Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well ...Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well understood.In this paper,the complex flow field in the hub endwall of a cantilevered compressor cascade has been investigated through numerical approach.The predicted results were validated by experimental data.To highlight the dominant flow structures among irregular and chaotic motions of various vortices,a Dynamic Mode Decomposition(DMD)method was utilized.The results show that there exist three dominant periodic flow structures:the oscillation of the leakage vortex,a circumferential migration of a Breakdown Induced Vortex(BIV)and the fluctuation of the passage vortex.These three coherent structures all together form a self-sustained closed loop which accounts for the flow unsteadiness of the studied cascade.During this process,the BIV plays a key role in inducing the flow unsteadiness.Only if the BIV is strong enough to affect the passage vortex,the flow unsteadiness occurs.This study expands current knowledge base of flow unsteadiness in a compressor environment,and shows the efficacy of the DMD method for revealing the origin of flow unsteadiness.展开更多
The effects of Reynolds number on the compressor efficiency are investigated by tests on three highlyloaded 10-stage axial compressors.The tests are conducted by adjusting the inlet total pressure,and thus different R...The effects of Reynolds number on the compressor efficiency are investigated by tests on three highlyloaded 10-stage axial compressors.The tests are conducted by adjusting the inlet total pressure,and thus different Reynolds numbers are obtained.The results indicate that the compressor efficiency decreases when the Reynolds number decreases.Based on the test results,reasonable correlations between the Reynolds number and compressor efficiency for each of the three compressors are obtained.The comparison between the test result-deduced correlations and Wassell correlations indicates that the effects of Reynolds number on the efficiency predicted by the Wassell correlations are less than those obtained by the test result-deduced correlations.Owing to the complex loss models and flow behavior in highly-loaded multi-stage compressors,additional influence factors,including the tip clearance and the compressor inlet duct design,should be considered for performance correlations.Nevertheless,the Wassell correlations are valid for the tendency prediction of performance changes relating to the Reynolds number,while accurate correlations still largely depend on the specific test results.展开更多
Aircraft engines deteriorate during continuous operation under the action of external factors including fouling, corrosion, and abrasion. The increased surface roughness of compressor passage walls limits airflow and ...Aircraft engines deteriorate during continuous operation under the action of external factors including fouling, corrosion, and abrasion. The increased surface roughness of compressor passage walls limits airflow and leads to flow loss. However, the partial increase of roughness may also restrain flow separation and reduce flow loss. It is necessary to explore methods that will lower compressor deterioration, thereby improving the overall performance. The experimental research on the effects of surface roughness on highly loaded compressor cascade aerodynamics has been conducted in a low-speed linear cascade wind tunnel. The different levels of roughness are arranged on the suction surface and pressure surface, respectively. Ink-trace flow visualization has been used to measure the flow field on the walls of cascades, and a five-hole probe has been traversed across one pitch at the outlet. By comparing the total pressure loss coefficient, the distributions of the secondary-flow speed vector, and flow fields of various cases, the effects of surface roughness on the aerodynamics of a highly loaded compressor cascade are analyzed and discussed. The results show that adding surface roughness on the suction surface and pressure surface make the loss decrease in most cases. Increasing the surface roughness on the suction surface causes reduced flow speed near the blade, which helps to decrease mixing loss at the cascades outlet. Meanwhile, adding surface roughness on the suction surface restrains flow separation, leading to less flow loss. Various levels of surface roughness mostly weaken the flow turning capacity to various degrees, except in specific cases.展开更多
To predict stall and surge in advance that make the aero-engine compressor operatesafely,a stall prediction model based on deep learning theory is established in the current study.The Long Short-Term Memory(LSTM)origi...To predict stall and surge in advance that make the aero-engine compressor operatesafely,a stall prediction model based on deep learning theory is established in the current study.The Long Short-Term Memory(LSTM)originating from the recurrent neural network is used,and a set of measured dynamic pressure datasets including the stall process is used to learn whatdetermines the weight of neural network nodes.Subsequently,the structure and function hyperpa-rameters in the model are deeply optimized,and a set of measured pressure data is used to verify theprediction effects of the model.On this basis of the above good predictive capability,stall in low-and high-speed compressor are predicted by using the established model.When a period of non-stallpressure data is used as input in the model,the model can quickly complete the prediction of sub-sequent time series data through the self-learning and prediction mechanism.Comparison with thereal-time measured pressure data demonstrates that the starting point of the predicted stall is basi-cally the same as that of the measured stall,and the stall can be predicted more than 1 s in advanceso that the occurrence of stall can be avoided.The model of stall prediction in the current study canmake up for the uncertainty of threshold selection of the existing stall warning methods based onmeasured data signal processing.It has a great application potential to predict the stall occurrenceof aero-engine compressor in advance and avoid the accidents.展开更多
Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held ...Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held by GREE and Hefei General Machinery Research Institute Co.,Ltd.in Zhuhai,South China’s Guangdong province on June 12.展开更多
