DESIGN OF AUTO-COMPENSATING NOZZLE FOR GATED IRRIGATION PIPES.

8/11/2019 DESIGN OF AUTO-COMPENSATING NOZZLE FOR GATED IRRIGATION PIPES.

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DESIGN OF AUTO-COMPENSATING NOZZLE FOR GATED 113

IRRIGATION PIPES.

Mohamed E. El-Hagarey1, A. M. Al-kot1

and G. M. El-Gindy2

Email: *[email protected]

ABSTRACT

Gated irrigation pipe is an important tool for improving surfaceirrigation, it's development on depends on replacing the gates by designed

auto-compensating nozzle (poppet nozzle). The main objective of this study

was to improve the distribution uniformity of water discharge along the gated

pipe length, by developing a newly designed and locally manufactured auto-

compensating nozzles (poppet nozzles), to take the place of the gates.

Poppet nozzle was tested and evaluated the hydraulic characteristics of a

auto-compensating nozzle (poppet nozzle). Three disc diameters (25, 27 and

29mm) were selected for testing under pressure head ranged between 0.33-3.4 m. The poppet nozzle (25mm diameter) was evaluated under operating

pressure head 50, 100 and 150cm.

The main results of this study showed the following: Under operating

pressure head ranged between 33cm to 340cm (3.3 to34 kPa), the mean

discharge of poppet nozzle with disc diameters of 25, 27 and 29 mm were

0.63, 0.46 and 0.28 l/s, and the mean corresponding discharge coefficients

(Cd) were 0.75, 0.79 and 0.9 respectively. Mean water discharge for 25mm

disc diameter was constant (0.81l/s) in spite of pressure increasing as a next

10, 30 and 34kPa (100, 300 and 340cm) with mean flow (0.81l/s). While mean

discharge for 27mm disc diameters was constant (0.48l/s) in spite of pressure

increasing from 6.8, 30 to 33kPa (68, 300and 330cm). Water flow through

poppet nozzle with 29mm diameter was shutting at operating pressure 12kPa

(120cm). The mean discharge of poppet nozzles along the pipes with initial

pressure head (0.5m, 1.0m and 1.5m) were 0.5, 0.56 and 0.64l/s, with mean

coefficient of discharge (Cd) 0.77, 0.75 and 0.72 respectively, For initial

pressure of 0.5, 1.0 and 1.5m the uniformity coefficient were 99, 91.7 and

90.2%, and the manufacture coefficient of variation is 0.094, 0.12 and 0.065

respectively.

Keywords: Surface Irrigation, Gated pipes, Poppet Nozzle, Pressure,

Uniformity.

1 = Researcher of irrigation and drainage unit, Desert Research Center.

1 = Assistant Researcher of Soil conservation, Desert Research Center.

2 = Prof. of Agricultural Engineering Ain-Shams University


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El-HAGAREY, M. E., et al. 114

INTRODUCTION

Water resources are the critical factor for all production process and

sustainable development in Egypt. Land and water recourses are considered as the

most key elements in the agriculture strategy which require improvement andenhancement in this use and management. Non-pressurized surface irrigation is the

most utilized existing irrigation methods. Improving this method is still less expensive

than the pressurized methods. Precise land leveling using laser technology and

gated pipes are technologies for increasing water applied and use efficiency.

Gated irrigation pipes history was recorded by Green (1973), it were

invented in 1945 by a machinist named Pau Hohnstein, at Nebraska, he made his

system of aluminum pipes with evenly spaced gates to control the flow of water.

Within a few years, the invention was successful and gated pipes were being used

around the world.

gated irrigation pipes need many operators with an experience in the

operation process. It needs calibration process of gated flow and insurance of gates

location; furthermore, with the lack of accuracy in terms of water distribution

uniformity, the flow area of gate has no flexibility (auto-compensating) to face the

change of pressure head along the pipe. Finally, the user must touch the irrigation

water during the gates calibration which he was exposed for diseases.

The main objectives of this study are as follows: 1) modification of gated

irrigation pipes systems to obtain high uniformity of water distribution pattern along

the pipe, 2) avoidance of exhaustive calibration process and 3) stability of nozzle

position reaching stability of flow performance during seasons.

To realize these objectives, the researcher:

1. Designed a modified auto-compensating nozzle for gated irrigation pipes and

studied the hydraulic parameters that would affect its performance.2. Evaluated the hydraulic and engineering characteristics of auto-compensating

nozzle along the pipes.

