In order to achieve a lower consumed energy, the performance of a new type of rotating volumetric pump with two profiled rotors (variant I) which is compared with a centrifugal pump (variant II) is presented. The...In order to achieve a lower consumed energy, the performance of a new type of rotating volumetric pump with two profiled rotors (variant I) which is compared with a centrifugal pump (variant II) is presented. The analysis regarding the same flow rate of transported liquid and the same pressure increases points out the conduct of the system at the variation of the key operating parameters. The actual driving power of the rotating volumetric pump is higher stating that is more advantageous in operation. The effective efficiency of the system is improved due to the original constructive solution.展开更多
The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic inter...The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic interaction between the blade rows. The results show that, compared to the compressor with unurved rotors, the compressor under scrutiny acquires remarkable increases in efficiency with significantly reduced amplitudes of the time-dependent fluctuation. The amplitude of the pressure fluctuation around the stator leading edge decreases at both endwalls, but increases at the mid-span in the curved rotors. The pressure fluctuation near the stator leading edge, therefore, becomes more uniform in the radial direction of this compressor. Except for the leading edge area, the pressure fluctuatinn amplitude declines remarkably in the tip region of stator surface downstream of the curved rotor, but hardly changes in the middle and at the hub.展开更多
The SiCp/Al-alloy composite front brake rotors designed for Shanghai Santana cars were prepared by semi-solid stirring+liquid forging process. The composite brake rotors were subjected to dynamometer tests on a SCHENC...The SiCp/Al-alloy composite front brake rotors designed for Shanghai Santana cars were prepared by semi-solid stirring+liquid forging process. The composite brake rotors were subjected to dynamometer tests on a SCHENCK brake testing system, referring to TL110 standard of VOLKSWAGEN Co. The friction coefficient and thermal response during fade testing and the wear performance of the composite rotors were studied as the functions of various parameters such as braking pressures, initial speeds, initial temperatures, torque and decelerations, and were compared with those of conventional cast iron rotors. The results show that the properties of the composite rotors can achieve the requirements of commercial cast iron rotors. The results also show that the friction coefficients of the composite rotors under different braking conditions are within the deviation band specified by the TL110 standard, and the temperature rise of composite rotors is lower than that of cast iron rotors at the end of each fade stop. The wear resistance of composite rotors is higher than that of cast iron rotors. The friction mechanism and wear mechanism were analyzed.展开更多
To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example an...To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example and Fluent software was applied to the virtual prototype simulations. Through simulation sample points, the total lift of the ducted coaxial-rotors aircraft was obtained. The Kriging model was then constructed, and the function was fitted. Improved particle swarm optimization(PSO) was also utilized for the global optimization of the Kriging model of the ducted coaxial-rotors aircraft for the determination of optimized global coordinates. Finally, the optimized results were simulated by Fluent. The results show that the Kriging model and the improved PSO algorithm significantly improve the lift performance of ducted coaxial-rotors aircraft and computer operational efficiency.展开更多
This work deals with a finite element procedure developed to perform the eigenvalue analysis of damped gyroscopic systems, represented by flexible rotors supported on fluid film journal bearings. The rotor finite elem...This work deals with a finite element procedure developed to perform the eigenvalue analysis of damped gyroscopic systems, represented by flexible rotors supported on fluid film journal bearings. The rotor finite element model is based on the Timoshenko beam theory, accounting for the shaft rotary inertia and gyroscopic moments. The governing equations for the hydrodynamic journal bearing are obtained through the Galerkin weighted residual method applied to the classical Reynolds equation. A perturbation scheme on the fluid film governing equation permits to obtain the zero-th and first order lubrication equations for the bearings, which allow the computation of the dynamic force coefficients associated with the bearing stiffness and damping. The rotor-bearing system equation, which consists of a case of damped gyroscopic equation, is rewritten on state form to compute the complex eigenvalues. The natural frequencies at several operating conditions are obtained and compared to the technical literature data. The influence of the effective damping on the eigenvalue real part sign is analyzed for some examples of rotor-bearing systems, showing how the stability conditions can be predicted by the eigenvalue analysis. The procedure implemented in this work can provide useful guidelines and technical data about the selection of the more appropriate set of bearing parameters for rotating machines operating at stringent conditions.展开更多
