In this paper,the kerosene/air rotating detonation engines(RDE)are numerically investigated,and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE inc...In this paper,the kerosene/air rotating detonation engines(RDE)are numerically investigated,and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE including the initiation,instabilities,and propulsive performance.A hybrid MPI t OpenMP parallel computing model is applied and it is proved to be able to obtain a more effective parallel performance on high performance computing(HPC)systems.A series of cases with the total pressure of 1 MPa,1.5 MPa,2 MPa,and the equivalence ratio of 0.9,1,1.4 are simulated.On one hand,the total pressure shows a significant impact on the instabilities of rotating detonation waves.The instability phenomenon is observed in cases with low total pressure(1 MPa)and weakened with the increase of the total pressure.The total pressure has a small impact on the detonation wave velocity and the specific impulse.On the other hand,the equivalence ratio shows a negligible influence on the instabilities,while it affects the ignition process and accounts for the detonation velocity deficit.It is more difficult to initiate rotating detonation waves directly in the lean fuel operation condition.Little difference was observed in the thrust with different equivalence ratios of 0.9,1,and 1.4.The highest specific impulse was obtained in the lean fuel cases,which is around 2700 s.The findings could provide insights into the understanding of the operation characteristics of kerosene/air RDE.展开更多
Inlet total pressure distortion has great adverse effects on the aero-engine performance. The distorted flow passes through the compressor and becomes non-uniform in the downstream blade rows. Different from previous ...Inlet total pressure distortion has great adverse effects on the aero-engine performance. The distorted flow passes through the compressor and becomes non-uniform in the downstream blade rows. Different from previous studies based on the assumption of circumferential uniformity, this study aims to improve circumferential non-uniform flow with the non-axisymmetric structure. Non-axisymmetric stator clearance was adopted to resolve the effects of non-uniform flow caused by inlet total pressure distortion in this paper. The 9 stators with tip clearance were installed in the distorted region and the flow field structure and performance under different operating conditions was studied. The study finds that the non-axisymmetric compressor with 9 tip clearance stators can ensure compressor efficiency while improving compressor stability margin. What’s more, the separation range and strength in the distorted region can be reduced significantly and the anti-distortion capability of compressor can be enhanced.展开更多
The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have fo...The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have focused on constant pressure models, constant static pressure models and pressure loss models. However, low model precision is a common disadvantage when simulating engine exhaust manifolds, particularly for turbocharged systems. To study the performance of junction flow, a cold wind tunnel experiment with high velocities at the junction of a diesel exhaust manifold is performed, and the variation in the pressure loss in the T-junction under different flow conditions is obtained. Despite the trend of the calculated total pressure loss coefficient, which is obtained by using the original pressure loss model and is the same as that obtained from the experimental results, large differences exist between the calculated and experimental values. Furthermore, the deviation becomes larger as the flow velocity increases. By improving the Vazsonyi formula considering the flow velocity and introducing the distribution function, a modified pressure loss model is established, which is suitable for a higher velocity range. Then, the new model is adopted to solve one-dimensional, unsteady flow in a D6114 turbocharged diesel engine. The calculated values are compared with the measured data, and the result shows that the simulation accuracy of the pressure wave before the turbine is improved by 4.3% with the modified pressure loss model because gas compressibility is considered when the flow velocities are high. The research results provide valuable information for further junction flow research, particularly the correction of the boundary condition in one-dimensional simulation models.展开更多
Transverse pressure gradient(TPG)is one of the key factors influencing the boundary layer airflow diversion in a bump inlet.This paper proposes a novel TPG-based hypersonic bump inlet design method.This method consist...Transverse pressure gradient(TPG)is one of the key factors influencing the boundary layer airflow diversion in a bump inlet.This paper proposes a novel TPG-based hypersonic bump inlet design method.This method consists of two steps.First,a parametric optimization approach is employed to design a series of 2D inlets with various compression efficiencies.Then,according to the prescribed TPG,the optimized inlets are placed in different osculating planes to generate a 3D bump inlet.This method provides a means to directly control the aerodynamic parameters of the bump rather than the geometric parameters.By performing this method to a hypersonic chin inlet,a long and wide bump surface is formed in the compression wall,which leads to good integration of the bump/inlet.Results show that a part of the near-wall boundary layer flow is diverted by the bump,resulting in a slight decrease in the mass flow but a significant improvement in the total pressure recovery.In addition,the starting ability is significantly improved by adding the bump surface.Analysis reveals that the bump has a 3D rebuilding effect on the large-scale separation bubble of the unstarted inlet.Finally,a mass flow correction is performed on the designed bump inlet to increase the mass flow to full airflow capture.The results show that the mass flow rate of the corrected bump inlet reaches up to 0.9993,demonstrating that the correction method is effective.展开更多
Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length...Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.展开更多
