2009 Vol. 24, No. 3

  Previous Issue | Next Issue 
Display Method:
Numerical study on main shaft inner cooling channel of a micro turbojet
LIU You-hong, SHAN Peng
2009, 24(3): 477-482.
Abstract PDF(1130KB) icon1290 icon442
Abstract:
The innovative ideas of a high power density micro-turbojet engine with a thrust 100 N and a rotational speed 100 000 r/min were presented in this paper.And,the research focused on the new design feasibility of the main shaft inner cooling channel,especially on the pumping air mass flow capacity of the simple front nut micro-pumps.The flow field and the temperature field of the main shaft inner cooling channel were numerically simulated based on the Navier-Stokes equations.The problem with the boundary conditions coupling was solved by iterative method.The numerical results show that the cooling performance of the main shaft inner channel is determined by the number and structure of the simple front nut micro-pump.The new design of the main shaft inner cooling channel,the simple front nut micro-pump and the numerical method can be applied to the research of other types of micro engines.
Numerical simulation of flowfield in a multi-swirler array lean direct injection combustor
ZHANG Qun, XU Hua-sheng, ZHONG Hua-gui, HOU Min-jie
2009, 24(3): 483-487.
Abstract PDF(1374KB) icon1853 icon449
Abstract:
The flowfield in a lean direct injection(LDI) combustor with co-rotating multi-swirler array was investigated using Reynolds stress model(RSM) computationally.The computational results indicate that the recirculation zones generated by nine swirlers deform and decay rapidly,and a unified and large swirling flow is formed far downstream of the swirler array.The existence of recirculation zones and strong turbulence levels indicate the potential for excellent combustion performance and low NOx emissions.The RSM-computed results were compared with laser doppler velocimeter(LDV) measurements.The results indicate that the RSM accurately describes most of the flow characteristics,contributing to solve recirculation zones and high velocity gradients.
Analysis of the combustion and flow field characteristics of advanced vortex combustor
DENG Yang-bo, LIU Shi-qing, ZHONG Jing-jun
2009, 24(3): 488-493.
Abstract PDF(1486KB) icon1630 icon504
Abstract:
In this paper,numerical simulation was carried out to study the mechanism of stabilitating flame and reduce the polutant exhaust and the influences of the major parameters on combustion stability,combustion efficiency and emissins of advanced vortex combustor(AVC).The flow resistance,trapped vortex configuration and stability,combustion efficiency of AVC were influenced by the position,angle and equivalence ratio of airflow jet in the cavity between fore-body and after-body.The position of airflow jet in the cavity had most effect on that.
Application of unsteady fluid network to air cooling system in engine
HOU Sheng-ping, TAO Zhi, HAN Shu-jun, DING Shui-ting, XU Guo-qiang, WU Hong-wei
2009, 24(3): 494-498.
Abstract PDF(583KB) icon1441 icon489
Abstract:
A new approach combining fluid network and unsteady simulation method was developed to predict the unsteady characteristic of pressure,temperature and mass flow rate of the flow in engine.The air cooling system was simplified into a fluid network comprised of nodes and branches.Conservation equations were solved by a newly introduced method to deal with the computational unstabilization problem.As a validation,the program was applied to a model which had provided a correlation,and the computational results show good agreement with the benchmark.Then the program was used to predict the unsteady characteristic of flow in the cavities along the axis in the engine.
Influence of angles and hole pitches on discharge coefficients of expanded holes at inlet and outlet
LI Guang-chao, ZHU Hui-ren, FAN Hui-ming
2009, 24(3): 499-506.
Abstract PDF(2062KB) icon1867 icon519
Abstract:
This paper presented discharge coefficients of the expanded holes at inlet and outlet with plane angles of 20°,45°,90°,radial angles of 0°,30°,65° and the ratios of pitch to diameter of 2,3,4.The momentum flux ratios varied in the range from 1 to 8.The results show that discharge coefficients of radial angle =0° increase significantly when the plane angles increase from 20° to 90°.The effect of plane angle becomes weak with the increasing radial angles.Radial angles have weak influence on the discharge coefficients of plane angle=20° and discharges coefficients of plane angle=45°and plane angle=90° decreases when the radial angles increase from 0° to 65°.Discharge coefficients of plane angle=90°increase when the ratios of hole pitch to the diameter increase from 2 to 4.
