A numerical methodology for investigating compressor instabilities in a multistage environment is presented. The method is based on a stage-by-stage dynamic compression model and considers air compressibility explicit...A numerical methodology for investigating compressor instabilities in a multistage environment is presented. The method is based on a stage-by-stage dynamic compression model and considers air compressibility explicitly throughout the compressor. It involves discretizing the compression system into distinct elements and a use of the local elemental characteristic of mean performance. The models are presented in both nonlinear and linearized forms. The linearised form permits well surge condition prediction for multistage axial compressors, while the non-linear form is able to investigate the growth of local flow disturbances, and helps to develop practical control strategy. Validations were carried out using the data from several aircraft engine compressors. A good experiment-model consistency is achieved.展开更多
The purpose of the investigation is to obtain the mechanism of affecting the performance and stability of an axial flow compressor with two kinds of multi distortion area.In the investigation,the compressor inlet dist...The purpose of the investigation is to obtain the mechanism of affecting the performance and stability of an axial flow compressor with two kinds of multi distortion area.In the investigation,the compressor inlet distortion is made by the distortion generator,which is a column and is placed in the compressor rotor passage upstream.The five-passages unsteady numerical results show that the compressor performances for two kinds of multi distortion area are both lower than that for the clean inlet,and the compressor peak efficiencies for inlet distortions of 6×12 degrees and 6×24 degrees are about 3.5%,and 9.2%lower than that for the clean inlet,respectively.Further,two kinds of multi distortion area both reduce the compressor stability,and the stall margin improvements of–2.93%and–6.11%are provided by inlet distortions of 6×12 degrees and 6×24 degrees,respectively.The flow field analyses show that the flow conditions of the rotor tip inlet upstream deteriorate after the application of multi distortion area.The values of axial velocity and flow angle of incoming flows in some regions,which are near the shroud,become small due to the adverse effect made by the inlet distortion.So,the circulation capacity of the regions becomes low,and inlet blockages appear in some rotor tip passages.The bigger the distorted range is,the greater inlet blockages and corresponding flow losses are.When multi distortion area changes from 6×12 degrees to 6×24 degrees,there are obvious separations of the boundary layer near the blade suction surface in some blade tip passages,and the serious separations prevent the incoming flows from entering the blade tip passage.As a result,overflows occur at the leading edge of the blade tip.Furthermore,as the number of the distortion generator increases by a factor of one,the effects of inlet distortion on the amplitudes of the air relative velocity and static pressure in the rotor inlet upstream at the distortion generator passing frequency of 1076.5 Hz increase by a factor of about one.展开更多
Parametric study of tip injection was implemented experimentally on a subsonic axial flow compressor to understand the underlying flow mechanisms of stability improvement of the compressor with discrete tip injection....Parametric study of tip injection was implemented experimentally on a subsonic axial flow compressor to understand the underlying flow mechanisms of stability improvement of the compressor with discrete tip injection.Injector throat height varied from 2 to 6 times the height of rotor tip clearance,and circumferential coverage percentage ranged from 8.3% to 25% of the annulus.Static pressure fluctuations over the rotor tip were measured with fast-response pressure transducers.Whole-passage time-accurate simulations were also carried out to help us understand the flow details.The combinations of tip injection with traditional casing treatments were experimentally studied to generate an engineering-acceptable method of compressor stall control.The results indicate that the maximum stability improvement is achieved when injectors are choked despite their different sizes.The effect of circumferential coverage percentage on compressor stability depends on the value of injector throat height for un-choked injectors,and vice versa.Tip blockage in the blade passage is greatly reduced by the choked injectors,which is the primary reason for stability enhancement.The accomplishment of blockage diminishment is maintained in the circumferential direction with the unsteady effect of tip injection,which manifests as a hysteresis between the recovery of tip blockage and the recovery of tip leakage vortex.The unsteady effect is primarily responsible for the effectiveness of tip injection with a partial circumferential coverage.Tip injection cannot enhance the stability of the rotor with axial slots significantly,but it can improve the stability of the rotor with circumferential grooves further.The combined structure of tip injection with circumferential grooves is an alternative for engineering application.展开更多
