1. INTRODUCTIONCentrifugal pump is the pump that has two main components: the impeller attached to a rotating shaft, and a stationary housing enclosing the impeller. Energy added to the fluid by the rotating blades, and both pressure and absolute velocity are increased as the fluid flows from the eye to the periphery of the blades. The kinetic energy is converted into further increase in pressure as the fluids flows from the impeller into the casing enclosing the impeller

2. OBJECTIVEThe main objective of the experiment is to obtain performance characteristics head hp, efficiency, η and brake horsepower, bhp, for a variable speed centrifugal pump operating at 3 different impeller speeds.

3. APPARATUS

Water flow bench and centrifugal pump, instrumentation panel, centrifugal pump, digital tachometer.

4. THEORY

The pump head rise,

hp = (p2 - p )/ρġ + (z 2 – z) + (V2² – V ²)/2ġ hp = (p2 - p )/ρġ

The power, Pf = ρġQha

The pump overall efficiency, η = Pf// Wshaft

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5. TABULATION OF DATA AND CALCULATION

Test 1 – Pump speed, N1 = 1421 rpm at 50% speed

NoWater height, h

(mm)Capacity, Q

(l/min)Inlet Pressure

P1Discharge

Pressure, P2Torque, T

(N.m)1 0 0 0.05 8 0.52 58 70 0 7 13 64 88 -0.05 6 1.14 69 105 -0.1 5 1.25 72 119 -0.2 4 1.26 75 130 -0.3 3 1.27 78 145 -0.5 2 1.38 78 145 -0.5 1 1.3

a) Pump head,

Hp = (p2 - p )/ρġ Hp = (8 – 0.05)/ (1000*9.81) = 0.810*10ˉ ³m

b) The power, Pf = ρġQhp

Pf = 1000*9.81*0*0.810*10ˉ ³ = 0

c) The pump overall efficiency,

η = Pf// Wshaft η = 0/ 148.81; Wshaft = 2πN/60 = 148.81 = 0

Q Hp Pf η0 0.810*10ˉ ³ 0 0

70 0.714*10ˉ ³ 490.3 3.29

88 0.714*10ˉ ³ 532.64 3.58

105 0.520*10ˉ ³ 535.63 3.61

119 0.428*10ˉ ³ 499.64 3.36

130 0.336*10ˉ ³ 428.5 2.88

145 0.255*10ˉ ³ 362.72 2.44

145 0.153*10ˉ ³ 217.63 1.46

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Test 2 – Pump speed, N2 = 2212 rpm at 75% speed

NoWater height, h

(mm)Capacity, Q

(l/min)Inlet Pressure

P1Discharge Pressure,

P2Torque, T

(N.m)1 0 0 0.1 19 12 68 102 0 17 23 75 130 -0.3 15 2.34 80 154 -0.6 13 2.55 84 173 -1 11 2.66 87 188 -1.1 9 2.77 90 205 -1.5 7 2.88 92 215 -1.8 5 2.99 94 228 -2 3 3

a) Pump head,

Hp = (p2 - p )/ρġ Hp = (19– 0.1)/ (1000*9.81)

= 0.810*10ˉ ²m

b) The power, Pf = ρġQhp

Pf = 1000*9.81*0*0.193*10ˉ ² = 0

c) The pump overall efficiency, η = Pf// Wshaft

η = 0/ 231.64; Wshaft = 2π (2212)/60 = 231.64 = 0

Q Hp Pf η0 0.193*10ˉ ³ 0 0

102 0.173*10ˉ ³ 1731.07 7.47

130 0.156*10ˉ ³ 1989.47 8.59

154 0.139*10ˉ ³ 2099.93 9.06

173 0.122*10ˉ ³ 2070.5 8.94

188 0.103*10ˉ ³ 1899.61 8.2

205 0.0.87*10ˉ ³ 1749.61 7.55

215 0.069*10ˉ ³ 1455.31 6.28

228 0.051*10ˉ ³ 1140.71 4.92

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Test 3 – Pump speed, N3 = 3026 rpm at 100% speed

NoWater height, h

(mm)Capacity, Q

(l/min)Inlet Pressure

P1Discharge

Pressure, P2Torque, T

(N.m)1 0 0 0.1 36 1.62 72 118 -0.1 33 3.33 83 169 -0.8 29 3.94 890 205 -1.4 25 4.25 95 235 -2 21 4.56 99 260 -2.4 17 4.77 102 280 -2.8 13 4.88 104 295 -3 9 4.99 106 310 -3.3 5 5

a) Pump head, Hp = (p2 - p )/ρġ

Hp = (36– 0.1)/ (1000*9.81) = 0.3640*10ˉ ²m

b) The power, f = ρġQhp

f = 1000*9.81*0*0.364*10ˉ ² =0

c) The pump overall efficiency,

η = Pf// Wshaft

η = 0/ 316.88; Wshaft = 2π (3026)/60 = 316. 88 =0

Q Hp Pf η0 0.364*10ˉ ² 0 0

118 0.337*10ˉ ² 3901.04 12.31

169 0.304*10ˉ ² 5039.99 15.91

205 0.269*10ˉ ² 5409.72 17.07

235 0.234*10ˉ ² 5394.52 17.02

260 0.198*10ˉ ² 5050.19 15.94

280 0.161*10ˉ ² 4422.35 13.96

295 0.122*10ˉ ² 3530.62 11.14

310 0.085*10ˉ ² 2584.94 8.16

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6. DISCUSSSION

From the experiment that we have done, we can see that the speed of 100% of the pump give the best maximum efficiency which is 17.07%. For the speed of 50% and 75% give the maximum efficiency at 3.61% and 9.06% respectively. For the brake horse power and efficiency graphs, it shown that the similarity represents each other. Both graph shows a steady increase for the value of BHP and efficiency before it reach the highest value and fall rapidly afterwards. For the head pump graph, it shown the graph is decrease for every test. There has an error during the experiment that effects the calculation for the experiment value, error on reading the data.

7. CONCLUSION

From the experiment, we can conclude that the speed of 100% of the pump give the best maximum efficiency which is 17.07%. From the graph above also, we can see the similarity of the actual brake horse power and the experiment graph of brake horse power. The only different is where from the reference lab sheet, it don’t started at point zero while from the experiment we shows that the graph started at zero point. This is because from our calculation we obtain the value of P f = 0 every time we started the experiment as the value of the h = 0, the value of Q is equal to 0.

Pf = ρġQhp = ρġ (0) hp = 0

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