Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gaso...Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.展开更多
According to the production plan of the coal mine, Nanliupan region is the lower connecting curve of the mine. The mine plans to construct two air shafts (one for the air inlet shaft and one for the air return shaft) ...According to the production plan of the coal mine, Nanliupan region is the lower connecting curve of the mine. The mine plans to construct two air shafts (one for the air inlet shaft and one for the air return shaft) in Nanliupan region. Before drilling the shaft, it is necessary to construct an air shaft inspection hole. Combining with the previous geological data, the engineering geological characteristics of the air shaft are checked in advance, and the stability of the surrounding rock of the shaft is evaluated to ensure the safety of the air shaft construction.展开更多
In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, wh...In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three envelopes.Under the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.展开更多
Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise ...Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise reduction. Based upon the mode analysis method of sound propagation in a circular duct with multiple liners, a flexible tolerance method is used to optimize the acoustic parameters(impedance), geometric structure parameters(such as open area ratio, cavity depth and hole diameter) and operating condition parameters(such as blade passing frequency). The mathematical models for these kinds of optimization are presented here. The optimum values of the design variables are determined when the in-duct sound suppression approaches a maximum. It can be derived from the optimum results that the emphasis of the engineering optimization design of the perforated plate honey-comb structure should be placed on the optimum choice of the open area ratio and cavity depth. Some reference criteria for the engineering design of the multi-linings are also provided.展开更多
It is urgent to solve various problems in electromagnetic （EM） engineering under the increasingly complicated environment. Some expert systems （ES） come into being just to keep up with the demand for solving these...It is urgent to solve various problems in electromagnetic （EM） engineering under the increasingly complicated environment. Some expert systems （ES） come into being just to keep up with the demand for solving these problems. Combined with the analysis of development orES technology and the development trend of EM engineering software in recent years, the application orES technology in EM engineering is discussed, and especially the progress of complete ES in electromagnetic compatible （EMC） is introduced.展开更多
Modifying agents 2,2-Bis(4-glycidyloxyphenyl)propane(2BPE)and dibutyl phthalate(DBP)were selected to enhance the compatibility.By using molecular simulation software(Materials Studio,MS),nine systems were constructed,...Modifying agents 2,2-Bis(4-glycidyloxyphenyl)propane(2BPE)and dibutyl phthalate(DBP)were selected to enhance the compatibility.By using molecular simulation software(Materials Studio,MS),nine systems were constructed,including molecular models of aged asphalt and WVO monomers with 2BPE and/or DBP.The solubility parameters,Flory-Huggins parameters,and interaction energies of these systems were calculated to determine the impact of 2BPE and DBP on the compatibility of WVO and aged asphalt.Results showed that the addition of 2BPE and DBP reduced the difference in the solubility parameters between WVO and aged asphalt,thus improving the compatibility between WVO and aged asphalt.Additionally,using a combination of 2BPE and DBP in both aged asphalt and rejuvenator was found to be more effective than using either 2BPE or DBP alone.Finally,it was determined that evaluating the compatibility of WVO and aged asphalt using Van der Waals potential and non-bonding energy as evaluation indicators was more accurate than using electrostatic potential energy.展开更多
The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structu...The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structure and principle of EPES,three parts of the internal flow force were obtained,namely,the additional resistance before the inlet,the internal flow force in the inlet and the thrust produced by the ejector.On the assumption of one-dimensional isentropic adiabatic flow,the theoretical formulae for calculating the forces were derived according to the measured total pressure,static pressure and total temperature of the internal flow section.Subsequently,a calibration tank was used to calibrate the EPES system.On the basis of the characteristics of the EPES system,the process and method of its calibration were designed in detail,and the model installation interface of the calibration tank was reformed.By applying this method,the repeatability accuracy of the inlet flow rate calibration coefficient was less than0.05%,whereas that of the exhaust flow rate and velocity was less than 0.1%.Upon the application of the calibration coefficients to the correction of the wind tunnel experiment data,the results showed good agreement with the numerical simulation results in terms of