2013 Vol. 28, No. 6

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Incremental particle filter method
FU Hui-min, LOU Tai-shan, WU Yun-zhang
2013, 28(6): 1201-1207.
Abstract PDF(464KB) icon1673 icon996
Abstract:
An incremental particle filter(IPF)model and analysis method were put forward, while the concept and recursive calculative steps were established. For the measurement data with unknown system errors in practical engineering, accurate measurement model cannot be established. The presented IPF method established accurate measurement likelihood function by calibrating the unknown system errors in the measurement data, and accurate incremental particle filter model was obtained. This can eliminate these unknown system errors, decrease the number of resampling, effectively preserve the diversity of particles and improve the accuracy of nonlinear filtering. In simulation, the number of resampling decreased by 41.7 percentages, and filtering error mean value and RMSE (root mean square error) decreased by 45.3 percentages and 70.1 percentages, respectively, improving the performance of filtering effectively.
Method for notched fatigue life prediction with stress gradient
WANG Yan-rong, LI Hong-xin, YUAN Shan-hu, WEI Da-sheng, SHI Liang
2013, 28(6): 1208-1214.
Abstract PDF(583KB) icon2226 icon1865
Abstract:
A method for fatigue life prediction of notched specimen or real component when taking the effects of mean stress,stress gradient and dimensional size into consideration was developed based on the distribution of dimensionless stress at notch root of the specimen.The factors for stress gradient and dimensional size were calculated and the fatigue life was predicted for two types of notches machined with TC4 alloy.The results show that mean stress at notch root and the factors for stress gradient and dimensional size could reflect the effects of notch on the fatigue life.Predictions based on the developed approach give estimates falling within 2-fold scatter.
Experiment on rotor dynamics of rotor system with air film damper
MA Yan-hong, WANG Hong, HONG Jie
2013, 28(6): 1215-1222.
Abstract PDF(1517KB) icon1788 icon996
Abstract:
An air film damper (AFD) with metal rubber as the outer ring was presented,which was designed as the assistant support and damping component for rotor systems.The mechanical model of AFD was established and the mechanism of AFD was explained.A rotor system with AFD and the testing rig were constructed in order to verify the performances of AFD as an assistant support and damping component comparing with a rotor system without AFD.Based on the measurements of the displacements and the phrases of AFD,the tracking vibration response process of the air film ring was captured.Comparing the phrases of the air film ring with the journal,the mechanism and damping properties of AFD was testified.Moreover,the effects of the original air film clearance on the properties of AFD were studied.The results show that due to the moveable metal rubber ring,the air film ring can adjust the displacement and phrase with the vibration of the journal automatically,which presents an automatic adaptability of AFD.Combining the stiffness and damping of the metal rubber ring and the air film,AFD,being an assistant support and damping component,can provide additional support stiffness and effective damping to the rotor system,which can reduce the vibration of the rotor system.Furthermore,a smaller original air film clearance would result in a more additional stiffness and better damping effect.
Typical fatigue life analysis approaches for notched components
ZHANG Cheng-cheng, YAO Wei-xing
2013, 28(6): 1223-1230.
Abstract PDF(571KB) icon2150 icon1138
Abstract:
Some commonly used fatigue life analysis approaches for notched components were systemically reviewed.According to different descriptions of the notch effect,the fatigue life analysis approaches for notched component were classified into three categories,namely,local stress-strain approaches,stress gradient approaches and critical zone approaches.The capability of each approach was discussed and experimentally checked by four groups of LCF(low cycle fatigue) test data of LY12CZ aluminum alloy under different notch geometry.It's found that the predictions with regard to stress gradient and distribution of stress field (e.g. critical zone approach and stress gradient approach) show a good agreement with test data as well as the stress field intensity approach can predict the correct failure location, while the local stress-strain approach showes poor fitness and low accuracy.
Compressive strength prediction of CCF300/QY8911 unidirectional fiber reinforced composites
ZHANG Yong-bo, FU Hui-min, WANG Zhi-hua
2013, 28(6): 1231-1235.
