2009 Vol. 24, No. 1

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Study on application of fluid network into the design of air system in engine
TAO Zhi, HOU Sheng-ping, HAN Shu-jun, DING Shui-ting, XU Guo-qiang, WU Hong-wei
2009, 24(1): 1-6.
Abstract PDF(676KB) icon1670 icon449
Abstract:
A new program was developed to predict the pressure,temperature and mass flow rate of the flow in engine.The air system was simplified into a fluid network comprised of nodes and elements.One-dimensional conservation equations were solved by a method of combination of pressure-correction method,fluid-thermal coupled method and coefficient-correction method.The program was validated through a model with an empirical formula,and the results showed good agreement with the empirical formula.Then the program was used to verify and improve the preliminary design scheme of a jet engine.Results show that the adjusted design parameters obtained with the help of simulation results are satisfactory.
Investigation on heat transfer of micro-jet array impinging on pin-fin surface
XIA Guo-dong, JIA Zhen, CHEN Yong-chang
2009, 24(1): 7-12.
Abstract PDF(742KB) icon1415 icon417
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An investigation on heat transfer of a micro-jet array impinging smooth and pin fin surfaces was conducted.The experimental results indicate that:(1)the dimensionless nozzle-to-target spacing(H/d) has notable effects on heat transfer coefficient of both free-surface and submerged jet impingement,and heat transfer may be enhanced with increasing Reynolds number or decreasing dimensionless jet-to-jet spacing(S/d).(2)the enhancement factor(ε) is not influenced by H/d for free surface jet,but it is sensitive to variation of H/d for submerged jet.For both free-surface and submerged jet impingement,ε increases with increasing Re.(3)The convection resistance decreases,at first rapidly and then slowly,with increasing liquid flow rate.
Numerical simulation on flow and heat transfer in channel with small spacing short pin-fin arrays
ZHANG Li, ZHANG Shu-hua, ZHU Hui-ren, LIU Song-ling
2009, 24(1): 13-17.
Abstract PDF(1057KB) icon1584 icon441
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Numerical simulation was conducted to gain greater insight into the flow structure of trapezoidal pin-fin duct and get detailed knowledge of the heat transfer on the endwall surface.The array geometries have short pin heights and small chord-wise pin spacing.Numerical results show that,the calculated flow resistances and chord-wise ejection mass flow rate agree well with the experimental data,and the heat transfer pattern is well simulated.The numerical results also show that the flow direction in pin-fin region is mainly chord-wise.There are a lower velocity and lower turbulence intensity region behind the cylinder.
Numerical simulation of effusion holes on the longitudinal ripple heat shield
TANG Chan, CHANG Hai-ping
2009, 24(1): 18-24.
Abstract PDF(871KB) icon1485 icon427
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The numerical simulation was used to study the effusion holes on the longitudinal wavy liner in the combustor.The investigation focused on the parameters affecting cooling effectiveness,including: opening ratio,height of ripple board,diameter of holes and height of cooling passage.Given the same total flow effusion from holes,the results show that the heat shield gets a higher average cooling effectiveness when the opening ratio is 3% compared with 6%;cooling effectiveness is sensitive to the height of ripple board,the heat shield gets the highest cooling effectiveness when the dimensionless height of ripple board is 1% compared with 2% and 3.33%;but there is a little influence on the cooling effectiveness of the liner with the change of the diameter of holes and the height of cooling passage.
Nonlinear analysis of large eddy simulated supersonic two-phase mixing layer
WU Hai-yan, TAO Yu-jing, WANG Yu, ZHOU Jin
2009, 24(1): 25-31.
Abstract PDF(830KB) icon1904 icon494
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The two-phase compressible mixing layer with droplets was calculated by large eddy simulation(LES) for studying the mixing law of supersonic two-phase flow.To get the sub-grid LES equations,the compressible N-S equations of gaseous phase were filtered by two-dimensional box-filter function.The droplets phase was simulated by track model,and the evaporation equations of single droplet model were employed to simulate the evaporating course.The phase space for the time series of mixing layer pressure was reconstructed by determining the embedding dimension and time-delay of the phase space reconstruction,with the method of false neighbors and mutual information.The characteristic of eddy and droplets evaporation in mixing layer were analyzed,and moreover,the nonlinear characteristic of mixing layer instability was discussed.The results show that the different development stages of mixing layer is closely related with its nonlinear eigenvalue.
