Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications a...Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications and blade clearances, and the impact on blade section and shearing force of blade clearance was analyzed. Comparing with traditional experience formulas and measured values, the limitations of the experience formulas were proved. And by contrasting with the shearing force data collected from Linfen Iron and Steel Company, the reliability of the finite element method was further proved. The simulated results show that the simulated values controlled by ductile fracture criterion and measured values are very close, and the deviation value is in the range of 4.8%-20.8%. For the same steel, if the plate is thicker, the blade clearance will be greater, and thickness and blade clearance are approximately linear. The difference between numerical simulation of the maximum shearing force and the measured results is 7.7% to 12.0%, and the simulation results are close to facts. With the increase of blade clearance and the thickness, the shearing force was increased to some degree.展开更多
Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 ...Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 international specification and GL(Germanisher Lloyd)regulations for the wind energy conversion system.Stress analysis is performed with a 3-D finite element method(FEM).Considering Saint-Venant′s principle,a uniform cross section FEM model is built at each critical zone.Stress transformation matrixes(STM)are set up by applied six unit load components on the FEM model separately.STM can be used to convert the external load into stresses in the linear elastic range.The main material of composite wind turbine blade is fiber reinforced plastics(FRP).In order to evaluate the degree of fatigue damage of FRP,the stresses of fiber direction are extracted and the well-known strength criterion-Puck theory is used.The total fatigue damage of each laminate on the critical point is counted by the rain-flow counting method and Miner′s damage law based on general S-N curves.Several sections of a 45.3mblade of a 2 MW wind turbine are studied using the fatigue evaluation method.The performance of this method is compared with far more costly business software FOCUS.The results show that the fatigue damage of multi-axis FRP can be assessed conveniently by the FEM-STM method.And the proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.展开更多
For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is develo...For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.展开更多
A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural fr...A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural frequencies and mode shapes of the blade for the helicopter are studied by using beam characteristic orthogonal polynomials by the Rayleigh-Ritz method. The variation of natural frequencies with the speed of rotation and the mode shapes at different rotational speeds are plotted. The using of orthogonal polynomials for the bending shapes enables the computation of higher natural frequencies of any order to be accomplished without facing any difficulties.展开更多
An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced ...An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced response of bladed disks in frequency domain, which is validated by numerical integration method in time domain. The resonant features of both tuned and mistuned systems are investigated by using this method under various system coupling strengths, viscous dampings, and dry friction darnpings, etc. The results demonstrate that the proposed multi-harmonic method is very efficient for studying the mistuning effects on the resonant response of bladed disks with blade-to-blade dry friction damping, especially considering the combined effects of various system parameters.展开更多
To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector mac...To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.展开更多
The doctor-blade method is investigated for the preparation of Cu2ZnSnS4 films for low-cost solar cell application. Cu2ZnSnS4 precursor powder, the main raw material for the doctor-blade paste, is synthesized by a sim...The doctor-blade method is investigated for the preparation of Cu2ZnSnS4 films for low-cost solar cell application. Cu2ZnSnS4 precursor powder, the main raw material for the doctor-blade paste, is synthesized by a simple ball-milling process. The doctor-bladed Cu2ZnSnS4 films are annealed in N2 ambient under various conditions and characterized by X-ray diffraction, ultraviolent/vis spectrophotometry, scanning electron microscopy, and current-voltage （J-V） meansurement. Our experimental results indicate that （i） the X-ray diffraction peaks of the Cu2ZnSnS4 precursor powder each show a red shift of about 0.4°; （ii） the high-temperature annealing process can effectively improve the crystallinity of the doctor-bladed Cu2ZnSnS4, whereas an overlong annealing introduces defects; （iii） the band gap value of the doctor-bladed Cu2ZnSnS4 is around 1.41 eV; （iv） the short-circuit current density, the open-circuit voltage, the fill factor, and the efficiency of the best Cu2ZnSnS4 solar cell obtained with the superstrate structure of fluorine-doped tin oxide glass/TiO2/In2S3/Cu2ZnSnS4/Mo are 7.82 mA/cm2, 240 mV, 0.29, and 0.55%, respectively.展开更多
Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the r...Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.展开更多