This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-ho...This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-hole probe at exit Mach numbers of 0.10, 0.14 and 0.19. At each exit Mach number, experiments are performed at the tip clearance heights of 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of the blade height. The effects of the non-uniform tip clearance height of each blade in the pitchwise direction are also studied. The results show that at a given tip clearance height, generally, total pressure loss rises with exit Mach numbers proportionally. At a fixed exit Mach number, the total pressure loss augments nearly proportionally as the tip clearance height increases. The increased tip clearance heights in the tip regions of two adjacent blades are to be blame for the larger clearance loss of the center blade. Compared to the effects of the tip clearance height, the effects of the exit Mach number and the pitchwise variation of the tip clearance height on the cascade total pressure loss are so less significant to be omitted.展开更多
An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from ...An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from 0~135°are presented in this paper. The static pressure distributions along the duct, distortions of the flow field at the outlet section and total pressure recovery coefficients are measured and analyzed. The results show that this type of inlet has high total pressure recovery coefficients at a wide range of yaw angle. The regions of local flow separation and distortion are closely related to the yaw angle. It′s also found that the outlet section has the best characteristics at sideslip, and sharply deteriorated characteristics at the yawed flight with a yaw angle of more than 90°展开更多
Inlet distortion is one of the main factors for the degradation of aerodynamic performance and stability margin of the compressor in practical operation. Due to the change of the inlet shape and the large amount of in...Inlet distortion is one of the main factors for the degradation of aerodynamic performance and stability margin of the compressor in practical operation. Due to the change of the inlet shape and the large amount of inhalation of the body Boundary Layer, the ducted thrust fan of the Boundary Layer Ingestion (BLI) propulsion system inevitably works in the intake distortion condition. In this paper, the ducted thrust fan in a BLI propulsion system is taken as the research object. The influence of radial and circumferential total pressure distortion on the inlet section of the ducted thrust fan caused by boundary layer suction and inlet shape is studied by steady single channel and fullloop numerical simulation. The influence law of distortion intensity and distortion range of the two types of distortion patterns of the distortion map is analyzed emphatically. The results show that :(1) the greater the range and intensity of the radial total pressure distortion are, the more affected the performance of the ducted thrust fan is;(2) The aero-dynamic performance decline amplitude of the ducted thrust fan increases with the increase of the intensity of the circumferential total pressure distortion;The transmission law of the circumferential total pressure distortion intensity along the inlet and outlet of the fan is almost the same. Different working conditions have influence on the attenuation degree of the circumferential total pressure distortion in the ducted thrust fan, and the attenuation range of the circumferential total pressure distortion in the design working condition is the largest.展开更多
In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pr...In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pressure distribution measurement along the wall, the flow separation is found at the top wall of the second S duct for the baseline inlet design, which yields a high flow distortion at the exit plane. To improve the flow uniformity, a single array of vortex generators （VGs） is employed within the inlet. In this experimental study, the effects of mass flow ratio, free stream Mach number, angle of attack and yaw on the performance of a serpentine inlet instrumented with VGs are obtained. Results indicate： （1） Compared with the baseline serpentine design without flow control, the application of the VGs promotes the mixing of core flow and the low momentum flow in the boundary layer and thus prevents the flow separation. Under the design condition, the exit flow distortion （-↑△σ0） decreases from 11.7% to 2.3% by using the VGs. （2） With the descent of the free stream Mach number the total pressure loss decreases. However, the circular total pressure distortion increases. When the angle of attack rises from - 4° to 8°, the total pressure recovery and the circular total pressure distortion both go down. In addition, with the increase of yaw the total pressure recovery is fairly constant, while the circular total pressure distortion ascends gradually. （3） When Mao = 0.6-0.8, a = -4°-8° and β = 0°-6°, the total pressure recovery varies between 0.936 and 0. 961, the circular total pressure distortion coefficient varies between 1.4 % and 5.4 % and the synthesis distortion coefficient has a ranges from 3.8 % to 7.0 %. The experimental results confirm the excellent performance of the newly designed serpentine inlet incorporating VGs.展开更多
In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the t...In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the total pressure distribution at the exit of the inlet, the structure of the inner flow and the effects of the boundary layer along the fuselage on the performance of the inlet. Moreover, in comparison with the experimental data at different angles of attack, yaws and mass flow ratios, the reliabilities of the computational fluid dynamics（CFD） studied are verified. Results indicate： （1） the CFD results agree well with the experiment results and the relative errors of the total pressure coefficient is less than 1% ; （2） at the inlet＇s exit, the contour of total pressure obtained by CFD is similar to the experiment result except the contour in the low total pressure zone in CFD is slightly larger; （3） the secondary flow at the cross section behave as two counter-rotating vortices. Along the flow direction, the fields influenced by the vortex pair transport downstream and expand to the whole section at the exit; （4） the total pressure loss at the exit of the submerged inlet can be divided into external loss and internal loss. Usually, the external loss is greater than the internal loss, and both decrease with the augment of the Mach number at the exit. In addition, when the angle of attack ranges from -2° to 8°, the total pressure coefficient ascends gradually, due to the reduction of the external loss caused by the less boundary layer flow captured and the invisible change of the internal loss.展开更多
