2009 Vol. 24, No. 11

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Instabilities of boundary layers along a tilt plate dissipating uniform heat flux
TAO Jian-jun, XIONG Xiang-ming
2009, 24(11): 2397-2402.
Abstract PDF(935KB) icon1916 icon548
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The stabilities of natural convection boundary layers along a tilt uniform-heat-flux plate were studied theoretically and numerically.For some Prandtl numbers,three-dimensional instability may have two critical modes,whose critical frequencies are close to the internal wave frequency and the value of two-dimensional T-S(Tolmien-Schlichting) wave,respectively.Specially,at proper tilt angles the three-dimensional wave mode is more unstable than the two-dimensional T-S wave.This result that seems contradict with the Squire Theorem is caused by the additional buoyancy terms in the governing equations.Direct numerical simulations confirmed the critical properties of the three-dimensional waves.Since hydrodynamic instability always exists at the first stage of turbulence transition process,current results may provide theoretical basis for optimal design of fins with high heat transfer efficiency.
Influence of inlet dynamic total pressure flow field on gas-turbine engine stability margin
LI Xiao-tang, WANG Qin, XUE Xiu-sheng, WANG Liang, XING Zhi-guo, WANG Hong-xiang
2009, 24(11): 2403-2409.
Abstract PDF(1195KB) icon1642 icon450
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Gas-turbine inlet dynamic total pressure flow field was measured to analyze the reason of surges happened during previous engine tests.Inlet flow field characteristics were obtained such as larger eddy scale and higher instant pressure distortion and pressure fluctuation associated with rotor speed base frequency which caused by the resonance of the engine and the inlet scroll case etc.Experimental data and information show that inlet dynamic flow field characteristics of the above-mentioned will make the engine increase the loss of stability margin and result in the engine surge.
Microturbo engine development and key technology analysis
SU San-mai, ZHANG Lei, CAI Yuan-hu, TU Qiu-ye
2009, 24(11): 2410-2414.
Abstract PDF(715KB) icon1891 icon693
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As powerplant of unmanned aerial vehicales(UAV) and cruise missile,microturbo engine has been developing quickly in recent years.In this paper,worldwide typical series microturbo engines with thrust below 4 000 N were summarized,covering the engine development background,structure,performance parameter and equipment/weapon object,etc.The newest developed TJ100 and AT-1 500 series of turbojets with thrust weight ratio over 10 were specially introduced.Based on above,common characteristics of this type of engine were discussed,and finally,seven key technologies during engine design,testing and manufacturing were proposed and analyzed by integrating real project engineering experience.
Swallowing water capability experiment of one turbine-shaft overall aviation engine
KUANG Gui-lan, WANG Dao-bo, SHAN Xiao-ming, WU Zhi-yong, WEI Hai-long
2009, 24(11): 2415-2420.
Abstract PDF(811KB) icon1624 icon468
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Waterworks and special air intake path were designed to conduct swallowing water experiments for one aviation turbine-shaft engine under research,while big and small rings were used to spurt certain quantity of water into the engine.The experiments were conducted at swallowing water in the quantity of 2.5% and 3.5% of engine's intake air.The results show that,the designs of the experiment method and device are feasible;when symmetrically swallowing water not higher than 3.5% of engine's intake air,the temperature drop at each engine's section decreases from the inlet to the exit;the engine's performance degrades after swallowing water experiments.
Predicting method for the performance of constant area isolator under back pressure
YUAN Hua-cheng, LIANG De-wang, GUO Rong-wei, LI Bo
2009, 24(11): 2421-2428.
Abstract PDF(1080KB) icon1767 icon488
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The flow filed in the isolator of a typical hypersonic inlet was simulated with uniform and non-uniform(with oblique shock) inflow.The pressure-temperature-Mach number at isolator exit relationship was investigated,the relationship of each other was presented,and all of those were independent of the isolator length.The predicting methods of the performance for constant area isolator under back pressure were studied,and doable predicting method of isolator under back pressure was presented.The concept of maximum pressure capability was developed when the back pressure was greater than the maximum pressure capability with unstarting of inlet.It's observed that the maximum pressure capability has relationship with the Mach number of the isolator exit with no back pressure.The predicting methods of maximum pressure capability for constant area isolator were presented.The maximum pressure-isolator length relationship was also presented.
