Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetric Flow Control: Part II—Non-Axisymmetric Self Recirculation Casing Treatment

This is the Part II of a two-part paper involving the development of asymmetric flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure-ratio. Non-axisymmetric Self Recirculation Casing Treatment (SRCT) as an instance of asymmetric flow control method is presented. Experimental and numerical methods were used to investigate the impact of non-axisymmetric SRCT on surge point of the centrifugal compressor. Firstly, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (S_r). Next, several arrangements of a non-axisymmetric SRCT were designed, based on flow analysis presented in Part I. Then, a series of experiments was carried out to analyze the influence of non-axisymmetric SRCT on the compressor performance. Results show that the non-axisymmetry SRCT has certain influence on performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the non-axisymmetric SRCT is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest S_r is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.