Experimental study on characteristic of deflagration to detonation transition in different close end
ZHANG Peng-gang, HE Xiao-min, ZHANG Jing-zhou
2009, 24(1): 32-37.
Abstract PDF(1217KB) icon1774 icon427
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In order to investigate the characteristic of deflagration to detonation transition(DDT) in close end with 5 kinds of block ratios,a series of single detonation experiments were conducted to study the performance of acetylene-air mixtures in square detonation tube of 60 mm×60 mm×2 000 mm.The ion-probes and pressure transducers were utilized to get the velocity and pressure in the tube,respectively.The results indicate:(1) Position of DDT moves back with the accretion of block ratio in close end;(2) The block degree does not affect essential characteristic of DDT.
Study of heat transfer of turbulated cooling holes distributed close along the periphery of the aerofoil of turbine blade
LI Na, JI Hong-hu, YANG Chao
2009, 24(1): 38-43.
Abstract PDF(1877KB) icon1744 icon486
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A simplified heat transfer model was extracted from the turbulated cooling holes located close to the periphery of the aerofoil of a turbine blade.The turbulators of the holes are ring ribs with rectangular cross section.By dimensional analysis,it is shown that the Nusselt number of the cooling holes was affected not only by Reynolds and Prandtl numbers,but also by the geometry of the turbulator,the distance between the hole and the outer surface of the blade,and the ratio of fluid conductivity to solid conductivity.A detailed numerical study shows that:(1) the ring ribs increase average Nusselt number,while the distance between the hole and the outer surface of the blade affects the local heat flux and Nusselt number distributing;(2) the Nusselt number monotonously increase with the increase of rib height to holes diameter ratio,e/d,but it also lead to rapid increase of friction coefficient;(3) by increasing Reynolds number and optimizing the ratio of rib pitch to rib height,p/e,Nusselt number of the cooling hole can be increased,the optimized value of p/e is about 10.
Study effect of different thickness of porous layer on thermally driven heat transfer in a centrifugal force field
XIA Jie, CHANG Hai-ping
2009, 24(1): 44-49.
Abstract PDF(1254KB) icon1596 icon479
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Based on the research of turbine blade super cooling technology,porous medium was installed in a new kind of cooling configuration with cooling tunnels.Experiments and numerical simulations were carried out to investigate the thermally driven heat transfer rules in the new kind of cooling configuration with different thickness of porous layers in a centrifugal force field.The results of experiments and numerical simulations are consistent basically.The results of study show that the heat transfer rules of the new cooling configuration are identical under different thickness of porous layers.The thermally driven heat transfer of the cooling configuration filled with porous medium can be enhanced with increase of the rotate speed,heat flux and cooling air speed.At the same time,the heat transfer effect is weakened with increase of the thickness of porous layer.
Investigation of detached detonation induced by oblique shock in premixed supersonic flow
LIN Zhi-yong, ZHOU Jin, ZHANG Ji-ye, WANG Yu, HUANG Yu-hui
2009, 24(1): 50-54.
Abstract PDF(732KB) icon1606 icon416
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In order to study the detonation mechanism problems in the elevated initial temperature supersonic flow,a continuous heater was designed and employed to produce supersonic premixed hydrogen/air mixture flow,with Mach number of 2.6 and static temperature above 700 K;and the high speed schlieren was used to observe and analyze the direct initiation and development process of the detonation.The result shows that the oblique shock angle before the detonation initiation and the detached detonation angle are consistent with theoretical analysis.It is also found that the transition from the deflagration to detonation induced by oblique shock is rapid,and the phenomenon of detonation failure and re-initiation will exit under the circumstances of high initial temperature and low stoichiometric ratio of combustible mixture.The results obtained here provide a reference for the application of detonation in the hypersonic propulsion.
Experimental study on the combustion and flow process in a scramjet with strut injector
LIU Shi-jie, PAN Yu, LIU Wei-dong
2009, 24(1): 55-59.