Investigation of flow characteristic and performance on the "Jaws" hypersonic inlet
DONG Hao, WANG Cheng-peng, CHENG Ke-ming
2009, 24(11): 2429-2435.
Abstract PDF(1018KB) icon1659 icon427
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Two different inward turning inlets,i.e.a classic rectangular cross-section and a "Jaws" one,were explored numerically.Based on a three dimensional flowfield with four planar shock waves,these two were derived with the technology of streamtracing.Results indicate: the performance of the "Jaws" inward inlet is insensitive to the angles of attack on design point;the inlet has high mass capture and compression capability on off-design point;in addition,boundary-layer growth of the inlet develops slowly and shock/boundary-layer interaction is weak because of the diminished wetted area.In conclusion,this "Jaws" inward inlet is an advantageous option of the hypersonic inlet.
Experiment on the induced airflow acceleration by plasma aerodynamic actuation
ZHAO Xiao-hu, LI Ying-hong, LI Yi-wen, WU Yun, MA Qing-yuan
2009, 24(11): 2436-2442.
Abstract PDF(1465KB) icon1796 icon475
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To show the basic mechanism and the influential factors of induced airflow acceleration by plasma aerodynamic actuation,the induced airflow velocities were measured when the ambient air was still.The experimental conclusion shows that once the instant plasma aerodynamic actuation is started,a start-up vortex appears,and then moves behind and finally evolves into jet stream close to the actuator surface;the induced airflow velocities and the range of the jet stream increase when the actuation voltage rises;the induced airflow velocity variation is not obvious when the actuation frequency rises;the airflow velocities induced by plasma actuator with more pairs of electrodes increase firstly and then decrease periodically,and the impact of induced airflow acceleration weakens gradually as the stream-wise location rises.
Numerical simulation of weakly ionized gas hypersonic flow under uniform magnetic field
HUANG Fu-lai, HUANG Hu-lin
2009, 24(11): 2443-2451.
Abstract PDF(2656KB) icon2055 icon470
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Seven-species air model was used and electrical conductivity was calculated by species formula to investigate the effects of the intensity of uniform magnetic field on three dimensional chemical nonequilibrium hypersonic flows around a blunt body by solving the viscous MHD(magneto-hydro-dynamics) equations.The results show that the shock standoff distance is increased and total drag coefficient and wall temperature are reduced with increasing external magnetic field.At By=0.03 T,the shock standoff distance is increased by about 7%,total drag coefficient and local wall temperature in nonequilibrium flow are decreased by about 5% and 74%,respectively.However,in frozen flow under the same conditions,the shock standoff distance is increased by about 43%,total drag coefficient and local wall temperature are decreased by about 6.9% and 18%,respectively,as compared with that without magnetic field.
Study on the reliability of a single-sweep space marching algorithm for hypersonic flows
YANG Pan, CHEN Bing, XU Xu
2009, 24(11): 2452-2458.
Abstract PDF(1158KB) icon1592 icon467
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The accuracy of a single-sweep parabolized Navier-Stokes(SSPNS) algorithm for aeroforce and aeroheating prediction in hypersonic flow fields has been tested through three typical cases.The results suggest: 1) It is feasible for the SSPNS algorithm to predict hypersonic laminar compression corner flows with wedge angle smaller than 15°,when there is no obvious streamwise flow separation.2) According to the numerical results of cone flows(biggest attack angle 24°),the simulation of transverse separations with the SSPNS algorithm are reliable.3) For the flows over a two-dimensional wing with attack angle smaller than 12°,the accuracy of the SSPNS algorithm corresponds to that of time-iterative algorithm.4) As compared to the traditional time-iterative full Navier-Stokes,the SSPNS algorithm's computational speed is faster by 1～2 order of magnitude and presents a considerable storage saving.
Rotor-wing interaction analysis of a compound helicopter in forward flight
WAN Jia, CHEN Ming
2009, 24(11): 2459-2464.
