2010 Vol. 25, No. 9

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Display Method:
Discussion on combustion airflow distribution of advanced staged combustor
LIN Yu-zhen, LIN Yang, ZHANG Chi, XU Quan-hong
2010, 25(9): 1923-1930.
Abstract PDF(922KB) icon1601 icon457
Abstract:
One of the significant characters in superhigh temperature-rise combustors and low emission combustors is represented by the high combustion airflow rate which is more than 60% in the airflow distribution.With this characteristic,the normal combustors could not achieve the basic requirements of the high temperature-rise combustors and low emission combustors.Based on the basic characteristics of combustion and the basic performance of the combustor,this paper emphatically analyzed the limit of the combustion airflow distribution on normal combustor design,and discussed the key points for the high combustion airflow rate combustor and the concept of the flexible staging.This paper compared the characteristics of different staging methods,pointed out that the rich premix prevaporized(RPP) center staged combustion is a preferred method for superhigh temperature-rise combustors,and the lean premix prevaporized(LPP)center staged combustion is a preferred method for low emission combustors.
Experimental study on the turbine blade cooling channel with crossed-ribs
DENG Hong-wu, TAN Yan, WANG Jia-ren, SUN Ji-ning
2010, 25(9): 1931-1937.
Abstract PDF(929KB) icon1638 icon428
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The characteristics of heat transfer and flow resistance in turbine blade cooling channel were studied experimentally with use of vapor heating method,which could provide the experimental model with equivalent wall temperature boundary condition.The experiments were carried out under the condition that the Re was 10 000～60 000.The experiment models adopted the structure of crossed-ribs,pin-fins and longitudinal dividers.The outside wall was divided into ten regions and the condensation vapor of the regions was gathered to get the local heat transfer coefficient.The results show that the crossed-ribs channel could lead to better heat performance than the pin-fins channel.The results also show that,in the case of Re<30 000,the structure with the best general heat transfer performance is crossed-ribs channel of 0612,and in the case of Re>30 000,the best one is crossed-ribs channel of 0412.
Calculation method for matching enthalpy parameter of three-wheel bootstrap high-pressure water-separated system
ZHANG Xing-juan, LI Feng, YANG Chun-xin
2010, 25(9): 1938-1941.
Abstract PDF(306KB) icon1619 icon432
Abstract:
A calculation model for matching the enthalpy parameters of three-wheel bootstrap cooling system was introduced according to the shortcomings of traditional method for matching thermal parameters.The model could simplify the wet cooling point matching process.And the thermal parameters of each system's status point was calculated by the model.The results show that,with the use of enthalpy instead of temperature as the state parameter for system matching,it's viable to simplify the calculation process.An optimal water equivalent ratio is found by system performance analysis;as the three-wheel power ratio increases,the compressor pressure ratio and turbine expansion ratio decrease.
Analysis of heat sink for rejected condenser heat of loop heat pipes for cooling avionics
SU Xiang-hui
2010, 25(9): 1942-1947.
Abstract PDF(501KB) icon1911 icon471
Abstract:
For the purpose of suitability validation of the approach to dissipate heat from aircraft avionics by the loop heat pipes,the available heat sinks for rejected condenser heat of loop heat pipe were discussed in this paper.The potential for using the aircraft wings skin as a heat sink of the loop heat pipe condenser was proposed.An analysis of the heat transfer for an aircraft wing skin was performed.The aircraft wing inner skin temperature for the entire mission envelope was predicted to determine heat sink temperature range of the loop heat pipe condenser.Theoretical calculations reveal that dissipating heat from the aircraft skin using a loop heat pipe between the avionics package and the aircraft skin is a possible thermal management technique.
Detailed and reduced chemical kinetic mechanisms for RP-3 aviation kerosene combustion
XIAO Bao-guo, YANG Shun-hua, ZHAO Hui-yong, QIAN Wei-qi, LE Jia-ling
2010, 25(9): 1948-1955.
