2011 Vol. 26, No. 8

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Sensibility analysis of the air inlet position in the rotating cavity
DING Shui-ting, ZHANG Gong, LI Ye, LI Guo
2011, 26(8): 1681-1687.
Abstract PDF(1085KB) icon2194 icon51
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Fluid structure interaction numerical method was applied to investigate the influence of air inlet position on the cooling effect of the rotating cavity.And,in order to ensure the safety of the turbine disk,the cooling effect was evaluated by an engineering evaluation system,which includes resistance evaluation,heat transfer evaluation and stress distribution evaluation.The results show that,the air inlet position has a great influence on the fluid structure in the rotating cavity,which determines the heat transfer and the temperature distribution of the rotating disk.Furthermore,the thermal stress of the rotating disk related to the temperature gradient can be affected.With the rise of the inlet position,the frictional windage of the rotating cavity increases,the heat transfer of the windward of the disk slacks,and the stress level and the maximum value decline.Therefore,the change of the inlet position has an effect on the failure probability of the turbine disk from two aspects:the material affordability and the working stress.
Experimental study of discharge coefficient and cooling effectiveness for impingement effusion cooling in curved section
LUO Guo-liang, YANG Wei-hua, CAO Jun, SHI Rui, SONG Shuang-wen
2011, 26(8): 1688-1694.
Abstract PDF(956KB) icon1859 icon43
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In order to experimentally study the discharge coefficient and cooling effectiveness of impingement effusion cooling in curved section of combustion chamber,several test pieces with different geometrical dimensions were designed.The research results from experimental study show that: (1) The discharge coefficient of impingement effusion dimension in curved section is less than 0.7.The discharge coefficient of effusion hole angle 40° is larger than the discharge coefficient of effusion hole angle 30° and 20°,and the spacing between effusion holes has a great influence on the discharge coefficient. (2) The cooling effectiveness of impingement effusion in curved section is increased with the increase of blowing ration.And there is a large difference for the cooling effectiveness of impingement effusion between curved and flat sections,and the difference is decreased with the increase of blowing ratio.
Unsteady numerical simulation of the turbine blade film cooling
ZHOU Li, ZHANG Xin, CAI Yuan-hu
2011, 26(8): 1695-1701.
Abstract PDF(1249KB) icon1653 icon46
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The unsteady flowfield of the turbine blade film cooling was investigated numerically,and the influence of unsteady stator/rotor interaction on the blade film cooling effectiveness was discussed.Results show that,the overlying width of the cooling jet flow increases near the downstream of the cooling jet position,when the stator wake is transferred to the cooling jet position,resulting in better film cooling effectiveness at the downstream within 30% arc length range.The fluctuation of the film cooling effectiveness increases with the increment of the blowing rate.Due to the influence of the vortex near the endwall,the cooling jet flow can hardly reach the endwall region,but be entrained to the downstream of the jet position,so the cooling effectiveness is improved correspondingly.
Experiment on heating kerosene with useless heat on the wall of pulse detonation engine
HUANG Xi-qiao, CHEN Le, YAN Chuan-jun, ZHENG Long-xi, WANG Zhi-wu, QIU Hua
2011, 26(8): 1702-1707.
Abstract PDF(973KB) icon1798 icon36
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Using kerosene as fuel and air as oxidizer,experiments on heat exchanger between detonation tube and fuel were performed on a pulse detonation engine (PDE) with a diameter of 110mm at different frequencies. It's found that the way of utilizing the waste heat produced by detonation tube can not only increase the temperature of fuel,but also improve PDE's operating performance and shorten the distance of deflagration to detonation transition (DDT).This heat exchanger process could also reduce the temperature of detonation tube.The temperature of detonation tube could decrease by 94℃ at the operating frequency of 20Hz.
Influences of the swirl cup flares design on the small combustor ignition performances
LUO Guo-liang, SONG Shuang-wen, HU Hao-sheng, PENG Jian-yong
2011, 26(8): 1708-1712.
