2008 Vol. 23, No. 12

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Essential characteristic of foreign object damage tolerance design for airfoils in aeroengine and development of design criteria
HU Xu-teng, SONG Ying-dong
2008, 23(12): 2153-2161.
Abstract PDF(750KB) icon1714 icon513
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Through the analysis of foreign object damage(FOD) and failure characteristic of fan and compressor airfoils,it was concluded that vibratory stress design and control of airfoils according to reduced material allowable due to FOD is the fundamental feature of FOD tolerance design.Then,by the analysis and review of specifications and standards for aeroengine,the development process of FOD tolerance design criteria was divided into three phases.In the first phase(1950s'-1960s'),FOD related failures were mainly regarded as prevention and maintenance problems.During the second phase(1970s'-1990s'),FOD tolerance design was equivalent to withstand to a notch with a stress concentration factor(Kt) not exceeding 3.0 at the most critical locations of flow path components.Since 2000,a probabilistic design criteria has being in its development phase and has obtained great progress.Finally,some advice was put forward on the research directions of FOD tolerance design technology in China.
Thermeset coupling analysis and optimization design of turbine cooling blade
SUN Jie, SONG Ying-dong, SUN Zhi-gang
2008, 23(12): 2162-2169.
Abstract PDF(977KB) icon1868 icon470
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According to the thermeset coupling analysis and approach of turbine blade optimization based on genetic-finite element method,an optimization design method about the integration of thermeset of turbine cooling blade was persented.By modeling the rotor blade of gas engine turbine,the influence of the position,shape(circle and rectanglar),size and number of cooling holes on thermal stress and cooling effect of turbine blade were investigated.It is proved that the developed method can effectively reduce the stress of turbine blade,and rectangular cooling hole has more cooling effect and smaller stress,the higher temperature of blade is decreased with the increase of size and number,but the max stress is rised.
Knowledge acquisition for aero-engine wear fault diagnosis based on rule extraction from neural networks
CHEN Guo, SONG Lan-qi, CHEN Li-bo
2008, 23(12): 2170-2176.
Abstract PDF(716KB) icon1930 icon474
Abstract:
In view of the problem that it is difficult to understand the knowledge and diagnosis process in intelligent and expert systems based on neural network,a new rule extraction method from neural network based on the functional point of view was studied,and the flow and the key algorithms of the new method were introduced.The UCI(University of California Irvine)machine learning data were used to analyze and verify the rule extraction method.Finally,this method was applied to aero-engine wear faults diagnosis.237 spectral oil analysis samples were acquired from practical aero-engine,the rules extraction from NN(Neural netwoks) method was used to extract the diagnosis knowledge rules,the extracted rules were explained and analyzed.The results fully show the correctness and rationality of the new method.
Response analysis of fluid and solid coupling characteristics for a wide-chord hollow fan blade
WANG Ying, TAO Zhi, DU Fa-rong, HAO Yong
2008, 23(12): 2177-2183.
Abstract PDF(1215KB) icon1912 icon508
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By using the numerical simulation method,the transient response of a wide-chord hollow fan blade was investigated under the atmospheric flow field.The deformation response of the wide-chord hollow fan blade was obtained under unsteady boundary conditions with the fluid-structure interaction numerical simulation method.Computational results show that,under the action of the air flow field,the largest displacement occurs in the top of the front blade and the stress concentration is resulted from the superposition area along the spanwise direction including blade and core,with the stress decreased gradually from surface to inner of the blade.The stress concentration occurs in the blade surface while the distribution stress is relatively small and the core is relatively thin.The modal shape of the blade structure has not been well distributed along the circumferential direction due to the coupling effect between the aerodynamic force and the blade structure.When the fan blade is under fluid-solid coupling,the bending vibration is significant and close to the first-order vibration mode.
Optimization design of crystallographic orientation in single crystal turbine blade
QING Hua, JIANG He-fu, WEN Wei-dong, WU Chang-bo, HU Ren-gao, QIN Zhi-xian, SUN Jing-guo
2008, 23(12): 2184-2189.