Numerical investigation on film cooling effectiveness of stator blade with different angles
YAO Yu, ZHANG Jing-zhou, GUO Wen
2009, 24(3): 507-512.
Abstract PDF(1413KB) icon1814 icon496
Abstract:
The film cooling characteristics on blade surface were numerically investigated using the two-equation turbulence model of the shear-stress transport.Three-dimensional turbulent flow in turbine cascade and the cooling effectiveness on blade surface were carried out under the same coolant total pressure.The influence of the cooling effectiveness of cylindrical film cooling holes on the blade suction surface with varying film hole inclination angles was investigated.Results show that the front inclination of the film cooling hole may improve the film cooling effectiveness for every row of film cooling holes,and the improvement is more obviously for the first row of film cooling holes.
Experimental investigation on film cooling effectiveness of multi-hole at longitudinal wavy surface
CHANG Guo-qiang, CHANG Hai-ping, CHANG Fei, HU Xiao-dong, SHAN Xue-qing
2009, 24(3): 513-518.
Abstract PDF(1005KB) icon1734 icon464
Abstract:
This paper described experimental studies on film cooling effectiveness of a corrugated wall involving multi-holes for the sake of cooling air injection.The influences of the arrangements of film cooling holes,average blowing ratio and main flow Reynolds number on the film cooling effectiveness were studied.Four types of hole arrangements were investigated at four Reynolds numbers of the main flow,ranging from 1.2×105 to 2.5×105,and average blowing ratios ranging from 0.2 to 2.0.The results indicate that the average blowing ratio is the main contributing factor to film cooling effectiveness,which varies with the shape of the wall among a large range of average blowing ratio.The rows of hole on the valley and in the downstream region near the valley can decrease the film cooling effectiveness.Conversely,the rows of hole on the crest and in the vicinal region of the crest can get better value.
Numerical simulation of film cooling in leading edge of turbine blade
DAI Ping, LIN Feng
2009, 24(3): 519-525.
Abstract PDF(1192KB) icon1754 icon461
Abstract:
Film cooling characteristics of a turbine blade's leading edge with two rows cooling orifices were investigated.The flow and heat transfer characteristics about two rows of coolant at turbine blade's leading edge were acquired in the study.Furthermore,this paper calculated film cooling effectiveness when the injection angle was 25°,35°,45°and 65°.The computed results were presented in the form of adiabatic effectiveness contours on the blade surface and compared with experimental results.It was found that the strength and the size of vortex could be reduced by decreasing injection angle.It's proven that the best cooling effectiveness is provided by a small injection angle of 25°to the stagnation line.The results show that the transportation of two rows of staggered coolants is complicated.It's also shown that two-layer k-ε turbulence models are better than common k-ε turbulence models,and the description of coolant jet flow field in the turbine cascade is reasonable.
Experimental research of surface boiling heat transfer of hydrogen peroxide
LI Mao-de, CHENG Hui-er
2009, 24(3): 526-531.
Abstract PDF(1841KB) icon1732 icon455
Abstract:
According to heat and mass transfer theory,the heat transfer of surface boiling of hydrogen peroxide solution under decomposition process was analyzed.The basic relation of heat transfer coefficient was presented.Based on the experimental data in the range of concentration from 5% to 30%,it is shown that,surface heat transfer coefficient will increase with the heat flux,bulk temperature and concentration,and there exists a maximum value of temperature difference between wall and solution,which will decrease with the increase of heat flux,bulk temperature and concentration.
Experimental investigation on leakage characteristics of finger seal
BAI Hua-lei, JI Hong-hu, JI Guo-jian, CAO Guang-zhou
2009, 24(3): 532-536.
Abstract PDF(724KB) icon1639 icon479
Abstract:
Experimental investigation on leakage characteristics of baseline finger seal had been made.The results show that the flow factor of finger seal at initial static state is high and hysteresis is obvious.With the increase of usage time the flow factor decreases gradually and finally approaches to a steady state.Under this condition,the influence of clearance between fingers of finger seal on flow factor is great;with the increase of pressure drop the flow factor increases at first and gradually reaches to a constant level;the rotor speed has little affect on flow factor;and with the increase of the number of wafer the flow factor decrease.
Effect of rib turbulator orientation and bleed hole location on flow character
GUO Tao, ZHU Hui-ren, LI Guang-chao, XU Du-chun
2009, 24(3): 537-541.
