2009 Vol. 24, No. 8

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Test of the characteristics of axial flow compressor with splitter
JIN Hong-jiang, YE Zhi-feng, GONG Ji-peng
2009, 24(8): 813-1817.
Abstract PDF(639KB) icon1756 icon538
Abstract:
Technologies of axial flow compressor with splitter and present status of researches on these technologies were introduced.The process of applying splitter blade to the turboshaft engine was explained.Based on component test and engine test on the engine test bed, the efficiency and the improvement of aeroengine performance installed with axial flow compressor with splitter were analyzed.The test result shows that the flow increases by 7.27%, the power increases by 20.79% and the specific fuel consumption(SFC) decreases by 2.67%.The technologies have broad prospects for application on aeroengine.
Research on residual life prediction of turbine blade-disc under radon environment
YANG Zi-chun, SHEN Wen-cai, PENG Mao-lin
2009, 24(8): 1677-1683.
Abstract PDF(2139KB) icon1727 icon493
Abstract:
Heat-fluid-solid coupling and contact thermo-elastic-plastic analysis was carried for a certain turbine blade-disc, and the stress and strain-time course was obtained in this paper.Based on probabilistic Miner's rule and strain field intensity(SFI)approach, the fatigue/creep life of turbine blade-disc was calculated by using K.N.Smith equation and Manson-Succop creep equation.Influential factors to the fatigue and creep were analyzed according to the life prediction results and some advices about utilization and maintenance of the equipment were given.Results in this paper were close to factual state, proving that the method of residual life prediction for the turbine blade-disc is preferably so far.
Generalized method of cell with weak interfacial bonding
GAO Xi-guang, SUN Zhi-gang, LIAN Ying-qi, SONG Ying-dong, ZHU Ru-peng
2009, 24(8): 1684-1690.
Abstract PDF(767KB) icon1691 icon472
Abstract:
A generalized method of cell(GMC) with weak interface was developed to model the interface debonding within continuum fiber reinforced composite.To accomplish this work, the average displacement continuum condition between sub-cells in original GMC was modified by employing weak interface theory.Then the average strain of subcell was expressed in terms of global strain.By using the local constitutive equation, the relationship between average stress of subcell and the global strain was established.At last, the evolving compliant interface model was employed by GMC to model the global response of fiber reinforced composite under transverse loading.The result shows that the methodology developed here is appropriate to model the interface debonding.
A rafting model for creep of Ni base single crystal at high temperature based on microstructure cell
CAO Juan, WANG Yan-rong, SHI Duo-qi
2009, 24(8): 1691-1698.
Abstract PDF(921KB) icon1612 icon451
Abstract:
A rafting model for creep of Ni base single crystal based on microstructure cell was introduced into the dislocation slip model, and the rafting behaviors during creep of DD3 at 1 223 K and SRR99 at 1 123 K and 1 253 K were described in combination with the cell's analytic stress model.By incorporating the changes of the cell's dimensions into the cell stress model, the criterion of rafting type and direction judgment was determined and the rafting deformation was simulated quantitatively.Both the results of rafting direction judgment and the simulation of rafting process were in agreement with experiments.With the introduction of rafting model, the dislocation slip model could simulate the creep behavior of single crystal at high temperature more accurately.
Structure analysis and life evaluation of the pin holes in a turbine disc of a type of aero-engine
LI Wei, DONG Li-wei, CAI Xiang-hui, ZHAO Fu-xing, LIU Dong
2009, 24(8): 1699-1706.
Abstract PDF(977KB) icon1741 icon491
Abstract:
The stress and strain distribution at the radial pin holes in a turbine disc of an aero-engine was analyzed using finite element analysis(FEA) method.The influence of some factors on the stress distribution adjacent the pin hole was discussed, such as the numbers of the pins, the friction coefficient between hole and pin, the presentation of torque on the disc.The analysis revealed the difference between earlier test and actual operation.The fatigue life was estimated with the formula of strain energy and the predicting life tallied well with the test.The results demonstrate that turbine disk fatigue test with torque is necessary, providing a mechanical foundation for the life extension of the high pressure turbine discs.