Based on the investigation of mid-span local boundary layer suction and positive bowed cascade, a coupled local tailored boundary layer suction and positive bowed blade method is developed to improve the performance o...Based on the investigation of mid-span local boundary layer suction and positive bowed cascade, a coupled local tailored boundary layer suction and positive bowed blade method is developed to improve the performance of a highly loaded diffusion cascade with less suction slot. The effectiveness of the coupled method under different inlet boundary layers is also investigated.Results show that mid-span local boundary layer suction can effectively remove trailing edge separation, but deteriorate the flow fields near the endwall. The positive bowed cascade is beneficial for reducing open corner separation, but is detrimental to mid-span flow fields. The coupled method can further improve the performance and flow field of the cascade. The mid-span trailing edge separation and open corner separation are eliminated. Compared with linear cascade with suction, the coupled method reduces overall loss of the cascade by 31.4% at most. The mid-span loss of the cascade decreases as the suction coefficient increases, but increases as bow angle increases. The endwall loss increases as the suction coefficient increases. By contrast, the endwall loss decreases significantly as the bow angle increases. The endwall loss of coupled controlled cascade is higher than that of bowed cascade with the same bow angle because of the spanwise inverse ‘‘C＂ shaped static pressure distribution. Under different inlet boundary layer conditions, the coupled method can also improve the cascade effectively.展开更多
Nowadays,the adjoint method has become a popular approach in the optimization of turbomachinery to further improve its aerodynamic performance.However,design variables in these adjoint optimization applications are ge...Nowadays,the adjoint method has become a popular approach in the optimization of turbomachinery to further improve its aerodynamic performance.However,design variables in these adjoint optimization applications are generally not direct design parameters of blade(such as wedge angles or maximum thickness),making the geometric variation by adjoint optimization can hardly be re-extracted as the change of each design parameter.By giving considerations to the G1 continuity constraint of adjoint method on its parameterization method,this manuscript shows how to apply a parameterization method in 3D blade design process into adjoint optimization.Nearly all design parameters can therefore be treated as design variables in the adjoint method and then participate in the sensitivity-based optimization.Finally,a fitted Rotor 67 blade is optimized and the adiabatic efficiency is significantly improved by nearly 0.91%.展开更多
Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇...Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the blade.Fatigue tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training set.Comparing with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load range.It has significant accuracy when the load is below 500 MPa.Especially,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement technology.The loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN model.The final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.展开更多
The potential hazard resulting from uncontained turbine engine rotor blade failure has always been the long-term concern of each aero engine manufacturer, and to fully contain the failed blades under critical operatin...The potential hazard resulting from uncontained turbine engine rotor blade failure has always been the long-term concern of each aero engine manufacturer, and to fully contain the failed blades under critical operating conditions is also one of the most important considerations to meet the rotor integrity requirements. Usually, there are many factors involving the engine containment capability which need to be reviewed during the engine design phases, such as case thickness, rotor support structure, blade weight and shape, etc. However, the premier method to demonstrate the engine containment capability is the fan blade-off test and margin of safety （MS） analysis. Based on a concrete engine model, this paper aims to explain the key points of aero engine containment requirements in FAR Part 33, and introduces the implementation of MS analysis and fan blade-off test in the engine airworthiness certification. Through the introduction, it would be greatly helpful to the industrial community to evaluate the engine containment capability and prepare the final test demonstration in engine certification procedure.展开更多
This paper aims to investigate the measurement uncertainty of blade surface by coordinates measuring machines (CMMs) in different sampling modes.Two different sampling methods for the blade surface, which are the para...This paper aims to investigate the measurement uncertainty of blade surface by coordinates measuring machines (CMMs) in different sampling modes.Two different sampling methods for the blade surface, which are the parallel mode and the rotation mode, are studied to examine their measurement uncertainty.The fundamental principles and operational processes of the two modes are presented and discussed.The measurements were performed on a twisted-face blade, and data processing was also conducted to fit the cross-section profile both of the base surface and back surface separately.Then the measurement uncertainties of two sampling methods were evaluated on different parts of the blade surface in terms of the surface profile’s curvature and twist rate.It is found that the measurement of blade surface by CMMs shows much uncertainty for both of the sampling modes because of the complexity of the blade surface.The back surface’s measurement uncertainty is larger than that of the base surface.The measurement uncertainty of cross-section profiles on the top blade surface is larger than that of the bottom blade surface.In addition, the difference between the measurement uncertainties of two sampling methods is small, especially for the base blade surface.The research means that both sampling methods can be a practical application choice for the measurement of blade surface by CMMs.展开更多
