离心叶轮与扩压器相互干扰数值模拟

Numerical Simulation of Impeller-diffuser Interaction in Centrifugal Compressor

采用定常与非定常数值模拟方法,对某小型离心压气机进行数值计算,首先比较了定常结果与非定常时均结果的特性;然后结合离心叶轮出口和径向扩压器进口典型位置非定常压力脉动的频域特性,研究了离心叶轮与扩压器之间的转静干涉作用;最后着重分析了离心叶轮带与不带分流叶片对径向扩压器进口压力脉动频率特性的影响。结果表明:在相同流量下,非定常时均结果的压比偏高约3.7%,效率偏高0.1%;在带有分流叶片的离心压气机中,离心叶轮叶片出口与扩压器叶片进口的脉动除了叶片通过频率的非定常脉动外,分流叶片尾缘会产生与之强度相当的2倍叶片通过频率的非定常压力脉动。同时,分流叶片会对径向扩压器进口产生更强的0.5倍叶片通过频率非定常压力脉动,这些频率的非定常压力脉动很可能会对离心压气机叶片的疲劳强度造成影响。

Steady and unsteady numerical simulations of a small centrifugal compressor are presented in this paper. First, the steady and unsteady time-averaged results are compared. Then, the unsteady interaction between the impeller and dif- fuser is investigated by analyzing the spectrum characteristics of pressure fluctuations at the outlet of the impeller and the in- let of the radial diffuser. Finally, the unsteady influences of the impeller with and without splitters on the radial diffuser inlet are studied. Results show that the unsteady time-averaged total pressure ratio and isentropic efficiency are respectively 3.7% and 0. 1% higher than those of the steady at the same mass flow; in the centrifugal compressor with splitters, pres- sure fluctuations at the blade passing frequency are the main fluctuations at the out^et of the impeller and the inlet of the radial diffuser. Besides, it is obvious that there are fluctuations two times the radial diffuser blade passing frequency at the outlet of the splitter and half times the impeller blade passing frequency at the inlet of the radial diffuser blades caused by the splitter. These unsteady pressure fluctuations will likely affect the fatigue strength of the centrifugal compressor.