A Study on Axial Skewing Effect of a Turbine Stator by 3-D Navier-Stokes Analysis

Abstract

The objective of the present paper is to investigate the axial skewing effect of a turbine stator blading on its aerodynamic characteristics systematically, to find the possibility for reducing the secondary losses by using axially skewed bladings and to understand better its flow physics in turbomachinery. In the present paper a typical turbine stator blading is applied as an example to generate a set of axially skewed bladings for systematical study and illustration of their differences of aerodynamics characteristics. The paper gives the procedure for generating different forward-skewed and backward-skewed blades with the same profile sections at the same radius and the numerical method used is also described briefly. The method is based on the 3-D time-marching finite volume Navier-Stokes solution and was developed by the Institute of Engineering Thermophysics, Chinese Academy of Sciences. The turbulence model proposed by Baldwin and Lomax is used here for predicting the effective viscosity. The calculated results and their comparisons are also given in the present paper. On the basis of the analysis it is shown that the appropriate use of skewed blades gives designers another possibility to control the flow in the blade channel. By adopting forward-skewed blades to replace the straight blades can be reduced the blade loading near the leading edge and in the central part of the span. It is also found that the pressure gradient at the endwall of forward-skewed blading yields the radial force that enables to avoid the boundary layer separation from the endwall. The axial skew of blade enables to restrain the strength of the secondary flow. Therefore, the total pressure loss can be reduced. An attention should be paid: if the skewed blade for stator is chosen to be used, the radial distribution of the outlet flow angle from stator vane is required to meet the optimal incidence satisfaction to the rotor blades. Otherwise, it results in the reduction of efficiency.