In this paper,stress states under corresponding condition of an aero-engine fan blade using finite element stress-strain analysis for three work cycles in the 900 h load spectrum are obtained.Through the nominal stres...In this paper,stress states under corresponding condition of an aero-engine fan blade using finite element stress-strain analysis for three work cycles in the 900 h load spectrum are obtained.Through the nominal stress method,we calculated the fatigue notch factor and combined the material characteristics of TC6 to correct the material curve to the fan blades curve. Finally,the fatigue life of a fan blade was estimated using the linear cumulative damage rule and nonlinear cumulative damage theory.展开更多
Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade wi...Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade with a tenon as an object, the influence of process parameters on the temperature distribution in precision forging process was investigated using 3D coupled thermo-mechanical FEM （finite element method） code developed by the authors. The results obtained illustrate that： （1） the gradient of temperature distribution increases with increasing the deformation degree; （2） with increasing the initial temperature of the billet, the zones of high temperature become larger, and the gradient of temperature distribution hardly has any increase; （3） friction factors have little effect on the distribution of temperature field; （4） with increasing upper die velocity, temperature of the billet increases while the temperature gradient in billet decreases. The results are helpful to the design and optimization of the process parameters in precision forging process of Ti-alloy blade.展开更多
Several structural design parameters for the description of the geometric features of a hollow fan blade were determined.A structural design optimization model of a hollow fan blade which based on the strength constra...Several structural design parameters for the description of the geometric features of a hollow fan blade were determined.A structural design optimization model of a hollow fan blade which based on the strength constraint and minimum mass was established based on the finite element method through these parameters.Then,the sequential quadratic programming algorithm was employed to search the optimal solutions.Several groups of value for initial design variables were chosen,for the purpose of not only finding much more local optimal results but also analyzing which discipline that the variables according to could be benefit for the convergence and robustness.Response surface method and Monte Carlo simulations were used to analyze whether the objective function and constraint function are sensitive to the variation of variables or not.Then the robust results could be found among a group of different local optimal solutions.展开更多
Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different...Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different octocopter configurations amid hover and forward flight. Conventional and coaxial configurations are studied and a hybrid configuration is also proposed to rectify the disadvantages associated with the earlier two. Comparison is carried out for the aforementioned configurations along with comparison of coaxial and hybrid octocopters with bigger diameter rotors in the same confined space for high thrust requirement missions. Vertical spacing of coaxial configuration is also studied. Virtual Blade Method (VBM) is considered herein due to its great computational efficiency. The results show that there are 11.89% and 14.22% loss in thrust for coaxial octocopter compared to conventional and hybrid configurations with normal size rotors and 15.61% loss compared to hybrid configuration with bigger rotors in hover, whereas coaxial square configuration performs the worst in forward flight with a lift loss of 9.1%, 14.77% and 18.8% compared to coaxial diamond, conventional and hybrid configurations with normal size rotors and 9.96% and 17.82% loss compared to coaxial diamond and hybrid configurations with bigger rotors. Combined FM shows that hybrid configuration outperforms other octocopter configurations in overall aerodynamic performance.展开更多
基金Item Sponsored by National Key Basic Research Program of China (2012CB722801)
文摘Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications and blade clearances, and the impact on blade section and shearing force of blade clearance was analyzed. Comparing with traditional experience formulas and measured values, the limitations of the experience formulas were proved. And by contrasting with the shearing force data collected from Linfen Iron and Steel Company, the reliability of the finite element method was further proved. The simulated results show that the simulated values controlled by ductile fracture criterion and measured values are very close, and the deviation value is in the range of 4.8%-20.8%. For the same steel, if the plate is thicker, the blade clearance will be greater, and thickness and blade clearance are approximately linear. The difference between numerical simulation of the maximum shearing force and the measured results is 7.7% to 12.0%, and the simulation results are close to facts. With the increase of blade clearance and the thickness, the shearing force was increased to some degree.
