脉冲频率与幅度对两级涡轮非定常特性的影响

涡轮复合技术中脉冲排气对两级涡轮性能产生显著影响。为探明脉冲来流下两级涡轮非定常特性,该文基于三维非定常流动仿真模型研究了排气脉冲频率与幅度的影响。模型中,高压级涡轮内流动采用全通道模拟以考虑蜗壳引起的非对称流动,低压级涡轮内流动采用单通道模拟以提高计算效率。结果表明,当脉冲频率从40 Hz增加到120 Hz,高压级涡轮瞬时功率峰值显著增大15.4%,而低压级涡轮瞬时功率峰值变化在1%以内;随脉冲幅度增大,低压级涡轮效率下降幅度比高压级涡轮更大,当脉冲幅度系数为1.6时,高、低压级涡轮转子效率分别下降3.66%和8.09%;低压级涡轮转子从叶中到叶尖处的进口流动攻角在脉冲周期内大幅度变化,引起叶片前缘处产生显著流动损失。

Impacts of pulse frequency and amplitude on the unsteady characteristics of a two-stage turbine

The pulsating exhaust in turbocompound technology significantly exerts effects on the performance of the two-stage turbine.The effects of exhaust pulse frequency and amplitude were investigated to reveal the unsteady characteristic of the two-stage turbine under pulsating flow conditions on the base of a threedimensional unsteady flow simulation model.In the model,the flows in the high-pressure turbine were modeled using full stage passage,which could consider the asymmetric flows caused by the volute.The flows in the lowpressure turbine were modelled using single passage to improve the calculation efficiency.The results show that as the frequency increases from 40 to 120 Hz,the peak instantaneous power of high-pressure stage turbine increases significantly by 15.4%,while the peak instantaneous power of low-pressure stage turbine changes within 1%.With the increase of pulse amplitude,the efficiency of low-pressure stage turbine decreases more greatly than that of high-pressure stage turbine.When the coefficient of the pulse amplitude is 1.6,the rotor efficiencies of the high-and low-pressure stage drop down 3.66%and 8.09%,respectively.The incidence angle of low-pressure turbine rotor from the middle to the tip of the blade varies significantly during the pulse period,resulting in significant flow loss at the leading edge of the blade.