RESEARCH ON THE APPLICABILITY OF USING A CURVED BLADE TO OPTIMIZE THE FLOW LOSS WEIGHT DISTRIBUTION OF A LINEAR COMPRESSOR CASCADE WITH DIFFERENT FLOW SEPARATION TYPES

Due to the influence of an adverse pressure gradient, three types of flow separation occur on the suction surface of a linear compressor cascade: full-span open separation, corner closed separation and a corner stall condition. A numerical simulation was performed using a topological analysis method to determine the applicability of using a curved blade to improve the total pressure loss coefficient of a cascade with different types of flow separation situations on the suction surface. First, the accuracy of the ANSYS CFX program was verified against existing experimental data to balance the relationship between the calculation accuracy and the time savings. Second, the incidence characteristics of the cascade were analyzed to determine the incident conditions for three types of flow separation. Three factors of the cascade were considered to analyze a cascade with and without a curved blade: the transferring process of the topological structure on the blade suction surface, the evolution process of the vortex structure in the cascade passage and the weight distribution of the total pressure loss coefficient. The results indicate that the strength and scale of the concentrated shedding vortex (CSV) is distinctly reduced in the corner stall condition due to the influence of radial migration by the curved blade; thus, the flow loss is observably reduced. In the corner closed separation condition, the scale of the corner separation was too small to be notably reduced. In the full-span open separation condition, the curved blade not only reduced the total pressure loss coefficient but also increased the strength and scale of the passage vortex (PV). Finally, the curved blade method improved the applicability of reducing the flow loss in the corner stall condition and increased the stability and margin of a highly loaded compressor.