2012 Vol. 27, No. 4

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Numerical simulation of the ducted-fan noise with finite thickness
WANG Tong-qing, ZHANG Li-shuang, YANG Bin
2012, 27(4): 721-725.
Abstract PDF(570KB) icon2106 icon671
Abstract:
To analyze the acoustic propagation of aircraft engine nacelle,predicting the acoustic propagation of a varying cross-section ducted-fan with finite thickness,the fast scattering method was discussed.The ability of the method in application to the sound propagation problems with different pipeline thickness of ducted-fan shapes,including the equal circular tube and variable cross-section tube has been demonstrated.If the pipeline thickness is more than 2 percents of the radius,the pipeline thickness should not be ignored in the prediction of the scattering sound field.The present method provides the theory basis for choosing the ducted-fan thickness in the engineering.
Effect of flap length on the performance of single-expansion-ramp-nozzle
TAN Jie, JIN Jie, DU Gang, XU Jing-lei
2012, 27(4): 726-734.
Abstract PDF(808KB) icon1906 icon758
Abstract:
An experimental study of single-expansion-ramp-nozzle (SERN) models has been conducted to investigate how the nozzle flow was affected by the flap length variation at nozzle pressure ratios (NPR) from 4 to 60 under wind off condition.Wall static pressure distributions were obtained.A three-dimensional numerical simulation was also conducted to predict the performance which was unattainable in the test facility of four models with different flap lengths.The results show that the flow exhibits strong three-dimensionality and crossflow separation of the exhaust flow is apparent in the ramp side regions at high NPR.The peak value of the axial thrust coefficient (ATC) increases with the increase of the length of flap;moreover,the corresponding NPR becomes larger and approaches to design NPR.The ATC increases with increasing flap length at NPR between 30 and 80 and the gap between maximum and minimum reaches 1.8% at the design NPR,whereas the model with shorter flap has higher ATC at certain low NPR.The thrust vector angle increases along with the flap length increase,and the maximal and minimal values of the thrust vector reaches 6.03° and -1.83° at the design point respectively.
MHD control of oblique detonation wave front induced by double wedges
SUN Xiao-hui, CHEN Zhi-hua, XUE Da-wen, SHA Sha
2012, 27(4): 735-741.
Abstract PDF(980KB) icon1753 icon556
Abstract:
Based on the requirement of detonation propulsion of the hypersonic aircraft research,both of the structural types of the oblique detonation waves (ODWs) induced by double wedges and the feasibility of its magnetohydrodynamic (MHD) control of oblique detonation wave (ODW) have been investigated numerically,furthermore,the influences of angle variations of the second ramp on the detonation flow field and MHD control have been discussed.The results show that,for the double wedge detonation with the first and second ramp angles of 15° and 20°,respectively,MHD control can return the position of a stable ODW wave front to its designed location,and can also turn the unstable ODW to be stable,but it is unable to return the unstable ODW front back to the desired place.With the increase of the second ramp angle,the MHD control can also return the ODW front under the condition of a stable ODW.However,when second ramp angle is bigger than 25°,the flow field becomes unstable,and it cannot be manipulated.In this case,with the increase of reaction rate,the ODW stability can be controlled again,but there is no way to return its front to the desired location.
Multi-node statics model and aerodynamic characteristics of cross parachute clusters
HAN Ya-hui, YANG Chun-xin, XU Xiao-dong
2012, 27(4): 742-748.
Abstract PDF(811KB) icon1466 icon571
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To calculate clusters’ aerodynamic characteristics for a certain type of disaster relief airdrop system,multi-node statics model of cross parachute system was developed to calculate the aerodynamic shape of canopy.Different cross parachute models were numerically simulated with different canopy arm ratios and suspension line ratios,and the numerical results were compared with test results in literature.According to this model,and aerodynamic shape was obtained for cross parachute clusters,and aerodynamic characteristics were simulated.The results show that:the calculated results and wind tunnel test results in literature are in good agreement,and the multi-node statics model is accurate and feasible.As canopy arm ratio and suspension line ratio of cross parachute increase,the axial force increases;as the angle of attack increases,the axial force firstly decreases and then increases,whereas the normal force increases.This model can be used for calculating aerodynamic shape of parachute clusters,which is also useful for parachute system design.