Abstract PDF(845KB) icon2428 icon777
Abstract:
A detailed chemical kinetic mechanism containing 109 species and 946 elementary reactions for kerosene combustion was developed.With the use of quasi-stationary state approximation(QSSA) method,a reduced chemical kinetic mechanism including 22 species and 18 global reactions was obtained from the detailed kinetics.By comparing the reduced mechanisms with the typical experimental results and reference results,high precision of the reduced mechanisms is shown,which can be used to represent the ignition characteristic of RP-3 aviation kerosene fuel,and also simulate accurately the combustion of kerosene.
Investigation on the mixing characteristics of combustion chamber with bilateral inlet at head
JING Jian-peng, GUO Rong-wei
2010, 25(9): 1956-1963.
Abstract PDF(1261KB) icon1477 icon429
Abstract:
Numerical simulation and experimental verification of the mixing characteristics of combustion chamber with bilateral inlet at head were conducted in this study,the performance parameters and flow field characteristics of the mixing duct were obtained.The results show that the bilateral vortices at the head of the mixing duct is the key to ignition and flame stabilization,the total pressure recovery of the mixing duct decreases slightly under attack or yaw angle,so the combustion chamber shall allow to adjust the fuel quantity to avoid unstable working state of the inlet.It can be seen in the paper that the numerical results are consistent with the experimental results,indicating that the numerical simulation is feasible and can be used as a reference to the combustion chamber design and combustion organization.
Investigation on the influence of jet pressure on detonation initiation via imploding annular shock waves
ZENG Hao, HE Li-ming, ZHANG Xiong-wei, LI Hai-peng, CHEN Xin
2010, 25(9): 1964-1970.
Abstract PDF(1338KB) icon1703 icon468
Abstract:
In order to investigate the influence of jet pressure on detonation initiation via imploding annular shock waves,detonation initiation with different jet pressures was simulated with hydrogen-air mixture.The results indicate that,when jet pressure is high enough,imploding annular shock waves can form high pressure and high temperature region that lead to direct initiation;thrust wall can strengthen reverberation shock,which contributes to initiate detonation;when the jet pressure is lower than its critical value,detonation can not be initiated.
Analysis of turbulence field of film cooling based on large eddy simulation
LIU Ning, SUN Ji-ning
2010, 25(9): 1971-1977.
Abstract PDF(999KB) icon1704 icon438
Abstract:
Large eddy simulation of film cooling over flat plate with 30° streamwise inclined cylinder hole was performed to investigate the turbulence field of film cooling.The Reynolds number at the jet exit was 2 600,and the blowing ratio was 0.5.Numerical results show that flow separation in the hole increases the turbulence kinetic energy and results in the decrease of film cooling effectiveness,which should be avoided as much as possible in design of coolant supply plenum.Eddy viscosity coefficient relevant to the lateral diffusion of film has peak on both sides of the hole,while the peak predicted by isotropic eddy viscosity model is in the shear layer between mainflow and jet.This results in the overprediction of vertical penetration and underprediction of lateral spread of the jet.Large eddy simulation can be used to construct anisotropic turbulence model in order to improve the accuracy of turbulence model.
Study of diffusion jet flame characteristic under centrifugal force
GUO Xin-hua, ZHANG Chi, LIN Yu-zhen
2010, 25(9): 1978-1983.
Abstract PDF(739KB) icon1594 icon452
Abstract:
The paper adopted the straight and curving passages to investigate the flame characteristic under the same test conditions.The diffusion jet flame characteristic was studied under high centrifugal force.Through comparison and analysis of the test results,it was obviously observed that the flame speed was faster in the curving passages under buoyant force action resulting from a high centrifugal force.The high centrifugal force made the diffusion flame speed faster and weakened the interference of crossflow.The diffusion flame could mix and react with the mainstream much more easily.The penetration depth of jet flame in the crossflow was increased.
Injection characteristics of supercritical n-decane into atmospheric environment
GAO Wei, LIN Yu-zhen, FU Zhen-bai, XU Quan-hong
2010, 25(9): 1984-1988.