Abstract PDF(815KB) icon1996 icon53
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The small combustor ignition performances were investigated experimentally with arc flare and straight line flare design swirl cup.Both swirl cups have the same primary and secondary radial vane swirler and a simplex pressure atomizer.The ignition experiments were conducted under atmospheric pressure and temperature,and the pressure drop across the flame tube was between 0.1% and 4.0% of inlet total pressure.The ignition results indicate that the ignition performances of swirl cup with straight line flare design are better than those with arc flare design.The flow field and two-phase flow field investigated from previous measurements illuminate the reason of the ignition results.
Numerical and experimental investigation on effect of distance between impingement and effusion plates on heat transfer characteristics of impingement-effusion composite cooling
ZHANG Bo, LI Ji-bao, JI Hong-hu, SHANG Shou-tang, CHENG Ming, WANG Yan-li
2011, 26(8): 1713-1718.
Abstract PDF(1191KB) icon1668 icon38
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The influence of distance between impingement and effusion plates on heat transfer characteristics of impingement-effusion double wall was investigated numerically, and the validity was experimentally verified. Results show that, with the increase of gap distance, heat transfer characteristics increase firstly, and then decrease. The change of gap distance caused different developments of impinging jet and pumping effects, and also led to different heat transfer effects. It shows that fluid particles move in translational mode in most region, but in rotating mode near effusion hole and impinging hole. The stronger fluid particle rotating causes better heat transfer effect.
Numerical and experimental study on inversing-rotating aero-valves of PDE
GONG Ji-shuang, FAN Yu-xin, WANG Jia-hua, ZHAN Huan, ZHANG Jing-zhou
2011, 26(8): 1719-1727.
Abstract PDF(1140KB) icon1895 icon46
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As a new concept aero-valve used in pulse detonation engine (PDE),inversing-rotating aero-valve was mentioned to improve one-way performance of the valve in this paper.A useful inclusion was obtained after a series of numerical investigation,that is,the swirl number is the key parameter affected the valve's performance.The optimum value of swirl number is approximately one.In addition,an aero-valve which swirl number equals to 1.364 was made to experiment.The experimental results without ignition demonstrate the conclusion revealed by numerical way.Finally,detonation waves at the operating frequency of 40Hz are obtained in a tube with inner diameter 114mm.
Electro-impulse de-icing (EIDI) technology study
LI Guang-chao, HE Jiang, LIN Gui-ping
2011, 26(8): 1728-1735.
Abstract PDF(941KB) icon1846 icon49
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The electro-impulse de-icing (EIDI) system was decomposed into four processes, and then its work theory was analyzed. The research methods and results in the field of electrodynamics were introduced, by taking the impacting pendulum test and Bernhart-Schrag model as an example. The feature of structural dynamics generated by pulse power was analyzed through the parameters of acceleration, strain and vibration displacement on the skin surface. A criterion of de-icing forecast was proposed, by making use of the strain on the skin surface. The experimental results in engineering applications were summarized including flight test, fatigue test and electromagnetic interference test. And on this basis, the development direction of the EIDI technology was prospected.
Complex lubrication and cooling technology of rolling bearing on micro aero-engines
LI Guo, HAN Shu-jun, DING Shui-ting, DU Fa-rong
2011, 26(8): 1736-1743.
Abstract PDF(1335KB) icon2651 icon51
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Based on computational fluid dynamics (CFD) method,the pressure and gas/liquid distribution in rolling bearing chamber and the effect of lubrication and cooling through varied gas-oil ratio were researched.The results show that the pressure distribution is not clearly changed with the increase of gas-oil ratio but the inhomogeneous force is enlarged in ball and cage.The gas/liquid two-phase flow distribution is not homogenized in rolling bearing chamber upstream,and then gradually becomes regular downstream and the position of ball influences the two-phase flow distribution.The thickness of oil slick distribution is not homogenized and the effect of lubrication is not enhanced with oil increase.The cooling effect of rolling bearing mainly depends on the gas-oil ratio and the large gas-oil ratio can enhance cooling effect.
Numerical simulation and experimental study on flame acceleration in annular detonation duct
QIN Ya-xin, YU Jun-li, GAO Ge
2011, 26(8): 1744-1749.