Nondestructive testing(NDT)methods such as visual inspection and ultrasonic testing are widely applied in manufacturing quality control,but they remain limited in their ability to detect defect characteristics.Visual ...Nondestructive testing(NDT)methods such as visual inspection and ultrasonic testing are widely applied in manufacturing quality control,but they remain limited in their ability to detect defect characteristics.Visual inspection depends strongly on operator experience,while ultrasonic testing requires physical contact and stable coupling conditions that are difficult to maintain in production lines.These constraints become more pronounced when defect-related information is scarce or when background noise interferes with signal acquisition in manufacturing processes.This study presents a non-contact acoustic method for diagnosing defects in scroll compressors during the manufacturing process.The diagnostic approach leverages Mel-frequency cepstral coefficients(MFCC),and shorttime Fourier transform(STFT)parameters to capture the rotational frequency and harmonic characteristics of the scroll compressor.These parameters enable the extraction of defect-related features even in the presence of background noise.A convolutional neural network(CNN)model was constructed using MFCCs and spectrograms as image inputs.The proposed method was validated using acoustic data collected from compressors operated at a fixed rotational speed under real manufacturing process.The method identified normal operation and three defect types.These results demonstrate the applicability of this method in noise-prone manufacturing environments and suggest its potential for improving product quality,manufacturing reliability and productivity.展开更多
Unstable operating conditions such as surge could cause damage to both aerodynamic performance and structural integrity of a compression system.This paper addresses the critical issue of aerodynamic instability in com...Unstable operating conditions such as surge could cause damage to both aerodynamic performance and structural integrity of a compression system.This paper addresses the critical issue of aerodynamic instability in compressor design,particularly focusing on an axial-centrifugal combined compressor,a widely used yet underexplored configuration.An experimental investigation was conducted on a three-stage axial and one-stage centrifugal compressor(3A1C),using two pipe systems and employing fast-responding transducers to capture the dynamic instability process from choke condition to deep surge.Results reveal that at the design speed,3A1C enters deep surge directly,whereas at off-design speeds,it experiences rotating stall and mild surge across a wide mass flow range.Some special instability features in the combined compressor can be found in the steady state map and dynamic process.The characteristic curve of the first axial stage keeps a positive slope during the whole mass flow range at an off-design speed.The first stage could work stably on the stall characteristic curve because the centrifugal stage has stronger pressurization and plays a dominant role in global aerodynamic instability.Besides,rotating instability occurs at the first rotor tip and disappears as the back pressure increases,which is also rarely seen in a single-axial compressor.This is also related to the strong pressurization of the centrifugal stage.The findings of this paper will contribute to the understanding of aerodynamic instabilities in combined compressors.展开更多
With the continuous increase of aeroengine flight ceiling(>20 km),the thin atmosphere at high altitudes and the size effect all cause the compressor component inlet Reynolds number to decrease rapidly to a critical...With the continuous increase of aeroengine flight ceiling(>20 km),the thin atmosphere at high altitudes and the size effect all cause the compressor component inlet Reynolds number to decrease rapidly to a critical value(approximately 2.0×10^(5)),and the significant transition process on the blade/endwall surface leads to the sharp degradation of compressor performance,which seriously affects the engine fuel consumption and working stability at high altitudes.In this paper,the research progress on the internal flow mechanism and flow control methods of axial compressors at low Reynolds numbers is reviewed from the aspects of quantification and prediction of performance variation,flow loss mechanism related to separation and transition,efficient transition control and flow field organization.The development trend of the low-Reynolds-number effect of axial flow compressors is noted,and the difficulties and application prospects of aerodynamic design and efficient flow control methods for compressors under low Reynolds numbers at high altitudes are discussed.展开更多
To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)...To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.展开更多
The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach...The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach narrows the spacing between the stator and the strut,making traditional research on transition ducts only with struts unsuitable.The numerical results and experimental oil flow visualization results were utilized to reconstruct the three-dimensional flow structures in the stator passages under various operating conditions.Additionally,numerical methods were employed to analyze the mechanisms of the strut's effect on the upstream stator in an aggressive transition duct.The results show that the strut potential field increases the load on the upstream stator,leading to severe blade surface separation and corner separation/stall,and redistributes the inflow angle of the upstream stators circumferentially,resulting in significant differences in the flow structures within the stator passages on both sides.The separation flows within the stator passages mainly manifest in five types:pressure surface separation vortex,suction surface concentrated shedding vortex,suction surface separation vortex,suction surface-corner stall separation vortex,and suction surface separation vortex pair.Under different operating conditions,the separation flows within the stator passages are always composed of a part of these five types or a transitional state between two of them.展开更多
