2012 Vol. 27, No. 8

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Capability compare of twin annular premixing swirler with the single annular and dual annular combustor
LI Feng, CHENG Ming, SHANG Shou-tang, LIU Dian-chun, ZHANG Shan-shan, SONG Bo
2012, 27(8): 1681-1687.
Abstract PDF(823KB) icon2991 icon875
Abstract:
Diffuser,outer case and exit dimensiom kept the same with single annular combustor(SAC)and dual annular combustor(DAC),redesigned the combustor from a single annular structure into twin annular premixing swirler(TAPS)combustor in central classified.Taking the same physical models(including the turbulence,radiation,spray and emission model),three-dimensional reaction flow simulation in TAPS combustor,SAC and DAC were developed in the fluent code.The total-pressure recovery coefficient,combustion efficiency,temperature distribution of the combustor exit and NOx/CO emission profiles were calculated.Finally,the capability of TAPS combustor,SAC and DAC were campared.The results show that,by using the TAPS combustor,the total-pressure recovery coefficient,combustion efficiency was improved compared with the SAC and DAC,the temperature distribution coefficient of the combustor exit and NOx emission is lower than SAC and DAC.So the conclusion could be drawed that the technical advantages of TAPS combustor is obvious,and the TAPS combustor is a good high temperature rise and low emission combustor.
Ignition and combustion characteristics of surrogate fuels for kerosene
ZENG Wen, CHEN Xiao-xiao, LIU Jing-chen, MA Hong-an
2012, 27(8): 1688-1695.
Abstract PDF(1664KB) icon2258 icon752
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Three new surrogate fuels (n-decane,the mixed fuel of n -decane and 1,2,4-trimethylbenzene,the mixed fuel of n -decane and toluene) for kerosene(Jet A-1) were chosen,and detailed reaction mechanisms (67 species and 344 reactions for n -decane,118 species and 527 reactions for the mixed fuel of n -decane and 1,2,4-trimethylbenzene,and 84 species and 440 reactions for the mixed fuel of n -decane and toluene) for the ignition and combustion of these three surrogate fuels were analyzed.The ignition characteristics and the premixed combustion processes of these three surrogate fuels in the shock tube and the perfectly stirred reactor were simulated especially,and the simulation results were compared with the experimental data.Furthermore,the effect of volume percentage of two species in the mixed fuel on the ignition and premixed combustion characteristics were analyzed.The results show that these two mixed fuels represent the ignition and combustion characteristics of Jet A-1 more accurately than n -decane single fuel does.At the same time,the effect of volume percentage of two species in the mixed fuel on the ignition and premixed combustion characteristics are remarkable.
Effect of unsteady wake transportation on film cooling flowfield of rotating turbine blade
ZHOU Li, WEI Wei, CAI Yuan-hu
2012, 27(8): 1696-1703.
Abstract PDF(1969KB) icon1717 icon724
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Unsteady flowfield of the turbine blade with film cooling was investigated numerically under different blowing rates with the wake simulated by the cylinder rod.The effect of unsteady wake transportation on the film cooling flowfield was analyzed.Results show a zone with low velocity forms due to the total pressure defection and velocity defection.The disturbance of the unsteady dominates the formation of the cooling film when the unsteady wake is transported to the position near the cooling hole,which results in the obvious reduction of the cooling effectiveness near the cooling hole.The cooling gas can be transported to the farther downstream region due to effect of the unsteady wake,and the recovery range of the cooling gas along the spanwise direction is wider than the time without unsteady wake passing,therefore better cooling effectiveness exists on the pressure surface when the unsteady wake is transported to the position near the cooling hole on the pressure surface.The effect of the unsteady wake on the cooling effectiveness increases with the increment of the width of the unsteady wake.The effect of the unsteady wake is larger on the pressure surface than that on the suction surface.
Effect of equivalence ratio on flow and combustion characteristics of super-sonic combustor with cavity
JIA Zhen, WU Di, PIAO Ying
2012, 27(8): 1704-1711.
