Optimization study on the influence of little blades’ spatial position on a compressor cascade performance

Abstract

To reveal the importance of little blades’ spatial position to improve the cascade performance at different condition, the pitchwise and axial direction of the little blades on the end-wall are adopted as the optimization variables to complete a double-objective optimization. Meanwhile, the three-dimensional flow field characteristics of the cascade with and without little blades are analyzed comparatively. The study found that as the optimal solutions are obtained at the three bigger incidences (3°, 5°, and 7°), the optimal position is always close to the leading edge of blade and far away from the blade suction surface, and the more intuitive design suggestions are given in this article. Moreover, at the near design conditions (−1°, 0°, and 1°), little blades increase the total pressure loss and reduce the static pressure, which are considered unsuitable for improving the cascade performance. If the stable operation range are the main performance indicators, the optimization of the little blades’ spatial position should be completed at the near stall condition (7° incidence). If the conditions with mid-range incidences (2°< i <5°) are the main performance index, the parameter optimization of little blades should be achieved at 5°. Based on the further flow field analysis of the optimization results obtained at 3°, 5°, and 7° incidences (named Opt_Act3, Opt_Act5, and Opt_Act7), the induced vortices resist the effect of axial reverse pressure gradient and pass through the blade passage, which is the main reason for the total pressure loss reduction. Appropriate spatial position of little blades not only strengthens the capability to prevent the low-energy fluids accumulating in the corner region near the end-wall, but exhibits sufficient advantage to weaken the boundary layer.

Numerical Study on the Corner Separation Control for a Compressor Cascade via Bionic Herringbone Riblets

“…For corner separation control, researchers have carried out a lot of research and have developed boundary layer aspiration [3,4], plasma [5,6] or fluidic [7] actuators, continuous and synthetic jets [8], a non-axisymmetric endwall [9,10], vortex generators [11][12][13][14], bladeend slots [15,16] and other active and passive control technologies. As a typical passive control method, the traditional blade-type vortex generator has been successfully applied in the corner separation control due to its effectiveness and easy implementation [11,12].…”

“…These losses are mainly caused by the mixing of induced vortices and the windward resistance of the vortex generation geometry. Reducing the size of the vortex generator can move the induced vortex closer to the bottom of the boundary layer and reduce the geometric upwind resistance, thus reducing the additional loss [13,14]. However, the reduction in the size of the vortex generator will lead to a significant reduction in the strength of the induced vortex.…”

“…Even if the herringbone riblets are comparatively smaller in size than the traditional vortex generators, the strength of the induced vortex created by herringbone riblets is guaranteed by the cumulative impact of the micro-scale riblets, and a smaller size means fewer additional losses. Now that traditional vortex generators have been successfully applied in corner separation control [11][12][13][14], the herringbone riblets are considered to have great potential in controlling corner separation. As far as the authors are aware, the effects of herringbone riblets on the corner separation of a cascade have not been reported.…”