2013 Vol. 28, No. 9

  Previous Issue | Next Issue 
Display Method:
Thermal protection of scramjet typical components
JIANG Jin, ZHANG Ruo-ling, YANG Yang, LIU Wei-xiong
2013, 28(9): 1921-1926.
Abstract PDF(1091KB) icon1492 icon1273
Abstract:
The material selections and thermal-structural designs for the typical passive thermal protection components,such as the cowl leading edges and fuel injection struts,were investigated by the tests on the electric arc heater instrument.The method of thermal-structural analysis for the actively cooled combustor was developed,and the thermal evaluation code validated by the experiments was applied to the combustor material coupon.The cowl leading edges made of materials C1 and C2 were in good condition after 60s test.The fuel injection struts made of material Z1 were in good condition after 50s test.The actively cooled combustor thermal analysis and calculation procedures were applied to the cooling panel tests.The maximum temperature difference between the measurement value and the calculated value was 55K,showing good agreement of the calculation and experiment.So,the calculation program can provide credible reference data for the material configuration design of the actively cooled combustor.The experience and technology learned from the approach will be incorporated into the design and demonstration of complete free jet engine.
Experiment on heat transfer enhancement of barium hydroxide octahydrate phase change material
SHENG Qiang, XING Yu-ming, WANG Ze
2013, 28(9): 1927-1932.
Abstract PDF(1067KB) icon1468 icon1523
Abstract:
The thermal properties of barium hydroxide octahydrate(Ba(OH)2·8H2O) were measured by differential scanning calorimetry(DSC).The DSC measurement method can be used for phase change temperature and latent heat of salt hydrates.The cross section image from scanning electron microscope(SEM) indicates that Ba(OH)2·8H2O and copper present excellent compatibility.Experiments were conducted to investigate heat transfer characteristics of Ba(OH)2·8H2O with/without copper foams.The results show that melting time of the phase change material(PCM) is shortened by 26% in PCM solid zone and the heat transfer rate of the PCM is enhanced.The supercooling degree of Ba(OH)2·8H2O is reduced by 50%.
Experiment of swirled air effect on spray characteristic of double-line pressure-swirl atomizer
ZHOU Bing, JI Hong-hu, ZHANG Bao-cheng
2013, 28(9): 1933-1941.
Abstract PDF(1264KB) icon1458 icon1044
Abstract:
The spray characteristic of the double-line pressure-swirl atomizer with air swirler was investigated using phase Doppler particle analyzer(PDPA).The fuel injection pressure ranged from 0.3MPa to 2.1MPa.The axial air swirler with blade outlet angle of 79°was adopted.The air pressure drop across the swirler ranged from 0.03MPa to 0.15MPa.The change rules of Sauter mean diameter(SMD) and spray cone angle with fuel injection pressure and swirled air velocity were obtained.The results show that in contrast with the situation without swirled air,the spray cone angle increases by 15°~20°and the Sauter mean diameter decreases by 40% which is induced by swirled air under the same fuel injection pressure.
Infrared radiation characteristics of exhaust system using temperature corrected k-ε model
LI Xi-xi, Eriqitai, ZHU Xi-juan, WU Meng
2013, 28(9): 1942-1948.
Abstract PDF(1241KB) icon1560 icon1038
Abstract:
The infrared signal in 3~5μm band of an axisymmetric nozzle was calculated to investigate the improvement of the temperature corrected k-ε turbulence model in the infrared radiation(IR) of exhaust system,and compared with the experimental results.The flow fields and temperature fields of nozzle were simulated numerically by using finite volume method(FVM) and solving Navier-Stokes(N-S) equations,and coupled with the standard k-ε model and the temperature corrected k-ε model respectively.The IR signal was calculated by FVM in non-gray absorbing-emitting media to slove the 3-D radiative transfer equation,and the atmosphere attenuation effect on IR was considered.The results show that the temperature corrected k-ε model can predict the potential core length of hot jet,and consequently the IR intensity agrees with the experiment data.The maximum value of relative error for IR intensity obtained using the temperature corrected k-ε model is 4.3%,while that obtained using the standard k-ε model is up to 64%.This shows that the temperature corrected k-ε model is appropriate for accurate simulation of IR characteristics of exhaust system.