Identification of rotor-rubbing malfunctions in aero-engines
CHEN Wei, DU Fa-rong, LI Yun-qing
2009, 24(8): 1706-1713.
Abstract PDF(1277KB) icon1401 icon563
Abstract:
Based on the characteristics that energy fluctuation occurs during resonant vibration transfer in elastic medium, a kind of method was developed to identify the state of rubbing between rotor and engine-frame by using the evidence of energy distribution and its movement.The rubbing was identified by processing vibration signals using fast Fourier transform(FFT), understanding color maps by point of energy, and also combining time-domain charts, frequency charts and waterfall maps.Through experiments, it's proved that the method is applicable and also provides actual evidence in engineering application.
Vibration analysis of rarefaction wave launch device in moving mass
WANG Ying-ze, ZHANG Xiao-bing
2009, 24(8): 1714-1719.
Abstract PDF(729KB) icon1221 icon496
Abstract:
The vibration response of the rarefaction wave launch device was studied.Based on the launch mechanism and structure characteristic of the rarefaction wave launch device, the vibration equations of launch device were established in consideration of the actual movement of the projectile and inertial breech.In these vibration equations, the projectile and inertial breech were equivalent to the moving masses, and the coupling effects between elastic vibration of the launch device and rigid movement of the moving masses were also considered.With modal superposition method, the vibration equations were dispersed to the second-order time-variant equations.After numerical calculation, the vibration response and muzzle dynamic effects were acquired.From these results, some theory references for fire precision and airframe integration design were provided.
Application of fractional Fourier transform in one turbine-shaft engine surge analyse
KUANG Gui-lan, WANG Dao-bon, WU Wei-li, YUE Li, YAO Zheng-rong
2009, 24(8): 1720-1725.
Abstract PDF(779KB) icon1652 icon438
Abstract:
The article constructed signal to simulate the fractional Fourier transform(FRFT)'s characteristics of time-frequency analysis and validated that FRFT can relieve time and frequency coupling effectively.Then, typical surge experiment data of a turbine-shaft engine were processed using FRFT in order to pick up surge characteristic signal.With the FRFT energy spectrum of the surge characteristic signal, we evaluated the instantaneous surge frequency.The results show that using the characteristics of FRFT's energy congregation in the rotary angle, which matches with the engine surge's peculiarity, helps pick up the engine's surge characteristics signal effectively;using the FRFT energy spectrum helps estimate the instantaneous surge frequency.
Experimental study on adaptivity of oxidation kinetics equations in APS thermal barrier coatings
LI Zhi-yong, ZHANG Jian-yu, BAO Rui, HU Hao-ju, FEI Bin-jun
2009, 24(8): 1726-1730.
Abstract PDF(1267KB) icon1504 icon488
Abstract:
The experiment method was adopted to study the oxidation kinetics of air plasma sprayed(APS) thermal barrier coatings(TBCs) in four different temperatures, and the state parameters were given by matching the experimental data with these two popular oxidation kinetics formulas.The investigation shows that the kinetic curves are the same in the form under four different temperatures, and the oxidation kinetics of APS TBCs can be expressed properly by the parabolic function formula only under higher temperatures, but the power function formula is powerful for the expression of oxidation kinetics, and it can express the oxidation kinetics perfectly in all the four temperatures.
Effects on transmission parameters of vibration measurement for high temperature environment
MEN Xiu-hua, LI Shun-ming, HU Rui, BAO Qing-yong
2009, 24(8): 1731-1735.