Flight dynamics characteristic of tilt rotor aircraft
SHA Hong-wei, CHEN Ren-liang
2012, 27(4): 749-754.
Abstract PDF(454KB) icon2378 icon875
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A flight dynamics model of the tilt rotor aircraft was established based on the research into the aerodynamic of the rotors,wing,fuselage,nacelle,empennage and control system.Quasi-steady element theory was used to analyze the lift,drag,moment and the flapping motion of the rotors.The lift line theory was used to research the aerodynamics of others,and then an investigation was conducted on the XV-15 tilt rotor aircraft.The results can be helpful to realize the characteristics of tilt rotor aircraft,also be useful to flight control design.
Numerical simulation and cold-flow test of outflow effect on linear aerospike nozzle
CHENG Cheng, WANG Yi-bai, LIU Yu
2012, 27(4): 755-760.
Abstract PDF(987KB) icon2019 icon634
Abstract:
Finite volume method was adopted to get the simulation results of aerospike nozzle vehicle model for cold-flow test in wind tunnel which was composed of a linear plug nozzle truncated rate 25% and a lift body.Simultaneously combined with test measurements,outflow effect on flow field structure and performance of linear plug nozzle at different heights (pressure ratio) were presented.It is shown that outflow interference results in excessive expansion of jet and increase of the intensity of lateral flow in linear aerospike nozzle,and also affect the restricted flow around plug bottom.Under the low-altitude flight conditions,there is a serious loss of nozzle performance caused by pressure decrease on plug wall and at the bottom,and a vehicle base drag increase due to the existence of outflow.Under high-altitude flight conditions,the loss of nozzle performance mainly caused by vehicle base drag loss is small,because the pressure on plug wall and at the bottom is no longer affected by outflow.
Equilibrium gas effects on aerodynamic characteristics of waveriders
ZENG Wei-gang, LI Wei-dong, HAN Han-qiao, LEI Mai-fang, WANG Fa-min
2012, 27(4): 761-769.
Abstract PDF(763KB) icon2361 icon684
Abstract:
The aerodynamic characteristics of waverider under equilibrium gas condition have been studied by computational fluid dynamics(CFD) method,and the results have been compared with that under perfect gas condition.The analysis reveals equilibrium gas effects on aerodynamics of waverider are due to the decrease of induced pressure of boundary layer,which is caused by the chemical reaction in the boundary layer.In comparison with the angle of attack,equilibrium gas affects little on lift to drag ratio and pitching moment coefficients of waverider,but it has some effects on the pressure center,and the effects are different from that on the reentry vehicle.The results are valuable for the design of gliders based on waverider.
Broadband sound-absorption of perforated lining in the presence of grazing flow
HUANG Wei-xi, HOU Hong, LI Bin, FANG Xian-liang, ZHU Yong-ding
2012, 27(4): 770-776.
Abstract PDF(525KB) icon2393 icon690
Abstract:
For large aperture perforation plate,reducing acoustic mass is a way to realize broadband sound absorption.Meanwhile,the acoustic resistance can be enlarged due to the grazing flow effect as well as the reduction of the acoustic mass.Based on above results,the designing principle was proposed for the parameters of the perforation plate.Besides this,the perforated plate muffler experiment was also conducted.The experimental results show that broadband sound absorption can be achieved for large aperture perforation plate with low acoustic mass in the presence of grazing flow when compared with that of perforated lining without grazing flow.Such perforation plate can be applied to the noise reduction of the aircraft engine nacelle,inlet and exhaust pipe of motor engine,and all kinds of ventilation pipe with large air flow.