Abstract PDF(829KB) icon1862 icon459
Abstract:
According to the flow in the channel with rib turbulators and double-row bleed holes,the effects of the rib turbulator orientation and the bleed hole location on the discharge coefficient and the total pressure coefficient distribution had been investigated.The rib tubulator orientation angles were 60°,90° and 120°.The bleed holes were located at 1/4 rib distance downstream from the front rib,the middle of rib distance,1/4 rib distance upstream from the behind rib.The results indicate that the rib turbulator orientation and the bleed hole location do not change the distribution of discharge coefficient and the total pressure coefficient along the channel;the discharge coefficient increases with the increase of the rib tubulator orientation angle;the absolute value of the total pressure coefficient in the channel with 60° and 120° ribs is approximately same and less than that in the channel with 90° ribs;the discharge coefficient and the absolute value of the total pressure coefficient decrease while the bleed holes are close to down stream between two adjacent ribs.
Heat transfer characteristic of steam-water two-phase pipe flow under high gravity
ZHAO Mei, SONG Bao-yin, YAO Qiu-ping
2009, 24(3): 542-546.
Abstract PDF(562KB) icon1523 icon424
Abstract:
In the present work,a rotating platform was established,whereby the experiment for investigating flow and heat transfer characteristics of the steam-water two-phase mixture flowing in a pipe positioned in radius direction of the platform was conducted by means of electric heating.The test section was a plexiglass circular tube with inner diameter of 20 mm and length of 400 mm.Different gravities were obtained by changing rotational speed,and the effect of gravity on the heat transfer characteristic of steam-water flow was investigated.The results show that the bigger the gravity,the higher the pressure and flow resistance,and the lower the flow rate,the lower the void and the heat transfer capability,as well as the bigger the heat transfer coefficient in outside pipe.
Experimental study of combustor using low calorific value fuel
HE Min, Yang Ling, Feng Da-qiang, ZHONG Hua-gui, QU Cheng-ze
2009, 24(3): 547-551.
Abstract PDF(802KB) icon1643 icon429
Abstract:
Combustions of low calorific value gas fuel in aero engine combustor were investigated experimentally,and the design of the combustor was improved.The combustion efficiency was promoted by decreasing gas velocity of primary zone and heating gas fuel.Combustor exit temperature was increased by amendments of combustor dome and fuel nozzle,and combustor temperature distribution was optimized by adding dilution tube into dilution zone of combustor.The experimental research reveals that combustion efficiency and exit temperature profiles of improved combustor are better than the prototype combustor.
Analysis of the scattering characteristic for the hypersonic flow field of semi-sphere
CHEN Wei-fang, CHANG Yu
2009, 24(3): 552-557.
Abstract PDF(1833KB) icon1664 icon512
Abstract:
To understand the interaction mechanism between electromagnetic waves and reentry plasmas and the effect on the reentry communication and scattering characteristic of reentry vehicles,a piecewise linear current density recursive convolution finite-difference time-domain(PLJERC-FDTD) algorithm was applied to study the scattering characteristic for the hypersonic flow fields of conductive metal semi-sphere.The effects of incidence wave frequency,scattering angle,Mach number and altitude on the radar cross section(RCS) were analyzed.The results demonstrate that the forward RCS is the maximal RCS of all scattering orientations.The backward RCS and the bistatic RCS of flow fields vary little with Mach number and altitude for L and S wave band when the Mach number is not more than 10 in this article,and the margin of the backward RCS and the bistatic RCS between flow fields and semi-sphere is small.The forward RCS of flow fields is more than that of semi-sphere for L and S wave band because of the over-dense plasma shell when the Mach number is 14 or 16 in this article,and the difference of the bistatic scattering characteristic between flow fields and semi-sphere is obvious.
PIV experimental study on flow characteristics of synthetic jets
TAN Xiao-Ming, ZHANG Jing-Zhou
2009, 24(3): 558-565.
Abstract PDF(2815KB) icon1582 icon483
Abstract:
The characteristics of flowfields of synthetic jets with slot-nozzle and hole-nozzle were investigated experimentally by utilizing Particle Image Velocimetry(PIV).The results show that: the formations of the synthetic jets from different-nozzles are the same.During the formation process,the rings of vortexes were generated,developed,broken down and merged together periodically,forming a steady jet within a certain normal distance near the orifice exit.The time-averaged flowfields of the synthetic jets were continuous and steady.However,the slot-nozzle synthetic jet appeared wider than the hole-nozzle synthetic jet with a bigger spreading angle.The velocity profiles of the slot-nozzle synthetic jet along the slot-width and the horizontal hole-nozzle synthetic jet appeared symmetrically and self-similarly.But,the velocity profiles of the slot-nozzle synthetic jet along the slot length direction took on a saddle shape and disappeared with the increase of normal distance from the nozzle.
