Abstract: There are some problems such as single-point measurement，inaccurate measurement and mismatching positions for current ice detection system of airplane.The optic fiber ice detection sensor was developed by the light intensity reflection method.And the flat film ice detection sensor was manufactured by the piezoelectric vibration method.These two were embedded into a NACA0012 airfoil.Thus a hybrid ice detection system suitable for airfoil surface and multi-point distributed measurement was developed，which was tested in cold storage and icing wind tunnel.It showed that，the hybrid ice detection system of multi-point distribution measurement can not only have the advantages of optic fiber ice detection and flat film ice detection，but also achieve ice detection on airfoil surface.The response time was less than 0.5 s and the measurement range of ice thickness was from 0.2 mm to 3 mm.The reliability of hybrid ice detection system was better than that of ice detection rod of single-point measurement，proving it is a novel and prospective ice detection technology.
Abstract: The theory and method of ground based scrubbing inerting technology of unmanned aerial vehicle fuel tank were proposed.CFD method was used to study the feasibility of using ground based scrubbing inerting technology to reduce the oxygen volume fraction in fuel tank and keeping the fuel tank inert under the ground and flight conditions.Volume of fluid（VOF） two-phase flow model and custom mass transfer equation were applied to calculate the variation of oxygen volume fraction in fuel tank under different initial oxygen volume fraction and fuel load.The results indicated that the oxygen volume fraction in fuel tank ullage increased with the increase of initial fuel load and initial oxygen volume fraction at the same flight time.When the initial oxygen volume fraction was no more than 2% and the initial fuel load was no more than 50%，the oxygen volume fraction in fuel tank was kept less than 9%，up to the requirements of military aircraft fuel tank inerting.This study can provide a reference for the design of boundary condition of ground based scrubbing inerting of unmanned aerial vehicle fuel tank.
Abstract: The influences of different swirler types on the spray characteristics of dual-stage swirl airblast atomizer were investigated by using a combination method with experiment and numerical calculation.Particle image velocimetry （PIV） was applied to measure the downstream flow field structures of different swirler types，a high-speed camera and a laser particle size analyzer were used to photograph the atomization morphology，measure Sauter mean diameter （SMD） and Rosin-Rammler distribution under different air flow and fuel flow rates.At the same time，the secondary atomization characteristics of the dual-axial swirl cup were obtained by using the numerical calculation method.The results showed that，under the same working conditions，the atomization cone angle of the atomizer with two-stage axial swirler was slightly larger than that of the radial swirler.The atomization process with dual-stage radial swirler mainly relied on its centrifugal atomization of the atomizer，and the air assisted atomization was limited.The atomization process with dual-stage axial swirler was mainly affected by the first atomization of the atomizer when the pressure loss of swirl cup was small.With the increase of pressure loss，the air assisted atomization effect gradually played a major role.The numerical calculation results were in good agreement with the experimental results，indicating that the numerical calculation method can be used to simulate the atomization process of the dual-stage swirl airblast atomizer，and the numerical results can be used to explain the secondary atomization process.
Abstract: In order to understand the thermal and mechanical equilibrium characteristics of ice crystal in large icing wind tunnel，a numerical approach based upon the Eulerian method coupling movement and heat and mass transfer of ice crystal was developed to simulate the process of movement and heat transfer of ice crystal in the typical configuration of China Aerodynamics Research and Development Center icing wind tunnel.The effects of particle shape and bulk density were examined from three aspects of sink and contraction，momentum equilibrium and thermal equilibrium.Results showed that the particle shape and bulk density had no significant effects on the thermal and mechanical equilibrium characteristics of small size ice crystals.Decreased particle sphericity and bulk density could restrain the sink and contraction of large size ice crystals，thereby increasing the ice crystal cloud size at the exit of configuration.The decrease in particle sphericity and bulk density could increase the particle modified drag coefficient and modified Nusselt number，and then enhance particle momentum and thermal followability，thereby facilitating large size ice particles approaching the momentum equilibrium and thermal equilibrium states at the exit.Under typical computational conditions with large size ice crystal，the velocity and temperature differences of spherical particle at the exit of configuration were about 21 m/s and 8.6 ℃，while those of plate-shaped particle with low bulk density reduced to about 1 m/s and 5.8 ℃，respectively.
