2010 Vol. 25, No. 5

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Analytical study of heat transfer of high-temperature and high-velocity flow field behind shock waves
WANG Bao-guo, LI Xiang, HUANG Wei-guang
2010, 25(5): 963-980.
Abstract PDF(5095KB) icon1704 icon598
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Analytical study of thermodynamics and heat transfer of high-temperature and high-velocity flow field behind shock waves is an important problem involving the design and heat transfer analysis of vehicle thermal protection system (TPS).The flow fields of the Apollo AS-202 return capsule aviating in the earth atmosphere of six cases (the Mach number varying from 15.52 to 22.63) and the Huygens vehicle aviating in the Titan atmosphere of six cases (the Mach number varying from 17.29 to 24.47) were simulated by using conservation integral form of Navier-Stokes equations with multi-species,nonequilibrium molecular thermal excitation and chemical reactions,based on the high-resolution total variation diminishing (TVD) scheme.Thermodynamics and heat transfer of high-temperature and high-velocity flow field behind bow shock were studied,and the wall heat flux density,wall temperature and Stanton number were in good agreement with the flight data.These results are useful for design of correlative vehicles'TPS.
Numerical study on film-cooling effectiveness on endwall of a turbine cascade by different film-cooling jet structures
LV Pin, WANG Zi-jian, WEN Jie
2010, 25(5): 981-986.
Abstract PDF(982KB) icon1485 icon423
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Numerical simulation was carried out to investigate the influence on film-cooling effectiveness by different structures,and the flow and heat transfer characteristics on endwall of a turbine cascade at different blowing ratios were obtained. The result shows that the jet of column holes produces a pair of coupling counter-rotating vortices at the downstream of cooling holes by the influence of mainstream and cooling jet. The vortices are disadvantageous to the endwall film-cooling. The forward expansion hole reduces the intensity of coupling vortices. The cooling jet is pushed to the wall. These factors make the cooling effectiveness better than the column cooling holes. The forward expansion leakage increases the width of jet,and cools down the endwall between the film-cooling holes. These factors make the forward expansion leakage better than the column holes and forward expansion holes.
Research on the effects of valveless operations of pulse detonation engine on supply system
QIU Hua, YAN Chuan-jun, XIONG Cha
2010, 25(5): 987-992.
Abstract PDF(679KB) icon1630 icon442
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Experimental research on the effects of valveless pulse detonation engine on supply system was conducted. The pressures at different positions of pipe were measured,and also used to verify the numerical simulation models of fuel pipe and air pipe. Based on the numerical model,flow characteristics of the supply system were investigated. This showed that the influences of the same head pressure on the air and fuel supplies were different. And it caused unsteady filling when the supply system was opened because of differential pressure. The unsteady filling time was fixed and determined by the given supply system. When the working frequency of the engine became larger,the ratio of this time to one cycle time increased,that is to say,more influences of unsteady feeding were imposed on the operation characteristics of the engine. Therefore,the distribution of fuel concentration was more non-uniform and the working state of pulse detonation engine was instable.
Numerical research of turbulent combustion in reversed-type annular combustor
CAI Wen-xiang, ZHAO Jian-xing, HU Hao-sheng, WU Xiao-song
2010, 25(5): 993-998.
Abstract PDF(2439KB) icon2363 icon515
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In the arbitrary curvilinear coordinates,intermediate and final production formations of the reverse-flow annular combustor with swirl cup were numerically investigated by the four-step reaction mechanism. The renormalization group (RNG) k-ε model,eddy-dissipation model (EDM) and discrete-ordinate method were used to simulate the turbulent viscosity,reaction rate and radiative heat transfer,respectively. The stochastic particle trajectory model was applied to simulation of the droplet trajectories,size and temperature history. Discretization equations were solved with pressure implicit split-operator (PISO) algorithm. The three-dimensional two-phase reacting flow fields and profiles of combustion production were predicted on a non-staggered gird system. Calculations are in reasonable agreement with experimental data. It is shown that the numerical methods and models adopted are reliable and can be used to provide technology support for the optimum design and reducing pollutant emission in the reverse-flow combustor.
Numerical heat computation of key equipment of spacecraft in orbit based on STL file and finite element method
ZHANG Tao, SUN Bing
2010, 25(5): 999-1004.