MATERIALS AND METHODS

Experimental site (Hydraulic laboratory):

Laboratory experiments were conducted at Hydraulic Laboratory of

Agricultural Engineering Department, Faculty of Agriculture, Ain Shams University, to

test and evaluate the hydraulic characteristics of a auto-compensating nozzle (poppet


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IRRIGATION PIPES.

nozzle) with three disc diameters (25, 27 and 29mm) testing under pressure head

ranged between 0.33- 3.4 m.

- Experimental apparatus:

The laboratory testing equipments contained an electrical centrifugal pump 1

/1.5 Inches (25-56 m pressure head, 6.6 m3/h discharge, 1.5kW, and 2860 rpm),

pressure gauges (10cm smallest reading), Manometer, control valves, and water

container.

Hydraulic measurements include nozzle discharge, operating pressure head,

and helical compression spring deflection measurements for various types of

designed nozzles were conducted. The development and modification of gated pipes

primarily depends on replacing the moving slid gates by auto-compensating nozzles

(PN) which can be operated with high uniformity, stability, and efficiency.

Auto-compensating nozzle design:

Form of discharge through orifice:

Q = Cd (a*V) ------------------- (1)

Cd= [actual discharge/theory discharge]

Where:

Q = Water flow through flow area (m3/sec.)

Cd = Discharge coefficient

a = Cross section of flow area (m2)

V = Velocity of water flow (m /sec.)

From dynamic energy of water the main velocity (V) could be determined

from the following equation:

V = (2gh) 0.5----------------------------------- (2)

Where:

g= Gravitational acceleration, 9.81, (m/sec2).

h= Pressure head (m). From equation (1) and

equation (2),

A = (Q / CdV). Where: A = D2/4.


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D2/4 = (Q / CdV) .

To get the flow area for desired flow rate (l/sec.) at a designed pressure, by using

continuity relationship

A = (/4) [dn2- dd2] -------------------------- (3)

Where:

dn= Inside diameter for nozzle body,( mm),

dd = Disc outside diameter,(mm),

From equation (3),maximum flow area (maximum nozzle diameter (dn))- fixed

disc diameter (dd) ) could be obtained at first poppet nozzle on the irrigation pipe at

operating pressure head 0.00 bar. While minimum flow area could be obtained at

maximum operation pressure head for the same first poppet nozzle.

From figs. (2, and 3). the maximum nozzle diameter (dn) equals 35 mm when

operated under pressure head equals zero on the disc, and the minimum nozzle

diameter equals (25 mm) at maximum pressure head.

By using disc diameters (dd) 25, 27, and 29 mm with equation (3), it is easy to

obtain (inside nozzle diameter dn) which is versus the operating pressure head.

Fig.(1):Isometric view for auto-compensating nozzle body (poppet nozzle)(no scale).


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IRRIGATION PIPES.

Fig.(2): Side view for auto-compensating nozzle body (poppet nozzle).

Changeable radius equals the half of difference for disc diameter (dd) and the

nozzle inside diameter (dn) with 6oslope angle Fig.(4)

Disc diameters (25, 27, and 29 mm) were tested and evaluated to obtain the

most appropriate auto- compensating nozzle design.

rx= 0.5 (dn - dd) ------------------------------------------- (4)

rx= ro (Tan * ) = ro 0.105 ------------------ (5)

Tan = tan 6= -0.105

Where:

rx = Space from disc edge to inside body nozzle at

second site (mm)

ro = Space from disc edge to inside body nozzle at first

site (mm)

= Slope angel (6)

= Spring deflection (mm)


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Fig.(3): Relationship between spring deflection and the change of the flow area

reduction.

Disc diameters (25, 27, and 29mm) were taken to carry out the auto-

compensating nozzle design. So, spring design was built according to the force

which faces the disc.

2-2-2- Helical compression spring design:

Since the spring design was built according to the force facing the disc

(Force (N) = operating pressure (Pa) * disc area (m2)), so, to design helical

compression spring, according to Vallance et al (1951), the following relationship

should be applied:

----------------------------------------- (6)

Where:

Dw = Spring wire diameter (mm)

F = Force at disk and spring (N)

Ci = Spring index

Na = Active coils

= Spring deflection (mm)

G = Factor of Shearing (80*103N/mm2)

G

NCFD a

w

3)(

=

w

m

D

D

Flow


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IRRIGATION PIPES.

