The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studi...The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studies by our team have shown that the induced shock resulting from the circumferentially diverging clearance structure has remarkable effect on suppressing leakage flow in transonic compressor rotors.Therefore,the inherent correlations between the characteristics of induced shock and leakage flow are further elucidated in this paper,and the influencing rules of induced shock wave on tip flow characteristic of transonic rotors are summarized as well.The results demonstrate that the enhancement of inhibitory effects on leakage flow and increase in the rotor’s stall margin can be achieved by both intensifying the induced shock wave and shifting its circumferential position away from the suction side edge of blade tip,which is possible by adjusting the circumferential expansion ratio of diverging clearance.The stall margin of the transonic rotor exhibits three distinct variations as the circumferential expansion ratio of the diverging clearance increases monotonically,and a maximum improvement of over 8.9%can be achieved through feature variations of the induced shock wave.The insufficient acceleration of the supersonic leakage jet flow over blade tip due to a smaller circumferential expansion ratio poses challenges in inducing a shock wave,resulting in an increased blockage effect and reduced stall margin of rotor.Meanwhile,excessive circumferential expansion ratio results in a pronounced adverse pressure gradient originating from the induced shock wave,leading to leakage flow separation at the blade tip and consequently weakening the intensity of induced shock waves while shifting its circumferential position towards the blade tip.As a result,further increasing the circumferential expansion ratio does not yield an enhanced rotor stall margin but instead exhibits a slight decreasing trend.展开更多
Circumferentially non-uniform tip clearances induced by rotor eccentricity significantly affect the overall performance of axial compressors,particularly the stability margin.Currently,Computational Fluid Dynamics(CFD...Circumferentially non-uniform tip clearances induced by rotor eccentricity significantly affect the overall performance of axial compressors,particularly the stability margin.Currently,Computational Fluid Dynamics(CFD)plays a crucial role in the aerodynamic analysis of eccentric compressors.However,conventional full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)simulations are prohibitively expensive for routine design and analysis purposes.To address this issue,the paper presents a novel Fourier-based method,called the Time-Space Collocation(TSC)method,for efficient simulations of eccentric compressors.This method coherently treats temporal and spatial harmonics,making it well-suited to tackle the rotor eccentricity problem,as the perturbation waves induced by eccentricity are time-periodic with respect to the rotor and space-periodic with respect to the stator.Three numerical cases,including NASA Rotor 67,original Stage 67,and Stage 67 with a reduced rotor-stator axial gap,were conducted to verify the effectiveness of the TSC method.The results indicate that,for the rotor eccentricity levels studied in this paper,the influence of weak rotor-stator interactions can be disregarded in the original Stage 67.In this situation,applying three harmonics can accurately capture both the performance variations and the non-uniformly distributed flowfields of eccentric compressors,while achieving a reduction in run time by two orders of magnitude compared to full-annulus URANS simulations.However,in Stage 67 with a reduced rotor-stator axial gap,the results that include rotor-stator interactions align much more closely with the URANS results.Nevertheless,the TSC simulations can still achieve speed-ups of several dozen times.Overall,the TSC method shows promising potential for application within the engineering community.展开更多
Tip leakage flow affects the flow stability of high-loading compressors significantly.Therefore,a novel approach via induced shock wave near suction-side edge of blade tip was proposed to suppress the strength and inf...Tip leakage flow affects the flow stability of high-loading compressors significantly.Therefore,a novel approach via induced shock wave near suction-side edge of blade tip was proposed to suppress the strength and influence range of leakage flow in a transonic rotor.Three new schemes with different circumferentially diverging degrees of clearance were designed to reveal the mechanism of the new approach.Through the action of the circumferentially diverging clearance(from the pressure side to the suction side over blade tip),a much more dramatic acceleration of the supersonic leakage jet flow appeared over blade tip of the new schemes.An induced shock wave was produced near the suction side edge of blade tip due to the pressure difference between the discharging leakage flow and the surrounding high-pressure mainflow in tip channel.As a result,both the mass flow rate and the outlet velocity of leakage flow were reduced significantly via the induced shock wave.Meanwhile,the suppressing effect of the new approach on the tip leakage jet flow was closely related to the strength and circumferential location of the induced shock wave.With the aids of the induced shock wave,the largest improvement of tip flow characteristics with an over 5%increase in stall margin was realized in new transonic rotor when the circumferential divergence angle equals 8°,accompanied with no more than a 0.4%decrease in isentropic efficiency.展开更多
基金the General Program of National Natural Science Foundation of China(Grant No.52076124)the Joint Fund of the National Natural Science Foundation of China(No.U2441278).
