2012 Vol. 27, No. 1

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Large eddy simulation of square duct turbulence based on the lattice Boltzmann method
WU Hong, WANG Jiao
2012, 27(1): 1-8.
Abstract PDF(1524KB) icon1994 icon449
Abstract:
Large eddy simulation(LES),based on the lattice Boltzmann equation (LBE),was used to study the square duct turbulent flow at a shear Reynolds number equal to 300 based on the hydraulic diameter and the friction velocity.The flow field was simulated by the multiple relaxation time lattice Boltzmann equation.The non-closure term after filtering was modeled by the shear improved Smagorinsky sub-grid stress model.To combine the lattice Boltzmann and large eddy simulation,the subgrid scales turbulent viscosity was related to the subgrid-scale relaxation time.Then the effective relaxation times were computed locally.The turbulent statistics quantities,including the mean streamwise velocity,mean second velocity,the root-mean-square velocity and the instantaneous streamwise voriticity on different sections,were computed.The comparison result,with the DNS and experimental data,shows that the LES based on the LBE can be used to study the bounded turbulent flow.
Experiments on aerodynamic and infrared radiation characteristics of film-cooling center-body exhaust system for a turbofan engine
SHAN Yong, ZHANG Jing-zhou, SHAO Wan-ren, SHANG Shou-tang, DENG Hong-wei
2012, 27(1): 9-15.
Abstract PDF(1992KB) icon1775 icon550
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For depressing the infrared radiation of the turbofan exhaust system,a 1/3 scaled model was constructed according one-type engine to investigate the plume temperature and infrared radiation for exhaust system with/without cooling center body,to validate the suppression capability of cooling center body.The experimental datum shows the temperature of the center body surface decrease under the bypass flow cooling.On the condition of bypass ratio 0.3,the infrared radiation intensity of the exhaust system with cooling center body depress by 24%~32% at the detected angle from 0° to 10° comparing to that of the baseline center body.When the bypass ratio increase to 0.8,the infrared radiation intensity of the exhaust system with cooling center body depress by 60% at the detected angle of 0°,and by 33%~51% at the detected angle of 20° to 90°.
Numerical investigation of thermodynamic performance on continuous detonation engines
ZHOU Rui, WANG Jian-ping
2012, 27(1): 16-24.
Abstract PDF(1504KB) icon2097 icon489
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Based on the two-dimensional(2-D) numerical simulation of continuous detonation engine in an annular chamber,the paths of fluid particles starting at the injection plate were tracked,and their thermodynamic condition was plotted on a p-v and T-s diagram.The main factors that affect the paths and the fluctuation of physical parameters were discussed in detail.The thermodynamic cycle efficiency and net work output were obtained from the diagrams.The numerical thermodynamic cycle diagrams show very similar structure to the ideal ZND(Zeldovich-Neumann-Doring) model.The superior performance of CDE(continuous detonation engine) is further defined.
Infrared radiation simulation of exhaust system by coupling FVM with narrow band k-distribution
ZHU Xi-juan, Eriqitai, LI Xi-xi, WANG Qiang
2012, 27(1): 25-32.
Abstract PDF(1103KB) icon1488 icon418
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A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media. The final infrared signature had considered the atmosphere effect, and the simulation values were favorably consistent with testing ones. The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%, it shows that when simulating the infrared radiation of the target which is received by the infrared detectors, even the calculation band is in atmospheric windows 3~5 μm, the effect of atmospheric transmission on infrared signature of the target should not be neglected.
Flow and air-fuel mixing processes in a premixed swirl combustor with LES
ZHENG Yun-zhe, ZHU Min, JIANG Xi
2012, 27(1): 33-40.
Abstract PDF(2323KB) icon2072 icon479
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Flow and air-fuel mixing processes in a premixed swirl combustor were studied with large eddy simulation (LES) method.Eddy viscosity model based on SGS(subgrid scale) turbulent kinetic energy model was selected to simulate the movement of vortex core,in order to characterize the qualitative development of coherent structures;with the introduction of unmixedness probability density function,the influences of inlet boundary conditions on eddy break-up and mixing were studied,especially the inlet velocity boundary condition;the correlation between velocity components and fuel mass fraction fluctuation shows the different velocity fluctuation factors for the mixing process.These conclusions provide useful information for further studying of premixed swirl combustor instability and pollutant emissions.
