE AND NO ENTRAINED AIR APPEARED IN THE

CYLINDER, NOR IN ANY PART OF THE SYSTEM. (SEE FIG. XIII.)

Viii CONCLUSIONS

THE CONCLUSIONS THAT WERE DRAWN FROM THE TESTS WERE BROKEN DOWN

INTO FOUR SPECIFIC AREAS:

A. EFFECTS OF FLUSHING

THE EFFECT OF CONTINUOUS I HARD-OVER CYCLING UPON AIR

CONTENT AGREED WELL WITH INTUITIVE RESULTS* IN FACT,

THE FINAL VALUES ACHIEVED WERE FAR LOWER THAN WHAT

WOULD BE IMAGINED FOR A CYLINDER WITH "BUILT-IN" AIR

POCKETS.

ASSIDUOUS CYCLING CANI THEREFORE, BE EXPECTED TO

EFFECTIVELY PURGE ANY GIVEN SYSTEM OF AIR.

8. AERATION DUE To DISSOLVED AIR

ThE RESULTS OF THE IilGH PRESSURE CYCLING INDOICATE THAT

SYSTEMS USING AIR-SATURATED MIL-H-5606 FLUID, OR

SIMILAR HYDRAULIC F,.UIOS, AT PRESSURES OF APPROXIMATELY

1000 PSIG OR GREATER, CAN LOOK FORWARD TO THE GENERATION

OF ENTRAINED AIR ACROSS ORIFICES IN THE SYSTEM.I

LowJ PRESSURE HARD-OVER CYCLING OF ACTUATORS CAN HELP

REMOVE THE RESULTANT AIR IF THE CYLINDER TO VALVE LINES

ARE SHORT,

CYLINDERS WORKING UNLOADED AND ONLY IN THE MIO--STROKE.RANGE, WITH INFREQUENT HARD-OVER TO HARD-OVER SIGNALS,CAN EXPECT INCREASING AIR CONTENTS WITH TIMEo

C. BULK MODULUS

THE EFFECT OF AIR ON BULK MODULUS AGREED WELL WITH THFORY

WHERE THE AIR CONTENT WAS 4? OR MORE (SEE APPENOIX).AT

HIGH PRESSURE, THE CORRELATION FELL OFF AS AIR CONTENT

DECREASED; I. E4 , ADDITIONAL VOLUME WAS REQUIRED BEYOND

THAT DUE TO AIR AND FLUID COMPRESSIBILITY*

-5- D6-58362TN101

4 * ~ -- ,,* - 4 ~ - " -- **- 4'

THIS EFFECT COULD ONLY BE EXPLAINED BY THE ELASTICITY

OF THE CYLINDER, O-RING, END CAP, AND THREAD CLEARANCES.

0. EFFECTS OF DEAERATION

THE EFFECT OF DEAERATING THE SYS-TEM FLUID WAS TO PREVENT

-COMPLETtLY THE GENERATION OF ENTRAINED AIR ACROSS THE

SIMULATED VALVE ORIFICE. PREVIOUS TESTS, CONDUCTEDWITH UNSATURATED FLUID, INDICATED ACCELERATED PURGINGALSO TAKES PLACE JUE TO THE ADSORPTION OF SMALL AIRBUBBLES. FURTHER WORK IS NOW UNDERWAY TO QUALITATIVELY'DEFINE' THE REDUCTION OF PUMP NOISE AND MATERIAL EROSIONDUE TO THE USE OF UNSATURATED, HYDRAULIC FLUID.

E. GENERAL. CONCLUSIONS

IT IS READILY APPARENTI FROM THE TESTS MADE, THAT SEVERALAREAS OF PERFORMANCE CAN BE IMPROVED AS A DIRECT RESULTOF DEAERATING THE SYSTEM FLUID.

IN REGARD TO BULK MODULI, A WORD OF CAUTION IS NECESSARY.THE VALUES SHOWN ARE NOT B "MITTE0 AS PRAZClATIC NUMBERS

TO BE USED WITH ABANDON. tF ANYTHIN% THEY POINT OUT

THAT, FOR ANY SPECIFIC SYSTEMI ACTUAL MEASUREMENTS SHOULDBE MADE RATHER THAN RELYING UPON "1TEXT BOOK"I VALUES,

D6-58362TN102 v?'

X~~~ P: I 01

- A:~~~ i'NDIX--.-

THE FOLLOWING CHART CONTAINS ACTUAL AND COMPUTED THEORET-1CAL

VALUES OBTAINED FOR BULK MODULI TESTS:

(NOTE: 0.17, 0.97 AND 4-15 REFER TO AIR CONTENT'-IN:%) ".

PRESS: ACTUAL VOL. REQ'D THEOR. VOL. REQ'o DEVIATION - .

