Abstract: The spatial location of center of mass and principal axis of inertia was utilized to describe the motion status of rotors.From the general definition of inertial load，the complete expressions of rotary inertial load were derived.Based on this，the continuous shaft model and its differential equations including the local rotary inertial load were established.Results showed that，the rotary inertia of high-speed-spinning disk can be categorized into self-centering of center of mass and self-centering of principle axis of inertia，which increases the forward processing natural frequencies and the bearing dynamic loads；the key to these influences is local angular stiffness between disk and shaft.On this basis，the reason was illustrated for the consistent increase of bearing dynamic load in high-speed range，while the influence of local angular stiffness between disk and shaft on the modal and response characteristics was investigated.The results above are of benefit to the vibrational fault detection and design of rotor structures during the engineering application.
Abstract: In view of the early-stage short crack propagation behaviour in turbine disks under low-cycle fatigue，a method coupling crystal plasticity （CP） theory and extended finite element method （XFEM） was proposed to simulate short cracks in engineering structures.The method used the total cumulative shear strain in crystals as the criterion of crack propagation and made the crack propagate along the slip plane with the most active slip system.By using sub-model technology/regional refinement of grids and a combination of macro-micro constitutive models，the framework overcame the scale mismatch between the real engineering structure and the micro model，and then predicted the short crack propagation path and rate in the dangerous section of a technique turbine disk at an acceptable calculation cost.The results showed that the short crack propagation path and rate in structures was highly affected by crystal orientations，resulting in a large dispersion of fatigue life.At the same time，it verified the feasibility of the CP-XFEM-based framework in predicting the short crack propagation life of engineering structures.
Abstract: In view of the imperfect design method of the crowned involute spline and the uncertainty of the range of the modification amount，a method of designing the crowned involute spline was proposed by using the allowable stress of the spline tooth surface and the interference of the inner and outer splines to determine the range of the crowned amount of the crowned spline.Taking the spline of a central transmission rod of an aero engine as an example，design of the crowned spline was carried out；and the contact characteristics of the ordinary spline were compared with those of the crowned spline under the alignment and misalignment state respectively.The research results showed that under the aligned condition，ordinary spline contact stress was concentrated on the tooth loading end，while the contact stress of the crowned spline was located in the axial tooth middle and the contact stress increased；in the misalignment state，the number of contact tooth pairs of the ordinary spline significantly reduced and the contact stress significantly increased，while the load-sharing effect of the crowned spline was significantly improved and the contact stress significantly reduced.As the misalignment increased，the ordinary spline had the risk of tooth breakage due to interference，while the crowned spline could still engage but the number of disconnected tooth pairs increased，and the contact stress also increased sharply.The determined range of the crowned spline modification amount was reasonable，and it can quantitatively couple the tooth backlash，misalignment compensation ability，and the modification amount.The research results provide an important theoretical basis for designing aero crowned splines，controlling the misalignment and improving the load-bearing capacity and the wear life.
Abstract: The problem of the burst speed of vortex reducer was studied by numerical analysis combined with experiment.According to the stress state of vortex reducer，the simulative specimen was designed，and the failure experiments under the monotonic tensile load were carried out.The failure parameters reflecting the structural stress characteristics were obtained.Furthermore，based on the finite element method，the failure parameters of the simulative specimen were introduced into burst speed prediction of vortex reducer and the influences of different failure criterion on the burst speed prediction were compared.The analysis showed that the stress gradient of simulative specimen was in good agreement with structure，which can accurately describe the structural stress characteristics.Burst speeds calculated by the methods of local plasticity and based on tensile strength of materials were more conservative，which were 15% and 23% lower than those predicted by average stress method，respectively.The method developed has engineering reference value for the failure analysis of structures.