Abstract PDF(344KB) icon2109 icon1071
Abstract:
A method for the compressive strength prediction of unidirectional fiber reinforced composite was proposed. Based on the fiber microbuckling mechanism and fiber kinking mechanism, an investigation on the compressive strength prediction of CCF300/QY8911 unidirectional fiber reinforced composites was made. Combining the fiber microbuckling mechanism and fiber kinking mechanism together, which were both responsible for the failure, a combined model for compressive strength prediction of the unidirectional CCF300/QY8911 composite was proposed. According to the compression between the predicted results and measured date, it shows that to compare with the microbuckling model and the kinking model, the combined model makes a better agreement that keep the difference less than 5%.
Fatigue life prediction of turbine disk based on stress gradient
SHI Liang, WEI Da-sheng, WANG Yan-rong
2013, 28(6): 1236-1242.
Abstract PDF(592KB) icon1754 icon1129
Abstract:
The effects of stress gradient and dimensional size on fatigue life were investigated.The relationship between the notched specimen and the smooth specimen was correlated by introducing the stress gradient effect factor,and a new model of predicting notched specimen based on the Walker modification for the mean stress effect was established.Three-dimensional elastic finite element (FE) analysis of a turbine disk was carried out to obtain the fatigue parameters for predicting its life.The result shows that this model can well reflect several effects on fatigue life,especially the effect of stress concentration on the fatigue life of specimen.If the mean stress,stress gradient and size effect are considered comprehensively,the prediction result of the disk is closer to the experiment result.This model gives a prediction falling within a scatter of two for both GH901 standard specimen and the disk.
Meso-scale modeling of 3-D four-directional braided composites
FENG Wei, WANG Yan-rong, WEI Da-sheng
2013, 28(6): 1243-1249.
Abstract PDF(704KB) icon1805 icon1074
Abstract:
Based on the motion of yarn carriers on the braiding machine bed, the spatial configuration of interior yarns was analyzed in detail, and a meso-scale model of 4-step three-dimensional (3-D) braided composites was established. In this model, the cross-section deformation, the contact of fiber bundle and the bended centerline due to the mutual squeezing in the braiding process were taken into account. In addition, the structural geometry of the composites was analyzed and the mathematical relationship between the braided parameters and the structure of the unit cell was obtained. The results show that the hypotheses that axis of fiber bundle is curve inside the composites and the section of fiber bundle is oval at control points are close to the real structure and good agreement can be obtained between the calculated and measured values of the geometric characteristics of braided composite samples. The predicted value of unit cell height show that the maximum error remained at about 3%, in addition, when the braided angle is 19°, 21° and 21.5°, the prediction results are more close to the measured results. It is suitable for modeling of 3-D braided composites, especially the structure of small braided angle. Therefore, the model presents a foundation for the mechanical properties prediction of the composites.
Modeling and optimization for the structure of biaxial symmetry non-circular hole of turbine disk
CHEN Qiu-ren, GUO Hai-ding, LIU Xiao-gang
2013, 28(6): 1250-1256.
Abstract PDF(565KB) icon1935 icon1014
Abstract:
In order to resolve the stress concentration of the holes on engine disks,a geometry model of turbine disk non-circular hole was established and applied to a turbine disk flange.The contour of this model consisted of eight biaxial symmetry arcs to ensure smooth connection and bolts assemblage.The geometry of turbine disk hole was improved and optimized with the non-circular hole,using the maximum first principal stress as objective function.The optimization results show that the maximum first principal stress on the non-circular bolt hole inner surface is reduced by 14.8% along with remarkable drop of the stress concentration.The results of design variables' sensitivity show that the sizes of transition arcs connected with main arcs have significant influence on hole edge stress concentration.
Calculation of needled C/SiC composite elastic parameters in consideration of the porosity
LI Long, GAO Xi-guang, SHI Jian, SONG Ying-dong
2013, 28(6): 1257-1263.