基金supported jointly by the National Basic Research Program of China(″973″Program)(No.2014CB046200)the Natural Science Foundation of Jiangsu Province(No.BK2014059)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China(No.11172135)
文摘Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 international specification and GL(Germanisher Lloyd)regulations for the wind energy conversion system.Stress analysis is performed with a 3-D finite element method(FEM).Considering Saint-Venant′s principle,a uniform cross section FEM model is built at each critical zone.Stress transformation matrixes(STM)are set up by applied six unit load components on the FEM model separately.STM can be used to convert the external load into stresses in the linear elastic range.The main material of composite wind turbine blade is fiber reinforced plastics(FRP).In order to evaluate the degree of fatigue damage of FRP,the stresses of fiber direction are extracted and the well-known strength criterion-Puck theory is used.The total fatigue damage of each laminate on the critical point is counted by the rain-flow counting method and Miner′s damage law based on general S-N curves.Several sections of a 45.3mblade of a 2 MW wind turbine are studied using the fatigue evaluation method.The performance of this method is compared with far more costly business software FOCUS.The results show that the fatigue damage of multi-axis FRP can be assessed conveniently by the FEM-STM method.And the proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.
基金financially supported by the Program for New Century Excellent Talents in University(No.NCET-13-0229,NCET-09-0396)the National Science & Technology Key Projects of Numerical Control(No.2012ZX04010-031,2012ZX0412-011)the National High Technology Research and Development Program("863"Program)of China(No.2013031003)
文摘For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.
基金This work was supported by the "985"foundation of China(No.082200102).
文摘A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural frequencies and mode shapes of the blade for the helicopter are studied by using beam characteristic orthogonal polynomials by the Rayleigh-Ritz method. The variation of natural frequencies with the speed of rotation and the mode shapes at different rotational speeds are plotted. The using of orthogonal polynomials for the bending shapes enables the computation of higher natural frequencies of any order to be accomplished without facing any difficulties.
基金National Nature Science Foundation of China (NO.50275121)
文摘An efficient multi-harmonic method is proposed for studying the effects of mistuning on resonant features of bladed disks with blade-to-blade dry friction damping. This method is able to predict accurately the forced response of bladed disks in frequency domain, which is validated by numerical integration method in time domain. The resonant features of both tuned and mistuned systems are investigated by using this method under various system coupling strengths, viscous dampings, and dry friction darnpings, etc. The results demonstrate that the proposed multi-harmonic method is very efficient for studying the mistuning effects on the resonant response of bladed disks with blade-to-blade dry friction damping, especially considering the combined effects of various system parameters.
基金Project(51335003)supported by the National Natural Science Foundation of ChinaProject(20111102110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.
文摘The doctor-blade method is investigated for the preparation of Cu2ZnSnS4 films for low-cost solar cell application. Cu2ZnSnS4 precursor powder, the main raw material for the doctor-blade paste, is synthesized by a simple ball-milling process. The doctor-bladed Cu2ZnSnS4 films are annealed in N2 ambient under various conditions and characterized by X-ray diffraction, ultraviolent/vis spectrophotometry, scanning electron microscopy, and current-voltage （J-V） meansurement. Our experimental results indicate that （i） the X-ray diffraction peaks of the Cu2ZnSnS4 precursor powder each show a red shift of about 0.4°; （ii） the high-temperature annealing process can effectively improve the crystallinity of the doctor-bladed Cu2ZnSnS4, whereas an overlong annealing introduces defects; （iii） the band gap value of the doctor-bladed Cu2ZnSnS4 is around 1.41 eV; （iv） the short-circuit current density, the open-circuit voltage, the fill factor, and the efficiency of the best Cu2ZnSnS4 solar cell obtained with the superstrate structure of fluorine-doped tin oxide glass/TiO2/In2S3/Cu2ZnSnS4/Mo are 7.82 mA/cm2, 240 mV, 0.29, and 0.55%, respectively.
基金supported by National Natural Science Foundation of China(Grant Nos.51175017,51245027)Innovation Foundation of Beihang University for PhD Graduates,China(Grant No.YWF-12-RBYJ008)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111102110011)
文摘Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.
