ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 1

Gear Pump

Aim

To determine the characteristics of Gear Pump and to plot the following performance

characteristics:- 1. Head Vs Discharge.

2. Pump efficiency Vs Discharge.

To check if the ratio of discharge Vs RPM is a constant.

Apparatus

Sump tank

Overhead tank

Gear pump mesh attached to DC motor Thyristor controlled DC drive to vary the RPM of motor: Single Phase, 220 Volts, 1KW

Vacuum gauge

Pressure gauge Oil used: SAE 20W/40 (30 liters)

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 2

Theory

The pump is defined as a device which transfers mechanical energy supplied to it to the

fluid in the line. Here we are going to study characteristics of a gear pump.

There are two main variations; external gear pumps which use two external spur gears, and internal gear pumps which use an external and an internal spur gear. Gear pumps are positive

displacement (or fixed displacement), meaning they pump a constant amount of fluid for each

revolution. Some gear pumps are designed to function as either a motor or a pump.

External gear pump

Internal Gear Pump

As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump,

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 3

where the meshing of the gears displaces the fluid. The mechanical clearances are small— in the

order of 10 μm. The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards.

Gear pump has a fixed discharge per rotation. It entraps fluid from one side and pushes it

to the other side. The volume of fluid trapped each time is constant. This rigid structural property

makes it ideal to pump even the most viscous fluids. Discharge Vs RPM is constant for a gear pump even for fluids with different viscosity.

Procedure

1. Fill Sump tank .with oil (SAE 40) and ensure that no foreign particles are there.

2. Open Flow Control Valve given on the discharge and suction line.

3. Set the RPM of motor with the help of variac.

4. Now switch on the Main Power Supply (220 V AC, 50 Hz) and switch on the Pump. 5. Make sure that control valves are open.

6. Record discharge pressure by means of Pressure Gauge, provided on discharge

7. line. 8. Record suction pressure by means of Vacuum Gauge, provided at suction of the

9. pump.

10. Record the power consumption by means of Energy meter and stop watch.

11. Measure the discharged by using measuring tank and Stop Watch. 12. Repeat the same procedure for different RMP of pump and calculate discharge.

13. Closing Procedure:

14. Switch OFF the pump first. 15. Switch OFF Power Supply to Panel (MCB).

Notations

A = Area of measuring tank, m2 EMC = energy meter constant

N = Speed of Pump, RPM.

H = Total Head, m P = Pulses of energy meter

Q = Discharge, m3/s

R = Rise of height of fluid in measuring tank, m

t = Time taken by R, sec t’ = Time tank by P, sec

ƞ0= Overall efficiency.

ƞ𝑝 = Pump efficiency.

ρ= Density of fluid, Kg/ m3

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 4

Formulae

Electrical Power

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑃𝑜𝑤𝑒𝑟 𝐻𝑃 =𝑃 ∗ 3600 ∗ 1000

𝑡𝑝 ∗ 𝐸𝑀𝐶 ∗ 746

Shaft Power

𝑆ℎ𝑎𝑓𝑡𝑃𝑜𝑤𝑒𝑟 𝐻𝑃 = ƞ𝑚𝑜𝑡𝑜𝑟 ∗ 𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑃𝑜𝑤𝑒𝑟(𝐻𝑃)

ƞ𝑚𝑜𝑡𝑜𝑟 𝑖𝑠𝑎𝑠𝑠𝑢𝑚𝑒𝑑𝑡𝑜𝑏𝑒 0.8

Discharge

𝑄 =𝐴 ∗ 𝑅

𝑡

Total Head

𝐻 = 11.5 ∗ 𝑃𝑑 +𝑃𝑠

760 + 0.8

Pump Power

𝑃𝑢𝑚𝑝𝑃𝑜𝑤𝑒𝑟 𝐻𝑃 =𝜌 ∗ 𝑄 ∗ 𝐻

75

Overall Efficiency

ƞ0 =𝑃𝑢𝑚𝑝𝑃𝑜𝑤𝑒𝑟(𝐻𝑃)

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑃𝑜𝑤𝑒𝑟(𝐻𝑃)∗ 100

Pump Efficiency

ƞ𝑝 =𝑃𝑢𝑚𝑝𝑃𝑜𝑤𝑒𝑟(𝐻𝑃)

𝑆ℎ𝑎𝑓𝑡𝑃𝑜𝑤𝑒𝑟(𝐻𝑃)∗ 100

Data

Area of measuring tank (A) = 0.0625 m2

Energy meter constant (EMC) = 6400 Pulses/ kW hr

Density of oil, ρ= 868 Kg / m3

Motor efficiency = 0.8

Pump : Speed 1500 RPM (max.) Capacity 1 HP

Head 5 kg/cm2 (max.)

Pressure Gauge : Bourdon type.

Medium Flow : Clear Oil

Drive : 1 HP DC Motor with Thyristor controlled DC

Drive for variable Speed (Standard Make)

Sump tank : Made Of Stainless Steel, Capacity 30 Ltrs. (max.)

Flow Measurement : Using Measuring Tank with Piezometer (StandardMake) capacity

20 liters. (Max.)

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 5

Observation Table

Sr.No RPM Height(cm) Pulse/20 sec Gauge Pressure(mm Hg) Vacuum Pressure(mm Hg)

1 0417 06.5 05 0.35 30

2 0525 08.0 07 0.55 30

3 0618 09.0 09 0.75 45

4 0740 11.2 10 1.00 45

5 0800 11.5 12 1.15 45

6 0930 13.5 14 1.50 50

7 1014 14.4 16 1.80 50

8 1150 15.7 18 2.25 55

Calculation Table

S.No Elect.pow(HP) Shaft.pow(HP) Discharge(m3/s) Total head(m) Pump.pow(HP) ƞ

𝑝 ƞ

𝑜

1 0.188505 0.150804 0.000203 5.278947 0.01241 6.583328 8.229159

2 0.263908 0.211126 0.00025 7.578947 0.021928 8.309131 10.38641

3 0.33931 0.271448 0.000281 10.10592 0.032895 9.694618 12.11827

4 0.377011 0.301609 0.00035 12.98092 0.052581 13.94692 17.43365

5 0.452413 0.36193 0.000359 14.70592 0.061164 13.51959 16.89949

6 0.527815 0.422252 0.000422 18.80658 0.091823 17.39684 21.74605

7 0.603217 0.482574 0.00045 22.25658 0.115912 19.21568 24.0196

8 0.678619 0.542895 0.000491 27.50724 0.156191 23.01595 28.76994

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 6

Characteristic Graphs

0

5

10

15

20

25

30

0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006

Tota

l He

ad(m

)

Discharge(m3/s)

Head Vs Discharge

0

5

10

15

20

25

30

35

0 2 4 6 8 10

Pu

mp

eff

icie

ncy

Discharge(m3/s)

Pump Efficiency Vs Discharge

0

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0 200 400 600 800 1000 1200 1400

Dis

char

ge(m

3/s

)

RPM

Discharge Vs RPM

ME-313, IIT Gandhinagar, Dept. of Mechanical Engineering Page 7

Conclusion

The characteristics of gear pump were studied.

The characteristic graphs were plotted and observed that: Head increases with Discharge

Pump efficiency increases with increase in Discharge.

Discharge Vs RPM graph is fairly a strait line.

Suggestion

Experiments were to be conducted with different viscosity fluids to check if ratio of discharge to RPM is

constant.