Centrifugal Pump2

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Title of experiment: CENTRIFUGAL PUMP

INTRODUCTION Centrifugal pump consist of an impeller rotating within a spiral casing. The fluid enters the pump axially through the suction pipe via the eye of the impeller, it is discharge from impeller around the entire circumference both into the ring stationary diffuser vanes (and through them into the volute casing) or directly into the casing. The casing collect the fluid, decelerates it thus converting some of the kinetic energy into pressure energy and finally discharges the fluid through the delivery flange. OBJECTIVE The objective of this experiment are to obtain the characteristics performance of the centrifugal pump Student should be able to understand the principles and application of centrifugal pump THEORY Assuming steady flow, pump basically increase the Bernoulli head of flow between point 1 (suction) and point 2 (delivery), neglecting viscous work and heat transfer, this donate by head, H. The head of a pump is the mechanical work transfer red by the pump to the medium pumped under the local gravity conditions. The head, H tells us the increment of mechanical energy, E between inlet and outlet. Head could be defined as: H = (ZD- Zs) + (PD Ps) + (VD2 Vs2) g Where ZD Zs : Difference in the height of the inlet and outlet cross section on the pump. 2g

: Difference in the pressure head of the medium pumped between inlet and outlet

: Difference in the speed of the medium pumped between inlet and outlet.

Usually VD and Vs are about the same ZD Zs is no more than a meter or so. Therefore, the net pump head, H equals to change in pressure head: H = PD Ps (2) g

The power required to drive the pump is brake power, Pmech Pmech = T. = T 2N 60 Where T = torque (Nm) (3)

Hydraulic power output, Phyr: Phydr = gQH (4)

The pump efficiency, is given by the ratio between the power output by a pump and the power drawn from the shaft, ie = P hydr P mech .. (5)

Pump Characteristic Curves P (and thus the efficiency ) , as well as the parameter NSPH req depend on the flow rate Q. The relationship between these of the performance data is displayed in characteristic curves. The operating behavior of each centrifugal pump is characteristic by these characteristic curves. System characteristic curve The system characteristic curve is given by the pressure losses in the pipes at a specific flow rate. For increasing speed (= flow rate), these exist points in a graph of head H against flow rate Q using which the characteristic curve can be drawn. The operating point of a pump is positioned, as per figure 1, where the head of the pump and the system are the same that is at the point where the system characteristic curve and pump characteristic curves cross.

Centrifugal Pump One of the most common radial-flow turbo machines is the centrifugal pump. This type of pump has two main components: an impeller attached to a rotating shaft, and a stationary casing, housing, or volute enclosing the impeller. The impeller consists of a number of blades 1 usually curved 2, also sometimes called vanes, arranged in a regular pattern around the shaft. A sketch showing the essential features of a centrifugal pump is shown in figure below. As the impeller rotates, fluid is sucked in through the eye of the casing and flows radially outward. Energy is 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. For the simplest type of centrifugal pump, the fluid discharges directly into a volute-shaped casing. The casing shape is designed to reduce the velocity as the fluid leaves the impeller, and this decrease in kinetic energy is converted into an increase in pressure. The volute-shaped casing, with its increasing area in the direction of flow, is used to produce an essentially uniform velocity distribution as the fluid moves around the casing into the discharge opening. For large centrifugal pumps, a different design is often used in which diffuser guide vanes surround the impeller. The diffuser vanes decelerate the flow as the fluid is directed into the pump casing. This type of centrifugal pump is referred to as a diffuser pump.

EQUIPMENT Equipment used for this experiment are: 1. Basic module water pumps, (GUNT Hamburg), Germany. 2. Self Priming centrifugal pump. 3. Drive and Brake unit. 4. Tachometer Procedure Series of measurement at various speed must be performed on the pumps. The pump must be running at constant speed and the system must be more or less at the steady state. Steps to run the experiment are: 1. Turn On all main switches and check to ensure the apparatus is ready. 2. The belt guard (1) must be in place and the direction of the rotation indicator in clock wise direction is illuminated. 3. The pump can only start with back pressure. The ball valve 2 for flow rate regulation must be closed. 4. Move the potentiometer 3 to start the motor. Fully open the ball valve. 5. Set the speed to 1000 rpm and observe whether water is pumped back to the tank 4 6. Let the pump runs for some time and reach its operating temperature.

Experiment At constant Speed, 2900 rpm 7. Ensure the ball valve is fully opened. 8. Increase the speed in 2900 rpm by turning the potentiometer. 9. For this experiment, take the flow rate reading from magnetic inductive only 5 10. Flow rate , P1, P2 and torque are recorded 11. A little the ball valve are closed to reduce the flow rate.

Experiment At Various Speed. 12. The speed is set to 1500 rpm with the ball valve fully opened.13. Flow rate P1, P2 and torque are record. 14. The speed is increase into 1100 rpm ( 100 rpm increment)

15. Repeat from 13 until the maximum speed 3000 rpm.

RESULT Calculate and fill up Table 1 and 2 Speed = 2900 rpm N o. 1 2 3 4 5 6 7 8 9 10 11 12 13 No. Flow rate Q (l/s) 2.884 2.883 2.880 2.869 2.871 2.856 2.816 2.757 2.607 1.375 1.172 1.149 0.287 Suction Delivery Torque Head Mechanical Pressure Pressure T H Power P1 (Bar) P2 (bar) (Nm) (m) Pmech (W) -0.89 0.37 2.72 13.01 829.45 -0.89 0.37 2.70 13.01 823.35 -0.89 0.38 2.68 13.11 817.25 -0.89 0.39 2.66 13.22 811.15 -0.88 0.40 2.65 13.22 808.10 -0.88 0.43 2.65 13.53 808.10 -0.85 0.49 2.63 13.66 802.00 -0.82 0.56 2.59 14.07 789.80 -0.74 0.67 2.56 14.37 780.66 -0.63 0.85 2.50 15.09 762.36 -0.54 0.97 2.45 15.39 747.11 -0.30 1.35 2.14 16.82 652.58 -0.07 1.78 1.58 18.86 481.81 Flowrate Q (l/s) 1.486 Suction Pressure P1 (Bar) -0.30 Hydraulic Power Phydr (W) 368.08 367.95 370.65 372.08 372.33 379.07 377.36 380.54 367.51 203.55 176.94 189.59 53.10 Efficiency 0.44 0.45 0.45 0.46 0.46 0.47 0.47 0.48 0.47 0.27 0.24 0.29 0.11 Head H (m) 3.72

