2010 Vol. 25, No. 4

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Film deflection measurements of a rotating film cooling model
DENG Hong-wu, MA Ming, LUO Xiang
2010, 25(4): 723-728.
Abstract PDF(1038KB) icon1534 icon480
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An experimental study was performed to investigate the deflection of film trajectory on a flat blade model under the rotating operating conditions.The moving trajectory of film was mainly governed by the inertial force and radial pressure gradient in the blade passage.A new dimensionless parameter Φ,which is related to the ratio of the above two forces to determine the radial deflective angle of the film trajectory,was demonstrated in the present study.The steady-state thermochromic liquid crystal(TLC) technique was employed for flow visualization,and all the signals from the rotating reference frame were collected and transmitted to the stationary receiver via a wireless launcher,which was fixed in the rotation laboratory bench.The experimental results demonstrate that the spanwise deflection of film trajectory decrease with the increase of Φ values.
Experimental study of cooling effectiveness of impingement/cocurrent convection/film cooling
YANG Wei-hua, WANG Mei-juan, DING You-hong, ZHANG Jing-zhou
2010, 25(4): 729-734.
Abstract PDF(1147KB) icon1602 icon492
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In order to study the heat transfer characteristics of impingement/cocurrent convection/film double cooling,several test pieces were designed.The experimental results show that the cooling efficiency increases with the growing blowing ratio;the distribution of cooling efficiency is wavy on the cooling wall.The cooling efficiency is higher in the areas of cooling film exit and the impingement stagnant point.The decrease of cooling efficiency is weakened behind the impingement stagnant point.Cooling efficiency increases with the decrease of impingement space.
Experiment on nitrogen-filling performance of fuel scrubbing ejector
LIU Xiao-fang, LIU Wei-hua, QIAN Guo-cheng, ZHAO Hong-tao
2010, 25(4): 735-740.
Abstract PDF(709KB) icon1726 icon417
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The experimental and theoretical analysis was implemented on the basis of fuel scrubbing orthogonal tests for reducing experiment times.Results show that the nitrogen-filling performance of the scrubbing ejector is influenced by important factors of area ratio m,lenth to diameter ratio L/D,and nozzle pressure p.But their significance is relative.A series of experience formulae and good values is found out.The scrubbing ejector designed and manufactured on these formulae and values not only ejects very small nitrogen-enriched microbubbles to improve scrubbing efficiency,but also satisfies the oxygen concentration of ullage throughout.
Comparison of external heat transfer codes for turbine blades
QING Xiong-jie, PAN Bing-hua, ZENG Jun
2010, 25(4): 741-747.
Abstract PDF(1248KB) icon1859 icon564
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The mathematical models of two external heat transfer(EHT) codes,STAN5 and S1ICH,were compared.Both codes were employed to calculate the EHT coefficients(EHTC) of two turbine blades,i.e.:Von Karman Institute(VKI) high-pressure turbine guide vane and blade,and the results were compared with experimental data.The results show that S1ICH has higher precision on capturing onset of transition and predicting EHTC of turbine blades than STAN5.S1ICH can meet the requirement of engineering applications,thanks to its character of extensive applicability,good convergence and simple input.
Numerical methods in simulation of annular combustor cold flow field
CAI Wen-xiang, ZHAO Jian-xing, HU Hao-sheng, WU Xiao-song
2010, 25(4): 748-753.
Abstract PDF(2814KB) icon1772 icon449
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Three-dimension turbulence flow field in an annular combustor with two-stage radial swirler was simulated to quantify the prediction accuracy of different turbulent models(standard k-ε model,RNG(renormalization group) k-ε model,algebraic stress model) and the calculation efficiency of different algorithms(SIMPLE(semi-implicit method for pressure-linked equations) and PISO(pressure implicit split-operator)) in the complex flow fields.Body-fitted grid of the flametube used in this study was generated by an elliptical grid generation technique combined with the anchored grid method,and the flow fields near the wall were treated by the standard wall function.Computational results show that,PISO algorithm can be used to obtain an obviously higher efficiency.Simulation results gained from different turbulence models are in agreement with the experimental data.Among these turbulence models,the algebraic stress model is likely to offer better prediction capability for complex turbulent flow field.
