The adaptive feedback control of stability with circumferential inlet distortion has been experimentally investigated in a low-speed,axial compressor.The flat-baffles with different span heights are used to simulate d...The adaptive feedback control of stability with circumferential inlet distortion has been experimentally investigated in a low-speed,axial compressor.The flat-baffles with different span heights are used to simulate different distorted inflow cases.Compared with auto-correlation and root-mean-square analysis,cross-correlation analysis used to predict early stall warning does not depend on the distortion position.Hence,the cross-correlation coefficient was used to monitor the stable status of the compressor and provide the feedback signal in the active control strategy when suffering from different distortions.Based on the stall margin improvement of tip air injection obtained under different distorted inflow cases and the sensitivity analysis of cross-correlation coefficients to injected momentum ratios,tip air injection was adopted as the actuator for adaptive feedback control.The digital signal processing controller was designed and applied to achieve adaptive feedback control in distorted inflow conditions.The results show that the adaptive feedback control of air injection nearly achieves the same stall margin improvement as steady air injection under different distortion intensities with a reduced injection mass flow.Thus,the proposed adaptive feedback control method is ideal for the engine operation with circumferential distorted inflow,which frequently occurs in flight.展开更多
A stall diagnosis method based on the entropy feature extraction algorithm is developed in axial compressors.The reliability of the proposed method is determined and a parametric sensitivity analysis is experimentally...A stall diagnosis method based on the entropy feature extraction algorithm is developed in axial compressors.The reliability of the proposed method is determined and a parametric sensitivity analysis is experimentally conducted for two different types of compressor stall diagnoses.A collection of time‐resolved pressure sensors is mounted circumferentially and along the chord direction to measure the dynamic pressure on the casing.Results show that the stall and prestall precursor embedded in the dynamic pressures are identified through nonlinear feature perturbation extraction using the entropy feature extraction algorithm.Further analysis demonstrates that the prestall precursor with the peak entropy value is related to the unsteady tip leakage flow for the spike‐type stall diagnosis.The modal wave inception with increasing amplitude is identified by the considerable increase of the entropy value.The flow field in the tip region indicates that the modal wave corresponds to the flow separation in the suction side of the rotor blade.The warning time is 100–300 rotor revolutions for both types of stall diagnoses,which is beneficial for stall control in different axial compressors.Moreover,a parametric study of the embedding dimension m,similar tolerance n,similar radius r,and data length N in the fuzzy entropy method is conducted to determine the optimal parameter setting for stall diagnosis.The stall warning based on the entropy feature extraction algorithm provides a new stall diagnosis approach in the axial compressor with different stall types.This stall warning can also be adopted as an online stability monitoring index when using the concept of active stall control.展开更多
According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be desig...According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.展开更多
This paper describes the effects of non-equilibrium air plasma generated by a dielectric barrier discharge (DBD) on the combustion of low heating value fuels. The experimental results indicate that addition of a very ...This paper describes the effects of non-equilibrium air plasma generated by a dielectric barrier discharge (DBD) on the combustion of low heating value fuels. The experimental results indicate that addition of a very small amount of energy to the air flow in the form of DBD significantly improves the flame stability. Moreover, main combustion characteristics such as flame propagation speed, combustion intensity and lean blow-off limits are also enhanced by the effect of plasma. Some active radicals such as excited O atom and excited N2 molecule are observed by spectrograph in the discharge area. Based on the results of numerical investigation we can conclude that these active radicals generated in discharge area can accelerate the production rate of active OH radical which plays a key role in the oxidation process of low heating value fuel, and thus the whole combustion process is accelerated.展开更多
Based on the simplified format of the Reynolds stress equations,a fire-new rotational-modification method for the anisotropic turbulence model has been presented.A three-dimensional Navier-Stokes code with this new ro...Based on the simplified format of the Reynolds stress equations,a fire-new rotational-modification method for the anisotropic turbulence model has been presented.A three-dimensional Navier-Stokes code with this new rotational modified k-ω turbulence models(β=0.1 and β=1) and the standard k-ω turbulence model have been used for the prediction of flow and heat transfer characteristics in a rotating smooth square channel.The Reynolds number Re based on the inlet velocity of the cooling air and hydraulic diameter is 6000.The rotating speed are 300,600,900,1200rpm respectively.The calculations results of using three turbulence models have been compared with the experimental data.The research results show that(1) the rotational modification coefficient Rf13 used in the new anisotropic k-ω model would increased/decreased the predictions of heat transfer on the trailing surface/leading surface compared to the standard k-ω model.And this tendency would be increased with the increased β.(2) The simulation performance of the standard k-ω model was well on the leading surface.However,on the trailing surface it under-predicted the heat transfer at high rotating speed.(3) The calculation results of the new anisotropic k-ω model with β=0.1 proposed by the present paper agreed well with experimental data,both on the leading and trailing surfaces.Besides,compared to 1,0.1 is a more appropriate magnitude of β at conditions in the present paper.展开更多