=

mDp

1tan

Spring Index Ci = ---------------------------------------------- (7)

Mean Diameter Dm= Di + Dw ----------------------------------------------- (8)

----------------------------------------------------------(9)

Lo= Nap + 4Dw-----------------------------------------------------------------(10)

Ls= (Na+4) Dw+ [10 % Lo(as a clash allow)] --------------------------(11)

Where:

Dm = Mean diameter of spring coil (mm)

Di = Inside diameter of spring coil (mm)

= Pitch angle, i.e. the angle between the coils and the base of the

spring ().

p = Pitch, which is the distance from center to center of the wire in

adjacent active coils (mm).

Lo = Free length, i.e. the length of the unloaded spring (mm).

Ls = Solid length, the minimum length of the spring (mm).

Basic components of auto-compensating nozzle:There were two materials of plastic to be used:

A) Transparent acrylic plastic material is used to watch the mechanism of

water flow with poppet nozzle and measuring of the spring deflection. (for

experimental purpose only)

B) Delrin plastic is used to carry out field experiments.

Fig.(4):Basic inside components of auto-compensating nozzle.


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Measurements and calculations:

Hydraulic measurements and calculations include (outlet discharge, pump

discharge, control head pressure, outlets pressure, the friction head losess,

the superimpose head and helical compression spring deflection).Uniformity efficiency was calculated according to (Bralts et al, 1987)

.

---------------------------- (12)

Where:

UE% = Uniformity efficiency (%)

Qd = Absolute deviation of each sample from

the mean (l/s).

Qaver = The mean of outlets discharge (l/s).

-Flow rate through the poppet nozzle was calculated to be a power

function of the head in the followng form according to Jensen (1980).

q = b hx --------------------------------------(13)

Where:

q = Flow rate along the pipe (l/s)

b = Factor of the orifice dimensions

H = Operating pressure head (m)

x = Orifice exponent

- Manufacture coeffiecient of variation for desigend PN (poppet

nozzle) was calculated as follows:

MCV =(Qd/ Qaver) --------------------------------------(14)

Where:

MCV = Manufacture coefficient of variation for nozzles

discharge (%).

=

aver

d

Q

QUE 1100%


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IRRIGATION PIPES.

Qd = Standard deviation of poppet nozzles

discharge (l/s).

Qaver = The mean of nozzles discharge (l/s).

Numerous guidelines have been suggested, and given in the AENRI-LOFTI-

MASE Standard (dr\em\test\2002).

RESULTS AND DISCUSSION

Laboratory experiments.

Flow rate for poppet nozzle with various operating pressure.

Under low operating pressure, for PN (disc diameter 25mm), the flow rate

increased from 0.37, 0.44 and 0.53l/s with increasing pressure from 3.5, 5.2 and 6.5

kPa ( 33, 52 and 65cm ), while the coefficient of discharge decreased from 0.87, 0.80

and 0.76, respectively; Reynolds number for last values is (3395, 4262, and 4933),

respectively. But at higher operating pressure, the nozzle discharges were

approximately constant, which means that compensating the increase of operating

pressure by reducing the flow area was activated., Accordingly, nozzle discharge

values were 0.79, 0.82 and 0.836 l/s with operating pressure head 100, 300 and

340cm (10, 30 and 34 kPa), while the coefficient of discharge values were 0.69, 0.68

and 0.67, and Reynolds numbers were (6684, 8360 and 9253) respectively.


increased from, 0.35, 0.49 to 0.51 l/s with increasing operating head from 2.7, 4.9 to

6.8 kPa ( 27, 49 to 68cm ), while the coefficient of discharge values were 0.90, 0.84

and 0.78. and Reynolds number for last values were (3179, 3987 and 4592)

respectively. On other side, for disc diameter 27 mm under higher pressure, flow rate

takes a disproportionate behavior wherein; the flow rate close to constant with the

increase in operating pressure due to the flow area's decrease according to the

operational theory of poppet nozzle, which depends on control of flow area due to

operating pressure to strike a balance between them along pipe.

So, with higher operating pressure the flow rates were semi constant 0.52,

0.49 and 0.48 l/s with increasing operating head 50, 300 and 330cm (5 , 30 and 33

kPa), while the coefficient of discharge values were 0.77, 0.73 and 0.74, respectively.