Abstract PDF(617KB) icon1479 icon439
Abstract:
The injection of supercritical n-decane into a quiescent atmospheric environment was experimentally investigated to study the jet structures and phase transition process near the nozzle exit.It was found that supercritical n-decane jets injected above the critical point underwent ideal gas-like expansion and exhibited visible Mach disk shock structures.The axial location of the Mach disk increases with the growing injection pressure,and the injection temperature has little effects on the axial location of Mach disk.The phase transition process analysis reveals that,the supercritical n-decane is penetrated directly into the gas region from the supercritical region at the nozzle exit,without passing through the two phase region at higher injection temperature.Supercritical n-decane condensation phenomenon occurs in the nozzle and the outlet,and the fuel passes through the two phase region when fuel is injected near the critical point.
Regression analysis method for superalloy stress relaxation process
FU Hui-min, WU Qiong
2010, 25(9): 1989-1993.
Abstract PDF(311KB) icon1637 icon448
Abstract:
Based on the linear process regression analysis theory,a regression analysis method for superalloy stress relaxation process was put forward.Then the residual stress regression equation and one-sided lower confidence limit curve with high confidence level and reliability were given.By this method,the stress relaxation process can be analyzed as an integration and the lengthwise information of the residual stresses at different test times is applied,therefore the presented method not only has higher precision but also provides reasonable estimates for small sample sizes.Furthermore,the proposed method can avoid distortion of the relaxation curve in the traditional method especially when the sample size is very small.
Design of the simulation test device of a support with random stiffness parameter
LIU Bao-guo, CHENG Min, XU Ming-xin
2010, 25(9): 1994-1999.
Abstract PDF(620KB) icon1580 icon416
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Based on the principle that electromagnetic force varies with electromagnetic field,a test device with parallel electromagnetic and mechanical support elements was designed to realize the varying of the system support stiffness with the electromagnetic field strength.By studying and linearizing the mathematical model of this simulation test device,four design rules were given,making sure that the system support stiffness parameter could be randomly controlled by the controllable random electric current.The linearized rule guarantees the linearity of the system support stiffness;the linear random rule engenders the linear relationship between the support stiffness parameter and the controllable random electric current;the rule of significant random stiffness weight brings about obvious randomness of the system support stiffness,and satisfies the demand of testing;finally the rule of the positive system total stiffness ensures the stability of the simulation test device.Consequently,the simulation test device of random stiffness parameter has been constructed according to these four rules.The test results show that the simulation test device can well simulate the random stiffness parameter.
Design method of imitation specimen for engine disk with any maximum stress gradient path
LU Shan, WANG Chun-guang, CHEN Jun
2010, 25(9): 2000-2005.
Abstract PDF(766KB) icon1493 icon421
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A design criteria of disk two-dimensional(2-D) imitation specimen based on stress-life was established.The imitation specimen's optimum design methods about random maximum stress gradient were proposed,including: searching automatically the maximum first principle stress gradient route,stress distribution and two-stage optimization method of the imitation specimen.An equivalence principle of elastic and plastic design for the imitation specimen was proposed based on the analysis of examples.
Probability characteristics for response localization of mistuned bladed disk assemblies
YU Chang-bo, WANG Jian-jun, LI Qi-han
2010, 25(9): 2006-2012.
Abstract PDF(747KB) icon1620 icon424
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Based on the reduced-order finite element(FE) model and its Monte Carlo-response surface method,the localization characteristics of a typical bladed disk with geometry mistuning were researched in detail,with particular regard to the subjects of the probability characteristics for the forced response.An FE modeling method of bladed disks with geometry mistuning was given,and the order-reduction method was presented as well.Then the response properties of the tuned structure were discussed.The response magnification factor was defined to assess quantitatively the behavior of the vibratory localization.The statistical characteristics of the forced response of the stochastically mistuned and detuned structures were simulated and their main properties were explained.Results indicate that there is a peak phenomenon in the mean values and standard deviations of the response with the increasing mistuning strength.