Influence of synthetic jet actuator arrays on the mixing in coaxial jets
LIU Yan-ming, WANG Bao-guo, LIU Shu-yan, WU Nai-ming
2009, 24(3): 566-572.
Abstract PDF(1405KB) icon1607 icon476
Abstract:
Detailed unsteady numerical simulation has been carried to investigate the mixing of coaxial jets with zero-mass-flux synthetic jet actuator array placed side by side around coaxial jets.Firstly,the influence of an array of actuators and two arrays of actuators on the flowfield was studied,respectively,by analyzing their control effectiveness comparatively.Secondly,both the temperature fields of the primary jet and mixing processes were analyzed to study the mixing control mechanism of synthetic jet actuator array.In addition,the effect of adjacent synthetic jets was considered during the analysis.The results show that the mixing enhancement can be achieved by using synthetic jet actuators,which result from the stronger instability of flow.Both of the actuator's configurations can result in the significant mixing enhancement,but the former exhibits more stronger controlling ability due to bigger acting force of adjacent synthetic jet than that of single synthetic jet.
CFD analysis of modular hypersonic Busemann inlets
SUN Bo, ZHANG Kun-yuan, WU Xiao-song
2009, 24(3): 573-580.
Abstract PDF(1844KB) icon1569 icon441
Abstract:
Modular streamtraced Busemann inlets were studied in detail for Mach 7.8 flight at 20 km altitude conditions.Numerical simulations were performed to study the effect of truncation angle and contraction ratio on the performance parameters of inlets,which were created by correcting the inviscid streamlines for turbulent boundary layer displacement obtained from finite difference calculations.To assess these inlets and calculate engine performance,they were coupled to an ideal combustor and nozzle.Mass-weighted average performance parameters of inlet/exit obtained by simulations were used as combustor entry flow conditions.The fuel used in the calculation is octane.The results show that mass capture ratio varies from 0.89 to 0.97 with truncation angles of 2°～10°.Larger truncation angle leads to higher mass capture ratio,pressure ratio and engine specific impulse.
Numerical simulation of the two-dimensional magneto-hydro-dynamic controlled inlet
ZHENG Xiao-mei, XU Da-jun, CAI Guo-biao
2009, 24(3): 581-587.
Abstract PDF(975KB) icon1524 icon482
Abstract:
The numerical simulation of flows in magneto-hydro-dynamic(MHD) controlled inlet at flight Mach number larger than the design value was performed.The shocks could be moved back to the design point,and the outlet Mach number was decreased.Influence of load factor on the performance of MHD controlled inlet was analyzed.The role of the Hall Effect on MHD channel was investigated.The results show that continuous electrode Hall Effect causes serious performance deterioration,segmented electrode will efficiently reduce the adverse impact of Hall effect.
Surge experimentation research for a whole turbine-shaft engine
KUANG Gui-lan, YAO Zheng-rong, WANG Dao-bo, Wu Zhi-yong, Peng Wen-wen
2009, 24(3): 588-595.
Abstract PDF(1521KB) icon1773 icon500
Abstract:
For the requirement of a turbine-shaft engine research,surge experimentation had been done exploringly in a whole engine test-bed.This paper describes engine surge,the design of surge experimentation method,experimentation equipment and the process of the experimentation.In the end,the results of the experimentation have been analysed and summarized,the results make clear that the experimentation method is valid,connecting high pressure air to the engine bleeds can do the engine surge experimentation successfully.Consequently the real surge margin of the compressor installed in the overall engine can be gotten.
Numerical simulation of plasma-based separation control over a hump
LIU Hua-ping, YAN Pei-gang, CHEN Fu
2009, 24(3): 596-601.
