FluidMechWhite5eCh11

# FluidMechWhite5eCh11 - Chapter 11 Turbomachinery 11.1...

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Chapter 11 Turbomachinery 11.1 Describe the geometry and operation of a human peristaltic PDP which is cher- ished by every romantic person on earth. How do the two ventricles differ? Solution: Clearly we are speaking of the human heart , driven periodically by travelling compression of the heart walls. One ventricle serves the brain and the rest of one’s extremities, while the other ventricle serves the lungs and promotes oxygenation of the blood. Ans. 11.2 What would be the technical classification of the following turbomachines: (a) a household fan = an axial flow fan . Ans. (a) (b) a windmill = an axial flow turbine . Ans. (b) (c) an aircraft propeller = an axial flow fan . Ans . (c) (d) a fuel pump in a car = a positive displacement pump (PDP) . Ans. (d) (e) an eductor = a liquid-jet-pump (special purpose). Ans. (e) (f) a fluid coupling transmission = a double-impeller energy transmission device . Ans. (f) (g) a power plant steam turbine = an axial flow turbine . Ans. (g) 11.3 A PDP can deliver almost any fluid, but there is always a limiting very-high viscosity for which performance will deteriorate. Can you explain the probable reason? Solution: High-viscosity fluids take a long time to enter and fill the inlet cavity of a PDP. Thus a PDP pumping high-viscosity liquid should be run slowly to ensure filling. Ans. 11.4 An interesting turbomachine is the torque converter [58], which combines both a pump and a turbine to change torque between two shafts. Do some research on this concept and describe it, with a report, sketches and performance data, to the class. Solution: As described, for example, in Ref. 58, the torque converter transfers torque T from a pump runner to a turbine runner such that ω pump Τ pump ω turbine Τ turbine . Maximum efficiency occurs when the turbine speed ω turbine is approximately one-half of the pump speed ω pump . Ans.

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810 Solutions Manual Fluid Mechanics, Fifth Edition 11.5 What type of pump is shown in Fig. P11.5? How does it operate? Solution: This is a flexible-liner pump. The rotating eccentric cylinder acts as a “squeegee.” Ans. Fig. P11.5 11.6 Fig. P11.6 shows two points a half- period apart in the operation of a pump. What type of pump is this? How does it work? Sketch your best guess of flow rate versus time for a few cycles. Solution: This is a diaphragm pump. As the center rod moves to the right, opening A and closing B, the check valves allow A to fill and B to discharge. Then, when the rod moves to the left, B fills and A discharges. Depending upon the exact oscillatory motion of the center rod, the flow rate is fairly steady, being higher when the rod is faster. Ans. Fig. P11.6 11.7 A piston PDP has a 5-in diameter and a 2-in stroke and operates at 750 rpm with 92% volumetric efficiency. (a) What is the delivery, in gal/min? (b) If the pump delivers SAE 10W oil at 20 ° C against a head of 50 ft, what horsepower is required when the overall efficiency is 84%?
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