2012 Vol. 27, No. 5

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Display Method:
Approach and facility for aerodynamic thermal test by lower speed and high-temperature gas flow
DONG Su-jun, QI Bin, LI Zhi-jie, FAN Wei-jun, ZHANG Rong-chun, WANG Jun
2012, 27(5): 961-968.
Abstract PDF(1107KB) icon2369 icon693
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Comparability of flow parameters and surface heal flux density on a typical leading structure by these two heating approach was analyzed,it was demonstrated to be feasible of utilizing lower-speed and high-temperature gas flow as heating method for hypersonic aerodynamic thermal test.A new combined heating scheme composed of a lower-speed and high-temperature gas flow and quartz lights was proposed for hypersonic aerodynamic test of blunt cone’s.The newly-built aerodynamic thermal tester was designed with an efficient double-chamber vaporizing combustor,a new water-cooled pipe structure with thermal insulation sandwich of keramic material bearable high temperature,electric pre-heaters and twin-fule-supply scheme for the combustor.It can generate a hot gas of 2100K.The average gradient of radial temperature distribution of φ250mm nozzle is about 3K/mm.And the tester has auto-linear-control ability of temperature and the temperature difference is 46K.In a word,it can meet the urgent requirement for thermal test of high temperature and high heat flux of hypersonic vehicle flying by 24km height and mach number 6 speed.
Transient measurement for measuring the heat transfer in a rotating cavity with a high rotational speed
SUN Ji-ning, LUO Xiang, LIU Jin-nan, XU Guo-qiang, ZHOU Zhi-xiang, QIU Chang-bo
2012, 27(5): 969-974.
Abstract PDF(574KB) icon1958 icon633
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A real turbine disk cooling configuration was simplified to be a shrouded rotating disk system with central coolant air.Heat transfer characteristic was studied by experimental method.On the heat transfer test rig with high rotating-speed for rotating components,the procedure of experiment and the method of data processing were established initially.The Nusselt number of the rotating disk surface was got,and the variations with the mass flow coefficient,the rotating Reynolds number and the ration of sealing clearance were studied.Conclusions could be drawn as follows:For central inlet,the heat transfer in the lower radius is mainly controlled by the impingement of cooling air,the influence of impingement decreases with the increasing of radius.The Nusselt number increases with the mass flow coefficient and the rotating Reynolds number,decreases with the ratio of sealing clearance.
Experimentation on nitrogen-enriched characteristics of on-board hollow fibre membrane
LIU Xiao-fang, LIU Wei-hua, QIAN Guo-cheng, ZHAO Hong-tao
2012, 27(5): 975-980.
Abstract PDF(647KB) icon1734 icon574
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The experimentation and analysis of on-board hollow fibre membrane,which were jointly designed by a technic center,were systemically implemented by ground condition simulation.Results show that:(1) the oxygen concentration descends with input pressure increasing,ascends with input flux arising,and then is basically independent of the temperature of input air;(2) the oxygen concentration increases with the output flux gained,especially under the low pressure of input air;(3) the effect of height above sea level on the nitrogen-enriched performance of the membrane is light.The formula of nitrogen-enriched performance was found by multielement regression and validated by the comparison of experimental results.
Volume fraction technique for measuring the minimum value of mass flow in turbine rotor-stator disk cavities
SUN Ji-ning, LUO Xiang, LIU Jin-nan, XU Guo-qiang, ZHOU Zhi-xiang, QIU Chang-bo
2012, 27(5): 981-985.
Abstract PDF(397KB) icon2019 icon611
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The minimum value of the cooling air flow is a critical flow rate for preventing hot gas ingestion happened in the rotor-stator disk cavity system of turbines.Experimental investigation based on volume fraction technique was performed to found the minimum values of cooling air flow of six typical rim seal structures with different rotating velocities and seal clearances.The results showed that,the minimum value of the seal air flow rate almost increases linearly with rotational velocity,and also increases with the seal clearance.Furthermore,the corresponding correlations about sealing flow rate were fitted for different structures,and an optimum option of rim seal structure was advised.