In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the ...In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the unbalances can be identified conveniently. Therefore, the rotor can be balanced without test runs.展开更多
The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor an...The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive, as for the upwind type, the inner and the outer rotational armatures, respectively, in keeping the rotational torque counter-balanced between both wind rotors/armatures. The unique rotational behaviors of the tandem wind rotors and the fundamental performances of the unit have been discussed at the previous paper. Continuously, this paper investigates experimentally and numerically the flow condition around the wind rotors to know the flow interactions between the front and the rear wind rotors, and optimizes the blade profile in the front wind rotor. The front blade should work fruitfully at the larger radius and had better not work at the smaller radius for giving plenty of wind energy to the rear wind rotor, taking account of the flow interaction between both wind rotors.展开更多
An iterative free-wake computational method is developed for the prediction of aerodynamic interaction characteristics between the twin rotors of a tandem helicopter.Here the mutual interaction effects between twin ro...An iterative free-wake computational method is developed for the prediction of aerodynamic interaction characteristics between the twin rotors of a tandem helicopter.Here the mutual interaction effects between twin rotors are included,as well as those between the rotor and wake.A rotor wake model,blade aerodynamic model and rotor trim model are coupled during the process of solution.A new dual-rotor trim approach is presented to fit for the aerodynamic interaction calculations between tandem twin rotors.By the present method,the blade aerodynamic loads and rotor performance for the twin rotors under the interactional condition are calculated,and the comparisons with available experimental data are also made to indicate the capability of the proposed method.Then,the effects of such parameters as the longitudinal separation and axial separation between twin rotors on the aerodynamic interaction characteristics are analyzed.Based on the investigation,the conclusions are obtained to be of benefit to the configuration design of tandem rotors.Furthermore,the performance comparison between the tandem rotors and a single rotor is conducted.It is shown that the strongest interaction does not appear in a hover state,but in a low-speed forward flight state.展开更多
During recent years,the axial-flus PMSM with contra-rotating rotors has become a hot topic in academic research due to its high efficiency and simple structure.However,its back-EMF may be distorted under the condition...During recent years,the axial-flus PMSM with contra-rotating rotors has become a hot topic in academic research due to its high efficiency and simple structure.However,its back-EMF may be distorted under the condition of different angular positions.This paper investigates characteristics of the novel motor used for contra-propeller driving.Considering the torque ripple and current oscillation under unbalanced load condition,this paper analyzes the distorted back-EMF of the machine when its two rotors get different angular positions during rotating.The analysis results are validated by transient-magnetic 3-D FEA method,which the 3-D FEA software is used to model this motor and transient simulations are carried out to obtain its magnetic characteristic and main performances.A main focus is put on the back-EMF characteristic with different angular positions between the two rotors.Furthermore,the characteristic of torque production under unbalanced load is investigated.Finally,a prototype motor is fabricated to validate the analyses of this paper.展开更多
A Large balancing weight may be obtained by calculation, when the ordinary influence coefficient method is used. In this paper, a new residual value balance method is recommended. The fundamental idea of the new metho...A Large balancing weight may be obtained by calculation, when the ordinary influence coefficient method is used. In this paper, a new residual value balance method is recommended. The fundamental idea of the new method is on the principle of getting the minimized weight on condition that the vibration values at various points are less than the admitted ones. Experimental results show that this method is effective for balancing the insensitive rotor and rotors with special dynamic characteristics.展开更多
The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is a...The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.展开更多