Genetic algorithm model-based optimization for float-wall with thermal-structural coupled
GAO Jian-hui, WEN Wei-dong, CUI Hai-tao
2012, 27(1): 41-47.
Abstract PDF(1647KB) icon1698 icon444
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Taking the float-wall as the object of study,combined genetic algorithm with exhaustive search,the thermal-structure coupling optimization of float-wall was researched by the way of two-step progression.Using genetic algorithm to carrying out install position optimization;then,using exhaustive search to optimize the thickness and the bolt diameter.A float-wall has more excellent capability was obtained;the stress index was decreased by 22.77%.The results show that the optimal technology applied in optimal design of float-wall is effective and reasonable.
Experiment of outlet temperature distribution of a reverse-flow annular combustor
LIU Fu-qiang, FANG Ai-bing, CUI Yu-feng, XU Gang, ZHU Jun-qiang, NIE Chao-qun
2012, 27(1): 48-54.
Abstract PDF(1541KB) icon1663 icon451
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An experiment on the outlet temperature distribution of an aero-engine reverse flow annular combustor was performed under several different working conditions.Outlet temperature distribution factor and radial temperature distribution factor were obtained.Temperature distribution along the height of turbine guide vane was studied in detail.A new concept called local sector radial temperature distribution along the height of turbine was proposed and it was recommended that when assessing the temperature factor it should be taken into consideration.The experiment results provide significant promotion for the evaluation and optimization of the outlet temperature distribution.
Numerical simulation of a novel turbine inter-vane burner
LI Ming, TANG Hao, ZHANG Chao, CHENG Ben-lin, MO Da
2012, 27(1): 55-62.
Abstract PDF(2183KB) icon1931 icon544
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To improve the performance of gas turbine engines,a turbine inter-vane burner (TIB) was designed.The Realizable k-ε turbulent model,probability density function(PDF) combustion model, discreate ordinates(DO) radiation model and discreate phase model (DPM) of FLUENT were used to simulate the turbulent flow and combustion in the burner.It’s observed that the TIB can increase the gas temperature by about 700K with 98.4% combustion efficiency and 4.2% absolute pressure loss.The radial temperature grows linearly with the dimensionless height.The distribution of the velocity,temperature and species are controlled by the degree of mixing of the combustion products and the main flow.Given the radial vane cavity (RVC) plays an important part in improving the outlet temperature profile,its shape deserves more study.Compared to the literature experimental data,it indicates that the mathematical models and numerical methods are reasonable and the numerical results provide an important reference to the design of TIB.
Characteristics of flow distribution of aviation kerosene in parallel pipes under supercritical pressure
RAN Zhen-hua, XU Guo-qiang, DENG Hong-wu, ZHANG Chun-ben, ZHU Kun, HUANG Wen
2012, 27(1): 63-68.
Abstract PDF(983KB) icon1916 icon571
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Flow distribution characteristics of China No.3 kerosene (RP-3) in vertical parallel U-turn tubes were experimentally investigated under supercritical pressures.Based on the experimental results,the effects of temperature,pressure and asymmetrical heat flux to the flow distribution characteristics of the RP-3 were analyzed.In the experiments,the inner and outer diameters of the test tube are 1.8mm and 2.2mm respectively;the mass flow rate is maintained at 4g/s under the pressure from 3 to 5MPa,and the heat flux changes from 60 to 240kW/m2.The test results indicate that static unsteady phenomenon will be induced when fuel temperature is close to its pseudo-critical point under the lower pressure,which leads to flow imbalance and flow redistribution between the two tubes.In addition,the mass flow in the branch tube is significantly affected by the non-uniformity of heat flux,and the system stability can be improved effectively by the increase of pressure and which will inhibit the flow distribution differences in the parallel pipes.
Resonance demodulation technique based on IHT for rolling bearings fault diagnosis
DENG Si-er, WANG Yong, WANG Heng-di
2012, 27(1): 69-74.
Abstract PDF(1130KB) icon1892 icon455
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Aiming at the limitations of traditional demodulation methods for extracting the fault feature of rolling bearing vibration signal,combining iterated Hilbert transform (IHT) with resonance demodulation technique,a new method about rolling bearing fault diagnosis was proposed.Firstly,the original vibration signal was decomposed into some component signals of envelope amplitude by iterated Hilbert transform,which contain fault characteristics;then,the high frequency interference noise was eliminated and frequency multiplication spectrum was obtained by resonance demodulation technique;finally,fault type was determined by contrast with theoretical fault frequency.The experimental results show that the approach can be applied to the roller bearings fault diagnosis effectively.