1 0.17 0.97 4.15 0.17 0.97 4.15 0.17 0.9? "4-15

45 .040 .25 .99 .042 .206 .2o 7 10.50 -- .41i 1..-4C 1000 .240 .52 1.43 .186 .428 1.44 29 24 0.75^" 0 -- .V-1 I .51

2AO .460 .71 1.59j .3n3 .553 1.57 52 29 1.2 "; -2500 -- .81 1 633000 .670 -08 173 j.415 .61 1.-C8 61 X5 2.9

*NOTE: AIR CONTENT DETERMINED @ 45 PSIG BY MEANS OF BOYLE'SEQUATION: Vi - P2 (V1 -V2)/ (P2 - P1 )

ORV1 4Av15E. G. ~V4x 04/ 3 =.53

o AIR= .053 x 100/32 " -. ;USE 0.1?'(ACTUAL CYLINDER VOLUME: 32 CUBIC INCHES)

TO FIXED DISPLACEMENT OF CYLINDER, O-RINGS AND END CAP THREADS

AT THE VARIOUS PRESSURES

THEORETICAL VOLUME REQUIRED WAS COMPUTED AS FOLLOWS:

TOTAL VOLUME REQUIRED = CHANGE I' OIL VOLUME + CHANGE

IN AIR VOLUME.

V TOTAL = (01L VOLUME X PRESSURE/ SULK 'MODULUS) + AIR VOLUME X

(1 - VOLUME RATIO)

PR-SSURE BULK MODULUS FqESSURE VOLUME RATIO

4c5 220,000 45 .33-,00 240,000 1000 .0152000 250,000 2000 00075000 265,000 3000 .005

E.G. FOR 0.17% AIR: (AIR CONTENT: 054 IN3 ; OIL CONTENT: 51.95 IN3

AV TOTAL = (31.95 x 3000/265,000) + .054 (1 - .005)

.362 IN3 + .053 IN3

= 0.415 CUBIC INCHES (THEORETICAL VOLUME REQUIRED)

D6-58362TN-7- 103

' i 1.9357 DIA, '

STROKE

TEST CYLINDER

FIG. I

, , o , !I 1 -1 E I.' ! .!LO,~V s..:,_R

2.2 _ vs'M i FsIRCIO'ENf I___ I .. ..-. t..I.....8.L..-..,. I

o 1.4 - i - , -

< N.w'zLO-I_-l

o Ir. ,.: t ,, t ,1 jin L - :- '-m

510 15 20 30 40 50 60 70

CYCLES OF ACTUATION

FLUSHING CYCLES VS, AIR CONTENT.

FIG. U[ D6-58362TN104

-' ,- -. l r Y.; :,:; -,,, -- ¢I-- -- -- r-',: -: , . . , - , . .. , .-. . . . .-p.- .,

*

4 '1OIL w/O% AIR BULK* ODULUS=0265,00 CALCULATED

CYLINDER, 0 RING & OIL V./.17

r-- AIR B...= 152,000 PSI ACTUAL

CYLINDER, 0 RING & OIL W/I%AIR S.M.= 100,563 PSI ACTUAL

CYLINDER, 0 RING & OIL W/4 K -AIR B.M. 55,312 PSI ACTUAL

p R Z ESS CYLINDER, 0 RING & OILPSI W~~V/ 10% AIR 8M2~2

CALCULATED

I 3000,1 r

2000

.1 .2 .3 .4 .5.6 .8 1.0 2.0 3.0 5.0ADDITIONAL VOLUME REQUIRED IN3

CURVES$ OF OIL VOLUMES REQUIRED TO PRODUCEVARIOUS CYLINDER PRESSURES

FIG.L'

25O3000 -.

o o,

-J

3 10 010 0

< 150,000

0 .17 1 2 34 5 6 7 8 9 104AIR CONTENT- %

EFFECTIVE BULK MODULUS AT VARIOUS AIR CONTENTS D6-58362TN 1FIG. ! 4

C Lt' ONK,

,-F.0

I 4 - - .*Wo- .

p t i -- x

.40

CC4 IP-1E3dTUATI O -1-~- -~ -IRT f 0Ntgtj jLU2 .GE-N

-- - - - - -

__-P t -P.,0

*,.OF--*, SOLUTIAN. ACRONitS- AN

~ -,BE

.w,. 4' ,

D4 -M " N

E' A. - . 4

~~TN,

.4.k

:1

* .le

CDi

0i0

0* 0

Z21 W) (I) r0 _- -. * -- __________________________

*J 0, 0 .

0 ) V)clo-

_ _ _ _ _ _ -.T

1AV

-- so

40108F I.l

A. W

FIG 2010

2-

K3

FI

0 0

-Cf)

coh

t. 'Vii o

-W.:

-- I

I. - - - 4,D6-58362. '

101

9.

-L - . VoJ1

-_ _" _- _ _ _ ".-_

Is 30 75 90 , 5 -

RUNNING TIME-MINUTES - .

