The effect of injector size on compressor performance in a transonic axial compressor with discrete tip injection

Abstract

The present study investigates the effects of injector size, which covers both circumferential extent and radial extent on compressor stability and radial work redistribution using time-accurate three-dimensional numerical simulations for multi-passages in a transonic compressor with discrete tip injection. Injector width ranges from 1% to 14.5% of casing perimeter and injector throat height varies from 2 to 6 times the height of rotor tip clearance. Six identical injectors are uniformly mounted around the annulus. Results indicate that, with sufficient covering of injection, tip injection can significantly improve compressor stability. Stability margin is improved by 3.5% employing 0.65% of the annulus mass flow. With injector width increased, stability improves sharply when the width is less than 4.5% of casing perimeter, but increases flatly for the rest coverage. Expanding injector throat height to an intermediate level can further enhance compressor stability, but excessive throat height is detrimental on account of the deterioration of the aerodynamic characteristic of Coanda injector. The average decrement of the blockage in injection region, which is defined as injection efficiency, is a key factor that takes primary responsibility for the capacity of tip injection in stability improvement. Injection efficiency derived from the same operating condition for all the configurations with tip injection is well-qualified to estimate the trend of stability improvement. The unsteady influence on radial work redistribution is much more significant than the time-averaged one.

Effects of modified micro-vortex generators on aerodynamic performance in a high-load compressor cascade

“…Therefore, many active and passive control devices were used to control the impact of secondary flow. Active flow control techniques were widely exploited in high-load compressors, 2 such as boundary layer aspiration, 3 vortex generator jet, 4 tip injection, 5 and so on. On the other hand, passive flow control devices were developed by a contrasting idea, which can get rid of the constraint of external equipment to control the secondary flow of a compressor.…”

Mechanism study of performance enhancement in a subsonic axial flow compressor with recirculating casing treatment

“…Nie et al 12 disclosed that a micro air injection using very small amount of air could improve the compressor stability by shifting the position of tip clearance vortex toward downstream without unloading the rotor tip. Beheshti et al 13 and Wang et al 14,15 found that tip injection reduced the TLF-related blockage, which was responsible for the stability enhancement of NASA Rotor 37. The latter built a relationship between the improvement in the stability and the decrement in the blockage.…”

“…The stabilizing effect of tip injection can be briefly summarized as the unloading effect, [7][8][9][10][11] the action on TLF or endwall blockage, [12][13][14][15][16][17] and the unsteady effect. [20][21][22][23][24] However, it is difficult to evaluate the influence on compressor efficiency accurately for the tip injection with external air source.…”

Experimental study of self-recirculating casing treatment in a subsonic axial flow compressor

“…17,20,25,29 The injection velocity should be maximized by choking the injectors. 20,[23][24][25]32 Partly covering the annulus is adequate, although the optimal coverage is different for different compressors. 16,17,32,33 Nevertheless, the optimal options of some other parameters are still in dispute, such as injection yaw angle, i.e.…”

“…20,[23][24][25]32 Partly covering the annulus is adequate, although the optimal coverage is different for different compressors. 16,17,32,33 Nevertheless, the optimal options of some other parameters are still in dispute, such as injection yaw angle, i.e. whether the jets should be injected axially (indicated or proved by Suder et al, 19 Strazisar et al, 20 and Weichert et al 28 ) or be made aligned with the blade camber line of rotor tip (supported by Hathaway, 21 Cassina et al, 23 and Khaleghi et al 25 ) is not determined.…”