Dynamic image processing measurement method of droplets impingement characteristics
LIU Dan-yang, HAN Ya-hui, Ding Li, YANG Chun-xin
2012, 27(5): 986-992.
Abstract PDF(852KB) icon1815 icon572
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Image processing method was applied to analyze the dying process at different locations on test cylinders in order to examine the variation of the surface chroma during the test.A complete test was divided into three stages:sub-dyed,balanced and over-dyed.The chroma distribution of balanced stage was normalized and defined as local water collection efficiency.Droplet impingement limits and the ratio of total impingement to the maximum local impingement efficiency can therefore be analyzed by the colorimetric integration curves.Comparing to the numerical simulation and the experiment of NASA (National Aeronautics and Space Administration),the current results indicate that water droplets impingement characteristics can be correlated with the dynamic RGB(rad-green-blue) color space,with ±15% repeatability error.Interrelation among the three characteristics was also observed.
Effect of cavity leading edge angle on performance of super-sonic combustor
JIA Zhen, WU Di, PIAO Ying, XUE Mei-xin
2012, 27(5): 993-998.
Abstract PDF(755KB) icon1777 icon590
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The effect of cavity leading edge angle on flow field and cavity drag characteristics in a supersonic combustor under the condition with/without chemical reactions was numerically investigated.It is found that low velocity and high temperature recirculation zones form in cavity and upstream boundary layer of wall orifice,respectively,which are induced by a bow shock produced by the normal fuel jet interacting with the supersonic cross flow and expected to facilitate the fuel ignition and enhance the flame stabilization.A shock/boundary layer interaction phenomenon arises from an intense back pressure fluctuation induced by combustion spreading upstream through subsonic region of boundary layer.Decreasing the leading edge angle moves separation point of free shear layer ahead,which strengthens the reattaching shock at angled back wall and consequently increases the total pressure loss,in other words,decreases the total pressure recovery coefficient as well as the drag coefficient.This investigation provides insight into the characteristics of flow field inside supersonic combustor with/without combustion and corresponding mechanism of fuel-air mixing enhancement,which is crucial for optimization of the cavity structure.
Numerical study of mixing and combustion performance for magnetohydrodynamic-bypass scramjet
CHEN Rui-feng, WEI Zhi-jun, WANG Ning-fei
2012, 27(5): 999-1004.
Abstract PDF(602KB) icon2027 icon568
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In order to study the mixing and combustion performances of magnetohydrodynamic(MHD)-bypass scramjet(AJAX),the three-dimensional numerical methods were used for the MHD generator flow and the chemical reaction flow,respectly.The combustion entrance conditions were varied by altering the MHD conditions,the mixing efficiencies and combustion efficiencies were got.The results show that as the magnetic field strength increases or load factor decreases,the mixing efficiency is increase,the improved maximum value of mixing efficiency is 11.6%.In the front part of chamber where the thermal dissociation is not sensible,the combustion efficiency is increase;in the latter part of the chamber,while the thermal dissociation is no present,the combustion efficiency are increase,the improved maximum value of combustion efficiency is 6.5%,the combustion chamber is shorten by 25%,reduce the geometric sizes and mass of the vehicle;while the thermal dissociation is present,the combustion efficiency are reduced even lower than the no-MHD case,so it should try to avoid larger magnetic field strengths or smaller load factors to reduce the temperature of the combustion entrance,which cause the thermal dissociation reduce the combustion efficiency.
Premixed combustion model based on laminar flamelet and presumed beta-PDF
YANG Jin-hu, LIU Fu-qiang, XU Gang, ZHU Jun-qiang
2012, 27(5): 1005-1014.
Abstract PDF(1530KB) icon2412 icon684
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Based on the laminar flamelet concept and the presumed beta-PDF(probability density function),a turbulent premixed combustion model was studied.In this model,the laminar flamelet calculation was performed with one dimensional free propagation flame code,PREMIX.The results of the laminar flamelet calculation can be formulated as functions of progress variable and then integrated with the presumed beta-PDF,which produced a lookup table.This model was validated with the calculation of the turbulent Bunsen flame for stoichiometric methane.The results were compared with the results of Zimont model and the experiment,which show that the calculation here can appropriately predict the distribution of average velocity.However,the turbulent kinetic energy and temperature are not so well captured and the mean reaction rate is likely overpredicted,which lead to a shorter flame brush.This is likely because of the exclusion of turbulent stretch effect on the flame surface.A model which can account for the effect of turbulent stretch will be explored in future studies.
