2011 Vol. 26, No. 12

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Experimental investigation on heat transfer in complex internal cooling blade channel with leading-edge
WU Hong, LIU Yu-sheng, XU Guo-qiang
2011, 26(12): 2641-2647.
Abstract PDF(1164KB) icon2150 icon14
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Heat transfer characteristics of complex serpentine channels with leading-edge impingement in static turbine blade were investigated using the transient thermochromic liquid crystal technique under different Reynolds numbers.Distributions of local heat transfer coefficient at different positions were obtained on both pressure and suction sides.Experimental results show that:local heat transfer between two ribs is stronger than that in smooth region on inner surface of blade channels.A single heat transfer peak occurs between two adjacent ribs along the flow direction.With increase of Reynolds number,heat transfer is enhanced on all surfaces and centrifugal effect of fluid is strengthened in non-rib area downstream the bend,resulting in uneven distribution of local heat transfer there.However,ribs after the bend can reduce this effect significantly.Besides,mainstream speed changes caused by expansion and contraction of channel cross-section also influence the values and distributions of local heat transfer.
Heat transfer and friction behavior in internal cooling duct with cuniform-fins
QIU Qing-gang, WANG Hai-peng, ZHAO Liang, SHEN Sheng-qiang
2011, 26(12): 2648-2654.
Abstract PDF(995KB) icon1918 icon11
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Experimental and numerical methods were applied together to investigate the influence of cuniform-fin geometry parameters on heat transfer and friction behavior in helix-alike internal cooling channel of the gas turbine blades.The numerical results were compared with the experimental data,and they agreed very well with each other.Results show that,with the increase of helix-alike fin leading angle,heat transfer enhancement is improved more significantly and at the mean time pressure penalty also becomes higher in the internal cooling duct.The results also indicate that air flow direction has less effect on heat transfer enhancement,but the flow resistance with reverse coolant direction is markedly higher than that with normal coolant direction.In addition,based on the results of the numerical simulation,the configuration of fins with leading angle 7? and fluid flow with normal coolant direction give the best overall performance.
Experiment investigation of windage heating on straight-through labyrinth seals with honeycomb bush
JI Guo-jian, JI Hong-hu, HUANG Yun-xia, SHUAI Hai-shan, LU Hai-ying, WANG Hai
2011, 26(12): 2655-2660.
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Experiment investigation of windage heat on straight tooth and slant tooth of labyrinth seals composed of three teeth and two cavities with honeycomb bush and smooth bush had been made to study the effect of rotating speed and the pressure ratio of inlet to outlet and structure of tooth and bush.The results show that the total temperature of leakage fluid caused by windage heat may be neglected at low rotor speed and is increased with the increasing rotation speed between 3000r/min and 6000r/min.The total temperature ratio of first tooth to all teeth is more than 50% with smooth bush and is only 20% with honeycomb bush under low pressure ratio and enhanced to 50% with the increase of the pressure ratio.The straight tooth show increased windage heat when compared to slant tooth with the same bush due to the larger extension length of seal surface curve.
Experimental study on outlet temperature field in multipoint injection combustor-sector
ZHANG Zhen-kui, ZHONG Hua-gui, FENG Da-qiang, WANG Fang-ping
2011, 26(12): 2661-2666.
Abstract PDF(1209KB) icon2151 icon11
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The experimental study on outlet temperature field in a multipoint injection combustor-sector was finished on high-pressure test facility of annular combustor in GTE(China Gas Turbine Establishment) .Experiment results indicate that the multipoint injection combustor can control the outlet temperature filed redistribution through adjusting fuel injector switches.This control would increase the overall temperature distribution factor causing by switching and reduce radial temperature distribution factor.The combustion efficiencies of multipoint combustor and conventional combustor are fairly consistent,indicating that the multipoint injection combustor is feasible.The results have considerable significance for the designs of similar combustors.
Experimental investigation on transpiration cooling of trapped vortex combustor
ZHANG Rong-chun, FAN Wei-jun, SONG Shuang-wen, XING Fei, KONG Xiang-lei
2011, 26(12): 2667-2675.