On the base of an assumed steady inlet circumferential total pressure distortion, three-dimensional time-dependent numerical simulations are conducted on an axial flow subsonic compressor rotor. The performances and f...On the base of an assumed steady inlet circumferential total pressure distortion, three-dimensional time-dependent numerical simulations are conducted on an axial flow subsonic compressor rotor. The performances and flow fields of a compressor rotor, either casing treated or untreated, are investigated in detail either with or without inlet pressure distortion. Results show that the circumferential groove casing treatment can expand the operating range of the compressor rotor either with or without inlet pressure distortion at the expense of a drop in peak isentropic efficiency. The casing treatment is capable of weakening or even removing the tip leakage vortex effectively either with or without inlet distortion. In clean inlet circumstances, the enhancement and forward movement of tip leakage vortex cause the untreated compressor rotor to stall. By contrast, with circumferential groove casing, the serious flow separation on the suction surface leads to aerodynamic stalling eventually. In the presence of inlet pressure distortion, the blade loading changes from passage to passage as the distorted inflow sector is traversed. Similar to the clean inlet circumstances, with a smooth wall casing, the enhancement and forward movement of tip leakage vortex are still the main factors which lead to the compressor rotor stalling eventually. When the rotor works trader near stall conditions, the blockage resulting from the tip leakage vortex in all the passages is very serious. Especially in several passages, flow-spillage is observed. Compared to the clean inlet circumstances, circumferential groove casing treatment can also eliminate the low energy zone in the outer end wall region effectively.展开更多
The unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady performance characteristics,casing wall pres...The unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady performance characteristics,casing wall pressure fluctuations and their wavelet analyses.The main feature of the test compressor is a capacity tank facility connected in series to the compressor outlet in order to supply compression and/or expansion waves from downstream of the compressor.Research attention is focused on the post-stall characteristics of the surge and rotating stall which occur simultaneously.The influence of the compressor operating point on the unsteady performance curve shows that the surge cycle changes irregularly depending on the steady-state resistance characteristics,and the results of the wavelet analyses of the wall pressure fluctuations suggest that the surge cycle may selectively be determined by the rotating stall cell structure within the rotor cascade.展开更多
Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experimentally investigated by detail measurements of unsteady performance characteristics and casing wall pressu...Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experimentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected directly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system. The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The results suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.展开更多
The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady character...The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe: surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.展开更多
A model to predict the double leakage and tip leakage leading edge spillage flows was developed.This model was combined by a TLV trajectory model and a TLV diameter model and formed as a function of compressor one-dim...A model to predict the double leakage and tip leakage leading edge spillage flows was developed.This model was combined by a TLV trajectory model and a TLV diameter model and formed as a function of compressor one-dimensional design parameters,i.e.the compressor massflow coefficient,Ф and compressor loading coefficient,ψ,and some critical blade geometrical parameters,i.e.blade solidity,σ,stagger angle,βS,blade chord length,C,and blade pitch length,S.By using this model,the double leakage and tip leakage leading edge spillage flow could be predicted even at the compressor preliminary design process.Considering the leading edge spillage flow usually indicates the inception of spike-type stall,i.e.the compressor is a tip critical design,this model could also be used as a tool to choose the critical design parameters for designers.At last,some experimental data from literature was used to validate the model and the results proved that the model was reliable.展开更多
A basic equation system for meridional throughflow fileds in multistage axial flow compressors has been deduced,containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in ...A basic equation system for meridional throughflow fileds in multistage axial flow compressors has been deduced,containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in a unified form.The equation system shows that spanwise mixing of meridional flows in compressors is attributed to three kinds of mechanism:molecular motion,turbulent diffusion,and circumferential non-uniformities,the last of which includes secondary flow effects and others,Therefore the equation system unifles the two models for spanwise mixing coefficients defined and introduced into the basic equation system,a novel,much simpler equation system,without additional unknown correlation terms included,has been obtained.This novel equation system makes throughflow computations including mixing far easier for multistage compressors .It has been rigorously shown that these apparent mixing coefficients contain full information of all the three kinds of mixing mechanism,so that the simpler equation system can also be taken as a unified model for meridional flows with all the dinds of the mixing effects.Calculations of the flow through multistage machines have been made by incorporating the new model into a streamline curvature throughflow calculation method and the improved agreement with experimental data has been obtained.It is believed that the simpler equation system can be apphed to the flows not only in subsonic but in transonic and supersonic compressors if an appropriate model is propsed for the apparent mixing coeffcients.展开更多