An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular c...An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.展开更多
The performance of compact,aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow ...The performance of compact,aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow distortions at the duct exit.An experimental investigation was conducted to study the flow field and passive suppression of flow separation and Aerodynamic Interface Plane (AIP) distortion in a serpentine air inlet duct.Tests were performed by a turbofan engine at several Engine Operating Points (EOPs) from 56%(idle) to 100%(max).A large total pressure deficit region arose at the upper part of the AIP,which was associated with the upper surface flow separation.Using the new mechanical S-type vortex generators in two longitudinal positions (VGl and VG2),separation and loss were diminished at the upper part of the duct and AIP.The VG2 arrangement attained the maximum reductions in distortion coefficients which were 73.72%,60.7% and 37.8% in DC(90°),DC(60°) and△P_C/P metrics,respectively.In the next step of the study,some unsteady aspects of the flow field were analyzed inside the duct.The separation onset and reattachment points were determined by the standard deviation of static pressure on the upper surface.The AIP spectral distribution showed that the boundary of low pressure and high pressure recovery regions was dominated by the maximum fluctuations.Furthermore,the PSD diagram of several probes at AIP revealed the vortex shedding frequency and its higher harmonics at separation region.The energy content of distinct unsteady spectral features in the bare configuration was significantly reduced using VGs,which showed the improvement of flow at the duct exit.展开更多
To overcome the limitations posed by three-dimensional corner separation,this paper proposes a novel flow control technology known as passive End-Wall(EW)self-adaptive jet.Two single EW slotted schemes(EWS1 and EWS2),...To overcome the limitations posed by three-dimensional corner separation,this paper proposes a novel flow control technology known as passive End-Wall(EW)self-adaptive jet.Two single EW slotted schemes(EWS1 and EWS2),alongside a combined(COM)scheme featuring double EW slots,were investigated.The results reveal that the EW slot,driven by pressure differentials between the pressure and suction sides,can generate an adaptive jet with escalating velocity as the operational load increases.This high-speed jet effectively re-excites the local low-energy fluid,thereby mitigating the corner separation.Notably,the EWS1 slot,positioned near the blade leading edge,exhibits relatively low jet velocities at negative incidence angles,causing jet separation and exacerbating the corner separation.Besides,the EWS2 slot is close to the blade trailing edge,resulting in massive low-energy fluid accumulating and separating before the slot outlet at positive incidence angles.In contrast,the COM scheme emerges as the most effective solution for comprehensive corner separation control.It can significantly reduce the total pressure loss and improve the static pressure coefficient for the ORI blade at 0°-4° incidence angles,while causing minimal negative impact on the aerodynamic performance at negative incidence angles.Therefore,the corner stall is delayed,and the available incidence angle range is broadened from -10°--2°to -10°-4°.This holds substantial promise for advancing the aerodynamic performance,operational stability,and load capacity of future highly loaded compressors.展开更多
In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions...In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions with respect to the main blade have been used to reduce such losses and improve the efficiency of the outlet guide vane(OGV).Three different relative positions have been considered assuming a NACA 65-010 profile for both the main blade and the splitter.The numerical results indicate that splitters can effectively reduce the total pressure loss by suppressing the secondary flow around the main blade,but the splitters themselves also produce flow losses,which are caused by flow separation effects.展开更多
Aiming at the problem that the total pressure loss of the flue of the electric precipitator of the 350 MW unit of a power plant to the inlet of the draft fan is too large,the numerical simulation software Fluent and t...Aiming at the problem that the total pressure loss of the flue of the electric precipitator of the 350 MW unit of a power plant to the inlet of the draft fan is too large,the numerical simulation software Fluent and the standard k-εmodel was used to simulate the flue,the results show that the main part of the flue mean total pressure loss is derived from the confluence header and elbow.In order to reduce the loss and consider the cost of transformation,the concept of twodimensional feature surface is established,gradually proposed three sets of flue transformation program and analysis of the flue transformation program drag reduction effect,the results show that the total reduction of the flue can be reduced from 486 Pa to 89 Pa and the reduction rate is 81.7%,which is the best solution;The concept of two-dimensional feature plane is helpful for quick condensing of flue;Double V-type structure of the convergence of the box has a better drag reduction effect.展开更多
Significant aerodynamic engine instability can occur during the operation of marine gas turbines as airflow enters the compressor through a 90°turning and causes inlet distortion.This study adopts the method of s...Significant aerodynamic engine instability can occur during the operation of marine gas turbines as airflow enters the compressor through a 90°turning and causes inlet distortion.This study adopts the method of simulating board equivalence to provide the target distortion flow field for ship compressors.The characteristics of the flow field behind the simulated board are obtained through experiments and numerical simulations,through which the relationship between the height of the simulated board and the total pressure distortion is elucidated.Subsequently,the study summarizes the prediction formula to achieve a distortion prediction of 0.8%–7.8%.In addition,this work analyzes the effects of drilling methods and diameters on flow nonuniformity by drilling holes into the simulation board.The results indicate that drilling holes on the board can weaken the nonuniformity of the flow field within a certain range and change the distribution pattern of total pressure in the cross-section.Furthermore,the total pressure distortion no longer changes significantly when the number of holes is too large.The proposed double simulation board structure is capable of obtaining the following two types of distorted flow fields:symmetrical dual lowpressure zones and low-pressure zones with high distortion intensity at the compressor inlet.The distortion equivalent simulation method proposed in this work can obtain various types of distortion spectra,thereby meeting the distortion parameter requirements for the antidistortion testing of marine engines.展开更多