Numerical investigation on pressure wave propagation speed of gas-liquid two-phase flow in pump pipeline
CHEN Er-feng, LI Yan-zhong, YING Yuan-yuan
2010, 25(4): 754-760.
Abstract PDF(2480KB) icon2035 icon476
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With the thermal phase change model in computational fluid dynamics code ANSYS CFX,the mixing condensation process of gaseous oxygen and liquid oxygen in pump pipeline was numerically simulated.Moreover,the dispersion equation of two-phase pressure wave propagation was derived via the ensemble average two-fluid model,and was used to predict the pressure wave propagation speed in pump pipeline.The results indicate that,with the increase of void fraction,the two-phase pressure wave propagation speed in pump pipeline first decreases and then slightly increases in slug flow,and the propagation speed increases as angular frequency enlarges.When liquid oxygen mass flow rate increases or inlet gaseous oxygen temperature decreases,the condensation effect of gaseous oxygen in pump pipeline enhances and the average void faction along the flow direction decreases,thus producing large pressure wave propagation speed.
Numerical investigation of film cooling with anisotropic turbulence model
ZHU Jian-qin, XU Guo-qiang, SUN Ji-ning, DENG Hong-wu
2010, 25(4): 761-767.
Abstract PDF(1204KB) icon1579 icon441
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An in-house three-dimensional Navier-Stokes code was developed to evaluate numerically the advantages of the anisotropic turbulence model over the classical isotropic k-ε model in a typical film cooling experiment.The anisotropic turbulence model was the k-w turbulence model incorporated with anisotropic coefficient.The effects of the anisotropic turbulent transport coefficient on the flow and temperature filed were analyzed in detail.The applicability of this model was also discussed.Comparison result reveals that the introduction of the anisotropic turbulent transport coefficient intensified the turbulent mixing of cooling jet with the main stream in lateral direction,and subsequently enhanced the lateral spreading of cooling air.The cooling effectiveness in centerline predicted by the anisotropic model was much closer to experimental data than that by the standard k-ε model.The anisotropic model was in good agreement with the experimental results at low-mass flux ratio condition(M=0.5).However,with the increase of mass flux ratio,the jets tend to be detached and then reattached to the wall,the discrepancy upstream the reattachment increased due to the limitation of the anisotropic coefficient,and downstream the reattachment these two agreed well consistently.
Numerical analysis of subsonic high-temperature-gas thermal environment simulation
YAO Feng, DONG Su-jun, WANG Jun
2010, 25(4): 768-773.
Abstract PDF(1089KB) icon1703 icon478
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The article introduced an experimental method using subsonic high-temperature-gas flow to simulate aerodynamic thermal environment of near space hypersonic vehicle.In the test section of the experiment equipment,the subsonic high-temperature gas flow ejected the room temperature air to make the heat distribution of the experimental condition in line with that of the real flight condition on the surface of the cap.Twelve experimental conditions were analyzed using FLUENT.The numerical analysis shows the temperature of the stagnation will below that of the gas flow,the inject ratio change of the facility can make a wide temperature change in the back region of the nose cone,so the facility is efficient to simulate the aerothermal environment of the hypersonic vehicle in a certain accuracy.
Experimental investigation of spray characteristics of a double line pressure-swirl atomizer
CHEN Jun, JI Hong-hu, ZHANG Bao-cheng
2010, 25(4): 774-779.
Abstract PDF(1434KB) icon1541 icon494
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The atomization quality of a double line pressure-swirl atomizer for aero-engine was investigated using phase Doppler particle analyzer(PDPA).The spacial distributions of Sauter mean diameter(d32) and the angle of spray cone were obtained.The results show that: the droplet size decreases with the increase of fuel-supplying pressure,and tends to become invariable when the pressure rises to certain extent;the spray cone angle is basically independent from fuel-supplying pressure;d32 decreases with the widening distance from the spray nozzle,when the main or secondary fuel lines operates respectively;at the same measuring cross section,d32 slightly changes with the radial distance.
Experimental investigation of rotating single-hole film cooling performance on suction side of a turbine blade
LI Guo-qing, DENG Hong-wu, XIAO Jun
2010, 25(4): 780-785.