Its be clear that the constant flow rate for PN (disc diameter 25mm) was

higher than constant flow rate for (disc diameter 27mm) with 38.9%, because of flow

area of PN (disc diameter 25mm) is bigger.


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increased from 0.23 0.45 l/s , with increasing operating head from 25 74 cm (2.5

7.4 kPa), while the coefficient of discharge ranged between (0.99, and 0.80) and

Reynolds number for last values ranged between (2547, and 4707) respectively. But

with the higher operating pressure head of 120 cm (12 kPa) the nozzle discharge

was completely stopped.This PN shutdown was due to closing the flow area by the

29 mm disc movement which reached a point of contact with inside body of poppet

nozzle resulting in zero flow area.

For poppet nozzles, the values of Reynolds number ranged from 2921 to

9253. This means the flow type of poppet nozzles may be transitional or turbulent

according to the equivalent diameter and water flow velocity.

Regarding the maximum value of Reynolds number which is more than 4000,

this indicates that the type of flow of poppet nozzle may be turbulence for PN (disc

diameter 25mm) because of the increase of flow area and flow rate,

Fig.(5) shows the flow rate for the three designed poppet nozzles with discs

diameter (25, 27 and 29mm) under different operating pressure, it is crystal clear

that, the flow rate increases with the decrease in disc diameter due to the increase

of flow area, according to the disproportionate relationship between flow area and

disc diameter, as shown in Fig. (7)

Fig. (5):PN flow rate for disc diameters (25, 27 and 29mm) under operating pressure

head.

Under low operating pressure head, the poppet nozzles (25, 27 and 29mm)

disc diameter flow rate were behaved a linear relationship, the poppet nozzle flow

rate increased from 0.17 to 0.44l/s with operating pressure head from 10 to 50cm,


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IRRIGATION PIPES.

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60

Operation pressure head (cm)

Flowr

ate(l/s)

1 /4 openi ng 1 /5 openi ng 3 /4 ope ni ng F ull ope ni ng

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 10 20 30 40 50 60

Operation pressure head (cm)

Flowr

ate(l/s)

PN 25mm PN 27mm PN 29mm

beside the poppet nozzle flow rate increased from 0.3 to 0.44l/s under operating

pressure head 50cm due to flow area increasing from PN 29mm to 25mm disc

diameter, the range of poppet nozzles flow is agreement with El-Sayed (1997).

Measurements of gates flow rates were shown in Table.(7) and Fig. (7)

versus operating pressure head, at many various cases of gates opening. It's clear

with operating pressure head increasing from 10 to 50cm, the flow rate increased

from 0.42 to 2 l/s, beside it can be note the flow rate increasing with gate opening

increasing at constant operating pressure head 30cm. Cited from El-Gindy et al

(2003).

Fig. (6):Gates flow rate under various operating pressure head and Poppet nozzle

flow rate under various operating pressure head.

Finally, it could be concluded that, according to the work theory of poppet

nozzle, uniformity of water flow discharged from the nozzles along irrigation gated

pipe depends on the balance between the operating pressure head and flow area of

the poppet nozzle. This balance takes place because of regulator helical

compression spring which absorbs and resists operating pressure with changing of

flow area (slope of inside nozzle body versus disc outer diameter) to realize a

balance between operating pressure and flow area. This causes a constant flow rate

along pipe with exponent of pressure head about zero in the flow equation. Jensen

(1980).


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Table.(1): Hydraulic parameters for poppet nozzle under laboratory experiments.

No. V

(m/se)

H

(m)

Q

(l/sec)

A

(m2)

d

(m)

Re Cd

25mm poppet disc diameter.