Abstract PDF(823KB) icon1882 icon486
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A two-damage-variable creep constitutive model was used to analyze the creep deformation of nickel-based single crystal turbine blades.Based on multidisciplinary design optimization theory,the crystallographic orientation optimization was performed by ASA(adaptive simulation annealing) and NLSQP(non-linear sequential quadratic programming) algorithm.The analysis results show that controlled orientation and uncontrolled orientation have profound influence on creep deformation of single crystal turbine blades.The minimal radial displacement of blade tip is 0.07774mm,when one of uncontrolled crystal orientations is 76.2° in one dimensional optimization state.The optimization amplitude is 2.0%.The minimal radial displacement of blade tip is 0.07378mm,when two uncontrolled crystal orientations are 63.7° and 81.4°,respectively in two dimensional optimization states.The optimization amplitude is 5.4%.The radial displacements of blade tip are 0.07929mm and 0.09352mm when the controlled orientations are 0° and 10°,respectively.The amplitude variation is 17.9%.
Grade-life model of rolling bearing based on support vector machine
MIAO Xue-wen, TIAN Xi-ming, HONG Jie
2008, 23(12): 2190-2195.
Abstract PDF(1756KB) icon1650 icon483
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Grade-life was used to describe rolling bearing's service life,showing the entire service life is divided into four stages: good bearing condition,initial defect condition,damaged bearing condition and upcoming failure condition;an assessment model was presented for bearing's grade-life.Signal feature extraction and pattern recognition algorithm were crucial to construct the model.Vibration signals of the rolling bearing were analyzed,and the wavelet packet analysis theory was adopted to extract the grade-life characteristics.Through signal reconfiguration with wavelet package to extract energy feature of various frequency bands acting as the life feature vector,the support vector machine was used to realize the mapping between the grade-life vector and the grade-life of rolling bearing,and the model of establishing the identification model by using bearing test stand run-to-failure data as learning samples was employed.The validity and creditability of model has been demonstrated by bearing test stands.
Influence of fiber Poisson contraction on matrix cracking development of ceramic matrix composites
LI Long-biao, SONG Ying-dong, SUN Zhi-gang
2008, 23(12): 2196-2201.
Abstract PDF(2008KB) icon1613 icon474
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The influence of fiber Poisson contraction on matrix cracking development of ceramic matrix composites under unidirectional tensile was studied in this paper.The micro stress field was analyzed by combining the Coulomb's friction law and the Lame formulation.The matrix cracking development was determined by the critical matrix strain energy criterion and the fracture mechanics interface de-bonding criterion.The influence of interface friction coefficient,fiber Poisson ration,interface de-bonding toughness and the fiber volume fraction on the interface de-bonding and matrix cracking development was discussed in this article.The present analysis was compared with the results under the assumption of the constant interface shear stress.
Forced vibration analysis of turboshaft engine
CAI Xian-xin, LIU Yu-hui, ZHAO Yan-yun
2008, 23(12): 2202-2207.
Abstract PDF(637KB) icon1348 icon488
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The forced vibration problems of a turboshaft engine,which is mounted directly on the main gear box,were investigated.The characteristic of the engine structure and the source of the exciting force were analysed,and the distribution states of the axial force and bending moment caused by the vibration were also discussed.The mechanical vibration method and finite element method were applied to the forced vibration.The results of the full engine vibration experiment show that the proposed procedure is efficient.
Numerical simulation on blade loss caused by bird-impact and casing containment
JIANG Xiang-hua, WANG Yan-rong, GUI Xing-min
2008, 23(12): 2208-2213.