Abstract PDF(1022KB) icon1718 icon461
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Experimental studies on the combustion and flow process in a scramjet combustor with strut fuel injector were presented.The results show that,the relative position of the fuel injector(strut) and flame holder(cavity) has great influence on the flame structure and scramjet performance.The combustion efficiency of fuel injected from the side of strut is better than from strut end.Combustion and flow process interact with each other intensively.Due to the quantity of heat released from combustion,the flow structure changes greatly,consequently,the fuel injection,diffusion and mixing with air are affected.
Numerical simulation of detonation wave interacting with turbine blade
JIANG Lian-you, YAN Chuan-jun, DENG Jun-xiang, ZHENG Long-xi
2009, 24(1): 60-64.
Abstract PDF(7548KB) icon1565 icon379
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This paper conducted preliminary numerical simulation of their interactions by means of CFD method.The stoichiometric hydrogen-air mixture was employed as reactants and 1-step finite rate reaction model was used to investigate the interaction of detonation wave with a stationary blade.The simulation results indicate that the detonation wave attenuates after passing the blade passage,and generates a strong compression wave reflecting back upstream from leading edge of blade at the same time,This mitigates the pulse effect on turbine blade and causes a short period of back mass flow at turbine inlet surface.A high pressure environment is formed at the leading edge,The pressure time sequences at pulse detonation engine(PDE) exit surface shows many pairs double-peaks are gradually attenuated.
Study of aerodynamic heating predictions for hypersonic aircrafts by tracking the surface stream trace
HAN Dong, FANG Lei
2009, 24(1): 65-69.
Abstract PDF(864KB) icon1842 icon505
Abstract:
The boundary layer edge conditions were determined by 3-D CFD(Computational fluid dynamics) method and solved by 3-D Euler equation on structured grids;the wall stream trace was computed based on the stream function theory and flow parameters;the heating rates of staypoint with constant and variable specific heats were computed by the theory and semi-experienced formulas,while the heating predictions of non-staypoint were calculated based on the reference enthalpy theory and locally similar theory.The calculated results of the heating rates of double blunt biconic are in good agreement with existing experimental data and classic engineering methods,with average precision about 10%.It is applicable to the parametric design of hypersonic aircrafts.
Design and study of combustor for micro-turbojet engine
LI Ming, WU Er-ping, SUO Jian-qin
2009, 24(1): 70-74.
Abstract PDF(604KB) icon2086 icon490
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An annular combustor with evaporation tubes was designed for certain micro-turbojet engine.According to performance requirements of the engine,designed main components of the combustor,calculated flow distribution and flowage parameters of the combustor.Refers to overall structure of the engine,designed test apparatus of the combustor and carried out the several performance experiments.The results show that the designed combustor meets the demand for structural project,main components and overall performance.
Unsteady internal performance study of counterflow vectoring thrust nozzle
WANG Ming-sheng, YANG Jian-jun
2009, 24(1): 75-82.
Abstract PDF(2202KB) icon1841 icon420
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Internal performance of unsteady flow of counterf low thrust vectoring no zzle has researched base on numer ical simulat ion. The results show, in the former of half aun??steady period, the perfo rmance parameters are almo st the same under at tachment and deat tachment cases, but have a great dif ference in the after of half a period. It is the representation of the flow hy steresis. T he hyster esis leads the at tachment of main f low diff icult to depart from the w all. The origin of hysteresis may be relate to shear lay er. The evolv ement of counterf low and cof low shear layer present a difference behave, and may play a common role in main flow deat tachment. Lastly, the results of unsteady flow point out, counterf low thrust vectoring nozzle is a ef ficiency f luidic vecto ring nozzle.
Study on the high-accuracy compact-finite-difference schemes for computational aeroacoustics
LIU Zhan-xin, HUANG Qi-bai, HU Li, YUAN Ji-xuan
2009, 24(1): 83-90.
