Parametric Study of Tip Clearance—Casing Treatment on Performance and Stability of a Transonic Axial Compressor

Abstract

The control of tip leakage flow through the clearance gap between the moving and stationary components of rotating machines is still a high-leverage area for improvement of stability and performance of aircraft engines. Losses in the form of flow separation, stall, and reduced rotor work efficiency are results of the tip leakage vortex (TLV) generated by interaction of the main flow and the tip leakage jet induced by the blade pressure difference. The effects are more detrimental in transonic compressors due to the interaction of shock TLV. It has been previously shown that the use of slots and grooves in the casing over tip of the compressor blades, known as casing treatment, can substantially increase the stable flow range and therefore the safety of the system but generally with some efficiency penalties. This paper presents a numerical parametric study of tip clearance coupled with casing treatment for a transonic axial-flow compressor NASA Rotor 37. Compressor characteristics have been compared to the experimental results for smooth casing with a 0.356 mm tip clearance and show fairly good agreement. Casing treatments were found to be an effective means of reducing the negative effects of tip gap flow and vortex, resulting in improved performance and stability. The present work provides guidelines for improvement of steady-state performance of the transonic axial-flow compressors and improvement of the stable operating range of the system.

Numerical Study on the Effect of Single Shallow Circumferential Groove Casing Treatment on the Flow Field and the Stability of a Transonic Compressor

“…But the groove which whose width is greater than 20%, not only reduces the stall margin, but also reduces the total pressure ratio and the efficiency of the compressor significantly so that the maximum decline occurs using Config-a0w100. Effect of this configuration on the compressor behavior is similar to the effect of increased tip gap size on the behavior of Rotor 37 that was investigated by Beheshti et al (2004). They demonstrated that large tip gap has detrimental effects on the pressure rise, stability, and efficiency of the compressor.…”

Investigations on the Effects of Inflow Condition and Tip Clearance Size to the Performance of a Compressor Rotor

“…To improve compressor per formance and expand stability range, many passive/active control methods were proposed by researchers, such as casing treatment [4,5], tip micro-injection [6,7], endwall blade profiling [8,9], and positive effects were gained. Study on the endwall flow evolving into the passage is not only an impor tant but also a difficult issue in the past few years.…”

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In v e s tig a tio n s on th e E ffects of In flo w C o n d itio n and T ip C le a ra n c e S ize to th e P e rfo rm a n c e of a C o m p re s s o r R o to r

To clearly clarify the effects of different upstream boundary layer thickness and tip clear ance size to the detailed tip flow field and flow mechanism, numerical simulations are performed on a subsonic compressor rotor, which is used for low-speed model testing of a rear stage embedded in a modern high-pressure compressor. To improve compressor per formance and expand stability range, many passive/active control methods were proposed by researchers, such as casing treatment [4,5], tip micro-injection [6,7], endwall blade profiling [8,9], and positive effects were gained. Second, comparisons are made for tip leakage vortex (TLV) structure, the interface of leakage flowlmainflow, endwall loss, isentropic efficiency and pressure-rise among different operating conditions.

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State-of-Art of Transonic Axial Compressors

“…10. Single extended casing circumferential groove (Beheshti et al, 2004) Fig. 11 is related to a numerical investigation of casing contouring effects on flow instability.…”