Compressor surge is a major aerodynamic instability that constrains the performance and reliability of industrial gas turbines.To address this challenge,this paper provides a comprehensive review of recent progress in...Compressor surge is a major aerodynamic instability that constrains the performance and reliability of industrial gas turbines.To address this challenge,this paper provides a comprehensive review of recent progress in surge monitoring,modeling,and control strategies.Key difficulties in early surge detection are identified,including ambiguous precursor signals,strongly coupled system dynamics,and sensor-actuator time delays.The review categorizes existing modeling approaches into high-fidelity computational fluid dynamics(CFD),reducedorder physical models,and data-driven techniques,evaluating each in terms of accuracy,adaptability,and realtime feasibility.In terms of control strategies,both passive and active methods are analyzed,with a particular focus on closed-loop feedback,model predictive control,robust control,and intelligent data-driven approaches.The review concludes by outlining future directions that prioritize model integration,control reliability,and systemlevel coordination for enhanced compressor stability.展开更多
In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential f...In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential for enhancing the performance of such systems.This study examines the main sCO_(2) compressor from Sandia Laboratory,utilizing entropy production theory to elucidate the sources and distribution of energy losses both across the entire machine and within its key flow components.The findings reveal that turbulent viscous dissipation is the predominant contributor to total entropy production.Interestingly,while the relative importance of the entropy produced by various sources as the mass flow rate rises remains essentially unchanged,the total entropy production exhibits a nonmonotonic trend,first decreasing and then increasing with the mass flow rate.High entropy production in the impeller is primarily concentrated in the clearance region and along the rear cover of the impeller tip.In the diffuser,it is most pronounced on the front and rear plates and within the central flow path.Meanwhile,in the volute,the highest entropy production occurs around the diffuser outlet and along the outer region of the volute’s centerline.展开更多
To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-s...To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.展开更多
The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The...The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The framework is validated through the experiments of rotating inlet distortion within a low-speed compressor. The input–output method is subsequently applied to transonic compressors, including NASA Rotor37 and Stage35, wherein impedance optimization is studied along with the exploration of its fundamental mechanisms. The IBC is employed to model the effect of Casing Treatment (CT). The optimal complex impedance values are determined through predicted results and tested across a range of circumferential modes and forcing frequencies. The IBC significantly reduces the energy and Reynolds stress gain, notably at the first-order circumferential mode and within the Rotor Rotating Frequency (RRF) range. Output modes reveal that transonic compressors with fine-tuned impedance values exhibit a more confined perturbation distribution and redistribute the perturbations compared to the uncontrolled case. Additionally, the roles of resistance and reactance are elucidated through input–output analysis, and resistance determines the energy transfer direction between flow and pressure waves and modulates the amplitude, whereas reactance modifies the phase relationships and attenuates the perturbations.展开更多
This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault dia...This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault diagnosis of a reciprocating compressor(RC).Initially,raw vibration signals undergo empirical mode decomposition to break them down into multiple intrinsic mode functions(IMFs).This operation can reveal inherent vibration patterns of fault and other components hidden in the original signals.Subsequently,features are refined from all the IMFs and concatenated into a high-dimensional representative vector,offering localized and comprehensive insights into RC operation.Through DBN,the fault-sensitive information is further refined from the features to enhance their performance in fault identification.Finally,similarities among subspaces on the Grassmann manifold are computed to match fault types.The efficacy of the method is validated usingfield data.Comparative analysis with traditional approaches for feature dimension reduction,feature extraction,and Euclidean distance-based fault identification underscores the effectiveness and superiority of the proposed method in RC fault diagnosis.展开更多
Currently,the design of advanced compressor blades has reached the full ThreeDimensional(3D)modeling stage.When analyzing the reasons for the failure of popular corner stall prediction criteria for axial compressors t...Currently,the design of advanced compressor blades has reached the full ThreeDimensional(3D)modeling stage.When analyzing the reasons for the failure of popular corner stall prediction criteria for axial compressors to predict the corner flow state in modern compressor3D blades with end-bend and composite bend-sweep characteristics,it is believed that,in addition to the dihedral angle factor in the corner,the variation of the dihedral angle along the flow path is an important factor that has not been considered to date.In light of this,this study first uses the characteristic effects of the diffuser on the deceleration and pressure increase in airflow to design a series of physical models of varying dihedral angle diffusers that are equivalent to compressors.Based on these models,a quantization parameter is established to characterize the development speed of the intersection of boundary layers at the corner under varying dihedral angle and adverse pressure gradient conditions.After combining this with the effects of secondary flow,a Modified diffusion factor DJ(MDJ)is developed to describe the development of corner flow from the leading edge of the blade to its trailing edge under varying dihedral angle conditions.Finally,based on a compressor cascade database,an improved criterion for predicting corner stall in axial compressors using the MDJ diffusion factor is proposed.The validation results,based on extensive experimental data of compressor blades,reveal that this improved criterion can significantly enhance the accuracy of corner stall predictions in the 3D blades of modern compressors compared to currently used prediction criteria,by taking into account the effects of variations in the dihedral angle.展开更多