Abstract PDF(1177KB) icon1826 icon17
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Two kinds of transpiration cooling schemes of trapped vortex combustor were designed,and two angles of transpiration cooling holes were 30 ? and 150 ?.The cooling efficiency test was conducted to study the performance of cooling in different locations,different temperature ratios and blowing ratios.The experimental results show that two cooling structures have high cooling efficiency;and the cooling efficiency variation with mainstream temperature or blowing ratio is similar to each other.For the wall of cavity,the cooling efficiency of fore-wall is the highest and the cooling efficiency of after-wall is the lowest.Under the same experimental conditions,the cooling efficiency of the structure at angle 150 ? is higher than that of the structure at angle 30 ?.At the same time,with the decline of cooling gas rate,the difference between them will increase.Finally,the test results were analyzed by numerical methods.
Analysis on installation location of probe-style ice detectors
ZHU Cheng-xiang, SUN Zhi-guo, FU Bin, ZHU Chun-ling
2011, 26(12): 2676-2683.
Abstract PDF(1103KB) icon2136 icon13
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Navier-Stokes(N-S)equations were solved to obtain the air-flow field around the geometry,and Eulerian method was used to obtain the water droplet trajectories.Based on these results,generalized shadow height of water droplet could be calculated by computing the vertical distance between the geometry and the freestream liquid water content (LWC) isoline.Generalized shadow height of water droplet under various flight and meteorological conditions were calculated.Locations of probe-style ice detectors were determined according to the installation requirement.With the results,effects of various flight and meteorological parameters on generalized shadow height of water droplet were analyzed,providing a guidance for choosing appropriate calculation conditions for the installation location of ice detector.
Development and calibration of heat transfer coefficient sensor for rotational state
QUAN Yong-kai, XU Guo-qiang, LUO Xiang, ZHANG Da
2011, 26(12): 2684-2690.
Abstract PDF(872KB) icon1505 icon15
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A novel heat transfer coefficient sensor is introduced and the design, manufacture,and calibration are described.The intended application of this instrument was on a high rotational speed test disc. In the experiments,the heat transfer coefficient sensor was calibrated under static state and rotational state respectively. The calibration under the static state was accomplished in a pipe: the inside diameter (ID) was 0.048m and the total length was 4m, the distance between the sensor and the inlet of the pipe was 3.5m; the standard value was measured using a self-made calibrator. The calibration under the rotational state was accomplished using a rotating disc: the diameter and thickness of the stainless disc were 800mm and 25mm, respectively;the sensor was installed at the location of r =250mm; the rotating disc driven by a 30kW direct current motor can supply the maximum rotational speed of 3000r/min. The standard value under rotational state was provided by an approximate empirical formula. The results show that the designed sensor can measure heat transfer coefficient directly under rotational state and static state with good accuracy and stability; the correlation factor of K are constant under static state and rotational state.
Calibration of pressure-sensitive paint and application to the measurement of film cooling effectiveness
ZHANG Chao, WANG Zhan, ZHOU Si-jing, LIU Jian-jun
2011, 26(12): 2691-2697.
Abstract PDF(895KB) icon1795 icon17
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Calibration of pressure sensitive paint was carried out by using the self-designed calibration setup.The influence of excitation light intensity and temperature on the calibration curve was investigated.The experimental results showed that the effect of excitation light intensity was negligible when the excitation light intensity was sufficient to cause the oxygen quenching of luminescent molecules,but the calibration curve was more sensitive to the temperature change.The expression of emission light intensity about pressure ratio and temperature ratio was proposed based on two-dimensional interpolation method,and the measurement results were corrected to account for temperature change effects.Then the pressure sensitive paint technology was applied to the film cooling effectiveness measurement of cylinder film hole and fan-shaped film hole,and the experimental results compared well with the previous experimental data.