Abstract PDF(1373KB) icon1703 icon487
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Bird impact on an aeroengine rotating stage may cause the blades split and hit the engine casing subsequently.This phenomenon was studied here by using MSC software.The result shows the entire blade loss involving large mass provides a high possibility of punching through the casing.This rushing blade may collide with other blades and trigger new blade loss and containment problems(secondary damage).Partially broken blade loss could also exist,but this kind of accident is less critical at most of time,which usually can not break the casing nor trigger any secondary damage.The wide coexistence of swift movements,large deformations,unrecoverable breakages and energy exchange processes will make this process much more complicated.
Characteristic analysis of frequency veering and mode interaction of bladed disks
WANG Hong-jian, HE Er-ming, ZHAO Zhi-bin
2008, 23(12): 2214-2218.
Abstract PDF(637KB) icon1494 icon428
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Frequency veering in a bladed disk is the result of system mode interaction,which will greatly affect the vibrational characteristics of the system.In view of system modal power,the expressions of various sub-mode powers were derived from the eigenfunction of a bladed disk in this paper.By using a lumped parameter model,the characteristics of frequency veering and variations of sub-mode powers were systematically investigated.While studying comprehensively the variation features of the mode interaction power of the bladed disk,the interaction between frequency veering and variations of sub-mode powers was thoroughly analyzed and summarized.This method and conclusion could provide a fundamental theory for looking into the physical insight of frequency veering of a bladed disk.
Fault detection of early rotor rub-impact based on cross-correlation and chaos oscillator array
GUO Yang-ming, ZHAI Zheng-jun, JIANG Hong-mei, MA Jie-zhong
2008, 23(12): 2219-2223.
Abstract PDF(1725KB) icon1465 icon473
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In order to improve the veracity and effectiveness of the early fault detection,the method of early detection method of weak fault signals with multi-character frequencies was proposed through array scan,by employing cross-correlation for denoising and building chaos oscillators array.In this method,the denoised signals were sent to the chaos oscillator detection array to act as a part of the chaos detection system's periodical driving force,and then the weak fault signals could be detected from the system's phase locus change.Its feasibility is verified by the example of an aircraft rotor system's early rub-impact fault detection.
Numerical simulation of the breakdown process in laminar-turbulent transition of incompressible boundary layer on a flat plate
TANG Hong-tao, SONG Yun-xue
2008, 23(12): 2224-2232.
Abstract PDF(2565KB) icon1403 icon476
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Temporal mode was used to simulate numerically the breakdown process of laminar-turbulent transition and the fully developed turbulence in an incompressible boundary layer on a flat plate.The analysis of results showed that,before the breakdown process of laminar-turbulent transition,the growth rate of amplitudes of a two-dimensional and two oblique Tollmien-Schlichting waves has already deviated from the linear growth rate due to non-linear interaction,and energy transfer existed between different wave modes.During the breakdown process,the rate of strain had great effect on the general stress,and the Reynolds stress has remarkable effect on the general stress after transition.The conclusion indicates that many more harmonics will be quickly excited,and their amplitudes will also increase quickly,the direct consequence is that the Reynolds stress and its corresponding normal-wise gradient increase greatly,which in turn further modifies the mean flow profile in a much faster pace,leading to the breakdown of the laminar flow with a catastrophic nature.
Simulation of inlet swirl and evaluation in flight test
JIANG Jian, QU Ji-yun, SHI Jian-bang, ZHANG Kun-yuan, YE Fei
2008, 23(12): 2233-2241.
Abstract PDF(2471KB) icon1687 icon432
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To investigate swirl and perfect evaluation criterion of inlet/engine compatibility,a set of swirl generator was developed with adjustable blade turning angle,height and density.The validation of the swirl generator was testified through numerical simulation and wind tunnel test.The effect of adjustable parameters was also analyzed.Feasible evaluation criterion and measurement method for inlet swirl in flight test was pointed out and applied to wind tunnel test.Numerical and wind tunnel test results show that:(1)The intensity of generated bulk swirl can reach to 28 degrees.(2)Blade density and angle of attack affect swirl intensity most.(3)All kinds of typical swirl can be simulated by different blade distribution.