Reliability and multidisciplinary design optimization for turbine blade based on decoupled method
HE Qian, LI Yuan-sheng, WEN Zhi-xun, YUE Zhu-feng
2010, 25(9): 2013-2018.
Abstract PDF(2068KB) icon1544 icon446
Abstract:
A suitable reliability-based multidisciplinary design optimization(RBMDO) framework for turbine blade was proposed by combining inverse first order reliability analysis method(inverse FORM) with multidisciplinary feasible(MDF) method.The Kriging approximate model with updating function was introduced to reduce the computational cost of MDF caused by complex structure.The proposed method is efficient since it can decouple reliability analysis process from optimization process.A turbine blade design optimization was employed to illustrate the feasibility and efficiency of the proposed method.It shows that the optimal results can satisfy the required reliability and the efficiency is improved 63.8% by the proposed method as compared with commonly used double-loop based RBMDO method.It is feasible and efficient to apply this method to engineering design.
Double factor level analysis method of simulation results
WU Wen-juan, FU Hui-min
2010, 25(9): 2019-2022.
Abstract PDF(252KB) icon1451 icon389
Abstract:
To analyze every factor level and every level combination interaction effect,a double factor level analysis method of simulation results was presented.When the simulation results were not correct,not all the factor levels and the level combination interaction effects were wrong.The presented method can determine which level of which factor has not been simulated correctly,or find out the incorrectly simulated level combination interaction effect.According to the flow chart in the paper,the method can be carried out in practical engineering,and guide the programming and the modification of simulation software system.
Design and experimental study of a SMA motor with low speed and continuous rotation
LIU Ying, YAN Xiao-jun
2010, 25(9): 2023-2029.
Abstract PDF(1079KB) icon1461 icon423
Abstract:
A continuously rotating motor actuated by shape memory alloys(SMA) wires was designed,which rotates with a low speed and high torque.Liang-Roger constitutive model was used to design the SMA wire-spring actuator.Based on the actuator,the mechanical structure and control system were designed.Finally the motor was tested and it shows that: the SMA motor can rotate continuously with the speed of 0.03 rad/min under 6 V constant power supply at 27 ℃.It is concluded that the new motor,which is actuated by SMA wires owning the characteristics of low rotating speed,high torque and high power density,has a potential use in industry application.
Plasticity-induced fatigue crack closure under plane strain condition with dwelling
CHEN Ya-long, YANG Xiao-guang, SHI Duo-qi
2010, 25(9): 2030-2035.
Abstract PDF(966KB) icon1804 icon417
Abstract:
Visco-plastic finite element method was used to simulate fatigue crack propagation under constant amplitude cyclic and dwelling tensile loading conditions for a middle-crack specimen made of turbine disc material Udimet720 Li(low inclusion).Node release was used to model the crack propagation at 700 ℃.The influences of different maximum cycle loads and dwelling time on crack open stress intensity factor were studied under plane strain and constant load stress ratio R=0 condition.The values of normalized crack open stress intensity factor were dispersed under different maximum cycle loads,increased at the beginning of the cycles,and then decreased slightly to a steady value after adequate cycles with the crack growth.The result shows that the increase of dwelling time will increase normalized crack open stress intensity factor.Creep may influence the crack growth rate at elevated temperature and under dwelling condition.
Performance parameter equivalent correction of turbo-shaft engine
HUANG Kai-ming, HUANG Jin-quan, REN Dan, YANG Fang, ZHANG Xin
2010, 25(9): 2036-2040.
Abstract PDF(479KB) icon1796 icon494
Abstract:
The turbo-shaft engine with free turbine can't guarantee similar rule perfectly.For the purpose of engine parameter correction,the traditional resemble correction formula with too much tolerance was discussed.And,a more scientific method called equivalent conversion of turbo-shaft engine parameters correction based on simulation was brought forward.Finally,an example was presented.The results show that,this new method can be used to reduce the tolerance of the performance parameter correction,laying a foundation for formulating the turbo-shaft engine test performance modification standard and acceptation specification.