Abstract PDF(1651KB) icon1857 icon496
Abstract:
Using the simplified model of plasma generator,this paper solved electric equation to obtain the electric field and the plasma distribution,and then coupled the electrical force on the ions to flow equation.The results indicate that the electrical field could induce air flowing nearby the electrode interface and generate "wall surface jet flow" effect,increasing the fluid momentum and greatly improving the velocity in the boundary layer.Compared with the flow without plasma,the separation point was deferred about 4% chord,the attachment point was moved up approximately 12% chord,thus the separation scope was reduced obviously.In addition,increasing the voltage and exposing electrode to the surrounding air can enhance the plasma control ability.
Visualize framework for aero-engine performance simulation
WANG Bo, TANG Hai-long, ZHONG Ru-hao, CHEN Min
2009, 24(3): 602-607.
Abstract PDF(1098KB) icon1688 icon515
Abstract:
A graphical framework,which is object-oriented,visualized and expanded in Microsoft Windows environment,was introduced in this paper.In this framework program,the user could click engine components graphically shown in the component library,and drag them to the working space to form any kind of aircraft engine intended for simulation.The present framework covers steady and transient state performance calculation functions.The performance calculation of some sample aircraft engines confirms the correctness of the logic in this program and the practicability of the graphical user interface.
Investigation of the effect of wake impact effect on vortex sheets of the downstream blade row in axial compressor
ZHOU Xiao-bo, ZHOU Sheng
2009, 24(3): 608-614.
Abstract PDF(980KB) icon1577 icon434
Abstract:
The flowfield in axial compressor is characterized by unsteady vortex flow due to the relative motion of the blade rows.The upstream unsteady wake flow changing periodically is responsible for the airfoil aerodynamic efficiency and thus for the overall performance of the aeroengine.This paper examines the influence of such unsteadiness of upstream wake impact on the development of vortex sheets of downstream blades in a highly loaded HPC(High pressure compressor).The results of this study indicate that the temporal-spatial structure of wake impact effect in multistage turbomachinery flowfield could be more deeply understood when the unsteady processes are considered through the interaction of respective vortex sheets.The results suggest that the performance change is corresponding with temporal-spatial structure of the flowfield.The vortex sheets interaction of upstream weak and downstream blades might reduce the loss.It is the frequency of the vortex shedding alternately at the trailing edge that couple with the upstream weak passing frequency,instead of the frequency of leading edge separated vortex instability.
Numerical optimization of compressor blade profile based on the control theory
DU Lei, NING Fang-fei
2009, 24(3): 615-625.
Abstract PDF(1406KB) icon1564 icon438
Abstract:
An aerodynamic optimization method based on the control theory has been applied to the axial compressor 2-D blade profile design.The correspondent adjoint equations on the basis of Euler equations and the relevant boundary conditions were deduced in detail.The solving method for the adjoint equations was also proposed.The procedure to conduct an optimized design of a compressor 2-D blade profile could be divided into three steps.First,the required surface pressure distribution is pre-specified and set as the objective function.Second,the parameterized blade profile is seen as a set of the design variables,and the gradients of objective function to the design variables can be calculated by solving the adjoint equations.Third,a new blade profile is obtained by using the BFGS optimization algorithm,and this process is repeated until a converged profile is obtained.The proposed method has been validated by three illustrations.
Design and core and bypass numerical simulation of acompound swept fan
DING Jian-guo, HU Jun, CAI Xian-xin
2009, 24(3): 626-633.
Abstract PDF(1229KB) icon1524 icon464
Abstract:
An arbitrary airfoils blade design procedure was adopted to redesign a transonic fan with compound swept.by adjusting the distribution of crucial design parameters in the process of redesign,the loss of shock was depressed,the conflict of the high relative Mach number and low loss/high efficiency was overcome.Numerical simulation core and bypass indicate that,the efficiency of design point falls little,but the efficiency of take off point improves significantly,and the matching of core and bypass of the fan and booster is also promoted efficiently.
Optimal design of the axial-flow fan in the aeronautic electronic devices
ZHOU Jian-hui, YANG Chun-xin
2009, 24(3): 634-642.
Abstract PDF(1765KB) icon1626 icon506
Abstract:
Based on the procedure of the parametric design and numerical simulation of the fan,investigations were made in detail on the effect of various design parameters on the aerodynamic performance of the fan,which can provide deep understanding for the optimization of the fan.The multi-parameter constrained optimization procedures based on the combination algorithms of design of experiments(DOE),response surface models(RSM),genetic algorithm(GA) and mixed integer optimization(MOST),were carried out on 8025 fan for maximizing the coefficient of flow rate over the operating range rather than at a single operating condition with parallel computational fluid dynamics(CFD).Results show that aerodynamic average performance of the optimal fan is increased by 14.5 % when compared to the initial fan.