Abstract PDF(511KB) icon1487 icon417
Abstract:
Temperature rise leads to signal transmission change of vibration measurement during test run of engines.Based on electromagnetic-thermal theory, the effects of thermal field on electromagnetic field variables were studied.A new approach was proposed to extract multi-conductor transmission parameters by combining test transmission network.The parameters values obtained by proposed approach were in good agreement with classical energy method.The results show that resistance and inductance of transmission conductor increase with the rising temperature, and conductor resistance has obvious change range compared to inductance.Proximate effects of conductors aggravate along with temperature rise, and mutual electrical parameters have important changes due to temperature and distance.
Research into the restoration method for high-altitude piston engine
XU Bin, LIANG Zheng-yue
2009, 24(8): 1736-1740.
Abstract PDF(1237KB) icon1589 icon446
Abstract:
The power development of a new generation of unmanned aerial vehicle(UAV) was analyzed.According to the performance characteristic of small UAV powered by the piston devices, a method matching small UAV's two-stage supercharging system was designed for realization at high altitude.A preliminary analysis on the high-altitude performance of engine was conducted to verify the feasibility of the programme, providing a design basis for high-altitude UAV.
Compressor characteristics generation method using moving least square
YANG Xin-yi, SHEN Wei, LIU Hai-feng, DONG Ke-hai
2009, 24(8): 1741-1746.
Abstract PDF(1749KB) icon1926 icon433
Abstract:
Compressor characteristics maps need to be interpolated and dispersed during gas turbine engine performance simulation.Meanwhile the maps usually need to be extrapolated as the characteristics data of low rotational speed are absent.An improved method of using dimensional surface to illustrate compressor characteristics instead of rotational speed lines was proposed.Characteristics data were calculated from start-up test results of a small gas turbine engine.Based on these data and the known characteristics data from the original map, a characteristic curve was generated using moving least square(MLS).The generated curve covers all the operational range and has a high degree of accuracy.It is very suitable for performance simulation as it need no interpolation.
Test investigation of areo-engine's stability enhancement components in anti-surge system
YE Wei, QIAO Wei-yang, HOU Min-jie
2009, 24(8): 1747-1751.
Abstract PDF(526KB) icon1628 icon427
Abstract:
To assess and optimize the optimal efficiency of the anti-surge system, this paper adopted the temperature distortion generator as the force-surge system and presented the test results of certain turbojet and turbofan engine's stability enhancement components at different combinatorial projects respectively, compared and discussed the effects of various stability enhancement components of the anti-surge system.The test results show that the most effective anti-surge system is the one using throttle cutting for a short time, vane regulating and air bleed and so on.The defect is the biggish thrust drop and system complexity.The stability enhancement effect of cutting off and regulating vane at the same time is not as good as the preceding one, but with lesser thrust drop and better realizability.
Numerical simulation of two dimension iced airfoil using immersed boundary method
ZHONG Guo-hua, SUN Xiao-feng
2009, 24(8): 1752-1758.
Abstract PDF(1953KB) icon1811 icon467
Abstract:
An immersed boundary method was applied to numerical simulation of the flow past a clean/iced NACA0012 airfoil.In this paper, two dimension imcompressible Reynolds-averaged Navier-Stokes equations were solved with SIMPLEC method.One equation turbulence model——Spalart-Allmaras turbulence model, was used in the numerical procedure.Good agreement was found between the present numerical results and previous experimental work.
Experimental research on active control of separation flow over airfoil
HAO Li-shu, QIAO Zhi-de, SONG Wen-ping
2009, 24(8): 1759-1765.
Abstract PDF(2079KB) icon1715 icon448
Abstract:
In order to carry out the experimental research on active control of separated flow over airfoils, two forms of synthetic jet actuators based on piezoelectric vibration diaphragm were designed.The hot wire anemometer measurements were performed on synthetic jets with rectangular orifice in quiescent environment.The results indicate that the vertical synthetic jets can obtain a maximum speed of 21.32 m/s.The airfoil separation active control experiment based on synthetic jet technology was performed in two-dimensional testing section of NF-3 wind tunnel, the inclined synthetic jets in the airfoil experiment can obtain 10 m/s order magnitude speed, postpone the airfoil surface flow separation and improve the airfoil stall's characteristic.When the synthetic jet actuator is working, airfoil maximum lift coefficient can increase by 11.36% and the angle of attack stall can increase by 3°.At the same time, it's observed that the effect of active control on flow separation is effective when momentum coefficient reaches the order of magnitude of 10-3, and there will be no effect if the momentum coefficient is less than the order of magnitude of 10-4.