Abstract PDF(932KB) icon1845 icon48
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Numerical simulation of annular detonation duct with orifice plate of different numbers were carried out to study the phenomena of flame acceleration,the evolution of deflagration to detonation transition (DDT) and the detonation initiation distances at different equivalence ratios.Two-dimensional axisymmetric and unsteady Navier-Stokes equations were numerically simulated.The results of numerical simulation show that laminar flame is generated by low energy ignition in the region of flame mixing.The flame of low velocity jets to annular detonation duct,and propagates to the export with a changed direction.The laminar flame becomes turbulent flame in the obstruction of orifice plate and under the acceleration action of shock wave and reflected wave.The turbulent flame is strengthened mutually with its induced shock wave,and then detonates the unburned mixture.The progress of detonation propagation in the region with obstacles was also analyzed.The flame velocities and detonation initiation distances at different equivalence ratios were studied respectively.Through calculation and analysis,deep understanding of flame acceleration and DDT was obtained,and data for the mechanism of indirect initiation were accumulated.
Flamelet/progress variable model for supersonic reacting flows
FAN Zhou-qin, SUN Ming-bo, LIU Wei-dong
2011, 26(8): 1750-1755.
Abstract PDF(1111KB) icon2153 icon32
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The flamelet/progress variable model for supersonic turbulent reacting flows was developed based on Pierce's model for low Mach number flows,in consideration of the compressibility effects and shock waves.The present model solved the mixture fraction and progress variable transport equations,and employed three solution branches of flamelet equation:the steady burning branch,the unstable branch of partially extinguished states and the complete extinction state.The performance of the flame/progress variable model was compared to the steady flamelet model for predicting the product and temperature field of a hydrogen-air supersonic combustion ramjet engine in DLR (Deutsches Zentrum für Luft- und Raumfahrt) for which experimental data are available.With capturing of extinction and lifted flame,the present model is good agreement with the experimental data,and outperforms the steady flamelet model which predicts an attached flame.
Effects of airflow split and primary holes arrangement on the lean blowout limits of a combustor with axial-radial swirl cup
XIE Fa, HUANG Yong, MIAO Hui, HU Bin
2011, 26(8): 1756-1760.
Abstract PDF(739KB) icon2028 icon38
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An experiment was conducted for studying the effect of the variations of dome air entry areas and the arrangements of primary holes on the lean blowout (LBO) limits of a single dome rectangular model combustor with axial-radial swirl cup.The experimental results show that the decrease of air entry areas of the primary axial-swirler and the increase of primary holes' number have great effect on the LBO limits of the combustors.Decreasing of air entry areas into the primary axial-swirler by 20% will improve the combustor lean blowout limits about 9.7%,and increase of the number of primary holes to 4 will improve the combustor lean blowout limits about 7.6%.Besides,increase of air entry areas into the primary axial-swirler by 20%,change of air entry areas into the secondary radial-swirler by 20% and change of the number of primary holes to 2 have little effect on the combustor LBO limits.
Numerical simulation study on temperature field of helicopter nacelle fire under non-ventilation condition
NIU Xue-min, XIE Yong-qi, YU Jian-zu
2011, 26(8): 1761-1767.
Abstract PDF(1172KB) icon2424 icon32
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The model of fire was established for nacelle of helicopter using large eddy simulation (LES) technology.Taking oil pool fire as an investigation object,the fire scene was designed.Different ignition positions of nacelle fire were studied by simulation method.And the influences of ignition positions on heat release rate,velocity field and temperature field under non-ventilation condition were analyzed.The results show that it has a significant effect on fire propagation in nacelle when the ignition positions are changed.Meanwhile,serious damage of components occurs at the bottom of nacelle in 1/4 position due to strong fire.So,more attention shall be paid to the fire protection design.The conclusion provides a reference for design of fire protection in nacelle.
Investigation on heat transfer mechanism of impinging jet with cross-flow
ZHANG Chuan-jie, SUN Ji-ning, LI Hao, MAO Hong-xia
2011, 26(8): 1768-1774.