Extended incremental Kalman filter method under poor observation condition
FU Hui-min, LOU Tai-shan, WU Yun-zhang
2012, 27(4): 777-781.
Abstract PDF(386KB) icon2204 icon670
Abstract:
A nonlinear incremental measurement equation under poor observation condition was established, and its linearization method was given. Based on this equation, an extended incremental Kalman filter(EIKF)model under poor observation condition and its recursive calculative steps were proposed. Due to environmental factors and the instability of measurement equipments, the measurement data had unknown system errors in engineering. Classical extended Kalman filter(EKF)method cannot compensate and correct the unknown system errors, which produced considerable filter errors and even led to diverge. The presented EIKF method can successfully eliminate these unknown system errors and effectively improve the accuracy of nonlinear filtering. The method is simple to calculate and easy to apply in engineering.
Experiment and analysis on compressive modulus of X-Cor sandwich
SHAN Hang-ying, XIAO Jun, SHANG Wei, LI Ning
2012, 27(4): 782-788.
Abstract PDF(450KB) icon1755 icon626
Abstract:
Analyzing the error between theoretical result predicted by deduced formula and test data of compressive modulus,a modified model which concerned stiffness discount due to structual buckling and Z-pin length diversities was proposed,and stiffness discount mechanism of sandwich was studied.The analytical result of modified model sandwich compressive modulus was in coincidence with the test data.The theoretical formula provided basis for X-Cor sandwich design,and established the foundation for X-Cor’s practical application as a new type of material.
Theoretical and experimental research on impact damping with fine particles as damping agent
DU Yan-chen, ZHANG Ming-ming
2012, 27(4): 789-794.
Abstract PDF(371KB) icon1507 icon637
Abstract:
Based on the mechanical model of elastic-plastic impact between two spheres,the energy absorption ability of two spheres covered by fine particles during elastic-plastic impact process was predicted,the analysis model of the impact damper with fine particles as damping agent (IDFPDA) was built and the damping performance of a cantilevered beam vibration with IDFPDA was simulated.Experimental studies on the cantilevered beam with IDFPDA were also performed,and the results were in good agreement with the theoretical predictions in vibration period,transition point,amplitude response and resonance transfer,which validated the mechanical models proposed.The following conclusions were drawn through the numerical and experimental studies on the IDFPDA:(1) the analysis model of the IDFPDA proposed is reliable;(2) the IDFPDA has good performance in energy dissipation,which is better than single mass impact damper;(3) the IDFPDA is helpful to alleviate the adverse effects of negative damping.
Fatigue life scatter factor analysis for time truncated zero-failure data based on Weibull distribution
ZHANG Yong-bo, FU Hui-min, WANG Zhi-hua
2012, 27(4): 795-800.
Abstract PDF(298KB) icon1569 icon545
Abstract:
A method was introduced for correction of fatigue life scatter factor based on time truncated zero-failure data contributing to Weibull distribution. The formula of scatter factor correction coefficient was defined and proved detailedly following time truncated zero-failure data. For the completed date is basically different from the truncated zero-failure data, their fatigue life scatter factor is significantly different. Therefore, according to the definition of fatigue life scatter factor, five kinds of fatigue life scatter factors was corrected,which based on average life, character life, median life, mini life, max life respectively for two parameter Weibull distribution of time truncated zero-failure data. A comparison of fatigue life scatter factor between the complete data was introduced for analysis, and the results show that the method implied in this paper can fully make use of the information of time truncated zero-failure data,and improve the forecasting precision of safe fatigue life significantly. Also the correction coefficient is easy for calculation and convenient for engineering.
Forced response characteristic of bladed disk with aerodynamic mistuning
XIN Jian-qiang, WANG Jian-jun
2012, 27(4): 801-810.
