Deviation Angle in a Turbine Nozzle Cascade with Convergent Meridional Shape of Flow Path

orc2019 Tracking Number 158

Usually, deviation angle for standard turbine cascades with subsonic flow is considered to be insignificant or isn’t taken into account at all while performing 1D/2D simulations. The existing loss models evaluate deviation angle for subsonic flow taking into account the Mach number and the blade outflow gauging angle. However, the meridional shape of the flow path is often neglected. Two turbines for which experimental data are available were considered in the article: axial (NASA Energy Efficient Engine (EEE)) and radial (NASA CR-3514). Both presented turbines have convergent meridional shape of the flow path (Figure 1). According to the Craig-Cox and Ainley-Mathieson loss models, deviation angle in the stator cascade for considered flow parameters and blade designs should not exceed 0.2-0.3 degrees. However, experimental reports have shown the deviation angle of approximately 2 degrees. Conducted CFD simulations of the considered turbines with different meridional shapes have shown that convergence of the flow path meridional shape has significant effect on the cascade deviation angle. It was found out that such effect takes place in both axial and radial turbines. Based on the analysis of the three-dimensional flow in turbine nozzle cascade a technique for calculating the deviation angle, depending on the meridional shape of the turbine flow path was proposed. In this article the developed technique is described. Using it, the new calculation of the cascade deviation angle was performed. Obtained calculation results have met good agreement with experimental data.