文摘The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studies by our team have shown that the induced shock resulting from the circumferentially diverging clearance structure has remarkable effect on suppressing leakage flow in transonic compressor rotors.Therefore,the inherent correlations between the characteristics of induced shock and leakage flow are further elucidated in this paper,and the influencing rules of induced shock wave on tip flow characteristic of transonic rotors are summarized as well.The results demonstrate that the enhancement of inhibitory effects on leakage flow and increase in the rotor’s stall margin can be achieved by both intensifying the induced shock wave and shifting its circumferential position away from the suction side edge of blade tip,which is possible by adjusting the circumferential expansion ratio of diverging clearance.The stall margin of the transonic rotor exhibits three distinct variations as the circumferential expansion ratio of the diverging clearance increases monotonically,and a maximum improvement of over 8.9%can be achieved through feature variations of the induced shock wave.The insufficient acceleration of the supersonic leakage jet flow over blade tip due to a smaller circumferential expansion ratio poses challenges in inducing a shock wave,resulting in an increased blockage effect and reduced stall margin of rotor.Meanwhile,excessive circumferential expansion ratio results in a pronounced adverse pressure gradient originating from the induced shock wave,leading to leakage flow separation at the blade tip and consequently weakening the intensity of induced shock waves while shifting its circumferential position towards the blade tip.As a result,further increasing the circumferential expansion ratio does not yield an enhanced rotor stall margin but instead exhibits a slight decreasing trend.
文摘Circumferentially non-uniform tip clearances induced by rotor eccentricity significantly affect the overall performance of axial compressors,particularly the stability margin.Currently,Computational Fluid Dynamics(CFD)plays a crucial role in the aerodynamic analysis of eccentric compressors.However,conventional full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)simulations are prohibitively expensive for routine design and analysis purposes.To address this issue,the paper presents a novel Fourier-based method,called the Time-Space Collocation(TSC)method,for efficient simulations of eccentric compressors.This method coherently treats temporal and spatial harmonics,making it well-suited to tackle the rotor eccentricity problem,as the perturbation waves induced by eccentricity are time-periodic with respect to the rotor and space-periodic with respect to the stator.Three numerical cases,including NASA Rotor 67,original Stage 67,and Stage 67 with a reduced rotor-stator axial gap,were conducted to verify the effectiveness of the TSC method.The results indicate that,for the rotor eccentricity levels studied in this paper,the influence of weak rotor-stator interactions can be disregarded in the original Stage 67.In this situation,applying three harmonics can accurately capture both the performance variations and the non-uniformly distributed flowfields of eccentric compressors,while achieving a reduction in run time by two orders of magnitude compared to full-annulus URANS simulations.However,in Stage 67 with a reduced rotor-stator axial gap,the results that include rotor-stator interactions align much more closely with the URANS results.Nevertheless,the TSC simulations can still achieve speed-ups of several dozen times.Overall,the TSC method shows promising potential for application within the engineering community.
基金sponsored by the General Program of National Natural Science Foundation of China (Grant No.52076124)the National Science and Technology Major Project (Grant No.J2019-Ⅱ-0014-0035)
文摘Tip leakage flow affects the flow stability of high-loading compressors significantly.Therefore,a novel approach via induced shock wave near suction-side edge of blade tip was proposed to suppress the strength and influence range of leakage flow in a transonic rotor.Three new schemes with different circumferentially diverging degrees of clearance were designed to reveal the mechanism of the new approach.Through the action of the circumferentially diverging clearance(from the pressure side to the suction side over blade tip),a much more dramatic acceleration of the supersonic leakage jet flow appeared over blade tip of the new schemes.An induced shock wave was produced near the suction side edge of blade tip due to the pressure difference between the discharging leakage flow and the surrounding high-pressure mainflow in tip channel.As a result,both the mass flow rate and the outlet velocity of leakage flow were reduced significantly via the induced shock wave.Meanwhile,the suppressing effect of the new approach on the tip leakage jet flow was closely related to the strength and circumferential location of the induced shock wave.With the aids of the induced shock wave,the largest improvement of tip flow characteristics with an over 5%increase in stall margin was realized in new transonic rotor when the circumferential divergence angle equals 8°,accompanied with no more than a 0.4%decrease in isentropic efficiency.