The present study focused on the development of a full-scale gas turbine combustor burning syn-gas from the coal-based multi-production. The dynamic features of a variety of parameters of the combustor, such as temper...The present study focused on the development of a full-scale gas turbine combustor burning syn-gas from the coal-based multi-production. The dynamic features of a variety of parameters of the combustor, such as temperature and pressure during the procedures of startup and thermal load shifting, were measured and analyzed. The frequency and power spectrum of pressure fluctuation were analyzed by applying FFT and 1D continuous MORLET wavelet methods. The results show that the pressure fluctuation has distinct patterns during startup and load-transition procedures. The relationship between these dynamic features and the stability, safety and efficiency of gas turbine combustors burning syn-gas are preliminarily discussed.展开更多
The inlet attack angle of rotor blade reasonably can be adjusted with the change of the stagger angle of inlet guide vane (IGV); so the efficiency of each condition will be affected. For the purpose to improve the eff...The inlet attack angle of rotor blade reasonably can be adjusted with the change of the stagger angle of inlet guide vane (IGV); so the efficiency of each condition will be affected. For the purpose to improve the efficiency, the DSP (Digital Signal Processor) controller is designed to adjust the stagger angle of IGV automatically in order to optimize the efficiency at any operating condition. The A/D signal collection includes inlet static pressure, outlet static pressure, outlet total pressure, rotor speed and torque signal, the efficiency can be calculated in the DSP, and the angle signal for the stepping motor which control the IGV will be sent out from the D/A. Experimental investigations are performed in a three-stage, low-speed axial compressor with variable inlet guide vanes. It is demonstrated that the DSP designed can well adjust the stagger angle of IGV online, the efficiency under different conditions can be optimized. This establishment of DSP online adjustment scheme may provide a practical solution for improving performance of multi-stage axial flow compressor when its operating condition is varied.展开更多
The DLE (dry low emission) technology has already been used on industrial gas turbine combustor and the NO X emission can be limited to 25 ppmv (@15% O 2 ), but one of the destructive effects is combustion instability...The DLE (dry low emission) technology has already been used on industrial gas turbine combustor and the NO X emission can be limited to 25 ppmv (@15% O 2 ), but one of the destructive effects is combustion instability. In this paper, the dynamic and emission characteristics of a DLE gas turbine combustor have been researched in the authors' laboratory, and the results show that the key source of combustion instability is the non-uniformity of fuel in the flame zone. Two main fuel supply methods have been used to form different fuel distribution types; it is shown that in the perfectly premixed case the emission level is low and combustion process is stable. The PPF also has an obvious effect on the combustor's emission and dynamic characteristics.展开更多
The stall behavior in a single-stage low-speed axial compressor under rotating inlet distortion (RID) is investigatedin the first half of this paper. The tests demonstrate that the tip leakage flow (TLF) plays an impo...The stall behavior in a single-stage low-speed axial compressor under rotating inlet distortion (RID) is investigatedin the first half of this paper. The tests demonstrate that the tip leakage flow (TLF) plays an important rolein triggering rotating stall. The tracking of the spike-like disturbances caused by the spillage of TLV indicates thatmost of such spike-like disturbances will be smeared by non-distorted sector and the growth of the spike-like disturbancesactually relate closely to how and how often the path of the propagating disturbances come across thepath of the rotating distorted sector. In the second half of this paper, micro air injections are applied to test the effectbehavior of TLF on stall inception. Contrasts to without micro air injections, the spike-like disturbances aremuch fewer, so the possibilities that spike-like disturbances may trigger rotating stall are fewer too. As a result,the compressor gets a lower mass flow rate at stall for both co-rotating inlet distortion and counter-rotating inletdistortion.展开更多
A new anisotropic k-o turbulence model was proposed in this paper.This new model,with the standard k-o model and the standard k-e model was embedded in our three-dimensional(3-D)Navier-Stokes code to compute rotationa...A new anisotropic k-o turbulence model was proposed in this paper.This new model,with the standard k-o model and the standard k-e model was embedded in our three-dimensional(3-D)Navier-Stokes code to compute rotational film cooling.In addition,the theoretical and numerical analysis on the influence of the Coriolis and buoyancy forces induced by the rotation was discussed in detail.Major findings of this study are as follows:⑴The new anisotropic k-o model preformed much better compared to its isotropic counterparts.(2)In the region of 6D-12D downstream the film hole,the numerical results of the new model were much closer to the experimental data than that in the region of 0-6D.(3)The constant density term can be balanced by the pressure gradient and would not influence the velocity and temperature distributions.But the centrifugal buoyancy force and the Coriolis force would change the trajectory of cooling air and temperature distributions.展开更多
基金co-supported by the National Natural Science Foundation of China(No.51922098)the National Science and Technology Major Project of China(No.2017-Ⅱ-0004-0017)the Special Fund for the Member of Youth Innovation Promotion Association of CAS(No.2018173).