Abstract PDF(710KB) icon1882 icon487
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The compound helicopter has gained more and more attention so far since there is an efficient way to improve the performance of such helicopter.By employing the free-wake arithmetic and vortex lattice method(VLM),a program for the rotor-wing system of compound helicopter aerodynamic computation has been developed.With this program,interactions between the rotor and the wing in different advance ratios were computed.Some conclusions can be made from the computation results: for the compound helicopter described in the paper,the influence of wing on the rotor lift is small,but a little bigger on the rotor torque;with the increase of the flight speed,the influence of rotor on the wing decreases;and the interaction reduces the efficiency of both the rotor and the wing.
Preliminary analysis of thermodynamic cycle of an intercooled recuperated turbofan engine
CAO Meng-yuan, TANG Hai-long, CHEN Min
2009, 24(11): 2465-2470.
Abstract PDF(2015KB) icon2115 icon547
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Intercooled recuperated aero-engine(IRA) is built based on conventional engine while intercooled and recuperated cycles are incorporated.It can utilize effectively engine's heat,improve the thermal efficiency and reduce the specific fuel consumption.The intercooled recuperated aero engine presents a new concept about "green" engine.On the MATLAB platform,an overall performance simulation model has been developed on the intercooled recuperated tri-spool turbofan engine with split exhaust.Then,performance simulation and thermal cycle analysis was carried out under this model.The result indicates that,with the same thermal cycle parameters and specific thrust,the specific fuel consumption of the IRA is less than that of the conventional turbofan engine.
Effects of car models proportion and wind tunnel cross section on aerodynamic characteristics of car
XU Xiao-ming, ZHAO You-qun
2009, 24(11): 2471-2475.
Abstract PDF(565KB) icon1592 icon480
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In consideration of the flow field characteristics of car aerodynamics,three-dimensional incompressible Navier-Stokes equations and RNG k-ε(renormalization group k-ε)model were used in simulation.Second-order upwind difference scheme was applied to obtain the physical quantities of control pedal,and SIMPLEC method was adapted for iteration.Different car model proportions and wind tunnel cross sections were simulated,the effects of car models proportion and wind tunnel cross section on aerodynamic characteristics of car were analyzed.The results show that: in a certain range of car models proportion,aerodynamic parameters of car changes gently;the simulation results of different car model proportions in three typical wind tunnel models vary greatly.
Experimental investigation of mixing characteristics of jet from circle-rectangular transition nozzle
ZHANG Bo, JI Hong-hu, HUANG Wei, CAO Guang-zhou, YANG Hai
2009, 24(11): 2476-2482.
Abstract PDF(1007KB) icon1568 icon476
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In order to measure the flow field and mixing characteristics of the jet from rectangular nozzle,the single incline hot-wire was used in the experiments.The results show that,the strongest mixing appears radially near the interface of ambient gas and jet,and causes the maximum value of Renaults shear stress in the same position,while the turbulent intensity decreases radially.Reynolds shear stress decreases axially,while turbulent intensity increases a little,and then decreases axially.
Particle image velocimetry(PIV) measurements of the flow in a rotating cavity with a radial inflow
YU Xiao, LUO Xiang, XU Guo-qing, SUN Ji-ning
2009, 24(11): 2483-2488.
Abstract PDF(1240KB) icon1755 icon467
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Particle image velocimetry(PIV) was applied to a multifunctional rotating facility,the velocity distributions in the rotating cavity with a radial inflow of fluid had been measured in different working conditions.The experimental facility,experimental method and error analysis were introduced.The instantaneous and ensemble-average velocity fields in the rotating cavity had been discussed in this paper.And the results show PIV can be used to analyze the velocity field in a complex rotating cavity and the influence of non-dimensional mass flow-rate and rotating Reynolds number.At the same time,the light reflection control and the symmetrical and steady dispersion of tracer particles are the key factors of the PIV measurement.
Numerical simulation on flow and heat transfer in rotating channel with small spacing pin-fin arrays
ZHANG Li, ZHU Hui-ren, LIU Song-ling
2009, 24(11): 2489-2494.
Abstract PDF(863KB) icon1610 icon448
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Numerical simulation was conducted to study the rotational effects on flow and heat transfer in pin-fin rotating ducts.The pin-fin is low and the chord-wise pin spacing is small.Numerical results show that rotation influences the pressure distribution and chord-wise ejection mass flow rate.In pin-fin rotating duct,the pressure increases gradually in the radial direction due to the effect of centrifugal force.The chord-wise ejection mass flow rate becomes smaller near the entrance and becomes larger near the radial exit.Rotation also influences the wall heat transfer,and enhances the pin-fin endwall heat transfer slightly.The heat transfer on the leading side of the duct is slightly higher than that on the trailing side.