Abstract PDF(1162KB) icon1734 icon637
Abstract:
The forced response characteristic of bladed disk under fluid excitation with aerodynamic mistuning was analyzed.The resonant criterion of bladed disk and the aerodynamic mistuning theory were performed first.Then, the modal reduction theory and the precise integration method were given.Finally, the transient response characteristics of bladed disk under tuned and mistuned fluid excitations were investigated.In this section,the system mass,stiffness and damping matrix were obtained by FEM(finite element method),and MATLAB code was then used to study the response characteristic.
Investigation of ultra-high cycle fatigue behavior of TC17 alloy at a frequency of 20kHz
GAO Chao, CHENG Li, PENG Hua, SHEN Jing-sheng, QIU Chen-lin, LIU Yan-jie
2012, 27(4): 811-816.
Abstract PDF(572KB) icon1997 icon664
Abstract:
The bending fatigue system was developed using the piezoelectric ultrasonic fatigue testing technology and experimental investigation of the ultra-high cycles fatigue life for TC17 alloy subjected to bending fatigue deformation has been conducted.The experimental resultes show that the specimens were tested to failure in the range of 107-109 cycles and the fatigue limit decreases with the increasing number of cycles between 107 and 109 for R=-1.0 and there was no obvious fatigue limit.The S-N curve for TC17 is a continuous decline curve between 107 and 109 cycles.The fractographic study showes that fatigue failures are mostly initiated at the surface of the test specimens.When there are subsurface inclusions,fatigue cracks initiated from subsurface inclusions,and the composition of inclusions is mainly oxides of aluminums.
Experiment on dry friction damping of shrouded turbine blades
CHEN Xiang, ZHU Jing, Li Guang-hui, Wang Chun-jian
2012, 27(4): 817-823.
Abstract PDF(603KB) icon1743 icon537
Abstract:
A dry friction damping test system of shrouded turbine blades was designed.The effects of different mounting tightness and contact areas between damping block, blade shroud and different materials of damping block on dynamical characteristic and damping of the turbine blades were studied with this system.The results show that damping of the turbine blades is affected by mounting tightness,contact area,materials of damping block and excitation force,which also determin whether the damping system has best vertical press,and dominates its range and domain under the existence of best vertical press.Moreover,change of the excitation force can induce the changing a series of experimental parameters,such as response of the turbine blades,damping ratio of the system,resonance frequency and best vertical press.Those results can provide the experimental verification for theoretical arithmetic and provide further insight into damping design of the shrouded turbine blades.
Experiment on kerosene fueled scramjet ignition by using plasma torch
LI Fei, YU Xi-long, GU Hong-bin, CHEN Li-hong, ZHANG Xin-yu
2012, 27(4): 824-831.
Abstract PDF(564KB) icon1753 icon551
Abstract:
Liquid kerosene ignition was explored in a direct-connected scramjet test facility,that the entrance flow Mach number of the combustor was 2.5,and the total temperature was 1650K.Using a plasma torch with 1.5kW input power,kerosene ignition and sustain combustion realized without any pilot hydrogen.Fuel injection pressure and injector location were investigated as factors affecting the ignition performance.The test results indicate that successful ignition can be achieved when the injectors are located 550mm,upstream the ignition cavity and the fuel injection pressure is between 1.5-2.3MPa.It is also found that higher injection pressure and shorter distance between injection location and the cavity brings negative effects to ignition.Therefore,local fuel-air-ratio is considered as one of the main factors of ignition.Based on the high-speed images of ignition and combustion,it is indicated that the downstream cavity does not advance ignition at the beginning period of the ignition but is very important for sustain combustion and flame propagation.
Numerical investigation of heat transfer characteristics of effusion cooling and machinery film cooling combustors
ZHANG Bo, JI Hong-hu, YANG Fang-fang, ZHENG Mei, CHENG Ming
2012, 27(4): 832-836.