Wavelet analysis of features of rotating stall in a combined compressor
SHAN Xiao-ming, YAO Zheng-rong, YUE Lin, HUANG Jin-quan
2012, 27(5): 1015-1021.
Abstract PDF(1663KB) icon1840 icon645
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A fast response pressure probe was applied to test the rotating stall and surge of an axial and centrifugal combined compressor.The pressure signals were analyzed by utilizing the method of the time-frequency analysis based on the Morlet and singular value decomposition.The experimental results indicate that,at the stable condition,there are many main frequency components in the frequency domain but the amplitude is small,while,at the stall condition,the energy of the frequency components becomes larger.In the process of unstall to stall,the larger amplitude of the pressure fluctuation does not produced by the stall cell in this compressor.The compressor enters smoothly into the full stall condition from the modal wave.2 stall cells are measured around annulus and the propagation speed of the stall cell is from 44.8% to 45.9% rotor speed.
Measurements of three-dimensional flow field at exit of a turbine rotor passage in different tip clearances
XIONG Bing, WAN Qian-jun, SHI Xiao-jiang, CHEN Hong-min, MA Hong-wei
2012, 27(5): 1022-1028.
Abstract PDF(2475KB) icon2093 icon807
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The time-resolved flow field downstream of a turbine rotor with different tip clearances was measured using a fast-response four-hole pressure probe.The results show that the flow is obviously periodic due to the rotor.It also indicates that the tip leakage flow has profound effects on the flow field.With bigger tip clearance,the leakage flow is relatively stronger and the secondary flow near the casing wall is weaker.When the tip gap is smaller,the secondary flow near the casing wall becomes stronger.The velocity in the leakage flow region is very low and the loss is high,which leads to substantial flow blockage.The flow under-turning due to the leakage flow is also clearly seen in the measurements.The static pressure in the leakage flow is higher than that in the main flow.The work done by the rotor with bigger tip clearance is lower than that with smaller tip clearance.
Numerical aerodynamic optimization of axial turbomachinery blades based on NURBS
WANG Lu, LIU Hai-qing, ZHANG Hong-wu, YANG Jian-dao
2012, 27(5): 1029-1035.
Abstract PDF(1463KB) icon1640 icon544
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A NASA(National Aeronautics and Space Administration) transonic single stage turbine was taken as an example,describing how to use an aerodynamic numerical optimization platform to find the optimal solution.The platform had three parts:parameterization and fitting of blades,simulation of flow field and optimization strategy.Blades were parameterized based on non-uniform rational B-splines(NURBS) curve.Integrated optimizationstrategy which included DOE(design of experiments) method and genetic algorithm was used to find the global optimal solution.Results show that the performance is improved at the optimized work point.The platform provides a useful reference for analogous optimization of axial turbomachinery blades.
Numerical study on the stator solidity characteristics of axial turbine element stages
YANG Jie, QIAO Wei-yang, HOU Wei-tao, WEI Zuo-jun
2012, 27(5): 1036-1044.
Abstract PDF(1701KB) icon1733 icon596
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For different stator solidity (vane count),an unsteady numerical simulation of turbine element stages was conducted to investigate the influence of stator solidity on the turbine element stage flow and loss status.Results indicate that the stator-solidity-change effects on the turbine element stage flow and loss status were directly associated with the rotor solidity.The change of stator solidity influenced the mass flow rate through the turbine element stage.With rotor solidity fixed,the turbine element stage reaction would change.When the stator solidity increased to a certain extent,shock loss would arise from gas excessive expansion in the stator region,as well as boundary layer separation loss caused by the interference of the shock and boundary layer.When the stator solidity reduced to a certain extent,the flow in the rotor would be greatly deteriorated,with an overlarge negative incidence angle caused great range of separation on the rotor pressure side.There’s one best stator solidity,resulting in the least turbine stage loss.