Abstract: The interaction between the mainstream and coolant flow from the crater hole on flat plate was studied by large eddy simulation method，and the film-cooling enhancement mechanism of crater hole was revealed.The simulation results were compared with the experimental results by infrared thermal imaging test and particle image velocimetry.The results showed that the crater hole generated a pair of anti-kidney vortices downstream the coolant exit，promoted the entrainment of coolant towards the wall and improved the coolant coverage.Compared with round hole，large-scaled coherent structures including hairpin vortices and horseshoe vortices can also be observed in crater-hole flow fields.However，different from round-hole，the concave effect on the trailing edge of crater generated parallel lines of hairpin vortices，presenting better stability at high blowing ratio.The time-frequency analysis of pressure fluctuation signals showed that the periodicity of crater-hole film cooling was weaker，and the small-frequency vortices played a dominant role.Overall，crater improved the lateral spreading of coolant jet，and its cooling performance was better than round-hole.
Abstract: In order to obtain the combustion characteristics of gas-liquid two-phase multi-cycle U-bend pulse detonation combustor （U-PDC） under high temperature inlet stream，experimental research was carried out by using gasoline and air as fuel and oxidant.The results indicated that the U-PDC can achieve stable operation at the working frequency of 15-38 Hz when the inlet temperature was 373 K，and the deflagration to detonation transition （DDT） distance was shortened when the working frequency increased.When the working frequency was 15-25 Hz，the detonation initiation failed at room temperature.The results showed that high temperature inflow can promote the DDT process.At room temperature and working frequency of 15-25 Hz，due to the uneven distribution of combustible gas in the U-bend detonation tube，the time when the flame was detected outside of the U-bend detonation tube was later than the exit of the U-bend detonation tube.When the inflow temperature increased to 373 K，the phenomenon was obviously improved.In addition，the ignition time of U-PDC was within 3-10 ms，which was greatly affected by ignition delay time.When the working frequency of U-PDC was the same and the inlet stream temperature raised from room temperature to 373 K，the wave velocity increased，and the ignition time decreased.
Abstract: Taking the simplified airborne integrated thermal management system as the research object，the change characteristics of the system under different control modes were analyzed，which provided a theoretical basis for the study of system control schemes.Using a combination of mathematical models and computer models to establish an airborne integrated thermal management system model with fuel as the main heat sink，air/fuel heat exchanger，fuel/PAO （polymerized alpha olefin） heat exchanger and other main components，and a fuzzy self-tuning PID （proportional-integral-derivative） control method was proposed to analyze system characteristics such as fuel/PAO heat exchanger and electronic equipment thermal changes.The results show that compared to open-loop control under thermal extreme conditions，the fuzzy self-tuning PID control mode can not only effectively control a series of equipment such as fuel pumps to maintain proper speed，but also ensure the electronic cabin and fuel/PAO heat exchanger.The outlet temperatures are kept within a predetermined range to meet the design requirements of the airborne integrated thermal management system.
Abstract: The flow response law of pulse jet through cooling pipe with structural parameters was explored. Under the aerodynamic parameters of pulse frequency of 1 Hz，Reynolds number of 5 000 and pulse jet duty ratio of 50%，the influences of cooling pipe diameter，jet hole diameter，hole spacing on the pulse jet flow response characteristics were analyzed successively and the internal mechanism of the influence of structural parameters on the flow response characteristics of pulse jet in the cooling pipe was comprehensively described.In view of the structural parameters，empirical formulae of the cooling pipe jet quality coefficients with cooling pipe diameter，jet hole diameter，hole spacing were fitted to optimize the array of pulse jet cooling pipe chamber，providing a reference for structure design.It was found that the response time and hysteresis time of cooling pipe jet velocity decreased with the increase of cooling pipe diameter，hole spacing and jet hole diameter.With the increase of cooling pipe diameter，the decrease of jet hole diameter and hole spacing，the pressure in the cooling pipe and the jet velocity coefficient increased，and the flow capacity decreased.