Numerical simulation method for the powered effects in airframe/propulsion integration analysis
TAN Zhao-guang, CHEN Ying-chun, LI Jie, ZH ANG Miao
2009, 24(8): 1766-1772.
Abstract PDF(1095KB) icon1957 icon517
Abstract:
The flow-fields around powered isolated turbofan engine model and powered DLR-F6 wing/body/pylon/nacelle(WBPN) model were numerically simulated and analyzed by the appropriate fan inlet face and jet-exit boundary conditions.Three-dimensional time-dependent compressible Reynolds-averaged Navier-Stokes equations were solved with third-order upwind-biased flux-difference splitting method and approximate factorization method.The point-to-point patched multi-block technology was used to generate high quality grid.The multi-grid technique was employed to accelerate the convergence.For a better simulation of the powered effects, the fan inlet face boundary conditions and jet-exit boundary conditions were determined.Computational results and comparisons with experimental data were presented.The good agreement indicates that the numerical method, grid blocking strategy and management of boundary conditions are validated.
Two-dimensional incompressible model of effects of rotating inlet distortion on flow instability in compression systems
ZHANG Huan, HU Jun, LIU Da-xiang, TU Bao-feng, WANG Zhi-qiang
2009, 24(8): 1773-1784.
Abstract PDF(2617KB) icon2168 icon455
Abstract:
Based on Moore-Greitzer model, a two-dimensional incompressible model was developed to predict the post stall transient and effects of nonuniform inlet flow on flow stability of compression systems, and calculations were presented in detail to predict the post stall transient behavior and the onset of flow instabilities in axial compression systems with rotating inlet total pressure distortion.It's found that both the inlet distortion amplitude and rotating frequency have a strong effect on the stability and post stall transient behavior, and the rotating frequency has the same strong influence on the onset of surge as the influence on the onset of rotating stall.But the resonant response frequency strongly depends on the frequency at which the stall cell rotates.
Numerical simulation of effects of the inlet pipe on the performance of a centrifugal compressor
ZHANG Jun, MA Hong-wei, HE Hong, JI Jian-bo
2009, 24(8): 1785-1791.
Abstract PDF(1433KB) icon1601 icon439
Abstract:
Steady-state simulation including the impeller, vaneless diffuser and volute with different configurations of inlet pipe was carried out to investigate the effects of inlet pipe on the compressor performance.The results show that the uncorrelated performance curve varies obviously with different inlet pipes.When the inlet pipe is longer in length or smaller in diameter, the pressure ratio and choked mass flow of the compressor become smaller.It is because the existence of inlet pipe changes the incidence angle at the impeller inlet which determines the performance of the compressor.If compared by correlated performance, the influence of the inlet pipe is relatively smaller.However, the correlated choked mass flow is still smaller when the inlet pipe is longer in length or smaller in diameter.
Numerical simulation of the effect of total pressure inlet distortion on a compressor rotor
CHEN Mei-ning, PIAO Ying, WANG Da-lei
2009, 24(8): 1792-1798.
