2007 Vol. 22, No. 10

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Experimental investigations on the local heat transfer coefficient of rotating single circular impingement in a half-limited space
MAO Jun-kui, BAI Yun-feng, CHANG Hai-ping, PU Ji-xing
2007, 22(10): 1593-1597.
Abstract PDF(732KB) icon1978 icon479
Abstract:
The local heat transfer coefficient Nu of rotating single circular impingement in a half-limited space was studied experimentally.Heated film and thermocouples were used to measure the temperature of target plate and the local heat transfer coefficient Nu was obtained.Jet Reynolds number(Re) of 20 000～35 000 and rotation number(Ro) of 0～0.003 441 were varied to study the heat transfer characteristic of impingement cooling applied under rotating condition.The results show that the Nu is affected greatly by rotation, and the distribution of Nu in rotating condition is quite different from that in stationary condition because of the centrifugal and coriolis forces.With Ro increasing, local and average Nu of target plate increases firstly and then decreases.And the Nu of single circular impingement increases with Re increasing, which is the same as that in stationary case.
Experimental investigations on round jet impingement on flow structures of convex surface target with narrow space
MAO Jun-kui, LIU Zhen-xiong, GUO Wen
2007, 22(10): 1598-1603.
Abstract PDF(811KB) icon2011 icon464
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The flow structure of convex surface target with narrow space under round jet impingement was investigated by smoke wire flow visualization.Reynolds number Re(750-1500), the ratio of the jet impingement distance to the diameter of the jet hole H/d(0.2-1), and the relative curvature d/D were modified in this experiment.The changes of flow separation angle and vortex dependently of above-specified parameters were analyzed through capture of flow field state.The results shows that, when Re, H/D are larger, a stable vortex is generated at two sides of the convex surface.With the increase of Re and H/D, the air separation is delayed when the radius angle of jet flow corresponding to surface separation increases.It was also observed in the experiment that the separation was caused in advance and the corresponding radius angle decreased when d/D declined.
Influence of pin fin on the convective heat transfer characteristics of turbine blade trailing edge
SONG Shuang-wen, HU Hao-sheng, YANG Wei-hua, ZHANG Jing-zhou
2007, 22(10): 1604-1608.
Abstract PDF(1276KB) icon1562 icon430
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In order to study the convective heat transfer characteristics of turbine blade trailing edge influenced by the pin fin, four kinds of pin fins were designed and the film cooling characteristics with pin fins of diverse shapes and alignments were studied by an experimental method using infrared cameras.The result shows that, when the blow ratio is low, the convective heat transfer performance of turbine blade trailing edge with water-drop-shaped pin fin I is better than others;and when the blow ratio is high, the convective heat transfer performance of turbine blade trailing edge with the column-shaped pin fin Ⅱ is better, and the convective coefficient of turbine blade trailing edge with the water-drop-shaped pin fin Ⅱ is the smallest.At the same position of the trailing edge, the convective coefficient increases with the increase of the blow ratio.
Numerical evaluation on infrared radiant intensity of exhaust system of turbine engine without afterburning
LUO Ming-dong, JI Hong-hu, HUANG Wei
2007, 22(10): 1609-1616.
Abstract PDF(2214KB) icon2168 icon540
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The numerical calculation method of infrared radiant intensity of exhaust system of turbine engine without afterburning was studied.Due consideration was given to emission and reflection of solid wall, absorption and emission of water vapor, carbon dioxide and carbon monoxide in the gas.This method was used to calculate the infrared radiant intensity of a scaled model of turbofan exhaust system, and compare with the experimental results.These results show that, this method could help you calculate accurately the infrared radiant intensity of turbine engine at waveband of 35μm, showing an engineering practicability.
Experimental study on mechanism of shock-flame interactions in detonation tubes
ZHANG Peng-gang, HE Xiao-min, LI Jian-zhong, ZHANG Jing-zhou
2007, 22(10): 1617-1621.