基金supported by China Postdoctoral Science Foundationa key project of the National Natural Science Foundation of China (No. 51236006)
文摘Based on the investigation of mid-span local boundary layer suction and positive bowed cascade, a coupled local tailored boundary layer suction and positive bowed blade method is developed to improve the performance of a highly loaded diffusion cascade with less suction slot. The effectiveness of the coupled method under different inlet boundary layers is also investigated.Results show that mid-span local boundary layer suction can effectively remove trailing edge separation, but deteriorate the flow fields near the endwall. The positive bowed cascade is beneficial for reducing open corner separation, but is detrimental to mid-span flow fields. The coupled method can further improve the performance and flow field of the cascade. The mid-span trailing edge separation and open corner separation are eliminated. Compared with linear cascade with suction, the coupled method reduces overall loss of the cascade by 31.4% at most. The mid-span loss of the cascade decreases as the suction coefficient increases, but increases as bow angle increases. The endwall loss increases as the suction coefficient increases. By contrast, the endwall loss decreases significantly as the bow angle increases. The endwall loss of coupled controlled cascade is higher than that of bowed cascade with the same bow angle because of the spanwise inverse ‘‘C＂ shaped static pressure distribution. Under different inlet boundary layer conditions, the coupled method can also improve the cascade effectively.
基金supported by the National Major Science and Technology Project of China(Nos.2017-II-0006-0020 and J2019-II-0003-0023)。
文摘Nowadays,the adjoint method has become a popular approach in the optimization of turbomachinery to further improve its aerodynamic performance.However,design variables in these adjoint optimization applications are generally not direct design parameters of blade(such as wedge angles or maximum thickness),making the geometric variation by adjoint optimization can hardly be re-extracted as the change of each design parameter.By giving considerations to the G1 continuity constraint of adjoint method on its parameterization method,this manuscript shows how to apply a parameterization method in 3D blade design process into adjoint optimization.Nearly all design parameters can therefore be treated as design variables in the adjoint method and then participate in the sensitivity-based optimization.Finally,a fitted Rotor 67 blade is optimized and the adiabatic efficiency is significantly improved by nearly 0.91%.
基金supported by National Natural Science Foundation of China (Grant No. 60879002)Tianjin Municipal Science and Technology Support Plan of China (Grant No. 10ZCKFGX03800)
文摘Fatigue life and reliability of aero-engine blade are always of important significance to flight safety.The establishment of damage model is one of the key factors in blade fatigue research.Conventional linear Miner＇s sum method is not suitable for aero-engine because of its low accuracy.A back propagation neutral network（BPNN） based on the combination of Levenberg-Marquardt（LM） and finite element method（FEM） is used to describe process of nonlinear damage accumulation behavior in material and predict fatigue life of the blade.Fatigue tests of standard specimen made from TC4 are carried out to obtain material fatigue parameters and S-N curve.A nonlinear continuum damage model（CDM）,based on the BPNN with one hidden layer and ten neurons,is built to investigate the nonlinear damage accumulation behavior,in which the results from the tests are used as training set.Comparing with linear models and previous nonlinear models,BPNN has the lowest calculation error in full load range.It has significant accuracy when the load is below 500 MPa.Especially,when the load is 350 MPa,the calculation error of the BPNN is only 0.4%.The accurate model of the blade is built by using 3D coordinate measurement technology.The loading cycle in fatigue analysis is defined from takeoff to cruise in 10 min,and the load history is obtained from finite element analysis（FEA）.Then the fatigue life of the compressor blade is predicted by using the BPNN model.The final fatigue life of the aero-engine blade is 6.55 104 cycles（10 916 h） based on the BPNN model,which is effective for the virtual design of aero-engine blade.
文摘The potential hazard resulting from uncontained turbine engine rotor blade failure has always been the long-term concern of each aero engine manufacturer, and to fully contain the failed blades under critical operating conditions is also one of the most important considerations to meet the rotor integrity requirements. Usually, there are many factors involving the engine containment capability which need to be reviewed during the engine design phases, such as case thickness, rotor support structure, blade weight and shape, etc. However, the premier method to demonstrate the engine containment capability is the fan blade-off test and margin of safety （MS） analysis. Based on a concrete engine model, this paper aims to explain the key points of aero engine containment requirements in FAR Part 33, and introduces the implementation of MS analysis and fan blade-off test in the engine airworthiness certification. Through the introduction, it would be greatly helpful to the industrial community to evaluate the engine containment capability and prepare the final test demonstration in engine certification procedure.