Abstract PDF(681KB) icon1931 icon1082
Abstract:
Based upon the microphotographs of the needled ceramic matrix composites(CMCs),appropriate representative volume elements(RVE) were selected to establish a single-cell model for predicting the elastic properties of needled ceramic matrix composites.The effect of porosities on the elastic properties of matrix and fiber bundles was considered,and the elastic constants of fiber bundles were calculated by mixed rate,then elastic constants of fiber bundles and matrix were taken into the single-cell model.The elastic properties of needled ceramic matrix composites were calculated by the finite element method(FEM) at last.At the same time,the tests for tensile strength and determination of porosities were carried.Through the experiment,the materials' open porosity of 7.33% and closed-cell porosity of 10.67% were acquired.Numerical results of the elastic properties obtained by the proposed method agree well with the experimental results,and the error is 3.1%.
Using the mode match method liner design and experimental validate in the uniformity axis flow
WANG Tong-qing, LIANG Dong
2013, 28(6): 1264-1269.
Abstract PDF(648KB) icon1609 icon1254
Abstract:
The mode match method has been used for the liner design and optimization of the low speed fan facility. The experimental results and the trend of the calculation results are identical with each other. 2 liners both has significant effect for the +4 order mode of 2 blade passing frequency (BPF). The first forward liner's insert loss is 30.4dB, and the backward liner's insert loss is 20.25dB; the second forward liner's insert loss is 21.85dB, and the backward liner's insert loss is 18.85dB. It's proves that, mode match method can be used in the liner design and optimization, and the experimental platform for the nacelle design was gotten. The cost of liner design for the aero engine nacelle can be reduced.
Integrated design and performance analysis of waveriderforebody and inlet
HE Xu-zhao, QIN Si, ZHOU Zheng, NI Hong-li
2013, 28(6): 1270-1276.
Abstract PDF(657KB) icon2163 icon1085
Abstract:
The basic inward turning cone was designed by methods of characteristics which were represented by straight initial shock wave and inner compression section shock wave cancelation, controllable flow parameters and uniformity exit inner compression section. The integrated osculating inward turning cone waverider inlet(OICWI) design methods were developed based on the osculating inward turning cone (OIC) waverider design methods. Based on the designed basic inward turning cone flow field and OICWI design methods, an OICWI was designed. The OICW's performances were analyzed by numerical ways. The results show that:(1)The integrated waverider inlet design methods agree well with aerodynamic principles. (2)The waverider-inlet's shape can be easily controlled by adjusting inlet capture curve, front capture curve and basic flow field structure. (3)Numerical simulation results agree well with the design results and the flow field structures are consistent with each other, showing that the integrated design methods are correct. (4)The viscous results on design and off-design conditions show that OICWI has high pressure recovery and flow capture characteristics, and the flow field parameters are uniform in the inlet exit plane.
Model optimization method and connected-pipe experiment of a liquid fuel ramjet engine
MA Qian-rong, GUO Xin, WU Hu, CHOU Qian
2013, 28(6): 1277-1285.
Abstract PDF(600KB) icon1622 icon1087
Abstract:
The optimization method of a mathematical model and connected-pipe experimental technique for a test in altitude test facility (ATF) of a liquid fuel ramjet engine was researched.The optimization of the simple mathematical model was divided into two steps.Firstly,using the test engine's geometry configuration size data,a preliminary adjustment was done.Secondly,using experimental test data,the components' experiential coefficients were modified appropriately.Emphasis was laid on the simulation technique of flight condition and parameters measurement method.The experimental technique was applied to a ramjet ATF test successfully.The comparison results show that the optimized-model has higher precision and the nozzle gross thrust difference drops from 12% to about 4%.
Aero-engine ground starting performance at non-standard atmosphere
GUO Hai-hong, PAN Xu, ZHANG Zhi-shu
2013, 28(6): 1286-1290.
Abstract PDF(335KB) icon1670 icon1081
Abstract:
In order to gain the influences of the atmosphere condition on aero-engine starting characteristics, the output power of air turbine starter and ideal starting process at standard atmosphere were analyzed, and the diversities of ground starting performance at non-standard atmosphere were described, e.g.: differences of ignition time, start time and exhaust gas temperature. Besides, with use of constant acceleration method, the starting process was simulated. Based on grounding test conditions, test data was summarized. The ignition and breaking-up time was prolonged with the temperature drop or rise. Comparing the start time below or above 293.15K,it is 3s shorter in hot days than in cold days, so the results meet the theory analysis well.