In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocit...In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocity gradient. Experimental study is carried out in a single stage axial compressor by using Hot-wire Anemometer (HWA). Simultaneously, the numerical calculation is brought out in the same experiment rig. Firstly, we analyze the time-averaged velocity and radial vorticity at different axial positions, and explore the wake variability along the axial direction. Then, we present the effects of operation conditions on the wake-core position, and find out the inlet Mach number and incident angle are both the key influence factors of the wake-core position. Finally, we summarize four preliminary conclusions of the wake variability.展开更多
The estimation of the precise performance of existing multistage axial-flow compressors of gas turbine engines is fast becoming a great concern, as the use of gas turbine engines in the power generation and in the mil...The estimation of the precise performance of existing multistage axial-flow compressors of gas turbine engines is fast becoming a great concern, as the use of gas turbine engines in the power generation and in the military industry increases, in order to reduce the analysis performance error of the traditional scaling method, a new scaling method for estimating the characteristics of multistage axial flow compressors is proposed. This novel method is based on experimental and partial data provided by engine manufacturers. Taking the effect of density-change into account, we introduce the average infinitesimal stage concept, and thereby divide the compression process into an infinite number of infinitesimal processes corresponding to infinitesimal stages. Subsequently, we adopt the corrected Reynolds analogy method for compressible flow calculation in order to ensure much better compliance with the similarity criterion, Validation checks show that the proposed method has enough precision to predict the off-design performance characteristics of multistage axial flow compressors.展开更多
Boundary layer suction is an e ective method used to delay separations in axial compressors. Most studies on bound?ary layer suction have focused on improving the performance of compressors,whereas few studies investi...Boundary layer suction is an e ective method used to delay separations in axial compressors. Most studies on bound?ary layer suction have focused on improving the performance of compressors,whereas few studies investigated the influence on details of the flow fields,especially vortexes in compressors. CFD method is validated with experi?mental data firstly. Three single?slot and one double?slot endwall boundary layer suction schemes are designed and investigated. In addition to the investigation of aerodynamic performance of the cascades with and without suction,variations in corner open separation,passage vortex,and concentration shedding vortex,which are rarely seen for the flow controlled blades in published literatures,are analyzed. Then,flow models,which are the ultimate aim,of both baseline and aspirated cascades are established. Results show that single?slot endwall suction scheme adjacent to the suction surface can e ectively remove the corner open separation. With suction mass flow rate of 0.85%,the overall loss coe cient and endwall loss coe cient of the cascade are reduced by 25.2% and 48.6%,respectively. Besides,this scheme increases the static pressure rise coe cient of the cascade by 3.2% and the flow turning angle of up to 3.3° at 90% span. The concentration shedding vortex decreases,whereas the passage vortex increases. For single?slot suction schemes near the middle pitchwise of the passage,the concentration shedding vortex increases and the passage vortex is divided into two smaller passage vortexes,which converge into a single?passage vortex near the trailing edge section of the cascade. For the double?slot suction scheme,triple?passage vortexes are presented in the blade passage. Some new vortex structures are discovered,and the novel flow models of aspirated compressor cascade are proposed,which are important to improve the design of multi?stage aspirated compressors.展开更多
The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possibl...The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.展开更多
For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential dist...For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential distributions concerning the splitter cascades upon the aerodynamic performance were investigated. The studies show that the optimum splitter cascade is not very close to the suction side of main blade. The load between the main blade and the splitter blade can be soundly distributed in terms of the adjustment of circumferential position of the splitter blade. The best aerodynamic performance can be successfully obtained according to the optimum shape of the expanding fluid channel reasonably formed by the splitter blade and the main blade.展开更多
基金This project is supported by National Natural Science Foundation of China (No.50146014) National Natural Science Foundation of Xi'an Jiaotong University, China (No.573023).