Abstract PDF(441KB) icon1870 icon663
Abstract:
The flowing and heat transfer characteristics of machinery film cooling and effusion cooling combustors were numerically investigated.The results show that in the effusion combustor,heat transfer is enhanced,and temperature of the front wall of combustor increases,while temperature of the back wall decreases,which cause the temperature gradient decrease.The flow efficiency decreases;the amount of cooling gas is reduced by 23% compared with the machinery one.
Numerical simulation of flow and heat transfer in internal cooling blade channel with leading-edge
LIU Yu-sheng, WU Hong, XU Guo-qiang
2012, 27(4): 837-845.
Abstract PDF(1316KB) icon1837 icon539
Abstract:
Flow and heat transfer in approximate real model of blade channel with leading-edge was analyzed by numerical simulation at static condition.The results show:three-dimensional vortices introduced by inclined ribs lead to a great impact on heat transfer in the cavity.Within one rib height range,vortices after ribs occur in both Y-Z and X-Y cross-sections,which makes heat transfer coefficients here in decrease.In X-Z cross-section,the second channel produces a pair of vortices in the opposite direction while the third channel results in just one vortex.Vortices in these two channels occupy the whole cross-section and increase flow resistance.The impingement and film flow play a leading role in heat transfer in leading-edge channel where vortex pair induced by impingement enhances flow mixing and stimulates heat transfer on suction and pressure sides,while high-speed film flow promotes this process.In the same flow conditions,average and local heat transfer on ribbed surface of the second channel perform the best,but the smooth first channel owns the highest comprehensive heat transfer performance due to its minimum total pressure drop in all the channels.With the increasing Reynolds number,local and average heat transfer on suction and pressure sides in each channel are enhanced in contrast with little change in the pressure drop coefficient.
Analysis of dynamic modeling of aviation heavy oil piston engine fuel delivery system
WANG Zhen-yu, DING Shui-ting, DU Fa-rong
2012, 27(4): 846-853.
Abstract PDF(543KB) icon1696 icon651
Abstract:
A complete mathematical model for fuel delivery system used in aviation heavy oil piston engine was developed.The mathematical model included one-dimensional pipe flow module,hydraulic module,mechanical module and electromagnetic module.The nonstationary flow in the fuel delivery system was simulated,including the characteristic of pressure in the system.The injection rate was also provided.The comparison of the prediction results with experimental data showes a generally good agreement,which proves the accuracy of the mathematical model.
Heat transfer enhancement of fin-copper foam composite structure
CHI Peng-tao, GAO Hong-xia, YU Jian-zu, XIE Yong-qi
2012, 27(4): 854-860.
Abstract PDF(858KB) icon1924 icon542
Abstract:
As the fins can significantly enhance the thermal conducting capability along the fin extending direction,the concept of combining fins with copper foam as thermal conductivity enhancer was proposed to satisfy the heat rejection requirements of some high-power electronic components used in the aviation.Fin-copper foam/paraffin samples with fin thicknesses of 0.5,0.8 and 1.0mm were processed.The thermal performances of the samples were tested via steady and transient experiments.The results suggest that the effective conductivity of composite material with 1.0mm fin reaches 11.4W/ (m·K), which is 3.7 times as that of the copper foam/paraffin and 42.2 times as that of the pure paraffin.Under the same heat flux,the maximum temperature differences of the samples with fins are reduced by 73.2%-90.0%.The tests verify that the effective thermal conductivity and the dynamic thermal response of copper foam/paraffin can be remarkably enhanced by fins.A correlation of the non-dimensional coefficients is raised via the experimental results.
Performance test of micro turbojet engine’s evaporator and numerical simulation of the combustor
TAN Wen-long, FAN Wei-jun, ZHANG Tao, WANG Wei-jian, ZHANG Rong-chun
2012, 27(4): 861-867.