Abstract: In view of the problem of blade rubbing response，a proper orthogonal decomposition method was proposed to reduce the dynamic order of the system.The projection space was generated by the proper orthogonal decomposition of the snapshot matrix，the system dynamic equation was projected into the subspace for model reduction，and the rubbing response was solved in combination with the numerical integration method.Based on the reduced order model，the blade rub impact response under different speed and penetration parameters was analyzed and compared with the full order model.The results showed that the time-domain response deviation of the reduced order model was less than 5%，and the computational efficiency of the reduced order model was improved by 98.4%.The robustness of the reduced order model was verified by changing the blade speed and penetration.With the increase of rotational speed and penetration，it was found that the energy of the proper orthogonal modes transferred between the lower order and the higher order，and presented different transfer laws.There was a certain relationship between the modal energy transfer caused by the rotational speed and the natural frequency of the structure.The method and conclusion can provide a basis for blade rub impact analysis and fault diagnosis.
Abstract: For prompting the application of functionally graded materials （FGMs） in the fields of engines，missiles and rockets，the traveling wave modal frequencies of rotating FGMs laminated cylindrical shell were studied.The Voigt model and Sigmoid volume fraction were employed to describe the material properties of the FGMs laminated cylindrical shell.The energy expression of the rotating FGMs laminated cylindrical shell was derived with the Coriolis force，centrifugal inertial force，hoop initial tension and thermal internal force involved.The modal frequency equation of the FGMs laminated cylindrical shell with arbitrary boundary conditions was derived by using the Chebyshev orthogonal polynomial as the admissible displacement function.And the effects of material components，sandwich thickness，temperature gradient and spring stiffness coefficients on the modal frequency of the FGMs laminated cylindrical shell were discussed.Results indicate that the sandwich thickness is more sensitive to the traveling wave mode than the Sigmoid volume fraction index；the short thin-walled cylindrical shell is more sensitive to boundary conditions and instability than the long thin-walled structures at high rotation speeds；the axial spring stiffness has a greater effect on the traveling wave mode than other spring stiffness.
Abstract: By setting up a flange contact thermal resistance experimental bench，within the range of 0-0.75 mm of flange clearance and 20-40 of bolt tightening torque，the wall temperature of multiple axial positions of casing of different materials was measured to obtain the heat flux passing through the flange，and the contact thermal resistance and unit contact thermal conductivity of the flange were obtained.The influences of flange clearance and bolt tightening torque on the contact thermal resistance of flange were analyzed.The results showed that with the increase of flange clearance，the contact thermal resistance increased linearly，the maximum increase was 0.03 K/W，the unit contact thermal conductivity decreased rapidly at first，and then was inclined to smooth，with the maximum reduction of 10 744.2 ，about 94.5%；with the increase of tightening torque，the contact thermal resistance decreased，the maximum reduction was 22.1%.
Abstract: Based on the VOF （volume of fluid） interface capture method and the dynamic adaptive grid technique，a direct numerical simulation of the breakup process of a circular jet was carried out.The surface morphology of the circular jet and the response characteristics of liquid ligaments and droplets under different disturbance frequencies were revealed.The results showed that Rayleigh linearized dispersion theory can well explain the instability process of jet surface wave.When the nozzle disturbance frequency （66.6 kHz） was less than the theoretical critical value of 95.5 kHz，the jet gradually lost stability with the evolution of time and space.When it was greater than the critical value，the amplitude of surface wave gradually weakened and the liquid core became smooth.When the surface wave was unstable，the falling droplets impacted the nodal structure and impact dents left on its surface；with the increase of nodal amplitude，the liquid film broke through，and then a large number of detached liquid ligaments and droplets were formed.Appropriate frequency disturbance can reduce the velocity fluctuation of the jet head and slow down the atomization process of the jet.The breakup of the jet surface wave and the breakup process of the liquid core head determined the size of the SMD （Sauter mean diameter） of spray field，and there existed mutual coupling between them.
