The Experimental Research On The Tangent Slot Injection Flow To The Performance Of Diffusion Cascades

The development of aviation industry demands to the performance improvement of aero-engine, especially of aerodynamic performance of compressor. Since the end wall loss constitutes the major part of cascade energy loss, it is of high value to study the inner flow structure and loss increase mechanism inside compressor cascades and explore the way to lower end wall loss. Meanwhile, the better controlling of the boundary layer flow shall be the key step to improve the compressor performance.Flow control by air injection slot is designed to decrease transverse secondary flow at cascade by means of drilling holes or slots at blade surface or end wall, the aim is to use pressure difference between pressure side and suction side to keep low energy fluid flowing; meanwhile, separation between corner zone is restrained effectively by air injection, loss secondary flow is decreased consequently, air 's turning ability is improved within cascade, and the stable operating range of compressor is increased.The dissertation experimentally studied the aerodynamic performances of the rectangular compressor cascades composed of Straight Blade in low-speed, large-scale wind tunnel in institute of propulsion theory and technology in HIT. On design conditions, the cascade flow fields were measured by five-hole probe in detail, the static pressure was measured by tapping on the cascade surfaces and ink-trace flow visualizations was also conducted. Eight different experiments were planed which is decided by the composition of slot position, experimental results were compared in detailed. The result indicated that air injection slot improved cascade's pressure diffusing ability greatly, diffusion factor improved remarkably at the position where slot was located; after the comparison of results of three air injection slot, the optimal slot position lay in 25 percent of blade span away from the end wall, where diffusion factor improved greatly alone most span wise direction; the loss distribution at outlet was redistributed alone span wise when air injection slot was adopted into cascade, the total loss was also decreased. Air injection restrained separation at suction surface, flow condition is also improved and losses generated by separation decreased consequently; air injection decreased mixing loss which was generated by secondary flow and wake, air injection also decreased range of wake zone and high loss zone, yaw angle at end wall also decreased.