Research on the method to solve convergence problem in aero turbo-engine performance computation
CHEN Yu-chun, XU Si-yuan, YANG Yun-kai, TU Qiu-ye, SHANG Xu-sheng
2008, 23(12): 2242-2248.
Abstract PDF(739KB) icon1901 icon443
Abstract:
The convergence problems of solving the nonlinear equations of aero turbo-engines were studied in detail,while the non-convergence cases were counted and the mechanism was analyzed.For solving the common non-convergence problems,some improved methods based on Newton method were presented,such as: limitation of initial variables of the nonlinear equations based on components maps,polynomial fit of initial values of variables of the nonlinear equations,variable step Newton method and expansion of components' maps.These improved methods were employed in performance computing program.The performance calculation results of some fix geometry turbojet and variable geometry turbofan show that the convergence and convergence rate have been improved greatly.
Experiment and simulation of the mean value model on two-stroke gasoline aero-engine
CHEN Lin-lin, WEI Min-xiang, YANG Hai-qing
2008, 23(12): 2249-2255.
Abstract PDF(848KB) icon2240 icon507
Abstract:
The mean value model for small two stroke gasoline aero-engine based on the mechanism modeling and experiment modeling combined method was presented.The two stroke gasoline engine mean value model mainly consists of three dynamic modules: the fuel evaporation and oil film dynamic module,the intake port and crankcase scavenging module,power output module.The reed valve modeling and the short circuit loss during scavenging process were also considered at the modeling process.Then established the power output,rotational speed and Air/Fuel ratio models,and carried out simulation on Matlab/Simulink platform.The simulation result fully meets the experiment data,which proves the correctness of the mean value model.
Study and numerical calculation wall streamline distributions for hypersonic vehicle according to Euler equation
HAN Dong, FANG Lei
2008, 23(12): 2256-2261.
Abstract PDF(732KB) icon1706 icon465
Abstract:
A new method for calculating the wall streamline distributions on hypersonic vehicles was presented.Firstly surface stream function was put forward,and the relationship between surface function with surface streamline was obtained.Secondly the boundary layer edge conditions were determined by 3-D CFD method and solved by 3-D Euler equtions.And finally,the wall streamline distributions were computed based on the stream function theory and flow parameters.The calculated results indicate that the prediction and the numerical simulation proposed are workable at small angle and without angle of attack.It will play an important role in exactly predicting the heating rates on hypersonic vehicles.
Study on the flowpath and the aerodynamic characteristic of an hypersonic vehicle at different flight conditions
ZHANG Hong-ying, SUN Shu, CHENG Ke-ming, WU Yi-zhao
2008, 23(12): 2262-2267.
Abstract PDF(1201KB) icon1604 icon440
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The 3-D flow numerical simulation of a hypersonic vehicle like X43-A was implemented,and the computational static pressure distribution on the undersurface was compared with the experimental data.The comparison shows that the numerical results are consistent well with the measurements.A study was carried out to investigate the aerodynamic characteristics and the full flowpath of the hypersonic vehicle in different flight conditions.Results indicates:(1) With the increase of the free stream Mach number,the full flowpath and the aerodynamic characteristics fluctuate though changes could be found.(2)Despite of the fact that the drag coefficient is not sensitive to the change of the angle of attack,the lift coefficient and the flow structure of the full flowpath is highly affected.(3)The sideslip affects the asymmetric flowpath but with little unfavorable influence on the aerodynamic characteristic.
Application of resistance heater in supersonic combustion facility
SONG Wen-yan, XIAO Yin-li, LE Jia-lin
2008, 23(12): 2268-2273.
Abstract PDF(1134KB) icon1638 icon441
Abstract:
A unique supersonic wind tunnel facility using resistance heaters has been built to simulate the operation of a scramjet over a range of Mach numbers of 3.0 to 4.5.A number of preliminary experiments results from calibration of both the facility and the various components were introduced.Based on the previous experience and the experimental results published worldwide,a new combustor configuration using cavity flame holder to create recirculation and promote the fuel/air mixing has been developed.And the combustion characteristics of the hydrogen have been investigated in the supersonic clean airstreams experimental facility.The effect of the hydrogen fuel equivalence ratio on the flame holding mechanism and combustion was studied.Furthermore,the ignition characteristics of kerosene using hydrogen pilot have been investigated.The effect of the injection locations and diameters on the kerosene combustion was also presented.