Abstract PDF(1270KB) icon1679 icon29
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Experimental and numerical investigations were made to simulate heat transfer characteristics of a single impinging hole and short impinging distance with cross-flow. The results show that:(1)in the experiment, the average Nusselt number of the impingement surface increases with the increase of cross-flow; (2)the Nusselt number in the front impact area decreases with the increase of cross-flow, because the flow velocity near the wall decreases, weakening the heat transfer effect; (3)the Nusselt number behind impact area near the impact point increases with the increase of cross-flow, because the vortexes directions between the horseshoe vortex in the upstream near the impact point and the stretching vortex produced by impinging jet are the same, and these two vortexes enhance the heat transfer in the impact surface.
Ground wind tunnel test study of the propeller of stratospheric airships
LIU Pei-qing, MA Rong, DUAN Zhong-zhe, MA Li-chuan
2011, 26(8): 1775-1781.
Abstract PDF(1097KB) icon2020 icon40
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In accordance with similarity criteria such as the equal Reynolds number and equal advance ratio, the paper established some similarity formulas about the thrust coefficient, the power coefficient and efficiency from the perspective of kinematic similarity and dynamical similarity for the propeller of stratosphere airships. The scaled model test of the propeller was carried out in Beijing University of Aeronautics and Astronautics ground wind tunnel. It shows that the experiment results basically tally with the results of the standard strip's theoretical calculation and numerical simulation. So it proves that the environment density has no effect on similarity parameters, and the scaled model test of the propeller can be carried out in the ground wind tunnel using the Reynolds number similarity criteria and the advanced ratio similarity criteria. There is no need of building special and costly low-density wind tunnel. Meanwhile, the experiment results also show that there is a large lateral contraction in the slip flow regime when the advance ratio of the propeller is less than 0.3. So lateral contraction correction is required for the nondimensional aerodynamic character curves calculated by the standard strip theory.
Research on visualization of transient high speed exhaust flow by FRS technique
WANG Sheng, HU Zhi-yun, ZHANG Zhen-rong, LIU Jing-ru, YE Jing-feng, ZHANG Li-rong
2011, 26(8): 1782-1786.
Abstract PDF(986KB) icon1501 icon28
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A visualization technique based on of molecular filtered Rayleigh scattering (FRS) was studied for diagnosing the structures of transient high speed exhaust flow.The diagnostics system was composed of a narrow line width laser,a molecular/atomic absorption filter and a collection device such as ICCD(intensified charge coupled device).The absorption filter was used to modify the spectra of the Rayleigh scattering signal from the flow field illuminated by a laser sheet from a Nd : YAG (neodymium-doped yttrium aluminium garnet) pulsed laser.The laser was tuned to an absorption line of iodine vapor contained in the filter.This caused background scattering from solid particles and surface to be strongly absorbed,while much of Doppler broadened Rayleigh scattering was transmitted through the filter.FRS diagnostic system was described.FRS technique was used to diagnose transient high speed exhaust flows.The turbulence structures on the area of laser action were obtained.These demonstrate the ability of the FRS technique to diagnose supersonic flow.
Power-matching methodology in tip-jet drive rotor design
LI Yi-bo, MA Dong-li, NIU Ling-yu
2011, 26(8): 1787-1793.
Abstract PDF(1007KB) icon1954 icon34
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A power-matching methodology was promoted to decouple the interior-flow and external-flow of a tip-jet drive rotor,and a reaction drive model based on the engine exhaust gas property and duct flow condition was established,which including:influence of area,temperature,friction and rotor rotation.The rotor tension and torque was analyzed by a modified blade element method.The result shows that section thickness and rotary speed are main influential factors to the tension and power balance,and the represented method is a rapid approach to choose the jet rotor parameters in overall design stage.
Experiments of sidewall compression scramjet inlet on dynamic characteristic of angle-of-attack
LIU Kai-li, ZHANG Kun-yuan, GUO Bin
2011, 26(8): 1794-1800.
Abstract PDF(1114KB) icon2106 icon36
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In order to research the influence of dynamic angle-of-attack on the performance of hypersonic inlet,wind tunnel experiments were conducted on a sidewall compression scramjet inlet with Ma=3.85,range of angle-of-attack 0°~8.2° and frequency up to 10.4 Hz.The present work suggests that:with the high angle-of-attack,the inlet could work in unstart mode,and flow field features are significantly altered and also analyzed by a computational fluid dynamics (CFD) solver.In the dynamic process of angle-of-attack,the inlet could go through a start-unstart-restart process but the pressure on the wall has the hysteresis effect,especially when the inlet is unstart.With the rise of frequency,the value of unstarting angle-of-attack could increase and restarting value could decrease in the oscillation.
