进口预旋对离心叶轮气动性能影响机理的研究

将理论推导和数值模拟相结合,对典型离心压缩机Eckardt叶轮流场进行分析,探讨了不同进气预旋对叶轮气动性能的影响;从叶片进口攻角、叶尖相对马赫数和流向压力变化的角度,阐述了预旋对内部流动以及气动性能的影响机理。结果表明:预旋角对进口攻角和叶尖相对马赫数同时产生显著影响,正预旋会降低进口来流的攻角及相对马赫数,使叶片前缘载荷降低、叶轮效率及稳定性提升;负预旋会提升叶轮的做功能力,使总压比上升;正预旋由于降低了叶片前部做功能力,使低压流体堆积到叶片中后部,导致总压比下降;叶轮最高效率受叶尖相对马赫数与进口攻角共同影响,若提升效率必须合理协调预旋对二者的影响。

Study on the influence mechanism of inlet pre-swirl on aerodynamic performance of centrifugal impeller

The Eckardt impeller is studied by the combination of theory and numerical simulation. The influence of different pre-swirl on the performance curve of the impeller is discussed. The influence mechanism of pre-swirl on internal flow is analyzed mainly from the inlet angle of attack, blade tip relative Mach number and change in total pressure along streamwise. The results show that pre-swirl will have a significant impact on the inlet angle of attack and the blade tip relative Mach number. Positive pre-swirl will reduce the angle of attack, the relative Mach number of the inlet flow, and the load on the leading edge of the blade, and will also improve the efficiency and stability of the impeller. In order to improve the efficiency, a reasonable pre-swirl must be formed to reduce the inlet angle of attack and the relative Mach number of inlet flow. Negative pre-swirl will enhance the impeller’s working force, and the total pressure ratio will rise, while positive pre-swirl will make the front blade’s working force worse, so that the low-pressure fluid will accumulate in the middle and rear blades, leading to the decrease of the total pressure ratio. The maximum efficiency is affected by the relative Mach number of blade tips and the angle of attack at the inlet.