Abstract PDF(2357KB) icon1743 icon404
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Because STL (stereo lithography) file can transfer the information of solid model accurately,a method to compute solid radiation heat flux of spacecraft based on STL file was proposed. The boundary cells were identified according to topological relationship of cells and nodes and on that basis,radiation heat transfer was computed. Computation method of view factors and external heat flux of complicated structure based on STL file and finite element method was expatiated in detail. Coupled computation of conduct and radiation heat transfer with finite element method was researched. Finally,three-dimensional transient temperature field of key equipment of spacecraft in orbit was computed by finite element method (FEM).
Numerical simulation of center-body width in a trapped vortex combustor
LIU Shi-qing, ZHONG Jing-jun
2010, 25(5): 1005-1010.
Abstract PDF(1075KB) icon1834 icon454
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The numerical simulation has been carried out to investigate the effect of the center-body with of different equivalent widths (from 0.3 to 0.8,interval 0.05) in the trapped vortex combustor under four different inlet conditions,so as to select the width of the center-body in the trapped vortex combustor. The results show there is a proper scale of the width to establish the low velocity and steady flow region in the trapped vortex cavity. The total pressure loss at the combustor outlet increases with rising center-body width.
Experiment of impingement heat transfer with film holes bleeding and side bleeding
WANG Ke-fei, ZHU Hui-ren, ZHANG Bin, XU Du-chun
2010, 25(5): 1011-1017.
Abstract PDF(1267KB) icon1920 icon448
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A transient liquid crystal technique was used to measure the local heat transfer coefficients on a target surface with array impingement hole. The effects of jet Reynolds numbers (5000,10000,15000,20000) and the ratios of the side bleeding(0,0.25,0.4,0.6,0.8,1) on the heat transfer coefficients were investigated. Results show that,the heat transfer coefficients on the target surface rise with the increase of jet Reynolds number; the heat transfer coefficients on the impingement stagnation regions are the highest,and the heat transfer coefficients on the film holes regions are also relatively high. The average heat transfer coefficients on the target surface decrease with the increase of the ratio of the side bleeding,and are not strongly influenced with the low ratio of side bleeding,but significantly affected with the high ratio of side bleeding.
Numerical investigation of temperature field in brush seals
LI Li-ke, WANG Zhi-li, SONG Fei, WANG Wei, CHEN Cong-hui
2010, 25(5): 1018-1024.
Abstract PDF(1294KB) icon1681 icon437
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The mechanism of frictional heat generation and heat transfer in brush seals was analyzed and a computational fluid dynamics (CFD) model was developed. In the model,the brush was treated as an anisotropic porous region with nonlinear resistance coefficients and the frictional heat as a heat source. The pressure distribution,velocity field and temperature field were obtained and the maximum temperature under various interference and pressure difference conditions were studied. The investigation shows a steep temperature rise in bristle-rotor interface,which diminishes further away in the radial direction; fluid convection and leakage flow affect temperature distribution deeply. The results can be used to guide brush seal geometry design,contact-pair material selection and interference fit.
Numerical research on aerodynamic characteristics inside single-stage ejection and multi-nozzles infrared system of helicopter
PAN Cheng-xiong, ZHANG Jing-zhou, SHAN Yong, WANG Xian-wei
2010, 25(5): 1025-1030.
Abstract PDF(1262KB) icon1680 icon450
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Three-dimensional numerical simulation was carried out to investigate the internal aerodynamic characteristics insides the single-stage ejection and multi-nozzles infrared radiation suppressor used in the helicopter. Conclusions can be drawn as follows according to the simulation conditions:(1)This kind of infrared radiation suppressor has an impressive ability to pump secondary flow,the pumping ratios for three individual mixing duct differ obviously and the total pressure recovery coefficients are almost the same. (2)The primary flow velocities and pressures at multi-nozzles exit are the same,the important factor affecting the pumping ratio of the individual mixing duct is the secondary flow's smooth level.(3)The decay of the primary flow core velocity and temperature is relative to pumping ratio for three individual mixing ducts.