1 2.54 0.33 0.37 14E-5 0.013 3395 0.87

2 3.19 0.52 0.44 14E-5 0.013 4262 0.80

3 3.57 0.65 0.53 15E-5 0.014 4933 0.76

4 4.43 1 0.79 18E-5 0.015 6684 0.69

5 7.6 3 0.82 10E-5 0.011 8360 0.68

6 8.2 3.4 0.83 10E-5 0.011 9253 0.67


1 2.30 0.27 0.35 15E-5 0.014 3179 0.90

2 3.10 0.49 0.49 13E-5 0.013 3987 0.84

3 3.13 0.5 0.52 17E-5 0.014 4536 0.77

4 3.6 0.68 0.51 13E-5 0.013 4592 0.79

5 7.67 3 0.49 6E-5 0.009 6943 0.73

6 8.00 3.3 0.48 6E-5 0.009 7021 0.74


1 2.21 0.25 0.23 10E-5 0.012 2547 0.99

2 2.73 0.38 0.25 9E-5 0.011 2921 0.97

3 3.31 0.56 0.33 10E-5 0.011 3738 0.88

4 3.43 0.6 0.36 10E-5 0.012 3965 0.84

5 3.81 0.74 0.45 12E-5 0.012 4707 0.80

6 - 1.2 - - - - -

V : Velocity of water flow. d: diameter of flow area (m).


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IRRIGATION PIPES.

H: Operating pressure. A: Flow area (m2).

Q: Water flow (m3/s). Re: Reynolds number.

Cd: Coefficient of discharge.

Spring deflection for three disc diameter under operating pressure.

Data in Fig.(7) illustrates that the spring rate is 117, 128 and 169 gm/mm for

25, 27 and 29 disc diameter respectively. The spring rate increases with the increase

in the characteristic frontal area of the disc due to drag force increase. Whenever the

area of disc increases the operating pressure head must be increased to reach the

balance between pressure head and flow area reaching a steady flow rate.

Fig.(7): Spring deflection for three disc diameter under operating pressure head

Flow rate for poppet nozzle with various operating pressure (Field

experiments) :

Poppet nozzle (25mm disc diameter) irrigation system was selected to

evaluation, due to the wide extent of spring deflection and flow area change.

Data showed the deviation of poppet nozzles discharge from the mean

discharge along irrigation pipe at three different initial operating pressure 5, 10

and 15kPa (50, 100 and 150cm). The uniformity coefficient was high; 99, 91.7

and 90.2 for the three initial operating head respectively, which is considered

excellent as regard to the data obtained by Merriam and Keller (1978),and

good according to IRYDA (1983).

0

1

2

3

4

5

0 10 20 30 40 50 60 70

pressure head (Kpa)

Springdeflection(mm)

disc 25 mm disc 27 mm disc 29 mm


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Flow rate for poppet nozzle irrigation pipes

For operating pressure head 5kPa (50cm), the flow rates for poppet

number(1, 9, 18, 27, 36 and 45) were 0.5, 0.5, 0.5 and 0.56l/s with pressure 6, 6, 6

and 8kPa (60, 60, 60 and 80cm), while the coefficient of discharge value were 0.78,

0.78, 0.78 and 0.76 respectively. Reynolds number for last values is (4676, 4676,

4676 and 5305) respectively. Table.(2).

Table (2): Hydraulic parameters for poppet nozzle under field experiments.


number(1, 9, 18, 27, 36 and 45) were 0.5, 0.6, 0.56 and 0.6l/s with pressure head

10, 11, 11 and 14kPa (100, 110, 110 and 140cm), while the coefficient of discharge

is 0.77, 0.74, 0.75 and 0.73 respectively. Reynolds number for last values is (5310,5951, 5763 and 6338) respectively.


number were (1, 9, 18, 27, 36 and 45)0.63, 0.63, 0.66 and 0.63l/s with pressure

head 15, 18, 18 and 18kPa (150, 180, 180 and 180cm), while the coefficient of

discharge is 0.72, 0.72, 0.71 and 0.72 respectively. Reynolds number for last values

is (6590, 6900, 7061 and 6900) respectively.

The head exponent was close to zero (compensating flow) according toJensen (1980).Table(2).

Items PN1 PN2 PN3 PN4

0.5m Q(l/s) 0.5 0.5 0.5 0.56

H (m) 0.6 0.6 0.6 0.8

Cd 0.78 0.78 0.78 0.76Re 4675.5 4675.5 4675.5 5305.2

q= 0.6115h0.3939

1m Q(l/s) 0.5 0.6 0.56 0.6

H (m) 1 1.1 1.1 1.4

Cd 0.77 0.74 0.75 0.73

Re 5310.3 5950.8 5763.2 6338.3

q= 0.5262h0.45

1.5m Q(l/s) 0.63 0.63 0.66 0.63

H (m) 1.5 1.8 1.8 1.8

Cd 0.72 0.72 0.71 0.72

Re 6589.5 6900 7061 6900

q= 0.6086 h0.0851


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IRRIGATION PIPES.

