微型燃机向心透平叶轮顶部间隙流动的数值模拟

Numerical Simulation of Tip Clearance Flow in a Radial Inflow Turbine for Microturbines

对自行研制的100kW微型燃气轮机向心透平叶轮,在级环境设计工况下的顶部间隙流动进行了全三维黏性数值模拟研究,其动静间隙信息传递采用混合平面方法,湍流模型采用SpalartAllmaras模型.结果表明向心透平叶轮顶部间隙流场在轮壳相对运动速度很高的情况下,其影响因素除了所熟知的叶轮叶片顶部间隙两侧压差以及已得到试验验证的轮壳相对运动外,还有另一个重要因素是叶轮叶片表面次流,其存在使得叶轮顶部间隙流场更加复杂;叶轮进口较大的负冲角是该向心透平叶轮叶片表面较强次流形成的主要原因,在研究向心透平叶轮顶部间隙流场时不应忽略.

Tip clearance flow in a radial inflow turbine rotor for the developed 100 kW microturbine under the design condition and stage environment was investigated by 3-dimensional viscous numerical simulation with Spalart-Allmaras turbulence model, in which the mixing plane approach was adopted to transfer the flow interaction information between rotating and non-rotating mesh blocks. The results indicate that with higher relative casing motion velocity, secondary flow on rotor blade surface was one of flow impact factors on rotor tip clearance apart from well-known pressure difference between the pressure and suction sides and relative casing motion, which have been validated by experimental investigation. Because of the existence of secondary flow on rotor blade surface, the flow structure became more complex in rotor tip clearance. Moreover, larger negative incidence angle at rotor inlet was the primary reason of stronger secondary flow formed on the rotor blade surface. Thus the factor of incidence angle at rotor inlet should not be neglected while investigating flow fields of rotor tip clearance in a radial inflow turbine rotor.