Full 3-D inverse design optimization method for turbomachinery blade
ZHU Yang-li, WANG Zheng-ming, CHEN Hai-sheng, TAN Chun-qing
2012, 27(5): 1045-1053.
Abstract PDF(1229KB) icon1747 icon588
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Full 3-D inverse design optimization method for turbomachinary blade was studied,which was based on numerical solver of Navier-Stokes equations.Pressure distribution on blade surface was specified for obtaining the corresponding blade profile in inverse problem,assuming there was virtual velocity of grid node on blade surface;blade geometry was modified by the difference between surface pressure and target pressure during iterative procedure.Inverse designs of cascade and optimization example indicate that solution of new blade profile matches target pressure well,which validates effectiveness of this method.The method is practical for engineering applications in time cost and accuracy.
Numerical simulation of aeroelastic response in compressor based on fluid-structure coupling
TAO Hai-liang, ZHU Yang-li, GUO Bao-ting, TAN Chun-qing
2012, 27(5): 1054-1060.
Abstract PDF(1014KB) icon1881 icon630
Abstract:
A numerical simulation method for fluid-structure interaction (FSI) in compressor was presented to predict the aeroelastic stability of blade.Results from steady-state computation were compared with time-averaged experimental data in this paper.On the basis of the steady-state simulation,a flow solver was coupled to a structure solver by using a fluid-structure interface method.The integration of the three-dimensional unsteady Navier-Stokes (N-S) equations was performed in time domain,simultaneously to the integration of a three-dimensional structure model.In the process of coupling,energy transferred from physical interface between fluid and structure.The study shows that the developed fluid-structure method is feasible to predict the aeroelastic stability of blades.The result of numerical simulation shows the response of blade,thus helping to predict the flutter.
Numerical simulation of fouling deposition in compressor rotor
SHI Hui, CHEN Shao-wen, ZHANG Chen, WANG Song-tao, WANG Zhong-qi
2012, 27(5): 1061-1067.
Abstract PDF(1400KB) icon1808 icon550
Abstract:
Three-dimensional numerical simulation to study the influence of fouling deposition on compressor rotors was carried out.As a representative of realistic compressor rotor,the NASA Rotor 37 was considered to perform a numerical investigation and by comparing with the experimental data available from literature,the reliability of commercial CFD(computational fluid dynamcics) computational code was validated.The results show that computed performance maps achieve a good agreement with the experimental data,so it’s practicable using the means of numerical simulations on the study.Then the influence of different fouling deposit degree on compressor rotor performance was simulated by adding surface roughness and thickness on the blade and end-wall.The results indicated that increasing surface roughness and thickness on the blade can make total pressure ratio and isentropic efficiency decrease,and increasing wall roughness can make flow reduce,rotor stable operating range transfer to small flow.Also,increasing blade thickness can make stable operating range decreased obviously,the flow reduced observably at the blockage point,which lead to increase on the deterioration degree of rotor performance.
Platform crack and recrystallization of DD6 single crystal turbine blade
MA Jian, LI Shi-feng, HE Ai-jie, ZENG Jun
2012, 27(5): 1068-1073.
Abstract PDF(759KB) icon2222 icon552
Abstract:
It was found that the cracks appeared on the surface of DD6 single crystal turbine blade platform after testing.Based on the cracks character,the platform failure mode was studied by appearance check,observation on fracture surfaces,microscopic structure examination,and chemical analysis.The results show that the cracks have made from the surface recrystallization of DD6 single crystal turbine blade platform;it has relation to the grain boundary face.Under stress condition,the cracks have expensed along the white particles bond until fatigue failure.Meanwhile,it was found that the recrystallization zone already exists at its surface before application.Owing to the larger cast stress during cast process,the carbide is formatted in platform zone.Then,the recrystallization grain,which mass precipitated phases with W element are around its boundary,is formatted in heat treatment.