Abstract PDF(996KB) icon2006 icon467
Abstract:
Steady numerical simulation of the flow field of the Rotor37 with total pressure distortion inlet was conducted by resolving three dimensional Navier-Stokes functions in this paper.Three different low total pressure inlet conditions were considered: one distortion per revolution(1×120°), two distortions per revolution(2×60°) and four distortions per revolution(4×30°).The characteristics of the rotor with total pressure distortion were achieved.Influences of different frequencies of distortion were considered.The flow field of the rotor was analyzed in detail, and some preliminary conclusions were made: circumferential pressure distortion causes non-uniformity of other inlet parameters.The inlet total pressure induces total temperature distortion at the outlet.Massflow and efficiency decrease, and stall margin increases as the frequencies of distortion increase with the total spoiled sector of 120 degrees.Stability total pressure ratio depends only on the angle of the distorted sector and the loss of the stability total pressure ratio increases with the growing angle of the distorted sector.
Effects of non-axisymmetric IGV wakes on a low speed axial compressor
LIU Jian-yong, LI Zhi-ping, LU Ya-jun, ZENG Tao
2009, 24(8): 1799-1804.
Abstract PDF(906KB) icon1563 icon466
Abstract:
Based on the axisymmetric wake impact experiment, several non-axisymmetric wake impact experiments were carried out.When the number and circumferential positions of inlet guide vanes(IGV) were logical, the wakes of non-axisymmetric IGVs could make beneficial unsteady excitation on downstream rotor field.In these experiments, some suitable non-axisymmetric wake impact plans worked better than the axisymmetric wake impact plan.As compared to the axisymmetric wake impact plan, the non-axisymmetric wake impact plan could supply multi-frequency exciting signals.In addition to the beneficial high-frequency signal, the non-axisymmetric plan B generated a low-frequency square-wave exciting signal and some beneficial secondary signals.Based on the unsteady cooperative flow theory, the exciting wakes in non-axisymmetric plan were easier to cooperate with complicated vortices in a compressor, such as clearance vortices, passage vortices and separated vortices.The non-axisymmetric wake impact plan B in this paper could make the max efficiency increase by 1.2%, total pressure rise and stall margin rise by a little.
Design of a high-loading two-stage forward swept fan and investigation on the swept-blading mechanism
YANG Jing-jing, SHAN Peng
2009, 24(8): 1805-1812.
Abstract PDF(1451KB) icon1755 icon549
Abstract:
The design method and the result of a two-stage high-loading forward-swept fan were presented.The design strategies of both rotor tip and stator hub forward-swepts were applied to improve the stage efficiency and stall margin.With this design, 3-D steady viscous computational fluid dynamics(CFD) technique was used to discuss the influences of forward and backward-swept rotors on the first-stage fan performance and their reasons.Two facts are found.Firstly, the swept forward and backward blade passages cause almost the same stage-efficiencies, and there exist no contrarily rotated swirling phenomena in the 3-D relative velocity fields.Secondly, the reason why the forward-swept blade can significantly increase the stall margin is that the rotor's passage shock wave tends to develop from near hub to tip according to its own intrinsic rule of developing spanwise.Both the spanwise structure and the streamwise location of the curved passage shock don't vary thoroughly with the forward or backward of the blade leading edge.So the relative distance between the shock and the leading edge increases.
Turbulence modulations caused by change of particle size and particle mass loading ratio
WANG Bing, LIU Yi, WANG Xi-lin
2009, 24(8): 1818-1823.
Abstract PDF(978KB) icon1452 icon443
Abstract:
The velocity fields in particle-laden two-phase round turbulent jets were measured by means of phase Doppler particle analyzer(PDPA).The turbulence modulations caused by the change of particle size and particle mass loading ratio were studied under the condition of small particle Reynolds number.The measured results of turbulence intensities show that particles have more pronounced effects on the attenuation of the gas-phase turbulence, if the particle diameter reduces, or the particle mass loading ratio increases.The dimensionless analysis shows that the attenuation of turbulence intensity introduced by decreasing the particle size is higher than that by increasing the particle mass loading ratio.
Investigation on liquid/solid phase change heat transfer of aircraft icing
DU Yan-xia, GUI Ye-wei, XIAO Chun-hua, YI Xian, LI Jun
2009, 24(8): 1824-1830.
