ABOUT THE INFLUENCE OF THE CLEARANCE BETWEEN THE WORKING BLADES AND HOUSING OF A RADIAL TURBINE ON ITS EXPONENT
AIR FORCE SYSTEMS COMMAND WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB
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The results of a 1959 experimental study of dissipation in an air radial turbine are reported. The relative internal turbine efficiency was determined Re number variation was 1.1 - 1.7 x 1,000,000 turbine pressure drop, 1.25 and 1.67 gap variation, 0.15 - 7 mm. It is found that the gap clearance loss plays an important role in the axial part of the rotor, and only a very little role in the radial part. The gap swirl results in a gap-to-channel gas flow, and this phenomenon reduces the gas leakage around the rotor-blade tips. The above phenomenon is also enhanced by Coriolis forces. In subsequent testing of various radial turbines, it was noticed that the turbine efficiency depended only very slightly on the gap value. It is found that 1 The gap loss is considerably lower in radial centripetal turbines than in axial turbines hence, the gaps in radial turbines need not be very small 2 An empirical formula has been developed for calculating the gap loss 3 A gas-dynamic scheme is suggested to explain the low gap loss.
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