2013 Vol. 28, No. 5

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Multiple precision MDO strategy for turbine blade
WANG Rong-qiao, JIA Zhi-gang, HU Dian-yin, FAN Jiang, Shen Xiu-li
2013, 28(5): 961-970.
Abstract PDF(1036KB) icon1861 icon1122
Abstract:
Based on kinds of different precise analysis methods on the turbine design,the multiple precision strategy was put forward in order to balance the cost and the precision on turbine MDO.This strategy studied the variable complexity method (VCM) which was improved by the two-point scale function, the new updating technology and three kinds of precise models including the fluid-solid closely couple analysis,the fluid-solid-thermal loosely couple analysis and the approximate equation.The strategy solves the difficulty of disciplinary decoupling and coordination by the collaborative optimization (CO) strategy.Finally,using 9 high precision fluid-solid coupling analysis,the new strategy can finish the turbine MDO with acceptable performance.
An image reconstruction method for improving CT spatial resolution
FU Jian, TAN Ren-bo, ZHAO Feng
2013, 28(5): 971-976.
Abstract PDF(1019KB) icon2055 icon1084
Abstract:
In order to improve the spatial resolution of industrial computed tomography (CT) without changing the hardware,the half-pixel offset scanning mode was analyzed and a direct reconstruction algorithm,which was based on the algebraic iteration technique,was proposed.This algorithm adopted area-weight to execute directly the iterative update of the reconstructed value using the acquired projection data.Computer simulation analysis with a star-type spatial resolution phantom was implemented and a modulation of 0.8 was reached at the cut-off frequency.It demonstrates that the proposed method has the potential of improving the spatial resolution.The industrial CT experimental results of a standard spatial resolution phantom validate the feasibility and the effect of the method.The proposed approach is easy to implement and has a promising application future.
Looseness-rubbing coupling fault of dual-disk three-support rotor-bearing system
LIU Yang, TAI Xing-yu, MA Hui, WEN Bang-chun
2013, 28(5): 977-982.
Abstract PDF(834KB) icon1752 icon1186
Abstract:
For looseness-rubbing coupling fault of rotor-bearing system caused by pedestal looseness,the mechanical model and finite element model of dual-disk three-support looseness-rubbing coupling fault of rotor-bearing system were established.The research of effect of rubbing stiffness and looseness stiffness on dynamics characteristics of the system was done with equivalent stiffness model on the loose support,nonlinear finite element method and contact theory.Through the relevant research and analysis,it is found that looseness-rubbing coupling fault mainly is embodied in the rubbing fault.It is also found that high and low peaks appeared alternately in the time-domain graph and the shape of the axis orbit is trapezoid.This feature can be a basis which can diagnose looseness-rubbing coupling fault.
Dynamic assessment model for MTBF of aero-engine based on fuzzy integral
WANG Da-wei, WANG Wei, FENG Zhen-yu
2013, 28(5): 983-988.
Abstract PDF(346KB) icon1682 icon941
Abstract:
The lag problem of reliability assessment of the aero-engine was studied aiming at the limitation existed in the traditional assessment methods.The dynamic aero-engine reliability assessment model was established by using fuzzy integral method.Reasonably fault samples of every stage for data fusion were used,which were key issues of dynamic assessment for aero-engine reliability.The failure intensity factor was introduced.The failure rectification process was expressed by the low half normal distribution function of failure intensity factor.Fuzzy density was obtained by the failure intensity factor.The reliability targets of aero-engine were fused using Choquet fuzzy integral method.Dynamic assessment for reliability targets of aero-engine was realized.The research results were applied to the small turbofan engine.Using Choquet fuzzy integral data fusion method for dynamic assessment can take the importance of each stage fault samples in consideration.The method provides scientific evaluation for the aero-engine reliability.
Axial displacement and rubbing vibration of rotor system caused by thermal expansion
PAN Jian-zhi, CAO Deng-qing, CHU Shi-ming, WANG Li-gang
2013, 28(5): 989-998.
