变几何涡轮可调叶栅过渡态特性研究

Research on Transition State Characteristics of Variable Geometry Turbine Adjustable Cascade

变几何涡轮使发动机在变工况下的性能得到提升,为了更透彻地了解变几何涡轮导叶转动过程中参数的变化情况,通过数值模拟及试验方法探究可调叶栅过渡态特性。将变几何涡轮导叶进行调节,导叶调大范围为0°~6°,导叶调小范围为0°~-5°,观察过渡态参数变化规律。试验研究表明:导叶在调大及调小过程中,导叶出口质量流量、绝对气流角和绝对马赫数随转角接近线性变化,导叶出口总压损失系数和熵增接近抛物线变化;导叶从0°向-5°转动过程绝对出口马赫数减小了2.2%,总压损失系数增加了37.3%;导叶从0°向6°转动过程中,导叶出口马赫数增加了1.5%,导叶出口总压损失系数减小了15.8%;在导叶转角和二次流改变的影响下,吸力侧和压力侧来流在导叶尾缘后掺混改变,沿叶高分布的出口绝对气流角不同程度地偏离几何出口角;导叶转角调大,上部通道涡沿叶高上移,泄漏涡和通道涡相互削弱,总压损失系数减小。

Variable geometry turbines improve the performance of the engines under variable operating conditions.In order to understand the changes of parameters during the rotation of the variable geometry turbine guide vane more thoroughly, explores the transition state characteristics of the adjustable blade cascade through numerical simulation and experimental method.The guide vane adjustment range is-5° to 6°,and observe the transition state parameter changes.Experimental research shows that during the process of adjusting, the change law of the guide vane, the mass flow rate, absolute airflow angle and absolute Mach number of the guide vane are linearly changed with the angle of rotation, and the total pressure loss coefficient and entropy increase of the guide vane are close to parabolic changes.The absolute exit Mach number line of the guide vane from 0° to-5° is reduced by 2.2%,and the total pressure loss coefficient is increased by 37.3%.During the turning of the guide vane from 0 degrees to 6 degrees, the Mach number of the guide vane outlet increased by 1.5%,and the total pressure loss coefficient at the guide vane outlet decreased by 15.8%.Under the influence of the changes of guide vane angle and secondary flow, the suction side and pressure side incoming flow will mix and change after the trailing edge of the guide vane, and the outlet absolute airflow angle distributed along the height of the blade deviates from the geometric outlet angle to varying degrees.The turning angle of the guide vane is increased, the upper channel vortex moves up along the blade height, the leakage vortex and the channel vortex weaken each other, and the total pressure loss coefficient decreases.