Regarding the data shown, the mean discharge of poppet nozzles was 0.59,

0.69 and 0.81l/s. (2.11, 2.49 and 2.93 m3/h), which were obtained for mean operating

head pressure 8.9, 11.8 and 14.8kPa (89, 118 and 148cm), the total discharge was

92.84, 109.6 and 129 m3

/h with total dynamic head 1, 2 and 3 m, respectively for 44poppet nozzle.

MCV values (0.09, 0.12 and 0.06) which are within "good" for first and

third value with initial pressure head 50, and 150cm but for initial pressure

head 100cm MCV is medium according to AENRI-LOFTI-MASE Standard

(dr\em\test\2002), due to flow type progress to turblence phase parallel to the

increase in the operatng pressure head whenever, Reynolds number is

around 5305, 6338 and 7061 for three intial pressure respectively.

Table (3): Hydraulic parameters for poppet nozzle are under field experiments.

PN

No.

H

(m)

Q

l/sec

A

m2

d

(m)

Re Hsn

(m)

hf

(m)

At field with initial operating head (50cm)

1 0.6 0.5 15E-5 0.014 4676 0.3 0.22

11 0.6 0.5 15E-5 0.014 4676 0.3 0.44

22 0.6 0.5

15E-5 0.014 4676 0.3 0.6544 0.8 0.56 14E-5 0.013 5305 0.1 1.03


1 1 0.5 11E-5 0.012 5310 0.7 0.32

11 1.1 0.6 13E-5 0.013 5951 0.6 0.63

22 1.1 0.56 12E-5 0.012 5763 0.6 0.97

44 1.4 0.6 11E-5 0.012 6338 0.3 1.50


1 1.5 0.63 12E-5 0.012 6590 0.5 0.39

11 1.8 0.63 11E-5 0.012 6900 0.2 0.89

22 1.8 0.66 11E-5 0.012 7061 0.2 1.30

44 1.8 0.63 11E-5 0.012 6900 0.2 1.77

H: Operating pressure head Re: Reynolds number.

Q: Discharge of PN. Hsn: Super-impose head

A: Flow area hf: Friction head losses

d: Equivalent diameter of flow

area.


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0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 5 10 15 20 25 30 35 40 45

Poppet nozzle No.

Flowrate(l/s)

F low L/s & Hm = 0.5 m Flow L/s & Hm =1 m Flow L/s & Hm =1.5 m

For initial pressure head 50cm, the minimum discharge of poppet nozzle was

0.45l/s (1.62m3/h) while the maximum discharge was 0.60l/s (2.16m3/h);, for initial

pressure head 100cm the minimum discharge of poppet nozzle was 0.53l/s (1.9m3/h)

while the maximum discharge was 0.83l/s (3.0m3/h) and for initial pressure head

150cm the minimum discharge of poppet nozzle was 0.67l/s (2.4m3/h) while the

maximum discharge is 1.0l/s (3.6m3/h). Table (1).

Fig.(8): Poppet nozzle irrigation pipes during irrigation operation.

322 Flow rate for poppet nozzle under various operation pressure head.

PN irrigation pipe flow rate was increasing with operating pressure head

increasing along the pipe, but coefficient of uniformity was increased with the

operating pressure head decrease. The uniformity coefficient for poppet nozzle

irrigation pipe was 99.25, 91.7 and 90.19% with operating pressure head 50, 100 and150cm. The mean discharge of poppet nozzles was increased due to operation

pressure head increasing, so the poppet nozzle was adjustable with operating

pressure head as shown at Fig. (9).

Fig. (9): Flow rate distribution pattern for nozzle on irrigation pipes under various

Operating pressure head increases gradually along pipe due to the gradualincrease of the superimpose pressure head that overcomes the effects of the


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IRRIGATION PIPES.

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25 30 35 40 45 50

Poppet nozzle No.

PressureHead(m)

Operating pressure head (0.5m) Operating pressure head (1m)Operating pressure head (1.5m)

cumulative friction head losses as a result to flow compensating according to El-

Awady et al (2002). Fig. (10). Table(3).

Fig.(10): Operating pressure head along PN pipes.