This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compresso...This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compressor impeller model is used as a reference system.Through three-dimensional numerical simulations,we examine the Mach number distribution,temperature field,blade pressure pulsation spectra,and velocity field evolution,and identify accordingly the operating boundaries ensuring stability and the mechanisms responsible for performance degradation.Findings indicate a stable operating range for mass flow rate between 0.74 and 3.74 kg/s.At the lower limit(0.74 kg/s),the maximum Mach number within the compressor decreases by 28%,while the temperature gradient sharpens,entropy rises notably,and fluid density varies significantly.The maximum pressure near the blades increases by 6%,yet flow velocity near the blades and outlet declines,with a 19%reduction in peak speed.Consequently,isentropic efficiency falls by 13%.Conversely,at 3.74 kg/s,the maximum Mach number increases by 23.7%,with diminished temperature gradients and minor fluid density variations.However,insufficient enthalpy gain and intensified pressure pulsations near the blades result in a 12%pressure drop.Peak velocity within the impeller channel surges by 23%,amplifying velocity gradients,inducing flow separation,and ultimately reducing the pressure ratio from 1.47 to 1.34.展开更多
Water management within the membrane electrode assemblies(MEAs)of electrochemical hydrogen compressors(EHCs)plays a crucial role in optimizing overall performance,particularly under low relative humidity(RH),where the...Water management within the membrane electrode assemblies(MEAs)of electrochemical hydrogen compressors(EHCs)plays a crucial role in optimizing overall performance,particularly under low relative humidity(RH),where the anode side tends to dry out.Hollow mesoporous silica nanoparticles functionalized with amino groups(HMSNs-NH_(2))were integrated into the anode catalyst layers of EHCs to establish humidity-independent proton pathways through acid-base interactions with Nafion ionomers.These acid-base pairs between grafted–NH_(2)and sulfonic acid groups create continuous“proton highways”,enabling efficient conduction via the Grotthuss mechanism even at 50%RH.With only 2.5 wt%HMSNs-NH_(2)in the anode catalyst layer,hydrogen was compressed to 0.9 MPa in 60±3 s at 50%RH,representing a 55%reduction in compression time compared to MEAs with conventional Pt/C catalyst layers under the same conditions.This work overcomes the critical water-management bottleneck in EHCs,advancing the deployment of hydrogen energy technologies in arid environments.展开更多
To assess the aerodynamic performance and vibration characteristics of rotor blades during rotation,a study of unsteady blade surface forces is conducted in a low-speed axial flow compressor under a rotating coordinat...To assess the aerodynamic performance and vibration characteristics of rotor blades during rotation,a study of unsteady blade surface forces is conducted in a low-speed axial flow compressor under a rotating coordinate system.The capture,modulation,and acquisition of unsteady blade surface forces are achieved by using pressure sensors and strain gauges attached to the rotor blades,in conjunction with a wireless telemetry system.Based on the measurement reliability verification,this approach allows for the determination of the static pressure distribution on rotor blade surfaces,enabling the quantitative description of loadability at different spanwise positions along the blade chord.Effects caused by the factors such as Tip Leakage Flow(TLF)and flow separation can be perceived and reflected in the trends of static pressure on the blade surfaces.Simultaneously,the dynamic characteristics of unsteady pressure and stress on the blade surfaces are analyzed.The results indicate that only the pressure signals measured at the mid-chord of the blade tip can distinctly detect the unsteady frequency of TLF due to the oscillation of the low-pressure spot on the pressure surface.Subsequently,with the help of one-dimensional continuous wavelet analysis method,it can be inferred that as the compressor enters stall,the sensors are capable of capturing stall cell frequency under a rotating coordinate system.Furthermore,the stress at the blade root is higher than that at the blade tip,and the frequency band of the vibration can also be measured by the pressure sensors fixed on the casing wall in a stationary frame.While the compressor stalls,the stress at the blade root can be higher,which can provide valuable guidance for monitoring the lifecycle of compressor blades.展开更多
There is introduced a new low-reaction, highly-loaded axial compressor design concept which is coupled with boundary layer suction method. The characteristic features of the concept are made clear through its comparis...There is introduced a new low-reaction, highly-loaded axial compressor design concept which is coupled with boundary layer suction method. The characteristic features of the concept are made clear through its comparison with the MIT boundary layer suction compressor. Also are pointed out the potential applications of this concept as well as its key technological problems. Based on this concept, a single-stage, low-reaction and low-speed axial compressor is constructed in association with analysis and computation of boundary layer suction on vanes with the aid of a three-dimensional numerical approach. The results attest to the effectiveness of this way to control separation in blade cascades by the boundary layer suction and the feasibility of this proposed design concept.展开更多
基金supports of National Natural Science Foundation of China(Nos.51790512,52176045)the National Major Science and technology Project of China(No.J2017-Ⅱ-0010-0024)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX201911)。
文摘Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well understood.In this paper,the complex flow field in the hub endwall of a cantilevered compressor cascade has been investigated through numerical approach.The predicted results were validated by experimental data.To highlight the dominant flow structures among irregular and chaotic motions of various vortices,a Dynamic Mode Decomposition(DMD)method was utilized.The results show that there exist three dominant periodic flow structures:the oscillation of the leakage vortex,a circumferential migration of a Breakdown Induced Vortex(BIV)and the fluctuation of the passage vortex.These three coherent structures all together form a self-sustained closed loop which accounts for the flow unsteadiness of the studied cascade.During this process,the BIV plays a key role in inducing the flow unsteadiness.Only if the BIV is strong enough to affect the passage vortex,the flow unsteadiness occurs.This study expands current knowledge base of flow unsteadiness in a compressor environment,and shows the efficacy of the DMD method for revealing the origin of flow unsteadiness.