regularity and magnitude before stall,which validates the reasonableness and feasibility of the calibration method.Analysis of the calibration data also demonstrated the consistency in the variation law and trend between the theoretical calculation and actual measurement of internal flow force,further reflecting the rationality and feasibility of the theoretical calculation.Nevertheless,the numerical difference was large and further widened with a higher ejection flow rate mainly because of the accuracy of flow measurement and the inhomogeneity of internal flow.The thrust deflection angle of EPES is an important factor in correcting this issue.In particular,the thrust deflection angle becomes larger with small ejection flow and becomes smaller with an increase in flow rate,essentially exhibiting a general change of less than 10°.展开更多
Recently, it is predicted that the fossil fuels will be sufficient for a few decades at the present extraction rates. So, the performance studies of the internal combustion engines play an important role to achieve th...Recently, it is predicted that the fossil fuels will be sufficient for a few decades at the present extraction rates. So, the performance studies of the internal combustion engines play an important role to achieve the best operating point at different weather temperatures. In the present study, the effects of the inlet air temperatures on the engine performance characteristics were studied at different cooling loads. Several experiments were carried out on a single cylinder diesel engine （SCDI）. The performance characteristics of SCDI included： brake power, specific fuel consumption, brake thermal efficiency and exhaust emissions （carbon dioxide, CO2, carbon monoxide CO, and hydrocarbon HC）. The findings show that the inlet air temperature and cooling conditions have appreciable effect on the performance characteristics of the SCDI especially at low cooling rate. It can be concluded that the high cooling rate leads to the enhancement in the brake thermal efficiency, the b.s.f.c, and the emitted COz, CO, and HC. On the other hand the high cooling rate leads to the decrease in the volumetric efficiency. So, a compromising between the inlet air temperature and the cooling rate should be recommended for the engine best performance.展开更多
Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic...Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic equations of the method are first set up, and then the mode cut-off principle and the dividing principle are proposed. MATLAB is used for simulation in different frame structures. The simulation results demonstrate the applicability of this substructure method to civil engineering structures and the correctness of the proposed mode cut-off principle. Studies are also conducted on how to divide the whole structure for better computation efficiency while maintaining better precision. It is observed that the geometry and material properties should be considered, and the synthesis results would be more precise when the inflection points of the mode shapes are taken into consideration. Furthermore, the simulation performed on a large-scale high-rise connected structure further proves the feasibility and efficiency of this modal synthesis method compared with the traditional global method. It is also concluded from the simulation results that the fewer number of DOFs in each substructure will result in better computation efficiency, but too many substructures will be time-consuming due to the tedious synthesis procedures. Moreover, the substructures with free interface will introduce errors and reduce the precision dramatically, which should be avoided.展开更多
Non-uniform inlet conditions have become increasingly important in recent years for simulating the aerodynamic performance of turbofan engine with real flight situations.This paper focuses on a particular fan and boos...Non-uniform inlet conditions have become increasingly important in recent years for simulating the aerodynamic performance of turbofan engine with real flight situations.This paper focuses on a particular fan and booster structure and employs frozen rotor interface method for 3D full-channel CFD simulation.Inlet distortion and rain ingestion are used as two representative non-uniform inlet conditions discussed in this work.It is found that the circumferential total pressure distortion develops along the flow direction,and leads to total temperature distortion.Additionally,the regulation of rain movement in fan and booster structures is investigated,and some factors about water inlet ratio impacting the performance of core engine and wet compression mechanism affecting the bypass performance are discussed.展开更多