Non-probabilistic analysis on aero-engine rotordynamics
WANG Jun, HONG Jie, CHEN Meng, MA Yan-hong
2012, 27(1): 75-81.
Abstract PDF(948KB) icon1789 icon470
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A non-probabilistic-interval analysis method,which solves the rotordynamics with these uncertain parameters,was presented.Based on interval mathematics and perturbation method,interval analysis method simplified the uncertain parameters such as support stiffness and connecting structure stiffness to interval vectors,so that it could get the intervals within which the rotordynamics varied when less information of structure was known.The formulation of natural frequencies of rotor using interval perturbation analysis method was formulated.A numerical example of comparison between interval perturbation method analysis and monotonic method was given.The rotordynamic analysis of a turbofan rotor was performed with this method.The present interval perturbation method is more accurate than determined method in rotordynamic analysis,and it decreases the requirement of uncertain parameters,such as distribution characteristic.
Compressive behavior of composite panels with deeply embedded delamination
FU Hui-min, PENG Bo
2012, 27(1): 82-88.
Abstract PDF(1401KB) icon1426 icon423
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The compressive behavior of laminates with a deeply embedded circular delamination was studied numerically and experimentally. In the finite element analysis (FEA),virtual crack closure technique (VCCT) and B-K law were employed to simulate the delamination growth,and the contact of the two substrates was considered.The effect of the delamination size and through-thickness position on the compressive behavior of laminates with an artificially embedded circular delamination was discussed.It is found that the through-thickness position affects the buckling mode,which then strongly influences delamination growth speed and direction,as well as the dominant component energy release rate (ERR).The numerical results agreed well with the experimental results.
Collaborative optimization of heat dissipation and load capacity for sandwich structures with carbon fiber reinforced lattice truss cores
ZHANG Lei, QIU Zhi-ping
2012, 27(1): 89-96.
Abstract PDF(895KB) icon2046 icon439
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The overall heat transfer coefficients and equivalent pressure loss of lattice truss sandwich structures were derived in analytical forms as well thermal performance index was defined in heat dissipation analysis.The overall effective stiffness of lattice truss sandwich structure was analyzed by continuum method combined with classical lamination theory and series parallel model.Multifunctional collaborative optimal design for sandwich structures with carbon fiber reinforced lattice truss cores was presented with satisfying heat dissipation and load capacity constraints,the optimum weight of sandwich structures was obtained using discrete hybrid optimization method based on branch and bound approach.The results demonstrate that pyramidal lattice truss sandwich structures provide higher levels of heat dissipation efficiency and load capacity,more ultralight and efficiently,by analyzing and comparing different types of truss cores.
Structural design optimization method and program implementation for a hollow fan blade
YANG Jian-qiu, WANG Yan-rong
2012, 27(1): 97-103.
Abstract PDF(777KB) icon1971 icon674
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A bi-objective optimization model for a hollow fan blade was established for the purpose of minimizing the mass and radial displacement with the constraint of maximum Von Mises equivalent stress,based on the structural analysis of a hollow fan blade.The effects of design variables on the constraint function and objective functions were studied using orthogonal experimental design method,and the number of design variables was reduced as a result.The response surface metamodels of constraint function and objective functions were constructed using radial basis function method so as to improve the efficiency of structural design optimization and avoid a lot of finite element analysis during the optimization process.An example was solved for the purpose of studying the applications of metamodels and elitist non-dominated sorting genetic algorithm (NSGA-Ⅱ) for the bi-objective structural design optimization of a hollow fan blade,then a group of uniform Pareto solutions and some recommended optimal results of a hollow fan blade example were obtained.
Creep property variation at different regions on a directionally solidified turbine blade
DENG Ying, SUN Rui-jie, XIE Jian-wen, YAN Xiao-jun
2012, 27(1): 104-109.
Abstract PDF(883KB) icon1465 icon436
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In order to study the creep property variation at different regions on a directionally solidified (DS) turbine blade caused by microstructure difference among those regions,three types of DS specimen (platform-like specimen,shroud-like specimen and sheet specimen) were presented to investigate the difference by creep rupture tests at elevated temperature.The tests data shows that the performance of platform-like specimen and shroud-like specimen are 94.22% and 75.65% of sheet specimens' performance,respectively.Therefore,the difference of creep property among different regions on a DS turbine blade should be considered in blade structure design and creep life assessment.The research results may also help to improve the manufacture processes of directional solidification.