文摘The effects of Reynolds number on the compressor efficiency are investigated by tests on three highlyloaded 10-stage axial compressors.The tests are conducted by adjusting the inlet total pressure,and thus different Reynolds numbers are obtained.The results indicate that the compressor efficiency decreases when the Reynolds number decreases.Based on the test results,reasonable correlations between the Reynolds number and compressor efficiency for each of the three compressors are obtained.The comparison between the test result-deduced correlations and Wassell correlations indicates that the effects of Reynolds number on the efficiency predicted by the Wassell correlations are less than those obtained by the test result-deduced correlations.Owing to the complex loss models and flow behavior in highly-loaded multi-stage compressors,additional influence factors,including the tip clearance and the compressor inlet duct design,should be considered for performance correlations.Nevertheless,the Wassell correlations are valid for the tendency prediction of performance changes relating to the Reynolds number,while accurate correlations still largely depend on the specific test results.
基金Financially supported from"National Natural Science Foundation of China"(Grant No.51206035)"the Foundation for Innovative Research Groups of the National Natural Science Foundation of China"(Grant No.51121004)
文摘Aircraft engines deteriorate during continuous operation under the action of external factors including fouling, corrosion, and abrasion. The increased surface roughness of compressor passage walls limits airflow and leads to flow loss. However, the partial increase of roughness may also restrain flow separation and reduce flow loss. It is necessary to explore methods that will lower compressor deterioration, thereby improving the overall performance. The experimental research on the effects of surface roughness on highly loaded compressor cascade aerodynamics has been conducted in a low-speed linear cascade wind tunnel. The different levels of roughness are arranged on the suction surface and pressure surface, respectively. Ink-trace flow visualization has been used to measure the flow field on the walls of cascades, and a five-hole probe has been traversed across one pitch at the outlet. By comparing the total pressure loss coefficient, the distributions of the secondary-flow speed vector, and flow fields of various cases, the effects of surface roughness on the aerodynamics of a highly loaded compressor cascade are analyzed and discussed. The results show that adding surface roughness on the suction surface and pressure surface make the loss decrease in most cases. Increasing the surface roughness on the suction surface causes reduced flow speed near the blade, which helps to decrease mixing loss at the cascades outlet. Meanwhile, adding surface roughness on the suction surface restrains flow separation, leading to less flow loss. Various levels of surface roughness mostly weaken the flow turning capacity to various degrees, except in specific cases.
基金funded by the National Natural Science Foundation of China(No.52376039 and U24A20138)the Beijing Natural Science Foundation of China(No.JQ24017)+1 种基金the National Science and Technology Major Project of China(Nos.J2019-II-0005-0025 and Y2022-Ⅱ-0002-0005)the Special Fund for the Member of Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2018173)。
文摘To predict stall and surge in advance that make the aero-engine compressor operatesafely,a stall prediction model based on deep learning theory is established in the current study.The Long Short-Term Memory(LSTM)originating from the recurrent neural network is used,and a set of measured dynamic pressure datasets including the stall process is used to learn whatdetermines the weight of neural network nodes.Subsequently,the structure and function hyperpa-rameters in the model are deeply optimized,and a set of measured pressure data is used to verify theprediction effects of the model.On this basis of the above good predictive capability,stall in low-and high-speed compressor are predicted by using the established model.When a period of non-stallpressure data is used as input in the model,the model can quickly complete the prediction of sub-sequent time series data through the self-learning and prediction mechanism.Comparison with thereal-time measured pressure data demonstrates that the starting point of the predicted stall is basi-cally the same as that of the measured stall,and the stall can be predicted more than 1 s in advanceso that the occurrence of stall can be avoided.The model of stall prediction in the current study canmake up for the uncertainty of threshold selection of the existing stall warning methods based onmeasured data signal processing.It has a great application potential to predict the stall occurrenceof aero-engine compressor in advance and avoid the accidents.
文摘Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held by GREE and Hefei General Machinery Research Institute Co.,Ltd.in Zhuhai,South China’s Guangdong province on June 12.
基金supported in part by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(RS-2023-00239657)in part by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.RS-2024-00423772)。
文摘Nondestructive testing(NDT)methods such as visual inspection and ultrasonic testing are widely applied in manufacturing quality control,but they remain limited in their ability to detect defect characteristics.Visual inspection depends strongly on operator experience,while ultrasonic testing requires physical contact and stable coupling conditions that are difficult to maintain in production lines.These constraints become more pronounced when defect-related information is scarce or when background noise interferes with signal acquisition in manufacturing processes.This study presents a non-contact acoustic method for diagnosing defects in scroll compressors during the manufacturing process.The diagnostic approach leverages Mel-frequency cepstral coefficients(MFCC),and shorttime Fourier transform(STFT)parameters to capture the rotational frequency and harmonic characteristics of the scroll compressor.These parameters enable the extraction of defect-related features even in the presence of background noise.A convolutional neural network(CNN)model was constructed using MFCCs and spectrograms as image inputs.The proposed method was validated using acoustic data collected from compressors operated at a fixed rotational speed under real manufacturing process.The method identified normal operation and three defect types.These results demonstrate the applicability of this method in noise-prone manufacturing environments and suggest its potential for improving product quality,manufacturing reliability and productivity.