Numerical simulation of full annuls of a transonic fan with distorted inlet
TAO Li-quan, SUN Peng, ZHONG Jing-jun
2009, 24(3): 643-651.
Abstract PDF(1908KB) icon1867 icon477
Abstract:
A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out.The pattern and causes of flow loss caused by pressure distortion in rotor and stator were analyzed in detail.It is found that the distorted flow influences the inlet velocity angle of rotor and stator so that the attack angles vary a lot along with circumferential direction.The flow field parameters in rotor are totally different at different radial and circumferential positions.In stator,inlet total pressure distortion induces large-scale vortex,which produces backflow and increases the loss.
Review on investigation of high cycle fatigue failures for the aero engine blade
HONG Jie, ZHANG Da-yi, CHEN Lu-lu
2009, 24(3): 652-661.
Abstract PDF(1772KB) icon1783 icon452
Abstract:
High cycle fatigue(HCF) of blades caused by forced vibration is an outstanding problem for turbo engines,so the domestic and foreign research progress on high cycle life of blades in recent years are overviewed,the research methods are summarized and suggestions on further researches are put forward.The important ways to develop prediction method of high cycle life on blades are described as follows.The numerical method to obtain the dynamical responses under aerodynamic forces must be perfected,and the probability design should be introduced into the evaluation of high cycle life of blades.Besides,it is necessary to establish the blade-disk model accurately and to improve the solving technology of fluid-solid interaction.
Mistuning identification of integrally bladed disk based on the modal reduced technique
WANG Shuai, WANG Jian-jun, LI Qi-han
2009, 24(3): 662-669.
Abstract PDF(1386KB) icon1561 icon448
Abstract:
A method of mistuning identification for integrally bladed disk has been presented in this paper.The analytical modes obtained by finite element model of tuned bladed disk and the measured modes of actual mistuned bladed disk were used as the basic information.The identification method is based on the subset of nominal modes(SNM) reduced technique,which greatly lowers the computational costs and the required information of the identification procedure.The submatrix method makes the definition of mistuning parameters more freely and adds the model modification function to this identification method.The measured data is filtered through the best probable eigenvectors technique,which effectively suppresses the influence of measurements noise and non-linearity on the identification procedure.Finally,numerical simulation of an industrial bladed disk was preformed to validate the effectiveness of the identification method.
Performance of damping-sleeve for vibration control in labyrinth air seals
ZENG Liang, LI Lin
2009, 24(3): 670-676.
Abstract PDF(1925KB) icon1623 icon441
Abstract:
The design of damping-sleeve for vibration control was based on the research of damping-ring for vibration control in labyrinth air seals.The dynamic response of labyrinth air seals with different damping-sleeve(thickness,contact area) and interference was analyzed by dynamic compliance method.The simulation results confirm the validity of the proposed model and method,and show that the damping-sleeve could reduce the amplitude of the labyrinth air seals notably.Best parameters of damping-sleeve are available,which lead to the best effect of vibration control.The vibration control of damping-sleeve differs from varied modal shapes of labyrinth air seals.
Theory error of cutting face gears with sphericity hob
ZHAO Ning, GUO Hui, FANG Zong-de, SHEN Yun-bo
2009, 24(3): 677-682.
Abstract PDF(1180KB) icon1889 icon488
Abstract:
A scheme for cutting face gears with a sphericity hob and reconstructive hobbing machine was proposed.The basic worm helicoid surface of sphericity hob was deduced,and the coordinate systems for cutting face gears were established.The error difference surface research indicates that theory surface error of the face gear using sphericity hob is very small.The forming error of hobbing is much less than that of slotting cutter.Tooth contact analysis(TCA)indicates that the contact path position and direction are consistent with the theory results,and the transmission errors curve with the new method is favorably parabolic.This research finds a new method for machining face gears,and expands the application scope for the sphericity hob.
Effects of non-Newtonian behavior of lubricants on the thermal elastohydrodynamic lubrication in heavily loaded point contacts
WANG Yan-shuang, DENG Si-er, YANG Hai-sheng, LI Yun-feng, WANG Heng-di
2009, 24(3): 683-689.