Bayesian reliability demonstration test design for binomial distributed product
FENG Wen-zhe, LIU Qi
2012, 27(1): 110-117.
Abstract PDF(541KB) icon1674 icon446
Abstract:
The requirements and constraint conditions of reliability statistical demonstration test design for binomial distributed product were analyzed.Considering the producer's risk and consumer's risk,reliability test cost,the reliability test design model based on test loss (RTDMTL) was constructed for the reliability test design of binomial distributed product.To given sample size,according to 0-1 loss function,the acceptable maximum failure number calculation method was presented under the principle of minimize the posterior expect loss.According to average risk criteria,the formulas of producer's risk and consumer's risk were deduced.To the solution of RTDMTL,the steps of optimum test plan calculating numeric algorithm were given by Matlab software.At last,an example was given to show the validity of the proposed method.
Simulation research of the CRGT cycle gas turbine performance
ZHENG Hong-tao, ZHANG Yu-long, YANG Ren
2012, 27(1): 118-123.
Abstract PDF(940KB) icon1910 icon446
Abstract:
Design and off-design performance of the different cycle in one certain three -spool gas turbine,with the combination programming method of VC and MATLAB was analyzed.Among it,used the modification engineering algorithm method to program the computation procedure of the working medium's thermodynamic properties,used the BP (back propagation) neural network method to build the calculation models of the compressor and turbine component characteristics;used the modular modeling method to build the dynamic simulation models of the simple cycle,the STIG(steam injection gas turbine) cycle and the CRGT(chemically recuperated gas turbine) cycle.The calculation results show that the STIG cycle and CRGT cycle can both reduce the combustor exit temperature and improve total thermal efficiency,in which the simple cycle's efficiency was 35.16%,the STIG cycle was 45% and the CRGT cycle was 52.8%;and in order to ensure the efficiency and the application areas,this CRGT cycle units can be used in the seawater desalination systems,under the safe operation areas and without the redesign of the components.
Numerical study of compression corner flowfield using Gao-Yong turbulence model
GAO Ge, ZHANG Chang-xian, YAN Wen-hui, WANG Yong
2012, 27(1): 124-128.
Abstract PDF(556KB) icon1684 icon422
Abstract:
A numerical simulation of shock wave turbulent boundary layer interaction induced by a 24° compression corner based on Gao-Yong compressible turbulence model was presented.The convection terms and the diffusion terms were calculated using the second-order AUSM (advection upstream splitting method) scheme and the second-order central difference scheme,respectively.The Runge-Kutta time marching method was employed to solve the governing equations for steady state solutions.Significant flow separation-region which indicates highly non-isotropic turbulence structure has been found in the present work due to intensity interaction under the 24° compression corner.Comparisons between the calculated results and experimental data have been carried out,including surface pressure distribution,boundary-layer static pressure profiles and mean velocity profiles.The numerical results agree well with the experimental values,which indicate Gao-Yong compressible turbulence model is suitable for the prediction of shock wave turbulent boundary layer interaction in two-dimensional compression corner flows.
Dynamic stability for maneuver flight of bumblebee
ZHU Dan, HU Ming-lang, WANG Qiang
2012, 27(1): 129-136.
Abstract PDF(1114KB) icon1681 icon489
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In allusion to the fact that current flight dynamic analysis of insect is limited to steady flight,the maneuver flight stability of bumblebee is analyzed with bifurcation analysis.The coupling stability of saccade and turning in maneuver flight is studied by analyzing the stability and stability field of different equilibrium point.Then get the global stability of saccade and turning at different forward speed.As the results have put it,turning at hovering is global stability and existing only and one stable focus when 14.23rad/s<| r |<23.8rad/s;turning at flying velocity are 2.5m/s and 4.5m/s is unstable,which explains why the insects are to reduce speed before turning;the bumblebee saccade at different forward speed are unstable and enter sharply unstable oscillation.However,there exists a transition time of 30 flapping period,which is enough for bumblebee to adjust.