Abstract PDF(1075KB) icon1444 icon479
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A series of single detonation experiments were conducted to study the performance of acetylene-air mixtures in square detonation tube.The ion-probes and pressure transducers were utilized to measure the flame velocity and pressure in the tube, respectively.The process of shock-flame interactions was analyzed through different triggering times between ion-probes and pressure transducers.The results indicate that the compression wave occurs always in front of flame without detonation in the smooth tube.With introduction of detonation tube of BR=0.4, detonation occurs in the tube;the flame is in front of shock within the obstacle section, or reversely outside of obstacle section.
Thrust correction on the test bench of pulse detonation engine under air-breathing condition
FAN Yu-xin, WANG Jia-hua, LI Yang
2007, 22(10): 1622-1626.
Abstract PDF(668KB) icon1418 icon457
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Influences of nozzle size and flow dynamic pressure at fan exit on test bench thrust value of pulse detonation engine were studied.Means of eliminating these influences were explored.The results show that the test bench thrust is on the low side due to the outer resistance of PDE.The outer resistance is managed to be removed by a force sustained shell installed outside of the inlet, thus true thrust is achieved.A thrust correction model was brought forward and validated by test.
Investigation on thermodynamic performance of pulse detonation engine with 180 mm
LIU Hong, WANG Jia-hua, ZHANG Yi-ning, TANG Hao, ZHANG Jing-zhou
2007, 22(10): 1627-1631.
Abstract PDF(466KB) icon1497 icon452
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The performance of Pulse Detonation Engine(PDE) with aerovavle of diameter 180 mm、length 2.2 m was pre-estimated by using a method combining experiential data and computation, at the same time the total pressure loss inside the PDE was taken into account.The computational results basically match the results obtained from the experiments.It was found that the thrust of PDE was lower than that in ideal case and specific fuel consumption(SFC) was larger than that in ideal case, due to that the total pressure loss was considered.This computational method is valuable for pre-estimating the performance of PDE in actual operation.
Reliability test in pressure measuement of detonation combustor
ZHANG Yi-ning, WANG Jia-hua, HE Xiao-min, ZHANG Peng-gang, HAN Qi-xiang, ZHANG Jing-zhou
2007, 22(10): 1632-1638.
Abstract PDF(2126KB) icon1536 icon419
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To improve the reliability of pressure measurement in detonation combustor of pulse detonation engine(PDE), the pressure/time curves of detonation were measured at single detonation and multicycle detonation, respectively, by using a dynamic pressure measurement system.The experimental study at single detonation reveals that, if the length of branch tube is less than 100mm, the peak value of detonation pressure can be measured;if the length of tube is more than 150mm, the flame cannot propagate within the branch tube, and only platform pressure after detonation could be measured.For multicycle detonation, if the length of cooling tube is short enough, the detonation pressure can be measured.The research results resolve the reliability problem of pressure measurement on multicycle detonation.
Experimental study of effects of geometric parameters on combustion performance of dual-stage swirler combustor
DANG Xin-xian, ZHAO Jian-xing, JI Hong-hu
2007, 22(10): 1639-1645.
Abstract PDF(2172KB) icon1833 icon442
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Under different fuel-air ratios, the effects of geometric parameters of dual-stage swirler and the arrangement of primary holes, on combustion performance(exit temperature distribution, combustion efficiency, lean blowout limit and pollutant emission) of single-head rectangle combustor are studied experimentally.The experimental results show that, the geometric parameters of dual-stage swirler and the arrangement of primary holes(swirler passage area, swirl vane angle of the primary and secondary swirler, the distance of the flare exit from throat, etc) have great influence upon the combustion performance of combustor, but the effects decrease with the reduction of fuel-air ratio.
Numerical analysis of combustion performance of EBMC flame holder
MA Wen-jie, YANG Yang, YANG Mao-lin, FAN Wei-jun
2007, 22(10): 1646-1651.