Abstract PDF(1520KB) icon2131 icon600
Abstract:
An annular combustor supplied by evaporator for a micro turbojet engine which was used for 40daN level missile was designed.The evaporator’s atomization and evaporation rate data was obtaind by test and then used for the numerical simulation of the combustor.The CFD(computational fluid dynamics) simulation shows the structure of the combustor is reasonable and the performance meets the design point’s requirements.
Influence of structural parameters on performance of monopropellant pulse thruster with high chamber pressure
QIN Li-zi, GUO Zhi-hai, LOU De-quan, LIANG Shu-qiang
2012, 27(4): 868-875.
Abstract PDF(714KB) icon1830 icon628
Abstract:
Due to the movable injector which can be regarded as a differential piston with some spray holes,the pulse thruster can provide much higher chamber pressure than the supply pressure of propellant.In order to analyze the operating characteristics of this type of pulse thruster adopting the monopropellant of HAN(hydroxylammonium nitrate),a lumped parameter model was established and the fourth-order Runge-Kutta method was applied to get its numerical solution which reflected the unique pulsating characteristics.The influence of the structural parameters on the thruster performance such as the area of injection holes,nozzle throat area,displacement and differential area ratio of the movable injector was analyzed and summarized.Though the pulsating operation would come to change when any of the above parameters is altered,the displacement and the nozzle throat area are the most influential and should be optimized firstly in the design progress of the new type of pulse thruster.The average pressure in the combustion chamber and the average specific impulse of the thruster are sensitive to the injector displacement,and the average thrust is sensitive to the nozzle throat area.
Linear instability analysis of a power-law liquid sheet
WANG Feng, FU Qing-fei, YANG Li-jun
2012, 27(4): 876-881.
Abstract PDF(435KB) icon1788 icon504
Abstract:
In order to investigate the breakup behavior of the liquid sheet formed by gelled propellant impinging injector,a linear instability analysis method and the power-law constitutive equation were used.The effects of the liquid properties and rheological parameters on the stability of liquid sheet were studied.The results show that as the consistency coefficient,flow index and surface tension increase,the surface wave growth rate decreases and the wavelength increases.A larger liquid sheet velocity,gas to liquid density ratio and sheet thickness can accelerate the growth of surface wave.The wavelength decreases with the increase of sheet velocity and gas to liquid density ratio,while the opposite is true for liquid sheet thickness.The comparison between the theoretical and experimental results shows that the linear instability analysis method can predict the breakup length well,but the predicted wavelength is larger than experimental results.
Particle swarm optimization of pressure reducing regulator based on uniform design
ZHENG Yun-tao, CHI Yuan-cheng, CHEN Yang
2012, 27(4): 882-889.
Abstract PDF(577KB) icon1706 icon512
Abstract:
The pressure reducing regulator which was the key point of turbo-pump gas-sealed decompressing experiment system was optimized by PSO(particle swarm optimization).Uniform design was used twice before the optimization for the sake of reducing computing quantity.The structure parameters of pressure reducing regulator were optimized to obtain steady outlet pressure meeting engineering requirement.The result indicates that the range of variables was compressed availably through twice of the uniform design.Compared with initial point,the swing of outlet pressure decreases obviously according with engineering design.
Numerical simulation of flow in swirl injector for power-law fluid
WANG Feng, FU Qing-fei, YANG Li-jun
2012, 27(4): 890-899.
Abstract PDF(1227KB) icon1801 icon511
Abstract:
In order to investigate the flow characteristics of swirl injectors for gelled propellants, which actually behaved as non-Newtonian power-law fluid, a swirl axisymmetric model was established to solve Navier-Stokes equations and VOF (volume of fluid) equation, and the power-law constitutive equation was used to describe the rheology characteristics of the gelled propellants. The film thickness and velocity distribution in the swirl injector under different flow conditions were studied numerically. The simulation results show that the increased geometry characteristic parameter of the swirl injector contributes to the decrease of liquid film thickness. The liquid film thickness is almost independent of the pressure drop. The rheologic parameters have great influences on the inner flow of swirl injector: by increasing the fluid consistency index K and power index n, both the axial and the swirl velocities decrease dramatically; higher fluid consistency index K and power index n make the liquid film thickness increase. When the viscosity is large enough, the air core in the injector would vanish.