Abstract PDF(1445KB) icon1918 icon593
Abstract:
Numerical simulation on effect of equivalence ratio on flow field and combustion characteristics of supersonic combustor with cavity under the condition with/without chemical reactions was conducted by adjusting the fuel injection pressure to reach a certain equivalence ratio value.It is found that increasing equivalence ratio enhances combustion backpressure,expands the upstream boundary layer separation zone,and pushes shock train to the entrance of the combustor gradually.Also,enlarging equivalence ratio increases jet penetration depth gradually.In the field near fuel injector ,mixing performance was obviously enhanced by increasing equivalence ratio,while in the field far away from fuel injector,little effect was induced by equivalence ratio.In the aspects of total pressure loss and cavity drag coefficient,they had proportional relationships with equivalence ratio.
Inverse method investigation of thermal radiation property of liquid hydrocarbon fuel
LI Dong, AI Qing, XIA Xin-lin
2012, 27(8): 1712-1717.
Abstract PDF(835KB) icon1518 icon750
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The spectral transmittance radio calculation model of glass- liquid hydrocarbon fuel-glass three layer slabs was developed based on ray trace method,and an inverse model was built to determine the thermal radiation property (k is extinction coefficient and n is refractive index) of liquid hydrocarbon fuel in the three layer slabs.The inverse model was retrieved,and was combined with Monte-Carlo method and area approach method.The thermal radiation property of heptane attained in the references was selected as the true values,and the spectral transmittance radio of the three layer slabs based on the direct model simulation was regarded as the experimental values.The thermal radiation property of Heptane was achieved by the inverse model,and then the effect of measurement error on the inverse results was also investigated.The results show that, (1) the standard deviation of k calculation error by the inverse model is less than 0.003%,and that of n is higher than 21%. (2) the effect of measurement error on the inverse results is urgent distinct,and some inversed calculation values are obviously when the measurement error is higher than 1%.(3) the standard deviation of k calculation error and measurement error y satisfy the equation which is y =2285.2 γ2-10.484 γ +0.0037.The effect of measurement error on the standard deviation of n calculation error is lower,however,the n calculation error is higher than 20% when the measurement error exists.
Numerical study and verification on combustion characteristics of afterburner with chevron mixer
DI Hu-wei, SHAN Yong, GAO Jia-chun, ZHANG Jing-zhou, LIU Tao
2012, 27(8): 1718-1725.
Abstract PDF(2271KB) icon1939 icon585
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Based on computational fluid dynamics(CFD),the two-phase turbulent combustion in a three-dimensional afterburner with a kind of curved chevron mixer was simulated.Eddy-dissipation,finite-rate/eddy-dissipation and eddy-dissipation-conception models were applied to the combustion simulation,respectively.Numerical results indicate that abundant streamwise vortices,which enhance the mixture between the core flow and bypass flow,form and develop along the downstream of the curved chevron mixer.The intensity of streamwise vortices deduced by curved chevron mixer always is greater than that of the straight chevron mixer.Therefore,the mixing efficiency of curved chevron mixer is the best.The eddy-dissipation model is the most realizable based on the distribution of O2 and CO2.
Numerical study of auxiliary power unit annular backflow combustor
LIN Zhi-yong, YAN Ying-wen, LI Jing-hua, ZHU Jia-wei, CHEN Li-qiang, KONG Zu-kai
2012, 27(8): 1726-1733.
Abstract PDF(2493KB) icon1947 icon636
Abstract:
The influences of different inlet conditions (including inlet temperature and inlet fuel air ratio) on two phase spray combustion flow of auxiliary power unit (APU) combustor were studied by using Fluent software.Standard k-ε model was applied to simulate the turbulent viscosity.The fuel droplet trajectories were modeled in Lagrangian frame of reference by using discrete phase model (DPM).Non-premixed combustion model was used to model turbulence-chemistry interaction.The results reveal that the outlet temperature raise with the increase of inlet temperature and fuel-air ratio,but distribution of temperature is similar.The numerical data agree well with experimental data,which show that the numerical model and method can be used to predict two phase spray combustion flow of APU.