基金supported by the National Science and Technology Major Project of China(Nos.2017-II-0004-0016 and J2019-I-0011-0011).
文摘Unstable operating conditions such as surge could cause damage to both aerodynamic performance and structural integrity of a compression system.This paper addresses the critical issue of aerodynamic instability in compressor design,particularly focusing on an axial-centrifugal combined compressor,a widely used yet underexplored configuration.An experimental investigation was conducted on a three-stage axial and one-stage centrifugal compressor(3A1C),using two pipe systems and employing fast-responding transducers to capture the dynamic instability process from choke condition to deep surge.Results reveal that at the design speed,3A1C enters deep surge directly,whereas at off-design speeds,it experiences rotating stall and mild surge across a wide mass flow range.Some special instability features in the combined compressor can be found in the steady state map and dynamic process.The characteristic curve of the first axial stage keeps a positive slope during the whole mass flow range at an off-design speed.The first stage could work stably on the stall characteristic curve because the centrifugal stage has stronger pressurization and plays a dominant role in global aerodynamic instability.Besides,rotating instability occurs at the first rotor tip and disappears as the back pressure increases,which is also rarely seen in a single-axial compressor.This is also related to the strong pressurization of the centrifugal stage.The findings of this paper will contribute to the understanding of aerodynamic instabilities in combined compressors.
基金co-supported by the National Natural Science Foundation of China(No.52306053)the Science Center for Gas Turbine Project,China(No.P2022-B-Ⅱ-005-001)the National Science and Technology Major Project of China(No.2017-Ⅱ-0010-0024)。
文摘With the continuous increase of aeroengine flight ceiling(>20 km),the thin atmosphere at high altitudes and the size effect all cause the compressor component inlet Reynolds number to decrease rapidly to a critical value(approximately 2.0×10^(5)),and the significant transition process on the blade/endwall surface leads to the sharp degradation of compressor performance,which seriously affects the engine fuel consumption and working stability at high altitudes.In this paper,the research progress on the internal flow mechanism and flow control methods of axial compressors at low Reynolds numbers is reviewed from the aspects of quantification and prediction of performance variation,flow loss mechanism related to separation and transition,efficient transition control and flow field organization.The development trend of the low-Reynolds-number effect of axial flow compressors is noted,and the difficulties and application prospects of aerodynamic design and efficient flow control methods for compressors under low Reynolds numbers at high altitudes are discussed.
文摘To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.
基金supported by the National Natural Science Foundation of China(No.52276025)the Science Center for Gas Turbine Project of China(Nos.P2022-A-Ⅱ-001-001,P2022-A-Ⅱ-002-001 and P2022-B-Ⅱ-002-001)。
文摘The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach narrows the spacing between the stator and the strut,making traditional research on transition ducts only with struts unsuitable.The numerical results and experimental oil flow visualization results were utilized to reconstruct the three-dimensional flow structures in the stator passages under various operating conditions.Additionally,numerical methods were employed to analyze the mechanisms of the strut's effect on the upstream stator in an aggressive transition duct.The results show that the strut potential field increases the load on the upstream stator,leading to severe blade surface separation and corner separation/stall,and redistributes the inflow angle of the upstream stators circumferentially,resulting in significant differences in the flow structures within the stator passages on both sides.The separation flows within the stator passages mainly manifest in five types:pressure surface separation vortex,suction surface concentrated shedding vortex,suction surface separation vortex,suction surface-corner stall separation vortex,and suction surface separation vortex pair.Under different operating conditions,the separation flows within the stator passages are always composed of a part of these five types or a transitional state between two of them.
文摘Compressor surge is a major aerodynamic instability that constrains the performance and reliability of industrial gas turbines.To address this challenge,this paper provides a comprehensive review of recent progress in surge monitoring,modeling,and control strategies.Key difficulties in early surge detection are identified,including ambiguous precursor signals,strongly coupled system dynamics,and sensor-actuator time delays.The review categorizes existing modeling approaches into high-fidelity computational fluid dynamics(CFD),reducedorder physical models,and data-driven techniques,evaluating each in terms of accuracy,adaptability,and realtime feasibility.In terms of control strategies,both passive and active methods are analyzed,with a particular focus on closed-loop feedback,model predictive control,robust control,and intelligent data-driven approaches.The review concludes by outlining future directions that prioritize model integration,control reliability,and systemlevel coordination for enhanced compressor stability.
基金supported by theDouble First-Class Key ProgramofGansu ProvincialDepartment of Education(grant number GCJ2022-38)Science and Technology Program of Gansu Province(grant number 22ZD6GA038)Key Research and Development Program of Gansu Province—Industrial Project(grant number 25YFGA021).