Experiment of heat transfer in oscillating turbulent flow in a pipe with constant heat flux
LI Ming-zhen
2013, 28(9): 1949-1955.
Abstract PDF(1000KB) icon1183 icon922
Abstract:
Heat transfer characteristics of oscillating turbulent air flow in a pipe heated with constant heat flux were experimentally investigated.The experiments were performed over a range of 245.7 to 902 of the kinetic Reynolds number and 25 to 175 of the dimensionless oscillation amplitude.The effects of these two dimensionless parameters were analyzed.The results show that the cycle-averaged local Nusselt number increases with both the kinetic Reynolds number and the dimensionless oscillation amplitude.The space-cycle averaged Nusselt number also effectively increases with the kinetic Reynolds number and the dimensionless oscillation amplitude.Based on the experimental data,a correlation equation of the space-cycle averaged Nusselt number for air in terms of these two dimensionless parameters has been obtained.
Experiment of transpiration cooling rules of single phase liquid
XIONG Yan-bin, ZHU Yin-hai, JIANG Pei-xue, HUANG Zheng, LIU Yuan-qing
2013, 28(9): 1956-1961.
Abstract PDF(916KB) icon1594 icon1115
Abstract:
Sintered metal porous media strut of the scramjet combustion chamber was manufactured to provide thermal protection for the scramjet.Transpiration cooling using water as coolant was studied experimentally.The experimental results show that the heat transfer between the mainstream and the strut wall can be effectually reduced.The cooling efficiency reaches 93% when blowing ratio of 2%.Cooling efficiency increases with the rising coolant blowing ratio,and tends to be 100%.Under two mainstream temperatures,the cooling efficiency at the same measuring points and blowing ratios varies little.Thermal response of the surface temperature of strut after stopping coolant supply was also studied.Water evaporation process was analyzed in three stages.
Numerical simulation of characteristic of hypersonic ablation flow field containing alkali-metal impurities
CHAI Dong, FANG Yang-wang, TONG Zhong-xiang, GAO Xiang
2013, 28(9): 1962-1966.
Abstract PDF(996KB) icon1397 icon1047
Abstract:
As for the ablation of hypersonic vehicles,the parabolized Navier-Stokes(PNS) equations of chemical non-equilibrium were calculated numerically based on a kind of Newton-type iteration method.The chemical model of 18 species 33 reactions containing alkali-metal impurities was established on the basis of a carbon-phenolic ablative material.Firstly,the wall temperature of small blunt cone was computed and the numerical results were validated by comparing with those in a reference.Then,the hypersonic ablation flow field containing alkali-metal impurities were simulated and the effects of ablation reactions on the flow parameters were deeply analyzed.The results show that compared with non-ablation condition,the temperature of flow field increases by 10% to 15% in ablation reactions.And the electron number densities increase by 1 to 2 orders of magnitude after taking alkali-metal Na into consideration.
Self-sustaining mechanism of detonation wave influenced by lateral expansion
ZHOU Zhu-lin, LIU Wei-dong, LIU Shi-jie, LIN Zhi-yong
2013, 28(9): 1967-1974.
Abstract PDF(1236KB) icon1798 icon1006
Abstract:
In order to study propagating characteristics and self-sustaining mechanism of detonation wave influenced by lateral expansion,the influences of different equivalent ratios(0.70-2.25) and different premixed gas heights(1,2,3cm) on the self-sustaining propagation of detonation wave were researched in the test section.It was found that if the premixed gas height is higher and premixed gas activity is stronger,the ability of detonation wave resisting the influence of lateral expansion is stronger and velocity deficits is smaller.Based on Fay's fluid expansion theory,Dabora and Murray's velocity deficits theory and Zeldovich-von Neamann-Döring(ZND)model,the shock wave angle,interface angle and velocity deficits of detonation wave by lateral expansion can be predicted theoretically,proving that experiment is in good agreement with theoretical prediction with Dabora's theory.In order to keep self-sustaining propagation of detonation wave influenced by lateral expansion,the velocity deficit limitation of detonation wave is 7.0%-11.0%.