Abstract PDF(1339KB) icon1846 icon476
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Experimental investigations were carried out to study the rotating film cooling characteristics in a 1.5-stage turbine using stationary thermo liquid crystal method.The length of the test blade in chordwise and spanwise was 124.3 mm and 99 mm respectively with a 4 mm film hole in the middle span oriented 36° to the tangential of the suetion side in streamwise.The mainflow was compressed and heated to bring the turbine to rotate with an inlet Reynolds number Reg of 8×104.Air and CO2 acted as coolant to achieve the coolant to mainflow density ratio of 1.03 and 1.57,respectively.Three rotation numbers of 2.092,2.324 and 2.448 were considered.The blowing ratio varied from 0.3 to 3.0.Results show that on suction side there is an optimum blowing ratio to obtain the best film cooling effectiveness and coverage.Higher density ratio could generate larger film cooling coverage.Rotation is bad for film cooling effectiveness.Meanwhile,the film trajectory deflects centripetally a little due to the horseshoe vortex and rotating effect.
Investigation on heat transfer characteristics of spiculate lamilloy internal surfaces
ZHANG Bin, ZHU Hui-ren, XU Du-chun
2010, 25(4): 786-793.
Abstract PDF(1974KB) icon1475 icon434
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Experiment was carried out to analyze the heat transfer characteristics of the inner surfaces of a kind of lamilloy configuration by using narrow-band transient liquid crystal technique.In this research,the ratio of hole pitch to impingement hole diameter(S/D) is 3.2,4.5,5.9,and Reynolds numbers range from 10 000 to 40 000.This paper also compared with traditional lamilloy model to analyze the heat transfer mechanism.The result shows that: heat transfer coefficient of the surfaces increases when Re becomes greater,and gradually decreases when the holes pitch becomes wider.The mathematics fit formulas of the Nu with respect to Re and S/D has also been given.
Experimental study on outlet temperature distribution in single vortex/lean oil trapped vortex combustor
KONG Xiang-lei, FAN Wei-jun, XING Fei, ZHANG Rong-chun, SONG Xuan-jin
2010, 25(4): 794-799.
Abstract PDF(748KB) icon1480 icon423
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The influential factors of outlet temperature distribution in single vortex/lean oil trapped vortex combustor were studied experimentally.Some results were obtained by analyzing the experimental data:(1) Cavity gas amount has great effect on outlet temperature distribution.Outlet temperature distribution factor(OTDF) firstly increases and then decreases with the growing cavity gas amount.This is related with the penetration depth of mixing jet.(2) Fuel mixing temperature also has great effect on outlet temperature distribution.When the fuel mixing temperature is low,OTDF is low.Also,OTDF firstly increases and then decreases with the higher fuel temperature.(3) Fuel amount also has important effect on outlet temperature distribution.When fuel amount becomes larger,OTDF firstly increases and then decreases.
Simulation of supersonic gas-particle two-phase flow with two-fluid model
YU Yong, ZHANG Xia, CHEN Wei
2010, 25(4): 800-807.
Abstract PDF(1213KB) icon2007 icon462
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A two-fluid model was applied to simulate compressible two-phase flow in JPL(Jet Propulsion Laboratory) nozzle and supersonic jet two-phase flow.And,the interactional mechanism of gas phase and particle phase,rules of particles flowing at different sizes were studied.Program "Solve2D" solving two-dimensional axisymmetric compressible two-fluid model with body-fitted coordinate system was developed.The program was used to solve gas phase Navier-Stokes(N-S) equations with k-ε turbulence model.For particle phase,Euler equations were solved.Two phases were coupled through source terms.Gas-particle two-phase flow field of JPL nozzle and jet were studied under different particle mass percentages and different particle sizes.
Effects of throat asymmetry on micro nozzle's performance
TONG Jun-jie, XU Jin-liang, CEN Ji-wen
2010, 25(4): 808-815.
Abstract PDF(1585KB) icon1493 icon479
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FLUENT 6.1 software was applied to simulate the supersonic flow in micro convergent-divergent nozzle.The simulation was complemented by computing steady two-dimensional Navier-Stokes(N-S) equations to study the effects of flow fields and performance of thruster from throat structure asymmetry.The asymmetry of throat was caused by deviation of throat upper vertex from lower vertex in x direction.The simulation results show that the asymmetry of throat causes fluids perturbation inside thruster,mass flow rate increases,and x direction thrust force decreases while additional y direction thrust force is produced at the exit of thruster.