Prediction of airfoil airload at low Mach numbers based on state space formulation
SHAO Song, ZHU Qing-hua, ZHANG Cheng-lin, NI Xian-ping
2012, 27(1): 137-144.
Abstract PDF(1031KB) icon1958 icon566
Abstract:
The Leishman-Beddoes (L-B) unsteady and dynamic stall model is applicable to the medium Mach numbers(Ma>0.3),and some inconsistent problems for predicting airfoil airload when comparing with airfoil airload test data at low Mach numbers (Ma<0.3),so firstly the unsteady and dynamic stall aerodynamic behavior of airfoil at low Mach numbers was investigated,secondly the modified L-B model was set from the viewpoint of the variation of the flow on the airfoil surface,finally the comparisons between the modified L-B and airfoil airload test data at low Mach numbers show that the modified L-B model with state space formulation is accurate and can be used to predict the airfoil airload at low Mach numbers,and also it can be easily incorporated into a helicopter comprehensive code.
Influence of cascade configuration on aerodynamic performance of a cascade thrust reverser
ZHANG Guo-dong, WANG Qiang
2012, 27(1): 145-151.
Abstract PDF(1448KB) icon1904 icon449
Abstract:
The study chose equal-thickness shaped cascade blades,with the technology of hybrid grid system,and studied the influence of inlet flow angle,transition-radius,axial space between upside and underside of vane,solidity and outlet flow angle on the mass flow and axial reverser thrust.The final computation results show:the inlet flow angle,transition-radius,axial space between upside and underside of vane play the important role in whether the fan flow inducts the cascade smoothly;the solidity affects the outlet area and diverted performance of cascade;the outlet flow angle is a key-factor of design of the cascade thrust reverser,so it gives direction to the aerodynamic performance of a cascade thrust reverser.
PIV investigation of the internal flow in a multi-stage compressor rotor
WANG Zhi-qiang, HU Jun
2012, 27(1): 152-159.
Abstract PDF(1295KB) icon1659 icon474
Abstract:
PIV(particle image velocimetry) was utilized to measure the flow field of the blade passage in a rotor of multistage turbomachinery,and was successfully applied to a four-stage large-scale low-speed compressor facility.In order to apply the PIV to compressor facilities,a light sheet periscope probe and a phase-lock system have been developed.The flow field of the third stage rotor blade passage has been measured at the design condition.Compared with the 3-D (three-dimentional) steady Navier-Stokes(N-S) solution,the measurements at the compressor design point show that the PIV measurement results reflect the flow structure of the third stage rotor blade passage reasonably.There is a big tip leakage vortex,which occupies the tip region of the rotor blade passage.There is no abnormal velocity filed and no obvious flow separation phenomenon at the other region of the rotor blade passage.
Effect of labyrinth-honeycomb seal of shrouded rotor blades on the aerodynamic performance of the turbine stage
GAO Jie, ZHENG Qun, LI Yi-jin
2012, 27(1): 160-168.
Abstract PDF(1836KB) icon1873 icon582
Abstract:
A commercial CFD(computational fluid dynamics) software was used to research the effect of rotor labyrinth-honeycomb seal leakage on the main flow in a 1.5-stage axial turbine.Effects of rotor seal leakages on the main flow,and mixing between leakage and main flows on the downstream stator with different tip clearances were analyzed;in addition,the effect of labyrinth seal with and without honeycomb facings on the aerodynamic performance of turbine stages was compared.The simulation results show that,mixing between leakage and main flows leads to velocity deflection in the mixing zone,and the suction side incidence of the re-entering leakage flow in the subsequent stator causes additional losses.The re-entering leakage flow in the subsequent stator which has a high radial velocity,alters the flow structure of the upper half channel,and causes extra secondary losses,besides,the losses are increasing with a growing tip clearance.The honeycomb acts to kill swirl velocity development for the rotating labyrinth-honeycomb seal due to the specific hexagon structure,which weakens the flow over the circumferential direction.Thus,it decreases the velocity gradients produced by the different velocity components of main and leakage flows,and the mixing of the leakage jet and main flow is greatly decreased.The honeycomb changes the flow pattern of labyrinth-honeycomb seal which leads to a reduction in leakage compared to the labyrinth seal.
Influence of tip clearance size on flow losses of a transonic high pressure turbine stage
WANG Da-lei, PIAO Ying
2012, 27(1): 169-175.