A sudden increase of vibration amplitude with no foreboding often results in an abrupt breakdown of a mechanical system.The catastrophe of vibration state of a faulty rotor is a typical nonlinear phenomenon,and very d...A sudden increase of vibration amplitude with no foreboding often results in an abrupt breakdown of a mechanical system.The catastrophe of vibration state of a faulty rotor is a typical nonlinear phenomenon,and very difficult to be described and predicted with linear vibration theory.On the basis of nonlinear vibration and catastrophe theory,fhe eatastrophe of the vibration amplitude of the faulty rotor is described;a way to predict its emergence is developed.展开更多
Twin-rotor cylinder-embedded piston engine is proposed for dealing with the sealing problems of rotors in twin-rotor piston engine where the existent mature sealing technologies for traditional reciprocating engine ca...Twin-rotor cylinder-embedded piston engine is proposed for dealing with the sealing problems of rotors in twin-rotor piston engine where the existent mature sealing technologies for traditional reciprocating engine can be applied.The quantity and forms of its sealing surfaces are reduced and simplified,and what's more,the advantages of twin-rotor piston engine are inherited,such as high power density and no valve mechanism.Given the motion law of two rotors,its kinematic model is established,and the general expression for some parameters related to engine performance,such as the trajectory,displacement,velocity and acceleration of the piston and centroid trajectory,angular displacement,velocity and acceleration of the rod are presented.By selecting different variation patterns of relative angle of two rotors,the relevant variables are compared.It can be concluded that by designing the relative angle function of two rotors,the volume variation of working chamber can be changed.However,a comprehensive consideration for friction and vibration is necessary because velocity and acceleration are quite different in the different functions,the swing magnitude of rod is proportional to link ratio λ,and the position of rod swing center is controlled by eccentricity e.In order to reduce the lateral force,a smaller value of λ should be selected in the case of the structure,and the value of e should be near 0.95.There is no relationship between the piston stroke and the variation process of relative angle of two rotors,the former is only proportional to the amplitude of relative angle of two rotors.展开更多
A rotor dynamic model is built up for investigating the effects of tightening torque on dynamic characteristics of low pressure rotors connected by a spline coupling.The experimental rotor system is established using ...A rotor dynamic model is built up for investigating the effects of tightening torque on dynamic characteristics of low pressure rotors connected by a spline coupling.The experimental rotor system is established using a fluted disk and a speed sensor which is applied in an actual aero engine for speed measurement.Through simulating calculation and experiments,the effects of tightening torque on the dynamic characteristics of the rotor system connected by a spline coupling including critical speeds,vibration modes and unbalance responses are analyzed.The results show that when increasing the tightening torque,the first two critical speeds and the amplitudes of unbalance response gradually increase in varying degrees while the vibration modes are essentially unchanged.In addition,changing axial and circumferential positions of the mass unbalance can lead to various amplitudes of unbalance response and even the rates of change.展开更多
We investigate the quantum-classical transition in a system of two coupled kicked rotors. We lind that when the mass of one kicked rotor is much smaller than the other's, the influence of the light kicked rotor is st...We investigate the quantum-classical transition in a system of two coupled kicked rotors. We lind that when the mass of one kicked rotor is much smaller than the other's, the influence of the light kicked rotor is still able to make decoherence of the heavy one. This leads to the quantum-classical transition of the heavy kicked rotor. We demonstrate this by two different coupling potentials.展开更多
The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 4...The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of ?2.3。, wind speeds of 10, 15, 24 m/s and yaw angles of 15。, 30。 and 45。. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm, a pitch angle of 3。, a wind speed of 5 m/s and yaw angles of 10。and 30。. The computed loads are compared to the loads measured from pressure measurement.展开更多
Based on the structural and mechanics analysis of aero-engines rotor system, the dynamic model of the flexible rotor system with multi-supports are presented in order to solve the bearing misalignment problem of rotor...Based on the structural and mechanics analysis of aero-engines rotor system, the dynamic model of the flexible rotor system with multi-supports are presented in order to solve the bearing misalignment problem of rotor system in aero-engines. The motion equations are derived through Lagrange method. The relationship between structural and mechanics characteristics parameters are built up. Finally, the dynamic influence of bearing misalignment on rotor system are divided into three kinds: additional rotor bending rigidity, additional bearing misalignment excitation force and additional imbalance. The equations suggest that additional imbalance excitation force activates the nonlinearity on rotor system and an additional 2x excitation force might appear.展开更多