Reduction of rocket engine jet noise by water injection
XU Yue, ZHOU Xu, ZHANG Zhi-cheng, CHEN Yu, LIU Li-hong
2010, 25(4): 816-820.
Abstract PDF(1753KB) icon1817 icon441
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A finite volume method was applied to determine rocket jet noise reduction due to water injection.Mass,momentum and energy equations based on the control volume were built and solved,and the equivalent jet parameters due to mix of the jet and water were obtained.The effect of the water-to-jet mass flow rate ratio on equivalent jet parameters and noise reduction was analyzed.The calculation results show the agreement with experimental data.The results indicate that the efficiency of noise reduction reduces when the mass flow rate ratio exceeds the critical value.
Numerical study on mixing enhancement for supersonic mixing layer in dual combustor ramjet
YAN Zhi-hui, CHEN Ti, YU Jiang-fei, LIU Wei-dong
2010, 25(4): 821-828.
Abstract PDF(3019KB) icon1918 icon454
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Numerical simulations were carried out for a mixing enhancement measure-streamwise surge plus low velocity flow inlet-for specific supersonic mixing layer in dual combustor ramijet's(DCR's) supersonic combustor.The results show that,if streamwise surge is added at low velocity flow inlet,the positive impact on mixing enhancement is evident,and the burning intensity is increased,however it still belongs to weak combustion.The frequency determines the location and scale of vortices assembling region,and the swing determines uniform degree of distributed and assembled vortices.
Numerical simulation of shear dual-coaxial gas-gas injector
DU Zheng-gang, GAO Yu-shan, LI Mao, JIN Ping, CAI Guo-biao
2010, 25(4): 829-834.
Abstract PDF(1160KB) icon1609 icon483
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The turbulent Navier-Stokes equations in combination with two equation k-ε turbulence models were used to simulate the flow field of shear dual-coaxial single element GO2/GH2 injector chamber.The results show that: the shear dual-coaxial injector has two shear combustion surfaces,enabling to achieve a high combustion efficiency at the condition of large mass flowrate,the oxygen injection velocity and the velocity ratio of hydrogen to oxygen are key parameters for shear dual-coaxial injector design,a lower oxygen injection velocity makes the combustion location far away from the faceplate,while a higher velocity ratio makes the combustion location closer to the faceplate.Compared with the gas-liquid shear coaxial injector,a faster oxygen injection velocity and proper velocity ratio of hydrogen to oxygen are preferable choice for design of shear dual-coaxial injector.
Simulation and analysis on combustion performance of hydrogen-rich/oxygen-rich gas-gas coaxial injectors
LI Mao, DU Zheng-gang, JIN Ping, CAI Guo-biao
2010, 25(4): 835-840.
Abstract PDF(1200KB) icon1737 icon431
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In order to investigate the performance of the hydrogen-rich/oxygen-rich gas-gas injector in the full flow staged combustion(FFSC) engine,the combustion flow fields of the combustors with a shear coaxial injector,a coaxial injector for the oxidizer injector with expansion angle,a coaxial injector for the fuel injector with contraction angle,a coaxial injector for the oxidizer injector with a column in the center and a shear dual-coaxial injector were simulated.The propellant of the injectors was hydrogen-rich gas in temperature of 758 K and oxygen-rich gas in temperature of 676 K.The results of the numerical simulation show that,the shear dual-coaxial injector has the best combustion performance.The results can provide the reliable criterion for the design and experiment of hydrogen-rich/oxygen-rich gas-gas injector.
Experimental investigation on flowrate characteristics of gaseous hydrogen/gaseous oxygen injector
GAO Yu-shan, DU Zheng-gang, LI Mao, CAI Guo-biao
2010, 25(4): 841-846.