Encapsulation,calibration and application of an economical measurement microphone
WANG Li, WANG Tong-qing
2010, 25(9): 2041-2049.
Abstract PDF(2060KB) icon1361 icon416
Abstract:
An economical measurement microphone was encapsulated using a consumptive microphone in this paper,and a calibration rig was designed and validated firstly,and then the amplitude and phase of the microphone was calibrated on this rig.The calibrated microphone was used as measurement microphone on the flow impedance test rig(FITR) in our laboratory,and the measured data were compared with data measured by Bruel & Kjaer(B & K) 4938 microphone.The comparison result shows that the microphone can be used as a measurement microphone when it is calibrated.
Numerical investigation on performance of second throat in transonic wind tunnel
CONG Cheng-Hua, LIAO Da-Xiong, CHEN Ji-Ming, QIN Hong-Gang
2010, 25(9): 2050-2056.
Abstract PDF(1086KB) icon1345 icon469
Abstract:
This paper presented the numerical investigation reports about the performance of transonic wind tunnel's second throat.Firstly,second throats were designed according to the general design rule.Then exact Mach number control was studied by numerical simulation when different second throat areas were analyzed by adjusting wall flaps and center body.The numerical results indicate that the control precision of Mach number is 0.001.At last,different models were studied based on the numerical results,and then the most efficient model was selected.
Components and engine matching of core-derived turbofan
OUYANG Hui, ZHU Zhi-li, YU Bo-liang
2010, 25(9): 2057-2063.
Abstract PDF(850KB) icon1805 icon456
Abstract:
The gas turbine core-engine derivative model for turbofan serialization,which focused on thermo-cycle approach,was established based on components and engine matching between core-engine and low-pressure system.The model took into account high-low system interaction,core turbine operation and inner-outer duct compatibility comprehensively,and then it was utilized to analyze derived turbofans' cycle and performance.The results show that the coupled low-high systems' constraints influence turbofan's performance and cycle parameters,providing engineering reference and design criteria for core-derived turbofan's matching and simulation.
Study of aerodynamic characteristics of an airfoil in rain
ZHANG Rui-min, CAO Yi-Hua
2010, 25(9): 2064-2069.
Abstract PDF(911KB) icon1602 icon427
Abstract:
The aerodynamic characteristics of an airfoil in rain were studied using computational fluid dynamics method.The flow field was calculated by solving the steady compressible Navier-Stokes equations.The trajectories of raindrops in the flow field were tracked with Lagrange method and the collection efficiency of airfoil surfaces was obtained.The model of water film was also set up,then assuming that water film accumulates layer-by-layer in the direction normal to the airfoil surface and the changes of airfoil shape due to rain and the roughness height on water film were predicted.The influence of rain on aerodynamic characteristics of the airfoil was studied using k-ω SST(shear-stress transport) two equations turbulence model with enhanced wall treatment.The results show that rain effect on the lift coefficient and drag coefficient of the airfoil is little within the low angles of attack;rain can cause boundary airflow separation on upper surface and thus result in serious aerodynamic penalties when the airfoil is nearly stalled.
Numerical investigation of a vector-enhanced dual-throat thrust-vectoring nozzle
ZHOU Hui-chen, TAN Hui-jun, SUN Shu, CHENG Dai-shu
2010, 25(9): 2070-2076.
Abstract PDF(1646KB) icon1744 icon470
Abstract:
A design concept of vector-enhanced thrust-vectoring nozzle was proposed to overcome the shortcoming of dual-throat thrust-vectoring nozzle of small vector angle.In the newly designed nozzle,two expansion ramps were added after the second throat of the nozzle to achieve greater vector angle using the Coanda effect.The feasibility of the design concept was firstly analyzed by 2-D simulation,and then the design law of the expansion ramps was studied.Results show that,with the expansion ramps,the efficiency of thrust-vectoring is remarkably enhanced with a vector angle over 20°.But some loss of thrust efficiency is also found.In the researched parametric range,the expansion angle,expansion length and expansion contour affect obviously the performance and the internal flow pattern of the nozzle.Furthermore,placing slots on the concave expansion ramps can suppress the overexpansion of the exhaust flow effectively,and obtain a vector angle of 24.12° and a thrust ratio of 0.929 with consumption of only 2.8% secondary flow.