Adaptive extended incremental Kalman filter method
FU Hui-min, WU Yun-zhang, LOU Tai-shan
2012, 27(8): 1734-1737.
Abstract PDF(410KB) icon1834 icon565
Abstract:
Based on extended incremental Kalman filter (EIKF) and adaptive incremental Kalman filter (AIKF), the adaptive extended incremental Kalman filter (AEIKF) and analysis method were put forward, the key calculative steps were established. The measurement equations have many uncertainties and can't obtain precision parameters in actual environment(such as deep space exploration). Due to environmental factors and the instability of measurement equipments, the measurement data have unknown time-varying system errors in actual engineering, which leads to greater Kalman filtering error. Ultimately, the convergence of Kalman filter were reduced. The presented adaptive extended incremental Kalman filter method can successfully eliminate these unknown system errors. The method can estimate statistical characteristics of noise in real time and greatly improve the accuracy of filter. The method is simple to calculate and easy to apply in engineering.
Single-disc rotor nonlinear vibration model and mechanism
YANG Jin-fu, WU Min
2012, 27(8): 1738-1745.
Abstract PDF(1067KB) icon1903 icon735
Abstract:
Based on mechanical properties of rotor nonlinear vibration and the assumption of large deformation,the rotor nonlinear vibration model in the form of Duffing equation was constructed from typical engineering problem.According to analytical solutions of Duffing equation,system's equivalent frequency and frequency response equation were derived.The system's vibration influences of stiffness components,damping components and nonlinear components were studied.The single-disc rotor nonlinear vibration experimental results verified the rationality and efficiency of nonlinear vibration model's construction and Duffing equation's analytical solution and frequency response equation.The mechanisms of resonance,amplitude jump and hysteresis are revealed.It provides a new research method for rotor vibration characteristics analysis.
Four-parameter life prediction method
NING Xiang-rong, CHEN Wei, CAI Xian-xin, LIAO Xue-jun, MI Dong
2012, 27(8): 1746-1751.
Abstract PDF(651KB) icon1946 icon646
Abstract:
Four-parameter life prediction method for helicopter transmission system was studied.Four-parameter stress-number of cycles (S-N) curve was presented first,and then,the derivation of helicopter transmission component safe S-N curve from material mean S-N curve and the scheme for the component life prediction were introduced in detail.Multi-load coordinating loading technology in fatigue test and a tail gear box(TGB) casing full-scale fatigue test were introduced at the same time.Finally,according to the full-scale fatigue test result and flight load survey data,applying the four-parameter life prediction method,the TGB casing life prediction was performed,which indicates that four-parameter life prediction method is a reliable and effective method and is worth to be generalized.
Chaotic prediction of metal rubber damper for occurred chaos
TANG Guo, CHEN An-hua, GUO Yuan-jun
2012, 27(8): 1752-1757.
Abstract PDF(333KB) icon1649 icon571
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The nonlinear dynamics equation of a metal rubber damper with nonlinear stiffness and nonlinear hysteresis resilience was proposed.According to non-linear vibration theory,the average equation of slowly-varying parameters was obtained in the weakly nonlinear case.The discrete mapping of the status equation of harmonic wave slowly-varying parameters was developed.The analytical condition of occurred chaos for metal rubber damper was obtained.
Mission reliability allocation of spaceflight TT&C system based on RBFNN adaptive hybrid learning algorithm
ZHANG Xin-gui, WU Xiao-yue
2012, 27(8): 1758-1764.
Abstract PDF(622KB) icon1740 icon589
Abstract:
Due to the existence of a complex spatial and temporal correlation,visualization and information related dynamic constraints to each equipment when they executed TT&C(telemetry tracking & commanding) mission,it was extremely difficult to model and analyze,and the solving efficiency was low.Therefore a radial basis function neural network (RBFNN) modeling method with adaptive hybrid learning(AHL) algorithm was proposed.Principal component analysis were used to determine the initial number of hidden units.Intelligence optimization algorithm combined with decaying gradient descent information was used to train parameters of RBFNN which were improved to accelerate convergence and guarantee the result to converge at the global optimum with high probability.The algorithm was employed in the offline training of model parameters by sampling the input/output data of the system,and the realization details were also provided.By simulation,it shows that the AHL has higher generalization power and can reach more optimal results in solving the mission reliability allocation of spaceflight TT&C system.