Design and numerical investigation of RBCC prototype inlet
SHI Lei, HE Guo-qiang, QIN Fei, LIU Pei-jin, LIU Xiao-wei
2011, 26(8): 1801-1807.
Abstract PDF(1026KB) icon1958 icon45
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The inlet of RBCC(rocket based combined cycle) engine ground-test prototype operated in rocket ejector mode and ramjet mode(Mach number from 0 to 4.0) was investigated.The 2-D(two-dimentional) inlet with strut was designed.Through numerical simulation,a comparative analysis of the performance and the inner flow with/without strut in the inlet in ramjet mode was made,whereas rationality of the design was verified and a rule was derived for the variation of the performance of RBCC prototype's inlet,which was induced by the change of the location or the configuration of strut.Finally,an optimized configuration was obtained.
Study on critical enthalpy extraction ratio and numerical validation for magnetohydrodynamic inlet
CHEN Rui-feng, WEI Zhi-jun, WANG Ning-fei
2011, 26(8): 1808-1813.
Abstract PDF(980KB) icon1685 icon29
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To ensure that the magnetohydrodynamic (MHD) inlet works in starting state,the concept of critical enthalpy extraction ratio was proposed for the MHD inlet.The quasi-one-dimensional model for the critical enthalpy extraction ratio state of MHD inlet was analyzed using the turbojet engine model,the variable cross-section pipe flow theory and the expressions of modified polytropic efficiencies.By comparison of this model with the computational fluid dynamics (CFD) method,the results show that this model fits good,and the error is less than 5.7%,thus providing a reference for design of the MHD inlet.
Regulating turbine exhaust valve about piston engine based on analyzing propeller
HU Yan-ling, XU Bin, YANG Shi-chun
2011, 26(8): 1814-1818.
Abstract PDF(954KB) icon2181 icon36
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The regulation of turbocharger exhaust valve was studied in cruising condition by analysis of engine propeller's power characteristic.The economy of aircraft operation was also predicted.Cruising condition of constant 180km/s was researched at 4000 meters altitude,the target pressure of air box could be reached by adjusting exhaust valve,and the propeller pitch was determined by propeller characteristic map.The results show that compressor matched with turbocharger is working within 68%~76% high efficiency area by regulating propeller pitch and turbocharger exhaust valve at constant speed of the airplane.
Numerical simulation of RCS for axisymmetric nozzles and symmetrical two-dimensional nozzle
YANG Tao, YANG Qing-zhen, LI Yue-feng
2011, 26(8): 1819-1823.
Abstract PDF(985KB) icon1921 icon39
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The iterative physical optic method was used for the programming code to calculate radar cross section (RCS),while the forward-backward algorithm combined with relaxation factor was used to accelerate the convergence and improve operation efficiency.Some sample standard models were calculated to validate the reliability of the code;based on this,the RCS of two-dimensional(2-D) nozzles with different aspect ratios and an axisymmetric nozzle was computed and compared.According to the numerical results,this procedure has high accuracy and versatility,and the RCS of the 2-D nozzle is higher than that of the axisymmetric nozzle in the large angular range.
Experimental study on fatigue curve law of turbine blade under combined high and low cycle loading
YAN Xiao-jun, SUN Rui-jie, DENG Ying, LIU Zhi-na, NIE Jing-xu
2011, 26(8): 1824-1829.
Abstract PDF(1006KB) icon1967 icon85
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The effect of the high cycle vibration load on the high-temperature fatigue properties of the turbine blade were addressed.Combined high and low cycle fatigue tests were carried out on several blade specimens.The results show that the superposition of high-frequency vibration on low-cycle load can significantly reduce the fatigue life of the blade.It is noteworthy that combined high and low cycle fatigue has two features:great dispersion and no fatigue limit.The former is exhibited by much broader life range than the low cycle fatigue (LCF) test,and the latter indicated by fracture of the blades over 107 high cycles (which is considered as the life limit of the metal materials for the invariable-amplitude fatigue).In addition,the fatigue data suggest a double logarithmic linear relationship between vibration stress level and the combined fatigue life.Further research has found that the law for superalloys operates universally.
