旋转状态下气膜冷却偏转理论的实验研究

Experimental study of deflective theory of film cooling trajectory under rotating operating conditions

关键词:  气膜冷却  偏转  热色液晶  平板模型  旋转

Key words:  Film cooling  Deflective theory  Thermochromic liquid crystal  Flat blade model  Rotating

摘要:

为了预测旋转状态下气膜轨迹偏转趋势,为叶片表面气膜孔的构型设计提供参考,基于一个平板叶片模型对旋转状态下气膜冷却中气膜轨迹偏转趋势进行了实验研究,对用于预测压力面侧气膜轨迹偏转方向的新无量纲准则数——偏转数Dn与气膜偏转的关系进行验证。实验利用热色液晶技术对叶片表面的二维色调场进行测量,并采用无线旋转拍照系统对旋转坐标系中的图像信号加以采集。结果表明,哥氏力和离心力是影响气膜轨迹偏转方向的主要因素,偏转数可以在一定程度上预测旋转状态下平板叶片的冷气出流的偏转方向,但由于径向压力梯度和粘性力的存在,预测结果存在误差。基于实验结果和偏转理论提出修正偏转数Dn*,从而提高预测的准确性。

Abstract:

A new dimensionless parameter,namely deflection number,Dn was proposed and validated experimentally to predict the film cooling trajectory on the pressure surface of a flat blade model.The steady-state thermochromic liquid crystal (TLC) technique was employed to measure the two-dimensional surface hue distribution,and all the signals from the rotating reference frame were collected and transmitted to the stationary receiver by a wireless launcher which was fixed in the rotation laboratory bench.Experimental results show that the centrifugal force and coriolis force are the main influencing factors to determine the deflective direction of film trajectory.The Dn provides a reasonable approach for distinguishing the coolant flow deflection in film cooling with deviation,which can be attributed to the influence of radial pressure gradient and viscosity force.Based on the experimental data and the deflection theory,an improved factor was added to correct the parameter,and it can be helpful in the arrangement of film-hole orientation on turbine blades.