The air intake-compression systems of modern aircraft usually use the aero-engine intake and fan/compressor as the main components.Inlet-engine compatibility has always been the key to the stable and safe operation of...The air intake-compression systems of modern aircraft usually use the aero-engine intake and fan/compressor as the main components.Inlet-engine compatibility has always been the key to the stable and safe operation of the propulsion system,including the influence of inlet distortion on the compressor performance and stall margin.Since 1950,theoretical models and experiments on the flow stability and inlet distortion of axial compressors have been released.After the 1990s,numerical methods became important tools.In the 21st century,the new trends of aircraft propulsion system/inlet integration,blended wing body,and stealth capability led to a new direction for the inlet-engine flow matching problem.This review aims to combine the development of both the inlet and the axial compressor components,and provides an overview of the research history,latest progress,and prospects of compressor inlet distortion in inlet-engine compatibility problems.Analytical or numerical models,experiments,and simulations related to inlet distortion problems are summarized.展开更多
The efficiency parameters are studied in this paper for evaluating the compression quality of the inlets with different compression degrees and assessing different design methods.Selfconsistency is proposed for the ef...The efficiency parameters are studied in this paper for evaluating the compression quality of the inlets with different compression degrees and assessing different design methods.Selfconsistency is proposed for the efficiency parameters,based on two mathematically derived efficiency parameters,entropy rise coefficient and compression quality efficiency.Two efficiency parameters are then examined for equal intensity shocks system to show their capabilities in characterizing the quality of compression system with different compression degrees,and representing the average compression efficiency of the entire inlet.And the process efficiency and compression quality efficiency are compared in the Mollier diagram to afford a clear understanding of their difference in evaluating the overall and the local compression efficiency.展开更多
There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.Th...There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.The FEM model of the bistable surface is established with hinged constraint,and the bistability condition and structural transition process are investigated in detail.Moreover,the effects of loading method,loading position and structural parameters on critical driving force,input energy and structural strain are studied.Finally,the influences of an elastic boundary condition on the structural bistability are discussed.The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snap-through phenomena during transition which are related to the loading position and structural parameters.Therefore,suitable loading position and structural material could reduce input energy and meet the demand of structural strain.展开更多
基金National Natural Science Foundation of China(50976094, 51176158)Reseach Fund for the Doctoral Program of Higher Education of China(20096102110022)Doctorate Foundation of Northwestern Polytechnical University (CX200909)
文摘Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.
文摘According to the production plan of the coal mine, Nanliupan region is the lower connecting curve of the mine. The mine plans to construct two air shafts (one for the air inlet shaft and one for the air return shaft) in Nanliupan region. Before drilling the shaft, it is necessary to construct an air shaft inspection hole. Combining with the previous geological data, the engineering geological characteristics of the air shaft are checked in advance, and the stability of the surrounding rock of the shaft is evaluated to ensure the safety of the air shaft construction.
基金supported by the Beijing Aeronautical Technology Research Center
文摘In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three envelopes.Under the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.
文摘Acoustically absorptive treatment in aircraft engine nacelle is an essential part of the overall aircraft noise reduction effort. The investigation on the optimization of multi-liners plays an important role in noise reduction. Based upon the mode analysis method of sound propagation in a circular duct with multiple liners, a flexible tolerance method is used to optimize the acoustic parameters(impedance), geometric structure parameters(such as open area ratio, cavity depth and hole diameter) and operating condition parameters(such as blade passing frequency). The mathematical models for these kinds of optimization are presented here. The optimum values of the design variables are determined when the in-duct sound suppression approaches a maximum. It can be derived from the optimum results that the emphasis of the engineering optimization design of the perforated plate honey-comb structure should be placed on the optimum choice of the open area ratio and cavity depth. Some reference criteria for the engineering design of the multi-linings are also provided.
基金the Key Project of Chinese Ministry of Education (No. 104166)
文摘It is urgent to solve various problems in electromagnetic （EM） engineering under the increasingly complicated environment. Some expert systems （ES） come into being just to keep up with the demand for solving these problems. Combined with the analysis of development orES technology and the development trend of EM engineering software in recent years, the application orES technology in EM engineering is discussed, and especially the progress of complete ES in electromagnetic compatible （EMC） is introduced.