Numerical simulation on heat transfer in duct roughened by periodic alternate scale ribs
SU Sheng, HU Jie, LIU Jian-jun, AN Bai-tao
2008, 23(12): 2274-2279.
Abstract PDF(1816KB) icon1392 icon473
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To study the heat transfer characteristics in a rectangular duct rib-roughened by periodic alternate scale ribs,six models with different rib scale were studied by employing commercial computational fluid dynamics(CFD)software CFX.The results show that,as fluid passes through each rib,a trumpet-shaped vortex is generated from the upstream vertex of the rib,shaping a region with high value of heat transfer coefficient(HTC).The area of high HTC region is affected by both the fluid flow condition and the location of the adjacent downstream rib.As compared with the duct roughened by unique size ribs,planting a smaller rib in a proper location between each two original ribs can improve heat transfer downstream re-attachment region.This also can decrease flow resistance coefficient in the duct and improve the general heat transfer ability.
Experiment study on single/fuel-lean rapped vortex combustor ignition and limit blow-out at different main air and mix air temperatures
XING Fei, ZHANG Rong-chun, FAN Wei-jun, LIU Yang, YAN Yong-qiang
2008, 23(12): 2280-2285.
Abstract PDF(1192KB) icon1685 icon483
Abstract:
To investigated ignition and limit blow-out(LBO) of a single trapped vortex combustor(cavity fueled only) test rig with kerosene as fuel,experiments were conducted in various inlet main air conditions and temperatures of premixed air.The experiment results indicate that the temperature of premixed air would improve ignition and LBO obviously,but the cavity air is a key factor.There is a critical value for main air,and the single trapped vortex combustor could obtain the best ignition performance.It becomes difficult for ignition when Mach number of main air is 0.59.
Numerical simulation of micromixing process inside micro mixer
LIU Xiang-yun, ZHANG Ren-yuan, KE Xiu-fang, LI Shi-dong
2008, 23(12): 2286-2290.
Abstract PDF(1390KB) icon1769 icon438
Abstract:
This paper simulated numerically and experimentally the micromixing process inside a micro mixing channel without any flow turbulated ribs or spins.Results show that fluid flow into the two tangent direction inlet of the model produces vortex,and increases the mixing process.The mixing process is not well proportioned with the increasing Reynolds Numbers.The mixture is equally in the suitable extent of Reynolds number.The detailed distributions of mixture volume fraction inside the channel could be obtained.
Study of pressure loss and heat transfer in contractive channel with water-drop-shaped pin fin arrays
XUAN Jian-guang, WANG Feng-ming
2008, 23(12): 2291-2295.
Abstract PDF(727KB) icon2076 icon456
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The flow processes in contractive channel with three different water drop-shaped pin fin staggered arrays were studied numerically in the present paper,and the basic features of intensity distribution of vortexes in the arrays were obtained.Moreover,the influences of the vortexes on the pressure loss and heat transfer enhancement of the arrays were discussed in detail.Comparisons were made between the contractive and rectangular channels.It is found that the average Nusselt number of the endwall in the contractive channel is higher than that of the rectangular channel in the range of the Reynolds number,and the pressure loss coefficients of the contractive channel is 3 to 4.5 times as much as that of the rectangular channel at the same Reynolds number.
Investigation of the aspirated compressor design methodology
LAN Fa-xiang, ZHOU Bai-hao, LIANG De-wang, HUANG Guo-ping
2008, 23(12): 2296-2301.