文摘The adaptive feedback control of stability with circumferential inlet distortion has been experimentally investigated in a low-speed,axial compressor.The flat-baffles with different span heights are used to simulate different distorted inflow cases.Compared with auto-correlation and root-mean-square analysis,cross-correlation analysis used to predict early stall warning does not depend on the distortion position.Hence,the cross-correlation coefficient was used to monitor the stable status of the compressor and provide the feedback signal in the active control strategy when suffering from different distortions.Based on the stall margin improvement of tip air injection obtained under different distorted inflow cases and the sensitivity analysis of cross-correlation coefficients to injected momentum ratios,tip air injection was adopted as the actuator for adaptive feedback control.The digital signal processing controller was designed and applied to achieve adaptive feedback control in distorted inflow conditions.The results show that the adaptive feedback control of air injection nearly achieves the same stall margin improvement as steady air injection under different distortion intensities with a reduced injection mass flow.Thus,the proposed adaptive feedback control method is ideal for the engine operation with circumferential distorted inflow,which frequently occurs in flight.
基金National Natural Science Foundation of China,Grant/Award Number:51922098,51727810National Science and TechnologyMajor Project of China,Grant/Award Number:J2019‐II‐0020‐0041Special Fund for the Member of Youth Innovation Promotion Association of Chinese Academy of Sciences,Grant/Award Number:2018173。
文摘A stall diagnosis method based on the entropy feature extraction algorithm is developed in axial compressors.The reliability of the proposed method is determined and a parametric sensitivity analysis is experimentally conducted for two different types of compressor stall diagnoses.A collection of time‐resolved pressure sensors is mounted circumferentially and along the chord direction to measure the dynamic pressure on the casing.Results show that the stall and prestall precursor embedded in the dynamic pressures are identified through nonlinear feature perturbation extraction using the entropy feature extraction algorithm.Further analysis demonstrates that the prestall precursor with the peak entropy value is related to the unsteady tip leakage flow for the spike‐type stall diagnosis.The modal wave inception with increasing amplitude is identified by the considerable increase of the entropy value.The flow field in the tip region indicates that the modal wave corresponds to the flow separation in the suction side of the rotor blade.The warning time is 100–300 rotor revolutions for both types of stall diagnoses,which is beneficial for stall control in different axial compressors.Moreover,a parametric study of the embedding dimension m,similar tolerance n,similar radius r,and data length N in the fuzzy entropy method is conducted to determine the optimal parameter setting for stall diagnosis.The stall warning based on the entropy feature extraction algorithm provides a new stall diagnosis approach in the axial compressor with different stall types.This stall warning can also be adopted as an online stability monitoring index when using the concept of active stall control.
基金supported by the National Natural Science Foundation of China(Grant No.51010007)China Scholarship Council(CSC)
文摘According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.
基金supported by National Natural Science Foundation of China with project No.50976116 and No.51076150
文摘This paper describes the effects of non-equilibrium air plasma generated by a dielectric barrier discharge (DBD) on the combustion of low heating value fuels. The experimental results indicate that addition of a very small amount of energy to the air flow in the form of DBD significantly improves the flame stability. Moreover, main combustion characteristics such as flame propagation speed, combustion intensity and lean blow-off limits are also enhanced by the effect of plasma. Some active radicals such as excited O atom and excited N2 molecule are observed by spectrograph in the discharge area. Based on the results of numerical investigation we can conclude that these active radicals generated in discharge area can accelerate the production rate of active OH radical which plays a key role in the oxidation process of low heating value fuel, and thus the whole combustion process is accelerated.
