Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researche...Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.展开更多
Numerical investigation is conducted on a 3.5-stage axial compressor,on which numerous experimental projects were carried out at the Institute during the last years and an experimental database was established.In the ...Numerical investigation is conducted on a 3.5-stage axial compressor,on which numerous experimental projects were carried out at the Institute during the last years and an experimental database was established.In the current study five on-and off-design operating points are simulated using a RANS solver and the results are compared with the measurement.The result shows that the compressor performance can be qualitatively predicted by the mixing-plane method.Better agreement is obtained for the on-design operating point.However,as the flow unsteadiness is insufficiently considered,the numerical method produces end-wall low-speed flow layers accumulated with the flow passing through the passage,which is in no good agreement with the experimental data.In the numerical simulation the rotor rows receive less work and this difference from the measurement increases with the rotational speed.In contrast,the stator rows increase the pressure more efficiently than the measurement.In the simulation the flow in the last stator row tends more to separate on the pressure side of the blade.For the operating points close to the surge line,the predicted separation is more intense than the experimental observation.But for the operating points close to the choke,the separation is suppressed.展开更多
In this study,the influence of inter-stage bleeding on the compressor performance and inter-stage flow field of a multistage axial compressor is investigated by both experimental and numerical methods.The experiment i...In this study,the influence of inter-stage bleeding on the compressor performance and inter-stage flow field of a multistage axial compressor is investigated by both experimental and numerical methods.The experiment is conducted on a four-stage low-speed axial compressor,and a specific computational model is built to simulate the experiment environment accurately.To illuminate the fluid mechanisms of bleeding effect in detail,both the experiment and the simulation are carried out twice,i.e.,in the first time,the mass flow rate upstream the bleed location is constant under different bleed rate conditions;while in the second time,the mass flow rate downstream the bleed location is constant under different bleed rate conditions.The results demonstrate that inter-stage bleeding has little influence on upstream compressor characteristics,and affects the upstream flow field only in the rear half of the stator.The bleed effect on the downstream flow field is embodied in the variation of an incoming flow profile,an increase as the compressor inlet flow coefficient decreases.Therefore,such an effect is only significant on compressor characteristics at small flow coefficient conditions.In multistage compressors,the variation of compressor characteristics and flow field caused by inter-stage bleeding is the comprehensive result of the bleeding and the variation of the upstream working condition.In addition,the comparison between numerical and experimental results shows that the flow moves towards top half of span through the downstream rotor passage in the numerical simulation,whereas the trend of flow field variation with different bleed rates at the outlet of the downstream rotor and stator is the same with that at the inlet of the downstream rotor in the experiment,which means that the numerical method has overestimated the radial mixing intensity of the flow.展开更多
A 15-stage axial-flow compressor utilized in steel industry was studied in this paper. All the stator's stagger angles of the compressor are variable to ensure the multistage compressor operate effectively within ...A 15-stage axial-flow compressor utilized in steel industry was studied in this paper. All the stator's stagger angles of the compressor are variable to ensure the multistage compressor operate effectively within a wide range of flow rate and meanwhile satisfy the demand for sufficient pressure ratio, adiabatic efficiency and stall margin. Three in all different base-settings of stator's stagger angles were presented and commercial CFD software was applied to obtain the overall performance characteristics. The results showed that both of the optimized base-settings improved the performances both in summer and winter conditions, although the adiabatic efficiency was somewhat decreased. Taking incidence angle and stage loading into consideration, differences among the three cases were analyzed in detail. On the basis of numerical computations, the performance could be effectively improved through adjusting the base-setting of stator's stagger angles.展开更多
In previous studies,a theoretical model was developed after Acoustic Resonance(AR)was experimentally detected in a four-stage compressor,and AR inception was proposed to be triggered by an unknown sound source,which i...In previous studies,a theoretical model was developed after Acoustic Resonance(AR)was experimentally detected in a four-stage compressor,and AR inception was proposed to be triggered by an unknown sound source,which is a pressure perturbation of a specific frequency with a suitable circumferential propagation speed.The present paper,which is not dedicated to the simulation of acoustic field,aims to identify the specific sound source generated by the unsteady tip leakage flow using the unsteady Computational Fluid Mechanics(CFD)approach.After a comprehensive analysis of an Unsteady Reynolds Averaged Navier-Stokes(URANS)simulation,a pressure perturbation of non-integer multiple of rotor frequency is found at the blade tip.Since the essence of the tip leakage flow is a jet flow driven by the pressure difference between two sides of blade,a simplified tip leakage flow model is adopted using Large Eddy Simulation(LES)in order to simulate the jet flow through a tip clearance.It is found that the convection velocity of shedding vortices fits the expected propagation speed of the sound source,the frequency is also close to one of the dominating frequencies in the URANS simulation,and the resultant combination frequency coincides with the experimentally measured AR frequency.Since such a simplified model successfully captures the key physical mechanisms,it is concluded that this paper provides a piece of unambiguous evidence on the role of unsteady tip leakage vortex in triggering the AR inception of the multistage compressor.展开更多
Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the ...Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet.Four variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage impeller.Reynolds Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,respectively.Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller.The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.展开更多
基金co-supported by the National Natural Science Foundation of China(Nos.51576009,11661141020 and 51711530036)the Aeronautical Science Foundation of China(No.20151554002)。
文摘Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation.And the excitation factor of high intensity sound wave to rotor blades should not be ignored.Experimental researches are conducted on a multistage high pressure compressor.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor.The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time.This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed.When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor.It can be confirmed that acoustic resonance occurs in the multistage compressor.The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.