Internal contraction tunnel design of two-dimensional hypersonic inlet
LI Hang, LI Bo
2013, 28(6): 1291-1297.
Abstract PDF(735KB) icon1680 icon1015
Abstract:
The curved surface of internal contraction tunnel of two-dimensional hypersonic inlet was designed and investigated.Based on hypersonic inlet with the same internal contraction area ratio and throat area,the influences of the length of internal contraction tunnel and the tension of the shoulder spline on the inlet performance were studied numerically.Results indicate that the length of internal contraction tunnel has great effect on the total pressure recovery coefficient and the starting-up Mach number.When the length to throat height ratio is 8.4,the total pressure recovery coefficient is better.Spline with suitable tension to replace the traditional surface with radii at shoulder can increase the total pressure recovery coefficient.With the increase of the length of internal contraction tunnel,the corresponding optimal tension of spline will decrease.The recommended range of spline tension is 0.80-1.25.
Inlet distortion’s effects on stability and performance of turbofan engine
ZHAO Yun-sheng, HU Jun, TU Bao-feng, LI Liang, LUO Ju
2013, 28(6): 1298-1304.
Abstract PDF(765KB) icon2157 icon1209
Abstract:
For assessing the inlet distortion's effects on the stability and performance of turbofan engine,a two-dimensional method was developed.The unsteady two-dimensional inviscid integral Euler's equations were used;units were divided along the axial and circumferential directions and solved by time-matching.Simulations of a two spool mixed flow turbofan engine show that this method would obtain the distortion transfer curves along the flow path,which can assess the attenuation of components such as fan or high pressure compressor for distortion.Capabilities to resist the total pressure and total temperature distortion were analyzed for typical operating points in the flight envelope,and the most dangerous point was confirmed;under the given total pressure distortion condition, the turbofan engine's thrust decreases and the specific oil consumption increases, and the maximum amounts of change are 10.5% and 11.7% respectively.
Critical area method for mass flow matching of dual-mode scramjet
HUANG Xing, CHEN Yu-chun, LI Jie, WANG Xiao-dong, CAI Yuan-hu
2013, 28(6): 1305-1312.
Abstract PDF(881KB) icon2483 icon943
Abstract:
The lumped parameter model for thermo-throat (Ma=1.0) simulation was established based on 0-D conservation equations(continuity equation,momentum conservation equation and energy conservation equation) of the control volume,including:wall friction model,fuel injection model,fuel atomization and mixing model,and chemical kinetics model.To solve the problems in simulating the thermo-throat with lumped parameter model,a critical area method based on mass flow balance was proposed to simulate the 1-D flow field of the combustor.With this method,the mass flow balance between isolator and combustor in different modes when a dual-mode scramjet worked in thermo-throat condition was achieved,and the thermo-throat was accurately captured;in addition,the isolator flow state,the combustor operation modes and the flow path parameters were determined.The results show that the lumped parameter computation model with the critical area method can solve the problems in thermo-throat simulation,its computing accuracy reaches 10-4,and the computing time at every working condition is less than 0.1s.
Parameters analysis of adaptive pressure relief slot in hypersonic inlet
LIU Yuan, JIN Zhi-guang, ZHANG Kun-yuan, NAN Xiang-jun
2013, 28(6): 1313-1321.
Abstract PDF(1430KB) icon1748 icon1082
Abstract:
In order to improve self-starting performance of the fixed-geometry inlet at low Mach number,a technology of self-adaptive pressure relief slot was proposed.The law about the location,direction and effective area of single adapted pressure relief slot was studied with a high performance two-dimensional hypersonic inlet utilizing the technology of numerical simulation.The result shows that:the slot has little influence on the model inlet,and the total pressure recovery ranges around 2%;the slot located downstream the cowl shock wave has large outgassing rate,which will increase as the angle descends and the effective area ascends.The outgassing rate of the adapted pressure relief slot is just 50% compared with normal slot under the same condition.It will drop as the Mach number increases,approaching self-close state at high Mach number condition.