Numerical simulation and analysis of leaf seal leakage flow
LIANG Ya-kun, WANG Zhi-li, WANG Wei
2013, 28(9): 1975-1981.
Abstract PDF(1076KB) icon1534 icon996
Abstract:
Leakage flow field of leaf seal, seal performance and its influential factors were analyzed based on its structure feature,and fluid dynamics calculative model of sealing zone was built.The velocity,pressure distribution in sealing clearance and leakage were calculated,and the sealing performance with structure parameters in different working conditions was obtained.The result shows that the leakage increases linearly with the sealing pressure,and decreases slightly with the increase of rotor speed;leakage reduces by about 40% with the leaf width from 3mm to 7mm,while it increases by only about 8% with the leaf length from 12mm to 16mm.With the widening gap of the front/back cover plate to leaf or to rotor,the result is also different;the gap from upper cover plate to rotor has greater impact on leakage compared with lower cover plate, with the leakage up to 16%.Leakage and rotor force are also affected by different dip angles of the leaf end.
Mechanism of film cooling efficiency enhancement by horseshoe plasma actuator
DAI Sheng-ji, HE Li-ming, DING Wei, JIN Tao, DU Hong-liang
2013, 28(9): 1982-1987.
Abstract PDF(1131KB) icon1411 icon1082
Abstract:
To disclose the basic mechanism of enhancing film cooling efficiency by plasma actuation produced from horseshoe plasma actuator,numerical simulation was carried out to investigate the flow field for two types of cylindrical holes with/without horseshoe plasma actuator.Results show that the jet flow has acquired expansibility by plasma actuation and the kidney-shaped vortices are changed significantly.With the pull inducement and actinic acceleration of plasma actuation,the coverage area and adherent of jet flow are improved,so the film cooling efficiency was enhanced.The film cooling efficiency of cylindrical hole with horseshoe plasma actuator is larger than that without horseshoe plasma actuator by about 165%(blowing ratio of 0.5),148%(blowing ratio of 1.0) and 500%(blowing ratio of 1.5), respectively.
Numerical calculation of dynamic performance of low-bypass ratio turbofan engine
TIAN Jin-hu, QIAO Wei-yang, PENG Sheng-hong
2013, 28(9): 1988-1996.
Abstract PDF(1383KB) icon1527 icon1084
Abstract:
The dynamic mathematical model and numerical simulation methods of turbofan engine were investigated.The modified engine dynamic performance numerical simulation program could simulate the engine dynamic conditions,such as changes of the inlet parameters,engine maximum rating after burning,engine acceleration and deceleration;then,dynamic performance of low-bypass turbofan engine was analyzed.The numerical simulation results show that engine thrust drops gradually within some accretion range while the inlet parameters change quickly;on the contrary,there isn't thrust surge while the inlet parameters change slowly.History of maximum specific fuel consumption is different while change speed of fuel flux accretion and diminution is unlike.Similarly,the maximum engine thrust and specific fuel consumption may vary with temperature rise.
Correction method of influence of simulation bias on performance of turboshaft engine test in ATF
MA Qian-rong, WU Hu, LIU Tao, ZHOU Wen-xiang
2013, 28(9): 1997-2002.
Abstract PDF(1036KB) icon1406 icon1599
Abstract:
Simulation bias can cause the performance difference during turboshaft engine tests in altitude test facility(AFT).Based on numerical simulation and tests research of a turboshaft engine,a performance correction method of combining the resemble conversion with small deviation analysis was put forward.The results show that the differences of output power and specific fuel consumption were drop from about 3.0% obtained by the resemble conversion to about 1.0%,so this combination method is reasonable and scientific for correcting the influence of simulation bias on the engine performance.
Solving transient second air system in engine by characteristics method
WU Hong, HU Xiao-xiao
2013, 28(9): 2003-2008.
Abstract PDF(1150KB) icon1204 icon1044
Abstract:
The characteristics method was used to solve continuity equation and momentum equation of transient second air system in engine,and the energy equation was solved iteratively.The time-dependent change rules of pressure,mass flow rate and temperature of the flow in second air system were calculated.The result shows that the changes in pressure and mass flow rate of inner nodes vary similarly with the changes of inlet pressure with a corresponding delay time of 0.01s,and the temperatures of elements vary with the boundary temperature.The quasi-static results show good agreement with that of software of Flowmaster,and the maximum relative error of pressure is 0.051%.
