The influence of the last stage blades swirl to the efficiency of «stage-diffuser» unit of stationary GTU

Abstract

THE PURPOSE. Determination of the optimal law of swirling of the blades of the last stage of a stationary GTU. Due to the specificity of its operating conditions - in a system with a diffuser - the traditional laws of swirling lead to a non-optimal flow in the diffuser and, consequently, reduce the efficiency of the entire unit and the power plant as a whole. In this paper, we used numerical and experimental methods for studying a three-dimensional flow. Two stages with different laws of swirling were investigated - with the traditional law of constancy of the angle of flow out of the guide vanes along the radius, and with reverse swirling. The same diffuser was used in both cases. METHODS. Experimental studies were carried out using pneumometric five-channel probes of an original design on an ET-4 aerodynamic stand in the Turbomachinery laboratory of SPbPU. Numerical studies were carried out in the CFX gas dynamic calculation package; the parameters in the corresponding sections, obtained during the physical experiment, were used as boundary conditions.RESULTS. Integral characteristics of the stage, the vector of flow velocities in various sections were obtained. The experiment was compared with the numerical calculation and showed satisfactory convergence of the results. CONCLUSION. The optimal swirling law for the last stage operating in a system with a diffuser is forced vortex flow.