An experimental investigation of a low Reynolds number, high Mach number centrifugal compressor
Author(s)
Shirley, Gregory B. (Gregory Brenton), 1975-
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Advisor
Alan H. Epstein.
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Experiments were performed on a super-scale test facility to study the performance of very small centrifugal compressors suitable for microfabrication. ThE test facility was 75 times larger than the full-scale device and operated under 17/5 atmospheric pressure conditions to correctly match the Reynolds number, which is about 20,000. The impeller tip speed of the test facility matched those in the design full-scale device to capture the effects of compressibility. Two compressor geometries were tested, one with and one without diffuser vanes; the same impeller was used in both cases. For each of the diffuser designs, speed lines were determined at impeller tip speeds of 400 mis, corresponding to 100% of the design value, and 170 mis, corresponding to 42% of design. Detailed measurements were made at a single operating point on each of the speedlines. The test results show that the total-to-static pressure ratios developed by the facility are in agreement with CFO prediction. The measured mass flow rates are between the values predicted by 2-D and 3-D CFO. The performance of the vaned diffuser (Cp=0.48) is superior to that of the vaneless diffuser (Cp=0.24) in recovering the dynamic pressure of air exiting the impeller. The impeller isentropic efficiencies are about 0.48 and 0.27 for 100% and 42% design impeller speeds, respectively. These values are substantially lower than the predictions of CFO. The difference is thought to be due in part to the interaction of the flow in the impeller with the impeller casing, and to the effects of inlet separation. This study confirms computational predictions for pressure rise, and is consistent with compuational predictions of mass flow rate. However, the measured efficiency is lower than CFD predictions. Additional testing is required to determine the sources of loss in the impeller.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998. Includes bibliographical references (p. 119-120).
Date issued
1998Department
Massachusetts Institute of Technology. Department of Aeronautics and AstronauticsPublisher
Massachusetts Institute of Technology
Keywords
Aeronautics and Astronautics