In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out...In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out.Firstly,based on the introduction of the theoretical knowledge involved in aircraft maneuvering flight,parameters such as aircraft attitude and engine mass flow etc.required for the aerodynamic performance calculation of CK drone aircraft air inlet are determined.By analyzing the test data of WP6 engine inlet distortion simulation board,the typical indexes are extracted as the basis for evaluating the air inlet performance of CK drone aircraft.Then,the aerodynamic characteristics of the inlet of CK drone aircraft under different maneuvering conditions are numerically studied,and the total pressure recovery coefficient and pressure distortion index of the outlet section are obtained.Several conclusions and suggestions are formed after the study.When CK drone aircraft flies at positive angle of attack,the inlet has good aerodynamic characteristics,which can meet the requirements of engine intake during high maneuverable flight.In the flight of negative angle of attack,the total pressure loss and pressure distortion at the outlet section of air inlet increase sharply,which cannot guarantee the stable working of the engine.On the premise that the aircraft attitude is satisfied,CK drone aircraft can use three engine thrust states of"Rated","Modified rated"and"Maximum"for high maneuverable flight.展开更多
The article presents the results of a study of changes in the parameters of the flow, velocity and pressure of air along the cotton transportation line in pneumatic transport installations and their dependence on the ...The article presents the results of a study of changes in the parameters of the flow, velocity and pressure of air along the cotton transportation line in pneumatic transport installations and their dependence on the parameters of the pipeline. The purpose of the research is to theoretically substantiate the choice of the pipeline diameter depending on the properties of the material (cotton), the required processing capacity and pipeline throughput. In the research, an analytical method was used to study changes in the pressure of the air flow along the transportation line at different pipeline diameters. It is established that, according to the existing calculation method, the flow pressure along the transportation line is reduced to zero. At the same time, various scientists have proposed various analytical and empirical dependencies, which, in turn, give different ideas about the resistance of the inner surface of the pipes to the movement of air and material flow and do not describe the real situation, especially when transporting material from a long distance. This requires in-depth theoretical and applied research to establish real patterns of changes in flow parameters along the material (cotton) transportation line.展开更多
Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by us...Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by using the partition splicing grid technology.Used the Reynolds⁃averaged of N⁃S equation,the Reynolds stress term uses the RNG turbulence model;and based on the slip grid method,numerical calculation of the flow field with different Mach numbers,front and rear blade angles and engine state were carried out;and the change law of propeller fan characteristics and the influence of slip flow on the inlet flow field were analyzed.The blade angle was the key parameter of the propeller fan characteristic conditions.When the blade angle increases from 41°to 50°,the thrust coefficient increases by 31.2%,and the power coefficient increases by 33.4%;in the climbing state of the propeller fan,the maximum total pressure distortion at the inlet port of 6.8%;the cross section is less affected by the slip flow of the propfan;and the pressure distribution is relatively uniform,but the area of the flow channel is small.The research results can provide a solution for the matching of the counter⁃rotating propeller fan and the engine and the arrangement of the air inlet measuring rake.展开更多
A low mass flux steam jet in subcooled water was experimentally investigated.The transition of flow pattern from stable jet to condensation oscillation was observed at relatively high water temperature.The axial total...A low mass flux steam jet in subcooled water was experimentally investigated.The transition of flow pattern from stable jet to condensation oscillation was observed at relatively high water temperature.The axial total pressures,the axial and radial temperature distributions were measured in the jet region.The results indicated that the pressure and temperature distributions were mainly influenced by the water temperature.The correlations corrected with water temperature were given to predict the dimen-sionless axial pressure peak distance and axial temperature distributions in the jet region,the results showed a good agreement between the predictions and experiments.Moreover,the self-similarity property of the radial temperature was obtained,which agreed well with Gauss distribution.In present work,all the dimensionless properties were mainly dependent on the water temperature but weakly on the nozzle size under a certain steam mass flux.展开更多
基金The authors would like to acknowledge the National Natural Science Foundation of China(Grant Nos.11802137,11702143)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX19_0292)+1 种基金the Natural Science Foundation for Young Scientists of Jiangsu Province of China(Grant No.BK20190468)the Fundamental Research Funds for the Central Universities(Grant Nos.30918011343,30919011259,309190112A1).