Three-dimensional conjugate heat transfer simulation for the surface temperature of wing hot-air anti-icing system
BU Xue-qin, LIN Gui-ping, YU Jia
2009, 24(11): 2495-2500.
Abstract PDF(918KB) icon1794 icon524
Abstract:
The conjugate heat transfer of a 3-D wing hot-air anti-icing system was studied and a method for calculation of the surface temperature was presented in this paper.The method employed the commercial software package FLUENT and its user-defined functions(UDFs) to integrate tightly the external heat flux,internal heat flux and the thermal conduction in the skin.The external convective heat transfer coefficient was computed using the boundary layer integrated method,and the internal hot air flow and heat transfer was modeled using FLUENT.The iteration for the sequential coupling of internal,external and conductive heat transfer was implemented by automatically calculating the external heat flux and setting the heat flux boundary condition on the external surface with UDFs.This new method for a wing anti-icing system can be applied to verification of its feasibility and validity.
Analysis of the hydrogen combustion field in scramjet dual-cavity combustor
LIU Juan, PAN Yu, LIU Wei-dong, WANG Zhen-guo
2009, 24(11): 2501-2505.
Abstract PDF(1138KB) icon1687 icon487
Abstract:
In order to compare dual-cavity combustor with single-cavity combustor on enhancing the combustion,high-speed photography was employed to investigate hydrogen flame structure when fuel equivalence ratio is 0.07 in scramjet.The results show that,hydrogen flame is stable under small fuel equivalence ratio;the combustion region of upstream-cavity near the orifice is a triangular zone formed by the cavity and its shear layer,and another stable zone is beside the downstream wall,while there is no obvious flame around the injection exit;under the same incoming situation,the wall pressure of single cavity combustor is lower than that of combustors with cavities in parallel and cavities in tandem;and the recirculation zone with slow velocity and high pressure between cavities in tandem is good for the process of combustion;for cavities in tandem,the nearer the cavities' distance is,the higher the wall pressure and more concentrated the heat released from combustion is.
Experimental study the effect of flare sleeve length on the flowfield and spray characterization of a combustor swirl cup
YU Jin-feng, GUO Zhi-hui, ZHANG Jun-feng, SHANG Shou-tang
2009, 24(11): 2506-2513.
Abstract PDF(1702KB) icon1375 icon518
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The two-phase flow field of combustor dome with double swirlers,venturi and flare sleeve was studied experimentally using two-dimensional particle dynamics analyzer(PDA).The velocities,diameter,volume flux of droplets were measured,while the effects of the flare sleeve length on the flow field and atomization were analyzed.The flowfield downstream created by flare sleeves with different lengths is of the same structure,which includes central recirculation zone and corner recirculation zone.The flare sleeve length controls the development of flow field and affects the attachment point of the flow,which moves downstream with the increase of the length.The size of the recirculation zone is biggest when the flare sleeve length reaches a critical value.The Sauter mean diameters(SMD) produced by the shortest flare sleeve are smallest in the recirculation zone,showing good atomization.The atomization improves outside the recirculation zone with the increase of the flare sleeve length.The spray cone angle decreases with the increase of the flare sleeve length.The selection of the optimum sleeve length depends on the needs of combustion performances.
Evaluation of elastic properties of 3-D 4-direction braided composites
WEN Wei-dong, SHAO Jiang, CUI Hai-tao, XU Ying
2009, 24(11): 2514-2520.
Abstract PDF(893KB) icon1754 icon443
Abstract:
An improved three-cell model,which includes interior cells,two kinds of surface cells and corner cells,was proposed based on the geometrical characteristic of the yarns for 3-D 4-directional braided composite.The variation of characteristics for the yarns in the cells was considered in the present model.The average yarn packing factor was proposed to distinguish the different cross-sectional variations of the yarns in different cells.Based on this model,the stiffness prediction model was established with the method of stiffness averaging.By comparing with the available experimental data,it shows the applicability of the present model.At last,the influence of the braiding angle and the fiber volume fraction is discussed.