Experiment on drop of cooling air temperature and flow loss performance of pre-swirl cooling system
ZHANG Jian-chao, WANG Suo-fang, YANG Shou-hui, KUANG Kai-xin
2011, 26(12): 2698-2703.
Abstract PDF(875KB) icon2068 icon15
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The effect of rotational Reynolds number and non-dimensional mass flow rate on the drop of cooling air temperature and flow loss of a simplified aero-engine pre-swirl system were investigated experimentally for two pre-swirl angles.A test rig was set up.Micro pressure transducers for measuring pressure of rotating disk surface were fixed on the disk,and the relative total pressure of the outlet of the pre-swirl system was obtained after calibrations.The rules of influences on drop of cooling air temperature and flow losses performance of pre-swirl cooling system were achieved.This shows that the cooling air temperature rises and then goes down with the increase of non-dimensional mass flow rate in the range of this study and these two pre-swirl angles,and decreases with the rising rotational Reynolds number;non-dimensional flow loss increases with the enlargement of non-dimensional mass flow rate,and decreases with the increment of the rotational Reynolds number.
Numerical simulation of rotationally-induced ingress through turbine rim seals
ZHOU Kun-yuan, LUO Xiang, XU Guo-qiang
2011, 26(12): 2704-2709.
Abstract PDF(933KB) icon1867 icon13
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In the turbine stage of the aero-engines,the rotation of disk can cause high-temperature gas in annulus ingest into the rotor-stator system through rim seal.Computational fluid dynamics (CFD) was applied to study the so-called rotationally-induced (RI) ingress through an axial seal clearance.The variation of the cavity pressure and the radial velocity at the seal clearance with the sealing flow rate was investigated.The effectiveness distributions based on mass and concentration were computed respectively,and the minimum sealing flow rate required to seal the system was determined from the computed effectiveness data.Pressure criterion was also used to estimate the minimum sealing flow rate for different rotational Reynolds numbers,and the results accord with previously published experimental correlation.
Experimental investigation on effect of small auxiliary holes on film cooling effectiveness
LIU Xiao-hong, TAO Zhi, LUO Xiang
2011, 26(12): 2710-2715.
Abstract PDF(945KB) icon2009 icon14
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Experimental study was conducted to investigate the effect of small auxiliary holes on the film cooling performance.The steady-state thermochromic liquid crystal (TLC) method was used to obtain the adiabatic effectiveness distributions on the flat surface.Measurements of adiabatic effectiveness were presented for cylindrical hole,fan-shaped hole,furcated hole and parallel hole with main flow Reynolds number at 2900,blowing ratio ranging from 0.3 to 3.0 and density ratio at 1.06.Results show that the film coverage and adiabatic effectiveness downstream of furcated hole and parallel hole are evidently superior to those of cylindrical hole at blowing ratios range from 0.3 to 3.0.While fan-shaped hole increases the adiabatic effectiveness compared with cylindrical hole only in cases of blowing ratios greater than 1.0.A higher blowing ratio means more obvious improvement of the adiabatic effectiveness.
Effects of injection fin on flow and mixing characteristics of cavity flame holder
JIN Jin-rui, LIU Yu-ying, HONG Yan
2011, 26(12): 2716-2721.
Abstract PDF(1165KB) icon1593 icon14
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Effects of injection fin in the supersonic cavity flame-holder were studied numerically.Both pressure loss and mixing enhancement effects were investigated.The results suggest that compared with the traditional structure,the cavity with injection fin induce less pressure loss,eularges penetration depth of the injections,and achieves a more appropriate fuel distribution.
Experiment on aerodynamic performance of turbine static cascade with high aerodynamic loading
YANG Qi-guo, WANG Xiang-feng, SHI Yu-wen, HAN Wan-jin
2011, 26(12): 2722-2730.