Abstract PDF(1072KB) icon1674 icon1538
Abstract:
The effect of non-uniformity and time varying characteristic of temperature field was quantified and provided as an axial clearance analytical expression when studying the rubbing process,and the rubbing between rotor and stator caused by the axial displacement was approximated as surface contact/squeeze process.Then the point contact or embedment of Hertz contact model was improved to an annulus surface contact or embeded model.On this basis,a new dynamical model of rotor system subjected to the rubbing force caused by axial squeeze was established.Finally,the numerical integration method was employed to solve the dynamical model,and the effect of annulus surface friction on the system was investigated for both the warming and steady temperature periods.The numerical results show that rubbing failure caused by axial displacement of rotor is as important as other rubbing phenomena;the surface rubbing is also an important factor which affects the normal operation of the engine.
Nonlinear dynamics of coupled rotor/fuselage system for shipboard helicopter
LIU Yang, XIANG Jin-wu
2013, 28(5): 999-1005.
Abstract PDF(800KB) icon2028 icon1278
Abstract:
The coupled rotor/fuselage system was developed using multibody dynamics approach. The undercarriage of helicopter comprised the oleo and tyre as a nonlinear system. The ship had the roll and pitch motion in the form of harmonic oscillation. Under different rotor speeds and excited frequencies, the response and dynamic stability of the rotor/fuselage system had been investigated. The result shows that the fuselage and the rotor oscillations may generate limit cycle oscillations under the excitement of ship. When the rotor oscillation is equal to the excited frequency of ship, the response of regressing lag will bring about limit cycle oscillations, and the center of gravity of rotor will shift from the hub, leading to ship resonance.
Performance reliability prediction for civil aviation aircraft engine based on Wiener process
ZHU Lei, ZUO Hong-fu, CAI Jing
2013, 28(5): 1006-1012.
Abstract PDF(393KB) icon2130 icon1095
Abstract:
With respect to degradation data of civil aviation aircraft engine, a method which combined prior degradation information with current degradation data was proposed to assess performance reliability and residual life. Firstly, on the basis of prior degradation information, prior distributions of Wiener process parameters were confirmed. Secondly, by using Bayesian method, prior distributions could be updated to posterior distributions, and then the reliability and residual life of an engine were evaluated based on the posterior distributions. The proposed method can update the evaluation results of reliability and residual life whenever new degradation data is available. Finally, a practical example of degradation data of civil aviation aircraft engine was used to testify the validity of the proposed model. The result shows that the deviation of No.41 engine in 2000 cycles and 3000 cycles is 0.060 and 0.018, which satisfies the management requirement of engine fleet of airlines.
Robust design of turbine-blade low cycle fatigue life based on neural networks and fruit fly optimization algorithm
ZHOU Ping, BAI Guang-chen
2013, 28(5): 1013-1018.
Abstract PDF(477KB) icon1953 icon1315
Abstract:
By combining generalized regression neural network (GRNN) with fruit fly optimization algorithm (FFOA) and using FFOA multi-point global search ability to optimize the random variable which affects the fatigue life, a robust optimization design for low cycle fatigue life of turbine-blade can be made on the base of probability analysis for turbine-blade low cycle fatigue life.Optimization results show that the probability interval of fatigue life decreases 17.9%,and the sensitivity of the low cycle fatigue life of the random variable can be reduced,so the fatigue life can be estimated more accurately.Optimization results indicate that the proposed method is available and feasible for the engineering application.
Aerodynamic design of highly-loaded blade in low-pressure turbine with low Reynolds number
YANG Lin, QIAO Wei-yang, LUO Hua-ling, MU Zhong-qiang, HOU Wei-tao
2013, 28(5): 1019-1028.
Abstract PDF(1171KB) icon1994 icon1211
Abstract:
Study was carried out using the combination of numerical simulation and cascade experiment to understand the effects on flow loss from loading distribution design and non-smooth profile design based on two-dimension span-wise groove combined with loading distribution design. Research shows that fore-loaded design is superior to aft-loaded design in two-dimension aerodynamic performance under low Reynolds number conditions; non-smooth profile design based on two-dimension span-wise groove can improve aerodynamic performance at low Reynolds number, and decrease it at high Reynolds number; non-smooth profile design based on two-dimension span-wise groove combined with aft-loaded design can improve aerodynamic performance in wider range of Reynolds number.