Abstract PDF(2618KB) icon1458 icon489
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The optimized pentadiagonal compact finite difference schemes were presented in this paper.Through Fourier analysis,the optimization object was converted to find the minimum of a nonlinear multi-variable function with multi-constraint.The advanced sequential quadratic programming(SQP) method was employed to find the minimum.In order to obtain high accuracy and resolution,the following strategies were applied:(1) the minimum is computed directly from integral errors of the scaled wavenumbers;(2) absolute error criterion is used for evaluating the deviation between effective and exact wavenumbers,and the waves with different wavelengths have the same error limit under this criterion;(3) the wavenumber domain for optimization is identical with the well-resolved domain.The asymptotical stability of the schemes is satisfied by adjusting the Taylor accuracy and error limits,and proved through the theoretical analysis.The increased performances of the optimized schemes are demonstrated through application to benchmark problems.
Numerical simulation of glaze ice accretions on an airfoil
ZHANG Qiang, CAO Yi-hua, HU Li
2009, 24(1): 91-97.
Abstract PDF(2294KB) icon1776 icon455
Abstract:
An Eulerian method to numerically simulate glaze ice accretions on an airfoil has been presented.Based on two-phase flow theory,the governing equations of the airflow and droplets were established.A permeable wall was proposed to simulate the droplet impingement on the airfoil surface.An integral boundary layer method,modified to consider the roughness effect,was employed to evaluate the convective heat transfer coefficient.The thermodynamic model for glaze ice accretions was presented by performing the mass and thermal balances.The process of ice accretions was simulated with the assumption that ice accumulates layer-by-layer,and the ice shape was built with the assumption that ice grows in the direction normal to the airfoil surface.The glaze ice accretions on a NACA 0012 airfoil at different environmental temperatures were investigated,while the predicted results and experimental data were compared,indicating that the simulated method presented in this paper is feasible and effective.
Linear parameter varying estimation for early deteriorated turbo fan engine performance parameter
HAN Xiao-bao, WANG Zhong-sheng
2009, 24(1): 98-103.
Abstract PDF(5155KB) icon1535 icon425
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To estimate the component performance parameters of early deteriorated areoengine,a linear parameter varying(LPV)filter was given for LPV model of a turbofan engine.Based on conceptions of affined parameter-dependent quadratic Lyapunov function and affined quadratic stability,the filter design method was converted into a normal linear matrix inequalities(LMI)constrained convex optimization by introducing the lemma of multiconvexity.Also the difficulties in solving the optimization problem with parameterized linear matrix inequalities(PLMI)constraint were avoided.Besides the convenience of filter gain scheduling,the accuracy and robustness of the filter were validated by simulation on parameter estimation for the early-deteriorated turbofan engine.
Study on back pressure and self-starting characteristics for sidewall-compression inlet with variable internal contraction ratio by moving cowl
PAN Jin, ZHANG Kun-yuan
2009, 24(1): 104-109.
Abstract PDF(1218KB) icon1724 icon419
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An experimental study was performed at Mach 3.85 wind tunnel about back pressure and self-starting characteristics for sidewall-compression inlet with variable internal contraction ratio.The results show that,the internal contraction ratio has effects on back pressure characteristics of sidewall-compression inlet;the inlet with internal contraction ratio 1.19 can withstand a maximum back pressure of 23.42 times static pressure;the inlet with internal contraction ratio 1.24 can withstand a maximum back pressure of 26.44 times static pressure;The sidewall-compression inlet can realize self-starting by moving cowl backwards.
Fast modeling method for aircraft wake vortices
ZHOU Bin, WANG Xue-song, WANG Guo-yu, XIAO Shun-ping
2009, 24(1): 110-115.
Abstract PDF(2112KB) icon1778 icon473
Abstract:
The mass,velocity and wing shape of the aircraft decide the intensity of wake vortex.The passive conservative model can better depict the movement evolution rule of water vapor and potential temperature in wake vortices.Since parametric studies are computationally expensive to the large amount of CPU time per simulation.In addition,it can't forecast the state distribution characteristic of any aircraft wake vortex in a real-time manner.Therefore,a fast modeling method for aircraft wake vortex was presented.It has solved the problems,such as the high request for computer time,long simulation time and lack of real time simulation.This can provide a theoretical basis to avoid former airplane's wake vortex and reduce the wake accident.