文摘A numerical methodology for investigating compressor instabilities in a multistage environment is presented. The method is based on a stage-by-stage dynamic compression model and considers air compressibility explicitly throughout the compressor. It involves discretizing the compression system into distinct elements and a use of the local elemental characteristic of mean performance. The models are presented in both nonlinear and linearized forms. The linearised form permits well surge condition prediction for multistage axial compressors, while the non-linear form is able to investigate the growth of local flow disturbances, and helps to develop practical control strategy. Validations were carried out using the data from several aircraft engine compressors. A good experiment-model consistency is achieved.
基金supports by National Natural Science Foundation of China with project No.51006084supported by National Science and Technology Major Project No.2017-II-0005-0018the Fundamental Research Funds for the Central Universities with project No.3102019ZX026。
文摘The purpose of the investigation is to obtain the mechanism of affecting the performance and stability of an axial flow compressor with two kinds of multi distortion area.In the investigation,the compressor inlet distortion is made by the distortion generator,which is a column and is placed in the compressor rotor passage upstream.The five-passages unsteady numerical results show that the compressor performances for two kinds of multi distortion area are both lower than that for the clean inlet,and the compressor peak efficiencies for inlet distortions of 6×12 degrees and 6×24 degrees are about 3.5%,and 9.2%lower than that for the clean inlet,respectively.Further,two kinds of multi distortion area both reduce the compressor stability,and the stall margin improvements of–2.93%and–6.11%are provided by inlet distortions of 6×12 degrees and 6×24 degrees,respectively.The flow field analyses show that the flow conditions of the rotor tip inlet upstream deteriorate after the application of multi distortion area.The values of axial velocity and flow angle of incoming flows in some regions,which are near the shroud,become small due to the adverse effect made by the inlet distortion.So,the circulation capacity of the regions becomes low,and inlet blockages appear in some rotor tip passages.The bigger the distorted range is,the greater inlet blockages and corresponding flow losses are.When multi distortion area changes from 6×12 degrees to 6×24 degrees,there are obvious separations of the boundary layer near the blade suction surface in some blade tip passages,and the serious separations prevent the incoming flows from entering the blade tip passage.As a result,overflows occur at the leading edge of the blade tip.Furthermore,as the number of the distortion generator increases by a factor of one,the effects of inlet distortion on the amplitudes of the air relative velocity and static pressure in the rotor inlet upstream at the distortion generator passing frequency of 1076.5 Hz increase by a factor of about one.
基金the support of the National Natural Science Foundation of China(Nos.51576162 and51236006)The Doctorate Foundation of Northwestern Polytechnical University(No.CX201422)
文摘Parametric study of tip injection was implemented experimentally on a subsonic axial flow compressor to understand the underlying flow mechanisms of stability improvement of the compressor with discrete tip injection.Injector throat height varied from 2 to 6 times the height of rotor tip clearance,and circumferential coverage percentage ranged from 8.3% to 25% of the annulus.Static pressure fluctuations over the rotor tip were measured with fast-response pressure transducers.Whole-passage time-accurate simulations were also carried out to help us understand the flow details.The combinations of tip injection with traditional casing treatments were experimentally studied to generate an engineering-acceptable method of compressor stall control.The results indicate that the maximum stability improvement is achieved when injectors are choked despite their different sizes.The effect of circumferential coverage percentage on compressor stability depends on the value of injector throat height for un-choked injectors,and vice versa.Tip blockage in the blade passage is greatly reduced by the choked injectors,which is the primary reason for stability enhancement.The accomplishment of blockage diminishment is maintained in the circumferential direction with the unsteady effect of tip injection,which manifests as a hysteresis between the recovery of tip blockage and the recovery of tip leakage vortex.The unsteady effect is primarily responsible for the effectiveness of tip injection with a partial circumferential coverage.Tip injection cannot enhance the stability of the rotor with axial slots significantly,but it can improve the stability of the rotor with circumferential grooves further.The combined structure of tip injection with circumferential grooves is an alternative for engineering application.