Influence of frequency mistuning on aeroelastic stability of blade
ZHENG Yun, WANG Jing
2013, 28(5): 1029-1036.
Abstract PDF(1070KB) icon2324 icon1329
Abstract:
Aeroelastic stability of oscillating blades was simulated by solving unsteady compressible Navier-Stokes equations with dynamic deforming mesh, and the effect of frequency mistuning on aero-dynamic damping was investigated. The aeroelasticity algorithm was validated by the simulation of aeroelastic behavior of the 10th aeroelastic standard configuration. The aero-dynamic damping of the oscillating cascade was calculated with different inter-blade phase angles (IBPA) and reduced frequencies. The effects of mistuning pattern and frequency of mistuning on aero-dynamic damping and the mechanism of frequency mistuning on aeroelastic stability were studied. The results indicate that frequency mistuning is an effective method in improving aeroelastic stability and the coupling of the blade vibration and the effect of IBPA were weakened by frequency mistuning; the aeroelastic stability of blade increases with the increase of frequency mistuning. 3-D aeroelstic computation of the 4th aeroelastic standard configuration was performed to examine the effects of frequency mistuning on aeroelastic stability margin, and the laws of IBPA and aeroelastic stability increasing was validated.
Numerical investigation on superimposed effect of wake/potential interaction in axial-radial combined compressor
LIU Yin-hong, YANG Ce, ZHAO Ben, LAO Da-zhong, MA Chao-chen
2013, 28(5): 1037-1046.
Abstract PDF(1206KB) icon2264 icon1151
Abstract:
Three-dimensional unsteady viscous numerical simulation was conducted on an axial-radial combined compressor to study the interaction characteristic of wake/potential and downstream potential effects on the mid stator vane.The axial rotor/stator vane,axial rotor/impeller and stator vane/impeller interaction effects on the impeller inlet angle were also investigated by using the effect factor split of the combined compressor unsteady flow.The results show that upstream wake and downstream potential lead to reinforce/suppress effect while coupling in the mid vane passage.Due to the different phases of axial rotor/stator vane,axial rotor/impeller and stator vane/impeller interaction,work fluid at impeller inlet encounters distortion,which directly affects the amplitude of inlet angle.
Experiments of effects of inlet-air distortion on aerodynamic performance in transonic compressor
LI Mao-yi, YUAN Wei, LU Ya-jun, SONG Xi-zhen, LU Li-peng
2013, 28(5): 1047-1056.
Abstract PDF(1627KB) icon1453 icon1001
Abstract:
The inlet-air distortion which was caused by high angle-of-attack flight was simulated by plugboard.Experiments were conducted on a transonic axial-flow compressor's rotor at 98% rotating speed.The flow-field characteristics and mechanism of performance degradation were analyzed in detail.The compressor inlet was divided into four sectors at circumference under inlet-air distortion.They were undistorted sector,transition sector A where the rotor was rotating into the distortion sector,distorted sector and transition sector B where the rotor was rotating out of the distortion sector.The experimental results show that compared with undistorted sector,there is a subsonic flow in transition sector A,so the pressure ratio is decreased by a large margin in this sector.However, the shock wave is enhanced in distortion sector and transition sector B, and thus the pressure ratio increases in these sectors.Because of the different works at circumference,the phase angle of total pressure changes 90? when the inlet total pressure distortion passes through compressor rotor.In addition,the frequency and amplitude of disturbances in front of the rotor strengthenes under inlet distortion,so the unstable flow would take place in advance.In addition, the position of stall inception is in one of the transition sectors.
Transitional flow on turbomachine blade using discontinuous Galerkin method
SONG Yin, FENG Fan, GU Chun-wei
2013, 28(5): 1057-1065.