Abstract: A method for simultaneous inversion of thermal conductivity of quartz window at different temperatures was presented by using transient thermal response information under high temperature heating.Combining the experimental test process，a high-temperature non-gray body radiative and conductive heat transfer model with a quartz window-graphite plate-quartz window sandwich structure was established firstly.Through the actual temperature response and the material's spectral radiation characteristic parameters，the genetic algorithm was used for constructing the inversion and identification model of the thermal conductivity of quartz window.The thermal conductivity of quartz window was inversed by the result data of 1 100 K heating conditions，ranging from 1.35 to 2.58 W/（m·K） at room temperature to 1 100 K，and the relationship between thermal conductivity and temperature was fitted.The influence of radiation on the thermal conductivity of the material increased with the temperature，accounting for 16.12% at 1 100 K.Finally，the method and the accuracy of the thermal conductivity data were verified by the additional high-temperature tests.
Abstract: In order to obtain the atomization characteristics of RP-3 kerosene and its surrogate fuel，the atomization characteristics （including the atomization cone angle，atomized particle size，droplet velocity） of RP-3 kerosene and its surrogate fuel （14% n-decane/10% n-dodecane/30% iso-cetane/36% methylcyclohexane/10% toluene，mole fraction） were experimentally tested and compared in the laser test platform of fuel nozzle atomization at the conditions of relative injection pressures of 200，400，600，800 kPa.The results showed that with the increase of relative injection pressure，the atomization cone angle and droplet velocity of RP-3 kerosene and its surrogate fuel increased gradually，but the value of Sauter mean diameter （SMD） decreased.Meanwhile，with the increase of the axial distance from the nozzle outlet，the SMD value and droplet velocity of RP-3 kerosene and its surrogate fuel decreased gradually.Under different relative injection pressures，the atomization cone angle and droplet velocity of the surrogate fuel were slightly higher than those of RP-3 kerosene，and the SMD value was slightly lower.However，the small difference indicated that the atomization characteristics of the surrogate fuel had a high similarity with RP-3 kerosene.
Abstract: Focusing on the performance recovery and knock suppression of two-stroke gasoline engine after switching to aviation kerosene，a one-dimensional simulation model of kerosene engine was established by GT-power，and the knock of kerosene engine was predicted and optimized.The simulation results showed that delaying the ignition time，the mixture far below and far greater than the theoretical air-fuel ratio can yield a certain inhibitory effect on knock.The experimental results verified the correctness of the simulation results.The control strategy of collaborative delaying ignition and increasing fuel injection was proposed and used for experimental researches.The results showed that the knock can be effectively suppressed at low speed and heavy load，the power recovery was generally more than 90% when the throttle was fully open.When the engine speed was 5 500 r/min，the power recovery can even reach 95.7% of the original engine.
Abstract: In order to achieve effective cooling of high temperature and large heat flux combustion devices in aerospace and other fields，the transpiration cooling performance of hydrogen for structure made by different materials and processes under high temperature and high flux density was studied.To simulate the structural characteristics and high heat flow of the high-pressure thrust chamber，a transpiration-cooling test piece was designed，and the mainstream air was heated by an electric arc to generate high-temperature gas.Hydrogen perspiration coolant was applied to 33 thermal tests for 172 seconds on porous ceramics，sintered porous stainless steel and porous laminate materials.The tested material had a porosity of 10%-40%，a combustion chamber pressure of 2.7-8.4 MPa，a mainstream gas temperature of about 3 600 K，a mainstream air flow rate of 220-1 490 g/s，a cooling hydrogen flow rate of 9.6-57 g/s，and an injection rate of 0.005-0.029.Test results showed that when the injection rate of hydrogen perspiration cooling was 1%，the heat exchange between the mainstream high-temperature gas and the walls of both the porous ceramics and the sintered porous stainless steel was reduced by more than 30% and 70%，respectively； when the injection rate of hydrogen perspiration cooling was 3%，the heat exchange between the mainstream high-temperature gas and the walls of the porous laminate materials was reduced by more than 60%.Hydrogen transpiration cooling can effectively reduce the convective heat flow between the wall and the gas.Furthermore，the performance correlation of high pressure，large heat flow and normal temperature hydrogen perspiration cooling was summarized.
