Gear Pump Performance - Lab Report PDF

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Abstract In this lab experiment, we solved for the various characteristic of a gear pump. The values of the pump speed, flow rate, suction and discharge pressure were taken by running the setup. Using these already measured quantities, other properties such as pump head , hydraulic power, efficiency and the net positive suction head is measured.

Table of Contents 1) Introduction 2) Experimental Methods 3) Sample Calculations 4) Results 5) Discussions 6) Conclusions 7) References 8) Appendices

Introduction Gear pumps are another category of pumps just like centrifugal pumps. Gear pumps uses the meshing of gears to pump the fluid. The two spur gears are placed inside the pump casing. Only one gear is connected to an electric motor that rotates the gear with a constant speed also transferring motion to the driven gear. The liquid is sucked in from one side and is discharged from the other side. The amount of liquid that is discharges per revolution is called as the displacement. In a gear pump, the suction side diameter as well as the discharge side diameter are the same, the suction and the discharge velocities are also the same. Due to this fact, the pump head is easily calculated by just knowing the pressure difference between the suction and the discharge side of the pump. It can be expressed as following Pump Head H = (P2 - P1) / ℽ An important phenomenon knowns as ‘slip’ occurs in gear pumps, it is defined as the escape of the liquid from discharge side to suction side via gear pump clearances. This amount of liquid lost affects the flow rate of the pump. The brake power(BP) of the shaft gets converted to useful hydraulic power, some of this brake power is lost as friction. The hydraulic power of a gear pump is expressed as the product of the specific weight of the fluid, pump head and flow rate. Hydraulic Power HP = ℽ. H.Q The amount of power lost due to friction is calculated as, Friction power loss = BHP - HP

Another important quantity that needs to be calculated is the net positive suction head (NPSH). NPSH is defined as the sum of all forms of hydraulic head in reference to the vapor pressure head. To calculate the NPSH, the following formula is used, NPSH = (P1,abs/ ℽ) + (Vs2/2g)

An important phenomenon that has been noticed to occur in gear pumps is cavitation. It is described as the formation of air cavities in liquid. Generally, cavitation occurs when the pump operates with a low pressure on the suction side. Cavitation is destructive to impeller as it causes metal erosion.

Experimental Methods: This experiment was performed using the following setup,

The tank contains oil has the driving fluid for the gear pump. Oil travels from the tank to the suction valve which controls the amount of oil going into the gear pump. The pressure gauge next to the suction valve measures the magnitude of the suction pressure. After the suction pressure gauge is the gear pump, the oil passes through it and then the discharge pressure gauge measures the discharge pressure. After the oil has been discharged from the gear pump it travels through a control valve, filter, thermometer and a heat exchanger, finally making its way to the storage tank. And this cycle can be repeated as many times as needed and for different pump speeds. The values that are documented from this setup are pump speed, flow rate, BHP , suction and discharge pressure.

Results: Speed = 1300 rpm Part A P1(in Hg)

P1(Pa)

P2(psi)

P2(Pa)

Q(GPM)

Q(m3/s)

-14.5

-48983.9

15

104160.2

1.8

1.14E-04

-14.5

-48983.9

25

173600.3

1.5

9.48E-05

-14.5

-48983.9

35

243040.5

1.7

1.07E-04

-14

-47294.8

45

312480.6

1.6

1.01E-04

-14

-47294.8

55

381920.8

1.55

9.79E-05

-13.5

-45605.7

65

451360.9

1.5

9.48E-05

-13.5

-45605.7

72

499969

1.5

9.48E-05

Head H(m)

HP(watts)

Fric Pow Loss

Efficiency%

BHP, Vs(m/s) Watts 2.34E08 340 1.95E08 337 2.21E08 342 2.08E08 346 2.01E08 352 1.95E08 354 1.95E08 356

NPSH

Vol Ef

17.7578975

17.41249

322.5875149

5.12131915

6.566683

2.25

25.8098617

21.08986

315.9101426

6.25811793

6.566683

1.88

33.8618258

31.35855

310.641448

9.16916725

6.566683

2.13

41.7179296

36.3613

309.6386971

10.5090471

6.762544

2.00

49.7698938

42.02378

309.9762195

11.938574

6.762544

1.94

57.6259975

47.08759

306.9124144

13.3015779

6.958404

1.88

63.2623724

51.6932

304.3067972

14.5205626

6.958404

1.88

Speed = 1500 rpm Part A P1(in Hg)

P1(Pa)

P2(psi)

-15.5

55740. 3 55740. 3 54051. 2 54051. 2 52362. 1 52362. 1

-15

-50673

-16.5

-16.5

-16

-16

-15.5

Hp (watt)

P2(Pa)

Q(GPM )

Q(m3/s )

Vs (m/s)

BHP,watts

H (m)

15

104160. 2

1.9

1.20E04

0.95

336

18.5413 4

25

173600. 3

1.5

9.48E05

0.75

341

26.5933

35

243040. 5

1.8

1.14E04

0.90

348

34.4494 1

45

312480. 6

1.9

1.20E04

0.95

356

42.5013 7

55

381920. 8

1.8

1.14E04

0.90

362

50.3574 7

65

451360. 9

2

1.00

371

75

520801

1.65

0.82

381

Friction P Loss

1.26E04 1.04E04

Efficiency%

NPSH

58.4094 4 66.2655 4

Vol Ef

19.19

316.81

5.7115256

5.829038

2.38

21.73

319.27

6.3724417

5.811785

1.88

33.78

314.22

9.7067025

6.020205

2.25

43.99

312.01

12.356721

6.024899

2.38

49.38

312.62

13.640321

6.216065

2.25

63.64

307.36

17.152832

6.225706

2.50

59.56

321.44

15.63304

6.405361

2.06

Speed 1700 rpm Part A P1(in Hg)