Abstract PDF(1349KB) icon1478 icon908
Abstract:
Large eddy simulation (LES) and a correlation-based transition model were applied with discontinuous Galerkin method (DGM) to investigate transitional flow on turbomachine blade.The methodology was used to simulate the flowfield within T106 turbine cascade and Zierke-Deutsch compressor cascade.Comparison was made between the results of transition model and LES for T106 cascade.The pressure distribution and the locations of separation bubbles calculated by the transition model and LES both agreed well with experimental results. The axial locations of separation bubbles predicted by LES and the transition model are 0.145~0.165m and 0.150~0.168m, respectively.The complex flow details,including the vortex structures in the separation bubble and the dynamic process of laminar separation,vortex shedding and wake diffusion,were simulated by LES,which can help to understand the transition mechanism.As for the transition model,although less flow details were captured,the calculated pressure distribution and the location of separation bubble agreed well with experimental data and LES results.The advantage of the transition model lies in the low computational costs,and it is more suitable for engineering applications.The accuracy of the transition model was further validated by the calculation of Zierke-Deutsch compressor cascade.
Characteristics of high-turning tandem stator in highly loaded small compressor
WEI Wei, LIU Bo, CAO Zhi-yuan, WANG Lei
2013, 28(5): 1066-1073.
Abstract PDF(1304KB) icon1652 icon966
Abstract:
A redesigned high-turning stator was studied in a highly loaded small compressor with tandem blades.During three dimensional (3-D) stacking of the tandem stator,the appropriate positive bow was adopted to achieve the best relative location between the front and rear blades.Performance curves of the original and redesigned stages were obtained by 3-D steady numerical simulations at different conditions under the design speed.The results show that separation of the original stator near the casing has been weakened.The adiabatic efficiency increases by 3.5% approximately at the design point;the front blade withstands main variations of stator's incidence,and the stability margin also increases by 2%.The redesigned tandem stator can distribute the high-turning blade loading along the axial chord more uniformly,so it is beneficial for the flow control of the blade boundary layer.
Dynamic derivative analysis for hybrid airship incorporating lift and buoyancy
MA Dong-li, YE Chuan
2013, 28(5): 1074-1080.
Abstract PDF(542KB) icon1546 icon1054
Abstract:
Translational and rotational acceleration derivatives of sphere and ellipsoid were calculated,and pitch oscillation of the NACA0015 airfoil was simulated.The applicability of computational fluid dynamics(CFD) method was validated.Forced oscillation of hybrid airship incorporating lift and buoyancy was simulated.The dynamic derivatives of whole airship,wing,hull,horizontal tail and vertical tail were obtained.The results were compared with those of conventional airship.The heave and roll velocity derivatives are much larger than those of conventional airship due to the contribution of wing.The viscous force and the interference of wing on hull and tail are important for the acceleration derivatives in the heave,roll and pitch directions.Consequently,the acceleration derivatives can not be simplified as additional mass coefficients.
Engine nacelle lip design for high speed TPS wind tunnel tests
TAO Yang, LIU Guang-yuan, ZHANG Zhao, GUO Dan-ping, LIN Jun, XIONG Neng
2013, 28(5): 1081-1085.
Abstract PDF(613KB) icon1699 icon1008
Abstract:
Computational fluid dynamics (CFD) was adopted to investigate the effects of mass flow rate difference on nacelle outer surface pressure coefficient distribution.Inverse design optimization technique was used in engine nacelle lip correction in order to adjust the turbofan propulsion simulators(TPS) outer surface pressure distribution to make it identical with that of the real engine.The engine nacelle lip inverse design method can be used in 2.4 m transonic wind tunnel to improve jet engine flow simulation test accuracy.
Aeroelastic stability analysis of composite hingeless rotor based on free-wake model
XIAO Yu, XU Guo-hua, ZHAO Qi-jun
2013, 28(5): 1086-1094.
Abstract PDF(1354KB) icon1443 icon1127
Abstract:
Based on finite element method (FEM) and free-wake method, an aeroelastic stability analysis model of composite hingeless rotor was developed. In order to simulate the aeroelastic behavior of composite rotor, 2-D linear FEM analysis was employed to obtain the sectional properties, and 1-D beam was modeled by 23 degree of freedom (DOF) nonlinear beam element which included transverse shears. The free-wake model was adopted to calculate non-uniform induced velocity field, and a highly-efficient and accurate aerodynamics analysis module was established by using lifting-line theory. On the basis of these, the stability analysis for composite hingless rotor was carried out. It is demonstrated by numerical simulation that the present model is capable to predict unsteady airloads and aeroelastic stability characteristics of composite rotor. Finally, the effect of material ply orientation on hingless rotor aeroelastic stability was analyzed, and it can be seen from the results that under the condition of low thrust coefficient (0.0025), the rotor aeroelastic instability may occur when ply angle of the vertical wall varies between 10°and 25°, which should be avoided in rotor design.