文摘Based on the simplified format of the Reynolds stress equations,a fire-new rotational-modification method for the anisotropic turbulence model has been presented.A three-dimensional Navier-Stokes code with this new rotational modified k-ω turbulence models(β=0.1 and β=1) and the standard k-ω turbulence model have been used for the prediction of flow and heat transfer characteristics in a rotating smooth square channel.The Reynolds number Re based on the inlet velocity of the cooling air and hydraulic diameter is 6000.The rotating speed are 300,600,900,1200rpm respectively.The calculations results of using three turbulence models have been compared with the experimental data.The research results show that(1) the rotational modification coefficient Rf13 used in the new anisotropic k-ω model would increased/decreased the predictions of heat transfer on the trailing surface/leading surface compared to the standard k-ω model.And this tendency would be increased with the increased β.(2) The simulation performance of the standard k-ω model was well on the leading surface.However,on the trailing surface it under-predicted the heat transfer at high rotating speed.(3) The calculation results of the new anisotropic k-ω model with β=0.1 proposed by the present paper agreed well with experimental data,both on the leading and trailing surfaces.Besides,compared to 1,0.1 is a more appropriate magnitude of β at conditions in the present paper.
文摘The present study focused on the development of a full-scale gas turbine combustor burning syn-gas from the coal-based multi-production. The dynamic features of a variety of parameters of the combustor, such as temperature and pressure during the procedures of startup and thermal load shifting, were measured and analyzed. The frequency and power spectrum of pressure fluctuation were analyzed by applying FFT and 1D continuous MORLET wavelet methods. The results show that the pressure fluctuation has distinct patterns during startup and load-transition procedures. The relationship between these dynamic features and the stability, safety and efficiency of gas turbine combustors burning syn-gas are preliminarily discussed.
基金supported by National Basic Research Program of China 2007CB210104National Natural Science Foundation of China with projects No.51010007.and No.50736007
文摘The inlet attack angle of rotor blade reasonably can be adjusted with the change of the stagger angle of inlet guide vane (IGV); so the efficiency of each condition will be affected. For the purpose to improve the efficiency, the DSP (Digital Signal Processor) controller is designed to adjust the stagger angle of IGV automatically in order to optimize the efficiency at any operating condition. The A/D signal collection includes inlet static pressure, outlet static pressure, outlet total pressure, rotor speed and torque signal, the efficiency can be calculated in the DSP, and the angle signal for the stepping motor which control the IGV will be sent out from the D/A. Experimental investigations are performed in a three-stage, low-speed axial compressor with variable inlet guide vanes. It is demonstrated that the DSP designed can well adjust the stagger angle of IGV online, the efficiency under different conditions can be optimized. This establishment of DSP online adjustment scheme may provide a practical solution for improving performance of multi-stage axial flow compressor when its operating condition is varied.
基金supported by the National Natural Science Foundation of China(No.50976116and No.50806077)
文摘The DLE (dry low emission) technology has already been used on industrial gas turbine combustor and the NO X emission can be limited to 25 ppmv (@15% O 2 ), but one of the destructive effects is combustion instability. In this paper, the dynamic and emission characteristics of a DLE gas turbine combustor have been researched in the authors' laboratory, and the results show that the key source of combustion instability is the non-uniformity of fuel in the flame zone. Two main fuel supply methods have been used to form different fuel distribution types; it is shown that in the perfectly premixed case the emission level is low and combustion process is stable. The PPF also has an obvious effect on the combustor's emission and dynamic characteristics.
基金The support of National Natural Science Foundation of China through Grant 50676094 and 50736007 are gratefully acknowledged.
文摘The stall behavior in a single-stage low-speed axial compressor under rotating inlet distortion (RID) is investigatedin the first half of this paper. The tests demonstrate that the tip leakage flow (TLF) plays an important rolein triggering rotating stall. The tracking of the spike-like disturbances caused by the spillage of TLV indicates thatmost of such spike-like disturbances will be smeared by non-distorted sector and the growth of the spike-like disturbancesactually relate closely to how and how often the path of the propagating disturbances come across thepath of the rotating distorted sector. In the second half of this paper, micro air injections are applied to test the effectbehavior of TLF on stall inception. Contrasts to without micro air injections, the spike-like disturbances aremuch fewer, so the possibilities that spike-like disturbances may trigger rotating stall are fewer too. As a result,the compressor gets a lower mass flow rate at stall for both co-rotating inlet distortion and counter-rotating inletdistortion.
文摘A new anisotropic k-o turbulence model was proposed in this paper.This new model,with the standard k-o model and the standard k-e model was embedded in our three-dimensional(3-D)Navier-Stokes code to compute rotational film cooling.In addition,the theoretical and numerical analysis on the influence of the Coriolis and buoyancy forces induced by the rotation was discussed in detail.Major findings of this study are as follows:⑴The new anisotropic k-o model preformed much better compared to its isotropic counterparts.(2)In the region of 6D-12D downstream the film hole,the numerical results of the new model were much closer to the experimental data than that in the region of 0-6D.(3)The constant density term can be balanced by the pressure gradient and would not influence the velocity and temperature distributions.But the centrifugal buoyancy force and the Coriolis force would change the trajectory of cooling air and temperature distributions.