Design of aerodynamic optimization shape digital model for car and it's wind tunnel test
HE Yi-bin, GU Zheng-qi, LI Wei-ping, JIANG Tao
2010, 25(5): 1031-1035.
Abstract PDF(530KB) icon1583 icon475
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Taking the least aerodynamic lift and longitudinal moment as restriction conditions,a protruding curve of aerodynamic optimization shape,namely,a projection curve of 'lifting section' on the car longitudinal symmetry section was designed; and taking machinery setting and living comfort as geometry restriction condition,an aerodynamic optimization shape with less aerodynamic drag was further created. The wind tunnel test of the shape validates the finite veracity of this method.The method can be used for forepart aerodynamic optimization of car; the result can greatly save wind tunnel test time and the outlay of aerodynamic optimization styling for car.
Gray neural network model of aviation safety risk
WANG Yan-yang, CAO Yi-hua
2010, 25(5): 1036-1042.
Abstract PDF(1026KB) icon1589 icon457
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A non-linear online model of China civil aviation risk was developed by using gray neural network method. Risk model inputs are represented by risk monitoring indicators about China civil aviation safety and output is represented by composite safety index of assessing China civil aviation industry safety. Numerical computation software was programmed based on this model. The agreement of the perception data of computation software with the actual data of composite safety index indicates that,using gray neural network method is correct. Using this risk model,the main influential factors from numerous risk monitoring indicators about civil aviation safety can be found out,and the reasonable proposal can be made for reducing China civil aviation safety risk. On the other hand,analysis of composite safety index of assessing China civil aviation industry safety can be made for providing a warning about China civil aviation safety.
LU-SGS pseudo-time iteration space marching method for solving supersonic chemical reaction flow
HE Xu-zhao, LE Jia-ling, SONG Wen-yan
2010, 25(5): 1043-1048.
Abstract PDF(698KB) icon1736 icon424
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A pseudo time iteration lower-upper symmetric-Gauss-Seidel (LU-SGS) method for solving supersonic multi-species chemical reaction flow was introduced. When solving parabolized Navier-Stokes (PNS) equations by space marching method,the modified LU-SGS method was used in the marching plane until reaching convergence. This plane's results were transferred to next plane and the entire flow field was solved plane by plane. Using pseudo time iteration LU-SGS method to solve the chemical reaction PNS equation,the result has the same level of accuracy compared with those obtained from Navier-Stokes (N-S) equations solved by time iteration method,and the computation efficiency is improved to an order or more.
Numerical simulation of the start and restart performance of a hypersonic inlet
LI Pu, GUO Rong-wei
2010, 25(5): 1049-1055.
Abstract PDF(1982KB) icon1886 icon496
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An unsteady numerical simulation was carried out on the start,unstart and restart performances of a fixed-geometry,axisymmetric hypersonic inlet due to changing free stream Mach number. The influence of cut-back side walls of the cowl on the characteristics of start and restart was analyzed. The results show that,the contradiction between captured mass flow and the flow capacity of the inlet is mitigated by lateral spillage in front of the cut-back side walls of the cowl,which improves the performance of start and restart. The strong interaction between shock wave and boundary layer in the internal duct is like a bottleneck to the start of the inlet.
Study on generalized exergy efficiency of gas turbine based on work potential
HE Xing, SUN Feng-rui, LIU Yong-bao, HUANG Shu-hong
2010, 25(5): 1056-1060.
Abstract PDF(2171KB) icon1601 icon437
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The analytical formula about gas turbine components' generalized exergy efficiencies was derived by using the intrinsic physical meaning of generalized exergy. The relationships were validated in theoretical analysis and numerical calculation based on the criterion that all kinds of efficiencies must be matched simultaneously. The influences of various parameters on the generalized exergy efficiencies were discussed. The results show that the generalized exergy efficiencies are not only closely related with the component efficiencies,but also logically related with other thermodynamic parameters such as pressure ratio. The compressor pressure ratio was optimized by transferring the stored work potential contained in fuel into generalized exergy.
Research on the intelligent design system for investment casting die of aero-engine turbine blade based on knowledge
JIANG Rui-song
2010, 25(5): 1061-1067.
Abstract PDF(1015KB) icon1285 icon470
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To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality.