Study on the aerodynamic noise of a fastback car with rear view mirrors in uniform motion and accelerated motion
LAN Tian, KANG Ning, ZHENG Hao, HU Chang-an
2009, 24(1): 116-121.
Abstract PDF(1201KB) icon1581 icon477
Abstract:
The flow field around a simplified fastback car with rear view mirrors and aerodynamic noise at some receiving point were numerically simulated and analyzed using CFD(Computational fluid dynamics) software FLUENT.The pulsating flow field was simulated by the large eddy turbulence model and the momentum equations were discretized with the unbounded central difference scheme.The calculations were performed under three conditions: uniform motion with two running speeds and accelerated motion.The influences of pulsating flow field and aerodynamic noise by uniform motion speed,uniform and accelerated motions were investigated.The results show that with the increase of uniform motion speed,the velocity,amplitude of pulsating pressure,sound pressure level corresponding to each frequency and total sound pressure level at the receiving point become bigger,the pressure becomes smaller;at the same motion speed,the velocity,sound pressure level corresponding to each frequency and total sound pressure level in accelerated motion are greater than those in uniform motion,the pressure is smaller.
An engineering method for predicting off-design performance of multistage axial compressors
WU Hu, ZHANG Liang, FENG Wei-lin
2009, 24(1): 122-126.
Abstract PDF(1320KB) icon1543 icon434
Abstract:
An analytical model for simulating the component characteristics of axial flow fan and high-pressure compressors was established based on their geometry,high speed characteristic maps and design point aerodynamic parameters of the engines.A computer program was fulfilled and three numerical examples were given.Comparison between the computed results and experimental data shows that these models and methods are practicable,and could be used in the engineering applications.It is remarkable that the model and method can be used to predict low speed characteristics of axial compression system component during simulation of start-up process of turbofan or turbine jet engines.
Design research of supersonic fan blade profile
ZHOU Zheng-gui, WANG Guang-wen
2009, 24(1): 127-131.
Abstract PDF(915KB) icon1706 icon428
Abstract:
To design low-flow loss supersonic fan blades,a design software of the blades was developed based on numerical optimization method.The blade main geometrical parameters were selected as blade design parameters.For the first stage of fan of inlet flow in axial direction,the objective function was set as minimum flow loss at given specific work.The optimal blades thickness increase along blade chord direction,so the cascade passage is contractive;in general,it results in the decrease of speed and increase of pressure of the supersonic flow passing through the cascades.There are several shock waves in the flow fields of cascades constructed by the optimal blades,and the flow loss is quite low.The design results show the feasibility of this supersonic blade design method,and provide new ideas for supersonic fan blade design.
Numerical investigation of wake/shock interaction in oscillating blade row
HUANG Xiu-quan, ZHOU Xin-hai
2009, 24(1): 132-136.
Abstract PDF(1634KB) icon1584 icon425
Abstract:
This paper investigated numerically the influence of wake/shock interaction on the unsteady flow in oscillating blade rows.The numerical scheme chosen is an advanced harmonic method.Based on Fourier transform,turbomachinery unsteady flow variables can be decomposed into a time-averaged part and a number of harmonics identifiable by their frequencies.Thus,time-domain unsteady Navier-Stokes equations can be converted to frequency-domain steady Fourier coefficient equations.The solution of Fourier coefficient equations was obtained by using a conventional pseudo-time marching scheme.To speedup the solution convergence,local time stepping and multi-grid acceleration techniques were used.In this paper,the numerical method was used to study the unsteady flow response under wake and blade vibration interaction.The test case chosen was NASA67 Rotor oscillating a first torsion fashion.The results show an obvious influence of upstream wake on the unsteady flow in oscillating blade rows.In the presence of the upstream wake,shock in blade passages reveals considerable excursion in the axial direction and blades witness increased amplitude and temporal periodicity losing of the unsteady force.
Aerodynamic optimization of a low speed compressor based on circumferential vorticity
GUO Ming, LI Qiu-shi, ZHOU Sheng
2009, 24(1): 137-142.
