Abstract
The compressor design requirement was for a pressure ratio of 3.6, with a peak pressure ratio of 4.3 at the maximum non-dimensional speed of the impeller of 1.66. Due to the stress-limited speed, an aluminium alloy impeller was specified, the impeller discharge blade backsweep had to be restricted and the application of prewhirl was considered from the outset as a means of extending the operating range. A non-dimensional conceptual design procedure, including the effect of inlet prewhirl, was applied to the design of three turbo- charger impellers. An impeller, designated A, was designed with the inclusion of 25° of prewhirl. A second impeller, designated B, was designed with zero prewhirl for comparison purposes, but was not manufactured. A third impeller, C, was manufactured through the modification of an existing design and the design study was applied to the assessment of this third design.
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