Abstract PDF(955KB) icon1774 icon502
Abstract:
The liquid/solid phase change heat transfer characteristics of aircraft icing were investigated based on the theories of liquid-solid phase change.The analysis model for the growth of film and ice was established and the influence of airflow parameters on the characteristics and rate of icing accretion was analyzed.The results indicate that the accretion rate of icing is not only influenced by the airflow parameters but also influenced by the inner heat transfer of each phase.The heat transfer in solid and liquid phase shall be taken into account as an important method to improve the precision of icing prediction.The current model predicts the ice growth rates and ice type relatively well in consideration of the nonlinear characteristics of liquid/solid phase change.
Application of preconditioned AUSM+ scheme on numerical simulation of reacting flows at all speeds
LIU Chen, WANG Jiang-feng, WU Yi-zhao
2009, 24(8): 1831-1836.
Abstract PDF(1858KB) icon1648 icon415
Abstract:
Preconditioned AUSM+(advection upwind splitting method+) scheme was discussed in details and was applied to numerical simulation of multi-component chemical reacting flows at all speeds.Based on multi-component Navier-Stokes equations with time-derivative preconditioning, an effective algorithm for simulating the reacting flows over a wide range of Mach numbers was developed using the preconditioned AUSM+ scheme.Numerical experiments, including supersonic flow, subsonic flow and low speed flow, show that the algorithm can be applied efficiently to the reacting flows at all speeds.
Design of the interface between ramjet and scramjet modules of dual combustor ramjet and flow field simulation
LI Pu, GUO Rong-wei
2009, 24(8): 1837-1842.
Abstract PDF(1041KB) icon1559 icon368
Abstract:
A preliminary study was carried out on the interface between ramjet and scramjet modules of dual combustor ramjet.Efforts were focused on the influence of the design parameters on the mixing performance using numerical method.The design parameters included the height of the step, the step geometry and the proportion of the mass flow of ramjet modules.An interface with better mixing performance was presented in the paper.Results indicate: the Mach number at the duct exit is 1.48, the total pressure recovery is 0.765, pressure ratio is 17.71 and temperature ratio is 4.05 for the free stream of the Mach number is 4.For the Mach number is 6 condition the Mach number at the duct exit, the total pressure recovery, pressure ratio and temperature ratio are 2.08, 0.502, 28.03 and 4.67 respectively.
Numerical simulation on cooling characteristics of an afterburner fuel injector with double-wall construction
LI Rui-ming, YAN Bao-hua, FAN Wei-jun, YANG Mao-lin
2009, 24(8): 1843-1848.
Abstract PDF(903KB) icon1580 icon401
Abstract:
The performance of the cooling air flow extracted from the bypass duct to cool a new fuel injector with double-wall construction for afterburner was simulated numerically.The results of the simulation and the experiment agree with each other very well.The temperature distribution of outer casing and inner pipe, and cooling air rate extracted from the bypass duct were obtained by calculations under four working conditions of the afterburner.It shows that the type of afterburner fuel injector can extract enough cooling air from the fan stream and can effectively decrease the temperature of the wall of fuel injector.
Robust engine speed control based on Takagi-Sugeno fuzzy systems
PAN Song, WEI Min-xiang, HUANG Wei-qing
2009, 24(8): 1849-1855.
Abstract PDF(1895KB) icon1591 icon373
Abstract:
The engine Takagi-Sugeno(T-S) models were obtained by sector nonlinearity based on the nonlinear two-stroke internal combustion engine model.A nonlinear engine speed controller was researched, and the system augmented method was used for the design of control algorithm without steady-state error.By considering the robust H∞, a disturbance rejection controller design for the T-S fuzzy models was presented.The stability conditions were derived using Lyapunov approach, and the problems were formulated as linear matrix inequality(LMI) problems.Finally, simulation results demonstrate the validity of these methods.
Research on sensor fault diagnosis of aero-engine based on data fusion of SPSO-SVR
LU Feng, HUANG Jin-quan, CHEN Yu, SONG Yun-feng
2009, 24(8): 1856-1865.
