Compressor Instability with Integral Methods Episode 1 Part 4 ppt

Chapter 2

Stall Prediction of In-flight Compressor

due to Flaming of Refueling Leakage near Inlet

In this chapter, the critical distortion line and the integral method explained in

Chap. 1 are extended further to investigate more practical applications about the

propagation of strong distortion at inlet of an axial compressor. The practical ap￾plications, such as the inlet conditions of flaming of leakage fuel during mid-air

refueling process, are implemented to show the details of the numerical methodol￾ogy used in analysis of the axial flow compressor behavior and the propagation of

inlet distortion. From the viewpoint of compressor efficiency, the propagation of

inlet flow distortion is further described by compressor critical performance and

its critical characteristic. The simulated results present a useful physical insight to

the significant effects of inlet parameters on the distortion extension, velocity, and

compressor characteristics. The distortion level, flow angle and the size of dis￾tortion area at compressor inlet, and the rotor blade speed are found being the

major parameters affecting the mass flow rate of engine.

2.1 Introduction

The inlet flow distortion may cause the rotating stall, surge, or a combination of

both. An inlet distortion is often encountered when the real flow is associated with

some degree of angle of attack to the engine nacelle. Take-off, landing and gust

encounter are some typical examples of such situation. On the other hand, the inlet

distortion can also occur when the leakage of fuel enters the compressor and con￾sumes part of the mass during the air to air refueling.

Since a severe inlet distortion may lead to a stall of fan blade and fatal loss of

engine power, the evaluation of inlet distortion effects is very important in the en￾gine safety problem. If such evaluation can be measured quantitatively, the de￾signer may be able to design the compressor stage with a minimum effect of inlet

distortion ([3], [4] and [5]).

With the rapid development in computational sciences, the numerical simula￾tion of complete three-dimensional flows within multiple stages of compressor is

becoming more effective and practical in design application. Nevertheless, many

CFD codes have to be converted for parallel computation in recent year when it is

implemented in large-scale simulations ([2], [8] and [11]), because such a complex