基金National Natural Science Foundation of China (10377013)
文摘On the base of an assumed steady inlet circumferential total pressure distortion, three-dimensional time-dependent numerical simulations are conducted on an axial flow subsonic compressor rotor. The performances and flow fields of a compressor rotor, either casing treated or untreated, are investigated in detail either with or without inlet pressure distortion. Results show that the circumferential groove casing treatment can expand the operating range of the compressor rotor either with or without inlet pressure distortion at the expense of a drop in peak isentropic efficiency. The casing treatment is capable of weakening or even removing the tip leakage vortex effectively either with or without inlet distortion. In clean inlet circumstances, the enhancement and forward movement of tip leakage vortex cause the untreated compressor rotor to stall. By contrast, with circumferential groove casing, the serious flow separation on the suction surface leads to aerodynamic stalling eventually. In the presence of inlet pressure distortion, the blade loading changes from passage to passage as the distorted inflow sector is traversed. Similar to the clean inlet circumstances, with a smooth wall casing, the enhancement and forward movement of tip leakage vortex are still the main factors which lead to the compressor rotor stalling eventually. When the rotor works trader near stall conditions, the blockage resulting from the tip leakage vortex in all the passages is very serious. Especially in several passages, flow-spillage is observed. Compared to the clean inlet circumstances, circumferential groove casing treatment can also eliminate the low energy zone in the outer end wall region effectively.
基金supported by a Grant-in-Aid for Scientific Research through grant number 20560171from Japanese Society for the Promotion of Science
文摘The unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady performance characteristics,casing wall pressure fluctuations and their wavelet analyses.The main feature of the test compressor is a capacity tank facility connected in series to the compressor outlet in order to supply compression and/or expansion waves from downstream of the compressor.Research attention is focused on the post-stall characteristics of the surge and rotating stall which occur simultaneously.The influence of the compressor operating point on the unsteady performance curve shows that the surge cycle changes irregularly depending on the steady-state resistance characteristics,and the results of the wavelet analyses of the wall pressure fluctuations suggest that the surge cycle may selectively be determined by the rotating stall cell structure within the rotor cascade.
基金supported by a Grant-in-Aid for Scientific Research through grant number 20560171 from Japanese Society for the Promotion of Science
文摘Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experimentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected directly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system. The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The results suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.
文摘The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe: surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.
基金funded by the National Natural Science Foundation of China,Grant No.51006007,51136003 and 50976009
文摘A model to predict the double leakage and tip leakage leading edge spillage flows was developed.This model was combined by a TLV trajectory model and a TLV diameter model and formed as a function of compressor one-dimensional design parameters,i.e.the compressor massflow coefficient,Ф and compressor loading coefficient,ψ,and some critical blade geometrical parameters,i.e.blade solidity,σ,stagger angle,βS,blade chord length,C,and blade pitch length,S.By using this model,the double leakage and tip leakage leading edge spillage flow could be predicted even at the compressor preliminary design process.Considering the leading edge spillage flow usually indicates the inception of spike-type stall,i.e.the compressor is a tip critical design,this model could also be used as a tool to choose the critical design parameters for designers.At last,some experimental data from literature was used to validate the model and the results proved that the model was reliable.
文摘A basic equation system for meridional throughflow fileds in multistage axial flow compressors has been deduced,containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in a unified form.The equation system shows that spanwise mixing of meridional flows in compressors is attributed to three kinds of mechanism:molecular motion,turbulent diffusion,and circumferential non-uniformities,the last of which includes secondary flow effects and others,Therefore the equation system unifles the two models for spanwise mixing coefficients defined and introduced into the basic equation system,a novel,much simpler equation system,without additional unknown correlation terms included,has been obtained.This novel equation system makes throughflow computations including mixing far easier for multistage compressors .It has been rigorously shown that these apparent mixing coefficients contain full information of all the three kinds of mixing mechanism,so that the simpler equation system can also be taken as a unified model for meridional flows with all the dinds of the mixing effects.Calculations of the flow through multistage machines have been made by incorporating the new model into a streamline curvature throughflow calculation method and the improved agreement with experimental data has been obtained.It is believed that the simpler equation system can be apphed to the flows not only in subsonic but in transonic and supersonic compressors if an appropriate model is propsed for the apparent mixing coeffcients.