Abstract PDF(2201KB) icon2154 icon487
Abstract:
This paper used an approximate numerical solution to simulate the thermal elastohydrodynamic lubrication(EHL) for an aviation lubricating oil HKD-1 in a point contact under heavier load.The computed results for two different rheological models were compared and examined by the traction test.The results show that the non-Newtonian characteristic of the lubricant is more important for heavier load(p0>1 GPa) and has a significant effect on the temperature,shear stress and traction of the lubricant in EHL,but it has a small influence on the pressure distribution.The computation errors for the Newtonian model are very large.The values of temperature,shear stress and traction of the lubricant computed for the Evans-Johnson model are very close to the experimental values.As slide-to-roll ratio increases,the temperature rise in film is obvious but the pressure change is very small,only the second peak value of pressure distribution is reduced to some extent.
Experimental study of elastohydrodynamic lubrication films under cyclic intermittent entrainment
JIANG Pei-gang, CHEN Jian-jun, GENG Mei-xiang, GUO Feng
2009, 24(3): 690-697.
Abstract PDF(1292KB) icon1409 icon455
Abstract:
Elastohydrodynamic lubrication(EHL) films were measured by interferometry under conditions of cyclic intermittent lubricant entrainment,and three types of local film dimples were indentified.The first dimple is generated from intermittent stops of the bounding surfaces,and the pure rolling produces larger oil entrapment than pure sliding.The second film dimple is generated by the velocity oscillation in the start-up process,and the resultant crescent-shaped dimple moves through the Hertzian contact region at the entrainment speed.When pure disc sliding is employed,the boundary slippage may lead to the third dimple,which is near the inlet region and related to the speeds and the time interval between two stops.The observed phenomena can be explained by the squeeze effect,the entrainment effect and the wall slippage.
Numerical studies on natural circulation precooling loop of cryogenic liquid rocket engine
CHEN Er-feng, LI Yan-zhong, CHENG Xiang-hua
2009, 24(3): 698-704.
Abstract PDF(1452KB) icon1824 icon430
Abstract:
One set of one-dimensional unsteady homogenous mathematic models for flow and heat process of natural circulation precooling loop of cryogenic liquid rocket engine was established,whilst both inverted annular model and dispersed model were introduced for the prediction of filming boiling region.The results indicate the unstable characteristics of circulation flow rate in precooling process is caused by the unstable characteristics of natural circulation driving force,that is,the heat flux transferred to the cryogenic liquid from the natural circulation precooling loop.Moreover,about 80% of wall temperature drop takes place in filming boiling region,and the inverted temperature distribution law of the return pipe is well interpreted by introducing the two filming boiling models mentioned above.
Calculation method of microwave attenuation by exhaust plume of solid rocket motors
ZHANG Shuo, WEI Zhi-jun, WANG Ning-fei, ZHANG Ping
2009, 24(3): 705-710.
Abstract PDF(1912KB) icon2085 icon458
Abstract:
The attenuation mechanism of microwave was investigated according to the standard Maxwell equations of exhaust plume plasma.With a reference to the Shukla charging equation of particle components,the prediction method of microwave attenuation by weakly ionized exhaust plume plasma was presented.Radio frequency attenuation calculation(RFAC) software was designed and used to calculate the rules of complex conductivity and microwave attenuation constant that are influenced by some special exhaust plume field parameters.The RFAC and ThermoCalc propellant thermo evaluation system was used comprehensively to calculate the microwave attenuation by nozzle exhaust plume field that comes from two different kinds of propellant.The calculation consequences are in well agreement with the experimental results in citation.
Numerical simulation of cold swirl flow field for solid fuel ramjet
LIU Wei, YANG Tao
2009, 24(3): 711-716.
Abstract PDF(1198KB) icon1663 icon439
Abstract:
In order to study the swirl flow characteristics in the solid fuel ramjet combustor,a new type of inclined multihole swirler was designed,and the analytical formula of swirl number was deduced.The cold swirl flow field in the combustor was numerically simulated with different angles of the holes and different back pressures,while the swirl flow field structure and the total pressure recovery coefficient were studied.The relative error of the swirl number at the swirler outlet of the analytical formula was small as compared to the numerical results,thus meeting the engineering need.The swirl number at the dump combustor inlet can be changed by different angles of the holes and different back pressures.The central torroidial recirculation zone and the recirculation zone after the step of the dump combustor account for biggest total pressure loss.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.