基金Funded by the National Natural Science Foundation of China(No.52008069)。
文摘Modifying agents 2,2-Bis(4-glycidyloxyphenyl)propane(2BPE)and dibutyl phthalate(DBP)were selected to enhance the compatibility.By using molecular simulation software(Materials Studio,MS),nine systems were constructed,including molecular models of aged asphalt and WVO monomers with 2BPE and/or DBP.The solubility parameters,Flory-Huggins parameters,and interaction energies of these systems were calculated to determine the impact of 2BPE and DBP on the compatibility of WVO and aged asphalt.Results showed that the addition of 2BPE and DBP reduced the difference in the solubility parameters between WVO and aged asphalt,thus improving the compatibility between WVO and aged asphalt.Additionally,using a combination of 2BPE and DBP in both aged asphalt and rejuvenator was found to be more effective than using either 2BPE or DBP alone.Finally,it was determined that evaluating the compatibility of WVO and aged asphalt using Van der Waals potential and non-bonding energy as evaluation indicators was more accurate than using electrostatic potential energy.
基金supported by the funda-mental research the Funds of China Aerodynamics Research and Development Center
文摘The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structure and principle of EPES,three parts of the internal flow force were obtained,namely,the additional resistance before the inlet,the internal flow force in the inlet and the thrust produced by the ejector.On the assumption of one-dimensional isentropic adiabatic flow,the theoretical formulae for calculating the forces were derived according to the measured total pressure,static pressure and total temperature of the internal flow section.Subsequently,a calibration tank was used to calibrate the EPES system.On the basis of the characteristics of the EPES system,the process and method of its calibration were designed in detail,and the model installation interface of the calibration tank was reformed.By applying this method,the repeatability accuracy of the inlet flow rate calibration coefficient was less than0.05%,whereas that of the exhaust flow rate and velocity was less than 0.1%.Upon the application of the calibration coefficients to the correction of the wind tunnel experiment data,the results showed good agreement with the numerical simulation results in terms of regularity and magnitude before stall,which validates the reasonableness and feasibility of the calibration method.Analysis of the calibration data also demonstrated the consistency in the variation law and trend between the theoretical calculation and actual measurement of internal flow force,further reflecting the rationality and feasibility of the theoretical calculation.Nevertheless,the numerical difference was large and further widened with a higher ejection flow rate mainly because of the accuracy of flow measurement and the inhomogeneity of internal flow.The thrust deflection angle of EPES is an important factor in correcting this issue.In particular,the thrust deflection angle becomes larger with small ejection flow and becomes smaller with an increase in flow rate,essentially exhibiting a general change of less than 10°.
文摘Recently, it is predicted that the fossil fuels will be sufficient for a few decades at the present extraction rates. So, the performance studies of the internal combustion engines play an important role to achieve the best operating point at different weather temperatures. In the present study, the effects of the inlet air temperatures on the engine performance characteristics were studied at different cooling loads. Several experiments were carried out on a single cylinder diesel engine （SCDI）. The performance characteristics of SCDI included： brake power, specific fuel consumption, brake thermal efficiency and exhaust emissions （carbon dioxide, CO2, carbon monoxide CO, and hydrocarbon HC）. The findings show that the inlet air temperature and cooling conditions have appreciable effect on the performance characteristics of the SCDI especially at low cooling rate. It can be concluded that the high cooling rate leads to the enhancement in the brake thermal efficiency, the b.s.f.c, and the emitted COz, CO, and HC. On the other hand the high cooling rate leads to the decrease in the volumetric efficiency. So, a compromising between the inlet air temperature and the cooling rate should be recommended for the engine best performance.