文摘In Brayton cycle energy storage systems powered by supercritical carbon dioxide(sCO_(2)),compressors are among themost critical components.Understanding their internal flowloss characteristics is,therefore,essential for enhancing the performance of such systems.This study examines the main sCO_(2) compressor from Sandia Laboratory,utilizing entropy production theory to elucidate the sources and distribution of energy losses both across the entire machine and within its key flow components.The findings reveal that turbulent viscous dissipation is the predominant contributor to total entropy production.Interestingly,while the relative importance of the entropy produced by various sources as the mass flow rate rises remains essentially unchanged,the total entropy production exhibits a nonmonotonic trend,first decreasing and then increasing with the mass flow rate.High entropy production in the impeller is primarily concentrated in the clearance region and along the rear cover of the impeller tip.In the diffuser,it is most pronounced on the front and rear plates and within the central flow path.Meanwhile,in the volute,the highest entropy production occurs around the diffuser outlet and along the outer region of the volute’s centerline.
基金financially supported by the National Natural Science Foundation of China(No.52176045)the National Science and Technology Major Project of China(No.J2019-I-0011-0011)。
文摘To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.
基金co-supported by the National Natural Science Foundation of China(Nos.52325602,52306036 and 52306035)the National Science and Technology Major Project of China(No.Y2022-II-0003-0006 and Y2022-II-0002-0005)+1 种基金the project funded by China Postdoctoral Science Foundation(No.2022M720346)supported by the Key Laboratory of Pre-Research Management Centre of China(No.6142702200101).
文摘The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The framework is validated through the experiments of rotating inlet distortion within a low-speed compressor. The input–output method is subsequently applied to transonic compressors, including NASA Rotor37 and Stage35, wherein impedance optimization is studied along with the exploration of its fundamental mechanisms. The IBC is employed to model the effect of Casing Treatment (CT). The optimal complex impedance values are determined through predicted results and tested across a range of circumferential modes and forcing frequencies. The IBC significantly reduces the energy and Reynolds stress gain, notably at the first-order circumferential mode and within the Rotor Rotating Frequency (RRF) range. Output modes reveal that transonic compressors with fine-tuned impedance values exhibit a more confined perturbation distribution and redistribute the perturbations compared to the uncontrolled case. Additionally, the roles of resistance and reactance are elucidated through input–output analysis, and resistance determines the energy transfer direction between flow and pressure waves and modulates the amplitude, whereas reactance modifies the phase relationships and attenuates the perturbations.
文摘This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault diagnosis of a reciprocating compressor(RC).Initially,raw vibration signals undergo empirical mode decomposition to break them down into multiple intrinsic mode functions(IMFs).This operation can reveal inherent vibration patterns of fault and other components hidden in the original signals.Subsequently,features are refined from all the IMFs and concatenated into a high-dimensional representative vector,offering localized and comprehensive insights into RC operation.Through DBN,the fault-sensitive information is further refined from the features to enhance their performance in fault identification.Finally,similarities among subspaces on the Grassmann manifold are computed to match fault types.The efficacy of the method is validated usingfield data.Comparative analysis with traditional approaches for feature dimension reduction,feature extraction,and Euclidean distance-based fault identification underscores the effectiveness and superiority of the proposed method in RC fault diagnosis.
基金co-supported by the National Natural Science Foundation of China(No.52406041)the China Postdoctoral Science Foundation(No.2025M774200)the National Science and Technology Major Project of China(No.2019-Ⅱ-0003-0023)。
文摘Currently,the design of advanced compressor blades has reached the full ThreeDimensional(3D)modeling stage.When analyzing the reasons for the failure of popular corner stall prediction criteria for axial compressors to predict the corner flow state in modern compressor3D blades with end-bend and composite bend-sweep characteristics,it is believed that,in addition to the dihedral angle factor in the corner,the variation of the dihedral angle along the flow path is an important factor that has not been considered to date.In light of this,this study first uses the characteristic effects of the diffuser on the deceleration and pressure increase in airflow to design a series of physical models of varying dihedral angle diffusers that are equivalent to compressors.Based on these models,a quantization parameter is established to characterize the development speed of the intersection of boundary layers at the corner under varying dihedral angle and adverse pressure gradient conditions.After combining this with the effects of secondary flow,a Modified diffusion factor DJ(MDJ)is developed to describe the development of corner flow from the leading edge of the blade to its trailing edge under varying dihedral angle conditions.Finally,based on a compressor cascade database,an improved criterion for predicting corner stall in axial compressors using the MDJ diffusion factor is proposed.The validation results,based on extensive experimental data of compressor blades,reveal that this improved criterion can significantly enhance the accuracy of corner stall predictions in the 3D blades of modern compressors compared to currently used prediction criteria,by taking into account the effects of variations in the dihedral angle.
基金National Science Foundation of China(grant numbers 52366009 and 52130607)Doble First-Class Key Programof Gansu Provincial Department of Education(grant number GCJ2022-38)+1 种基金2022 Gansu Provincial University Industry Support Plan Project(grant number 2022CYZC-21)KeyR&DProgramofGansu Province of China(grant number 22YF7GA163).