Abstract PDF(1085KB) icon1672 icon442
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In order to verify the combustion performance of EBMC flame holder in wider operating range, numerical simulation of the combustion process was carried out.The influence of the jet velocity, jet equivalence ratio and the approach velocity on combustion efficiency was analyzed, meanwhile the simulated results were compared with combustion performance of common V-shaped stabilizer, showing the influence of above-specified factors on the combustion performance of flame holder.On a comparative basis, the results show that the influence of such variables on combustion performance corresponds almost to earlier experimental results in narrower operating range, despite of some differences in some aspects.
Influences of turbulence models on heat transfer of guide vane surface
ZHU Yan-wei, ZHU Hui-ren
2007, 22(10): 1652-1657.
Abstract PDF(1030KB) icon1754 icon430
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In order to study comparatively the influences of turbulence models on heat transfer of the vane surface, five turbulence models and two wall functions were employed to calculate the surface heat transfer coefficients of NASA-MarkII guide vane and then compare with the calculated results.The results show that: the calculated results of different turbulence models differ a lot under the same boundary conditions.If different near-wall treatment functions are used, the calculated results may differ greatly even for the same turbulence model.Some turbulence model' s calculated results are only satisfactory in some area of the vane surface.However, no turbulence models are found to make the calculated results very close to the experimental data.In the absence of turbulence models with good universality, the calculation technique with different turbulence models and near-wall treatment functions for different domain is a feasible solution in simulating the heat transfer of vane surface.
Experimental research on heat transfer of "impingement/effusion" double-plate configuration in rotating state
XU Lei, CHANG Hai-ping, PAN Jin-dong
2007, 22(10): 1658-1662.
Abstract PDF(671KB) icon1776 icon481
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Based on the internal cooling turbine blade of high-performance aeroengine, the internal heat transfer characteristics of double-plate configuration with film cooling have been carried out in rotating state.The test was performed in the same and opposite direction of rotation.Thus, the effect of jet Reynolds numbers Rej(5 000～10 000), rotation numbers Ro(0～0.003 532)and wall-to-jet temperature difference ratios(Tw-Tf)/Tw(0.061～0.136)on heat transfer characteristics of impingement was obtained.By comparing the experiment results of both double-plate configuration and general configuration of impingement/effusion structure, it is observed that the heat transfer of double-plate configuration is 15% stronger than that of general configuration.
Study of convective heat transfer in channels with different geometrical ribs
LI Jian-hua, SONG Shuang-wen, YANG Wei-hua, ZHANG Jing-zhou
2007, 22(10): 1663-1666.
Abstract PDF(923KB) icon1422 icon471
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In order to study the heat transfer characteristics of channels with different ribs, 4 kinds of channels with different ribs were designed and the heat transfer characteristics of them were experimentally studied;the influence of different ribs and the impingement Re on their heat transfer characteristics were analyzed.The results show that the heat transfer characteristic at the region of stagnation point is different from that at rib region, and the heat transfer characteristic of channel with V-shape ribs is better than others.
Back pressure simulation by cavity injection and its application in hypersonic inlet experiment
SUN Shu, ZHANG Hong-ying, CHENG Ke-ming, WU Yi-zhao
2007, 22(10): 1667-1672.
Abstract PDF(752KB) icon2012 icon456
Abstract:
A kind of back pressure simulation technology by cavity injection is brought forward to improve wind tunnel test capability for hypersonic inlets.During wind tunnel test process, the back pressure of inlet can be adjusted rapidly by regulating the valve of injection pipe.Utilizing this specific simulation technology, the performance at different back pressures and the unstarting/restarting characteristics of an axisymmetric inlet are investigated.The design Mach number of the inlet is 7.0.Results indicate:(1) The newly developed simulation technology can form fairly average and easily controllable back pressure downstream the inlet, so it can be used to investigate the back pressure characteristics of hypersonic inlets.(2) By regulating the valve of injection pipe, the simulation technology can realize the switch of hypersonic inlet started state and unstarted state in about 8 milliseconds, so it is suitable to investigate the starting/unstarting/restarting problem of hypersonic inlets.
Study of SIMPLE algorithm for compressible flows on non-staggered grids
FU Xiao-yan, GAO Ge
2007, 22(10): 1673-1677.