文摘In this paper,the kerosene/air rotating detonation engines(RDE)are numerically investigated,and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE including the initiation,instabilities,and propulsive performance.A hybrid MPI t OpenMP parallel computing model is applied and it is proved to be able to obtain a more effective parallel performance on high performance computing(HPC)systems.A series of cases with the total pressure of 1 MPa,1.5 MPa,2 MPa,and the equivalence ratio of 0.9,1,1.4 are simulated.On one hand,the total pressure shows a significant impact on the instabilities of rotating detonation waves.The instability phenomenon is observed in cases with low total pressure(1 MPa)and weakened with the increase of the total pressure.The total pressure has a small impact on the detonation wave velocity and the specific impulse.On the other hand,the equivalence ratio shows a negligible influence on the instabilities,while it affects the ignition process and accounts for the detonation velocity deficit.It is more difficult to initiate rotating detonation waves directly in the lean fuel operation condition.Little difference was observed in the thrust with different equivalence ratios of 0.9,1,and 1.4.The highest specific impulse was obtained in the lean fuel cases,which is around 2700 s.The findings could provide insights into the understanding of the operation characteristics of kerosene/air RDE.
基金supported by the National Natural Science Foundation of China(No.51576024,51436002)the Double First Class Construction Special Innovation Project of Dalian Maritime University(No.BSCXXM008)。
文摘Inlet total pressure distortion has great adverse effects on the aero-engine performance. The distorted flow passes through the compressor and becomes non-uniform in the downstream blade rows. Different from previous studies based on the assumption of circumferential uniformity, this study aims to improve circumferential non-uniform flow with the non-axisymmetric structure. Non-axisymmetric stator clearance was adopted to resolve the effects of non-uniform flow caused by inlet total pressure distortion in this paper. The 9 stators with tip clearance were installed in the distorted region and the flow field structure and performance under different operating conditions was studied. The study finds that the non-axisymmetric compressor with 9 tip clearance stators can ensure compressor efficiency while improving compressor stability margin. What’s more, the separation range and strength in the distorted region can be reduced significantly and the anti-distortion capability of compressor can be enhanced.
文摘The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have focused on constant pressure models, constant static pressure models and pressure loss models. However, low model precision is a common disadvantage when simulating engine exhaust manifolds, particularly for turbocharged systems. To study the performance of junction flow, a cold wind tunnel experiment with high velocities at the junction of a diesel exhaust manifold is performed, and the variation in the pressure loss in the T-junction under different flow conditions is obtained. Despite the trend of the calculated total pressure loss coefficient, which is obtained by using the original pressure loss model and is the same as that obtained from the experimental results, large differences exist between the calculated and experimental values. Furthermore, the deviation becomes larger as the flow velocity increases. By improving the Vazsonyi formula considering the flow velocity and introducing the distribution function, a modified pressure loss model is established, which is suitable for a higher velocity range. Then, the new model is adopted to solve one-dimensional, unsteady flow in a D6114 turbocharged diesel engine. The calculated values are compared with the measured data, and the result shows that the simulation accuracy of the pressure wave before the turbine is improved by 4.3% with the modified pressure loss model because gas compressibility is considered when the flow velocities are high. The research results provide valuable information for further junction flow research, particularly the correction of the boundary condition in one-dimensional simulation models.
基金the National Natural Science Foundation of China(No.12102470)the Hunan Provincial Innovation Foundation for Postgraduate(No.CX20200082),China。
文摘Transverse pressure gradient(TPG)is one of the key factors influencing the boundary layer airflow diversion in a bump inlet.This paper proposes a novel TPG-based hypersonic bump inlet design method.This method consists of two steps.First,a parametric optimization approach is employed to design a series of 2D inlets with various compression efficiencies.Then,according to the prescribed TPG,the optimized inlets are placed in different osculating planes to generate a 3D bump inlet.This method provides a means to directly control the aerodynamic parameters of the bump rather than the geometric parameters.By performing this method to a hypersonic chin inlet,a long and wide bump surface is formed in the compression wall,which leads to good integration of the bump/inlet.Results show that a part of the near-wall boundary layer flow is diverted by the bump,resulting in a slight decrease in the mass flow but a significant improvement in the total pressure recovery.In addition,the starting ability is significantly improved by adding the bump surface.Analysis reveals that the bump has a 3D rebuilding effect on the large-scale separation bubble of the unstarted inlet.Finally,a mass flow correction is performed on the designed bump inlet to increase the mass flow to full airflow capture.The results show that the mass flow rate of the corrected bump inlet reaches up to 0.9993,demonstrating that the correction method is effective.
文摘Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.