Abstract: Spray characteristics of liquid jet in nonuniform velocity distribution crossflow were experimentally studied.The nonuniform velocity distribution was produced by perforated plates，the images of spray were captured with a light sheet and a single lens reflex camera，and a phase Doppler particle analyzer （PDPA） was used to measure droplets diameter and velocity.The experimental results indicated that，in the nonuniform crossflow，the bending state and breakup regime of each jet section were different，resulting in the difference of penetration and spray characteristics.Compared with uniform corssflow，the jets penetrated further into the crossflow when the column breakup height increased，and the concentration distribution was more uniform when the velocity distribution was in positive gradient，in addition，the jet presented a flat thrown profile.When the velocity gradient was negative，the spray field moved inward and presented a stratified structure，the jet wake region elongated，and the profile of jet was in collapse state.Correlations of a liquid jet for nonuniform crossflow are presented.Nonuniform crossflow can improve atomization and uniformity，and Sauter mean diameter （SMD） reaches a minimum value when the velocity distribution is negative gradient.
Abstract: In view of the deposition of micro particles on the surface of turbine blades，the EI-Batsh deposition model was used to simulate the deposition of micro particles on the surface of turbine blades to explore the effect of pressure surface cooling jets on particle deposition characteristics.Results showed that，particles were mainly deposited on the leading edge and pressure surface of the blade，and the deposition rate increased with the particle diameter.However，when the particle diameter increased to 17 μm，the increase of deposition rate began to decrease.When there was a cooling jet，the collision rate of small particles can be affected by off and entrainment，thereby affecting the deposition rate.But there was basically no impact on the collision rate of large particles.The jet can also reduce the particle adhesion rate by cooling the wall surface，and affect the deposition rate in this way.The large-size particles were affected more obviously.After changing the blowing ratio，the particle deposition rate decreased first and then increased as the blowing ratio increased.
Abstract: When an aircraft flies at a high Mach number for a long time，the airflow in the boundary layer of the aircraft wall will generate aerodynamic heat because of strong friction，which can cause the temperature near the wall to rise or even exceed the temperature resistance limit of the material to the disadvantage of the aircraft.A lattice truss structure based on active cooling was designed to reduce the weight of the aircraft while achieving thermal protection effectively.At the same time，a semiconductor thermoelectric conversion device was added to the structure to convert the generated aerodynamic heat into electrical energy，which could be used to supply power for small electrical equipment of aircraft.The proposed integrated system of thermal protection and utilization was studied through experiment and the results showed that the power of thermoelectric conversion was much larger than the pump power consumption of the active cooling system，which can realize the self-driving of the active cooling system.Furthermore，the thermal protection performance of the actively cooled lattice truss structure was optimized by numerical simulation method，and the heat transfer effect was enhanced by adding the inner tube protrusions and the spiral twist.The results showed that the coupling of the inner tube protrusions and the twisted band can significantly improve the thermal protection performance of the system.At the flow velocity of 0.1 m/s，the maximum temperature of the outer and inner panels decreased by 14.4% and 17.8%，respectively，when water was used as working fluid，and 15.0% and 34.5%，respectively，when kerosene was used as working fluid.
Abstract: To deal with the dynamic performance of biaxial high bypass ratio turbofan engine with split flow in shaft fracture event and find out the first hazardous event after shaft fracture，the common working equation and performance model of high bypass ratio turbofan engine with split flow capable of simulating the dynamic response of airflow parameters in millisecond time scale were established based on the simulation platform independently developed.The dynamic response of airflow parameters was simulated in the order of milliseconds in the model.The transient response law and mechanism of gas path parameters of a civil turbofan engine with high bypass ratio under high and low-pressure shaft fracture in the take-off state and the cruise state were calculated and analyzed by using the model，which provided a basis for the design of passive safety.The results showed that the first hazardous events that occur within a few tens of milliseconds after the shaft fracture of the high and low-pressure shafts were the surge of the medium-pressure compressor and the over-rotation of the turbine rotor；at the same time，the temperature rose in front of the turbine.
Abstract: In order to evaluate the impact of different component design reliability，different operating environments and maintenance decisions on fleet operation and maintenance indicators （shop visit rate，shop visit cauce，mean time between removal，rate per flight hour，etc.），a model method for the probabilistic repair of aero-engine life cycle was proposed.Based on the life distribution of the potential reasons for repairs in different environments，and combined with maintenance decision rules and maintenance task costs，this method was employed to model the life cycle maintenance event probability of the fleet through discrete event simulation and Monte Carlo sampling.A simulation study was carried out on a typical commercial turbo fan engine.Under three different operating environments，the average shop visit rates of engines were 0.029 1，0.038 4 and 0.059 8，respectively，and the rates per flight hour were 82，91 and 119 dollars per flight hour，respectively.The simulation results showed the effectiveness of the proposed method.