Abstract PDF(468KB) icon1928 icon443
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Based on Rhie-Chou momentum interpolation, a SIMPLE algorithm for compressible flows of non-staggered grids was deduced.With this method, the inviscid flow in a channel with a bump and shock/boundary-layer interactions were computed.If HLAP scheme is adopted for convection term, the hybrid scheme is applied to density interpolation.This method can simulate efficiently both compression waves and expansion waves in supersonic flows.With the help of GAO-YONG turbulence models, it' s possible to simulate satisfactorily the shock/turbulent boundary-layer interaction in a channel.
A computational study of 2-D dual-throat fluidic thrust-vectoring nozzles
TAN Hui-jun, CHEN Zhi
2007, 22(10): 1678-1684.
Abstract PDF(967KB) icon1870 icon487
Abstract:
Numerical studies on 2-D dual-throat fluidic thrust-vectoring nozzles were performed to obtain the key design rules.Results show that length of primary nozzle cavity, divergent cavity ramp angle, convergent cavity ramp angle and height of upstream primary nozzle throat have great influence on thrust ratio, thrust vectoring efficiency and the internal flow patterns.The optimal package of parameters is: 2.61, 10°, 30°, 1.0 and 150°, respectively(the length scale is normalized by the height of downstream primary nozzle throat).This package can achieve a pitch thrust vector angle of 14.34° and a thrust ratio of 0.967 in the case of a primary flow pressure ratio 4, secondary/primary flow pressure ratio 1.08 and mass consumption of 2.5%.
Load deformation compensation of the axisymmetric vectoring exhaust nozzle
WANG Yu-xin, WANG Yi-ming, LI Yu-tong
2007, 22(10): 1685-1689.
Abstract PDF(1960KB) icon1551 icon485
Abstract:
The compensation of the load deformations for axisymmetric vectoring exhaust nozzle(AVEN) under heat field and aerodynamic forces was analyzed.The correlation between expansion plates and suspension kinematic chains was set up, while a differential equation for the joint displacement increments and length increments of suspension kinematic chains was introduced.Then, the analytical expression for the deviations of the area/vector deflection angle of the exhaust nozzle caused by the load deformations was expressed analytically.With the aid of the relationship among the deviations of the nozzle and the pose parameters of the driving platform of the AVEN, the dynamic compensation equation for correcting the deviations of the AVEN caused by the heat field and forces was deduced.The research results show that, the relative error of the area and deflection angle of AVEN is less than 1% after compensation.
Inverse simulation research on pneumatic characteristic of aeroengines under steady state
CHEN Li-hai, YANG Qing-zhen
2007, 22(10): 1690-1694.
Abstract PDF(622KB) icon1729 icon508
Abstract:
The integral aerodynamic design of aircraft and its propulsion system becomes a difficult task due to the lack of steady pneumatic parameter data of the engine.While the discrete test run data of an aero-engine was adapted using the high order multi-parameters polynomial fit method, the steady characteristic curves were founded.The inverse simulation of pneumatic characteristics for the engine was thus performed, and the state characteristic curves of flow parameters at inlet and outlet of the engine were created, thus providing a basis for integral design of the aircraft and its engine.
Parallel design of turbo engine and three-dimensional nozzle
CHEN Yu-chun, HUANG Xing, GAO Ben-bing, YE Wei, ZHANG Hong
2007, 22(10): 1695-1699.
Abstract PDF(962KB) icon1828 icon553
Abstract:
In order to solve the problem of mass flow match between aero-engine and nozzle in the performance simulation, 0-D engine performance simulation programs and 3-D mixer and nozzle computation fluid dynamics software were integrated into iSIGHT platform.The method was presented solving the mass flow match and integrating multi-level of complexity analysis techniques(Zooming technology) that captured the appropriate physics of mixer and nozzle at the 3-D state for engine systems.By means of iteration computation of programs between 0-D and 3-D, the models and areas of the mixer and nozzle were adjusted automatically.The thrust coefficient and flow coefficient of nozzle were obtained at the same time.This method may provide a reference to application of Zooming technology in other parts of turbofan engines.