Abstract PDF(1106KB) icon1915 icon456
Abstract:
The influence of the tip clearance height of turbine rotor blades on the aerodynamic performance and secondary flow losses of an axial turbine stage were investigated by numerical simulation and different tip clearance heights were taken into account.Results show that the efficiency of the turbine stage would decrease markedly due to the increase of the tip clearance height.The efficiency would decrease 1.8% as the tip clearance height increased 1% of blade relative height.Analyses of the rotor flow field indicated that as the height if tip clearance increased,the distribution of flow losses changed in the upper passage of the rotor.The most losses were induced in the region between the middle of the rotor blade and the trailing edge,while secondary flow losses increased most behind the trailing edge.Mixing losses were the main factors which led to the efficiency decreased as the height of tip clearance increased.
Boundary layer behaviors on an ultra-high-lift low-pressure turbine profile under unsteady wakes
LI Wei, ZHANG Bo, ZHOU Min, LU Xin-gen, ZHU Jun-qaing
2012, 27(1): 176-182.
Abstract PDF(1315KB) icon1661 icon544
Abstract:
An experimental investigation on unsteady boundary layer behaviors of the suction surface of an ultra-high-lift low pressure turbine profile under periodically unsteady wakes was conducted with the help of surface-mounted hot film,and the influence of the wake-boundary layer interaction on the boundary layer separation,transition and reattachment was analyzed in detail with space-time (S-T) diagrams of quasi-wall shear stress and statistical parameters.The experimental results show that the wake has a significant influence on the boundary layer of turbine profile and the separation has been remarkably suppressed despite the larger separation bubble on the suction surface of ultra-high-lift profile at low Reynolds number.
Optimization design of the error sensitivity for spiral bevel gears
SU Jin-zhan, FANG Zong-de
2012, 27(1): 183-189.
Abstract PDF(720KB) icon1760 icon400
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In order to improve the sensitivity of spiral bevel gears caused by assembly errors,the optimization total curvature of different surface was applied from the tooth surface topology structure.The total curvature of two meshing surface contact points which orients lengthwise,can be considered as sensitivity coefficient,and the effect of reference point sensitivity coefficient of local synthesis and location parameters was investigated.The machine-tool settings of pinion which reduce sensitivity of assembly errors can be obtained by the optimization of the first order gear ratio,contact path direction,sencond order modified and third roll coefficient.The numerical example reveals that sensitivity coefficients of whole mesh cycle is controlled in comparatively small range,the amplitude and symmetry of transmission curve can be achieved to design requirements,the meshing quality can be improved.
Steady-state properties of gas film seal damper used in a rotor system
WANG Hong, HONG Jie, MA Yan-hong
2012, 27(1): 190-197.
Abstract PDF(1125KB) icon1840 icon491
Abstract:
In order to describe the movement of rotor system in an aero-engine that combines the rotation and procession together,the Reynolds equation of gas film seal damper (GFSD) was deducted.The fluid-solid coupling relationship among rotor,gas film and metal rubber ring was constructed based on the movement equation and displacement coordinated relationship,so the solution process of steady-state pressure field was clear and the design method for the stiffness of metal rubber was put forward.The finite difference method was employed to solve the steady-state pressure field,and the effects of working parameters and structural parameters on the steady-state properties were analyzed,which could provide references for the structural design of GFSD,and finally the mass flow-rate between GFSD and straight labyrinth seal was compared.The results show that the appropriate stiffness of metal rubber can make GFSD adjust the clearance of gas film adaptively.In order to maintain a dynamic lubrication condition,the larger the ratio of length and diameter,and the smaller the stiffness of metal rubber and clearance of gas film is,the better the steady-state properties are.The mass flow-ratio of GFSD is much less than that of straight labyrinth seal,and therefore GFSD could meet the requirements of the seals in advanced aero-engines.
Study on meshing characteristics of face gear drive with arcuate tooth based of manufacture on NC machine
CAI Xiang-wei, FANG Zong-de, SU Jin-zhan
2012, 27(1): 198-202.
Abstract PDF(926KB) icon1724 icon439
Abstract:
Numerical control machining of face gear with arcuate tooth has been proposed,and the meshing characteristics was investigated.Tooth surface equation that was based on the concept of imaginary gear cutter has been derived,flank modification had also been considered;the machining principle in the general multi-axle numerical control machine tool was created by using coordinate transformation,then the polynomial expression of the motion axes can be obtained;tooth contact analysis(TCA)model under different assembly conditions was established.The numerical results reveal that the bearing contacts are not sensitive to the errors of misalignments,and a more favorable type of parabolic function of transmission errors with better symmetry and reduced amplitude may be obtained according to the modification of the face gear.