Abstract: The fracture failure mechanism for new high temperature carburizing stainless aviation steel cylindrical gears was studied.The bending fatigue test for gear was carried out using“B test method”based on the stipulated GB/T 14230-1993.The results showed that the carbides in surface carburizing layer，the surface machining defects and interior carbides were main inducement factors in the tooth fracture failure.The carbides in surface carburizing layer were the most serious reason.When the carbides and surface machining defects did not exist in the surface，the interior carbides could be generated under alternating stresses，resulting in initiation and propagation for crack.The smaller size carbides generated the rough “fish-eye” zone morphology.In order to obtain the higher service life of new high temperature carburizing stainless aviation steel cylindrical gears，the size，amount，shape factor of the carbides and surface machining defects on the tooth surface should be controlled during the whole surface machining.The crack initiation in surface should be avoided.
Abstract: In view of the cutting chatter problem of thin-walled cylindrical workpieces，a combination of theoretical modeling，numerical simulation and experimental testing was adopted to study the influence of time-varying workpiece thickness and cutting position on the vibration characteristics of thin-walled cylindrical workpieces during the cutting process.The finite element method was used to establish the spindle-chuck-workpiece process system model.The influences of different wall thicknesses and cutting positions on the vibration mode and frequency response function of the thin-walled cylinder cutting system were analyzed.Through the modal experiment and the cutting vibration test，it showed that the shell mode of the thin-walled cylinder was more sensitive to the change of wall thickness，and the vibration response and main vibration mode of the process system at different cutting positions along the workpiece axis were different.It also verified that chatter textures of fish scales and grooves left on the surface were related to the low-order axial beam mode and circumferential shell mode of the thin-walled cylinder.The research results have a guiding effect on the prediction and suppression of chatter in machining of thin-walled workpieces.
Abstract: In view of the high-efficiency aerodynamic inverse design of the compressor cascade，an inverse design framework of the aerodynamic shape based on Gappy proper orthogonal decomposition （Gappy POD） was established.A certain type of compressor cascade was optimized through the Kriging surrogate model to obtain the aerodynamic optimization results，which were used as the basis of the inverse design goals.To further enhance the efficiency and accuracy，two improved methods based on adaptive snapshot replacement optimization and correction of the target pressure coefficient distribution were developed.The efficiency and accuracy of the basic Gappy POD combining these two improvement strategies were compared.Results showed that，the inverse design framework based on the adaptive snapshot replacement optimization process significantly improved the accuracy， and the root mean square error of the pressure coefficient distribution on the blade surface was reduced from 6.49×10-3 to 1.29×10-3.Correcting the target pressure coefficient distribution could improve the accuracy of the single inverse design.Combining the two improvement strategies for Gappy POD can achieve faster convergence speed with the same design accuracy，which can provide a new and efficient method for the reverse design of the geometric components of turbomachinery.
Abstract: A rapid method of compressor characteristics prediction with coupling inverse design and direct problems was proposed.According to one-dimensional meanline design theory of the compressor，the aerodynamics layout of the compressor was quickly obtained by solving the inverse problem to satisfy the design targets such as mass flow rate and pressure ratio.Then，by adopting the models of loss and deviation angle at off-design conditions，the compressor characteristics of the whole working condition were obtained by solving the direct problem.The aerodynamics layout was adjusted according to the deviation angle between the predicted characteristics and the targets，and the reasonable and rapid prediction of the compressor characteristics was realized through the coupling of inverse and direct problems.Moreover，a parameter calibration method of compressor loss and deviation angle model based on genetic algorithm was created.This method used optimization theory and experiment data of compressors to improve the traditional models of loss and deviation angle for enhancing the prediction accuracy of compressor characteristics.Experimental data of three compressors were used for calibration and validation of the proposal method.The results showed that the efficiency prediction errors at design and off-design conditions were 0.23% and 1.34%，which satisfied the requirement in the stage of requirement analysis and concept design for aero-engine.