Abstract PDF(1116KB) icon1535 icon450
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Experimental investigation on flowrate characteristics of two different types of GH2/GO2 injectors at different back pressure conditions were used for hot fire test.The effect of the fuel injector on oxidizer injector and the effect of pressure drop on the flowrate characteristics were investigated.The results show that the discharge coefficient of oxidizer injector is bigger than the oxidizer working alone when the oxidizer injector and the fuel injector are simultaneously working,as the back pressure changed from 0.2 MPa to 4 MPa.The discharge coefficient of the oxidizer injector and the fuel injector becomes bigger with the increase of pressure drop,but the trend becomes slower.The results presented in this paper may provide valuable reference for the design and improvement of the gas-gas injector.
Full elastic steady-state micro flow measurement system
ZHANG Xin-ai, TANG Hai-bin, LI Xin, LIU Yu, WANG Hai-xing, SHI Chen-bo
2010, 25(4): 847-851.
Abstract PDF(925KB) icon1616 icon444
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The operating principle and process of a liquid micro flow measurement system using mass measurement method were presented in this paper.This micro flow measurement system was designed by elastic link method to prevent the measurement error caused by rigid pipeline.The pressure compensator in this system can improve the measurement accuracy by means of modifying the density variation caused by pressure.Five different flow rates of alcohol measurement experiments were conducted with this new micro flow measurement system.The results show that the full elastic steady mass measurement method for micro flow measurement system works steadily and reliably.It can measure the liquid micro flow rate accurately.
Dynamic response analysis of fluid-structure interaction in liquid-filled pipes of rocket feed system
WEI Xin, SUN Bing, YU Zi-wen, TANG Bo, ZHANG Qing-song
2010, 25(4): 852-856.
Abstract PDF(1648KB) icon1727 icon505
Abstract:
Considering the effect of fluid-structure interaction,the dynamic response study of liquid-filled pipes of rocket feed system was carried out in this paper.To set a model,the pipes were defined in a plane,which could vibrate axially and transversely under the influence by Poisson coupling and junction coupling.Numerical test on pipes between rocket tank and pump was then conducted.The reasonable results regarding frequencies and modes show the necessity of proposed model,as compared with the traditional water hammer model.This study could give a reference to the pipe test and further study on oscillation suppression.
Denoising method for aeronautical engine turbine blade X-ray industrial CT image
FU Jian, LI Bin, XIAO Ying-chun, JIANG Bai-hong
2010, 25(4): 857-860.
Abstract PDF(1415KB) icon1677 icon440
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The similarity between different regions in an X-ray industrial computed tomography(CT) image of aeronautical engine turbine blade has been analyzed.A method called non-local means algorithm based on the similarity has been discussed to improve the industrial CT image contrast.This method adopts the weighted-Gaussian Euclidean distance to calculate the similarity between different regions in an image.Then it averages the regions with the similarity.It can decrease the noise in industrial CT images and meanwhile reserve the edge sharpness.However this method has a high computational complexity.So an acceleration algorithm based on Fourier transform for the non-local means algorithm has been researched.The weighted-Gaussian Euclidean distance is also replaced by the Euclidean distance to improve the calculation efficiency.The experiment results show that,this algorithm can improve the speed at least four times without affecting the denoising effect.
Experimental investigation on endwall fences with different height in compressor cascade
TIAN Fu, ZHONG Jing-jun
2010, 25(4): 861-867.
Abstract PDF(1169KB) icon1857 icon397
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Through measurement of the compressor cascade flow field by using the five-hole probe in a low speed wind tunnel,the effect of the different height and circular locations endwall fences on the total cascade loss and secondary velocity vectors was investigated.The results show that,the optimal circular location of fences which decreases the total cascade loss is 70 percent of pitch far from the suction surface of the blade,the optimal height of fences is 5 mm;the height of fences which decreases the total cascade loss is not unlimited.The endwall fences vortices became distinct with the increasing height of fences.The distribution of the cascade endwall loss can be changed by fences,so the flow in the corner of the suction surface/endwall is controlled and the aerodynamic performance of the cascade is improved.
Precision analysis of the flow field measured in compressor rotor by using stereoscopic particle image velocimetry
ZHANG Zhi-bo, YU Xian-jun, LIU Bao-jie
2010, 25(4): 868-876.