Flow rate versus pressure, spring deflection and flow area

The disproportionate relationship between operating pressure head

and the flow area along pipes is manifest. Whatever, it's be supposed that the

operating pressure head was decreased according to friction losses and then

flow area must be increase to have a compensate flow, but at this case, thesuperimpose pressure head can overcome the effects of the cumulative

friction head losses This is due to poppet nozzle mechanism which clear with

helical spring deflection as a result to absorb operating pressure head and

resistant makes compensating to flow area with pressure increasing reaching

stability of flow rate along pipes. Flow area decrease slightly along pipes. Fig.

(11).

Fig.(11): Flow rate versus pressure, spring deflection and flow area.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 2 3

Reading number

Flowrate(l/s)&Spring

deflection

(mm)

0

0.1

0.2

0.3

0.4

0.5

0.6

Pressurehead(m)&

Flowarea

change(mm

)

Spring deflection (mm) Flow rate (l/s)

Flow area change (mm) Operating pressure head (m)

Flow area reduction


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CONCLUSIONSBased on the testing and experiments results, can be summarized as afollow:

1) There is no flow rate change with constant value (0.81l/s) with pressurehead increased from 10-34 kPa (100-340) when 25 mm diameter disc isused

2) Flow performance for discs with diameters 27mm was constant in spiteof pressure increasing as a next 6.8, 30and 33kPa (68, 300and 330cm)with lower mean flow (0.48 l/s) and poppet nozzle with diameter 29mmshut down under operating pressure 12kPa (120cm).

3) The mean discharge of poppet nozzle with initial pressure along pipesfor prssure head (50, 100 and 150cm) was 0.5, 0.56 and 0.64l/s, meancoefficient discharge was 0.77, 0.75 and 0.72 respectively,

4) Uniformity efficiency is 99, 91.7 and 90.2% for initial pressure (50, 100

and 150cm) respectively, and manufacture coefficient of variation is0.094, 0.12 and 0.065 respectively and Poppet nozzle compensating thepressure head along irrigation pipes and flow performance was regulatoralong pipes.

REFERENCES

AENRI-LOFTI-MASE, (2002), Standard for irrigation dripper testing, Code No;ir/dr/em/test/2002, Ag. Eng. Res. Inst. Irrig. Proj. Misr Soc. Ag. Eng. Stanrad:5p.

Bralts S. V.; D. M., Edwards; and Par-Wu (1987).Drip Irrigation Des -ign andevaluation based on statical uniformity concept, In a duncein Irrigation ed.D.Hillel, New York Academic Press Inc.,67-117

El-Awady, M. N.; M. T. El-Tantawy; S. S. Hassan and A. O. El-Ashhab (2002).Water flow uniformity through irrigationgated pipes. Misr J. Agric. Eng., 19(3): 677-690.

El-Gindy, A. M.; M. F. Abd el-Salam; A. A. Abdel-Aziz and E. A. El-Sahar(2003).Some engineering properties of maize plants, ears and kernels underdifferent irrigation system.,J. Agric., Sci., Mansura Univ., 28(6):4339-4360

El-Sayed, G. H. (1997). Hydraulic studies for gated pipes distributionsystem. EgyptJ. Agric. Res., 76 (1): 387-403.

Green, D. E. (1973). Land of the Underground Rain: Irrigation on the Texas HighPlains, 1910-1970, University of Texas Press, Austin, TX, 1973.http://www.livinghistoryfarm.org/farminginthe40s/water 07.html. pp1-2.

IRYDA (Instituo de Reforma Ydesarrollo Agrario ),(1983). Normas paralaredaccin de proyectos deriego Localizado.Ministerio de Agricultura, Pesca YAimenta-Cin, Madrid,Spain.

Jensen, M. E., (1980): Design and operation of farm irrigation systems. ASAEMonograph No. 3, St. Joseph, MI, p 829.

Merriam, J.L. and Keller, J.(1978). Farm irrigation systemsevaluation. A guide formanagement. UTAH Sates University, Logan, Utah, USA. Pp102-150.

Vallance, L., Venton , L, and W. Doughtie. (1951) Design of machinemembers, 3rdedition, p. 292, McGraw-Hill Book Company, Inc., New York.


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DESIGN OF AUTO-COMPENSATING NOZZLE FOR GATED IRRIGATION PIPES.

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Transcript of DESIGN OF AUTO-COMPENSATING NOZZLE FOR GATED IRRIGATION PIPES.