Abstract PDF(1908KB) icon1329 icon400
Abstract:
Based on artificial neural network and genetic algorithms,the aerodynamic optimization of stacking curve for a low-speed compressor rotor was implemented by controlling circumferential vorticity.The adiabatic efficiency under small flow rate condition was optimized.The numerical results show that the distribution of circumferential vorticity at the exit of rotor is improved,the adiabatic efficiency under small flow rate zone is enhanced,and the stall margin is greatly increased.The optimization approach have high efficiency,and can provide a ordered flow field for compressor.
Experimental investigation on characteristic of rotating stall in a low-speed axial compressor
TU Bao-feng, HU Jun, WANG Zhi-qiang, LI Liang
2009, 24(1): 143-149.
Abstract PDF(1359KB) icon1632 icon479
Abstract:
The full flow characteristic of a 2-stage low-speed axial compressor was investigated with uniform inlet flow.The emphasis of this work was put on the characteristic of rotating stall at different flow coefficient and the stall inception.The results indicate that the modal wave will appear before stall about 30 rotor revolutions,and the rotary speed of modal wave is about 40% rotor speed.The modal wave can be detected across the compressor.The second stage comes into rotating stall first under the effects of the disturbance of the modal wave.The rotary speed of the early stall cell is about 83.3% rotor speed,and the speed will decrease as the stall cell spreads to the first stage,at last about 41.9% rotor speed.As the flow coefficient reduces,the frequency of the stall cell will decrease,and the scope of the stall cell will extend accordingly.
A blading design method for axial/centrifugal compressor airfoils using arbitrary camber lines
JI Guo-feng, GUI Xing-min
2009, 24(1): 150-156.
Abstract PDF(2522KB) icon1624 icon460
Abstract:
A blading design method for both axial and centrifugal compressor blades was discussed by using arbitrary camber lines.This method was based on through flow calculation.Three dimensional blades consistent with the result of through flow calculation can be obtained by modifying the distribution of velocity circulation.Meanwhile,it can control main blade/splitter blading and the shape of trailing edge of the airfoil.It has been applied to the design of compressor blades of some micro-engines,and fairly ideal airfoils are obtained.Also,this method can be used for optimization of compressor blades.
Experimental study on flow in the pump sump using PIV
SHAO Chun-lei, GU Bo-qin, CHEN Ye
2009, 24(1): 157-161.
Abstract PDF(1926KB) icon1959 icon441
Abstract:
Particle image velocimetry(PIV) system,pump experimental facility and test scheme were introduced.An experimental investigation of pump sump internal flow was performed at five different flow rates by means of PIV.The velocity vector distribution was obtained,and the characteristic parameters on the outlet section and the instantaneous volume flow rate on the inlet section were calculated.The results indicate that,the velocity distribution is uniform in the inlet and non-uniform in the outlet,and biased flow phenomenon appears in the outlet of the pump sump.Under the scope of the investigation,axial velocity distribution uniformity on the outlet section is improved and the velocity-weighed average bias angle decreases with the increase of flow rate.The instantaneous volume flow rate is impressively pulsatile and presents the Gaussian distribution,and the relative pulsation amplitude is within 6%.The mean flow rate in a longer period agrees with the flow rate measured by the turbine flowmeter.This confirms that the PIV system can be applied to measure the instantaneous volume flow rate and investigate the unsteady characteristics.
Singularity analysis of axisymmetric vectoring exhaust nozzle
WANG Yu-xin
2009, 24(1): 162-168.
Abstract PDF(2339KB) icon1552 icon418
Abstract:
Setting up the configuration bifurcation equation of the axisymmetric vectoring exhaust nozzle(AVEN) and utilizing the homotopy tracing approach,the configuration bifurcation behaviors of the AVEN driving parallel mechanism and the driving kinematic chains of the divergent flaps were analyzed.It is found that whether deflecting or not,the turning points will exist corresponding to the bifurcation parameter of the area exhaust nozzle,and the turning points will disappear corresponding to the bifurcation parameters of the deflecting angle.While the AVEN is in non-vector status,the driving kinematic chain of divergent flaps is at its multi-singular position.Both the turning points and multi-singular positions will lead the motion of the AVEN uncertain.This kind of motion uncertainty is harmful to the safety of aircrafts equipped with the AVEN.
