离心压气机无叶扩压器设计研究

Design of Vaneless Diffuser for Centrifugal Compressor

为研究无叶扩压器不同几何设计参数对离心压气机性能的影响,利用数值模拟方法,针对叶片数为16、压比为4.2、流量为0.9 kg/s的离心压气机通过改变其无叶扩压器叶轮出口处的叶高W1、扩压器出口高度W2、叶轮出口半径R_(3)、扩压器收缩段半径R_(4)和扩压器出口半径R_(5)的值进行仿真计算。分析数值模拟结果表明:W2/W1在0.82以下,应调整(R_(4)-R_(3))/(R_(5)-R_(3))的值在0.35以上,若(R_(4)-R_(3))/(R_(5)-R_(3))的取值偏小会造成收缩段后部发生边界层分离的情况,流动损失增加,导致压气机效率下降;W2/W1在0.82以上,应调整(R_(4)-R_(3))/(R_(5)-R_(3))的值在0.35以下,若(R_(4)-R_(3))/(R_(5)-R_(3))偏大,会使的无叶扩压器对叶轮尾缘涡流加速效果不理想,导致扩压器内逆压梯度下降,扩压能力下降,压气机的效率下降。

In order to study the influence of different geometric design parameters of the vaneless diffuser on the performance of the centrifugal compressor,a centrifugal compressor with 16 vanes,a pressure ratio of 4.2 and a flow rate of 0.9 kg/s was used.The vane height W1at the impeller outlet of the vaneless diffuser,the diffuser outlet height W2,the impeller outlet radius R_(3),the diffuser contraction section radius R_(4)and the diffuser outlet radius R_(5)were changed,and the numerical simulation method was used to simulate them.The results show that if W2/W1is below 0.82,the value of(R_(4)-R_(3))/(R_(5)-R_(3))should be adjusted above 0.35.If the value of(R_(4)-R_(3))/(R_(5)-R_(3))is too small,boundary layer separation will occur at the rear part of the contraction section.In this case,flow losses increase,resulting in reduced compressor efficiency;if W2/W1is above 0.82,the value of(R_(4)-R_(3))/(R_(5)-R_(3))should be adjusted below 0.35.If(R_(4)-R_(3))/(R_(5)-R_(3))is too large,the vaneless diffuser will be damaged.The acceleration effect of the eddy current on the trailing edge of the impeller is not ideal,resulting in a decrease in the back pressure gradient in the diffuser,a decrease in the diffusing capacity,and a decrease in the efficiency of the entire compressor.