Development of vacuum plume effects ground simulation experimental system key technology
WANFG Wen-long, ZHOU Jian-ping, CAI Guo-biao
2012, 27(4): 900-906.
Abstract PDF(787KB) icon1708 icon539
Abstract:
The development process of vacuum plume effects ground simulation test facilities from high altitude simulation test facilities to vacuum test system was described.The limitation of ejector principle and the applicability of cryogenic condensation technology were described.The American CHAFF-4(the collaborative high altitude flow facility-Ⅳ) facility,German STG(Simulationsanlage für Treibstrahlenin Göttingen) facility and China’s first large-scale vacuum plume effects ground simulation experimental system—PES (the plume effects experimental system)facility were introduced,all of which were constructed based on the low temperature condensation technology.Details of the initial simulation investigation of PES’s built-in LHe cryogenic pumping were presented along with the results from a direct simulation of Monte Carlo(DSMC).The results demonstrate that,with or without the plume cryogenic pumping,at 2g/s stage thruster working condition,the built-in liquid helium cryogenic pumping can meet the condition that the environment of the back pressure,in the region of ø4m×5m,is less than 10-3Pa,and plume cryogenic pumping can effectively prevent the compression wave from diffusion to the nozzle direction.
Life prediction of cooling passage for reusable liquid rocket engine
YANG Jin-hui, CHEN Tao, JIN Ping, CAI Guo-biao
2012, 27(4): 907-912.
Abstract PDF(481KB) icon1651 icon510
Abstract:
The thrust chamber life is mainly limited by the cooling passage failure,which is caused by fatigue,creep rupture and plastic tensile instability.Based on the analysis of coupled heat transfer and stress,the Porowski method was taken to perform life prediction of the reusable liquid rocket engine cooling passage.The life of nozzle throat liner was mainly determined by the plastic tensile instability,whereas the effect of creep damage can not be ignored in the life prediction procedure.Reducing the temperature difference between the ligament and closeout and increasing the width ratio of each passage or the passage number were all in favor of prolonging the life of cooling passage.The method used for predicting the cooling passage life can provide reliable criterion for the design of reusable rocket engine.
MIMO reconfigurable flight control system design based on sliding mode control
SU Yuan, WANG Ke
2012, 27(4): 913-919.
Abstract PDF(565KB) icon1524 icon503
Abstract:
A frequency domain design method based on sliding mode control for MIMO(multiple input multiple output) reconfigurable flight control system was presented.Combining the sliding mode control with the flight reconfigurable control solved the problems of fault detection and system parameter identification in flight reconfigurable control system.Raised the robustness of the control system to parasitic dynamics and unmodeled dynamics through the introduction of asymptotic observer and hedge model;made the design method become more effective and practical through the introduction of actuator model,output saturation and pilot model;the proposed scheme was applied to the design of lateral motion of an aircraft.The results show that good dynamic performance in the condition of significant changes of aerodynamic parameters and control surface failures.
Study on data bus of open FADEC system
LIU Dong-dong, ZHANG Tian-hong, CHEN Jian
2012, 27(4): 920-929.
Abstract PDF(847KB) icon1791 icon527
Abstract:
The study of fault-tolerant data bus is one of the key technologies for transition from a centralized architecture to a open architecture.The key characteristics of data bus for open FADEC(full authority digital electronic control)system such as consistency,open,transmission bandwidth,scheduling strategies,topologies and fault-tolerant mechanism were studied.Time uncertain problem of bus data transmission was analyzed.The key characteristics of four data bus based on time trigger architecture,which are TTP/C(time-triggered protocol/automotive class C),ARINC659,TTCAN and FlexRay(time-triggered controller area network),were researched from the angle of performance,reliability and availability.The study results show that the TTP/C data buses is the best choice for open FADEC system,and the hardware architecture of modular DEEC (digital electronic engine controller)based on TTP/C data bus was proposed finally.