Robustness research for mistuning identification of blisks from free response information
WANG Shuai, WANG Jian-jun, LI Qi-han
2010, 25(5): 1068-1076.
Abstract PDF(1746KB) icon1586 icon431
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This paper presented a method for robustness investigation of mistuning identification of disks by taking free response parameters as input information. The sensitivity of identified parameters with respect to input parameters was derived,and the different importance of the input parameters could be estimated from the sensitivity analysis results. This method could help to acquire effective input information in practice and also to further evaluate the accuracy of identified results.
Microstructural evolution and modeling for creep deformation of Ni base single crystal
CAO Juan, SHI Duo-qi, WANG Yan-rong
2010, 25(5): 1077-1084.
Abstract PDF(1826KB) icon1618 icon434
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By analyzing the microstructural evolution and creep of NASAIR100 at different stresses in several high temperatures,four dominating parameters of microstructural evolution as well as its relationship with creep curves were found out. While the change of precipitate's thickness and interlamellar spacing during rafting was considered,a microstructural evolution model was established based on the primary rafting model,the deformation process of precipitation,the matrix and the creep curves was obtained. By comparing with the tests,the influence of different microstructural evolution processes on creep curves was given,showing that,if four parameters' change in microstructural evolution at high temperature is considered,the model can simulate the creep of material at different stresses and temperatures preferably and more close to the reality.
Numerical study of failure mechanisms on plasma sprayed thermal barrier coatings
HU Hao-ju, ZHANG Jian-yu, YANG Xiao-guang, LI Zhi-yong, FEI Bin-jun
2010, 25(5): 1085-1091.
Abstract PDF(1132KB) icon1695 icon404
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A numerical simulation of a cylindrical system with plasma sprayed thermal barrier coatings under typical thermal loading was conducted,and the failure mechanisms were analyzed based on the stresses in ceramic coat. It is found that,there are two types of interfacial (transverse) cracking patterns of the ceramic coat:in the cooling process,mode Ⅰ is vulnerable to crack at the peak position of the cosine curve,and mode Ⅱ at the middle position; in the heating process,interface edges are introduced into the ceramic coat/substrate system as a result of the vertical cracks emergence,and the ceramic coat will transversely crack at these positions because of the stress concentration effect.
Method for test and state analysis of simulation results
WU Wen-juan, FU Hui-min
2010, 25(5): 1092-1096.
Abstract PDF(326KB) icon1646 icon390
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A method for test and state analysis of simulation results was presented,which can not only effectively determine whether the simulation results are right or not,but also analyze every state of the simulation results when they are not completely correct,and point out which states have been simulated correctly and which have not. The method for test and state analysis of simulation results can guide the programming and the modification of simulation software system. Furthermore,a table of simulation results test and a table of simulation results state analysis was established,which makes the engineering application of the method more convenient.
Experimental investigation of aerodynamics of turbine blade trailing edge cooling
SUN Da-wei
2010, 25(5): 1097-1102.
Abstract PDF(773KB) icon1420 icon437
Abstract:
This paper presented an experimental investigation the effects of the trailing edge cooling on the aerodynamic performance. The experiments were conducted on the low-speed linear cascade tunnel at Northwestern Polytechnical University. The external aerodynamic characteristics in the 40 percent chord downstream of exit plane were measured using five-hole probe with the different ejection rates. The results showed that the total pressure loss coefficient at the middle spanwise plane increased at first and then it has a decreasing tendency with the increase of ejection ratio. The trailing edge cooling would influence the structure of the turbine cascade outlet flow field. When the ejection rate was 3%,the loss area near the blade endwall would become stronger,but it would become weaker with the 6% ejection ratio. On the whole,the trailing edge cooling had more influence on the profile loss than on the secondary loss.
Aerodynamic performance research of propellers based on CFD technology
XU Jian-hua, SONG Wen-ping, HAN Zhong-hua, YANG Xu-dong
2010, 25(5): 1103-1109.
Abstract PDF(1421KB) icon2170 icon491
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Unsteady compressible Reynolds-averaged Navier-Stokes equations in absolute coordinate system were solved to simulate the flow around propeller for yawing-configurations. A moving chimera-grid methodology combined with multigrid scheme and a fully implicit dual-time stepping method for simulating the viscous flows over propellers were presented. For zero-yaw configurations,the numerical results agreed well with the experimental data; and for yawing configurations,the results were compared with 1P (once-per-revolution) method. Both cases validate the method. The periodical characteristics of propeller performance at different yaw angles provide a guideline for propeller design.