1

Mechanical Speed N (rpm) 1500

Delivery Pressure P2, (bar) 0.06

2 1600 1.592 -0.33 3 1700 1.700 -0.36 4 1800 1.800 -0.40 5 1900 1.902 -0.44 6 2000 2.006 -0.48 7 2100 2.100 -0.52 8 2200 2.220 -0.57 9 2300 2.330 -0.61 10 2400 2.430 -0.66 11 2500 2.540 -0.71 12 2600 2.640 -0.76 13 2700 2.750 -0.81 14 2800 2.842 -0.86 15 2900 2.962 -0.90 CALCULATION: Experiment At Constant Speed, 2900 rpm Calculation of Head H (m) 1 bar = 1.013 x 105 N/m2 H = PD - Ps g water = 1000 kg/m3

0.07 0.09 0.11 0.13 0.15 0.17 0.19 0.22 0.24 0.27 0.30 0.33 0.37 0.40

4.13 4.65 5.27 5.89 6.50 7.12 7.85 8.57 9.29 10.12 10.95 11.77 12.70 13.42

gravity = 9.81 ms-2

1 ).

H = 0.3748 x 105 + 0.9016 x 105 9810

= 13.01 m

2 ).

H = 0.3748 x 105 + 0.9016 x 105 9810

= 13.01 m

3 ).

H = 0.3849 x 105 + 0.9016 x 105 9810

= 13.11 m

4 ).

H = 0.3951 x 105 + 0.9016 x 105 9810

= 13.22 m

5 ).

H = 0.4052 x 105 + 0.8914 x 105 9810

= 13.22 m

6 ).

H = 0.4356 x 105 + 0.8914 x 105 9810

= 13.53 m

* The others calculation from data number 7 to 13 is same like above Calculation of mechanical power Mechanical Power , P mech (W) = T. = T (2 N ) 60 Where T = torque (Nm) N = Revolution/ minute (rpm)

1 ). P mech = (2.72 x 2 x 2912) / 60 = 829.45 W 2 ). P mech = (2.70 x 2 x 2912) / 60 = 823.35 W 3 ). P mech = (2.68 x 2 x 2912) / 60 = 817.25 W 4 ). P mech = (2.66 x 2 x 2912) / 60 = 811.15 W 5 ). P mech = (2.65 x 2 x 2912) / 60 = 808.10 W 6 ). P mech = (2.65 x 2 x 2912) / 60 = 808.10 W 7 ). P mech = (2.63 x 2 x 2912) / 60 = 802.00 W 8 ). P mech = (2.59 x 2 x 2912) / 60 = 789.80 W 9 ). P mech = (2.56 x 2 x 2912) / 60 = 780.66 W 10 ). P mech = (2.50 x 2 x 2912) / 60 = 762.36 W

11 ). P mech = (2.45 x 2 x 2912) / 60 = 747.11 W 12 ). P mech = (2.14 x 2 x 2912) / 60 = 652.58 W 13 ). P mech = (1.58 x 2 x 2912) / 60 = 481.81 W

Calculation to get hydraulic power Hydraulic Power ,Phydr (W) = gQH Where = density g = gravity Q = flow rate H = head water = 1000 kg/m3 g = 9.81 ms-2 1 m3 =1000 liter

1 ). 2 ).

Phydr = 1000 x 9.81 x 2.884 x 10-3 x 13.01 Phydr = 1000 x 9.81 x 2.883 x 10-3 x 13.01 Phydr = 1000 x 9.81 x 2.882 x 10-3 x 13.11 Phydr = 1000 x 9.81 x 2.869 x 10-3 x 13.22 Phydr = 1000 x 9.81 x 2.871 x 10-3 x 13.22 Phydr = 1000 x 9.81 x 2.856 x 10-3 x 13.53 Phydr = 1000 x 9.81 x 2.816 x 10-3 x 13.66 Phydr = 1000 x 9.81 x 2.757 x 10-3 x 14.07 Phydr = 1000 x 9.81 x 2.607 x 10-3 x 14.37

= 368.08 W = 367.95 W

3 ). 4 ). 5 ). 6 ). 7 ). 8 ). 9 ).

= 370.65 W = 372.08 W = 372.33 W = 379.07 W = 377.36 W = 380.54 W = 367.51 W

10). 11). 12). 13).

Phydr = 1000 x 9.81 x 1.375 x 10-3 x 15.09 Phydr = 1000 x 9.81 x 1.172 x 10-3 x 15.39 Phydr = 1000 x 9.81 x 1.149 x 10-3 x 16.82 Phydr = 1000 x 9.81 x 0.287 x 10-3 x 18.86

= 203.55 W = 176.94 W = 189.59 W = 53.10 W

Calculation of pump efficiency Pump Efficiency, = P hydr / P mech

1 ). 2 ). 3 ). 4 ). 5 ). 6 ). 7 ). 8 ). 9 ). 10). 11). 12).

= 340.12 / 811.15 = 0.44 = 344.06 /