超微型涡轮中极低展弦比静叶栅流场特性的数值研究

Flow Field Characteristics of Stator Cascade with Extremely Low Aspect Ratio in an Ultra-micro Gas Turbine

通过数值求解柱坐标系下三维定常粘性雷诺时均N-S方程,结合RNGk-ε湍流模型和非平衡壁面函数,获得了超微涡轮中极低展弦比静叶栅流道内部的三维稳态粘性流场,揭示了其独特的流场物理特性和气动损失规律.结果表明:超低展弦比涡轮叶栅中存在双二次流现象;尽管超微燃气涡轮静叶栅高度仅为1.3 mm,壁面影响区占叶高的总高度仍不超过3%;叶片的静压载荷主要由中部弧段承担;总压损失主要发生在近壁区,尤其是吸力面近壁区;静叶栅径向各截面最大马赫数并不是出现在主流中央,而是介于主流中央和壁面之间的一个狭小区域,这可能与通道低能二次流与主流的掺混作用有关.

The three-dimensional steady viscous flow field of an stator cascade with extremely low aspect ratio in ultra-micro gas turbine was obtained by numerically solving the 3D Navier-Stokes equations with time averaged Reynolds stress model under cylindrical system, combined with RNG k-ε turbulent model and non equilibrium wall function. The unique physical features of flow field and the regulations of aerodynamic loss were revealed. Results show that, the phenomenon of double secondary flow exisits in extremely low aspect ratio stator. Though the height of the stator cascade in the ultra-micro gas turbine is only 1.3 mm, the wall influenced area is relatively small, less than 3% height of the stator cascade. The main static pressure load is undertaken by middle part of the profile. The total pressure loss mainly takes place in the near wall area, especially the one adjacent to suction side. The maximum Mach number on each section along spanwise appears in a narrow area between the central flow region and wall surface, not in the centre of main flow which is supposed to be. It is probably due to the mixing of low energy secondary flow with main flow.