Abstract: The combination of high dimensional model representation （HDMR） and support vector machine （SVM） in machine learning was proposed to optimize the twisted blade of centrifugal pump．A centrifugal pump with medium specific speed was selected as the research object．The three blade profiles of twisted blade were parameterized，the control variables were separated and the training space of surrogate model was determined.After algorithm learning of the hydraulic models of the twisted blade of the centrifugal pump，the surrogate model of the centrifugal pump with the blade profile parameters as the independent variables and the efficiency as the objective function was obtained．The prediction results of the surrogate model were verified by numerical simulation and experiment.The change of flow field in twisted blade impeller before and after optimization was analyzed from the view of kinetic energy equation．The results showed that at the design operating point，the numerical simulation efficiency of the optimized twisted blade centrifugal pump was 1.72% higher than that of the prototype pump，and the head was 0.41 m higher；the test efficiency was 1.5% higher than that of the prototype pump，and the head was 0.35 m higher than that of the prototype pump.
Abstract: For the riblet drag reduction，a neural network-based method was used to optimize the shape of the riblet surface.This work employed the channel flow model and the governing equations were the viscous incompressible Navier-Stokes （NS） equations.The turbulent flow inside the channel was resolved by the direct numerical simulation （DNS） method.According to the numerical method，a compact fourth-order central scheme was used for the discretization of the convective term，a fourth-order central scheme was applied to the discretization of the viscous term，and a third-order Runge-Kutta scheme was employed for the time advancement.In the neural network sub-optimization process，the constraint equation was the incompressible NS equation，and an adaptive controller based on online learning was used.In the optimization procedure，the control law was based on weakening the spanwise shear stress，and the control quantities were provided by the wall deformation.The optimization results demonstrated that the maximum wall drag reduction reached 17.41%.For the wall optimization，the turbulence intensity was reduced by 19.68%，besides，the vorticity and Reynolds shear stress at the wall also declined.Since the turbulent flow was unsteady，the shape of the optimized wall also varied with time，but the overall shape of the riblets still illustrated a streamwise riblet-like configuration.
Abstract: In order to study the strong howling problem caused by the modification of the boarding gate of an air-plane in flight，a two-dimensional irregular cavity model was established according to the actual flow characteristics by combining the flow characteristics of the fuselage surface and the actual configuration of the boarding gate seam cavity.The flow and noise characteristics of two types of boarding gate seam cavities with shoulder wall were numerically simulated by using the hybrid method of detached-eddy simulation and Ffowcs Williams-Hawkings integral equation，and the generation mechanism of pure tone noise at the boarding gate seam was analyzed.The results show that for the seam cavity with single shoulder wall，the increase of the length-depth ratio makes the interaction between vortices in the cavity intensify，and the pressure pulsation in the cavity becomes more intense，as well the total sound pressure level in the far-field increases by 3~10 dB on average，which indicates that the length-depth ratio of the cavity has obvious influence on the noise level.The irregular two-dimensional cavity model of an air-plane gate seam established accords with the physical reality，and the pure tone frequency by numerical calculation basically falls within the pure tone frequency range obtained by flight test，which can reflect the main physical characteristics of the airplane boarding gate howling noise.
Abstract: Based on the Navier-Stokes equation with strong conservation of compressible flow，the particle trajectory model （PTM） and shear stress transfer （SST） k-ω turbulence model were applied to calculate the gas-solid two-phase coupling by using the particle source method （PSIC） in the computational unit，and the three-dimensional two-phase flow field numerical calculation model of a type of solid rocket motor （SRM） with front and rear wings propellant at the ignition was established.The pressure field，velocity field，particle deposition mass concentrations and distributions under single-phase and two-phase conditions were compared and analyzed.The particle deposition mass concentrations in different parts of SRM combustion chamber and nozzle were studied，and the effects of different particle sizes，transvers and axial overloads were considered.The results showed that the solid particles produced by the front and rear wing SRM were mainly concentrated around the front wing，rear wing and the wall of the cylinder.With the increase of particle size，the particle deposition mass concentration on each monitoring surface increased.The transverse overload was positively correlated with the maximum particle deposition on the bearing surface，and the particle distribution on the bearing surface and the non-bearing surface was uneven.With the increase of axial overload，particles accumulated continuously along the overload direction，the escape rate increased，and the deposition decreased.The particle direction deflection caused by overload could affect the particle deposition mass concentration on the wall of combustion chamber and nozzle at the same time，which should be fully considered in the design of SRM insulation layer with front and rear wings charge propellant.
Founded in 1986,
monthly
Sponsor: Aviation Industry Corporation of China
Sponsored by: Chinese Society of Aeronautics Beijing University of Aeronautics and Astronautics