Abstract: In order to analyze the spray characteristics and spray mechanism of gas-liquid pintle injector unit，the effects of throttling level on spray pattern，volume flow rate distribution，Sauter mean diameter （SMD） distribution and the velocity field were obtained by using backing-lighting photography technique and phase Doppler anemometry （PDA） system for the spray characteristics of gas-liquid pintle injector unit.The results showed that the spray of gas-liquid pintle injector was a fan-shaped form and the spray pattern was presented by shearing breaking.The volume flow rate presented a single peak distribution along the radial direction.With the decrease of throttling level，the edge of spray field shrank to the center.The SMD increased along the radial direction，and the best spay area was distributed in the center and both sides of the spay field.The value of SMD increased with the increasing throttling level.When the momentum ratio was constant，the throttling level had little influence on the variation range of SMD.The axial length of the backflow area below the pintle head decreased with the decreasing throttling level.
Abstract: From aspects of theory，experiments and numerical simulation，the research status and progress of cryogenic propellant jet atomization were analyzed and summarized.The mechanism and patterns of jet atomization were classified，the numerical research methods of jet atomization were sorted out and relevant experimental study of cryogenic jet atomization was introduced by comparing different atomization parameters between ambient fluids and cryogenic fluids.It indicates that the air disturbance induced breakup mechanism is the most accepted theory，whereas，the jet atomization morphology under supercritical conditions does not accord with the existing classification.Numerical methods for jet atomization gradually change from the volume of fluid method and level-set method to the direct numerical simulation.Modeling of flashing phenomenon is one of the key points in the simulation.Furthermore，there lacks of experimental data of the cryogenic jet atomization.Enriching measurement methods and improving measurement accuracy can solve this problem.
Abstract: In order to improve the aerodynamic performance of the rear stages of multi-stage axial compressor，an in-house optimization design platform for diffuser passage compressors based on genetic algorithm and neural network surrogate model was built and applied into the optimization design of an exit rotor with diffuser passage.Impacts of the design parameters on efficiency and stability improvement were analyzed based on optimization database.Two optimized diffuser passage designs were selected from the optimization solution set and their influencing rules and mechanisms on efficiency and stability were further studied.Results showed that application of diffuser passage design can improve the load coefficient by 12.1% and efficiency by 1.28% at design mass flow rate，the improvement of stall margin by 12.50% can also be obtained.According to the local entropy generation rate model，the loss of the upper and lower endwalls of the diffuser passage rotor was increased compared with the origin rotor，whereas the loss of profile was reduced. The main reason for stall margin increase of the diffuser passage rotor was the decrease of blockage coefficient near the stall point.
Abstract: Transonic centrifugal compressors face the problem of shock wave controlling.Therefore，the knowledge of the flow mechanism under leading edge swept effect plays an important role in improving the transonic centrifugal compressors performance.Two different transonic centrifugal compressors were investigated by numerical simulations after verified.The results show that,the inducer inlet shock position directly determines the effect of the leading edge swept under the design point.The change of leading edge swept can affect the flow-through capacity by changing the load distribution on the tip of inducer，and furthermore change the shock structure and flow loss on the tip of the inducer.For the impellers whose passage shock wave was swallowed in the blade passages，the backward swept weakened the strength of the passage shock wave and thus reduced the loss near the blade tip of the inducer.However，for the impellers whose leading edge shock wave was detached from leading edge，the forward swept weakened the strength of the leading edge shock wave and made the shock wave more attached，thus reducing the loss near the tip of inducers.
Abstract: In order to study the effects of throat-to-inlet area ratio，throat position and solidity on the performance of supersonic cascade at the minimum loss point，a series of planar cascades with designed Mach number 1.4 and different passage parameters were obtained based on a blading method of directly controlling the cascade passage.The results of numerical calculations and flow field analysis showed that the cascades can be divided into started and transitional ones according to different shock wave structures in cascade passages.Throat parameters mainly affected cascade performance by changing the location of the shock wave system.For a started cascade，the minimum total pressure loss decreased and the static pressure ratio increased when the throat-to-inlet area ratio was smaller and the throat position moved further forward，just the opposite for a transitional cascade.The structure of the shock wave system changed with the solidity.A tight solidity made more cascades started，having lower minimum total pressure loss and higher static pressure ratio，while wider solidity made more cascades non-started，having lager margin.