Statistical energy analysis method applied to high frequency load identification of structures
XIE Qiong, XIE Shi-lin, ZHANG Xi-nong
2012, 27(8): 1765-1772.
Abstract PDF(1612KB) icon1652 icon639
Abstract:
Application of statistical energy analysis method to high frequency load identification of structures was proposed.The approach and procedure of the input power identification of subsystems were presented for the structures subjected to multi-excitations.The simulation study using AutoSEA2 software and experimental study on high frequency load identification were respectively conducted for a plate-shell assembled structural system.Both the simulated results and experimental results show that the input power of excited subsystems can be identified accurately in the cases of single excitation and multi-excitations employing the presented identification method.The work presented provides a theoretical reference for high frequency load identification of engineering structures.
Method of flight performance prediction of high bypass ratio turbofan engine based on ground test data
TU Qiu-ye, SHI Yang, QIU Chao, HUANG Qiu-yuan, TANG Hong-yu
2012, 27(8): 1773-1777.
Abstract PDF(416KB) icon1763 icon571
Abstract:
In order to predict the flight performance of a high bypass ratio turbofan engine. Errors of component efficiencies and pressure losses of a high bypass ratio turbofan engine at ground test point and design point were estimated by using GasTurb 11 software. And then the relationships of the errors between design point and ground test point were determined through the non-design point sensitivity analysis method. In terms of the above relationships determined, the flight performance of the high bypass ratio turbofan engine can be predicted at last. Prediction of the flight performance of a high bypass ratio engine shows that the method is feasible, analysis of ground test data, relationships of delta value of ground point and design point and the non-design point sensitivity analysis are three key links in predicting the flight performance of high bypass ratio turbofan engines.
Flight test of mass flow measurement of turbofan engine
ZHAO Hai-gang, SHEN Shi-cai, ZHANG Xiao-fei, MA Yan-rong, WANG Xiao-feng
2012, 27(8): 1778-1784.
Abstract PDF(1593KB) icon1937 icon565
Abstract:
Based on the flight test of the turbo-fan engine,the system of mass flow measurement of the engine was designed and built,and mass flow of the turbo-fan engine was measured in the flight test under some different flight conditions and engine conditions.The test data was selected,calculated and analyzed,and then,the effect of every factor on mass flow of the engine was evaluted.The technique feasibility and result accuracy was validated and some usable conclusions of the mass flow measurement and analysis for the engine mass flow measurement designed were obtained.All of these provided foundation for the mass flow measurement and analysis of the subsequent models.Numerical simulation model for the engine mass flow was established and modified using flight test data.By comparing some results of numerical simulation with flight test data,it is found that the numerical results are in agreement with flight test data and the error is acceptable.
Aero engine component characteristic map correction using multi state test data
YANG Xin-yi, SHEN Wei, WANG Wen, WANG Yong-hua, WANG Xing-bo
2012, 27(8): 1785-1791.
Abstract PDF(1069KB) icon1717 icon525
Abstract:
In order to improve the accuracy of engine component characteristic map correction with modification factors method,a new correction method using multi state engine test data was presented.Equations from the engine model based on component matching and the difference equations of calculated and test parameters were used as objective equations.In addition,the objective function was optimized using an improved immune particle swarm optimization algorithm.Thus the engine component correction coefficients were obtained.Based on these coefficients of different states,a correction coefficient surface was fitted by moving least square method,and the corrected component map was obtained with the obtained coefficient surface.Simulated results show that because of the use of multi state test data,the proposed new method shows better performance than the traditonal one.The corrected component map has higher accuracy in the whole scope.
Investigation on unsteady characteristics of unstarted two-dimensional inlet flow using hybrid LES/RANS method
CHEN Ti, LIU Wei-dong, FAN Xiao-qiang
2012, 27(8): 1792-1800.