Aerodynamic optimization design of wing-body-nacelle-pylon configuration
ZUO Ying-tao, FU Lin, GAO Zheng-hong, SHAO Qi-lin, BAI Jun-qiang
2013, 28(9): 2009-2015.
Abstract PDF(1151KB) icon1469 icon964
Abstract:
A moving grid methodology based on transfinite interpolation(TFI) and radial basis function was adopted for complex configuration.For the problem that may lead to negative jacobian near configuration surface or decline of grid quality,a technology was proposed to remedy the flaw of TFI method:a radial basis function methodology was utilized to achieve the displacements of edges not directly linked to the configuration surface grid,and a linear interpolation was introduced to get the displacements of edges directly linked to the configuration surface grid.An efficient configuration surface grid movement method was introduced via TFI method in case of variation of junction lines.By use of descrete adjoint method to compute the gradient of objective function,wing and nacelle of DLR-F6 wing-body-nacelle-pylon configuration was parameterized and optimized.Tests show that 0.0001 of drag coefficient decline can be gained through optimization considering nacelle's position compared with optimization without considering nacelle's position.Totally,a decrease of 0.00153 aerodynamic drag coefficient can be obtained through optimization.
Tilt-rotor aircraft modeling and its manipulation assignment strategy
XIA Qing-yuan, XU Jin-fa, JIN Kai-bao
2013, 28(9): 2016-2028.
Abstract PDF(2171KB) icon2111 icon883
Abstract:
Nonlinear aerodynamic models and flight dynamic models of the flight test prototype with tilt-rotor were developed by calculating the airframe forces and moments of each component,including rotors,wings,nacelles,fuselage,horizontal tail and vertical tail.Its control characteristics on helicopter mode,the conversion mode and the airplane mode were researched.A manipulation assignment strategy of full-mode flight was presented based on the results of the trim value and the small perturbation linearized model.A difficult problem,involving aerodynamic structural components change and the manipulation redundancy with the change of flight mode in the process of flight control was overcome.A unified flight controller was designed with the help of the manipulation assignment strategy,without need to design a controller for different flight modes.The design difficulty of the flight controller was effectively reduced.Simulation results demonstrate the credibility of the tilt-rotor aircraft flight dynamics model and the effectiveness of the manipulation assignment strategy.
Regression study of scramjet nozzle performance oncontour parameters
ZHANG Wen-dian, WANG Yi-bai, LIU Yu, QIN Li-zi, ZHANG Xiao-yuan, HE Miao-sheng
2013, 28(9): 2029-2036.
Abstract PDF(1010KB) icon1559 icon945
Abstract:
In order to study the influence rules of contour parameters on the performance of cubic curve shaped scramjet nozzle, contour parametric study was conducted by introducing methods of uniform design and regression analysis, and the regression model of scramjet nozzle performance with contour parameter was obtained. The results show that most contour parameters have interactive influence on nozzle performance, but the influence of lower wall height on nozzle lift characteristic could be neglected. Meanwhile, the thrust performance could be improved with the increase of the lower and upper wall exit height. Upper wall length has positive influence on lift performance, contrary to upper wall exit height and angle. The upper wall exit height's correlation with pitch moment performance is similar to lift. The upper wall inlet angle has positive correlation with pitch moment performance while outlet angle has negative correlation in most situations. And within certain range of lower wall's curtailment, it has no significant effect on upper wall pressure distribution.
Numerical simulation of flow field and handling aerodynamic characteristics of ram-air parachute
ZHANG Chun, YANG Qian, YUAN Meng, CAO Yi-hua
2013, 28(9): 2037-2043.