Experimental investigation of wall static pressure distributions of shock induced axisymmetric fluidic vectoring nozzle
JIN Jie, LEI Jin-chun, LIAO Hua-lin, ZHAO Jing-yun, LIU Zhi-gang
2007, 22(10): 1700-1703.
Abstract PDF(615KB) icon1958 icon469
Abstract:
A scaled experimental investigation has been conducted to determine the wall static pressure distributions of a shock induced axisymmetric fluidic vectoring nozzle with a slot in its divergent section when the nozzle pressure ratio(NPR) was 3～10 and the flow flux ratio of the secondary flow injection to the primary flow(Ws/Wp) was 0%～20%.The results indicate that the internal flow characteristics are complex 3-Dimensional, for the secondary flow injection resulting in discrepancy of the circumference wall static pressure.NPR and Ws/Wp influence greatly the wall static distributions and under certain conditions they would influence the flow of the convergent section of the nozzle.When NPR=4, Ws/Wp≥15%, the shock waves may hit the lower flap which is farthest to the secondary flow injection in circumference direction, separating flows and bringing on higher wall static pressure.
Experimental study of flow characteristics of inlet /internal flowpath for a hypersonic flight vehicle
WANG Cheng-peng, ZHANG Hong-ying, SUN Shu, WANG Jiang-feng, CHENG Ke-ming
2007, 22(10): 1704-1709.
Abstract PDF(689KB) icon1823 icon478
Abstract:
The flow field structure and starting characteristics of two-dimensional inlet/internal flowpath for an airbreathing hypersonic vehicle was analyzed using Ma∞=7 wind tunnel test method.The experimental results show that:if the inlet flowpath is started under incoming total pressure(0.5～1.9 MPa) and unit Reynolds number(2.48×106～7.95×1061/m), the variation of the incoming total pressure and Reynolds number has little effect on the static pressure distributions along inlet/internal flowpath;the inlet-isolator could withstand maximum back pressure 250 times the free-stream static pressure, before flow in the inlet compression section is disturbed;the inlet has a self-starting ability if no lateral plate is added, and the outlet pressure at the isolator increases if lateral plates are added before the cowl;under the working condition at the design point, the inlet flowpath has a compression ratio 42.9, total pressure recovery of 0.27, and mass-weighted average Mach number of 2.76.
Investigation of two-phase flow in supersonic crossflow based on two-fluid method
LI Dong-xia, XU Xu, CAI Guo-biao
2007, 22(10): 1710-1714.
Abstract PDF(494KB) icon1687 icon443
Abstract:
Two-fluid model was employed to simulate two-phase phenomena of supersonic crossflow.Calculations were carried out under different diameter droplets and different momentum flux ratio conditions respectively to examine how they affected flow field.Numerical simulation results show that the cross-stream penetration of the jet is influenced evidently by the droplets diameter and momentum flux ratio;and the downstream flow of the muzzle changes when the droplet diameter or momentum flux ratio varies.The calculation results agree well with experimental results.
Numerical investigation on IGV/impeller interaction in a centrifugal compressor stage
ZHOU Li, XI Guang, CAI Yuan-hu
2007, 22(10): 1715-1721.
Abstract PDF(1894KB) icon1606 icon484
Abstract:
Numerical simulations on the unsteady inlet guide vane(IGV)-impeller interaction were performed under different prewhirl angles.The main factors to IGV-impeller interaction were also discussed to analyze the influence of unsteady flow effect upon flow field of impeller.The results show that the impeller flows periodically under large negative prewhirl angle.In such case, the wake of IGV outlet, especially the large size vortice formed behind IGV, was the key factor to strong unsteady flow in the downstream impeller inlet.The unsteady influence of IGV wake involved only a part of impeller passage(about 30 percent of the blade chord), and the potential repercussion of the impeller ranged from IGV trail edge to 20 percent of the chord.Both the passing frequency and rotating frequency of the blade have influence on the unsteady flow in IGV.