Study of the design method of an improved micro diffuser
CHEN Jie, HUANG Guo-ping, LIANG De-wang
2010, 25(5): 1110-1116.
Abstract PDF(889KB) icon1600 icon441
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The improved micro diffuser was suggested in the design of a 6cm-diameter micro turbine engine MJ-S1. The improved micro diffuser,which is composed of the full blades and splitters in the passage rear,can avoid significant mixing of airflow and air velocity of annular turning bend while reducing Mach number losses. The design method of the improved diffuser was put forward in this paper. The effects of passage area and blade angle on the diffuser characteristic were studied by using the computation fluid dynamic code NAPA. The diffuser has higher performance when the passage area distribution is convex and the blade angle is nearly linear. The calculation results show that the total pressure recovery coefficient of the improved diffuser can approach 0.9,when it is operated in the centrifugal compressor stage.
Numerical simulation of tandem cascades in an aero-engine fan
CHEN Mei-ning, PIAO Ying, WANG Da-lei
2010, 25(5): 1117-1122.
Abstract PDF(1387KB) icon1630 icon495
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Three-dimensional steady and unsteady numerical simulations were carried out for a fan with tandem cascades at design rotation speed. The matching characteristics of the tandem cascades and the corresponding rotor were emphasized. Detailed analysis of the fan flow field led to some preliminary conclusions:the matching characteristic of the tandem cascades and the corresponding rotor is bad near the hub region,resulting in serious airflow separation at the suction surface of the front tandem blade at the root region and big flow loss of tandem cascades. The total pressure loss of the tandem cascades is about 0.147 at design point and 0.215 at near stall point. The loads of the tandem cascades fluctuate intensely with the influence of the corresponding rotor wave.
Experimental investigation of transonic and supersonic aspirated compressor cascades
LAN Fa-xiang, ZHOU Bai-hao, LIANG De-wang, HUANG Guo-ping
2010, 25(5): 1123-1128.
Abstract PDF(943KB) icon1769 icon440
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The experimental investigation of a transonic and a supersonic aspirated compressor cascades was conducted in this paper. The aspirated compressor cascades were designed to improve the blade performance by sucking air on a slot. Various operating states were achieved by changing the slot location,the sucking air mass-flow,the sock location and the shock intensity. Generally,sucking air after the shock and before the separation had some beneficial effects in controlling the boundary separation and decreasing the loss. Then,the loading of blades was improved. The effects were especially prominent when there were strong shocks and strong boundary separations as a result of interaction between shock and boundary. There is a threshold of bleed air output for the transonic cascade,and also a threshold of sucking air mass-flow. Beyond it,suction can reduce the separation,weaken the loss and improve the performance.
Theoretical investigation on water/metal fuel ramjet motor-thermodynamic cycle and thermodynamic calculation
YANG Ya-jing
2010, 25(5): 1129-1138.
Abstract PDF(1482KB) icon1515 icon429
Abstract:
For achieving high-speed requirement of underwater vehicle,a conceptual engine,which utilizes the hydroreactive characteristic of several metals under supercavitation environment,has been put forward. Especially,in order to obtain specific impulse as great as possible,a dual water injection system is taken into account. Then thermodynamic cycle model,which lead the improvement of power plant and energy system,is introduced in detail,and thermal efficiency is also analyzed. Furthermore,for investigating the performance of this kind of engine system,detailed thermodynamic calculation and analysis are achieved. Especially,regarding hydroreactive metal fuel Mg/AP/HTPB as our target fuel-rich propellant,considering its obvious deficient oxygen property and the energy property of magnesium/water reaction,theoretical calculation method is established by integrating chemical non-equilibrium with chemical equilibrium. Accordingly,low limit of primary water/fuel ratio is determined. In addition,the qualitative and quantitative relationship of performance parameters,such as theoretical specific impulse,nozzle exit temperature,characteristic velocity,etc.,versus water/fuel ratio is investigated respectively.