文摘Numerical investigation is conducted on a 3.5-stage axial compressor,on which numerous experimental projects were carried out at the Institute during the last years and an experimental database was established.In the current study five on-and off-design operating points are simulated using a RANS solver and the results are compared with the measurement.The result shows that the compressor performance can be qualitatively predicted by the mixing-plane method.Better agreement is obtained for the on-design operating point.However,as the flow unsteadiness is insufficiently considered,the numerical method produces end-wall low-speed flow layers accumulated with the flow passing through the passage,which is in no good agreement with the experimental data.In the numerical simulation the rotor rows receive less work and this difference from the measurement increases with the rotational speed.In contrast,the stator rows increase the pressure more efficiently than the measurement.In the simulation the flow in the last stator row tends more to separate on the pressure side of the blade.For the operating points close to the surge line,the predicted separation is more intense than the experimental observation.But for the operating points close to the choke,the separation is suppressed.
基金the support of the National Natural Science Foundation of China(Nos.51806004,51790511)the National Science and Technology Major Project,China(No.2017-Ⅱ-0001-0013)。
文摘In this study,the influence of inter-stage bleeding on the compressor performance and inter-stage flow field of a multistage axial compressor is investigated by both experimental and numerical methods.The experiment is conducted on a four-stage low-speed axial compressor,and a specific computational model is built to simulate the experiment environment accurately.To illuminate the fluid mechanisms of bleeding effect in detail,both the experiment and the simulation are carried out twice,i.e.,in the first time,the mass flow rate upstream the bleed location is constant under different bleed rate conditions;while in the second time,the mass flow rate downstream the bleed location is constant under different bleed rate conditions.The results demonstrate that inter-stage bleeding has little influence on upstream compressor characteristics,and affects the upstream flow field only in the rear half of the stator.The bleed effect on the downstream flow field is embodied in the variation of an incoming flow profile,an increase as the compressor inlet flow coefficient decreases.Therefore,such an effect is only significant on compressor characteristics at small flow coefficient conditions.In multistage compressors,the variation of compressor characteristics and flow field caused by inter-stage bleeding is the comprehensive result of the bleeding and the variation of the upstream working condition.In addition,the comparison between numerical and experimental results shows that the flow moves towards top half of span through the downstream rotor passage in the numerical simulation,whereas the trend of flow field variation with different bleed rates at the outlet of the downstream rotor and stator is the same with that at the inlet of the downstream rotor in the experiment,which means that the numerical method has overestimated the radial mixing intensity of the flow.
文摘A 15-stage axial-flow compressor utilized in steel industry was studied in this paper. All the stator's stagger angles of the compressor are variable to ensure the multistage compressor operate effectively within a wide range of flow rate and meanwhile satisfy the demand for sufficient pressure ratio, adiabatic efficiency and stall margin. Three in all different base-settings of stator's stagger angles were presented and commercial CFD software was applied to obtain the overall performance characteristics. The results showed that both of the optimized base-settings improved the performances both in summer and winter conditions, although the adiabatic efficiency was somewhat decreased. Taking incidence angle and stage loading into consideration, differences among the three cases were analyzed in detail. On the basis of numerical computations, the performance could be effectively improved through adjusting the base-setting of stator's stagger angles.
基金the National Natural Science Foundation of China(Nos.51976116 and 51976125)the Natural Science Fund of Shanghai,China(No.19ZR1425900)+1 种基金the Open Research Subject of Key Laboratory(Fluid Machinery and Engineering Research Base)of Sichuan Province,China(No.szjj2019-022)Alexander von Humboldt Foundation.
文摘In previous studies,a theoretical model was developed after Acoustic Resonance(AR)was experimentally detected in a four-stage compressor,and AR inception was proposed to be triggered by an unknown sound source,which is a pressure perturbation of a specific frequency with a suitable circumferential propagation speed.The present paper,which is not dedicated to the simulation of acoustic field,aims to identify the specific sound source generated by the unsteady tip leakage flow using the unsteady Computational Fluid Mechanics(CFD)approach.After a comprehensive analysis of an Unsteady Reynolds Averaged Navier-Stokes(URANS)simulation,a pressure perturbation of non-integer multiple of rotor frequency is found at the blade tip.Since the essence of the tip leakage flow is a jet flow driven by the pressure difference between two sides of blade,a simplified tip leakage flow model is adopted using Large Eddy Simulation(LES)in order to simulate the jet flow through a tip clearance.It is found that the convection velocity of shedding vortices fits the expected propagation speed of the sound source,the frequency is also close to one of the dominating frequencies in the URANS simulation,and the resultant combination frequency coincides with the experimentally measured AR frequency.Since such a simplified model successfully captures the key physical mechanisms,it is concluded that this paper provides a piece of unambiguous evidence on the role of unsteady tip leakage vortex in triggering the AR inception of the multistage compressor.
基金Project(NRF-2010-013-D00007) supported by the National Research Foundation of KoreaWork finacially supported by the 2010 Research Professor Fund of Gyeongsang National University,Korea
文摘Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet.Four variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage impeller.Reynolds Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,respectively.Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller.The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.