Study on fusion diagnosis techniques of wear faults in synthesized monitoring of aero-engine
CHEN Li-bo, SONG Lan-qi, CHEN Guo
2009, 24(1): 169-175.
Abstract PDF(1914KB) icon1659 icon417
Abstract:
Although spectrometric oil analysis(SOA) is a widely applied technique for wear condition monitoring of lubricating system,this single monitoring technique is difficult to accurately predict some damages or failures in oil wetted system including bearing fatigues of aero-engine.In this paper,two techniques including SOA and auto debris classifier were applied to synthetically monitor a certain aero-engine,the Dempster-Shafer(D-S) evidence theory was used to implement fusion diagnosis,and an engine oil monitoring expert system was developed to carry out fusion diagnosis.Finally,some examples were analyzed;the results indicate that synthesized monitoring and fusion diagnosis is an important approach to increase the reliability for forecasting failures of aero-engine.
Analysis for stiffness on the bend vibration natural frequencies of a helicopter tail drive system
ZHU Zi-bing, ZHU Ru-peng, BAO He-yun, JIN Guang-hu
2009, 24(1): 176-180.
Abstract PDF(529KB) icon1838 icon446
Abstract:
The helicopter tail drive system was simplified,and it was presented that a helicopter tail drive system was a cascade system comprising shaft segments and disks.A bending dynamic analysis model in which the support stiffness of the bearing and coupling were included was established.Using transfer matrix method,the differential equations were solved.The results show that the effect of the angular stiffness and the radial stiffness of coupling on natural frequencies of the helicopter tail drive system is different,and the natural frequencies could be reduced with the increase of shaft segments or stiffness of the bearing.
Analysis of foil predeformation influence on the static characteristics of bump foil journal bearings
LIU Zhan-sheng, XU Huai-jin, ZHANG Guang-hui, WANG Yong-liang
2009, 24(1): 181-188.
Abstract PDF(2828KB) icon1584 icon434
Abstract:
The influence of foil predeformation on the static characteristics of bump foil journal bearings was analyzed in this paper.The air film thickness model was developed with considering the air compressibility and foil predeformation.Both finite difference method and Newton-Raphson method were applied to solve coupled Reynolds equation and air film thickness equation.Compared to the bump foil bearings with nominal clearance,air film thickness,pressure distribution and load carry capacity were discussed.The results indicates that the bump foil bearing with predeformation provides a better rotating stability and a greater load carrying capacity,and in some extent the foil predeformation is larger,the load carry capacity is higher.
Research on improved tooth contact analysis algorithm of spiral bevel gears
TANG Jin-yuan, LU Yan-feng, ZHOU Chao
2009, 24(1): 189-195.
Abstract PDF(2063KB) icon1484 icon418
Abstract:
According to the deficiency of tooth contact analysis analysis,an improved tooth contact analysis algorithm was proposed.Based on the spatial surface engagement theory,the Enler-Rodrigues formula and the equivalent relationship between the contacted areas' shapes,the tooth contact analysis algorithm was proved.Through the equation transformation,the dimensions of the nonlinear equations for the contact points' position were decreased.The initial value was obtained regularly by the meshing equations.Taking a pair of spiral bevel gears as an example,the algorithm was proved.The results show that the complexity of initial values is decreased,the stability of the solution for nonlinear equations is enhanced,and the complex calculation of relative curvatures of the tooth surface is avoided by using the geometrical educational relationships between the geometrical parameters.
Analysis of temperature field and coupled thermal and structure for finger seal
SU Hua, CHEN Guo-ding
2009, 24(1): 196-203.
Abstract PDF(2284KB) icon1788 icon516
Abstract:
The thermal analysis model for a repetitive section of single stick,two-layer finger seal was established herein.The thermal analysis boundary conditions were confirmed according to the finger seal's working situations.The temperature field in different conditions of the finger seal sections,including the rotor and the back plate,was obtained using the finite element method(FEM).It shows that the position of the highest temperature part of the finger seal is related to the upstream temperature.The highest temperature part moves from the finger foot to the middle part of the high pressure finger stick with the increase of upstream temperature.The coupled thermal and structural analysis of finger seal was also conducted and the finger seal's hysteresis and contacting performances considering the thermal character effect were obtained.If compared with the performance analysis results without considering the thermal effect,the hysteresis is lower and the contact pressure between the finger foot and the rotor is much higher with consideration of the thermal effect.