文摘This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compressor impeller model is used as a reference system.Through three-dimensional numerical simulations,we examine the Mach number distribution,temperature field,blade pressure pulsation spectra,and velocity field evolution,and identify accordingly the operating boundaries ensuring stability and the mechanisms responsible for performance degradation.Findings indicate a stable operating range for mass flow rate between 0.74 and 3.74 kg/s.At the lower limit(0.74 kg/s),the maximum Mach number within the compressor decreases by 28%,while the temperature gradient sharpens,entropy rises notably,and fluid density varies significantly.The maximum pressure near the blades increases by 6%,yet flow velocity near the blades and outlet declines,with a 19%reduction in peak speed.Consequently,isentropic efficiency falls by 13%.Conversely,at 3.74 kg/s,the maximum Mach number increases by 23.7%,with diminished temperature gradients and minor fluid density variations.However,insufficient enthalpy gain and intensified pressure pulsations near the blades result in a 12%pressure drop.Peak velocity within the impeller channel surges by 23%,amplifying velocity gradients,inducing flow separation,and ultimately reducing the pressure ratio from 1.47 to 1.34.
基金supported by the National Natural Science Foundation of China(No.22208376,No.UA22A20429)the Fundamental Research Funds for the Central Universities(buctrc202118,No.25CX07002A)+1 种基金the Qingdao New Energy Shandong Laboratory Open Project(QNESL OP 202303)the Shandong Provincial Natural Science Foundation(ZR2024QB175 and ZR2023LFG005)。
文摘Water management within the membrane electrode assemblies(MEAs)of electrochemical hydrogen compressors(EHCs)plays a crucial role in optimizing overall performance,particularly under low relative humidity(RH),where the anode side tends to dry out.Hollow mesoporous silica nanoparticles functionalized with amino groups(HMSNs-NH_(2))were integrated into the anode catalyst layers of EHCs to establish humidity-independent proton pathways through acid-base interactions with Nafion ionomers.These acid-base pairs between grafted–NH_(2)and sulfonic acid groups create continuous“proton highways”,enabling efficient conduction via the Grotthuss mechanism even at 50%RH.With only 2.5 wt%HMSNs-NH_(2)in the anode catalyst layer,hydrogen was compressed to 0.9 MPa in 60±3 s at 50%RH,representing a 55%reduction in compression time compared to MEAs with conventional Pt/C catalyst layers under the same conditions.This work overcomes the critical water-management bottleneck in EHCs,advancing the deployment of hydrogen energy technologies in arid environments.
基金funded by the National Natural Science Foundation of China(Nos.U24A20138 and No.52376039)the Beijing Natural Science Foundation,China(JQ24017)+1 种基金the National Science and Technology Major Project of China(Nos.J2019-II-0005-0025 and Y2022-II-0002-0005)the Special Fund for the Member of Youth Innovation Promotion Association of Chinese Academy of Sciences,China(No.2018173).
文摘To assess the aerodynamic performance and vibration characteristics of rotor blades during rotation,a study of unsteady blade surface forces is conducted in a low-speed axial flow compressor under a rotating coordinate system.The capture,modulation,and acquisition of unsteady blade surface forces are achieved by using pressure sensors and strain gauges attached to the rotor blades,in conjunction with a wireless telemetry system.Based on the measurement reliability verification,this approach allows for the determination of the static pressure distribution on rotor blade surfaces,enabling the quantitative description of loadability at different spanwise positions along the blade chord.Effects caused by the factors such as Tip Leakage Flow(TLF)and flow separation can be perceived and reflected in the trends of static pressure on the blade surfaces.Simultaneously,the dynamic characteristics of unsteady pressure and stress on the blade surfaces are analyzed.The results indicate that only the pressure signals measured at the mid-chord of the blade tip can distinctly detect the unsteady frequency of TLF due to the oscillation of the low-pressure spot on the pressure surface.Subsequently,with the help of one-dimensional continuous wavelet analysis method,it can be inferred that as the compressor enters stall,the sensors are capable of capturing stall cell frequency under a rotating coordinate system.Furthermore,the stress at the blade root is higher than that at the blade tip,and the frequency band of the vibration can also be measured by the pressure sensors fixed on the casing wall in a stationary frame.While the compressor stalls,the stress at the blade root can be higher,which can provide valuable guidance for monitoring the lifecycle of compressor blades.
基金National Defense Basic Research Program of China
文摘There is introduced a new low-reaction, highly-loaded axial compressor design concept which is coupled with boundary layer suction method. The characteristic features of the concept are made clear through its comparison with the MIT boundary layer suction compressor. Also are pointed out the potential applications of this concept as well as its key technological problems. Based on this concept, a single-stage, low-reaction and low-speed axial compressor is constructed in association with analysis and computation of boundary layer suction on vanes with the aid of a three-dimensional numerical approach. The results attest to the effectiveness of this way to control separation in blade cascades by the boundary layer suction and the feasibility of this proposed design concept.