Abstract PDF(2230KB) icon1853 icon513
Abstract:
A hybrid large-eddy simulation/Reynolds-averaged Navier-Stokes(LES/RANS) method together with 5th order WENO(weighted essentially non-oscillatory) scheme were used to caculate an unstarted two-dimensional inlet with contraction ratio of 1.5 in a Mach 3 freestream.The unsteady flow field in the unstarted inlet was captured.The result shows that current numerical method can predict mean adiabatic wall temperature,friction velocity and Reynolds stress reasonably well.Some low-frequency motion exist in the shock system and separation zone in the unstarted field at large time-space scale.The dominant frequency is close to its counterpart in classic shock/turbulent boundary layer interaction problem.The inlet switches to started state intermittently.
Model of open rotor engine for aircraft conceptual design
ZHANG Shuai, YU Xiong-qing
2012, 27(8): 1801-1808.
Abstract PDF(566KB) icon1800 icon561
Abstract:
A rapid analysis model of the open rotor engine,which can be used in aircraft conceptual design,was established by the combination of the test data of high speed propfan and approximate model of turboshaft.The performance,mass and size of the open rotor engine were able to be predicted quickly by this model with a small amount of input parameters.The precision of the model was validated by the experimental data from the references.The model developed in the paper can be used in the aircraft conceptual design to evaluate the benefits of using open rotor engines.
Study on thermodynamic cycle parameter matching for intercooled recuperated aero-engine
GONG Hao, WANG Zhan-xue, LIU Zeng-wen
2012, 27(8): 1809-1814.
Abstract PDF(1195KB) icon2412 icon575
Abstract:
The intercooled and recuperated processes were incorporated into the conventional high bypass turbofan engine thermodynamic cycle.Consequently,the intercooled recuperated aero-engine (IRA) simulation model was built and an overall performance simulation program was developed.Then,analysis on choosing and matching the thermodynamic cycle parameters of IRA was conducted.The result indicates that there are some thermodynamic cycle parameters such as intercooler effectiveness,recuperator effectiveness,bypass intercooling split,pressure ratio assignment between booster and high pressure compressor,overall pressure ratio and bypass ratio,which have significant influence on IRA performance.The turbofan engine performance can be improved with the proper use of intercooling, recuperation and the optimized matching of the thermodynamic cycle parameters.
Research on three-dimensional design of bowed and swept blade of transonic fan
JIANG Bin, ZHENG Qun, WANG Song-tao, FENG Guo-tai
2012, 27(8): 1815-1825.
Abstract PDF(2118KB) icon1744 icon547
Abstract:
Effects of bowed and swept blade on the improvement of transonic fan performance and inhibition of the flow loss were studied by numerical simulation based on a small transonic axial fan.The swept and bowed design concept for the up half spanwise of rotor and later half spanwise of stator was discussed at the design flow condition and the less flow condition.The results show that negative bowed design for up half spanwise of rotor changes the pressure gradient near the endwall ,thus ,the accumulation of boundary layer near the side of pressure surface at outlet caused by the leakage flow is decreased,and the flow capacity is enhanced.The negative bowed design at leading edge and positive bowed design at trailing edge were adopted in the design of stator.The complex bowed and twisted technology can realize the increase of flow rate near the endwall and the control of the secondary flow at the same time.The bowed and twisted stator can also control the deterioration of secondary flow better with the decrease of flow rate and enlarge the range of steady operation condition obviously.
Three-dimensional aerodynamic optimization of intermediate stator of 7-stage axial compressor
LIU Xiao-jia, NING Fang-fei
2012, 27(8): 1826-1831.
Abstract PDF(909KB) icon1640 icon552
Abstract:
To solve the conflict between stage-matching and computational cost during the 3-D(three-dimensional) aerodynamic optimization of multi-stage axial compressor,an optimization strategy was proposed,in which the stage to be optimized was simulated instead of the whole multi-stage compressor,while the stage environment was taken into account in the boundary conditions.The 4th stator with suction separation of a highly loaded 7-stage axial compressor has been optimized.Within the limited time,the adiabatic efficiency was improved about 0.8%,the total pressure ratio was improved about 4%,and the overall performance of the compressor was improved effectively.It is proved that the stage-matching and computational cost aer well balanced by this optimization strategy.