Damping ratio experiment study on rotary blade based on distributing excitation unloaded instantaneously
CHEN Mo-li, LI Shun-ming
2009, 24(11): 2521-2526.
Abstract PDF(639KB) icon1462 icon463
Abstract:
For the difficulty of estimating damping ratios in the dynamic design of aeronautics engine compressor blade,a response model of rotary blade under distributing excitation was established,and a nonattached damping ratios testing method with distributing excitation unloaded instantaneously(DEUI) was developed on the basis of this model.The former eight resonance damping ratios were tested with DEUI as well as with half-power method and modal analysis method,while the correlations of their experimental results were analyzed.It shows that the correlations between DEUI and the other two methods are more than 75%,and without interferences of frequency resolution and power spectrum analysis error,DEUI is more accurate.
Research on system reliability growth assessment model
HAN Qing-tian, LU Hong-yi, ZHANG Yi
2009, 24(11): 2527-2531.
Abstract PDF(531KB) icon1444 icon485
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According to the variation rule of failure intensity of repairable systems,and with a view of the influence of inter-failure time,a generalized reliability growth(GRG) model was developed,and the property was analyzed from different parameter values.Additionally,the trend test was also presented.Secondly,maximum likelihood estimation of the parameters was given under time censored and failure censored test.The Simpson rule was used to change the integral formula into the function of sum.The goodness-of-fit test and reliability growth assessment method were presented.Finally,a group of test data of some turbofan engines were analyzed.The result shows that the data is good fitted by the GRG model,and the assessment of the reliability growth is suitable to the engineering applications.
Response surface method of reliability sensitivity analysis for accessory gearbox outlet temperature
SHI Yan-yan, SUN Zhi-li, LI Guo-quan, GUO Mei, YAN Ming
2009, 24(11): 2532-2537.
Abstract PDF(516KB) icon1772 icon466
Abstract:
To resolve the reliability sensitivity analysis problems of unknown limit state function,a reliability sensitivity analysis method that uses response surface method(RSM) to get the ultimate state function for reliability sensitivity analysis was proposed,and the correlative formulas were deduced.The randomness of the flux and temperature of the lubricant at accessory gearbox inlet,and that of the temperature and velocity of the airflow outside accessory gearbox were considered;and the reliability of accessory gearbox outlet temperature and the reliability sensitivity of various random variables were calculated by the method of this paper.The result is consistent to references,showing that the method of reliability sensitivity analysis and the correlative formulas are correct and efficient.The method provides quantitative theoretical warranties for the reliability design and optimization of correlative accessories and accessory gearbox itself.
Optimization of momentum-biased wheel rotor based on its static and dynamic properties
SUN Xiao-juan, LIU Bo, JIA Hong-guang
2009, 24(11): 2538-2544.
Abstract PDF(837KB) icon1444 icon434
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Mathematical models of structural optimization were established for a momentum-biased wheel rotor,by integrally considering its static and dynamic properties,while the structural optimization designs were carried out.The wheel's maximum rotation speed is 7000 r/min and maximum angular momentum is 3N·m·s.Three-dimensional static and dynamic solid topology optimizations on the wheel rotor were performed based on artificial material density method;then a conceptual model,which tends to be a model with 4 I-beam spokes,was gotten.Simultaneously,a rotor with 4 rectangular spokes was designed in contrast with the I-beam spoke rotor.Finally,parameter models were established in software ANSYS,and sizing optimization design was performed based on the zero-order method.The optimized results show that the volume of each rotor declines to 1.51×10-4 m3,and that the first elastic vibration frequency(1468.0 Hz) of the rotor with I-beam spokes is higher than that(1 413.5 Hz) of the rectangular spoke rotor,proving that the result of topology optimization is reasonable.The optimized results in this article are realizable in engineering.And the study method provides a reference to decreasing design mass and lowering rotor's vibrant level,etc.
Response of two-disk rotor with squeeze film dampers and its variation with parameters
WANG Hong-jin, QIN Wei-yang, YANG Shu-lin, DENG Wang-qun
2009, 24(11): 2545-2550.