Abstract PDF(1158KB) icon1426 icon1027
Abstract:
The aerodynamic characteristics of ram-air parachute were numerically simulated to analyze flow field mechanism and handling aerodynamic characteristics.Finite volume method was used to solve Navier-Stokes(N-S) equations and shear stress transport(SST) k-ω two-equation turbulence model was applied to simulate the turbulence.The lift-drag characteristics agreed with the wind tunnel data,and the influences of leading edge cut,arc anhedral and static panel on the lift-drag characteristics were studied.The unsteady features of ram-air parachute were calculated by software Fluent to study unsteady lift characteristics and the phenomenon of lift coefficient pulsation was caused by unsteady detached eddy.When angle of attack is equal to 16°,the cycle of lift coefficient is 0.36s.Finally,the longitudinal static stability of ram-air parachute in steady gliding stage was analyzed and two different patterns of turning were compared.Compared with the method of edge deflection on one side,the method of closing intakes port on one side is more stable and effective.
Bistable vibration characteristics of disk-rod-fastening rotor with squeeze film dumper
CHENG Li, LI Shuai-ying, QIAN Zheng-wen
2013, 28(9): 2044-2049.
Abstract PDF(1073KB) icon1378 icon851
Abstract:
The disk-rod-fastening rotor dynamics model with squeeze film dumper(SFD) was built,and nonlinear differential equation method with multiple periodic solution was used to solve those equations with different combinations of system parameters;the influence law of bistable vibration characteristics of disk-rod-fastening rotor with SFD was studied,and the models' dynamic characteristics of stable system periodic solution with and without SFD were compared.The frequency spectrum analysis shows that the disk-rod-fastening rotor without SFD presents fundamental frequency vibration on bistable state,but that with SFD presents frequency multiplication besides fundamental frequency vibration.
Multiple damages detection of structure based on hierarchical genetic algorithm
FAN De-li, ZHENG Shi-jie, WANG Hong-tao
2013, 28(9): 2050-2054.
Abstract PDF(879KB) icon1269 icon876
Abstract:
On the basis of a hierarchical genetic algorithm(HGA) and the idea of structural optimization,a method for multiple damages detection of an Euler-Bernoulli beam and a 2-D plate structure was presented.The algorithm employed control genes to represent the number and location of multiple damages and parametric genes to denote damage extents, effectively avoiding the premature phenomenon of conventional genetic algorithm(CGA).The results of a cantilever beam and a 2-D cantilever plate simulation examples show that the good agreements with the actual situation can be obtained by using the present method,but CGA can't accurately predict multiple damages of the plate.For the simulation of the cantilever beam,the average values of depth prediction errors for HGA and CGA are 0.144% and 1.819%,respectively. The iteration numbers of finite element computation of HGA are only 16.4% of that of CGA.Compared with CGA,HGA remarkably improves the computational efficiency,accuracy and stability.
Literature survey of rub-impact model and experiment of rotating blade and casing
MA Hui, TAI Xing-yu, LI Huan-jun, WEN Bang-chun
2013, 28(9): 2055-2069.
Abstract PDF(1753KB) icon1475 icon1076
Abstract:
By combining with contact and impact dynamic theories,the development about rub-impact between the rotating blade and casing was summarized.Different blade-casing rub-impact models were discussed emphatically and researches of the blade-casing rub-impact model were divided into five types:normal rub-impact model based on the collision energy conservation,smearing and abradable blade-casing rub interface models,continuous elastic collision force model,pulse force local rub-impact model,rub-impact model based on contact dynamics.The defects and proper scopes of these five types of models were pointed out by comparing with one another and the experiments on blade-casing rub-impact were also introduced.Finally,new research directions about the blade-casing rub-impact models were suggested:establishment of detailed normal and tangential rub-impact models including the influence of multiple parameters,collision process simulation based on contact theory,revision of existing rub-impact models by the experiment data.
Experiment on single bolted joints in laminates under multilevel fatigue loading
WANG Dan-yong, WEN Wei-dong
2013, 28(9): 2070-2075.