Aerodynamic design method of high loaded supersonic axial-compressor with low reaction
WANG Song-tao, HU Ying-jiao, WANG Zhong-qi
2013, 28(6): 1322-1332.
Abstract PDF(1257KB) icon1871 icon949
Abstract:
For supersonic axial flow compressors, a brief summary was given for its historical development. The internal flow characteristics and problems of the two kinds of traditional supersonic compressors were analyzed. Some prospects were proposed for its future technology trends and research orientation. According to the flow characteristics in supersonic compressors, a new aerodynamic design method of high loaded supersonic axial-compressor with low reaction was put forward. Using this method, active flow control means are not necessary in the efficient rotor, and the exit absolute Mach number of the rotor is decreased. For the downstream stator, boundary layer suction is used to solve its internal flow problems to fulfill an efficient and high loaded stage design.A preliminary design verification of the principle has been conducted.The 3-D viscous numerical simulation results show that at the tip tangential speed of 360m/s,the stage pressure ratio of 2.3 and the isentropic efficiency of 86.5% are achieved in the use of this concept.
Further validation of NHM in two-stage counter-rotating compressor
LIU Bo, WANG Lei, HUANG Jian
2013, 28(6): 1333-1341.
Abstract PDF(1010KB) icon1620 icon969
Abstract:
The nonlinear harmonic method (NHM) has been used to examine and analyze the unsteady rotor-rotor interaction of the two-stage counter-rotating compressor.To validate the NHM simulation results,the predicted characteristics of aerodynamic parameters were compared with the measured data and rigorous full-annulus unsteady simulations at typical working conditions.Based on the NHM deterministic stresses have been post-processed to compare to the full-annulus simulation to analyze distinct sources of unsteadiness.The NHM deliver accurate results at design points compared to full annulus results.The limits of the NHM are reached as soon as rotating stall effects occur as the theory foundation of the NHM,Fourier transformation,is no longer valid.
Parameters design and 3-D modeling of small flow rate high-speed centrifugal impeller
GAO Li-min, XIE Jian, ZHU Qi-peng, MIAO Fang
2013, 28(6): 1342-1349.
Abstract PDF(1038KB) icon2690 icon1326
Abstract:
Approaches about preliminary parameters deign and 3-D modeling of high-speed small flow rate centrifugal compressor were presented,and corresponding FORTRAN code was developed.In order to verify the feasibility of the approaches,an impeller based on Krain's impeller was modeled with its camber line optimized by curvature control.The blade of the impeller was matched with S-shaped blade of good aerodynamic performance.After analysis of CFD results,the redesigned impeller achieved isentropic efficiency of 93.9% and total pressure ratio of 4.794 on design mass flow rate,and the error was 0.24% and 2.14% respectively compared with Krain's impeller.Results show that the approaches and the code are valid for rapid impeller design.
Effect of tip leakage flow and wake interactions on off-design point performance of tandem rotors
QIAN Yu-ping, LI Qiu-shi, LU Ya-jun
2013, 28(6): 1350-1356.
Abstract PDF(761KB) icon1596 icon907
Abstract:
Interactions of tip leakage flow and wake in tandem rotors were researched based on the changes of the circumferential position of back rotor in relation to the front rotor.An analysis flow model was established for studying the effect of above flow interactions.The model results indicate the mixing of tip leakage flow and wake can reduce the blockage greatly.3-D numerical simulations were further carried out in high loading tandem rotors with three typical circumferential arrangments and the model results were verified by the numerical results.According to the research,the mixing of back rotor tip leakage flow and front rotor wake can reduce tip blockage almost by 20% compared with non-mixing case and the stall margin of the tandem rotors increases by 11.7% relatively.
Numerical simulation of liquid film and regenerative cooling in a rocket combustor
SUN Bing, YANG Wei, ZHENG Li-ming
2013, 28(6): 1357-1363.