Abstract PDF(3240KB) icon1697 icon381
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This paper discussed the uncertainty analysis method of some SPIV results measured inside the compressor rotor.The convergence characteristics of the SPIV results of the three velocity components,the first-order results(vorticity) and the second-order statistics(the Reynolds stress) were investigated,and the measurement accuracy was analyzed.Then,the analysis of the main influential factors to the measurement accuracy of high-order statistics was carried out.At last,some advices for improving the measurement accuracy of SPIV in turbomachinery were given.
Off-design performance study of axial flow fan in helicopter
LI Ming, GAO Hong-xia, YU Jian-zu, ZHOU Yi
2010, 25(4): 877-883.
Abstract PDF(1246KB) icon1949 icon389
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This paper analyzed inner flow of an axial flow fan in helicopter at different work conditions by the ways of theoretical analysis,numerical simulation and experiment.The results show that,theoretical hypothesis of relative velocity in the impeller is applicable for rated condition but not for surge condition.When the helicopter flies at high altitude and the fan works at low flow rate condition,backflow will appear firstly in blade tip region and the secondary flow loss increases;increment of helicopter flight altitude also causes separation of boundary layer and widening of jet-wake area,thus the fan efficiency further decreases;stalling will first appear in tip clearance area in the event of gathering of low speed flow.So it is important that research on off-design performance should be performed to optimize main aerodynamic parameters influential to fan loss,and also to improve the stability of altitude performance when designing axial flow fan for lubrication system of helicopter.
Numerical aero-optimization method for three-dimensional compressor rotor with parameterized aerodynamic variables
HE Liu, SHAN Peng
2010, 25(4): 884-890.
Abstract PDF(1457KB) icon1575 icon397
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Employing the strategy of "experimental design+ response surface model + genetic algorithm",a response surface model code based on the artificial neural network and a genetic algorithm code were developed;and this paper established a numerical aero-optimization platform for three-dimensional(3-D) axial-flow compressor blade.This integral platform contains also the commonly used arbitrary camber line airfoil and blade formatting code and 3-D computational fluid dynamics solver.A fulfilled inverse-design of a zero-stage compressor rotor of a turbojet engine was optimized by this platform.The optimization object is to achieve the maximum adiabatic efficiency at the design point,while the mass flow rate and total pressure ratio are kept unchanged as the constraints.The relative flow-angle and the inner-blade deviation-angle are chosen separately as the independent-variables in two optimization cases.In order to directly couple the optimization method with the modern design system,the aerodynamic variables with physical meanings were chosen instead of the commonly used geometric variables as the optimization independent-variables.As compared with the original rotor,the adiabatic efficiencies of two optimal rotors increase by 0.82 and 0.73 percentage points,respectively.It shows that 3-D optimization method based on the aerodynamic variables has a good performance.
Investigation on clocking effect of 1.5-stage transonic compressor
REN Xiao-dong, GU Chun-wei
2010, 25(4): 891-896.
Abstract PDF(1232KB) icon1586 icon433
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The clocking effect in the 1.5-stage compressor,which would be used in the 1.5-stage transonic compressor test rig,was investigated by computational fluid dynamics(CFD) method in this paper.The results show that:(1) The compressor efficiency is high and mixing loss is low when the stator wake is mixed with the outlet guide vane(OGV) boundary-layer fluid.(2) The compressor efficiency is low and mixing loss is high when the stator wake is mixed with the OGV main flow area fluid.(3) The highest efficiency is 0.4% higher than the lowest efficiency.(4) The inlet guide vane(IGV)-stator clocking effect can be neglected,just leading to 0.025‰ improvement of compressor efficiency.Besides,the optimal clocking position versus the stator-OGV axial clearance plot was got.
Design and numerical simulation of the effect of heat transfer on the micro centrifugal compressor performance
SHEN Yu-xin, LIU Jian-jun
2010, 25(4): 897-901.
Abstract PDF(1817KB) icon1684 icon415
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A micro centrifugal compressor was designed for centimeter-scale micro turbomachinery,which has a diameter of 26 mm,designed rotate speed of 240 000 r/min,and designed mass flow rate of 30 g/s.Three-dimensional numerical simulations under adiabatic and isothermal conditions of solid wall were performed by using the commercial CFD(computational fluid dynamics) software CFX.The results show that,as compared with adiabatic condition,the mass flow rate at the isothermal condition decreases 7.53%,total to total isentropic efficiency decreases about 18.1%,total pressure rate decreases 21.7% at the same shaft work input.Taking the effect of heat transfer into account,the micro centrifugal-flow compressor was redesigned.CFX simulation results show that the improved design satisfies the design requirement of the micro turbomachinery.