An interactive computer aided preliminary design system has been developed mainly for gas turbine engine rotors. The design system covers three parts: disks, shafts and rotor dynamics. A nu- merical optimization packa...An interactive computer aided preliminary design system has been developed mainly for gas turbine engine rotors. The design system covers three parts: disks, shafts and rotor dynamics. A nu- merical optimization package called MPOP is used to minimize the weight of disks, shafts and optimize the arrangement or stiffness of bearings for rigid or flexible rotors subjected to certain constraints of sizes, shapes, stresses, deflections, stiffness and frequencies. Various forms of disks, shafts, rotors and structure-analysing result curves are displayed on the screen. Designer may select, inspect or modi- fy the results interactively. The integrated design of structure, optimization, strength and rotor dynamics has improved design quality and reduced turnaround time during preliminary design phase of gas turbine engine develop- ment. As an example, a real preliminary design of an aeroengine turbine rotor is described.展开更多
Two turbine rotors with outer rim and without outer rim were designed to analyze the influence of outer rim of rotors on the performance of a turbodrill. Two 3D models of the turbine rotor with different structures we...Two turbine rotors with outer rim and without outer rim were designed to analyze the influence of outer rim of rotors on the performance of a turbodrill. Two 3D models of the turbine rotor with different structures were established by SolidWorks software. The numerical simulation analysis of the turbine with different rotor structures was carried out based on software of fluent and then the performance of them at different rotating speeds was obtained. The results show that the torque,pressure drop and hydraulic efficiency of the turbine rotor with outer rim are greater than that of the turbine rotor without outer rim. By comparing the turbine rotor with outer rim and without outer rim,its torque increases 20. 1%,pressure drop increases 8.7% and hydraulic efficiency increases 10.4% at the maximum efficiency point. The related research is of guiding significance to further optimization of turbine rotor structure.展开更多
We present an immersed array of four rotors whose promoted flow can be mathematically modeled with a creeping flow solution from the incompressible Navier-Stokes equations. We show that this solution is indeed represe...We present an immersed array of four rotors whose promoted flow can be mathematically modeled with a creeping flow solution from the incompressible Navier-Stokes equations. We show that this solution is indeed representative of the two-dimensional experiment and validate such class of solution with experimental data obtained through the Particle Image Velocimetry technique and time-lapsed particles visualizations.展开更多
文摘In order to achieve a lower consumed energy, the performance of a new type of rotating volumetric pump with two profiled rotors (variant I) which is compared with a centrifugal pump (variant II) is presented. The analysis regarding the same flow rate of transported liquid and the same pressure increases points out the conduct of the system at the variation of the key operating parameters. The actual driving power of the rotating volumetric pump is higher stating that is more advantageous in operation. The effective efficiency of the system is improved due to the original constructive solution.
基金National Natural Science Foundation of China (506460210) Chinese Specialized Research Fund for the Doctoral Program of Higher Education (20060213007)Development Program for Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2006.046)
文摘The unsteady 3D flow fields in a single-stage transonic compressor under designed conditions are simulated numerically to investigate the effects of the curved rotors on the stage performance and the aerodynamic interaction between the blade rows. The results show that, compared to the compressor with unurved rotors, the compressor under scrutiny acquires remarkable increases in efficiency with significantly reduced amplitudes of the time-dependent fluctuation. The amplitude of the pressure fluctuation around the stator leading edge decreases at both endwalls, but increases at the mid-span in the curved rotors. The pressure fluctuation near the stator leading edge, therefore, becomes more uniform in the radial direction of this compressor. Except for the leading edge area, the pressure fluctuatinn amplitude declines remarkably in the tip region of stator surface downstream of the curved rotor, but hardly changes in the middle and at the hub.