Abstract PDF(1231KB) icon1857 icon16
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In a low-speed ring cascade wind tunnel,aerodynamic tests were fulfilled on a large enthalpy drop static cascade in the middle stage of a steam turbine.From the front to the back gate,the flow parameters in seven cross sections along the blade height and pitch at three incidences were measured in detail with the application of five-hole pin ball test.The results show that,in order to meet the requirements of high loading conditions,the combination of highly variable loading and blade bending along span-wise can control the accumulation,transition and separation of boundary layer.Fore-loaded blade profiles were applied in the main passage area to ensure that the blade could withstand high loading.After-loaded blade profile was applied to the end wall and the positive bending blade further reduced aerodynamic loading,the end wall lateral pressure gradient was cut down to weaken the end wall lateral secondary flow.Positive and negative incidences affect only the static pressure distribution at the leading edge of the suction side or pressure side,causing the increase and decrease of aerodynamic loading.The turbine cascade with high aerodynamic loading has a good adaptability of incidence.
Effect of tip injection on the flow of near-stall condition in a transonic rotor
JIA Wei, LIU Huo-xing
2011, 26(12): 2731-2740.
Abstract PDF(1427KB) icon1551 icon12
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Effect of tip injection on the performance and the flow of near-stall condition of transonic axial compressor rotor was investigated numerically.The result shows that the stall margin of this transonic rotor gains an absolute improvement of 4.48% by tip injection while the efficiency remains unchanged at the injection angle of +65?.Furthermore,the separation on the suction side of the rotor and intensity of the tip leakage vortex are both weakened.Besides,the trajectory of the tip leakage is more inclined to the suction side of the blade which mainly leads to the increase of stall margin.
Effects of high-pressure guide vane adjustment on 1+1/2 counter-rotating turbine
LUO Wei-wei, ZHANG Lei, WANG Hui-she, XU Jian-zhong
2011, 26(12): 2741-2748.
Abstract PDF(1128KB) icon1852 icon18
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A detailed numerical simulation was carried out to investigate the 1+1/2 counter-rotating turbine performance with different openings of high-pressure guide vane and turbine expansion ratios.By analyzing the results,the variable high-pressure vane could effectively control the massflow of 1 1/2 counter-rotating turbine; when the high-pressure guide vane was opened,there was a peak turbine efficiency with the change of the expansion ratio,when the high-pressure guide vane was closed,the efficiency decreased steadily with the reduced expansion ratio,and the efficiency reduced more quickly than that when the high-pressure guide vane was opened; in the case of the lower expansion ratio,the efficiency improved with the increase of the opening of the high-pressure guide vane,and the improvement was more obvious with the decrease of expansion ratio,which is significantly different from the efficiency of conventional turbine that generally decreases in the variable guide vane; the results show that the opened high-pressure guide vane is favorable for the specific work ratio(SWR) of high-pressure turbine to that of low-pressure turbine remained within reasonable limits.
A technique to calibrate cavity effect in unsteady pressure probes with high frequency response
LI Ji-chao, WANG Si-chen, LIN Feng, NIE Chao-qun, Schoen M P
2011, 26(12): 2749-2756.
Abstract PDF(1112KB) icon1649 icon12
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A technique to calibrate cavity effects was introduced.By combining a simplified theoretical model with experimental verification,the modeling of the transfer function for the pressure probe was established.An ARMAX(autoregressive-moving average with exogenous input) model was used as the base structure of the cavity system and its parameters were identified from experimental data.It is demonstrated that despite its simplicity,this method can well capture the transfer function for the cavity based on the input/output signals,from which the relationship of the true signal and measuring signal can be obtained.This calibration technique is simple and practical,and can be of great value in many applications.
Dynamic changes rule of aero-engine turbine tip clearance in maneuver flight
JIA Bing-hui, ZHANG Xiao-dong, PENG Kai
2011, 26(12): 2757-2764.
Abstract PDF(1033KB) icon1886 icon22
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Based on the preliminary analysis of the change mechanism of the turbine blade tip clearance,the simplified model of blade,rotor and casing was established,and the effect of rotor vibration amplitude of aero craft in-flight maneuver state was researched.The results show:reduction of clearance is approximately 0.44 to 1.45 mm;local tip clearance would increase or decvease caused by uniformity acceleration of aero craft;pitching maneuver and horizontal circling would bring vibration of tip clearance,which makes the nonlinear of clearance variation markedly enhanced.