Effect of axial turbine element stage stator solidity on rotor-stator interaction
YANG Jie, QIAO Wei-yang, SHI Pei-jie, WANG Pu-wei
2012, 27(8): 1832-1840.
Abstract PDF(1910KB) icon1678 icon502
Abstract:
A numerical simulation on the unsteady flow of turbine element stages with different stator solidity was conducted to investigate the stator solidity influence on the turbine element stage rotor unsteady potential interference,stator wake interference with rotor and the element stage performance unsteadiness and to explore the stator solidity influence mechanism on rotor-stator interaction.The research results show that the rotor unsteady potential interference in upstream stator passages becomes stronger as stator solidity increases,but damps faster and influences more narrowly;the stator solidity change causes the change of wake interference intensity by altering the wake intensity,wake interference frequency and the flow status in rotor passages;then the element stage performance unsteadiness is altered by the change of wake interference intensity.
Numerical investigation of effect of forward sweep on tip clearance flows in highly loaded fan rotor
WANG Lei, LIU Bo, ZHAO Peng-chen
2012, 27(8): 1841-1847.
Abstract PDF(1365KB) icon1836 icon534
Abstract:
A modern highly-loaded forward swept transonic fan rotor flow field was investigated numerically at multiple rotor tip clearance levels to obtain clearance sensitivities with respect to flow,efficiency and stall margin.Compared with a conventional radial leading edge profile that had aerodynamic equivalent manner,the forward swept rotor blades show significant reduction in clearance sensitivity.The benefits are more pronounced for the configuration with stronger tip clearance flows.No optimum clearance size for the present forward swept rotor is indicated.Detailed comparisons of tip clearance flow structures were used to explain the flow mechanisms responsible for the reduction in tip sensitivity and blockage with forward sweep.
PIV measurement of flow field for tip clearance flow in turbine shroud
YU Lei, CHANG Hai-ping, MA Hu-yue
2012, 27(8): 1848-1854.
Abstract PDF(2446KB) icon1672 icon507
Abstract:
In order to study flow characteristics of tip clearance flow in turbine shroud,a cooling experimental system was designed,and the instantaneous flow field of each typical section was received by particle image velocimetry(PIV).Then the flow field characteristics of tip clearance flow were studied.The result shows:two cooling flows of the turbine shroud cavity mixing with tip leakage flow makes the flow state in shroud cavity very complex.Therefore,vortex flows with different functions and sizes are generated at different positions in shroud cavity.Meanwhile,both the two cooling airflows have blocking effect on the leakage flow,and the effect from the former hole is more obvious.
Design method for improving aerodynamic damping of compressor blades
GUO Xue-lian, LI Lin
2012, 27(8): 1855-1860.
Abstract PDF(869KB) icon1769 icon546
Abstract:
Considering the situation of the application of aerodynamic damping in the forced response,an aero-damping design method based on basic blade profile was proposed.It was revealed that a slight adjustment to the blade-stacking axis of blade can change the aero-damping,meanwhile,the effect on the fluid filed can be confined to the minimum.The relationship between the adjustment and the aero-damping was established.Owing to such a relationship,a large quantity of fluid calculations could be avoided and an improveing of the aero-damping by adjusting the stacking axis can be obtained.In this way,the shape similarity was used to connect the mode shape and aerodynamic damping.The smaller the similarity,the bigger the aero-dynamic.
Interface stress analysis of solid motor grain structure
ZHENG Xiao-ya, LIU Qing, WANG Wei-xiang
2012, 27(8): 1861-1866.
