SEPARATING LOSS IN AXIAL-FLOW-TURBINE CASCADES

The use of a system of basic hydrogasdynamic equations, which was written for the portion of contraction of the fl ow at entry into a cascade of axial-fl ow turbine profi les at large angles of reattachment to the walls of a blade passage, has enabled the authors to obtain analytical dependences (characteristics) of the loss on the angles of entry of the fl ow into the cascade. The obtained procedure of calculating the loss permits taking account of the radius of rounding of the profi les at entry, on which the region of insensitivity to the angle of attack is dependent, and also determining relevant fl ow-entry angles limiting the insensitivity region. The authors have proposed variants of the procedure for both an incompressible-fl uid model and a compressible gas, where use is made of the gasdynamic functions of the reduced velocity. The calculated characteristics of the turbine cascades are in good agreement with the existing experimental data in a wide range of angles of attack and radii of rounding of the profi les′ leading edges. The infl uence of the fl ow compressibility on the loss has been shown. To test the procedure under the conditions of pulsed fl ow through the turbine where the angles of attack are particularly large, the authors carried out investigations whose results are also in good agreement with the results of corresponding calculations.
   
Author:  Yu. A. Grishin and V. N. Bakulin
Keywords:  turbine, angle of attack, separating loss, system of equations, characteristics, gasdynamic functions
Page:  868