Rotor vibration fault diagnosis method based on wavelet energy spectrum entropy and SVM
AI Yan-ting, FEI Cheng-wei
2011, 26(8): 1830-1835.
Abstract PDF(910KB) icon1755 icon33
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A method for rotor vibration fault diagnosis was proposed based on wavelet energy spectrum entropy and support vector machine (SVM) by fusing their advantages.The typical rotor vibration faults were simulated on the rotor test-bed and vibration signals were collected at the same time.The SVM model and multi-classifier for rotor typical faults diagnosis were established through training of the samples obtained,and the unknown rotor faults were recognized consequently.It is proved by practical applications that the method proposed in this paper for diagnosing rotor vibration faults is workable and effective.
Life scatter factor of time truncated zero-failure data subjected to normal distribution
FU Hui-min, ZHANG Yong-bo
2011, 26(8): 1836-1840.
Abstract PDF(800KB) icon1967 icon31
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For the existing method to calculate the life scatter factor only fits to complete data, it is not suitable for the time truncated zero-failure data which are significantly increasing in the life tests. Therefore, this study introduced the theory of complete data scatter factor into the situation of time truncated zero-failure data, and proposed a method for the life analysis of normal time truncated zero-failure data by providing the formula of life scatter calculation. According to the theory analysis and calculating result, it shows that the scatter factor of time truncated zero-failure data is significantly smaller than the completed data, and thus the method proposed by this study can fully utilize the depressed safety life by complete data scatter factor method.
Capability simulation of the turbine damper of certain UAV system
LI Yue, PEI Jin-hua
2011, 26(8): 1841-1846.
Abstract PDF(899KB) icon1648 icon30
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Turbine damper was used as a brake equipment for the pneumatic/hydraulic launching system and arresting net recovery system of certain unmanned aerial vehicle(UAV).The mathematics model of damp moment about turbine damper was built and simulated.The results of numerical analysis indicate that rotor radius and liquid medium density are key parameters affecting damp moment.The influences of some parameters such as stator radius,axes direction clearance between rotor vane and stator vane,kinematic viscosity modulus of liquid medium,on the damp moment are lesser reversely.Many turbine dampers with diversiform structure sizes and different liquid medium were used for the measure test of damp moment.The research results indicate that the simulations are in good accordance with the experiments,proving the validity of the mathematics model of damp moment.Therefore,a dependable theoretic basis is offered for the engineering development of turbine damper by the research.
Experimental investigation of the worst-case mode localization for a mistuned bladed disk assemblies
LIAO Hai-tao, WANG Jian-jun, WANG Shuai, LI Qi-han
2011, 26(8): 1847-1854.
Abstract PDF(1668KB) icon1792 icon39
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Based on the vibration mode characteristics of mistuned bladed disk,the methods for analysis mode localization were presented to assess the worst-case mode localization of mistuned bladed disk,numerical example shows that the method presented is reliable and effective.An experimental investigation of a simple 12-bladed academic blisk was then presented.The purpose was to validate theoretical predictions about the occurrence of mistuning jump-localized modes and to gain greater insight into the mechanisms by which the phenomena occur.The experimental measurements of localized mode shapes were compared to predictions based on the finite element method.The experimental measurements were found to have excellent agreement with numerical simulation results.
Sealing performance multivariate two-variance regression analysis method for rubbers
WU Qiong, FU Hui-min
2011, 26(8): 1855-1859.
Abstract PDF(961KB) icon1619 icon34
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The accelerated aging model of rubber seals was established and the multivariate two-variance regression analysis method for the compression set was also put forward.Then the multivariate regression equation and confidence limit curves with high confidence level and high reliability were given,based on which the calculation methods for the reliable storage life and storage reliability were obtained.The sealing performance multivariate two-variance regression model involves two independent variables associated with test time and temperature respectively;thus it can analyze accelerated aging data under different temperatures simultaneously.The presented method exploits the lengthwise information of the compression set among different test times and can solve the problem of reliability assessment with higher precision.