Filghtting test of inlet/engine compatibility during rapidly changing aircraft maneuvers
ZHAO Hai-gang, QU Ji-yun, SHI Jian-bang, JIANG Jian, ZHANG Xiao-fei
2010, 25(9): 2077-2082.
Abstract PDF(646KB) icon1598 icon454
Abstract:
The test of inlet/engine compatibility was carried out during aircraft maneuvers with rapidly changing angle-of-attack(AOA),angle-of-sideslip(AOSS).The same important test data about inlet/engine compatibility by flightting test were acquired.The test data were selected,calculated and analyzed,and at last the relation among rapidly changing aircraft maneuvers,inlet total pressure distortion and the stability of engine,as well as the relation between inlet total pressure distortion and the stability of engine were obtained.It shows that,the stability of engine and inlet total pressure distortion become worse due to rapidly changing aircraft maneuvers.
Comparative study of PIV and LDV measurements in the wake of a propeller
LI Guang-nian, ZHANG Jun, LU Lin-zhang, ZHANG Guo-ping
2010, 25(9): 2083-2090.
Abstract PDF(1465KB) icon1719 icon408
Abstract:
In order to validate the accuracy of PIV（particle image velocimetry）,the paper carried out the experiment to measure the same propeller wake by using PIV and LDV（laser Doppler velocimeter） technique in the cavitation tunnel during the same period and working condition.The results indicate the PIV data get good agreement with the LDV data in the flow macrostructure.The PIV can display the velocity peak which is only span 8° in peripheral direction,but the velocity peak is smaller than LDV data.As a whole,the difference of PIV data and LDV data is about 2%～3%,further analyses show that the improvement of the positioning accuracy of PIV system can reduce the error.
Experimental study on flow in the impeller of low specific speed pump using particle image velocimetry
SHAO Chun-lei, GU Bo-qin, HUANG Xing-lu, ZHOU Jian-feng
2010, 25(9): 2091-2096.
Abstract PDF(932KB) icon1807 icon444
Abstract:
Particle image velocimetry(PIV) system,pump experimental facility and test scheme were introduced.An experimental investigation of flow in the impeller was conducted at three different flow rates on three measurement planes by means of PIV.The velocity vector distribution was obtained.The velocity distribution in circumferential and axial directions and the influence of flow rate on the distribution were investigated.The results indicate that,the velocity near the suction surface decreases slightly,and that near the pressure surface changes dramatically with decreasing flow rate.The fluid flows back near the pressure surface when the flow rate reaches 0.6Qd.At the outlet of impeller,the flow rate has no significant influence on the direction of relative velocity.The velocity in the impeller passage distributes homogeneously in axial direction.The absolute velocity shows an increasing trend in radial direction.The circumferential component of nondimensional absolute velocity decreases from the pressure surface to the suction surface,and also increases with the decline of flow rate.The results provide valuable information for the design of impeller and experimental study on flow in the centrifugal pump.
Throughflow design of compressor considering bleeding flow effect
ZHAO Bin, LI Shao-bin, WU Hong, HOU An-ping, ZHOU Sheng
2010, 25(9): 2097-2102.
Abstract PDF(591KB) icon1510 icon459
Abstract:
In order to observe the throughflow design of compressor under the influence of bleeding flow,a bleeding model was set based on the circumference bleeding slot.Bleeding was considered in the throughflow design of compressor by changing the endwall no-slip-boundary condition of bleeding flow area into the velocity law of endwall for the new bleeding boundary condition.A comparative research between the bleeding and non-bleeding throughflow field and 3-D numerical analysis of a two-stage compressor show that,the bleeding model and its throughflow design method can reflect the influence of bleeding parameters as a result of the throughflow calculation.Furthermore,the bleeding model and its throughflow design method can also accurately reflect the change of bleeding with the local flow condition of bleeding flow area.