Abstract PDF(1108KB) icon1787 icon438
Abstract:
This paper investigated the variation of dynamical response of a low pressure rotor in turboshaft engine with its system parameters.Based on the model of low pressure rotor,a dynamical simplified model of two-disk rotor with squeeze film damper at each end was built.Its motion equations were derived.The numerical method was applied to solve the 12-dimensions differential equations.The influence of some parameters,e.g.,rotating speed,eccentricity and its phase angle,mass ratio of two disks,were analyzed.From simulation results,it can be seen that when phase difference of two disks' eccentricity is π,the two disks have their minimum vibration amplitude respectively.When their phase is identical,their vibration responses reach maximum values.The larger the mass of mid-span disk is,the larger the vibrations of two disks are.When mass of mid-span is lesser than that of overhung rotor,the response of system will decrease.
Method for analyzing flow losses in turobmachinery by using the measured results of stereoscopic particle image velocimetry
LIU Bao-jie, YU Xian-jun, JIANG Hao-kang
2009, 24(11): 2551-2557.
Abstract PDF(2409KB) icon1526 icon450
Abstract:
A method to calculate the entropy production rate based on the measured velocity flow fields was established based on the similar processes between stereoscopic particle image velocimetry(SPIV)measurement and large eddy simulation(LES).Comparing the turbulence dissipation rate estimated by several typical subgrid-scale(SGS) stress models,it can be found that the result calculated by the mixing model is most reasonable;however,the coefficients CSm and CAm should be well determined.Using the mixing model the entropy production rate of the complex flow fields near the rotor tip region measured by SPIV were analyzed.The results show that at the design condition the losses are mainly caused by the tip leakage vortex,while at the near-stall condition both the tip leakage vortex and the corner vortex can bring large flow losses.
Method of optimization of a stator vane setting in multistage axial-flow compressors
WU Hu, SUN Na
2009, 24(11): 2558-2563.
Abstract PDF(494KB) icon1643 icon452
Abstract:
Appropriate loss and deviation models for transonic axial compressors were selected from detailed investigation.By combining them with the blade row-by-blade row model,a quasi-one dimensional approach for calculating off-design performance of multi-stage axial compressors was developed.This approach was then combined with complex adjusting optimization algorithm.A new method was thus established for enlarging surge margin in multistage compressors using variable stator stagger setting.The methodology had been incorporated into computer program and validated using data from an eight-stage transonic axial compressor.Results have demonstrated that variable stator stagger setting is a powerful method to rematch stages and can be used to enlarge aerodynamic stability range of multi-stage compressors.Numerical results also show the effects of reflection coefficient α in complex adjusting optimization algorithm on optimizing results are apparent and α=1.15 seems best.
Effect of bowed and swept rotors on the unsteady efficiency fluctuation of a transonic compressor
MAO Ming-ming, SONG Yan-ping, WANG Zhong-qi
2009, 24(11): 2564-2569.
Abstract PDF(1112KB) icon1782 icon449
Abstract:
The unsteady 3-D flow fields in a transonic compressor at design point were simulated numerically to study the effects of the swept and bowed rotors on the stage efficiency fluctuation.The results show that,as compared to the baseline,the time-averaged efficiency of the compressor with bowed and swept rotors is increased remarkably,and the amplitude of the efficiency fluctuation is obviously reduced.And the phases of the stage efficiency fluctuation waves in time are shifted.The bowed and swept rotors reduce the separation loss of hub and tip region and also lower the efficiency fluctutiaon amplitude thereto.
Two-dimensional compressible model for compressor instability analysis
WANG Zhi-qiang, ZHANG Huan, HU Jun, TU Bao-feng
2009, 24(11): 2570-2576.
Abstract PDF(2078KB) icon1810 icon479
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Based on Moore-Greitzer model,a nonlinear multi "actuator disk" model was proposed to analyze the dynamic behavior of aerodynamic instabilities in high speed multistage axial compressors for both cases with and without rotating inlet distortion.The model described the duct flow fields using two dimensional,compressible and unsteady Euler equations,and accounted for the influences of downstream plenum and throttle in the system as well.It replaced each blade row of compressors with a disk.The main purpose of this work is to predict the mechanism of two-dimensional short wavelength rotating stall inception,the interaction between blade rows in high speed multistage compressors,and the influence of rotating speed of inlet total pressure distortion on the onset of flow instability.Some qualitative comparisons with available experimental results were made in this paper,showing that the model and results are reliable.