文摘The SiCp/Al-alloy composite front brake rotors designed for Shanghai Santana cars were prepared by semi-solid stirring+liquid forging process. The composite brake rotors were subjected to dynamometer tests on a SCHENCK brake testing system, referring to TL110 standard of VOLKSWAGEN Co. The friction coefficient and thermal response during fade testing and the wear performance of the composite rotors were studied as the functions of various parameters such as braking pressures, initial speeds, initial temperatures, torque and decelerations, and were compared with those of conventional cast iron rotors. The results show that the properties of the composite rotors can achieve the requirements of commercial cast iron rotors. The results also show that the friction coefficients of the composite rotors under different braking conditions are within the deviation band specified by the TL110 standard, and the temperature rise of composite rotors is lower than that of cast iron rotors at the end of each fade stop. The wear resistance of composite rotors is higher than that of cast iron rotors. The friction mechanism and wear mechanism were analyzed.
基金Project(2013AA063903)supported by High-tech Research and Development Program of China
文摘To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example and Fluent software was applied to the virtual prototype simulations. Through simulation sample points, the total lift of the ducted coaxial-rotors aircraft was obtained. The Kriging model was then constructed, and the function was fitted. Improved particle swarm optimization(PSO) was also utilized for the global optimization of the Kriging model of the ducted coaxial-rotors aircraft for the determination of optimized global coordinates. Finally, the optimized results were simulated by Fluent. The results show that the Kriging model and the improved PSO algorithm significantly improve the lift performance of ducted coaxial-rotors aircraft and computer operational efficiency.
文摘This work deals with a finite element procedure developed to perform the eigenvalue analysis of damped gyroscopic systems, represented by flexible rotors supported on fluid film journal bearings. The rotor finite element model is based on the Timoshenko beam theory, accounting for the shaft rotary inertia and gyroscopic moments. The governing equations for the hydrodynamic journal bearing are obtained through the Galerkin weighted residual method applied to the classical Reynolds equation. A perturbation scheme on the fluid film governing equation permits to obtain the zero-th and first order lubrication equations for the bearings, which allow the computation of the dynamic force coefficients associated with the bearing stiffness and damping. The rotor-bearing system equation, which consists of a case of damped gyroscopic equation, is rewritten on state form to compute the complex eigenvalues. The natural frequencies at several operating conditions are obtained and compared to the technical literature data. The influence of the effective damping on the eigenvalue real part sign is analyzed for some examples of rotor-bearing systems, showing how the stability conditions can be predicted by the eigenvalue analysis. The procedure implemented in this work can provide useful guidelines and technical data about the selection of the more appropriate set of bearing parameters for rotating machines operating at stringent conditions.
文摘In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the unbalances can be identified conveniently. Therefore, the rotor can be balanced without test runs.
文摘The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive, as for the upwind type, the inner and the outer rotational armatures, respectively, in keeping the rotational torque counter-balanced between both wind rotors/armatures. The unique rotational behaviors of the tandem wind rotors and the fundamental performances of the unit have been discussed at the previous paper. Continuously, this paper investigates experimentally and numerically the flow condition around the wind rotors to know the flow interactions between the front and the rear wind rotors, and optimizes the blade profile in the front wind rotor. The front blade should work fruitfully at the larger radius and had better not work at the smaller radius for giving plenty of wind energy to the rear wind rotor, taking account of the flow interaction between both wind rotors.
文摘An iterative free-wake computational method is developed for the prediction of aerodynamic interaction characteristics between the twin rotors of a tandem helicopter.Here the mutual interaction effects between twin rotors are included,as well as those between the rotor and wake.A rotor wake model,blade aerodynamic model and rotor trim model are coupled during the process of solution.A new dual-rotor trim approach is presented to fit for the aerodynamic interaction calculations between tandem twin rotors.By the present method,the blade aerodynamic loads and rotor performance for the twin rotors under the interactional condition are calculated,and the comparisons with available experimental data are also made to indicate the capability of the proposed method.Then,the effects of such parameters as the longitudinal separation and axial separation between twin rotors on the aerodynamic interaction characteristics are analyzed.Based on the investigation,the conclusions are obtained to be of benefit to the configuration design of tandem rotors.Furthermore,the performance comparison between the tandem rotors and a single rotor is conducted.It is shown that the strongest interaction does not appear in a hover state,but in a low-speed forward flight state.