文摘In this paper, we investigate the stator wake variability along the axial direction under different rotating speeds and mass flow conditions, in the terms of wake-core position, wake depth, wake width and wake velocity gradient. Experimental study is carried out in a single stage axial compressor by using Hot-wire Anemometer (HWA). Simultaneously, the numerical calculation is brought out in the same experiment rig. Firstly, we analyze the time-averaged velocity and radial vorticity at different axial positions, and explore the wake variability along the axial direction. Then, we present the effects of operation conditions on the wake-core position, and find out the inlet Mach number and incident angle are both the key influence factors of the wake-core position. Finally, we summarize four preliminary conclusions of the wake variability.
基金This project is supported by National Natural Science Foundation of China (No.59970220).
文摘The estimation of the precise performance of existing multistage axial-flow compressors of gas turbine engines is fast becoming a great concern, as the use of gas turbine engines in the power generation and in the military industry increases, in order to reduce the analysis performance error of the traditional scaling method, a new scaling method for estimating the characteristics of multistage axial flow compressors is proposed. This novel method is based on experimental and partial data provided by engine manufacturers. Taking the effect of density-change into account, we introduce the average infinitesimal stage concept, and thereby divide the compression process into an infinite number of infinitesimal processes corresponding to infinitesimal stages. Subsequently, we adopt the corrected Reynolds analogy method for compressible flow calculation in order to ensure much better compliance with the similarity criterion, Validation checks show that the proposed method has enough precision to predict the off-design performance characteristics of multistage axial flow compressors.
基金Supported by China Postdoctoral Science Foundation(Grant No.2016M600015)National Natural Science Foundation of China(Grant Nos.51741601,51236006)
文摘Boundary layer suction is an e ective method used to delay separations in axial compressors. Most studies on bound?ary layer suction have focused on improving the performance of compressors,whereas few studies investigated the influence on details of the flow fields,especially vortexes in compressors. CFD method is validated with experi?mental data firstly. Three single?slot and one double?slot endwall boundary layer suction schemes are designed and investigated. In addition to the investigation of aerodynamic performance of the cascades with and without suction,variations in corner open separation,passage vortex,and concentration shedding vortex,which are rarely seen for the flow controlled blades in published literatures,are analyzed. Then,flow models,which are the ultimate aim,of both baseline and aspirated cascades are established. Results show that single?slot endwall suction scheme adjacent to the suction surface can e ectively remove the corner open separation. With suction mass flow rate of 0.85%,the overall loss coe cient and endwall loss coe cient of the cascade are reduced by 25.2% and 48.6%,respectively. Besides,this scheme increases the static pressure rise coe cient of the cascade by 3.2% and the flow turning angle of up to 3.3° at 90% span. The concentration shedding vortex decreases,whereas the passage vortex increases. For single?slot suction schemes near the middle pitchwise of the passage,the concentration shedding vortex increases and the passage vortex is divided into two smaller passage vortexes,which converge into a single?passage vortex near the trailing edge section of the cascade. For the double?slot suction scheme,triple?passage vortexes are presented in the blade passage. Some new vortex structures are discovered,and the novel flow models of aspirated compressor cascade are proposed,which are important to improve the design of multi?stage aspirated compressors.
文摘The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.
文摘For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential distributions concerning the splitter cascades upon the aerodynamic performance were investigated. The studies show that the optimum splitter cascade is not very close to the suction side of main blade. The load between the main blade and the splitter blade can be soundly distributed in terms of the adjustment of circumferential position of the splitter blade. The best aerodynamic performance can be successfully obtained according to the optimum shape of the expanding fluid channel reasonably formed by the splitter blade and the main blade.