Abstract PDF(867KB) icon1340 icon876
Abstract:
A series of quasi-static tension experiments and constant amplitude tension-tension fatigue experiments for researching the multilevel fatigue behavior under real cyclic loading were performed on single bolted joints in laminates with the ratio of the width of the laminate to the diameter of the central hole being 3 and the ratio of the distance between the central hole and the end of joint to the diameter of the central hole being 3. Real damage types and failure rules of single bolted joints in laminates were also discussed to provide the basis of stress level selecting of multilevel fatigue experiments.Finally,an experimental program of researching fatigue behavior under two-level fatigue for low-to-high and high-to-low loading sequence was conducted.Fatigue damage index was calculated and analyzed by using the classical linear progressive damage method of Miner rule.The results show that the fatigue damage index is larger than 1 when the loading sequence changes from low-level to high-level.On the contrary,the fatigue damage index is less than 1.
Effect of mistuned bladed-disk induced by cracked blades on vibration characteristics of aero-engine
ZHANG Huan, ZHU Jing, LIANG En-bo, TENG Guang-rong
2013, 28(9): 2076-2082.
Abstract PDF(1295KB) icon1409 icon1033
Abstract:
The performance test of an aero-engine assembled with a mistuned bladed-disk induced by cracked blades was researched.The casing vibration data were analyzed to investigate the effect of mistuning on rotor-dynamic characteristics of the aero-engine.The relationship between crack length and aero-engine vibration characteristic was compared.The results prove that cracking induced mistuning not only modifies the vibration frequency composition of the rotor,but also amplifies the response amplitude of each frequency.However,areo-engine vibration characteristics are not sensitive enough to bladed-disk mistuning if the crack length ratio is less than 0.3,so this is helpful for crack diagnosis in aero-engine tests.
A parametric lightweight turbine disk structure CAD/CAE integration method
LUO Bin, DING Shui-ting, LI Guo
2013, 28(9): 2083-2089.
Abstract PDF(1096KB) icon1264 icon893
Abstract:
The relevance between input parameters and the files of parametric computer aided design(CAD)/computer aided engineering(CAE) integration was analyzed based on the lightweight turbine disk structure's characteristics.C/C++ program was compiled,and software UG/OPEN API was used to accomplish parametric modeling.CAE softwares were called sequentially to run the scripts modified based on one-way fluid structure interaction method to insure the relevance between input parameters and relevant files.Thus,the automated integration of parametric lightweight turbine disk CAD/CAE process was achieved.The program running results show that compared with the manual work which is the same with CAD/CAE process,this method costs less than 54 min,proving that the design and analysis efficiency is improved effectively.
Bi-directional evolutionary structural optimization method based on self-adaption and random sampling sensitivity analysis
SONG Jian, WEN Wei-dong, ZHANG Hong-jian
2013, 28(9): 2090-2099.
Abstract PDF(1359KB) icon1437 icon946
Abstract:
In order to solve the issue of periodic structural topology optimization with design-dependence,the self-adaption strategy and random sampling method were developed,and a topology optimization approach called bi-directional evolutionary structural optimization(BESO) using self-adaption and random sampling sensitivity analysis was proposed based on traditional BESO method.It is also suitable for the non-periodic structures.Based on the approach,the Michell truss structure topological optimization design was carried out,and the optimum structure was obtained in consistence with the theoretical solution.The mass was reduced by 71.5%,compared with the initial structure,showing the proposed method is reasonable;moreover,the multi-web fan disk was designed by the above method,and a new three-web fan disk was obtained.The mass declined by 17.21% in relation to the reference fan disk.The results further illustrates that the method has the ability to cope with the complex issue of periodic structural topology optimization.Additionally,the prone oscillation problems of classical BESO method has been overcome by the algorithm.
Influence of fuel injection position and equivalent mixture ratio on chemical non-equilibrium effects of single expansion ramp nozzle
CHENG Cheng
2013, 28(9): 2100-2111.