Design and analysis of HP-turbine for variable cycle engine
LIU Zhi-gang, FANG Xiang-jun, LIU Si-yong, WANG Ping, YIN Zhao
2010, 25(9): 2103-2110.
Abstract PDF(1450KB) icon1880 icon446
Abstract:
A supersonic highly loaded high-pressure turbine with large enthalpy drop was designed for a variable cycle engine(VCE) in two operating modes of high and low bypass ratio by using similarity principle,and the blade profiles were implemented by means of a new three-dimensional(3-D) profile design method based on S1 stream surface.Then,3-D numerical simulations were performed for the turbine in both operating modes under different thermodynamic cycle parameters to confirm the design methods and results.One-equation turbulence model of Spalart-Allmaras was applied to solve Reynolds averaged Navier-Stokes equations,whilst the transition model of Abu-Ghanam Shaw was introduced into the calculations to capture the development process of boundary layer on blade surface.The results of simulations indicate that excellent aerodynamic performances are available in both operating modes with overall efficiency of 92.79% and 92.31%,respectively,which are superior to anticipated targets;the used profile design method by S1 stream surface is more precise and effective than conventional cylinder method for turbine blade,since 3-D characteristics of flow fields are considered elaborately.
Analysis of the parameter of repetitious air-launch adjacent space aircraft based on liquid rocket engine
LING Gui-long, ZHANG Jian-wei
2010, 25(9): 2111-2216.
Abstract PDF(753KB) icon1567 icon421
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For a environment propellant group,the simulation model,mass model and orbit model of adjacent space aircraft were established.By setting combustion chamber pressure,ample oxygen coefficient and nozzle exit pressure as variables,the performance of adjacent space aircraft was analyzed.The results show that it will be better with higher combustion chamber pressure under specific task for improving adjacent space aircraft performance.The best ample oxygen coefficient can be achieved at 0.99.If permitted,the nozzle area expansion ratio deployed should be as big as possible,since it is limited by rocket outer diameter and technology level,etc.The correlation study could provide a guidance for the system project study of other similar adjacent space aircrafts.
Experimental and computational study of vortex/oblique shock interaction
WEI Bao-xi, ZHANG Cheng-liang, XU Xu
2010, 25(9): 2117-2124.
Abstract PDF(1609KB) icon1859 icon496
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An experimental study of the interaction between supersonic streamwise vortex and two-dimensional oblique shock was conducted to investigate the application of vortex/oblique shock interaction in supersonic combustion.The strong/moderate/weak interactions at different shock strengths were observed in the experiment using color-schlieren method.The numberical results agree with the experiments.Experimental results show that,for the case of Ma=2.3,10 degrees wing attack angle,vortex is strong,and as wedge compress angle increases the vortex/oblique shock interaction changes from weak to strong interaction.Numberical results indicate that for the same wing and wedge situation,Mach number has strong influence on vortex/shock wave interaction.Total temperature can affect the size of the bubble shock.The effect of total pressure is neglectable.
Three-dimensional simulation of beam ions in ion thruster optics system
ZHONG Ling-wei, LIU Yu, REN Jun-xue, QIU Qian
2010, 25(9): 2125-2131.
Abstract PDF(1190KB) icon1728 icon408
Abstract:
A three-dimensional numerical simulation was carried out with the particle-in-cell method.The electric field,the paths of the ions,the spatial and the phase spatial distribution of the ions in the calculation domain were obtained from the simulation.It shows that the ion transparency of the screen grid and the acceleration grid is 69.3% and 100%,respectively,which is respectively bigger than the physical transparencies of 67.1% and 31.1% of the screen grid and the acceleration grid.The simulation parameters selected in the calculation are reasonable.The simulation results can provide a reference for the preliminary design of the ion thruster optics.