Design and analysis of a spatial crank-rocker flapping-wing mechanism
XU Yi-cun, ZONG Guang-hua, BI Shu-sheng, YU Jing-jun
2009, 24(1): 204-208.
Abstract PDF(1014KB) icon1498 icon547
Abstract:
Topological structure of stereo shocks in the annular clustered plug nozzle
XIE Kan, REN Jun-xue, LIAO Yun-fei, LIU Yu
2009, 24(1): 209-216.
Abstract PDF(1887KB) icon1497 icon467
Abstract:
By using a visualization method which only shows the grids of the stereo shock zones between unites of the annular clustered plug nozzle,the numerical results were reprocessed.From the visualized images of the three-dimension interference shock,three kinds of topological structures of interference shock and a kind of ridge contour of energy leak were summarized.The performance loss caused by these three topological structures was analyzed with the aid of the experimental data,thus providing a reference for further design.
Research on temperature rise characteristics of hydrogen peroxide in the process of self decomposition
LI Mao-de, CHENG Hui-er
2009, 24(1): 217-223.
Abstract PDF(2241KB) icon1355 icon398
Abstract:
Based on the self decomposition process of aqueous hydrogen peroxide,the mathematical temperature rise models were set up,which were related to concentration,decomposition rate,thermal property and heat exchange with the environment.The research results of temperature rise provide important theoretical basis for the storage,transport,heat transfer and combustion propulsion control,contributing to further understanding of thermal chemistry mechanism of hydrogen peroxide.
Effect of the return flow locations on the thermal stratification in liquid oxygen tank of rocket
CHENG Xiang-hua, LI Yan-zhong, CHEN Er-feng, ZHANG Hua-zhao
2009, 24(1): 224-229.
Abstract PDF(757KB) icon1886 icon423
Abstract:
The engine of cryogenic liquid rocket is required for fully precooling by natural circulation before launching,and the return flow location of the circulation loop plays an important part in field distribution of tank.In the present investigation,the physical field of tank with different return flow locations was simulated numerically based on computational fluid dynamics(CFD) technique,the distributions of temperature and velocity fields were depicted,the effect of the return flow location on thermal stratification was analyzed.It is found that the return location at 2 meter above the bottom header is optimal,where the volume and depth of subcooled liquid oxygen in tank have the most values,thus providing an important theoretical support to the design of rocket propulsion system.
Method of defect recognition in solid motor CT testing
ZHU Min, LU Hong-yi, CONG Pei-sheng, LI Hai-yan
2009, 24(1): 230-234.
Abstract PDF(1507KB) icon1904 icon407
Abstract:
In order to recognize the defects in the solid motor,a new method integrating image moment invariants method and histogram analysis method was put forward.Firstly,the cracks were distinguished from other defects by using image moment invariants method to recognize the shapes of defects.Secondly,histogram analysis method was used to calculate the gray intervals of bubbles and slag inclusions,and then distinguish them.So defects in solid motor were recognized automatically.The problems such as low recognition efficiency and low veracity induced by manual defect recognition are thus resolved and the capability of solid motor is ensured.
Research of vibration suppression in the precision real time pointing and tracking system
QIN Li, YANG Ming
2009, 24(1): 235-240.
Abstract PDF(1835KB) icon1309 icon428
Abstract:
The vibration of the satellite was analyzed,and a mathematical model of real-time pointing and tracking system was built up.An immune feedback proportional integral differential(PID)controller based on fuzzy rules was presented,of which including an active term controlling the response speed and an inhibitive term controlling the stabilization effect;a fuzzy logic was implemented to approach the inhibitive term.Also,the genetic algorithm was adopted for parameter selection according to its optimizing characteristic.At last,simulation results verify the vibration suppression performance and show the highly robust and efficient controller design.

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