EXPERIMENTAL AND NUMERICAL INVESTIGATION OF BLADE ROW SPACING EFFECTS IN A 1.5 STAGE TURBINE RIG UNDER OFF-DESIGN OPERATING CONDITIONS

摘要

Subject of this paper is a detailed investigation of the effects of a variable axial gap between the blade rows on efficiency of a 1.5 stage axial flow turbine rig under off-design operating conditions. This includes a variation of rotational speed as well as different pressure ratios. The investigated machine is a low aspect ratio subsonic cold air turbine test rig with modern three dimensional shaped LPT airfoils. The influence of the blade row spacing has been analyzed by conducting steady and unsteady RANS simulations as well as measurements in the test rig. Both potential and viscous flow interactions including secondary flows are investigated. The results show an aerodynamic improvement of efficiency and favourable spatial distribution of secondary kinetic energy by reducing the axial gap under design conditions as well as a variation with changed operating point.