Analysis of influential factors to tip leakage mixing loss
SHAO Wei-wei, JI Lu-cheng, CHENG Rong-hui, HUANG Wei-guang
2007, 22(10): 1722-1729.
Abstract PDF(2849KB) icon1676 icon482
Abstract:
A basic relational model for tip leakage mixing loss of unshrouded blades for compressible flow was derived from theoretical analysis of Denton.Relationship.It reflected the influential factors such as blade surface static pressure, chordwise distribution of tip clearance, discharge coefficient and total pressure loss coefficient in the tip region.While only the mixing loss of tip leakage was considered, numerical analysis was performed for the influence of basic load of tip, clearance, average level and chordwise distribution upon mixing loss.The results clearly indicate the governing actions and mechanisms of various factors against the tip leakage mixing loss.Finally, an important combination parameter was put forward to reflect the overall influence of blade loading and tip clearance distribution on the tip leakage mixing loss.
Study of energy release rates for crack deflection of ceramic matrix composites
ZHANG Hong, SONG Ying-dong
2007, 22(10): 1730-1736.
Abstract PDF(2280KB) icon1572 icon457
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The energy release rates of different crack paths at interfaces were estimated by using virtual crack closure technique(VTTC).An energy criterion based on the energy release rates was used to study the crack deflection of ceramic matrix composites.Meanwhile, and the effects of elastic mismatch parameters α and β, the crack growth length a and the relative crack growth length ad/ap on the crack deflection were analyzed.The VCCT results were compared with those obtained by integration method.The results show that, VCCT can accurately calculate the energy release rates of crack growth, providing a reference for study of failure mechanism of ceramic matrix composites.
Experimental research on particle damping of cantilever beam
XIA Zhao-wang, SHAN Ying-chun, LIU Xian-dong
2007, 22(10): 1737-1741.
Abstract PDF(984KB) icon1935 icon456
Abstract:
The nonlinear change characteristics of dampers dependently from particle parameters were analyzed based on the cantilever beam with filling particles.And, the influence of changing parameters of particles and structures on the damping effect was also studied systematically.The results show: particle damper enables the damping ratio to reach up to 492%;the damping effect improves with the growing density of particles;the best damping ratio occur at the filling ratio of 70%;the particle damping effect is improved when particles are embedded into holes with higher amplitude of vibration.
Experimental research on impact damage and residual tensile strength of composite laminates
CUI Hai-po, WEN Wei-dong, XU Ying
2007, 22(10): 1742-1747.
Abstract PDF(1102KB) icon1670 icon475
Abstract:
T300/BMP316 is a promising composite on aeronautic and aerospace structures.The experimental research was performed on impact damage and residual tensile strength of T300/BMP316 composite laminates with different layer parameters.The results show that, layer parameters have effect on long-axis direction of impact damage figure, rather than the impact damage area.The residual tensile strength of laminates is not directly related to the impact damage area.
Application of adaptive genetic neural network algorithm in design of thrust estimator
YAO Yan-long, SUN Jian-guo
2007, 22(10): 1748-1753.
Abstract PDF(693KB) icon1691 icon469
Abstract:
An adaptive genetic neural network algorithm(AGNNA) was proposed for estimating aeroengine thrust accurately and easily in a full flight envelope.It is based on the combination of genetic algorithm and neural network technology which could make full use of the global convergence property and rapid local searching capability separately.The topology structure and weights(including threshold) of neural network could be directly optimized through adaptive probability genetic operator and local optimizing operator, thereby overcoming the disadvantage of hidden layer nodes of neural network requiring empirical effort and the sensitivity of neural network to its initial weights(including threshold).Then, neural network was applied to "fine-tune" the above-specified weights(including threshold).Finally, the thrust estimator for the full flight envelope was designed with the algorithm.The experimental results show that the thrust estimator has good estimation accuracy and generalization ability.