Using face name as index in multidisciplinary optimization data linking
LI Li-zhou, LI Lei, WANG Xin-mei, YUE Zhu-feng
2012, 27(5): 1074-1079.
Abstract PDF(1143KB) icon1747 icon578
Abstract:
To settle MDO(multidisciplinary optimization) failure induced by change of geometry model face number,a data-link method,which used face name in replace of face number as data link index,was provided.A program of the method,coded to link SOLIDWORKS and ICEM.CFD,was used in a turbine blade MDO process.The result shows that the method can keep the MDO process correct in a condition that face number changes randomly.
Reliability sensitivity of vibration transfer path systems
ZHAO Wei, ZHANG Yi-min
2012, 27(5): 1080-1086.
Abstract PDF(838KB) icon2269 icon695
Abstract:
The Kronecker algebra,the matrix calculus,the generalized second moment technique of vector-valued functions and matrix-valued functions,and the stochastic finite element theory were the basis of this journal.The effective approach for the transfer reliability and reliability sensitivity for vibration transfer path systems was presented,and the transfer reliability and reliability sensitivity of the vibration transfer path systems with uncertain paths,which included mass,stiffness and position,were analyzed theoretically and computed numerically,and the correlated mathematical expressions were obtained.Thus,in practical project,the most uncertain factors in vibration transfer systems can be considered so as to give the effective way for solving the vibration transfer path systems with uncertain factors,which provide the theoretical foundation for the dynamic design of vibration systems.
Cross-section torsion stiffness calculation of composite rotor blade based on accurate parametric definition
YANG Jian-ling, ZHANG Li-yan, ZHOU Shao-hua, FANG Yong-hong, HUANG Wen-jun
2012, 27(5): 1087-1095.
Abstract PDF(817KB) icon1952 icon544
Abstract:
A new method was proposed to improve the calculation of the composite rotor’s torsion stiffness.First,the flow of the blade’s structure design and analysis were studied.Then,all the material and geometry profile information of the blade construction were obtained by expanding the methods of blade parametric module definition and blade geometric modeling.Finally,the efficient calculation equations for cross-section torsion stiffness of composite rotor blade were derived based on the thin-box beam theory.One of the advantages of the proposed method lies in that the precision loss of model simplification is eliminate by taking the blade’s refined geometric model.On the other side,by importing the ply block,equivalent thickness and slenderness radio conception,and due to the analytical form of the calculation and the automatic geometric extraction,this method is quite suitable for practical use.Experimental results demonstrate that the method can complete the blade structure design and analysis efficiently.
Method for oil-line debris electrostatic monitoring of bearing steel sliding friction pairs
CHEN Zhi-xiong, ZUO Hong-fu, ZHAN Zhi-juan, ZHANG Ying, SUN Jian-zhong, CAI Jing
2012, 27(5): 1096-1104.
Abstract PDF(1341KB) icon2006 icon533
Abstract:
In order to meet the requirements of condition monitoring of oil system component deterioration at an early stage,an oil-line debris electrostatic sensor has been used to investigate real time and in-line wear monitoring in oil lubricated sliding contacts of bearing steel.The charging mechanism of oil lubricated metallic debris was researched and electrostatic monitoring system was designed.The wear experiments were divided into different loads and speeds,and then the friction coefficient,oil-line debris electrostatic signal,and electrostatic signal root mean square (RMS) were obtained and correlatively analyzed.The results show:(1) the oil-line debris electrostatic method and friction coefficient can consistently detect adhesive wear;(2) the electrostatic monitoring method can detect the abnormal signal before adhesion;(3) in the normal wear stage,the friction coefficient increases with the load reduction,and reduces with the speed increase;(4) in the severe wear stage,the RMS of electrostatic signal pulse peak first increase,and then reduces with the load increase,and reduces with the speed increase.
LCF life prediction for TC4 alloy notched specimens based on theory of critical distance
XIN Peng-peng, HU Xu-teng, SONG Ying-dong
2012, 27(5): 1105-1112.