Numerical investigation on the effect of bowed blade to aerodynamic performance of low pressure turbine under stage condition
CHEN Lei, CHEN Jiang
2011, 26(12): 2765-2771.
Abstract PDF(1211KB) icon1627 icon11
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The numerical investigation on the effect of bowed blade to the aerodynamic performance of a two-stage low pressure turbine was presented.By analyzing the flow field of the bowed blade of different bowed-angle and bowed-type,the result is:under the stage circumstances,bowed blade design should match the real load condition;for target turbine,the first stage stator with positive bowed type and the second stage stator with negative bowed type have the best aerodynamic performance;compared to the symmetry bowed blade,J bowed type improves load distribution of the stage and reduces the secondary flow loss and shock wave loss;further more,the blade with small bowed-angle which has better pressure distribution and less entropy production of the mid-flow passage is superior to the big one.
Experiment of tip leakage flow characteristics in turbine shroud
YU Lei, CHANG Hai-ping
2011, 26(12): 2772-2776.
Abstract PDF(870KB) icon1702 icon12
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For rotor shrouded blade with cooling air,the total pressure loss coefficient of tip leakage flow in stationary state was investigated in different mainstream Reynolds numbers,outflow ratio of the former and the latter holes,tip clearance at so on.The results show:(1)total pressure loss coefficient increases as mainstream Reynolds number and outflow ratio of the former hole increase;(2)total pressure loss coefficient also increases by reducing tip clearance,which increases faster with the mainstream Reynolds number and outflow ratio especially in small tip clearance;(3)outflow ratio of the latter hole has litter impact on total pressure loss coefficient.
Strength analysis and structural optimization of detonation combustor to multi-cycle pulse detonation loading
ZHENG Long-xi, JIANG Hong-wei, YAN Chuan-jun, QIU Hua
2011, 26(12): 2777-2782.
Abstract PDF(883KB) icon1620 icon10
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The equivalent stress of the detonation combustor was computed and researched using the axisymmetric finite element modal and whole cycle pressure obtained by numerical simulation.The effect of the temperature was calculated using the measured thermal equilibrium temperature data,and the primary optimization of the thickness was completed for given fatigue life.It is found that the equivalent stress of the detonation combustor to multi-cycle detonation loading is a little bigger than that to single cycle detonation loading,and the difference of the same position is less than 4%.The equivalent stress of the detonation combustor at the same position is periodic when the PDE(pulse detonation engine) works circularly,and the maximal equivalent stress in every cycle is nearly equal.The maximal equivalent stress has an increscent trend along with the spread of detonation wave.The maximal equivalent stress at the same position is nearly equal when the frequency changes among 10~50Hz.The equivalent stress with temperature is nearly equal to that without temperature when it is assumed that the detonation combustor has the same temperature in the radial direction and can expand freely in the axial direction,but the equivalent strain increases.
Multiaxial fatigue life prediction method based on maximum damage critical plane
YANG Jun, LI Cheng-bin, XIE Shou-sheng
2011, 26(12): 2783-2790.
Abstract PDF(1092KB) icon2174 icon19
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Based on the critical plane method,a multiaxial damage parameter and a life prediction model were proposed.Differ from the traditional damage parameter whith takes the maximum shear strain range as the critical plane,this damage parameter,taking the maximum damage plane as the critical plane,integrates the maximum shear range with the normal strain range and the maximum normal stress on the maximum shear range plane and reflects the reduction fatigue life owing to the additional cyclic hardening with the non-proportional loading.It is convenient for engineering application because there is no material constants in this parameter and no need to consider the mean stress.Experimental verifications show that the proposed parameter gives better satisfactory results for three checked metals under proportional and non-proportional loading.The life prediction result of a turbine disk transmission arm pin hole using this parameter further proves the engineering applicability of taking the maximum damage plane as the critical plane.