基金National Natural Science Foundation of China (10377011)
文摘This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-hole probe at exit Mach numbers of 0.10, 0.14 and 0.19. At each exit Mach number, experiments are performed at the tip clearance heights of 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of the blade height. The effects of the non-uniform tip clearance height of each blade in the pitchwise direction are also studied. The results show that at a given tip clearance height, generally, total pressure loss rises with exit Mach numbers proportionally. At a fixed exit Mach number, the total pressure loss augments nearly proportionally as the tip clearance height increases. The increased tip clearance heights in the tip regions of two adjacent blades are to be blame for the larger clearance loss of the center blade. Compared to the effects of the tip clearance height, the effects of the exit Mach number and the pitchwise variation of the tip clearance height on the cascade total pressure loss are so less significant to be omitted.
文摘An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from 0~135°are presented in this paper. The static pressure distributions along the duct, distortions of the flow field at the outlet section and total pressure recovery coefficients are measured and analyzed. The results show that this type of inlet has high total pressure recovery coefficients at a wide range of yaw angle. The regions of local flow separation and distortion are closely related to the yaw angle. It′s also found that the outlet section has the best characteristics at sideslip, and sharply deteriorated characteristics at the yawed flight with a yaw angle of more than 90°
基金National Natural Science Foundation of China(No.51706183,No.51790512)。
文摘Inlet distortion is one of the main factors for the degradation of aerodynamic performance and stability margin of the compressor in practical operation. Due to the change of the inlet shape and the large amount of inhalation of the body Boundary Layer, the ducted thrust fan of the Boundary Layer Ingestion (BLI) propulsion system inevitably works in the intake distortion condition. In this paper, the ducted thrust fan in a BLI propulsion system is taken as the research object. The influence of radial and circumferential total pressure distortion on the inlet section of the ducted thrust fan caused by boundary layer suction and inlet shape is studied by steady single channel and fullloop numerical simulation. The influence law of distortion intensity and distortion range of the two types of distortion patterns of the distortion map is analyzed emphatically. The results show that :(1) the greater the range and intensity of the radial total pressure distortion are, the more affected the performance of the ducted thrust fan is;(2) The aero-dynamic performance decline amplitude of the ducted thrust fan increases with the increase of the intensity of the circumferential total pressure distortion;The transmission law of the circumferential total pressure distortion intensity along the inlet and outlet of the fan is almost the same. Different working conditions have influence on the attenuation degree of the circumferential total pressure distortion in the ducted thrust fan, and the attenuation range of the circumferential total pressure distortion in the design working condition is the largest.
文摘In order to provide the line-of-sight blockage of the engine face for an advanced Uninhabited Combat Air Vehicle（UCAV）, a highly curved serpentine inlet is proposed and experimentally studied. Based on the static pressure distribution measurement along the wall, the flow separation is found at the top wall of the second S duct for the baseline inlet design, which yields a high flow distortion at the exit plane. To improve the flow uniformity, a single array of vortex generators （VGs） is employed within the inlet. In this experimental study, the effects of mass flow ratio, free stream Mach number, angle of attack and yaw on the performance of a serpentine inlet instrumented with VGs are obtained. Results indicate： （1） Compared with the baseline serpentine design without flow control, the application of the VGs promotes the mixing of core flow and the low momentum flow in the boundary layer and thus prevents the flow separation. Under the design condition, the exit flow distortion （-↑△σ0） decreases from 11.7% to 2.3% by using the VGs. （2） With the descent of the free stream Mach number the total pressure loss decreases. However, the circular total pressure distortion increases. When the angle of attack rises from - 4° to 8°, the total pressure recovery and the circular total pressure distortion both go down. In addition, with the increase of yaw the total pressure recovery is fairly constant, while the circular total pressure distortion ascends gradually. （3） When Mao = 0.6-0.8, a = -4°-8° and β = 0°-6°, the total pressure recovery varies between 0.936 and 0. 961, the circular total pressure distortion coefficient varies between 1.4 % and 5.4 % and the synthesis distortion coefficient has a ranges from 3.8 % to 7.0 %. The experimental results confirm the excellent performance of the newly designed serpentine inlet incorporating VGs.
文摘In order to get a deep insight of a submerged inlet on the plane surface, the integrated flow field of the inlet and fuselage has been numerically studied. The investigation is mainly focused on the formation of the total pressure distribution at the exit of the inlet, the structure of the inner flow and the effects of the boundary layer along the fuselage on the performance of the inlet. Moreover, in comparison with the experimental data at different angles of attack, yaws and mass flow ratios, the reliabilities of the computational fluid dynamics（CFD） studied are verified. Results indicate： （1） the CFD results agree well with the experiment results and the relative errors of the total pressure coefficient is less than 1% ; （2） at the inlet＇s exit, the contour of total pressure obtained by CFD is similar to the experiment result except the contour in the low total pressure zone in CFD is slightly larger; （3） the secondary flow at the cross section behave as two counter-rotating vortices. Along the flow direction, the fields influenced by the vortex pair transport downstream and expand to the whole section at the exit; （4） the total pressure loss at the exit of the submerged inlet can be divided into external loss and internal loss. Usually, the external loss is greater than the internal loss, and both decrease with the augment of the Mach number at the exit. In addition, when the angle of attack ranges from -2° to 8°, the total pressure coefficient ascends gradually, due to the reduction of the external loss caused by the less boundary layer flow captured and the invisible change of the internal loss.