A design method of mixed flow fan for helicopters
LI Ming, GAO Hong-xia, YU Jian-zu, CHANG Li
2009, 24(11): 2577-2583.
Abstract PDF(1281KB) icon2045 icon437
Abstract:
The excellent design of mixed flow fan is a key to the performance of oil cooling system of helicopter.Based on quasi-three dimensional flow theory and related design ideas,the principle of configuration optimization and pressurization design was provided for the mixed flow fan,which has characteristics of small size,high rotating speed and high pressure.Then,the radial balance equations and the constraint conditions were employed to calculate the meridional velocity.And finally the aerodynamic data were calculated and the geometry of fan was built based on the aerodynamic fundamental equation and the free vortex theory.Compared with axial flow and centrifugal fan,the design results show that the mixed flow fan has the advantages of high efficiency,high static pressure and power saving under the same work condition of lubrication cooling system of helicopter.
Design and tests of jet fuel starter-assisted airstarts for turbofan engines
ZHANG Shao-ji, BING Lian-xi
2009, 24(11): 2584-2588.
Abstract PDF(617KB) icon1756 icon465
Abstract:
The design and tests of a jet fuel starter-assisted airstart scheme were conducted for a turbofan engine.The methods of ground-rig tests,air-equipment tests and flight tests were performed,showing that the jet fuel starter-assisted airstart could enlarge the airstart envelop of a turbofan engine.The scheme using jet fuel starter-assisted airstart has improved the reliability of airstarts during engine flame out in the flight,thus guaranteeing the flight safety.
Critical technologies for aero-engine prognostics and health management systems development
JIANG Cai-hong, SUN Zhi-yan, WANG Xi
2009, 24(11): 2589-2594.
Abstract PDF(1120KB) icon2652 icon663
Abstract:
The definition,design objective and functions of engine prognostics and health management(EPHM) system were introduced in this paper.Along with the technical characteristics of EPHM systems of the fourth generation fighter engines,such as EJ200 and F119,the association scheme of a new EPHM system with its airplane and engine was discussed.The basic configurations of both on-line and off-line EPHM subsystems were further discussed.The technical specification of typical EPHM systems in modern advanced fighters was then presented.Critical technologies for aero engine prognostics and health management systems development were summarized.
Control law of turboshaft engine for helicopter autorotation training
HUANG Kai-ming, HUANG Jing-quan, ZHOU Wen-xiang, FENG Xing, HUANG Bo
2009, 24(11): 2595-2600.
Abstract PDF(762KB) icon1733 icon532
Abstract:
In order to deduce the engine control law during the helicopter autorotation,simulation was made to demonstrate the transient process of the engine when entering the helicopter autorotation condition using normal control law.Based on the existing control law,an improved law was brought forward by magnifying the differential gain of collective pitch "anticipator" and broadening the deceleration limitation.The simulation results show that the improved control law can satisfy the requirement of the helicopter,thus attaining an effective way for the control of the engine during the helicopter autorotation.
Improvement of Laval nozzle calculation model and simulative verification in aero-engine performance calculation
ZHOU Wen-xiang, HUANG Jin-quan, ZHOU Ren-zhi
2009, 24(11): 2601-2606.
Abstract PDF(551KB) icon2257 icon457
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By analyzing typical operating regimes of Laval nozzle,a zero-dimensional pneumatic model was built to evaluate the influence of Laval nozzle on the performance of aero-engine.The Laval nozzle model was integrated into a whole aero-engine component-level model.Numerical simulations were performed to study transient performance of aero-engine when nozzle throat and outlet areas decreased during accelerating process from idle to middle state.Results show that low pressure rotor speed decreases during some specific regimes,along with the reduction of Laval nozzle area in accelerating process,which also exists in real aero-engine rig tests.Besides,after normal shock clinging to nozzle outlet section was pushed out,there was a mach number break from subsonic to supersonic in nozzle outlet section,however,both the outflow rate and thrust changed smoothly without any break at the accelerating curve.
Three-variables robust controller design for aero-engine
WANG Qian-yu, SUN Jian-guo, LI Qiu-hong
2009, 24(11): 2607-2611.
