TITLE: FLUID MACHINERY (CENTRIFUGAL PUMP)
1.0 OBJECTIVE
The objective of this experiment is to obtain the performance characteristics for a variable speed centrifugal pump operating at 3 different impeller speeds. The characteristics include:
• Pressure (head) jump
• Power requirement
• Flow rate influence
• Pump speed influence
2.0 INTRODUCTION
Centrifugal pump is a machine that imparts energy to fluid. This energy infusion can cause a liquid to flow, rise to a higher level, or both. It is a member of a family known as rotary machines and consists of two basic parts:
a) The rotary element or impeller
b) The stationary element or casing (volute)
The figure 2.1 is a cross section of a centrifugal pump and shows two
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It is filled with liquid and the impeller is rotated by motor. Rotation imparts energy to the liquid causing to exit the impeller’s vanes at greater velocity than it possessed when it entered. This outward flow reduces the pressure at the impeller eye, allowing more liquid to enter. The liquid that exits the impeller is collected in the casing (volute) where its velocity is converted to pressure before it leaves the pump’s discharge. The application of centrifugal pumps ranges from domestic machines such as vacuum cleaner and water pumps to industrial machines, petrochemical pumps and coal preparation plant uses. Despite the common use, the actual performance of this kind of pump cannot be predicted solely based on theoretical ideas due to the intricacy of fluid flow in the pump. Pump performance curves comprising information of head rise, efficiency and capacity are experimentally determined by conducting …show more content…
Output
From 90o Vee Notch Calibration graph,
At height of 64mm,
Volume flow rate, Q = 87.5 L/min ; (1m3 = 1000L) Q = 1.46x10-3 m3/s
Inlet Pressure, P1 = 0 mH2O x 9.864k ; (1 mH2O = 9.864 kN/m2) = 0 N/m2
Discharge pressure, P2 = 18 psi x 6894.757 N/m2 ; (1 psi = 6894.757 N/m2) P2 = 124.11 kN/m2
Water Head, h = (P2-P1)/ρg h = h = 12.65 m
Power output, P = P = 1000 x 9.81 x (1.46x10-3) x 12.65 P = 181.18 W
Efficiency, η = η = η = 37.75 %
TEST 3 (100%)
Input
At pump speed, N = 2945 rpm ω = 2πN/60 ω = 308.40 rad/s
Shaft Power, P = ωT = 308.40 x 3.5 = 1.08 kW
Shaft Power, Hp (BHP) = P / 746 ; (1hp = 746W) = 1.08k / 746 = 1.45 Hp
Output
From 90o Vee Notch Calibration graph,
At height of 72mm,
Volume flow rate, Q = 117.5 L/min ; (1m3 = 1000L) Q = 1.96x10-3 m3/s
Inlet Pressure, P1 = -0.4 mH2O x 9.864k ; (1 mH2O = 9.864 kN/m2) = -3945.6 N/m2
Discharge pressure, P2 = 33 psi x 6894.757 N/m2 ; (1 psi = 6894.757 N/m2) P2 = 227.53 kN/m2
Water Head, h = (P2-P1)/ρg h = h = 23.60 m
Power output, P = P = 1000 x 9.81 x (1.96x10-3)x 23.60 P = 453.77 W
Efficiency, η