Performance deterioration mitigation control of aero-engine
LI Ye-bo, LI Qiu-hong, HUANG Xiang-hua, ZHAO Yong-ping
2012, 27(4): 930-936.
Abstract PDF(575KB) icon1768 icon607
Abstract:
The research on PDMC(performance deterioration mitigation control) of intelligent engine was performed.The PDMC consists of both loops,for example,the inner loop controls the rotor speed and the outer loop controls the thrust.As a result,it not only inherits the advantage of traditional control system,but also can realize the direct control of thrust as the direct thrust control.Meanwhile,it enhances the autonomous control of aero-engine.To verify the effectiveness of PDMC,simulations on a two-spool-mixed-flow-turbofan engine were performed.The simulation results show the efficacy and feasibility of PDMC technology.
Nature of tip clearance flow in subsonic unshroud impeller of centrifugal compressor
LIU Zheng-xian, CHEN Li-ying
2012, 27(4): 937-945.
Abstract PDF(1511KB) icon1637 icon522
Abstract:
The tip clearance seriously affects the aerodynamic performance of unshroud centrifugal impeller.The flow field in impeller with three tip clearances was investigated using the numerical simulation method,and then the effect of tip clearance on the aerodynamic performance of impeller,blade loading,flow angle across the tip clearance and the motion of leakage vortex was analyzed in detail.The results indicate different tip clearances have little effect on the blade loading profile,but a value reduction of static pressure from the middle to the trailing age of blade.The flow loss on tip clearance is hardly generated by leakage flow itself.The main flow is disturbed by leakage flow in the second half of the flow channel rather than in the first half.There exist amounts of vortexes near the shroud which cause significant entropy increase which leads to energy loss.The results are hoped to help to develop the aerodynamic model of tip clearance in unshroud centrifugal impeller.
Effect of stator-rotor blade row axial spacing on transonic axial compressor performance
SHI Ya-feng, WU Hu, XU Qian-nan, SONG Shi-ping
2012, 27(4): 946-952.
Abstract PDF(811KB) icon1638 icon554
Abstract:
The steady flow field of stator-rotor blade rows has been numerically simulated,and the computational results show the far axial spacing between blade rows can improve compressor efficiency near the choked mass flow,and the efficiency does not matter with the axial spacing at high loading.The numerical simulation results of unsteady flow field show the close axial spacing can enlarge the interaction of rotor shock on the stator boundary layer and more efficiently suppress the rotor tip double-leakage at high loading which can cause tip blockage and loss.
Aerodynamic performance optimization on S2 analysis code of multi-stage axial compressor
GUO Yi, DU Gang, CHEN Jiang, YIN Hong-shun
2012, 27(4): 953-960.
Abstract PDF(523KB) icon2112 icon549
Abstract:
An aerodynamic performance optimization platform was established for S2 analysis code of compressor by integrating the ISIGHT optimization software and S2 analysis code which calculated performance of multi-stage axial compressor.When a four-stages axial-flow compressor was optimized,the parameters were selected by adjusting blade camber angle,solidity,relative maximum thickness and so on,along radial which have more influence on the objective function just like efficiency to establish the response surface model and integrated evolutionary algorithm to optimize the objective function.The result shows that the whole characteristic of compressor improves,pressure ratio increases 19.6% and efficiency increases 4.66% at design point,stall margin increases to 22.32% at 1.0 equivalent rotor-speed,which proves that building optimization platform has practical value for aerodynamic design of compressor,and can be reference for aerodynamic performance optimization of inner flow tubromachinery.

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