Abstract: In view of misjudgment of unknown new faults of rolling bearing affects bearing safety and maintenance efficienc，a fault diagnosis model based on improved gray wolf optimization （GWO） and light gradient boosting machine （LightGBM） was proposed to realize high precision discrimination about the known and unknown faults.The time domain，frequency domain and wavelet domain features were extracted separately from the vibration signal of the rolling bearing to avoid the lack of feature extraction at a single scale.The GWO-LightGBM model with unknown new fault diagnosis mechanism was designed，and the improved gray wolf algorithm with Halton sequence and simulated annealing strategy was constructed to realize the effective optimization of model parameters.The experimental results showed that the average recognition rate of the model for known and unknown faults was 99.57%.The average recognition rates for 10 times random experiments were 21.98%，17.00% and 9.27% higher than logistic regression （LR），K-nearest neighbor （KNN） and support vector machine （SVM），respectively.The comparative experiments verified the effectiveness and superiority of the model，which can identify known or unknown new faults with high accuracy.
Abstract: By considering the truth of the existence of machining errors of face gear，an iterative method was applied to make measurement coordinate system as close as possible to design coordinate system.The optimization model of the relationship between measurement coordinate system and design coordinat system was constrained according to the machining errors.This optimization model was accurately solved based on the above two steps.Furthermore，a mathematical model between the theoretical measurement point and the practical measurement point was established to compensate the related measurement errors caused by machining errors.Finally，the actual measurement experiment was carried out.The results showed that the error between the measurement coordinate system and the design coordinate system of this method was reduced by more than 89% compared with the traditional method，the maximum measurement deviation was reduced by more than 54%，presenting more real and reliable measurement results.
Abstract: For the purpose of expanding the application range of face gear，a new design of offset orthogonal arc tooth face gear was proposed by combining the characteristics of both face gear and arc tooth.The equations of full tooth surfaces were derived，and the visualization of tooth surfaces was realized in Matlab.Based on the mathematical model and the undercutting theory，the undercutting location of the gear was calculated.Result was confirmed by the simulation experiment using CATIA secondary development.Several factors influencing with the minimum inner radius were studied.The research showed that：while the positional parameter had a small negative influence on the minimum inner radius，the radius of the gear cutter and the offset distance both had positive influence on it.When the module of gear increased，the inner radius increased greatly.In the end，the location of the tooth tipping point was confirmed and the tooth width of face gear was calculated.
Abstract: A fluidic oscillator with high-frequency and high-speed was designed，and its frequency and velocity response to inlet pressure，and internal pressure propagation pattern were measured by hot wire anemometers and high-frequency dynamic pressure sensors.The results showed that the working frequency of the fluid oscillator was about 900 Hz，and when the inlet pressure ratio was 2，the outlet velocity range was 75-239 m/s.The relationship between the oscillation frequency and the internal size was established，the pressure propagation and reflection mechanism inside the oscillator were verified.And the two stages of the jet switching were explained by the pressure propagation mechanisms，which can provide insights into the future fluidic oscillator design under different flow control conditions.
Abstract: The initial disturbance combinations were selected based on the linear stability theory （LST） for a supersonic flat-plate boundary layer with Mach number of 4.5.Through direct numerical simulation （DNS），the generation process of streamwise vortex due to the evolution of combined first-mode unstable waves along the flow direction was simulated.Based on the vortex identification method of modified Omega-Liutex and the streamline diagram at different positions in the streamwise direction，the generation characteristics of streamwise vortex were analyzed，and its generation conditions were proposed according to the features of streamline in zy plane.It was found that streamwise vortex can be obtained directly by superimposing a pair of first-mode unstable oblique waves and basic flow，in which nonlinear action was not necessary.
Founded in 1986,
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Sponsor: Aviation Industry Corporation of China
Sponsored by: Chinese Society of Aeronautics Beijing University of Aeronautics and Astronautics
