CENTRIFUGAL PUMPS VELOCITY DIAGRAM Vwz Vw2 AVW2" V2 a Ve Rī U2 U2 B,>90° B=90° B<90° (a) Forward-facing vanes (b) Radial vanes (c) Backward-facing vanes Discharge Radial Bearing Thrust Bearing Shaft Key Nozzle Centerline Mounted Support Bearing Housing Casing Shaft Sight Glass Suction Nozzile Impeller Mechanical Seal QUESTION 1: A centrifugal pump consists out of an impeller, diffuser and casing and is powered by 300 kW (shaft power) and rotates at 96.3 rad/s. The flow rate generated by the machine is 54.7 Kilo-litres/min. The impeller blade inlet angle and width is 23° and 180 mm respectively. The blades occupy 12% of the impeller area and the water is assumed to enter the impeller radially. Suction and delivery pipes are equal in size. Determine: 1.1. The impeller inlet (i) diameter and inlet blade velocity. (Hint - Substitution: Vi in terms of Di and Ui in terms of D; both sub into Tan of Blade inlet angle, only unknown is then solving for D?) ANS: 300 mm; 14.42 m/s If the pump has a mechanical efficiency of 80%, calculate the blade velocity at 1.2. outlet (Uo) and outlet whirl velocity Vwo. Assume the blade exit angle equal to the guide vane angle. (Hint - Substitution: Write Vwo in terms of Uo sub in Euler equation only unknown then is solve for Vwo) ANS: Vwo = 11.54 m/s; 23.1 m/s Impeller outer diameter. 1.3. ANS: 480 mm 1.4. If the flow through velocity is consistent through the pump find the fluid velocity at outlet. ANS: Vao = 13.06 m/s What is the manometric head if the suction gauge shows -30kPa and the delivery gauge shows 210 kPa? 1.5. ANS: 24.43 m

A scale model of a pump has been tested and the following results obtained. Impeller diameter (D)           110mm Power input (P)                   2.5kW  Speed (N)                           1500 r.p.m. Flow (Q)                              14.5 litres/sec Head (H)                             17m Efficiency (E)                      60%   You are to determine the speed and size of a geometrically similar pump which would deliver a flow rate of 25 litres/sec against a 22m resistance head. Determine the power input required by this pump.

For a 6.25-inch Model 4075 pump operated at 1160 rpm, if 450 GPM of water is to be delivered, what will be the estimated pump head in ft? HEAD IN FEET 30 25 0 0 0 10 O 6 ft 7.25" (184mm) 20 7.00" (178mm). 6.75" (171mm). 6.50" (165mm)] 15 6.25" (159mm). 5 O 16 ft O 20 ft O 12 ft aco® L/SEC 5 OT 10 Model 4075 FI & CI Series 15 -6-6 ⁰ dº 20 ANA 888 778 25 REQUIRED NPSH do 1160 RPM November 1, 2010 K ・dº- [M 90 do 30 8800 81 1HP(.75KW) DeJ kin do 60% 35 do 50 Curve no. 2175 Min. Imp. Dia. 6.25" Size 5 x 4 x 7.0 40 45 3HP(2.2KW), 2HP(1 5KW) 5HP(1 1KW)> CURVES BASED ON CLEAR WATER WITH SPECIFIC GRAVITY OF 1.0 L 75 150 225 300 375 450 525 600 675 FLOW IN GALLONS PER MINUTE NOWONG FEET 15 12 7 6 2 1 NPSH 758 50 5 HEAD IN METERS 45 586888 KPO 60 40 20 10 LO HEAD IN KILOPASCALS

The general energy equation is . For the picture blow, select the simplified the form of the general equation for point 1 and 4____________