文摘An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.
文摘The performance of compact,aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow distortions at the duct exit.An experimental investigation was conducted to study the flow field and passive suppression of flow separation and Aerodynamic Interface Plane (AIP) distortion in a serpentine air inlet duct.Tests were performed by a turbofan engine at several Engine Operating Points (EOPs) from 56%(idle) to 100%(max).A large total pressure deficit region arose at the upper part of the AIP,which was associated with the upper surface flow separation.Using the new mechanical S-type vortex generators in two longitudinal positions (VGl and VG2),separation and loss were diminished at the upper part of the duct and AIP.The VG2 arrangement attained the maximum reductions in distortion coefficients which were 73.72%,60.7% and 37.8% in DC(90°),DC(60°) and△P_C/P metrics,respectively.In the next step of the study,some unsteady aspects of the flow field were analyzed inside the duct.The separation onset and reattachment points were determined by the standard deviation of static pressure on the upper surface.The AIP spectral distribution showed that the boundary of low pressure and high pressure recovery regions was dominated by the maximum fluctuations.Furthermore,the PSD diagram of several probes at AIP revealed the vortex shedding frequency and its higher harmonics at separation region.The energy content of distinct unsteady spectral features in the bare configuration was significantly reduced using VGs,which showed the improvement of flow at the duct exit.
基金sponsored by the National Natural Science Foundation of China(No.52106057)the National Major Science and Technology Projects of China(No.2017-Ⅱ-0001-0013)+2 种基金Fundamental Research Funds for the Central Universities of China(No.D5000210483)the Foundation of State Level Key Laboratory of Airfoil and Cascade Aerodynamics of China(Nos.D5150210006 and D5050210015)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University of China(No.CX2023012).
文摘To overcome the limitations posed by three-dimensional corner separation,this paper proposes a novel flow control technology known as passive End-Wall(EW)self-adaptive jet.Two single EW slotted schemes(EWS1 and EWS2),alongside a combined(COM)scheme featuring double EW slots,were investigated.The results reveal that the EW slot,driven by pressure differentials between the pressure and suction sides,can generate an adaptive jet with escalating velocity as the operational load increases.This high-speed jet effectively re-excites the local low-energy fluid,thereby mitigating the corner separation.Notably,the EWS1 slot,positioned near the blade leading edge,exhibits relatively low jet velocities at negative incidence angles,causing jet separation and exacerbating the corner separation.Besides,the EWS2 slot is close to the blade trailing edge,resulting in massive low-energy fluid accumulating and separating before the slot outlet at positive incidence angles.In contrast,the COM scheme emerges as the most effective solution for comprehensive corner separation control.It can significantly reduce the total pressure loss and improve the static pressure coefficient for the ORI blade at 0°-4° incidence angles,while causing minimal negative impact on the aerodynamic performance at negative incidence angles.Therefore,the corner stall is delayed,and the available incidence angle range is broadened from -10°--2°to -10°-4°.This holds substantial promise for advancing the aerodynamic performance,operational stability,and load capacity of future highly loaded compressors.
基金the Natural Science Foundation from Hubei Province of China[Grant No.2019CFC866]the Guiding Project of Scientific Research Plan of Hubei Education Department of China[Grant No.B2020227]+2 种基金the Collaborative Innovation Team of Discipline Characteristics of Jianghan University[Grant No.03100061]the Research Start-up Funds of Jianghan University[Grant No.101906320001]and the Research Start-up Funds of Jianghan University[101906270002].
文摘In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions with respect to the main blade have been used to reduce such losses and improve the efficiency of the outlet guide vane(OGV).Three different relative positions have been considered assuming a NACA 65-010 profile for both the main blade and the splitter.The numerical results indicate that splitters can effectively reduce the total pressure loss by suppressing the secondary flow around the main blade,but the splitters themselves also produce flow losses,which are caused by flow separation effects.
文摘Aiming at the problem that the total pressure loss of the flue of the electric precipitator of the 350 MW unit of a power plant to the inlet of the draft fan is too large,the numerical simulation software Fluent and the standard k-εmodel was used to simulate the flue,the results show that the main part of the flue mean total pressure loss is derived from the confluence header and elbow.In order to reduce the loss and consider the cost of transformation,the concept of twodimensional feature surface is established,gradually proposed three sets of flue transformation program and analysis of the flue transformation program drag reduction effect,the results show that the total reduction of the flue can be reduced from 486 Pa to 89 Pa and the reduction rate is 81.7%,which is the best solution;The concept of two-dimensional feature plane is helpful for quick condensing of flue;Double V-type structure of the convergence of the box has a better drag reduction effect.