Determination of preload force of circumferential distributed rod fastening rotor
LI Hui-guang, LIU Heng, YU Lie
2011, 26(12): 2791-2797.
Abstract PDF(1044KB) icon1575 icon22
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Three dimensional finite element stress analysis of circumferential distributed rod fastening rotor considering contact was performed.The evolution laws of stress distribution and interface contact status were revealed with different preload forces and operation conditions.The calculation results show that contact interface may separate locally and slide when the rod fastening rotor transmits power and lateral load,which results in its carrying capacity less than integral rotor.With the increase of preload force,rod fastening rotor can transmit greater load,but the maximum stress increases significantly and the strength margin of material decreases.According to the obtained stress level of rod fastening rotor and contact stress distribution and the ratio between tangential force and normal force of contact interface,the method for determining preload force of rod is given to ensure structural integrity and structural strength requirements.The analysis also provides references for preload force determination of such rod fastening rotor.
Contacting optimization in high pressure spool finite element parameters updating based on adaptive cloud PSO model
ZHANG Zi-yang, XIE Shou-sheng, WANG Hai-tao, LONG Men, MIAO Zhuo-guang
2011, 26(12): 2798-2804.
Abstract PDF(1081KB) icon1947 icon10
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A method to describe the complex contacting surfaces was propounded to update finite element(FE) model of high pressure spool in aero-engine.It was posed as the minimization of an error function defined in time domain.The minimization was performed by using a novel particle swarm optimization method based on adaptive cloud distributing model,which constituted the main contribution in this work.In this algorithm,when the solution was close to the minimum,the weights of particle distribution were at the top of the cloud model which can find the nearest minima accurately,and when this algorithm tended to be unstable,the weights were at the bottom of the cloud model,which lowered the chance to relapse into local optimization in the process of solution convergence.The method has been tested through a simulated function model and FE model of high pressure spool.The performance of the proposed adaptive algorithm is more effective than those of other related algorithm with which it is compared.
Study of the instability characteristic in the boundary layer of a hypersonic blunt cone at low angle of attack
YUAN Xiang-jiang, LI Guo-liang, LIU Zhi-yong, TU Guo-hua
2011, 26(12): 2805-2811.
Abstract PDF(1236KB) icon1930 icon14
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DNS(direct numerical simulation) and LST(linear stability theory) were employed as tools to study the characteristics of instabilities and transitions in hypersonic boundary layers.The characteristics for flow past a blunt cone in Mach 6 free-stream with 5 half-angle at 2 degree angle of attack (AOA) were analyzed.The results show that there are multi branch instability modes.The instabilities of the blunt cone with the crossflow generated due to AOA is essential different from the cases without the crossflow.The crook in the transition front near the leeward line arises from a transformation between the instability modes.
Airship shape optimization with NURBS and gradient based algorithms
GUO Xue-yan, ZHANG Hai-jun, DAI Ren
2011, 26(12): 2812-2819.
Abstract PDF(1079KB) icon1683 icon16
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The present work attempts to conduct shape optimization of stratospheric airships with a method based on a combination of NURBS (non-uniform rational B-spline) and a gradient-based optimization algorithm.Drag coefficient was chosen as the objective function and airship volume as the constraint.NURBS based geometric parameterization was used because of its more efficient representation of the discrete geometric data than other methods (e .g. B?zier curve).Drag coefficient was obtained during the optimization iteration by solving two dimensional incompressible viscous flow field.Both form and viscous drags were considered when drag coefficient was calculated.Using LOTTE airship shape as initial shape,an improved shape with the above algorithm was obtained.Airship with the new shape obviously had better aerodynamic performance.It is eventually proved that the optimization method above can be effectively applied to airship optimization.
Numerical simulation and comparison of aerodynamic characteristics between ducted and isolated propellers
XU He-yong, YE Zheng-yin
2011, 26(12): 2820-2825.