Investigation on thermal environment for deep-space-exploration liquid rocket engine
WEI Chao, ZHANG Zhong-li
2010, 25(5): 1139-1144.
Abstract PDF(1869KB) icon1937 icon426
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The thermal environment for deep-space-exploration liquid rocket engine (LRE) was analyzed. It was found that high heat flux could be eradiated to the explorer from the nozzle of LRE. The thermal resistance material was used to prevent heat radiation onto the explorer. When the engine was coated with thermal resistance material,the nozzle wall temperature could be higher than wall temperatures without coating. The current analysis showed that,the increased nozzle wall temperature was still in the allowable range for engine thermal protection. The computational methods of current paper were validated by hot-fire testing. The results were in good agreement with hot-fire measurements.
Numerical study of plume characteristics of a pulsed plasma thruster
QIAN Zhong, DU Zhao-hui, WANG Ping-yang, YUAN Yi-chao
2010, 25(5): 1145-1150.
Abstract PDF(1118KB) icon1637 icon437
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By taking the plume of a pulsed plasma thruster (PPT) as research object,a three-dimensional physical model in a Cartesian coordinate system was developed,and the electron momentum equation was simplified and discreted to simulate the unsteady flow of plume employing particle-in-cell (PIC) and direct simulation Monte-Carlo (DSMC) hybrid method. Assuming that the propellant particles were injected to the flow field by a sinusoidal rule during a pulse period,the time-dependent profiles of potential,electron,ion and neutral number density were analyzed. Then the simulation model was verified by making comparisons between computational results and experimental data. The research indicates that the model could predict the parameters of the plasma plume in both parallel and perpendicular planes to electrodes. And the research method and findings can provide a reference for further study on PPT plume.
Optimization of grain design for hybrid rocket engine based on hybrid optimization algorithm
RAO Da-lin, LI Xin-tian, TIAN Hui, CAI Guo-biao
2010, 25(5): 1151-1155.
Abstract PDF(924KB) icon1486 icon461
Abstract:
To decrease the performance loss such as specific impulse caused by oxidizer fuel ratio deviation from optimal value during the working process,a hybrid optimization algorithm based on clonal selection algorithm(CSA) and differential evolution(DE) was proposed in this paper,which was called differential clonal selection algorithm(DCS).An optimization model and a scheme for grain design were established,and penalty function was adopted to eliminate the restrictions. The algorithm,model and frame were applied to a hybrid rocket grain design,and the result indicates a good performance of the algorithm and scheme. After the optimization,excrescent propellant ratio and combustor pressure are reduced,the working condition of combustor and nozzle is meliorated,and an average specific impulse increase by 1.2 percent.
Effects of propellant heat groove configuration on solar thermal propulsion performance
YANG Jie, YANG Li-jun
2010, 25(5): 1156-1162.
Abstract PDF(2033KB) icon1839 icon392
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A detailed study of solar thermal propulsion (STP) performance was made using numerical simulation method by changing spiral groove parameter in this paper. The optimum design parameter was gotten according to analysis on STP's thrust,specific impulse and mass flow rate. Advantage and disadvantage of performances were also compared between single and double spiral groove STP. The conclusion provides a guidance to design of STP thrust chamber spiral groove.
Research on fuel supply control law of airstart for an aero-engine
WANG Zhao-ming, WANG Fu-de, ZUO Wei, WANG Chen, BA De-chun
2010, 25(5): 1163-1168.
Abstract PDF(1910KB) icon1597 icon460
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The problem of airstart of an aero-engine was investigated. The enrichment in airstart of an aero-engine exists because the effects of flying height on fuel-feed characteristics are not considered for the original selfstarter. Various factors affecting the fuel-feed characteristics were investigated. A high altitude compensator was added to the original selfstarter to compensate the effects of flying height on fuel-feed characteristics. The mathematical models of original and improved selfstarters were built respectively. The simulations and tests verify the feasibility of the improved selfstarter,e.g.:airstart fuel supply flow decreases as the altitude increases as compared with the ground starter. The improved selfstarter can compensate the effects of flying height on fuel-feed characteristics and resolve the problem of airstart enrichment.