Hypersonic experimental investigation on interference and stage separation of a multi-body system
WANG Yuan-jing, WU Ji-fei, TAO Yang, LUO Xin-fu, QIAN Feng-xue
2010, 25(4): 902-906.
Abstract PDF(790KB) icon1945 icon429
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Investigation on aerodynamic interference during stage separation of a hypersonic multi-body system was conducted in this paper.A typical reusable space vehicle was applied in this research,which is composed of a booster and a reentry part.The test was conducted in FL-31 wind tunnel with Mach number of 6.97.The results show that,complicated shock wave interference exists in the multi-body system and this aerodynamic interference during stage separation is essentially induced by shock wave interference.
Shallow cavity noise influencing by boundary-layer thickness at supersonic speeds
YANG Dang-guo, LI Jian-qiang, FAN Zhao-lin, LUO Xin-fu, JIANG Wei-min
2010, 25(4): 907-911.
Abstract PDF(710KB) icon1592 icon398
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An experimental investigation had been constructed to perform effects of boundary-layer thickness on shallow cavity noise characteristics,and sound pressure level(SPL) distributions and sound pressure frequency spectrum(SPFS) characteristics inside shallow cavities with length to depth ratios of 12 and 15 at supersonic speeds were analyzed.The data presented herein was obtained over a Mach number of 1.5 at a Reynolds number of 2.26×107 per meter.The results show that decrease in ratios of the boundary-layer thickness to the cavity depth(δ/D) causes flow oscillation amplification,noise enhancement inside the shallow cavities.Decrease in δ/D leads to obvious increases in SPL in the most frequencies at different positions measurement in the forward and rearward of the shallow cavities.Shock waves in the middle of the shallow cavities which induced by supersonic free-stream flow disturb the flow structure,which makes boundary-layer flow characteristics has few influences on the aeroacoustic characteristics in the middle of the shallow cavities.Generally,decrease in boundary-layer thickness has significant influences on flow oscillations and noise characteristics of shallow cavity at supersonic speeds.
Concurrent subspace optimization design of hypersonic cruise vehicle
CHE Jing, WANG Wen-zheng, HE Kai-feng
2010, 25(4): 912-917.
Abstract PDF(1037KB) icon1540 icon383
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By employing orthogonal experiment design method to build up an initial database and approximate response surface model of quadric polynomial,this paper presented a concurrent subspace optimization process of hypersonic cruise vehicle(HCV) for airframe/scramjet integrated shape parameters and trajectory parameters based on multi-restricted and multi-disciplinary conditions.Through the optimization process,the optimal shape and trajectory parameters on multi-disciplinary synergetic conditions were acquired,providing a reference scheme of HCV for further detailed design.
Experimental investigation of HLFC mechanism on swept wing
WANG Fei, Eriqitai, WANG Qiang, GUO Hui, SU Pei-ran
2010, 25(4): 918-924.
Abstract PDF(1457KB) icon1534 icon346
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Hybrid laminar flow control(HLFC) experiments were conducted in the low-turbulence wind tunnel on a NACA64A-204 swept airfoil.Naphthalene sublimation flow visualization technology and hot-wire measurement method were taken to examine the effects of suction quantities on transition location and hydrodynamic stability.Experimental results show that transition location occurs at x/c≈0.4 in the non-suction case,and transition location can reach 80% of chord length(behind the minimum pressure point) in both standard and twice suction quantities.The HLFC methods can reduce the distortion of the velocity profile,bring down the nonlinear interaction among the disturbances,decrease the energy of dominated perturbation,and delay transition to achieve lager laminar flow region.
Calibration method for microphone array on flow impedance test rig
WANG Li, WANG Tong-qing
2010, 25(4): 925-929.
