Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ig...Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ignoring the influence of inlet distortions. This study investigates the mechanism of RI in a transonic rotor through full-annulus unsteady simulations, with a particular focus on the effects of boundary layer ingesting distortions. The results show that at the uniform inflow, the RI fluctuations with the broadband hump can be observed over a relatively wide mass flow rate range, and its origin can be attributed to the coupling effect between the tip leakage flow and shear layer instability. At the inlet distortions, the broadband hump only occurs with partial circumferential locations. This kind of flow phenomenon is defined as Partial Rotating Instability (PRI). The PRI only occurs in a narrower mass flow rate range in which the circumferential range of strong shear is sufficiently large and the self-induced unsteady effects are strong enough. Further, this study confirms that the averaged tip leakage flow axial momentum at the onset of RI or PRI is close, so it can be used as the parameter to determine whether RI or PRI occurs.展开更多
In order to alleviate the efficiency penalty of the leakage flow,especially for large relative clearance in the rear stage of highpressure compressors,numerical simulations were carried out to investigate the effect o...In order to alleviate the efficiency penalty of the leakage flow,especially for large relative clearance in the rear stage of highpressure compressors,numerical simulations were carried out to investigate the effect of the moving endwall on a compressor cascade with particular emphasis on revealing the loss mechanisms of large clearances.The flow field,loss characteristics,and entropy generation rate were analyzed.The results show that the boundary layer skew induced by the upstream moving endwall significantly improves the corner separation for the datum case without clearance.For the cases with clearances,the moving endwall not only increases the leakage loss but also enhances the loss sensitivity to the clearance size.The large turn of the streamlines causes the large spanwise gradient of the axial and pitchwise velocity components,which is the major cause of the high loss.Therefore,the leakage loss can be reduced by changing the∂Vy/∂z and∂V x/∂z terms in the middle and downstream regions of the blade passage.展开更多
An axial single-stage high-speed test rig is numerically studied in this paper with half-annulus URANS simulations to describe the flowcharacteristics at the near stall condition.Wavelet analysis is applied to demonst...An axial single-stage high-speed test rig is numerically studied in this paper with half-annulus URANS simulations to describe the flowcharacteristics at the near stall condition.Wavelet analysis is applied to demonstrate the time-frequency characteristics of the near-tip pressure signals captured by the numerical probes at different circumferential and axial positions.The detailed tip flow fields and wavelet transform results are combined to depict the generation and propagation of the spike-type stall inception.According to the wavelet spectrum,characteristic frequencies correspond to the temporal and spatial features of the rotating stall,such as the fluctuation of the shock wave,self-oscillation and propagation of tip leakage vortex et al.Consequently,the detection of typical spike stall inception can be significantly brought forward by identifying the crucial rotating disturbance and its development for the onset of stall inception.Then,the specific tip flow fields are also discussed to reveal the flow mechanism of stall inception evolution,including the leading edge spillage and the trailing edge backflow.Further investigation shows that the stall inception with smooth casing corresponds to the radial separation vortex caused by the tip leading edge spillage,which continues to develop and propagate in the circumferential direction and finally induces the stall.展开更多
基金supports of the National Natural Science Foundation of China(Nos.52076129,92360308,52376027)the Shanghai Municipal Education Commission of China(No.2023-02-4)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe United Innovation Center(UIC)of Aerothermal Technologies for Turbomachinery of China.
文摘Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ignoring the influence of inlet distortions. This study investigates the mechanism of RI in a transonic rotor through full-annulus unsteady simulations, with a particular focus on the effects of boundary layer ingesting distortions. The results show that at the uniform inflow, the RI fluctuations with the broadband hump can be observed over a relatively wide mass flow rate range, and its origin can be attributed to the coupling effect between the tip leakage flow and shear layer instability. At the inlet distortions, the broadband hump only occurs with partial circumferential locations. This kind of flow phenomenon is defined as Partial Rotating Instability (PRI). The PRI only occurs in a narrower mass flow rate range in which the circumferential range of strong shear is sufficiently large and the self-induced unsteady effects are strong enough. Further, this study confirms that the averaged tip leakage flow axial momentum at the onset of RI or PRI is close, so it can be used as the parameter to determine whether RI or PRI occurs.
基金The Natural Science Foundation of China(No.52076129,No.51576124)the National Science and Technology Major Project(2017-II-0004-0017).
文摘In order to alleviate the efficiency penalty of the leakage flow,especially for large relative clearance in the rear stage of highpressure compressors,numerical simulations were carried out to investigate the effect of the moving endwall on a compressor cascade with particular emphasis on revealing the loss mechanisms of large clearances.The flow field,loss characteristics,and entropy generation rate were analyzed.The results show that the boundary layer skew induced by the upstream moving endwall significantly improves the corner separation for the datum case without clearance.For the cases with clearances,the moving endwall not only increases the leakage loss but also enhances the loss sensitivity to the clearance size.The large turn of the streamlines causes the large spanwise gradient of the axial and pitchwise velocity components,which is the major cause of the high loss.Therefore,the leakage loss can be reduced by changing the∂Vy/∂z and∂V x/∂z terms in the middle and downstream regions of the blade passage.
基金supports from the Natural Science Foundation of Shanghai(23ZR1435400)the Aeronautical Science Foundation of China(2019ZB057006)+1 种基金Fundamental Research Funds for the Central Universities,Shanghai Municipal Education Commission(2023-02-7)the United Innovation Center(UIC)of Aerothermal Technologies for Turbomachinery.
文摘An axial single-stage high-speed test rig is numerically studied in this paper with half-annulus URANS simulations to describe the flowcharacteristics at the near stall condition.Wavelet analysis is applied to demonstrate the time-frequency characteristics of the near-tip pressure signals captured by the numerical probes at different circumferential and axial positions.The detailed tip flow fields and wavelet transform results are combined to depict the generation and propagation of the spike-type stall inception.According to the wavelet spectrum,characteristic frequencies correspond to the temporal and spatial features of the rotating stall,such as the fluctuation of the shock wave,self-oscillation and propagation of tip leakage vortex et al.Consequently,the detection of typical spike stall inception can be significantly brought forward by identifying the crucial rotating disturbance and its development for the onset of stall inception.Then,the specific tip flow fields are also discussed to reveal the flow mechanism of stall inception evolution,including the leading edge spillage and the trailing edge backflow.Further investigation shows that the stall inception with smooth casing corresponds to the radial separation vortex caused by the tip leading edge spillage,which continues to develop and propagate in the circumferential direction and finally induces the stall.