基金Sponsored by the National Natural Science Foundation of China(Grant No.11572098)
文摘This paper aims to investigate the measurement uncertainty of blade surface by coordinates measuring machines (CMMs) in different sampling modes.Two different sampling methods for the blade surface, which are the parallel mode and the rotation mode, are studied to examine their measurement uncertainty.The fundamental principles and operational processes of the two modes are presented and discussed.The measurements were performed on a twisted-face blade, and data processing was also conducted to fit the cross-section profile both of the base surface and back surface separately.Then the measurement uncertainties of two sampling methods were evaluated on different parts of the blade surface in terms of the surface profile’s curvature and twist rate.It is found that the measurement of blade surface by CMMs shows much uncertainty for both of the sampling modes because of the complexity of the blade surface.The back surface’s measurement uncertainty is larger than that of the base surface.The measurement uncertainty of cross-section profiles on the top blade surface is larger than that of the bottom blade surface.In addition, the difference between the measurement uncertainties of two sampling methods is small, especially for the base blade surface.The research means that both sampling methods can be a practical application choice for the measurement of blade surface by CMMs.
文摘In this paper,stress states under corresponding condition of an aero-engine fan blade using finite element stress-strain analysis for three work cycles in the 900 h load spectrum are obtained.Through the nominal stress method,we calculated the fatigue notch factor and combined the material characteristics of TC6 to correct the material curve to the fan blades curve. Finally,the fatigue life of a fan blade was estimated using the linear cumulative damage rule and nonlinear cumulative damage theory.
基金The authors express their appreciation for the financial support of the Aeronautical Science Foundation of China （No. 02H53061） the National Natural Science Foundation of China for Distinguished Young Scholar （No. 50225518） the Innovation Foundation of Ph.D. Dissertation in NPU of China （No. CX200405）.
文摘Blade precision forging is a high temperature and large plastic deformation process. Process parameters have a great effect on temperature distribution in billet, so in this paper, by taking a Ti-6Al-4V alloy blade with a tenon as an object, the influence of process parameters on the temperature distribution in precision forging process was investigated using 3D coupled thermo-mechanical FEM （finite element method） code developed by the authors. The results obtained illustrate that： （1） the gradient of temperature distribution increases with increasing the deformation degree; （2） with increasing the initial temperature of the billet, the zones of high temperature become larger, and the gradient of temperature distribution hardly has any increase; （3） friction factors have little effect on the distribution of temperature field; （4） with increasing upper die velocity, temperature of the billet increases while the temperature gradient in billet decreases. The results are helpful to the design and optimization of the process parameters in precision forging process of Ti-alloy blade.
文摘Several structural design parameters for the description of the geometric features of a hollow fan blade were determined.A structural design optimization model of a hollow fan blade which based on the strength constraint and minimum mass was established based on the finite element method through these parameters.Then,the sequential quadratic programming algorithm was employed to search the optimal solutions.Several groups of value for initial design variables were chosen,for the purpose of not only finding much more local optimal results but also analyzing which discipline that the variables according to could be benefit for the convergence and robustness.Response surface method and Monte Carlo simulations were used to analyze whether the objective function and constraint function are sensitive to the variation of variables or not.Then the robust results could be found among a group of different local optimal solutions.
基金supported by the National Natural Science Foundation of China(No.11972190).
文摘Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different octocopter configurations amid hover and forward flight. Conventional and coaxial configurations are studied and a hybrid configuration is also proposed to rectify the disadvantages associated with the earlier two. Comparison is carried out for the aforementioned configurations along with comparison of coaxial and hybrid octocopters with bigger diameter rotors in the same confined space for high thrust requirement missions. Vertical spacing of coaxial configuration is also studied. Virtual Blade Method (VBM) is considered herein due to its great computational efficiency. The results show that there are 11.89% and 14.22% loss in thrust for coaxial octocopter compared to conventional and hybrid configurations with normal size rotors and 15.61% loss compared to hybrid configuration with bigger rotors in hover, whereas coaxial square configuration performs the worst in forward flight with a lift loss of 9.1%, 14.77% and 18.8% compared to coaxial diamond, conventional and hybrid configurations with normal size rotors and 9.96% and 17.82% loss compared to coaxial diamond and hybrid configurations with bigger rotors. Combined FM shows that hybrid configuration outperforms other octocopter configurations in overall aerodynamic performance.