Abstract PDF(775KB) icon1515 icon558
Abstract:
The numerical method based on thermal viscoelastic contact theory was studied.It provided a convenient method to judge whether interface debond occured or not.A solid motor grain structure was taken as an example,and contact arithmetic was applied to simulate multilayer complicated boundary of solid motor grain structure.Strain field was computed under flight condition,and distribution rule of interface stress between case and insulation was researched.Results show that strain field contour agrees with the fact.Interface between case and insulation is ideal and is unable to debond.
Visible/near infrared radiation characteristics of attitude-control engine exhaust plume
KE Wei-na, ZHU Ding-qiang, CAI Guo-biao
2012, 27(8): 1867-1873.
Abstract PDF(943KB) icon1597 icon534
Abstract:
In order to study the plume radiation effects on optical detecting and imaging,based on the scatted theories of different diameter particles,the radiation transition equation and the database of molecular absorption lines,a program using the finite volume methods was developed to simulate the plume radiation characteristics in variable wave bands.Modeling the actual working conditions,the visible and near infrared radiation characteristics of attitude control engine plume working in lunar orbit was computed.In 0.4~0.9μm,the effects of composite gas component,the wavelength,the detected zenith and the solar incidence on the plume radiation were simulated and analyzed.The result shows that the program based on finite volume methods can simulate the plume radiation characteristic accurately and be applied diffusely;solar radiation is the greatest influential factor of plume radiation in the visible and near infrared wave band.
Analysis of infrared radiation of hybrid rocket motor exhaust plume
SHEN Wen-tao, DONG Chao, ZHU Ding-qiang, CAI Guo-biao
2012, 27(8): 1874-1880.
Abstract PDF(1049KB) icon1736 icon530
Abstract:
Infrared properties of hybrid rocket engine plume were studied by establishing a theoretical model of infrared radiation in 2~12μm wavelength.The pressure,temperature and concentration of each component of flow field were considered as the input parameters.The spectral radiation parameters of the particle were calculated by the Mie scattering model.The thermal radioactive transfer equation was discredited by using the finite volume method(FVM).Finally,the moderate resolution atmospheric transmission (MODTRAN) model was used to calculate the infrared radiation attenuation in the atmosphere.The results indicate that the transmission conditions,height,angle and particle size exert important effect on the distribution of spectrum radiance.The results contribute to providing reference for further research of target tracking and hybrid rocket motors design.
Simulation and analysis of wall heat fluxes for shear coaxial GH2/GO2 single element combustor
JIANG Jin-peng, LI Mao, JIN Ping, CAI Guo-biao
2012, 27(8): 1881-1886.
Abstract PDF(1031KB) icon1748 icon517
Abstract:
With gas hydrogen/gas oxygen being propellant,adopting numerical simulation,design parameters of shear coaxial injector,namely ratio of fuel velocity to oxidizer velocity and the ratio of oxidizer pressure drop to combustor pressure have been studied to find their impact on combustion characteristics and thermal loading of chamber wall.The simulation results of two kinds of wall boundary condition which were adiabat condition and isothermal condition were compared with experimental result.It shows that the increasing of the ratio of fuel velocity to oxidizer velocity improves the combustion performance and wall heat flux.The increasing of the ratio of oxidizer pressure drop to combustor pressure decreases the combustion performance and wall heat flux.In comparison with wall gas temperature,wall heat flux is more consistent with the real condition when used to predict thermal loading of combustion chamber wall.
Dynamic response of co-rotating and counter-rotating dual-rotor system supported on ball bearing
LUO Gui-huo, ZHOU Hai-lun, WANG Fei, YANG Xi-guan
2012, 27(8): 1887-1894.
Abstract PDF(1628KB) icon2086 icon520
Abstract:
The dual rotor-ball bearing-stator coupling dynamic model was established for the aero-engine with dual rotor as to research object.The model concerned the coupling effect of inter-rotor bearing between the low pressure rotor and high pressure rotor,between the outer race of ball bearing and bearing housing,and between the flexible support and squeeze film damper.In the model of ball bearings,the clearance of bearing,nonlinear Hertzian contract force between balls and races and the varying compliance vibration were considered.The beat vibration response and whirl orbit of co-rotating or counter-rotating dual-rotor system were analyzed by using the model.The results show that the beat vibration response occurs obviously when two rotors operate at approximate speed,the whirl orbit of the counter-rotating dual-rotor system will be the petal shape.Finally,the results of numerical integral and the model were validated with the experiments of the dual rotor rig.