基金This work was supported in part by the National Key R&D Program of China(No.2017YFB1300900)the Natural Science Foundation of China under Grant 51577052,51707062.
文摘During recent years,the axial-flus PMSM with contra-rotating rotors has become a hot topic in academic research due to its high efficiency and simple structure.However,its back-EMF may be distorted under the condition of different angular positions.This paper investigates characteristics of the novel motor used for contra-propeller driving.Considering the torque ripple and current oscillation under unbalanced load condition,this paper analyzes the distorted back-EMF of the machine when its two rotors get different angular positions during rotating.The analysis results are validated by transient-magnetic 3-D FEA method,which the 3-D FEA software is used to model this motor and transient simulations are carried out to obtain its magnetic characteristic and main performances.A main focus is put on the back-EMF characteristic with different angular positions between the two rotors.Furthermore,the characteristic of torque production under unbalanced load is investigated.Finally,a prototype motor is fabricated to validate the analyses of this paper.
文摘A Large balancing weight may be obtained by calculation, when the ordinary influence coefficient method is used. In this paper, a new residual value balance method is recommended. The fundamental idea of the new method is on the principle of getting the minimized weight on condition that the vibration values at various points are less than the admitted ones. Experimental results show that this method is effective for balancing the insensitive rotor and rotors with special dynamic characteristics.
文摘The nonlinear properties of rotating machinery vibration signals are presented. The relationship between faults and quadratic phase coupling is discussed. The mechanism that gives rise to quadratic phase coupling is analyzed, and the coupling models are summarized. As a result, higher order spectra analysis is introduced into fault diagnosis of rotors. A brief review of the properties of higher order spectra is presented. Furthermore, the bicoherence spectrum is employed to extract the features that signify the machinery condition. Experiments show that bicoherence spectrum patterns of different faults are quite different, so it is proposed to identify the faults in rotors.
文摘A sudden increase of vibration amplitude with no foreboding often results in an abrupt breakdown of a mechanical system.The catastrophe of vibration state of a faulty rotor is a typical nonlinear phenomenon,and very difficult to be described and predicted with linear vibration theory.On the basis of nonlinear vibration and catastrophe theory,fhe eatastrophe of the vibration amplitude of the faulty rotor is described;a way to predict its emergence is developed.
文摘Twin-rotor cylinder-embedded piston engine is proposed for dealing with the sealing problems of rotors in twin-rotor piston engine where the existent mature sealing technologies for traditional reciprocating engine can be applied.The quantity and forms of its sealing surfaces are reduced and simplified,and what's more,the advantages of twin-rotor piston engine are inherited,such as high power density and no valve mechanism.Given the motion law of two rotors,its kinematic model is established,and the general expression for some parameters related to engine performance,such as the trajectory,displacement,velocity and acceleration of the piston and centroid trajectory,angular displacement,velocity and acceleration of the rod are presented.By selecting different variation patterns of relative angle of two rotors,the relevant variables are compared.It can be concluded that by designing the relative angle function of two rotors,the volume variation of working chamber can be changed.However,a comprehensive consideration for friction and vibration is necessary because velocity and acceleration are quite different in the different functions,the swing magnitude of rod is proportional to link ratio λ,and the position of rod swing center is controlled by eccentricity e.In order to reduce the lateral force,a smaller value of λ should be selected in the case of the structure,and the value of e should be near 0.95.There is no relationship between the piston stroke and the variation process of relative angle of two rotors,the former is only proportional to the amplitude of relative angle of two rotors.