Research on sensor fault diagnosis for a given turbofan engine based on SVR
LI Ben-wei, FAN Zhao-yuan, WANG Yong-hua, YIN Da-wei, JIANG Ke-yi
2007, 22(10): 1754-1759.
Abstract PDF(1890KB) icon1609 icon422
Abstract:
A sensor fault diagnosis system with support vector regression(SVR) for a given turbofan engine was designed.It can detect sensor fault and recover fault-sensor signal.On the basis of training the SVR model with the trial run data of one turbofan engine, the system was simulated in the MATLAB through three different kinds of sensor fault, i.e.offset fault, impact fault and drift fault.The results show that the system has many advantages including high level of precision and good real-time performance.So SVR is an effective method for sensor fault diagnosis.
Analysis of modification and high-altitude adaptability for fuel flow regulator of a turbofan engine
SU San-mai
2007, 22(10): 1760-1764.
Abstract PDF(658KB) icon1627 icon485
Abstract:
In order to increase the thrust and flight adaptability of a small turbofan engine, the fuel flow regulator modification of original engine was required to provide theoretical support for modification.The operating principle of fuel flow regulator was mainly analyzed to establish a static and acceleration/deceleration control mathematical model, and then analyze the high-altitude adaptability.Finally, some modification methods and measures were recommended.
Numerical simulation on three-dimension supersonic jet of missile vertical launching system
XU Yue, ZHANG Zhen-peng, TIAN Ai-mei, CHEN Xiao-qing
2007, 22(10): 1765-1770.
Abstract PDF(1873KB) icon1679 icon447
Abstract:
The three-dimensional turbulent flow fields of missile Vertical launching system(VLS) are computed.Cell-centered finite-volume method and 3rd-order upwind spatial differencing with TVD option is applied for Navier-Stokes governing equations.Dual-time stepping and preconditioning procedure are utilized for improving the calculating convergence velocity. The diagonalized, dual-time ADI algorithm is employed to integrate the governing equations.Shock forming in the plenum chamber is simulated accurately.The complex flow pattern in Vertical Launching System was described veritably.The current studies show that the pressure of jet center at the bottom of plenum chamber oscillates with a frequency about 1200Hz.
Nonlinear dynamic response analysis of unbalance-rubbing coupling faults of rotor-ball bearing-stator coupling system
CHEN Guo
2007, 22(10): 1771-1778.
Abstract PDF(2474KB) icon2719 icon502
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A new rotor-ball bearing-stator coupling dynamic model was established for the unbalance-rubbing coupling faults.In the model, the rotor mass unbalance and rubbing faults were fully considered.The nonlinear factors of ball bearing, such as the clearance of bearing, nonlinear Hertzian contract between balls and races, and the varying compliance(VC) of bearing support were modeled.Moreover, the numerical integral method was employed to obtain system' s responses, whereas the bifurcation and chaos motion were analyzed, followed by the effects of rotational speed, rubbing stiffness, rotor eccentricity, bearing house-stator stiffness, and stator-foundation stiffness on dynamic responses.Therefore, the non-linear dynamic response laws of rotor-ball bearing-stator system under unbalance and rubbing coupling faults were obtained.
Improved Hilbert-Huang transform and its application in rotor-stator rub
HE Tian, LIU Xian-dong, SHAN Ying-chun, LI Qi-han
2007, 22(10): 1779-1784.
Abstract PDF(2161KB) icon1644 icon415
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In order to overcome the shortages of Hilbert-Huang transform(HHT), an improved HHT was proposed by the energy analysis method based on the singularity value decomposition of the track matrix reconstructed by time series, and a method for judging the pseudo-IMFs by empirical mode decomposition(EMD) was also presented.The advantages of improved HHT were verified from simulation signals.Then, the improved HHT was applied to detect the slight rubbing simulation of dual-rotor aero engine.The simulation results were compared with previous HHT and wavelet transform, respectively, showing that the improved HHT has the advantage of separating efficiently the weak component of signals from other strong components, and also confirming the slight rubbing more easily.The analytical results provide a useful reference for diagnosing the fault of rubbing.

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