Preliminary research on structural dynamical design based on evolutionary structural optimization method
LIU Da-ni, HONG Jie
2011, 26(8): 1860-1865.
Abstract PDF(890KB) icon2166 icon35
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A new idea of structural dynamical design and a development technology of optimization program based on ANSYS platform were proposed by using the evolutionary structural optimization method and structural efficiency. A single objective, multi-constraint optimization model was created by incorporating the dynamical design parameters of mass, stress, displacement and frequency; and the constraints were considered separately at the start of the study. The feasibility of this method and reliability of the program were proved by some examples, of which the final topology, evolution and variation of parameters were similar to the previous research under the same conditions and without consideration of influences caused by numerical instability.
Sealing performance of pipeline connection under the tensile load
WANG Zhen-xing, QIU Ming-xing, WANG Jian-jun
2011, 26(8): 1866-1870.
Abstract PDF(840KB) icon1813 icon36
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The sealing performance of aircraft engine pipeline connection was investigated under the tensile load in two aspects. Firstly, the contact force change of the pipeline connection sealing surface was studied to make a mechanical analysis of the sealing performance, by establishing the equivalent rigid model and the force balance equations of the pipeline connection under tensile load. Secondly, the multi-body contact elastic model of pipeline connection was established and the numerical simulation was made by finite element method(FEM) under the pre-tightening force and tensile load, whilst the contacts with initial penetration were established to realize the implementation of preload. On the basis of the simulation results, this paper made a detailed quantitative analysis of pipeline connection's sealing performance, through investigation of contact forces, contact area and contact stress on the sealing surface.
Influence on the performance of compressor cascade with alterative incidence angles by the plasma
LIU Hua-ping, CHEN Huan-long, YUAN Ji-lai, CHEN Fu
2011, 26(8): 1871-1878.
Abstract PDF(1593KB) icon1917 icon35
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The plasma effect on the performance of high-turning compressor cascade was investigated at different incidence angles,voltages and electrodes locations.The results show that,with the increase of the incidence angle,the aggravation of the flow separation is a primary reason for the increase of the cascade losses,while the boundary layer losses near the end-wall decrease due to the reduction of the flow velocity.At all the incidence angles (i=0°,5°,-5°),the plasma actuator could weaken the separation,reduce the cascade losses and increase the blade loading effectively.The bigger the voltage and the closer the electrodes to the separation line,the more obvious the plasma effect becomes.And the bigger incidence angle leads to weaker plasma effect.Although the electrodes are installed along the whole blade height,the plasma merely reduces the losses in the region above 10% blade height,and the loss reduction is almost the same in this zone.
Seven-hole probe and its application in the secondary flow for a high-load compressor cascade
WU Ji-chang, LI Cheng-qing, ZHU Jun-qiang
2011, 26(8): 1879-1886.
Abstract PDF(1271KB) icon1921 icon37
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The design and calibration methods for a new type of seven-hole probe were described,and better calibration results were obtained in this paper with the help of a subsonic wind tunnel and self-designed code on data reduction.Based on suitable distribution for all the non-dimension parameters,it indicates that the probe is capable of measuring complex secondary and vortex flow with the angle more than 65°.The error analysis based on calibration data shows that the probe can measure the flow velocity and angle at a relative error of 2.04% and 1.99°,respectively.For the complicated secondary flow at outlet of a highly-loading compressor cascade,the detailed flow field information can be captured by the probe,contributing to build up the secondary flow model in compressor passage.
Identification of stall characteristics of axial flow compressor
WANG Chun-rui, YUE Lin
2011, 26(8): 1887-1892.
Abstract PDF(1081KB) icon2358 icon34
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In order to identify the number of stall cells during rotating stall process,a method was presented in this paper. Firstly, the phase and amplitude characteristics of pressure fluctuation during stall process were drew in the polar coordinate, and then the number of stall cells was obtained by judging the waveform displayed. After comparison with the traditional method, it shows that this method for determining the number of stall cell is better than original one thanks to its noise immunity and certain degree of precision. Besides, the method can also visualize the areas of stall in circumference and occurrence and development of stall inception in compressor.