Application of adaptive second-order dynamic terminal sliding mode control to near space vehicle
PU Ming, WU Qing-xian, JIANG Chang-sheng, CHENG Lu
2010, 25(5): 1169-1176.
Abstract PDF(2920KB) icon1713 icon400
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In order to overcome chattering problem,a second-order dynamic terminal sliding mode control scheme was proposed. The terminal sliding mode control speeds up the convergence of tracking error and the second-order dynamic sliding mode control obtains continuous controller in time domain by embedding discontinuous functions into the first-order differential of controller and making the sliding surface and its derivatives equal to zero. Thereafter,a nonlinear disturbance observer was used to approximate compound disturbance. Adaptive compensation term was added to the controller,relaxing the prerequisite of nonlinear disturbance observer. The system was proved stable based on Lyapunov theorem. Finally,the simulation applied to near space vehicle has demonstrated the superiority and effectiveness of the control scheme.
Thrust estimator design based on K-means clustering and reduced least squares support vector regression
ZHAO Yong-ping, SUN Jian-guo, WANG Qian-yu, CHEN Ting-hao
2010, 25(5): 1177-1183.
Abstract PDF(2105KB) icon2075 icon408
Abstract:
In this paper,a design scheme for thrust estimator was proposed based on K-means clustering and reduced least squares support vector regression. Firstly,the K-means clustering algorithm was utilized to cluster the data in the full flight envelope,and the,a sub-estimator was designed in each cluster using the recursive reduced least squares support vector regression (RRLSSVR). In the process of designing the sub-estimator with RRLSSVR,the Cholesky factorization was utilized to replace the original iteration method for achieving higher numerical stability. Finally,the simulation experiments show that the thrust estimator can satisfy the requirement of direct thrust control for aeroengines,and as compared with other scheme for thrust estimator,the proposed scheme in this paper is also superior.
Research of optimal control for electromechanical integrated toroidal drive with regulator
LIU Xin, XU Li-zhong
2010, 25(5): 1184-1189.
Abstract PDF(736KB) icon1739 icon447
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Based on the electromechanical coupled dynamic model of a generic electromechanical integrated drive system,the speed transfer function was obtained,and the state space express of the system with a regulator was derived. Considering the requirement of engineering practice,the theoretical model of optimal control was built,and the optimal control rule was obtained. The Riccati matrix equation was solved,the feedback gain matrix was acquired,and the tracking response and optimal control input were simulated with Matlab software. Finally,the dynamic performance was greatly improved,and the combination of proportion integration (PI) regulator and optimal control was achieved. The results offer meaningful instruction for the practical application of the generic drive system.
Analysis of quasi-dynamic characteristics of compliant floating ring gas cylinder seal
MA Gang, XI Ping, SHEN Xin-min, HU Guang-yang
2010, 25(5): 1190-1196.
Abstract PDF(2023KB) icon1711 icon435
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Based on the service conditions and working principle of a compliant floating ring gas cylinder seal,the key-points of the seal design and analysis were studied and the numerical calculation model was established on rotating reference frame. A quasi-dynamic characteristics analysis method was presented and the seal performance was analyzed quantitatively. Static characteristics of the seal and mechanical characteristics of the gas film were calculated through finite element method. According to the typical service conditions in counter-rotating shafts,the relationship of the seal performance parameters and the film thickness was obtained through numerical analysis and simulation.
Study on the effects of whirling motion of the floating-ring on distribution of oil pressure in a floating-ring bearing
KANG Zhao-hui, REN Xing-min, HE Shang-wen, YANG Yong-feng
2010, 25(5): 1197-1202.
Abstract PDF(983KB) icon1676 icon427
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In consideration of the whirling motion of the floating-ring,the distribution of the oil pressure of the outer squeeze film and the inner squeeze film was studied in this paper. Based on Hirs'bulk flow theory,Moody' frication factor equation and the generalized incompressible Reynolds equation,the transient governing equations of the inner and the outer squeeze film and the equation of the motion of the floating-ring were set up. Using a numerical example,the relationship between the whirling motion of the floating ring and the distribution of the oil pressure was discussed. The result shows that the procession radius decreases as the eccentricity of the rotor increases,and the positive oil pressure zone moves in circumferential direction.

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