Abstract PDF(809KB) icon1597 icon392
Abstract:
Three variables controller for aero-engine was studied in this paper.Given the fact that too many outputs of aero-engine could be used as controlled variables,and different controlled variables have varying performances,it is particularly important to get the suitable controlled variables.Here,the method of choosing best outputs as the controlled variables is RSCN(robust stability and condition number)method.Three output-variables were chosen from 14 outputs of aero-engine.After the selection of controlled variables was completed,an augmented LQR(linenr quadratic requlator) controller was designed.The simulation indicates that the controller with the chosen outputs gets very well dynamic and steady state performance.
Research on meshing characteristics-based design of point-contact tooth surface
ZHOU Kai-hong, TANG Jin-yuan, YAN Hong-zhi
2009, 24(11): 2612-2617.
Abstract PDF(2144KB) icon1405 icon458
Abstract:
For deficiency of the Gleason design technique for the spiral bevel gears,in which the meshing function is unable to be predesigned in whole tooth contact,a theory for the meshing characteristic-oriented design of point-contact tooth surface was presented.The geometry of the points on the path of contact was determined from the predesigned meshing characteristics,unrelated to any specific machine tool adjustment parameter.The second-order parameters of tooth flank were studied by load-deformation condition of elastic gears instead of the dimension,position and orientation of the contact ellipse.A numerical example was given to proved that above-mentioned design method is improvement and development of Gleason spiral bevel gears design method.
Design and analysis of loaded transmission errors for aviation spiral bevel gears
CAO Xue-mei, ZHANG Hua, FANG Zong-de
2009, 24(11): 2618-2624.
Abstract PDF(1342KB) icon1936 icon432
Abstract:
Loaded tooth contact analysis is an important technique for analyzing the meshing performances under load.The known algorithms can't be concerned with the tooth surface design directly because of a great deal of calculation,iteration or equations.A new simplified formulation was thus proposed based on application of the time varying stiffness.The transmission errors under loads were calculated by the developed formulation and finite element method,respectively.The results for the two methods were compared with respect to the magnitude,shape and 1st component of frequency spectrum of loaded transmission errors,and showed good agreement.The developed formulation was used to study the relationship of real contact ratio and load,the law of the loaded transmission errors versus real contact ratio,and the effect of contact pattern,transmission errors on loaded transmission errors.The analysis results provide the theoretical bases for the optimization strategy to tooth surface design of spiral bevel gear.The calculation of the loaded transmission errors is embedded to constitute the design route in the courses of the optimization.The design variables include contact path orientation and magnitude of transmission error;the objective of optimization is that the magnitude of the loaded transmission error fluctuates less under wide load ranges.
Modeling and load analysis of spiral bevel gears power split system
GU Jian-gong, FANG Zong-de, PANG Hui, WANG Cheng
2009, 24(11): 2625-2630.
Abstract PDF(1760KB) icon2035 icon441
Abstract:
According to different forms of gear power split transmission including parallel axes,star gear train and planetary gear train,a new type of spiral bevel gears power split system with cross axes transmission was proposed and its structure and working state was explained.The transmission powers of every gear pair in the system were then calculated,and the power split situations were analyzed under conditions of all kinds of installation errors.The results show that,in consideration of the installation errors in shaft angle of input gear and its opposite output gear or axial error of its adjacent output gear,the power transferred by main load gear pair of the system can be decreased,so the load capacity of the system is improved obviously,contributing to uniform load of the system.When every gear has different installation errors,the load situations are influenced by the error accumulation and opposition.
Investigation of ring aerodynamic throat for solid rocket motor
XIE Kan, LIU Yu, WANG Yi-bai
2009, 24(11): 2631-2636.
Abstract PDF(1566KB) icon2108 icon489
Abstract:
A ring aerodynamic throat concept of solid rocket motor controlled by secondary injection was simulated numerically.The influence and rules of secondary flow injection positions,injection angle,secondary flow rate and injector geometry parameters on the performance of aerodynamic throat were studied.The flow field character of aerodynamic throat was attained by calculation,namely: the starting point of sonic line from the downstream of secondary injection outlet.And the scope of injection positions for the existence of aerodynamic throat character was also attained.The results show that,the performance of aerodynamic throat can be obviously increased by making secondary flow injector close to the throat,increasing secondary flow rate or decreasing secondary flow injection angle.

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