SYSTEM DISSOLVED AIR CONTENT V$ RUNNING TIME

R0 T 3 L PI

- I I' E1S l l ; ; i

,o~ I . . .. -. .- ,_ , . ..

2.6 4i r 4 4• I NGE., i !IT R FLUSHE

-B -AE-NbE OF0L . . .ER-

t - U A -,- -' --

I q 1 1 1lI

FtG

z I.

LIST OF ILLUSTRATIONS

'II Figure Page

1 Definition of Secant Bulk Modulus 5It

2 Typical System Bulk Modulus Data - MIL-H-5606B 7

3 Typical System Bulk Modulus Data - WSX-6885 8

4 Definition of Secant Bulk Modulus 13

5 Bench System - Bulk Modulus Investigation 15

6 Bench System - Bulk Modulus Investigation 16

7 Bench System - Bulk Modulus Investigation 17

8 Test S ystem - Bulk Modulus Investigation 18

9 Test System - Bulk Modulus Investigation 19

10 Test System - Bulk Modulus investigation 20

11 Test System - Wave Speed Measurement Section 22

12 Test System - Wave Speed Measurement Section 23

13 Comparison of Bench, System and Published Data - MIL-H-5606B 26

14 Deviation Between Bench and System Bulk Modulus 27

15 Deviation Between Bench and Published Bulk Modulus 28

16 Bulk Modulus Data, System, MIL-H-5606B 29

17 Bulk Modulus Data, System, MIL-H-5606B 30

18 Bulk Modulus Data, System, MIL-H-5606B' 31

10 Bulk Modulus Data, 7-Hour Extended Cycling 32

20 Bulk Modulus Data, 14-Hour Extended Cycling 33

21 Bulk ModL'Ius Data, System, MIL-H-5606B 34

22 Bu!k Modulus Data, System, MIL-H-5606B 35

REV SYM ASUFfAEZ No. D6-58362TN

PAGE 1136-7000

LIST OF ILLUSTRATIONS

Figure Page

23 Variation of Bulk Modulus With Time 37

24 Variation of Bulk Modulus With Time 38

25 Variation of Bulk Modulus With Time 39

26 Variation of Bulk Modulus With Time 40

27 Variation of Bulk Modulus With Time 41

28 Variation of Bulk Modulus With Time 42 I

29 Comparison of Bench and Published Data - 100 F 43

30 Comparison of Bench and Published Data - 350F 44

31 Deviation Between Bench and Published Bulk Modulus 45

32 Bulk Modulus Data, System, WSX-6885 46

33 Bulk Modulus Data, System, WSX-6885 47

34 Bulk Modulus Data, System, WSX-6885 49

35 Bulk Modulus Data, System, WSX-6885 50

36 Bulk Modulus vs. Time, System, WSX-6885 51

37 Bulk Modulus vs. Time, System WSX-6885 52

38 Bulk Modulus vs. Time, System NSX-6885 53

39 Bulk Modulus vs. Time, System WSX-6885 54

40 System Data with Four Hour Cycling WVSX-6885 55

41 System Data with Four Hour Cycling WSX-6885 56

42 Bench Data, Skydrol 500A 57

43 Comparison of Bench and Published Data, Skydrol 500A Fluid 58

a 44 Bulk Modulus Data, System, Skydrol 500A 60

45 Bulk Modulus Data, System, Skydrol 500A 61

REV SYM AAhVII NO. D6-5362TN .

PAGE 11 6.7000

LIST OF ILLUSTRATIONS

Figure Page

46 Bulk Modulus Data, System, Skydrol 500A 62

47 Bulk Modulus Data, System, Skydrol 500A 63

4q Bulk Modulus vs Time, System, S: ydrol 500A 64

49 Bulk Modulus vs Time, System, Skydral 500A 65

* 50 Bulk Modulus vs Time, System, Skydrol 500A 66

51 Bulk Modulus vs Time, System, Skydrol 500A 67

52 System Data with Four Hour Cycling, Skydrol 500A 68

53 System Dcta with Four Hour Cycling, Skydrol 500A 69

54 Test Section Oil Change with Actuator Cycling 71

55 Wave Speed vs Flow, WSX-6885 Fluid 72

56 'Nave Speed vs Flow, Skydrol 500A Fluid 73

57 Bulk Modulus Data - Flowing Fluid - WSX-6885 Fluid 74

58 Bulk Modulus Data - Flowing Fluid, Skydrol 500A Fluid 75

5P Published Data - 100 F, WSX-6885 Fluid 76

60 Published Data - 200 F, WSX-6885 Fluid 77

61 Published Data - 100 F, Skydrol 500A Fluid 78

62 Published Data - 100 F, Skydrol 500A Fluid 78

63 Air Content Data, WSX-6885 Fluid 81

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24 6725 6826 6927 7028 71

29 7230 7331 7432 7533 7634 7735 78

36 7937 8038 8139 82 140 8341 i84

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