Abstract PDF(1445KB) icon1512 icon968
Abstract:
Chemical non-equilibrium flow was investigated for the scramjet single expansion ramp nozzle(SERN) with a strut-based liquid-kerosene-fueled combustor.Two-dimensional Reynolds-averaged Navier-Stokes(RANS) equations were solved with the species conservation equation for continuous phase and the renormalization group(RNG) k-ε turbulence model.Lagrangian discrete-phase model was analyzed for liquid-kerosene droplets behavior in the supersonic stream.Combustion was simulated by kerosene surrogate fuel's 10-species and 13-step reduced reaction kinetics mechanism with use of Arrhenius's laminar finite rate model.Parametric studies were carried out to estimate the influence of different fuel injection positions and equivalent mixture ratios on the SERN chemical non-equilibrium effects.Numerical calculation results show that the strut-based combustor enables convenient modeling of various SERN entry conditions,which is similar with many preceding investigations,by changing the injector strut position and controlling the mass flow rate of each injector.Chemical non-equilibrium effects function in the whole SERN,especially in the initial flow expansion region,leads to obviously higher SERN performance of the non-equilibrium flow than that of the frozen flow.Furthermore,the distributed fuel injection pattern plays a significant role in enhancing the combustion efficiency in combustor,but weakening the chemical non-equilibrium effects funciton in SERN.Additionally,while the equivalent mixture ratio increases,the SERN thrust coefficient and lift coefficient rise gradually,and the increment of non-equilibrium flow in relation to frozen flow becomes higher as well.To be specific,the equivalent mixture ratio is 0.6,the maximum increment of thrust coefficient and lift coefficient are 11.6% and 25% respectively.
Research on stability of reverse unloading diaphragm pressure reducing regulator using BP neural network model
CHEN Jing-lu, WANG Yong-jun, CHEN Yang
2013, 28(9): 2112-2120.
Abstract PDF(1417KB) icon1360 icon859
Abstract:
Back propagation(BP) neural network model was used to study the dependency between the structural parameters and the stability of reverse unloading diaphragm pressure reducing regulator(PRR).The stability of PRR obtained by adjusting structural parameters,in particular,multi-structure parameters,proves that the stability of PRR is very sensitive to the diameter of damping orifice and the stiffness of diaphragm, and also relatively sensitive to the damping coefficient of springy elements material and the effective length of the low-pressure chamber.Thus,various measures for improving the dynamic stability were proposed, including increasing the diameter of damping orifice,the stiffness of diaphragm,the damping coefficient of springy elements material within a certain range(6.5 times of standard value), the effective length of the low-pressure chamber and reducing the mass of valve spool.The BP neural network model tested by the error analysis of the numerical experiments does not show any phenomenon of over-fitting and local optimum.The predictions of the model are reliable,which can be used to support the decision for the design of the PRR and system analysis.In addition,the model is applicable for different data sets,and can be used to study the dependency between the structural parameters and the performance of other components.
Analysis on variable nozzle turbine performance influenced by multiple factors under pulsating flow conditions
ZHANG Rui, SHI Xin, YANG Ce, MA Chao-chen, QI Ming-xu
2013, 28(9): 2121-2128.
Abstract PDF(1234KB) icon1325 icon1069
Abstract:
To improve the matching between the turbine and engine,computational fluid dynamics(CFD) methods were adopted to investigate the unsteady performance of variable nozzle turbine influenced by pulsating flow frequency,pulsating flow amplitude,nozzle vane angle and turbine rotating speed.Results show that the turbine instantaneous minimum mass flow rate under 80Hz condition is 10.4% higher than that under 40Hz condition,and the lowest efficiency increases by 4.7%.At high pulsating frequency,the unsteady efficiency apparently lags behind velocity ratio.Under pulsating amplitude of 25kPa condition,the swallow capacity and efficiency recover rapidly,indicating that it is possible to design turbines by steady flow hypothesis under low amplitude conditon.For nozzle angle of 32 degree, the mass flow difference between pulsating inlet flow condition and steady inlet flow condition is 3.3% more than that of 10 degree, and the efficiency difference is 6.6% more.Higher nozzle angle makes turbine flow field more pulsative and results in mass flow rate and efficiency dropping significantly.Under turbine rotating speed of 47256r/min condition,the mass flow rate and efficiency variation caused by pulsating inlet flow is 2.9% and 0.8% more compared to that of 30000r/min.The turbine flow field is more sensitive to turbine inlet condition when rotating speed is high,and the mass flow rate,efficiency and attacking angle deviate from equivalent steady values.
Experiment of flow separation control in highly loaded compressor cascade corner by endwall plasma aerodynamic actuation
ZHAO Qin, WU Yun, LI Ying-hong, ZHAO Xiao-hu, ZHANG Hai-deng
2013, 28(9): 2129-2139.