Abstract PDF(2867KB) icon1705 icon482
Abstract:
In consideration of the common sensor faults in aero-engine, a new algorithm was proposed based on support vector regression(SVR) trained by improved particle swarm optimization(PSO), and was used for sensor fault diagnosis system based on data fusion.A bank of SVR was applied to sensor fault detection, isolation and validation.This fault diagnosis system would isolate the fault sensor relying on the isolation mechanisms, and select the validation module for signal recovery when some fault sensors were detected.According to the simulation experiment of aero-engine sensor faults(impact fault, offset fault and drift fault), the results show that this sensor fault diagnosis system has high level of precision and is an effective way to sensor fault diagnosis under the conditions of both one and multiple sensor faults.
Design of an adaptive decoupling controller of aero-engine over whole envelop
PENG Jing-bo, XIE Shou-sheng, WU Yong, ZHAI Xu-sheng
2009, 24(8): 1866-1871.
Abstract PDF(619KB) icon1580 icon403
Abstract:
In order to achieve decoupling control of aero-engine over whole envelop, genetic algorithm was used to optimize the proportion parameters of single neural adaptive decoupling controller based on various points within envelop, whilst several groups of parameters optimized by the algorithm were used as sample data to train radial basis function(RBF)network, helping to map height and mach number on proportion parameters after tuning.The proportion parameters at every operating point can be calculated by RBF neural network.The simulation results show that the control system has a fine performance of dynamic and decoupling capability over whole envelop, and the proposed method is simple, feasible and effective.
Failure detection of actuators of aero-engine control system by interaction matrix formulation
TAO Wen-hua, YE Zhi-feng
2009, 24(8): 1872-1877.
Abstract PDF(877KB) icon1577 icon473
Abstract:
Currently there is no efficient method to detect and isolate the failure of actuators, which are an integral part of aero-engine control system.In this paper a novel technique was introduced, which allowed to formulate the difference about the actuators output through the controller's command output and the engine's actual output by means of interaction matrix.Therefore, the failure of multiple actuators could be detected and isolated successfully.The digital simulations demonstrate that this strategy has a high accuracy when it is applied in failures detection of the actuators of aero-engine control system.
Research on alignment error sensitivity and tolerance limit analysis of spiral bevel gears
TANG Jin-yuan, LEI Guo-wei, DU Jin, LU Yan-feng
2009, 24(8): 1878-1885.
Abstract PDF(2857KB) icon1662 icon481
Abstract:
Alignment errors are important influential factors to the gears' contact quality.The general model of the spiral bevel gears' tooth processed by cutter-tilt method and modified-roll method was proposed.Method of tooth contact analysis including alignment errors was established.Effects by alignment errors were investigated, the conceptions and models of alignment errors sensitivity and tolerance were proposed.According to parameters design of the gears, the effect laws and tolerance of the alignment errors could be obtained by using this modified contact analysis algorithm.Simulation analysis shows its feasibility.Alignment error sensitivity, tolerance of the alignment errors with the corresponding calculation methods could reflect the internal influence of spiral bevel gears' contact quality and installation technology due to alignment error.The research can provide a theoretical basis for improving the design quality of the spiral bevel and hypoid gears and developing the scientific installation technology.
Underdetermined blind source separation method of machine faults based on empirical mode decomposition
LI Zhi-nong, L Ya-ping, FAN Tao, LENG Chuan-guang
2009, 24(8): 1886-1892.
Abstract PDF(2404KB) icon1618 icon472
Abstract:
The traditional mechanical fault source separation method is restricted to nongaussian, stationary and mutually independent source signals, and the number of observations is assumed to be more than the number of sources.These deficiencies may cause many problems in the application of fault diagnosis, because fault signals generally do not meet these conditions.Based on these deficiencies, an underdetermined blind separation method of machine faults based on empirical mode decomposition(EMD) was proposed.The proposed method was that the mixture signals were decomposed into a series of intrinsic mode functions(IMF) by the EMD method.These IMFs and original observations were composed into new observations, which was blindly separated.The simulation and experiment results show that the proposed method is very effective.