Abstract PDF(779KB) icon1725 icon461
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This paper described the efforts to develop the inverse airfoil design methodology of the aspirated compressor,showing the potential to greatly increase compressor blade loading.The study began with a single stage aspirated compressor aero design based on the performance requirement of the front three stage of an advanced test HP compressor,in order to determine the high loading for following development of the airfoil inverse design methodology.Based on the method developed,the successful design for the rotor tip section of the single stage aspirated compressor is demonstrated.
Study on transfer characteristics in 3-stage compressor with inlet pressure distortion
WANG Le-ming, LI Jun, ZHANG Bai-ling, LIU Ying-chun
2008, 23(12): 2302-2307.
Abstract PDF(1116KB) icon1700 icon491
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A method of calculating the axial-flow compressor flow field under distortion was presented.The stage distribution in different faces was computed by solving the unsteady 3-D Euler equations.The transfer characteristic for 74A compressor,for example,was computed under the inlet circumferential total pressure distortion,then the distribution of total pressure,static pressure,total temperature and flow coefficient in different faces were obtained.The distribution of the distortion intensity,distortion range and distortion position in axial direction was acquired.
Experimental investigation on flowfields of non-axisymmetric endwall of annular cascades in multi condition
ZHENG Jin, LI Guo-jun, JIA Hai-dong, WANG Chuan-mei, DONG Kang-tian
2008, 23(12): 2308-2313.
Abstract PDF(1163KB) icon1765 icon445
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Aerodynamic performance of two kinds of annular turbine cascade with non-axisymmetric endwall profiling methods,which are designed by trigonometric function controlling method and pressure difference controlling method,was experimentally studied in the annular cascade wind tunnel test rig under designed condition and off-designed condition.The results show that some new characteristic are present under different flow conditions: amplitude of pressure distribution between pressure side and suction side is changing with different flow conditions,total pressure loss coefficient will decrease with increase of outlet Match number,secondary flow vector distribution will remain unchanged with outlet Match number,but the strength of secondary flow and passage vortex will decline with reduction of outlet Match number.
Establishment of state space model of turboshaft engine with self-optimized method
ZHOU Wen-xiang, SHAN Xiao-ming, GENG Zhi-dong, HUANG Jin-quan
2008, 23(12): 2314-2320.
Abstract PDF(1610KB) icon1655 icon446
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A self-optimized method was employed to establish the state space model(SVM),that is,A,B,C,D matrices were given arbitrarily,then small perturbation response between nonlinear model and SVM was compared to seek the exact A,B,C,D matrices directly.This method aims at inosculating the response between nonlinear model and SVM,so high precision could be guaranteed.This method is not limited by the order of model.One small perturbation SVM of a certain turboshaft engine model has been established by this method,and the simulation result between SVM and nonlinear model was also compared,proving the validity and accuracy.Also,the SVM could be applied to fault diagnosis and control system design for aero engines.
Gas path debris electrostatic monitoring technology and experiment
WEN Zhen-hua, ZUO Hong-fu, LI Yao-hua
2008, 23(12): 2321-2326.
Abstract PDF(983KB) icon1567 icon476
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The formation mechanism of charged-particles,the principle of electrostatic sensor and gas path electrostatic monitoring technology were discussed in this paper,then the simulated experimental system and experiment process were analyzed to make a preliminary exploration on gas path electrostatic monitoring technology;lastly,the energy distribution characteristics of experimental signal was studied via wavelet analysis.The results show that,the signal induced by large particle has the characteristic of large amplitude and energy distribution on low frequency band,but the signal induced by fine particle has the characteristic of small amplitude and energy distribution on high frequency band.The result provides a reference for distinguishing abnormal particle and proves the feasibility of monitoring method based on charged particle.
Diagnosis method of aeroengine early fault based on the Dempster-Shafer evidence theory
YANG Jian-ping, HUANG Hong-zhong, MIAO Qiang, FAN Xian-feng, WANG Gui-bao
2008, 23(12): 2327-2331.