Abstract PDF(704KB) icon2365 icon687
Abstract:
Low cycle fatigue (LCF) life prediction and critical distance analysis for TC4 alloy notched specimens were conducted.The correlation between the critical distance and fatigue life,load ratio,stress concentration factor and their influence on the fatigue life prediction were studied.The result suggests that the critical distance of TC4 alloy is not only related to the fatigue life,but also to the load ratio and stress concentrate factor.For the same load ratio,the power function can be used to describe the relationship between the critical distance and the fatigue life.For TC4 alloy notched specimens,when the load ratios were -1 and 0.1,the critical distance-fatigue life curves almost coincide;when the load ratios rose up to R=0.5,the critical distance increased obviously.For the same load ratio and fatigue life,the critical distance of TC4 alloy notched specimens was approximately inverse to the stress concentrate factor.Life prediction results show that the correlation between critical distance and fatigue life,load ratio,stress concentration factor must be considered to obtain more accurate fatigue life prediction for notched TC4 alloy using the theory of critical distance.
Tomo-TRPIV measurement of coherent structure spatial topology in turbulent boundary layer
JIANG Nan, YU Pei-ning, GUAN Xin-lei
2012, 27(5): 1113-1121.
Abstract PDF(2544KB) icon1875 icon569
Abstract:
The spatial-temporal sequence of 3D-3C(three-dimensional-three-component) simultaneous velocity field in a turbulent boundary layer was finely measured by tomographic TRPIV(time-resolved particle image velocimetry) in a water channel.A new concept of spatial local averaged velocity structure function was introduced to describe the dilation,compression and shear distortion and rotation of multi-scale eddy structures in turbulent flow.The three fluctuating velocity components of TBL (turbulent boundary layer) were decomposed into multi-scale components by spatial local averaged velocity structure function.A new turbulence coherent structure conditional sampling method was proposed based on the dilation and compression features of turbulent multi-scale eddy structures and the new concept of spatial local averaged velocity structure function.The eject and sweep process due to large-scale coherent structure burst was conditionally detected and the characteristic spatial topology modes of physical quantities,such as velocity and vorticity,during coherent structure bursts,were extracted from the tomo-PIV(particle image velocimetry) experimental dataset.A pair of counter-wise quasi-longitudinal horseshoe shaped vortex was discovered during coherent structure eject and sweep process.
Model of rotor aeroelastic stability using dynamics of flexible multbody systems
YU Zhi-hao, YANG Wei-dong, DENG Jing-hui, ZHANG Cheng-lin
2012, 27(5): 1122-1130.
Abstract PDF(714KB) icon1900 icon569
Abstract:
Aeroelastic model of rotor was developed using dynamics of flexible multibody systems.The modeling of components of rotor was independent,so different rotor configurations can be modeled and the model was appropriate for new configuration rotor aeroelastic analysis.A large deflection beam model,suitable for aeroelastic analysis of rotor,was incorporated.To simplify the form of constraint equations,dynamic equations of component including a joint were deduced.To avoid singularities for large rotations,the angular constraint equations,expressed by Rodriguez parameters,were modified by introduced a nominal motion.To verify the correctness of the developed method,the aeroelastic analysis of helicopter rotor and influence study of blade structure parameters were implemented.It demonstrates that the method is very useful for improving computation precision of aeroelastic stability.
Submerged inlet performance improvement with blowing on fuselage
CHENG Dai-shu, SUN Shu, WEN Yu-fen, TAN Hui-jun
2012, 27(5): 1131-1138.
Abstract PDF(1046KB) icon1899 icon654
Abstract:
Due to the large amount of boundary layer ingested into the submerged inlet which results in low total pressure recovery and high flow distortion,a flow control method based on blowing on the fuselage was introduced.By computational method,the models without and with inlet were both studied to obtain the effects of blow technique on the performance and flow structure of submerged inlet.Results indicate that the control method is effective to blow fuselage boundary layer,and improve the boundary layer condition before entrance and the flow in the duct.At the design condition,the total pressure recovery coefficient increased by 1.5% and the distortion index decreased by 6.6% as compared with the baseline case.
Numerical caculation of flow and acoustics fields for separated exhaust nozzle with bypass offset
ZHANG Zheng-wei, ZHANG Jing-zhou, SHAO Wan-ren, SHAN Yong, WU Fei
2012, 27(5): 1139-1145.