Research on the surge elimination control system design and test for aero-engines
ZHANG Shao-Ji, LIU Shi-Guan
2012, 27(1): 204-210.
Abstract PDF(692KB) icon1938 icon446
Abstract:
The design method of an aero-engine surge elimination control system and the forced surge tests were discussed,especially a digital simulation of the surge elimination controller in loop was developed in this paper.The test results in both engine rig test and flight test show that,the control parameters can be optimized through the control system digital simulation test,then a reliable aero-engine surge elimination control system can be developed.
Multivariable chaotic arithmetic for aero-engine performance forecasting based on boundary values
SHI Yong-sheng, PENG Peng, SONG Yun-xue
2012, 27(1): 211-217.
Abstract PDF(886KB) icon1787 icon580
Abstract:
Firstly,the boundary values of exhaust gas temperature(teg) was extracted from the original exhaust gas temperature data series.Further analysis on the boundary values data series indicated that there existed a chaos feature in it.Then,chaotic forecasting arithmetic based on multivariable phase space reconstruction was established to forecast the data series.Finally,by comparing the series with the red line,the condition of aero-engine was defined.The proposed arithmetic was verified through some type of aircraft aero-engine teg data series obtained from actual flight.The result shows that the proposed arithmetic can reduce the time complexity and has a better forecast accuracy in the prediction of outliers.It can be used as a supporting model in the decision making of this aero-engine fault forecast.
Investigation on working course of supersonic self-ejector
ZHANG Min-qin, ZHANG Zhong-li, ZHOU Li-xin, ZHANG Meng-zheng
2012, 27(1): 218-224.
Abstract PDF(1113KB) icon1604 icon473
Abstract:
The analysis model of self-ejector(ejector for short,including cylindrical ejector and second-throat ejector) was set up in liquid rocket engine.The two equation κ-ε model was employed to simulate the turbulence.The performances and the flow field features of cylindrical and second-throat ejector were gained in same gap.According as these flow fields,the site of the shock wave,the full flow in nozzle,the coefficients of ejecting were calculated.The numerical value was compared with hot fire test value in vacuum cabin,both are same.
Simplified analytical models for performance prediction of valveless pulsejet
WEI Tao, WU Xiao-song, CAI Wen-xiang
2012, 27(1): 225-232.
Abstract PDF(561KB) icon3478 icon500
Abstract:
The simplified physical and mathematical models of the working process in valveless pulsejet based on the analysis of such engine cycle were proposed.The flow principle of combustor of charging process and the relationship of the mean velocity of discharge with thermodynamic parameters and combustor pressure were achieved,then the equations of the operation frequency and mean thrust were given.The results show that non-dimensional mean velocity of discharge increases with the increase of the compression ratio,and tendency is mitigated;the errors between the results of operation frequency and mean thrust models and experimental data are less than 10% and ±17%;in addition,the equation of thrust is suitable for valved pulsejet.The study shows that presented simplified analytical models are reasonable,and the accuracy is acceptable.The conclusions offer instruction for designing,experiment,predicting the performance and optimization method of valveless pulsejet.
Safety research on unmanned aircraft system for airworthiness
DING Shui-ting, BAO Meng-yao, DU Fa-rong
2012, 27(1): 233-240.
Abstract PDF(1076KB) icon2261 icon484
Abstract:
Aiming at safety requirement for unmanned aircraft system(UAS),it was initially demonstrated that current safety assessment process and methodology based on regulation and reference for manned aircraft were limited for UAS because of its unique features.In views of this principle,some improvements for UAS safety assessment were proposed:(1) take consideration of UAS including the unmanned aerial vehicle and assured equipments,and enlarge the scope of safety assessment during functional hazard analysis at system level;(2) take consideration of the feature that pilot and unmanned aircraft are physically separated,and reclassify and redefine the serious level of UAS failures.(3) consider that the quality of take-off has a huge impact on system,and the safety analysis must be conducted for two key events-‘air collision’ and ‘ground impact’.The result indicates that the above improvements are in accordance with features of UAV and ensures safety through establishing targeted safety level.

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