基金Supported by the National Natural Science Foundation of China(No.52101348)the National Science and Technology Major Project(Y2019-VIII-0013-0174)the Fundamental Research Funds for the Central Universities(No.3072022JC0301)。
文摘Significant aerodynamic engine instability can occur during the operation of marine gas turbines as airflow enters the compressor through a 90°turning and causes inlet distortion.This study adopts the method of simulating board equivalence to provide the target distortion flow field for ship compressors.The characteristics of the flow field behind the simulated board are obtained through experiments and numerical simulations,through which the relationship between the height of the simulated board and the total pressure distortion is elucidated.Subsequently,the study summarizes the prediction formula to achieve a distortion prediction of 0.8%–7.8%.In addition,this work analyzes the effects of drilling methods and diameters on flow nonuniformity by drilling holes into the simulation board.The results indicate that drilling holes on the board can weaken the nonuniformity of the flow field within a certain range and change the distribution pattern of total pressure in the cross-section.Furthermore,the total pressure distortion no longer changes significantly when the number of holes is too large.The proposed double simulation board structure is capable of obtaining the following two types of distorted flow fields:symmetrical dual lowpressure zones and low-pressure zones with high distortion intensity at the compressor inlet.The distortion equivalent simulation method proposed in this work can obtain various types of distortion spectra,thereby meeting the distortion parameter requirements for the antidistortion testing of marine engines.
基金supported by the Fundamental Research Funds for the Central Universities(No.56XCA2004806)。
文摘In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out.Firstly,based on the introduction of the theoretical knowledge involved in aircraft maneuvering flight,parameters such as aircraft attitude and engine mass flow etc.required for the aerodynamic performance calculation of CK drone aircraft air inlet are determined.By analyzing the test data of WP6 engine inlet distortion simulation board,the typical indexes are extracted as the basis for evaluating the air inlet performance of CK drone aircraft.Then,the aerodynamic characteristics of the inlet of CK drone aircraft under different maneuvering conditions are numerically studied,and the total pressure recovery coefficient and pressure distortion index of the outlet section are obtained.Several conclusions and suggestions are formed after the study.When CK drone aircraft flies at positive angle of attack,the inlet has good aerodynamic characteristics,which can meet the requirements of engine intake during high maneuverable flight.In the flight of negative angle of attack,the total pressure loss and pressure distortion at the outlet section of air inlet increase sharply,which cannot guarantee the stable working of the engine.On the premise that the aircraft attitude is satisfied,CK drone aircraft can use three engine thrust states of"Rated","Modified rated"and"Maximum"for high maneuverable flight.
文摘The article presents the results of a study of changes in the parameters of the flow, velocity and pressure of air along the cotton transportation line in pneumatic transport installations and their dependence on the parameters of the pipeline. The purpose of the research is to theoretically substantiate the choice of the pipeline diameter depending on the properties of the material (cotton), the required processing capacity and pipeline throughput. In the research, an analytical method was used to study changes in the pressure of the air flow along the transportation line at different pipeline diameters. It is established that, according to the existing calculation method, the flow pressure along the transportation line is reduced to zero. At the same time, various scientists have proposed various analytical and empirical dependencies, which, in turn, give different ideas about the resistance of the inner surface of the pipes to the movement of air and material flow and do not describe the real situation, especially when transporting material from a long distance. This requires in-depth theoretical and applied research to establish real patterns of changes in flow parameters along the material (cotton) transportation line.
文摘Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by using the partition splicing grid technology.Used the Reynolds⁃averaged of N⁃S equation,the Reynolds stress term uses the RNG turbulence model;and based on the slip grid method,numerical calculation of the flow field with different Mach numbers,front and rear blade angles and engine state were carried out;and the change law of propeller fan characteristics and the influence of slip flow on the inlet flow field were analyzed.The blade angle was the key parameter of the propeller fan characteristic conditions.When the blade angle increases from 41°to 50°,the thrust coefficient increases by 31.2%,and the power coefficient increases by 33.4%;in the climbing state of the propeller fan,the maximum total pressure distortion at the inlet port of 6.8%;the cross section is less affected by the slip flow of the propfan;and the pressure distribution is relatively uniform,but the area of the flow channel is small.The research results can provide a solution for the matching of the counter⁃rotating propeller fan and the engine and the arrangement of the air inlet measuring rake.
基金Supported by the National Natural Science Foundation of China(Grant Nos.50676078,50821064)the National High-Tech Research and Development Program of China("863" Project)(Grant No.2006AA05Z230)
文摘A low mass flux steam jet in subcooled water was experimentally investigated.The transition of flow pattern from stable jet to condensation oscillation was observed at relatively high water temperature.The axial total pressures,the axial and radial temperature distributions were measured in the jet region.The results indicated that the pressure and temperature distributions were mainly influenced by the water temperature.The correlations corrected with water temperature were given to predict the dimen-sionless axial pressure peak distance and axial temperature distributions in the jet region,the results showed a good agreement between the predictions and experiments.Moreover,the self-similarity property of the radial temperature was obtained,which agreed well with Gauss distribution.In present work,all the dimensionless properties were mainly dependent on the water temperature but weakly on the nozzle size under a certain steam mass flux.