Abstract PDF(1287KB) icon1934 icon545
Abstract:
Based on large eddy simulation and FW-H(Ffows Williams-Hawkings) acoustics simulation,the unsteady flow field and the jet noise distribution of overall sound pressure level(OASPL) were obtained for one 1/10 scaled turbofan engine with separated exhaust system at various bypass offset distances.It shows that the structure of bypass offset has the ability of depressing the exhaust jet noise.The noise depression effects have relation with the bypass offset distance.Exhaust jet noise is reduced from 146.7dB to139.5dB at the offset distance of 0.15D which is the maximal noise reduction.The configuration and the numerical method mentioned can be taken into consideration in the design of the separated exhaust for turbo-fan engine.
Finite element analysis on temperature field of bearing with shaft
WANG Yan-shuang, ZHU Hai-feng, LIU Zhe
2012, 27(5): 1146-1152.
Abstract PDF(684KB) icon1875 icon523
Abstract:
Finite element model based on the structure of bearing with shaft was set up.Its temperature field was analyzed by finite element method.First,angular speed of balls was analyzed through quasi-static method.Then power loss was gotten at various inner ring velocities,axial loads and radial loads.Finally,temperature distribution was calculated by ANSYS.Effects on temperature field were analyzed at different operating conditions by examples.The results validated by experiments show that axial load and inner ring velocity can affect temperature distribution strongly,but the effect of radial load is not significant.
Application of envelope spectrum characteristics based on LMD to roller bearing fault diagnosis
YANG Yu, WANG Huan-huan, CHENG Jun-sheng, ZOU Xian-jun
2012, 27(5): 1153-1158.
Abstract PDF(431KB) icon2128 icon497
Abstract:
Most roller bearing fault vibration signals are always multi-component amplitude-modulated and frequency-modulated (AM-FM) signals,however,the selection of central frequency of band-pass filter needs to be determined with experience in conventional envelope analysis method,which would bring demodulation error.To target this problem,a roller bearing fault diagnosis approach based on LMD (local mean decomposition) and envelope spectrum characteristics was proposed.Firstly,by using LMD method,the vibration signal of roller bearing can be decomposed into a set of product functions (PF) whose instantaneous frequencies owned physical sense and each of which was a product of an envelope signal and a purely frequency modulated signal.Secondly,spectrum analysis can be used directly to envelope signal and then the envelope spectrum can be obtained.Finally,the amplitudes ratios in different characteristic frequencies of envelope spectrum were defined as the envelope spectrum characteristics,which served as input parameters of support sector machine classifier to classify working condition and fault patterns of roller bearings.The analysis results demonstrate the effectiveness of the proposed method.
Theory analysis for application grinding disk in face gear grinding
PENG Xian-long, FANG Zong-de, SU Jin-zhan, PEI Shan-shan
2012, 27(5): 1159-1165.
Abstract PDF(820KB) icon2014 icon526
Abstract:
A method of tooth grinding for face gear machining by using grinding disk was proposed with the purpose to manufacture hardened face gear with high precision and obtain parabolic transmission errors and increase transmission stability.The generation theory and grinding disk motion of face gear abraded by grinding disk were analyzed,the surface equation of grinding disk was deduced according to the generation theory,and the double crowned tooth surface equation of face gear was derived based on using grinding disk with mismatch involute and modified movement of grinding disk.The model of tooth contact analysis of double crowned face gear meshing with traditional involute pinion was established.Instances of tooth surface calculation and tooth contact analysis indicate that the method of gear grinding applied to manufacture double crowned face gear through grinding disk is feasible,parabolic transmission errors of face gear can be obtained,edge contact is avoided and is enhanced the stability of transmission.
Study on load sharing behavior of planetary gear train based on deformation compatibility
DU Jin-fu, FANG Zong-de, WNAG Bao-bin, DONG Hao
2012, 27(5): 1166-1171.
