An Investigation of Efficiency Limits for Small, Cooled Turbines
Final technical rept.
NORTHERN RESEARCH AND ENGINEERING CORP WOBURN MA
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The report describes the results of a combined analytical and experimental investigation of the efficiency limits of small, cooled turbines. The first section of the report is concerned with the design procedure whereby optimal stage aerodynamic and blade designs were established for nine representative turbine stages. Three levels of corrected work output at each of three annulus heights were considered. The second section contains the results obtained in cascade tests of the resulting stator and rotor mean section blading and six additional rotor root profiles. Both total and profile losses were measured in each case. In the third section, a correlation of blade row total- pressure-loss coefficient is obtained from the experimental data. Stage efficiencies are then recalculated for the nine original stages based on the derived correlation. The achievable stage efficiencies are presented and discussed in the fourth major section of the report. Results indicate that the aspect ratio penalties associated with small annulus heights are considerably less severe than previous studies would suggest.
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