Abstract PDF(604KB) icon1912 icon1036
Abstract:
Numerical calculation was made for liquid film and regenerative cooling in a liquid rocket combustor.Multiple species axial Navier-Stocks(N-S) equations were solved for liquid-film/hot-gas flow field,single specie axial N-S equations were solved for regenerative flow field and k-ε equations for turbulent flow.A kerosene/LOx rocket combustor was simulated,and the results of the model agreed well with the results in reference.The results show that:(1) Liquid film and regenerative cooling decrease the wall flux and wall temperature effectively,and the cold area covers the whole combustor and nozzle wall.(2) The cooling effect becomes better with the increase of the regenerative coolant. (3) The temperature rise of the regenerative coolant is between 450~600K,and becomes smaller when the mass flow rate of the regenerative coolant is larger.(4) The mass fraction of kerosene on the inner wall decreases along the axis and reaches the lowest value at the outlet,but the area containing kerosene becomes larger.
Experimental demonstration and one-dimensional model analysis of supersonic magnetohydrodynamic acceleration
ZHANG Bai-ling, CHEN Feng, LI Yi-wen, ZHU Tao, ZHANG Yang
2013, 28(6): 1364-1371.
Abstract PDF(782KB) icon1926 icon939
Abstract:
In order to investigate the influence of load factor and conductivity on the performance of supersonic magnetohydrodynamic (MHD) accelerator.The experiments under the conditions of a magnetic field of 0.5 T and different voltages applied to capacitors were carried out,which used shock tunnel drive MHD accelerator,took Ar and potassium carbonate as the working fluid and capacitors as the power sources.And a one-dimensional steady ideal segmented Faraday type MHD accelerator model was analyzed.The voltages across electrodes, currents,load factors and conductivities at #10 electrodes,and open-circuit voltage at #20 electrodes were acquired from the experiments.The MHD flow velocity was increased by 11.4% and 24.0% respectively with capacitors charging voltages of 300 V and 400 V,while the velocity decreased by 11.1% with the voltage of 500 V.Experiments and model analysis show the different load factors would make the supersonic MHD flow into different modes,the conductivity influences the magnitude of the energy deposition,would make the velocity gradient of the magnetic fluid change.
Numerical simulation of characteristics of ion thruster plume
REN Jun-xue, GU Zuo, GUO Ning, QIU Qian, TANG Hai-bin
2013, 28(6): 1372-1379.
Abstract PDF(801KB) icon1719 icon1068
Abstract:
The back flow of charge-exchange (CEX) ions in the ion thruster plume affects normal operation of the satellite.The ion thruster plume model was established and a numerical simulation using particle-in-cell (PIC) method was adopted to obtain CEX ions distribution in the plume.The simulation results agree well with the flight measurement results of deep space one spacecraft.Influential factors to the distribution characteristic of CEX ions surrounding the spacecraft were analyzed,including:spacecraft potential,electron temperature,thruster operation parameter and size of spacecraft.It shows that CEX ion density surrounding the spacecraft varies from 108m-3 to 1012m-3.The CEX ion density in the measurement point varies from 0.65×1012m-3 to 1.5×1012m-3 when the spacecraft potential varies from -15V to 27V.The distribution of CEX ion density and electrical potential structure varies slightly with the electronic temperature.However,the magnitude of the electrical potential is proportional to the electronic temperature.The CEX ion density at different thruster operation points can be induced accurately according to the relationship between the CEX ion generation rate and the thruster's operation parameter.The surface of the spacecraft onto which the thruster is installed in fact shields the backflow of CEX ions.
Orthogonal optimization design for a hydrogen-rich/oxygen-rich shear tricoaxial gas-gas injector
JIANG Jin-peng, JIN Ping, CAI Guo-biao, WANG Jue
2013, 28(6): 1380-1386.
Abstract PDF(592KB) icon1773 icon902
Abstract:
To study the influence of the design parameters of a hydrogen-rich/oxygen-rich shear tricoaxial gas-gas injector on the combustion performance and the heat load performance, the parameters were fitted combination through the orthogonal experiment design method. The flow field of the single injector combustor was simulated. Evaluation indexes were the combustion length, the average gas temperature on combustion chamber wall and the average gas temperature on the injection faceplate. The results show that the fuel velocity to the oxidizer velocity has the most remarkable influence on the combustion performance and the heat load performance, the percentage of the central fuel mass flow rate has very obvious impact on the heat load performance, and the ratio of the oxidizer pressure drop to the combustor pressure has notable influence on the faceplate temperature, while the oxidizer post tip wall thickness has insignificant influence on the performance of the injector. To some extent, the interaction between the velocity ratio and oxidizer pressure drop affects the performance of the injector, while other interactions of the design parameters have little influence. The shortest combustion length i s 117.9mm. The lowest wall temperature is 1637.7K, and faceplate temperature is 806.6K.