Low sensitivity modification for spiral bevel gears
SU Jin-zhan, FANG Zong-de
2012, 27(8): 1895-1901.
Abstract PDF(1022KB) icon1816 icon540
Abstract:
The methodology of low sensitivity modification was proposed for improving the meshing stability of spiral bevel gears used in aerospace application.Based on tooth surface error and error sensitivity matrix,the model of tooth surface error modified can be developed,the generalized inverse matrix with least square method was adopted to solve the transcendental equations,and the correction quantities can be obtained.Tooth surface modification with three segments parabolic was conducted,and the tooth surface correction model and the relative solutions were applied to obtain correspondingly machine-tool settings adjustment quantities by considering the modified tooth surface as the objective surface.A numerical example presents that the error sensitivity of the contact patterns and the misalignment tolerances can be enhanced by the low sensitivity modification with the root bending strength descending to 4.28%.Therefore,the change of tooth root strength can be fall down and the meshing stability can improved by the properly determination of tooth modification coefficients.
Analysis of front plate's effect on low hysteresis brush seal
CHI Jia-dong, WANG Zhi-li
2012, 27(8): 1902-1906.
Abstract PDF(675KB) icon1637 icon529
Abstract:
Aimed at different kinds of low hysteresis brush seals,computed them with porous medium model,and analyzed the pressure and velocity on upstream side of bristles,turbulence kinetic energy at the front and low part of bristles,discussed the effect of front plate on low hysteresis brush seals.The result indicates that front plate does not have obvious effect on upstream bristles' pressure,axial velocity and leakage of brush seals,but varies radial velocity on upstream bristles behind different kinds of front plate;the turbulence kinetic energy at the upstream and low part of bristles of the brush seal without front plant or with front plate too long is very big,the brush seal has front plate with holes got smaller turbulence kinetic energy at the upstream and low part of bristles than the other kinds of brush seal,and gets smaller bristle disturbance effect.
Improved clutch engagement control method for unmanned helicopter
ZHOU Yao-ming, ZHANG Lei, HE Wei, WU Zhe
2012, 27(8): 1907-1913.
Abstract PDF(663KB) icon1529 icon545
Abstract:
In light of the former method's shortcoming,a new method was explored to improve clutch engagement quality.The clutch control requirements were determined based on the dynamics characteristic research of an unmanned helicopter clutch and the analysis of the effect of clutch engagement process on transmission impact and belt life.The rotating speed of clutch driving pulley and driven pulley were selected as basic input parameters.Ideal rotating speed curves were proposed.Three stages of engagement process adopted open-loop control,closed-loop control and open-loop control in turn.To realize the smooth and quick engagement,the closed-loop control adopted the combination of proportion integration differentiation(PID) control and fuzzy control.The experiments were conducted by using former control method and improved control method respectively.The results show that,as compared with former control method,the engagement time of improved control method shortens 1.5 times, the maximum jerk decreases 3 times,and the sliding friction work decreases twice. These prove that the improved control method can improve clutch engagement quality.
A new method for designing optimal control law of aeroengine in transient states
LU Jun, GUO Ying-qing, WANG Lei
2012, 27(8): 1914-1920.
Abstract PDF(1637KB) icon2399 icon591
Abstract:
A new method——fixed dynamic method(FDM),which delt with the issue of designing optimal control law of aeroengine in transient states,was proposed.Firstly,based on a detailed non-linear aerothermodynamic model,it made the errors of nonlinear equations set to zero via extracting all of state variable rates and let the model reach steady-state,which meant the parameters in this state were equal to that in transient state;secondly,according to the given limited conditions respectively,the control laws can be built directly via simple static programming method;finally,merged all of them via Max/Min selection and obtained the optimal control law.The computing results of the improved acceleration control law of some turbofan engine indicate that the FDM is accurate and effective.

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