Abstract PDF(1176KB) icon2276 icon77
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The complicated flows around the ducted and isolated propellers were numerically simulated by solving the unsteady Euler equations based on unstructured dynamic overset grids,and the aerodynamic characteristics between them were compared.For the effective treatment of the complicated flow field involving relative motion between the propeller and duct,the computational domain was decomposed into two subzones,namely,rotational subzone and stationary subzone.The rotational subzone contained the propeller and the stationary subzone contained the duct.The good agreement between the present calculation result and experimental data demonstrates that the present method has good accuracy to simulate ducted-propeller problems.The lower-pressure area at the leading duct leads to the generation of additional thrust on the duct.Compared to the isolated propeller,the existence of duct changes the flow characteristic around the blade tip,and decreases the tip-loss.For the same rotational speed of the propeller,the ducted-propeller can generate greater thrust with less power,resulting in the conclusion that the ducted-propeller system has a better aerodynamic efficiency.
Analysis of geometric parameters influence on pressure swirl injector performance based on VOF interface tracking method
LIU Juan, SUN Ming-bo, LI Qing-lian, WANG Zhen-guo
2011, 26(12): 2826-2833.
Abstract PDF(1074KB) icon2083 icon31
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Interface tracking method volume of fluid (VOF) was used to simulate the flow process in pressure-swirl injector.Three target values including discharge coefficient,film thickness and spray cone angle were obtained after validating the reliability of numerical method.Non-dimensional influence factor η was defined to evaluate the influence of the 15 geometry parameters.The focus is on the geometry parameters which have not been researched much before,such as divergent angle,the length of swirl chamber and so on.The extention of the length of swirl chamber increases spray cone angle.Divergent angle at the injector exit decreases sheet thickness and increases cone angle remarkably.Increasing the distance between the injector and the top wall enhances injector performance.The number of tangent inlet and the length of central post dont not have much to do with the injector performance.What have been done in this paper helps to optimize the injector geometry.
Simulation of pressure shock during start and shutdown operation of rocket tank pressurization system
WANG Chong, GUO Yuan-yuan, LIANG Guo-zhu
2011, 26(12): 2834-2840.
Abstract PDF(916KB) icon1902 icon12
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For the purpose of researching into the engendering and diffusing of the pressure shock during the starting and the shutting of the rocket tank pressurization system,one-dimensional nonsteady finite difference equations under the Lagrange reference frame were built to simulate the gas flow in the pipes,and ordinary differential equations were calculated numerically based on the dynamic processes of the components,while the frictional loss was computed with a quasi-steady formula.The B-B(Beattie-Bridgeman) function was used to simulate the real-gas effect.The results were presented for the unsteady processes of a representative pressurization system,including the pressure shock that appeared during the starting and shutting operation.It is shown that the pressure shock during the starting changes with large amplitude and the pressure oscillation have shorter period,higher frequency,and rapidly cause of attenuation,while the pressure shock and oscillation changes reversely during the shutting operation.During both the operations,the pressure peak appeared was higher than the pressure in the bottle.The mathematical model and calculating method are validated to be effective in the calculation of the dynamic process of the rocket tank pressurization system.
Fault diagnosis method for aero-engine based on SVM with large-scale training set
XU Qi-hua, GENG Shuai, SHI Jun
2011, 26(12): 2841-2848.
Abstract PDF(866KB) icon1840 icon19
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A learning strategy was presented to solve the large-scale support vector machines (SVM) training problem of aero-engine fault diagnosis.According to the strategy,only those samples were retained for final training,which were near the support vector hyperplane of the original small-scale SVM classifier or classified mistakenly by the original classifier.The final pruning set was reduced evidently and the training time was shortened obviously on the condition of high classification accuracy.Meanwhile,the classification time was shortened correspondingly because of the decrease of the support vector number.Something about the parameter selection of the sequential minimal optimization (SMO) method and how to use this potential algorithm in aero-engine fault diagnosis were also discussed.Simulation examples show that this fault diagnosis method proposed for aero-engine,based on SVM with large-scale training set,is effective,reliable and easy to be implemented for engineering application.

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