Experiment on outlet temperature field of a gas turbine combustor
LIU Kai, ZHANG Bao-cheng, MA Hong-an
2013, 28(6): 1387-1391.
Abstract PDF(559KB) icon1634 icon884
Abstract:
The influence of aperture ratio and center distance of a gas turbine combustor mixing system on outlet temperature field was studied experimentally.Experimental results indicate:the outlet temperature distribution coefficient reduces gradually with the increase of aperture ratio.But too large aperture ratio will lead to partial obstruction and also hot spot temperature rise;aperture ratio does not change the radial temperature distribution curve shape,but only bring about shift of its position.Relative center distance and the radial temperature distribution coefficient have a strong correlation,too large (more than 0.33) or too small (less than 0.29) is not helpful for dilution.Relative center distance of 0.31 and aperture ratio of 0.32 are basically reasonable in this case.
Flame-holding mechanism of cavity structure in super-sonic combustor
JIA Zhen
2013, 28(6): 1392-1401.
Abstract PDF(1452KB) icon1564 icon893
Abstract:
The influences of length to depth ratio of cavity as well as its depth on the mixing effect of fuel and air and the combustion efficiency in supersonic flow field with/without reactions were numerically investigated. It is found that although increasing length to depth ratio could bring about fuel entrainment into cavity, delay the mixing time in low speed high-temperature recirculation zone and enhance the mixing and combustion efficiency. Yet, excessive length to depth ratio no longer improves combustion, but enhances the attached shock, increasing total pressure loss and drag between front and back walls. Increasing depth of cavity produces more loss of available energy induced by shock wave, but increases mass exchange rate between mainstream and cavity, enlarging cavity volume remarkably and increasing combustion efficiency.
Experimental investigation and numerical analysis of windage heating in rotating labyrinth seals
WANG Peng-fei, GUO Wen, ZHANG Jing-zhou
2013, 28(6): 1402-1408.
Abstract PDF(832KB) icon1890 icon928
Abstract:
Experiments were conducted to investigate the windage heating characteristics in real size models of stepped labyrinth seals.The change in total temperature across the labyrinth seal was measured in a high speed test facility at different pressure ratios (1.05-2.8),relative sealing clearances(2.4-4.0),Reynolds numbers(1900-28000) and rotational speeds (0-12000r/min).Based on the experiments,the renormalization group (RNG) k-ε turbulence model was used to compute the windage heating characteristics of the same stepped labyrinth seals.The results indicate that the temperature rise decreases with the increases of pressure ratio,Reynolds number and relative sealing clearance,and it increases with the increase of rotational speed.In addition,the numerical simulation satisfies the experiment.The most of the windage heating takes place in the first half of the seals,and the value of temperature rise is about 60% in the first two tooth chambers.An empirical expression for the windage heating coefficient was obtained and it fits the experimental results well.
Effects on calibration and use of thermochromic liquid crystal
ZHAO Xi, XU Guo-qiang, LUO Xiang, FENG Ye, WANG Lei
2013, 28(6): 1409-1414.
Abstract PDF(600KB) icon1374 icon948
Abstract:
Based on comprehensive analysis of thermochromic liquid crystal measurement methods, insight into the main influential factors to any general calibration was provided.The relative position of the strobe and camera and the distance of these two devices to the shooting window were kept,and the temperature difference from the shooting modes with and without shooting window,the thickness of plexiglass shooting window,the differences between cooling or heating cycles (hysteresis) and the number of heating or cooling cycles (aging) are up to 0.5℃,0.2℃,0.26℃ and 1.2℃, respectively;the sealing gap of rotor-stator disc does not affect the performance of the thermochromic liquid crystal;the relationship of temperature and hue depends on the light-emitting medium.
