Inlet distortion detrimentally affects the aerodynamic performance and lessens the stability of compressors, and has received considerable attention. The need to accurately estimate its effect on the performance and stability of compressor as early as possible in a pre-design cycle is emphasized herein. This work presents a modified circumferential average through flow method (CAM) based on parallel compressor (PC) theory for compressor performance and stability analysis under inlet distortion. The PC approach classically considers independent circumferential flow zones evolving through a compressor, with the same outlet static pressure. In the present work, this theory has been modified in order to create a parametric outlet static pressure boundary condition. It enables us to deal with an upstream flow distortion map, and the meridian plane flow field can then be calculated in order to update the corresponding compressor performance. The model is applied in a compressor which has been tested for its performance characteristics under uniform inlet conditions. Utilizing the new model, the stability and performance of the compressor under inlet distortion can be estimated.
The strategy of sweep design should be based on the inner flow field of the compressor. In this paper, a transonic centrifugal compressor within the splitter is discussed in detail, and both forward sweep and backward sweep are studied with numerical simulation for optimization. Splitter introduces extra leakage and it’s worth noting that the high-entropy region is shifted from the suction side of the main blade to the suction side of the splitter. Different from the transonic axial rotor, the leakage of the main blade mainly occurs after the passage shock and will be mixed with the leakage of the splitter in the suction side of the splitter. Therefore, the flow control on the middle and rare part of the compressor is more essential for the performance of the stage. In this regard, the backward sweep of the main blade exhibits a good effect by reducing the mixing loss of secondary leakage. Due to the redistribution of the airflow, the mainstream velocity in the tip area is accelerated in the forepart and reduced in the rare part, the aerodynamic loss in the high-entropy zone is then improved, and the flow capacity of the compressor is also increased. The best performance is achieved by an 8° backward sweep for the centrifugal compressor in this work, the pressure ratio is increased by 2.84% and isentropic efficiency is increased by 1.40%, compared to the prototype.
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