Study on adiabatic transient behavior of tilting-pad journal bearing
MA Xi-zhi, ZHU Jun
2009, 24(8): 1893-1898.
Abstract PDF(1969KB) icon1547 icon488
Abstract:
The purpose of this paper is to study the thermal behavior of a tilting-pad journal bearing subject to a sudden dynamic load.The time-dependent Reynolds equation and energy equation were used to analyze the transient pressure and temperature of the oil film during this period.The dynamic equations were developed to simulate the motion of journal and pads.These equations with initial conditions were solved numerically using finite differential methods and the Newton-Raphson iterative scheme simultaneously.The nonlinear thermal transient response of tilting-pad bearing was simulated under a step load function.The change of maximum film temperature and minimum film thickness as well as other parameters were presented.Oil film temperatures and film thickness were found to vary considerably, and there existed some overshoot in the responses of maximum temperature and minimum film thickness, leading possibly to the damage of bearing during the transient period.
Application of improved Hilbert-Huang transform method in gear fault diagnosis
SHEN Lu, LI Jun-sheng, WANG Hong-jun, ZHANG Wen-bin
2009, 24(8): 1899-1903.
Abstract PDF(1607KB) icon1500 icon415
Abstract:
The first intrinsic mode function(IMF) is generally a multi-component as the result of the abundant frequency component in gear fault signal.Pseudocomponents in low frequency may be produced in empirical mode decomposition(EMD).An improved Hilbert-Huang transform(HHT) method was proposed to overcome these two problems.Frequency span of fault information has been achieved in frequency spectrum, so corresponding binary wavelet coefficient of narrow-band signal could be extracted.The method of correlation coefficient screening was used to remove pseudocomponent in EMD of wavelet coefficient.Local instant energy was used to extract gear fault feature.It is demonstrated that improved HHT method could diagnose the gear fault effectively.
Numerical investigations of thermal stratification in cooling channel of liquid rocket engine thrust chamber
KANG Yu-dong, SUN Bing, GAO Xiang-yu
2009, 24(8): 1904-1910.
Abstract PDF(1881KB) icon2002 icon489
Abstract:
To study the formation mechanism of thermal stratification in cooling channel and its effects on the flow and heat transfer, three dimensional turbulent fluid flow and heat transfer in a regenerative-cooling channel of liquid rocket engine were numerically investigated with Reynolds stress model(RSM) model, and the coolant was hydrogen, whose thermophysical properties varied with both temperature and pressure.The results show that thermal stratification occurs at non-flow direction, the extent of thermal stratification becomes increasingly significant as the extent of heating increases, and the thermal stratification of coolant is weakened for the existence of secondary flow in throat region;the thermal stratification has little effect on the bulk temperature increase and hydrodynamic losses of hydrogen, but has significant effect on the calculation of the wall heat fluxes and temperature.
Numerical study the influences of charge exchange ions on optical system ion beam
ZHONG Ling-wei, LIU Yu, WANG Hai-xing, TANG Hai-bin, REN Jun-xue
2009, 24(8): 1911-1916.
Abstract PDF(999KB) icon1669 icon408
Abstract:
Based on particle-in-cell(PIC) and Monte Carlo collision(MCC) method, a two-dimensional numerical model was adopted to investigate the distribution and kinetic characteristics of the charge exchange(CEX) ions in the optical system of ion thruster.The simulation results show that, the screen grid current is increased by 1.42 percent when the CEX ions are considered.On the other hand, the accelerator grid current increases from zero to 1.41 percent of the main beam current.It is indicated from the simulation results that the CEX ions originated in the far downstream region of the optics are the main reason of the accelerator grid current and the erosion on the downstream face of the accelerator grid.

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