Abstract PDF(784KB) icon1489 icon451
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An in-situ calibration method was developed in this paper.The acoustic pressure data from two calibrated microphones were utilized to calculate the sound field in ducts.Then the sensitivity of every microphone was obtained by comparison of the signal measured by every microphone with the sound field calculated above.The advantage of the current method is that all microphones can be calibrated simultaneously and the phase sensitivities of these microphones are also obtained.A calibration experiment has been conducted on flow impedance test rig(FITR),and the calibration results were compared with those calculated by the mode-matching method,showing a good agreement.Additionally,as every microphone's complex sensitivity can be obtained respectively at different frequencies,low-precision microphones can have better precision by being calibrated using high precision microphones.By using these calibrated microphones,the cost of experiment can be reduced obviously.
Analysis method for linear process with independent increments
FU Hui-min, WU Qiong
2010, 25(4): 930-935.
Abstract PDF(2427KB) icon1421 icon415
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The concept and definition of linear process with independent increments were presented.Then the regression model and analysis method for linear process with independent increments were established.Furthermore,the regression equation and confidence limit curves were given.The proposed method extends the traditional regression analysis which is only suitable to data points to stochastic processes.Therefore the linear processes with independent increments such as performance degradation and crack propagation can be analyzed as an integration by the method.Compared with the traditional method,the presented method not only has higher precision but also solves the problem of reliability assessment with very small sample.The method has been applied in reliability tests successfully,showing that a great number of specimens can be saved.
Measurement of contact stiffness during microslip
CHEN Lu-lu, MA Yan-hong, LI Di, HONG Jie
2010, 25(4): 936-942.
Abstract PDF(1392KB) icon1578 icon468
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A measurement system was designed to accurately determine the contact stiffness between two surfaces of dry friction damper,so as to separate the system stiffness from the contact stiffness.The influences of exciting force and initial normal load were investigated in detail.The curve of the tangential contact stiffness for variable normal preload was obtained by fitting the results according to the given condition.This research can test and improve the calculation models,laying a foundation for establishing a practical method for numerical simulation of contact stiffness.
Design and application of a disturbance rejection rotor speed control method for turbo-shaft engines
ZHANG Hai-bo, SUN Jian-guo, SUN Li-guo
2010, 25(4): 943-950.
Abstract PDF(937KB) icon2091 icon470
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Turbo-shaft engine's control methodology was mainly studied in this article.Active disturbance rejection control(ADRC) method has been emerging in recent years.A hybrid control structure,i.e.an cascade proportion integration differentiation(PID) combined with torque's ADRC compensation,was proposed to improve the engine's disturbance rejection ability,and keep the formal control structure of the engine unchanged.The control system takes advantage of the excellent strong disturbance compensation property.The control system has better dynamic disturbance rejection ability than traditional system by simulation of helicopter's rapid lifting up and down based on the integrated helicopter/ turbo shaft engine platform.
Simulation experiment of the influence of elevation on performance of a rotary engine
TANG Ting-xiao, ZHAO Hou-liang, CHEN Huai-hai
2010, 25(4): 951-956.
Abstract PDF(1310KB) icon1797 icon477
Abstract:
With the increase of elevation,the power of the rotary engines is decreased in the higher air level.In order to measure the performances of rotary engine in different altitudes,an electronic fuel injection control system for the engine with real-time parameter monitor was put forward in the paper.Performance tests of a 208 cm3 engine were carried out by changing the atmospheric pressures to simulate the different elevations.An elevation compensation method was suggested for the engine's smooth running.The measured results provide very important references for control of these kinds of rotary engines to work stably in different heights in the sky.
Research on the variation rules of meshing stiffness of the helical gear
BU Zhong-hong, LIU Geng, WU Li-yan
2010, 25(4): 957-962.
Abstract PDF(2346KB) icon1746 icon499
Abstract:
The time-varying meshing stiffness is one of inherent characteristics of gear system vibration.The meshing stiffness of an external and inner helical gear pair with different helical angles was solved respectively using a modified method,which could determine the meshing stiffness and actual load distribution based on linear programming.The variation rules of meshing stiffness during one whole meshing period were summarized.The following findings were obtained in this paper: the key factor that influences the meshing stiffness most significantly is the whole length of contact-line of all the teeth in the engagement.The meshing stiffness decreases at the instantaneous position where the teeth enter contact or exit contact.The results were compared with those obtained by aerospace industry ministry standard(HB/Z 84.1-1984) and the influence of rim thickness on the meshing stiffness was analyzed.

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