Abstract
In order to detect the aerodynamic instability of a multistage axial compressor more accurately and earlier, the harmonic Fourier mean amplitude analysis method and heterotopic variance analysis method are developed. The dynamic instability prediction performance of the two methods is studied on a low-speed and a high-speed two-stage axial compressor. The harmonic Fourier mean amplitude analysis method is suitable for predicting the aerodynamic instability of a multistage axial compressor in the form of a rotating stall. Compared with the traditional harmonic Fourier analysis methods, the harmonic Fourier mean amplitude analysis method can capture the detail of the pressure signal more accurately and it can effectively prevent instability misjudgment. The heterotopic variance analysis method is developed based on the conventional variance analysis method, and it can be used to distinguish whether the compressor is in the rotating stall or the surge state. The heterotopic variance analysis method can predict the aerodynamic instability ahead of the harmonic Fourier mean amplitude analysis method, and fewer circumferential measuring points were employed. The layout of the measuring points also influences the detection of the aerodynamic instability of the compressor. The aerodynamic instability of the high-speed axial compressor can be predicted earlier by employing measuring points at the compressor outlet.
Highlights
As the power unit of an aircraft, the aeroengine may enter various aerodynamic instability states, inducing thrust reduction, extra fuel consumption, and critical problems
The maximum amplitudes of the first-order harmonic were taken as the prediction indicator of compressor instability. 0.25 s, 0.5 s, and 1.0 s were chosen as the time window, and 1100 Pa was taken as the warning threshold
Early and accurate detection of the aerodynamic instability compressor was realized on a multistage axial compressor under two newly developed methods: the harmonic Fourier mean amplitude analysis method and the heterotopic variance analysis method
Summary
As the power unit of an aircraft, the aeroengine may enter various aerodynamic instability states (rotating stall and surge), inducing thrust reduction, extra fuel consumption, and critical problems. Once the aerodynamic instability is likely to or has already appeared, measures such as adjusting the fuel mass flow rate, the turbine inlet guide area, and the installation angle of the inlet guide are often taken to stabilize the engine down to the stable working condition. If the working state of the aeroengine is misadjusted due to an unreliable aerodynamic instability detection method, the performance of the engine would be reduced suddenly. To avoid potential flight safety risks, accurate and early detection of the aerodynamic instability of the aeroengine is necessary. The working condition of the engine can be changed from the stable state to the unstable state by fuel step, nozzle area closing, adjustment of the turbine guide installation angle, and injection of gas from the highpressure compressor outlet
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