14-Practice Problems - Chapter 14 Turbomachinery Problem...

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Unformatted text preview: Chapter 14 Turbomachinery Problem 14.1 A propeller is to be selected for a light airplane with a mass of 1500 kg which will cruise at 100 m/s at an altitude where the density is 1 kg/m 3 The lift-to-drag ratio at cruise conditions is 30:1, and the engine rpm is 3500. The thrust coe g33- cient at maximum e g33 ciency is 0.03, and the maximum e g33 ciency is 60%. Find the diameter of the propeller, the advance ratio at maximum e g33 ciency, and the power output required by the engine. Solution At cruise conditions, the drag is equal to the thrust. g87 = g71 = g79g64 ( g79g64g71 ) = 1500 × 9 g61 81 g64 30 = 490 g61 5 N The thrust is given by g87 = g70 g87 g29g113 2 g71 4 490 g61 5 = 0 g61 03 × 1 × μ 3500 60 ¶ 2 g71 4 = 102 g61 1 g71 4 Solving for diameter g71 4 = 4 g61 805 g71 = 1 g61 48 m The advance ratio is g77 = g89 g114 g113g71 = 100 58 g61 3 × 1 g61 48 = 1 g61 16 125 126 CHAPTER 14. TURBOMACHINERY The power output is g83 = g87g89 g114 g20 = 490 g61 5 × 100 g61 6 = 81 g61 75 kW = 110 hp Problem 14.2 A pump delivers 0.25 m 3 /s of water against a head of 250 m at a rotational speed of 2000 rpm. Find the speci g31 c speed, and recommend the appropriate type of pump. Solution The speci g31 c speed of the pump is g113 g118 = g113g84 1 g64 2 ( g106 g4 g75 ) 3 g64 4 = 2000 60 × g61 25 1 g64 2 (9 g61 81 × 250) 3 g64 4 = 0 g61 048 From Fig. 14.14, a mixed g32 ow pump is recommended....
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This note was uploaded on 12/18/2011 for the course ECON 102 taught by Professor Drfcvvv during the Spring '11 term at Politechnika Wrocławska.

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14-Practice Problems - Chapter 14 Turbomachinery Problem...

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