Numerical simulation of dynamic characteristics of an open-end swirl injector
FU Qing-fei, YANG Li-jun, QU Yuan-yuan, GU Bin
2010, 25(9): 2132-2138.
Abstract PDF(1375KB) icon2078 icon419
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Theoretical studies and numerical simulation on dynamic characteristics of an open-end swirl injector were performed.The response of the injector flow to external excitations was investigated by superimposing periodical oscillation of flow-rate at the inlet.The numerical simulation results show that the surface wave causes oscillation of the liquid film in the swirl chamber,and then the flow oscillation occurs at the spout.Moreover,the frequency of the vortex wave is much smaller.The phase angle between the flow oscillation at spout and the pressure drop oscillation is proportional to the oscillation frequency,which agrees well with the linear injector dynamic characteristics theory.
Dynamic process identification of aircraft engine based on a novel sparse least square support vector machines
WANG Hai-tao, XIE Shou-sheng, WU Wei, MIAO Zhuo-guang, WU Yong
2010, 25(9): 2139-2147.
Abstract PDF(3338KB) icon1735 icon422
Abstract:
A novel sparse strategy was proposed for the least square support vector machines regression,and the dynamic process identification of aircraft engine was analyzed in particular.In the process of solving the original sample,the special nonlinear mapping matrix was recursively decomposed by using the modified Gram-Schmidt method,and the excellent sample was selected when the square of remaining output reached the threshold value;thus,the new sample quantity was reduced and the least square support vector machines(LS-SVM) regression model training speed was enhanced by saving memory.The simulation result shows that,the algorithm has better sparseness,less training time and equivalent precision;and the aircraft engine dynamic process simulation shows that the predicting error of high rotor's relative rotational speed is less than 0.2%,the predicting error of the low rotor's relative rotational speed is less than 0.35%,and the predicting error of the temperature at the exit of high-pressure turbine is less than 3.5 ℃.The model is suitable for aircraft engine's control and system simulation.
Integrative simulation platform design for aero-engine digital electronic control system
YAO Hua-ting, WANG Xi, SU San-mai
2010, 25(9): 2148-2154.
Abstract PDF(842KB) icon1613 icon512
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Combined with existing software and hardware resources,integrative simulation platform for aero-engine digital electronic control system,which mainly includes aeroengine model subsystem,signal simulation and processing subsystem,controller rapid prototyping subsystem was designed with modular approach.Aero-engine model subsystem acts as a numerical simulation platform that calls aero-engine mathematical model library and mechanical hydraulic actuator mathematical model library.Rapid prototyping subsystem for controller runs in Matlab/Simulink environment,in which control code encapsulated into S-Function module.As key techniques in platform software design,mixed programming and WINDOWS timer programming method were described in detail.Applying the platform to a turbofan control system researchment,numerical simulation,semi-physical simulation and bed test results are consistent.It shows the platform is feasible and effective in engineering.
Analysis of fluid solid interaction of hydrodynamic finger seal's working state and its influence
ZONG Zhao-ke, SU Hua
2010, 25(9): 2155-2162.
Abstract PDF(1323KB) icon1739 icon441
Abstract:
The fluid-solid coupling model and calculation method of circumferential convergent hydrodynamic finger seal were established.Numerical simulation of fluid solid interaction was conducted in the process of rotor startup.The time-dependent change of leakage rate and radial force of interface was analyzed.Two parameters,i.e.:leakage rate and radial force of interface,were used to evaluate the performance of finger seal at stable state.These two parameters were calculated and their changes were analyzed in different working conditions and structure parameters of fluid interface.Research shows that leakage rate decreases rapidly and tends to be stable,radial force of interface reaches the maximum and then decreases to be stable at last in the process of rotor startup,meeting the requirements of low leakage and non-contacting finger seal.The work provides a basis for optimizing hydrodynamic finger seal with good performance.

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