-18.5

-18

-18

-18

-17.5

-17

-17

P1(Pa) 62496. 7 60807. 6 60807. 6 60807. 6 59118. 5 57429. 4 57429. 4

Hp (watt)

P2(psi)

P2(Pa)

Q(GPM )

Q(m3/s)

BHP(watts )

H (m)

15

104160. 2

1.7

0.00010 7

350

19.3247 8

25

173600. 3

2.3

0.00014 5

359

27.1808 8

35

243040. 5

2

0.00012 6

367

35.2328 5

45

312480. 6

2.1

0.00013 3

376

43.2848 1

55

381920. 8

1.9

0.00012

385

51.1409 2

65

451360. 9

2.1

0.00013 3

395

58.9970 2

73

506913

1.8

0.00011 4

402

65.4385 9

FPL(watt)

Efficiency%

Vol Ef

17.89617

332.1038

5.11319267

2.13

34.05557

324.9444

9.48623062

2.88

38.38614

328.6139

10.4594391

2.50

49.51668

326.4833

13.1693306

2.63

52.93206

332.0679

13.7485876

2.38

67.49103

327.509

17.0863376

2.63

64.16573

337.8343

15.961625

2.25

Speed = 1300 rpm Part B P1(in Hg)

-18 -20

-22

-24 -25

-28

P1(Pa) 60807. 6 -67564 74320. 4 81076. 8 -84455 94589. 6

P2(psi)

Vs(m/s)

30

0.84812 5 0.84812 5

30

0.89801 5

30

Q(GPM )

Q(m3/s)

NPSH (m)

1.7

0.00010 7 0.00010 7

308

5.16820 5 4.38476 3

1.8

0.00011 4

310

3.60576 2

1.7

30

0.89801 5 0.84812 5

1.7

0.00011 4 0.00010 7

30

0.89801 5

1.8

0.00011 4

30

BHP(watts )

1.8

306

311 313

2.82232 2.42615 9

312

1.25543 7

Speed = 1500 rpm Part B P1(in Hg)

-18 -20 -22

P1(Pa) 60807. 6 -67564 74320.

Vs(m3/s) P2(psi) 0.94790 4 0.89801 5 0.94790 4

Q(GPM )

30

1.9

30 30

1.8 1.9

Q(m3/s)

0.00012 0.00011 4 0.00012

BHP(watts )

334 335 336

NPSH (m) 5.17733 8 4.38920 3 3.61045 5

-24

-26

-28

4 81076. 8 87833. 2 94589. 6

Graphs: Capacity vs Head

0.94790 4

30

1.9

0.00012

339

2.82701 4

0.89801 5

30

1.8

0.00011 4

340

2.03887 8

0.89801 5

30

1.8

0.00011 4

350

1.25543 7

Capacity vs Head 1.60E-04 1.40E-04

Capacity Q,(m3/s)

1.20E-04 1300 rpm Polynomial (1300 rpm) 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm)

1.00E-04 8.00E-05 6.00E-05 4.00E-05 2.00E-05 0.00E+00 10

20

30

40

Pump Head, Hp(m)

Hydraulic Power vs Head

50

60

70

Hydraulic Power vs Head 80

Hydraulic Power, Hp(watt)

70 60 1300 rpm Polynomial (1300 rpm) 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm)

50 40 30 20 10 0 10

20

30

40

Pump Head, H(m)

Friction Power Loss vs Pump Head

50

60

70

Friction Power Loss vs Head 350

Friction Power Loss , (watt)

340 330 1300 rpm Polynomial (1300 rpm) 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm)

320 310 300 290 280 10

20

30

40

Pump Head H(m)

Brake Horse Power vs Pump Head

50

60

70

BHP vs Head 420

400

BHP(watt)

380

1300 rpm 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm) Polynomial (1700 rpm)

360

340

320

300 10

20

30

40

Pump Head H (m)

Efficiency vs Pump Head

50

60

70

Efficiency vs Head 20 18 16 14 1500 rpm Polynomial (1500 rpm) 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm)

Efficiency

12 10 8 6 4 2 0 10

20

30

40

50

Pump Head H(m)

Volumetric Efficiency vs Pump Head

60

70

Vol Efficiency vs Pump Head 3.50 3.00

Volumetric Efficiency

2.50 1300 rpm Polynomial (1300 rpm) 1500 rpm Polynomial (1500 rpm) 1700 rpm Polynomial (1700 rpm)

2.00 1.50 1.00 0.50 0.00 10

20

30

40

Pump Head H (m)

Capacity vs NPSH

50

60

70

Capacity vs NPSH 0

Capacity Q (m3/s)

0

0

1300 rpm Polynomial (1300 rpm) 1500 rpm Polynomial (1500 rpm)

0

0

0 1

1.5

2

2.5

3

3.5

NPSH (m)

4

4.5

5

5.5...