Abstract PDF(1469KB) icon1824 icon922
Abstract:
To discover the flow characters and main influencing rules of flow separation control in highly loaded compressor cascade corner by endwall plasma aerodynamic actuation(PAA),microsecond pulse and nanosecond pulse plasma flow control experiments under different flowfields and actuation conditions were carried out.Results show that PAA on the endwall can effectively prevent the flow separation in cascade corner,and actuation effects drop with the increase of angle of attack,but become best at angle of attack of 3 degree;microsecond discharge PAA effects drop with the increase of freestream velocity but increase with the increase of the actuation voltage and duty cycles,and the optimum unsteady pulsed excitation frequency is 500Hz;compared to microsecond discharge PAA,nanosecond discharge PAA is more effective at higher freestream velocity;nanosecond discharge PAA effects are improved with the rising actuation voltage;the actuation frequency is of vital importance,and the effects are improved with the increase of actuation frequency,but when the actuation frequency is 5kHz,the effects will drop.
System-in-package technology for miniaturization design of aero-engine electronic control system
LIU Bao-hua, HUANG Jin-quan
2013, 28(9): 2140-2144.
Abstract PDF(1116KB) icon1599 icon973
Abstract:
An advanced technology of system-in-package(SIP) was presented for miniaturization of the aero-engine control system's electronic equipments.The circuit design of an aero-engine electronic control system was taken as an example.In the chip, an integrated approach was adopted based on a pile of integrated chips,and internal die pins were led to the connection points on the circuit underlay;then the surrounding was supplemented by printed circuit board;finally a complete electrical system was constituted.Design optimization and signal integrity simulation were implemented for quality control of signals.The test results show that,by use of SIP technology,the circuit board is reduced about 80% in area and 70% in mass as well as the signal quality is satisfied.The research illustrates that the SIP technology becomes one of the development directions of miniaturization and high reliability design of aero-engine electronic control system in the future.
High stability control of engine based on surge margin estimation model
WANG Jian-kang, ZHANG Hai-bo, CHEN Ke, SUN Feng-yong, ZHOU Xiao
2013, 28(9): 2145-2154.
Abstract PDF(1634KB) icon1909 icon1250
Abstract:
In order to solve the immeasurable problem of engine surge margin in super-maneuvering flight,an approach to build an engine surge margin estimation model was proposed.The modeling process consists of two parts:surge margin benchmark value model under routine flight condition and surge margin loss value model under super-maneuvering flight condition.The benchmark value model was developed using nonlinear fitting method,and the input of model was fixed by surge margin feature selection algorithm.The surge margin loss value was obtained by an angel of attack predictive model which can be used to real-timely estimate engine inlet distortion index.Based on the predictive messages of surge margin estimation model,a scheme of high stability engine control through correcting turbine expansion ratio command was designed for super-maneuvering flight.In this way, the great advantage is that the original closed-loop doesn't need changes.Finally,some surer-maneuvering flight missions with large angle of attack were imitated.The simulation results show that surge margin ranges between 11% and 13% with above stability control concept,ensuring that engine can work safely and efficiently.
Calculation of mean friction coefficient in scuffing strength for gear drive with meshing beyond pitch point
SUN Yong-zheng, ZHU Ru-peng, BAO He-yun
2013, 28(9): 2155-2160.
Abstract PDF(1094KB) icon1106 icon1041
Abstract:
The shortcomings in current method of mean friction coefficient calculation of scuffing strength were analyzed.Based on the meshing characteristics of gear drive with meshing beyond pitch point and the formula of involute cylindrical gear in related standard, a more reasonable and accurate calculation method of mean friction coefficient was proposed to meet the need for calculation of scuffing strength of the gear drive with meshing beyond pitch point.Through calculating the examples of external-meshing and internal-meshing gear drive with meshing behind and before pitch points, it was found that errors of mean friction coefficients are more than 18.5% except external-meshing gear drive with meshing before pitch point, when they are calculated by standard formula;all of errors are less than 6.5% when they are calculated by improved formula,which confirms that the improved calculation method of mean friction coefficient is more accurate.This calculation method is also applicable to the normal transmission of gears.

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

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