基金Supported by the National Natural Science Foundation of China(No.51108089)Doctoral Programs Foundation of Ministry of Education of China(No.20113514120005)the Foundation of the Education Department of Fujian Province(No.JA14057)
文摘Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic equations of the method are first set up, and then the mode cut-off principle and the dividing principle are proposed. MATLAB is used for simulation in different frame structures. The simulation results demonstrate the applicability of this substructure method to civil engineering structures and the correctness of the proposed mode cut-off principle. Studies are also conducted on how to divide the whole structure for better computation efficiency while maintaining better precision. It is observed that the geometry and material properties should be considered, and the synthesis results would be more precise when the inflection points of the mode shapes are taken into consideration. Furthermore, the simulation performed on a large-scale high-rise connected structure further proves the feasibility and efficiency of this modal synthesis method compared with the traditional global method. It is also concluded from the simulation results that the fewer number of DOFs in each substructure will result in better computation efficiency, but too many substructures will be time-consuming due to the tedious synthesis procedures. Moreover, the substructures with free interface will introduce errors and reduce the precision dramatically, which should be avoided.
基金supported by the National Natural Science Foundation of China(No.51976116)The Open Research Subject of Key Laboratory(Fluid Machinery and Engineering Research Base)of Sichuan Province,No.szjj2019-022.
文摘Non-uniform inlet conditions have become increasingly important in recent years for simulating the aerodynamic performance of turbofan engine with real flight situations.This paper focuses on a particular fan and booster structure and employs frozen rotor interface method for 3D full-channel CFD simulation.Inlet distortion and rain ingestion are used as two representative non-uniform inlet conditions discussed in this work.It is found that the circumferential total pressure distortion develops along the flow direction,and leads to total temperature distortion.Additionally,the regulation of rain movement in fan and booster structures is investigated,and some factors about water inlet ratio impacting the performance of core engine and wet compression mechanism affecting the bypass performance are discussed.
基金supported by National Natural Science Foundation of China(52306036)Science Center for Gas Turbine Project(P2022-A-II-002-001,P2022-C-II-003-001)supported by the Key Laboratory of Pre-Research Management Centre(No.6142702200101).
文摘The air intake-compression systems of modern aircraft usually use the aero-engine intake and fan/compressor as the main components.Inlet-engine compatibility has always been the key to the stable and safe operation of the propulsion system,including the influence of inlet distortion on the compressor performance and stall margin.Since 1950,theoretical models and experiments on the flow stability and inlet distortion of axial compressors have been released.After the 1990s,numerical methods became important tools.In the 21st century,the new trends of aircraft propulsion system/inlet integration,blended wing body,and stealth capability led to a new direction for the inlet-engine flow matching problem.This review aims to combine the development of both the inlet and the axial compressor components,and provides an overview of the research history,latest progress,and prospects of compressor inlet distortion in inlet-engine compatibility problems.Analytical or numerical models,experiments,and simulations related to inlet distortion problems are summarized.
基金supported by National Natural Science Foundation of China(Nos.11672309 and 11472279)。
文摘The efficiency parameters are studied in this paper for evaluating the compression quality of the inlets with different compression degrees and assessing different design methods.Selfconsistency is proposed for the efficiency parameters,based on two mathematically derived efficiency parameters,entropy rise coefficient and compression quality efficiency.Two efficiency parameters are then examined for equal intensity shocks system to show their capabilities in characterizing the quality of compression system with different compression degrees,and representing the average compression efficiency of the entire inlet.And the process efficiency and compression quality efficiency are compared in the Mollier diagram to afford a clear understanding of their difference in evaluating the overall and the local compression efficiency.
基金supported by the National Natural Science Foundation of China(Nos.11172128,51475228)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20123218110001)+1 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanics Structures (Nanjing University of Aeronautics and Astronautics)(No.0515G01)the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Funding of Jiangsu Innovation Program for Graduate Education(the Fundamental Research Funds for the Central Universities)(No.CXZZ12_ 0139)
文摘There exists inlet-engine match conflict between high and low speeds for a non-adjustable bump inlet.A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area.The FEM model of the bistable surface is established with hinged constraint,and the bistability condition and structural transition process are investigated in detail.Moreover,the effects of loading method,loading position and structural parameters on critical driving force,input energy and structural strain are studied.Finally,the influences of an elastic boundary condition on the structural bistability are discussed.The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snap-through phenomena during transition which are related to the loading position and structural parameters.Therefore,suitable loading position and structural material could reduce input energy and meet the demand of structural strain.