Abstract PDF(435KB) icon1819 icon472
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Based on the analysis of the characteristic of aeroengine early fault and information fusion,a method of forming the basic belief function was proposed when evidence theory was applied to information fusion of aeroengine fault symptom level.Thus,more precise early fault symptom could be attained.Moreover,the acquired fault symptom was applied to fuzzy cluster analysis to obtain aeroengine fault sources.Furthermore,the proposed method used fuzzy measure to express fault symptom,and considered the characteristics of imprecision,uncertainty and ambiguity of aeroengine early fault symptom.This is more suitable for the practical situation of aeroengine early fault.
Preliminary design and optimization of slotted tube grain for solid rocket motor
K Nisar, LIANG Guo-zhu, A Kamran
2008, 23(12): 2332-2340.
Abstract PDF(2597KB) icon1499 icon433
Abstract:
In this paper,design and optimization technique of slotted tube grain for solid rocket motors has been discussed.In doing so,the design objectives and constraints have been set,geometric parameters identified,performance prediction parameters calculated,thereafter preliminary designs completed and finally optimal design reached.Geometric model for slotted tube grain configuration has been developed.Average thrust has been taken as the objective function with constraints of burning time,mass of propellant,fixed length and diameter of chamber case.Lumped parameter method has been used for calculating the performance prediction parameters.A set of preliminary designs has been completed and an analysis of these results conducted.Although all the preliminary results fulfill the design requirements in terms of objective function and constraints,however in order to attain the optimal design,Sequential quadratic programming optimization technique has been adopted.As the slotted tube grain geometry is totally dependent upon various independent variables and each of these variables has a bearing on explicit characteristic of grain designing,hence affects of the independent variables on performance parameters have been examined,thus variation laws have been developed.Basing on the variation laws and the analysis of preliminary design results,upper and lower limits have been defined for the independent geometric variables and an initial guess provided for conducting optimization.Results attained exhibits that an optimal result has been attained and the value of objective function has been maximized.All the design constraint limits have also been met while ensuring sound values of volumetric loading fraction,web fraction and neutrality.This methodology of design and optimization of slotted tube grain for solid rocket motors can be used by engineers as a reference guide for actual design and engineering purposes.
Research on frequency characteristics of LOX/LH2 rocket engine
WANG Jue, ZHANG Zhen-peng
2008, 23(12): 2341-2345.
Abstract PDF(894KB) icon1578 icon370
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The frequency characteristics of a gas generator cycle liquid oxygen / liquid hydrogen(LOX/LH2) rocket engine system was analyzed numerically using matrix transform method.One-dimensional distributed parameter models were used to describe the pipelines and other components of the engine system.The models were transformed to frequency domains and described as transmission matrixes.According to the connecting relationship of the engine elements,the engine system was divided into several modules with corresponding transmission matrixes.The linear equations of engine system,which relate system variables and perturbations,were constituted from module transmission matrixes.The frequency characteristics of the system variables were thus obtained from these equations.For the purpose of validation,the frequency characteristics of a staged combustion cycle LOX/LH2 rocket engine system was analyzed as well to show the difference with the one of the gas generator cycle liquid rocket engine system.
Analysis of the subsection design of the porous wall of a transpiration cooling nozzle
JIN Shao-shan, JIANG Pei-xue, SUN Ji-Guo
2008, 23(12): 2346-2352.
Abstract PDF(965KB) icon1726 icon479
Abstract:
In order to minimize the coolant flow for transpiration cooling rocket nozzle with sintered porous media wall,an optimized transpiration cooling structure was presented in this paper,whose porous wall was divided into several sections along the axis direction.The transpiration cooling for a thruster with four-section structure porous wall was numerically studied by Fluent code and the results were compared with those of the one-section structure transpiration thruster.The results show that four-section structure can decrease the ratio of coolant flow and gas flow from 28.3% to 12.6% on the premise of satisfying the cooling need of the nozzle inner surface wall,the multi-section porous wall design is an effective way to reduce nozzle transpiration coolant flow.

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