Single-neuron PID control arithmetic with integral restriction function
QU Tao, HAO Bin-bin
2013, 28(6): 1415-1419.
Abstract PDF(409KB) icon1710 icon833
Abstract:
A variable parameter quadratic performance seeking PID(proportion integration differentiation) control algorithm capable of anti-integral windup was presented. In addition to structural simplicity of PID, the algorithm features self-adaptive adjustment ability of neuron and quadratic performance seeking characteristics; the integration of error could be reduced automatically by control logic in the occurrence of integral windup, thus improving robustness and adaptability of variable parameter PID algorithm. The nozzle of a two-spool turbofan engine was taken as a controlled object, control performance simulation was conducted with model parameters varying within 50% range. The results show that variable parameter quadratic performance seeking PID control algorithm features relatively high stability and robustness, the maximum overshoot of dynamic process is reduced within 5%, the settling time is only 0.6s. Simulation results show that the presented performance seeking PID control arithmetic can satisfy the requirement of aero-engine control.
Multi-step predictive control for aero-engine distributed control system based on RVM regression error compensation
WANG Lei, XIE Shou-sheng, MIAO Zhuo-guang, REN Li-tong, YU Jian
2013, 28(6): 1420-1428.
Abstract PDF(700KB) icon1619 icon845
Abstract:
A multi-step predictive control method based on relevance vector machine(RVM) regression error compensation was put forward to control aero-engine distributed control system(DCS) with stochastic and bounded time-delay.The neural network nonlinear auto regressive moving average(NARMA) model of the aero-engine DCS was established to predict the future output.An improved multi-step prognostic algorithm based on RVM regression was presented to estimate prognostic error series which were compensated for the NARMA model.Finally,a neural network inverse controller was designed,and rolling optimization of the parameters was conducted by prognostic output and the expectations.Simulation results illustrate the control strategy avoids the effect of stochastic and bounded time-delay on the control system.The controller has favorable dynamic tracking and robust performance.The absolute steady error of low-pressure rotor speed step response is less than 0.04%,and the response time is less than 0.3 s.
Fault detection of aero-engine non-linear distributed control system based on T-S fuzzy model
ZHAI Xu-sheng, XIE Shou-sheng, MIAO Zhuo-guang, PENG Jing-bo, ZHANG Zi-yang, WANG Lei
2013, 28(6): 1429-1435.
Abstract PDF(501KB) icon1685 icon1030
Abstract:
The problem of fault detection for aero-engine no-liner distributed control system was studied.Firstly,a new non-linear modeling method for aero-engine based on Takagi-Sugeno(T-S) fuzzy model and flight envelop division was proposed,and the model of the distributed control system with network derivational time-delay was established by using this method.Secondly,if the distributed control system was regarded as a discrete switch system,a fault detection observer with time-delay compensation was designed,and the sufficient conditions of asymptotically stability for the observer-based residual system were presented.The total simulation took 20 seconds, a step fault with 0.0025 amplitude happened at the 12th second, the simulation results show that: the fault observer was asymptotic stable for preceding 12 seconds, and the residuals rapidly increased and exceeded the threshold value at the 12th second, thereby the fault would be detected.
Design and simulation of aero-engine steady-state and transient-state control integration
WU Jun-feng, GUO Ying-qing
2013, 28(6): 1436-1440.
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Abstract:
The issue of synthesizing steady-state and transient-state control laws for a turbofan engine was studied.Firstly,a number of steady-state point PI(proportional integral) controllers were designed using root locus analysis and time domain method from ground idle power to take-off power,and furthermore full flight envelope controllers were designed using interpolation method and corrected parameters.Secondly,the synthesis control system was acquired by integrating schedule-based transient control and steady-state control through max/min logic into which an anti wind-up module was added to cope with the influence of integrator wind-up.Finally,the synthesis control system was validated in software MATLAB/Simulink.The results indicate that the synthesis control system has the following advantages:(1) during steady-state,the anti-disturbance quality is good;(2) during transient-state,the response curve is flat;(3) the system uses a variety of restrictions effectively with both anti-windup and smooth switching functions.

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