Abstract PDF(916KB) icon1881 icon550
Abstract:
The deformation compatibility equations and the torque balance equations were found of the 2K-H-type planetary transmission system based on the characteristic that the system composed a closed-loop of power flow.In consideration of the manufacturing error,assembly error and float of the parts,the load sharing coefficient of each planetary gear was calculated by using the theory of equivalent mesh error and equivalent mesh stiffness.The effects of the errors on load sharing were studied.The study provides useful theoretical guideline for the design of planetary gear systems.
EPDM ablation model considering of porous/compact structure of charring layer
YANG Sa, HE Guo-qiang, LI Jiang, LI Qiang, SUN Xiang-yu, HU Shu-fang
2012, 27(5): 1172-1178.
Abstract PDF(666KB) icon1855 icon678
Abstract:
By analyzing the characteristics of charring layers obtained in ablation motor and simulating erosion motor,the forming and consumption mechanisms of charring layer were analyzed,and ablation model considering the porosity of charring layer was developed.With the model,the charring layer was described as gas-saturated porous media with dense layer and porous layer,thermo-chemical reaction and gas diffusion existed in the pores of charring layer,and the compact structure of charring layer was formed by sediment of decomposition gas.Based on numerical investigation on flow and convection in porous media,a numerical model was presented to simulate the ablation process,and the calculated ablative rates,mass loss rates and the structures of charring layer agree with experimental results.The ablation model has been proved to simulate the process of the thermo-chemical ablation reasonably,and to provide the numerical method for all ablation models considering the thermo-chemical ablation and mechanical erosion.
Particle size effect on ammonium perchlorate decomposition kinetics
Abdel-Wareth W, XU Xu
2012, 27(5): 1179-1184.
Abstract PDF(512KB) icon2151 icon514
Abstract:
The decomposition kinetic parameters of ammonium perchlorate (AP) having different grain size (10-390μm) were investigated through simultaneous DSC/TGA (differential scanning calorimetry/thermal gravimetric analysis) analyzer in a dynamic nitrogen atmosphere under heating rate of 40K/min.The kinetic parameters such as activation energy and pre-exponential factor were determined by the modified isoconversional method.The Brurzauer-Emmett-Teller (BET)-method was applied to measure AP specific surface areas.The results show that the higher the AP particle size the lower the determined kinetic parameters and are matched with some important literatures.
FHA method for FADEC system based on aero-thermodynamics model
DING Shui-ting, QIU Tian, LIU Xiao-feng, LIU Chuan-kai, Gong Lei
2012, 27(5): 1185-1193.
Abstract PDF(677KB) icon2368 icon548
Abstract:
Starting from the airworthiness regulations related to full authority digital engine control(FADEC) system,considering the general principle of functional hazard assessment(FHA) and characteristics of FADEC system,the essential points of FHA for FADEC system were drew.According to the tool and data requirements,a hazard assessment for variable bleed valve (VBV) control function was conducted by using the aero-engine aero-thermodynamics model.The results indicate that:(1) This model could identify engine effect of FADEC system function failure.(2) Model analysis method of functional hazard for FADEC system which could determine engine effect hazard level through quantitative analysis,provides visual information for the assessment and could be a supplement for expert experience.
Adaptive nonlinear predictive control for turboshaft engine
XIAO Ling-fei, HUANG Xiang-hua
2012, 27(5): 1194-1200.
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Abstract:
When the collective pitch of the helicopter main rotor changes,in order to keep the speed of power turbine constant,and improve the dynamic performance,a novel adaptive nonlinear predictive control (ANMPC) algorithm was studied for turboshaft engine control system.Based on the steady states data and the dynamic properties of turboshaft engine,using recursive least square method to realize parameter identification,a numerical-ARX(auto regressive with external input) parallel prediction model which possessed online adaptive ability,was constructed.Then,by multistep output prediction and feedback correction,employing sequential quadratic programming,a ANMPC controller for turboshaft engine was obtained on the basis of receding horizon optimization.The simulation results show that,with the changing of collective pitch,ANMPC controller can make the power turbine speed converge faster,and make overshoot/droop smaller,compared with the conventional series PID(proportional-integral-derivative) controller.

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