文摘A rotor dynamic model is built up for investigating the effects of tightening torque on dynamic characteristics of low pressure rotors connected by a spline coupling.The experimental rotor system is established using a fluted disk and a speed sensor which is applied in an actual aero engine for speed measurement.Through simulating calculation and experiments,the effects of tightening torque on the dynamic characteristics of the rotor system connected by a spline coupling including critical speeds,vibration modes and unbalance responses are analyzed.The results show that when increasing the tightening torque,the first two critical speeds and the amplitudes of unbalance response gradually increase in varying degrees while the vibration modes are essentially unchanged.In addition,changing axial and circumferential positions of the mass unbalance can lead to various amplitudes of unbalance response and even the rates of change.
基金supported by National Natural Science Foundation of China under Grant No.10875087
文摘We investigate the quantum-classical transition in a system of two coupled kicked rotors. We lind that when the mass of one kicked rotor is much smaller than the other's, the influence of the light kicked rotor is still able to make decoherence of the heavy one. This leads to the quantum-classical transition of the heavy kicked rotor. We demonstrate this by two different coupling potentials.
文摘The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of ?2.3。, wind speeds of 10, 15, 24 m/s and yaw angles of 15。, 30。 and 45。. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm, a pitch angle of 3。, a wind speed of 5 m/s and yaw angles of 10。and 30。. The computed loads are compared to the loads measured from pressure measurement.
文摘Based on the structural and mechanics analysis of aero-engines rotor system, the dynamic model of the flexible rotor system with multi-supports are presented in order to solve the bearing misalignment problem of rotor system in aero-engines. The motion equations are derived through Lagrange method. The relationship between structural and mechanics characteristics parameters are built up. Finally, the dynamic influence of bearing misalignment on rotor system are divided into three kinds: additional rotor bending rigidity, additional bearing misalignment excitation force and additional imbalance. The equations suggest that additional imbalance excitation force activates the nonlinearity on rotor system and an additional 2x excitation force might appear.
文摘An interactive computer aided preliminary design system has been developed mainly for gas turbine engine rotors. The design system covers three parts: disks, shafts and rotor dynamics. A nu- merical optimization package called MPOP is used to minimize the weight of disks, shafts and optimize the arrangement or stiffness of bearings for rigid or flexible rotors subjected to certain constraints of sizes, shapes, stresses, deflections, stiffness and frequencies. Various forms of disks, shafts, rotors and structure-analysing result curves are displayed on the screen. Designer may select, inspect or modi- fy the results interactively. The integrated design of structure, optimization, strength and rotor dynamics has improved design quality and reduced turnaround time during preliminary design phase of gas turbine engine develop- ment. As an example, a real preliminary design of an aeroengine turbine rotor is described.
基金National Natural Science Foundation of the Country Project(51704034)Major National Special topics(2016ZX05038-002-LH001)Zhonghai Petroleum(China)Co.Ltd.Zhanjiang Branch Project(CCL2017ZJFN2272)
文摘Two turbine rotors with outer rim and without outer rim were designed to analyze the influence of outer rim of rotors on the performance of a turbodrill. Two 3D models of the turbine rotor with different structures were established by SolidWorks software. The numerical simulation analysis of the turbine with different rotor structures was carried out based on software of fluent and then the performance of them at different rotating speeds was obtained. The results show that the torque,pressure drop and hydraulic efficiency of the turbine rotor with outer rim are greater than that of the turbine rotor without outer rim. By comparing the turbine rotor with outer rim and without outer rim,its torque increases 20. 1%,pressure drop increases 8.7% and hydraulic efficiency increases 10.4% at the maximum efficiency point. The related research is of guiding significance to further optimization of turbine rotor structure.
文摘We present an immersed array of four rotors whose promoted flow can be mathematically modeled with a creeping flow solution from the incompressible Navier-Stokes equations. We show that this solution is indeed representative of the two-dimensional experiment and validate such class of solution with experimental data obtained through the Particle Image Velocimetry technique and time-lapsed particles visualizations.