Numerical study on temperature distribution of tank pressurization process of liquid rocket during outflow
WANG Lei, LI Yan-zhong, LI Cui, CHENG Xiang-hua
2011, 26(8): 1893-1899.
Abstract PDF(956KB) icon1716 icon37
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In view of the tank pressurization process of a certain liquid rocket during outflow, a two-dimensional numerical simulation method was adopted to study the law of temperature distribution in the ullage gas and in the tank wall. In this model, the low-Re k-ε model was selected to calculate the coupled heat transfer between fluid and tank wall, and a user-defined function (UDF) for phase transition was compiled and embedded into Fluent so as to research the effect of heat and mass transfer at the liquid surface. Certain experimental data in reference were selected to verify the results of this model on the same condition. The comparison results show that this two-dimensional model can forecast axial temperature distribution in ullage gas and in tank wall correctly. In addition, the computation results show that the effect of the direction and the area of pressurized gas injector on the axial temperature distribution in the ullage gas and in the tank wall is weak, but the temperature field nearby gas inlet is little affected by them. When pressurized gas is injected downstream into the tank ullage, the gas temperature nearby tank top is lower, which may be favorable to the normal operation of relief value. When pressurized gas is injected into the tank ullage horizontally, the bigger diameter of the injector means larger high-temperature region nearby the tank top.
Numerical investigation of combustion about injection positions in rocket induced secondary combustion of RBCC engine
PAN Ke-wei, HE Guo-qiang, LIU Pei-jin, QIN Fei, YANG Bin
2011, 26(8): 1900-1906.
Abstract PDF(1065KB) icon1756 icon32
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In order to investigate the influence on combustion by changing the injection positions in the rocket induced secondary combustion,the numerical simulation was used to study the rule of the distribution of component in the flow,the area of high temperature heat release and the distribution of pressure in the flow.The results show that:the combustion flow is obviously affected by changing the injection positions.In the combustor,the combustion performance could be improved by putting the fuel injection position forwards,helping to strengthen the mixing capability of fuel.For the fuel mixed ahead the flame of primary rocket,it accelerates the fuel spray evaporation effect,improves the flame spread and increases the combustion efficiency.In order to improve the performance of combustion in the rocket induced secondary combustion,the fuel injection positions should be placed at front end in the combustor.
An improved method of identification for aero-engine's state variable model
ZHANG Hai-bo, YANG Xiao-long, LIN Yi-hui
2011, 26(8): 1907-1913.
Abstract PDF(1008KB) icon2019 icon39
Abstract:
The method for aeroengines' state variable model(SVM)identification was implemented by using the linear relation of the variable of the differential equations,and separating the steady process and transient process to eliminate the steady errors coupled by transient process. Without solving the differential equations or using any iterative methods, the coefficient of the SVM could be acquired simply using matrix operation, so it has a higher computational efficiency than former least square method. And this method might also be combined with other identification method to realize better effect. Finally, to illustrate the validity and accuracy of the proposed method, a small perturbation SVM of some turbo-shaft engine model had been established through it, and the simulation results from the engine's state space model and nonlinear model were compared,and we can draw a conclusion that the SVM got by this method meets the dynamic and static objectives well, though the plant has a severe nonlinearity.
Mechanical research of double-decker ball bearing
ZHU Yi-li, XU Long-xiang
2011, 26(8): 1914-1920.
Abstract PDF(1230KB) icon2200 icon37
Abstract:
The mechanical model of the double-decker ball bearing was established and the relative calculation program compiled in MATLAB was developed based on the quasi-dynamic method by considering the radial load,axial load,centrifugal force as well as the gyroscopic moment acted on the bearing simultaneously.And the method was verified experimentally.The simulation results show that,the relationship between the inner and outer pitch diameters of the bearing determines the inner and intermediate races' rotate speed distribution.The radial and axial loads affect the ball contact angles relating to the bearing failure.Rotate speed,ball materials,axial preload as well as the initial contact angles greatly impact the bearing stiffness.The results provide a theoretical basis for the design and use of this bearing in high-speed rotor-bearing system.

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