Simulation and analysis of performance for combination of lift fan and turbofan engine power system
LIU Shuai, WANG Zhan-xue, CAI Yuan-hu, LIU Zeng-wen
2013, 28(5): 1095-1100.
Abstract PDF(709KB) icon2095 icon1232
Abstract:
Based on component matching and multi-point analysis,a turbofan plus lift fan engine performance simulation model was developed.The model was tested by the F135 engine.The simulation results show that the engine performance is the same as the conventional turbofan in cruise mode.When the lift fan is engaged,the matching point between the low pressure turbine,the cruise fan and the lift fan is achieved by adjusting the nozzle throat area,the bypass exit area,and the low pressure turbine throat area.Based on this model,the cycle parameter matching and performance analysis can be achieved for the turbofan plus lift fan engine in different missions.
Effects of bleeding on self-starting characteristics of side-compression hypersonic inlet
ZHAO Yi-long, FAN Xiao-qiang, WANG Yi, WANG Zhen-guo
2013, 28(5): 1101-1106.
Abstract PDF(941KB) icon1505 icon908
Abstract:
Various bleeding cases with slots and holes were designed for a side-compression hypersonic inlet,and the numerical simulation was conducted.The results show that the self-starting characteristics of the inlet can be significantly improved,and bleeding in the separation zone of the inlet has the best effects.The self-starting Mach number of the inlet was reduced from 4.6 to 3.7 in the research.The inlets with different attack angles were tested in the wind tunnel at the flow condition of Mach 4.The experimental results confirmed the bleeding effects on the improvement of the self-starting characteristics of the inlet.
Aerodynamic performance analysis of electric vehicle with different air-inlet and air-outlet patterns and battery positions
XU Xiao-ming, ZHAO You-qun
2013, 28(5): 1107-1111.
Abstract PDF(364KB) icon1536 icon999
Abstract:
Using software GAMBIT as pre-processor and software FLUENT as calculator and post-processor,research was done on the effect of air-inlet and air-outlet patterns and battery positions on the electric vehicle aerodynamic performance. The results show as follows:up-outlet mode of wind with one hole has the best aerodynamic performance,and down-outlet mode of wind has the worst aerodynamic performance;with the distance between battery and power cabin increasing,the aerodynamic performance of electric vehicle is improved,and then deteriorated,and the distance of 230mm fits the best electric vehicle aerodynamic performance.
Calculation of integrated performance for aircraft/engines
QIAN Fei, SONG Wen-yan, LUO Guang-qi
2013, 28(5): 1112-1118.
Abstract PDF(932KB) icon1933 icon1091
Abstract:
An integrated performance computing model for aircraft/engines was studied,and a visual software based on the model was further developed.The model consisted of engine's uninstalled performance computing model,inlet and nozzle/aftbody performance characteristic transferring model,engine's installed performance computing model and flight performance computing model.Using inlet and nozzle installation methods(INSTAL),the installed engine performance was calculated in conjunction with uninstalled engine performance and installed performance characteristics of the inlet and nozzle/aftbody which had been obtained through inlet and nozzle/aftbody installation transferring program.Based on above study,the aircraft performance was calculated as well.The software was applied to estimate integrated performance of a certain aircraft.The results show: (1) comparing with the empirical formula method, the degree of closeness between the estimation of installed engine performance using INSTAL and the data from designer is increased in general, and it can be increased by 13% in maximum; (2) the calculating results are reasonable with short executing time and high accuracy.
Numerical investigation of thermal radiation in a nacelle
WU Yu, ZHONG Jian-long, LÜ Qi-ming
2013, 28(5): 1119-1124.
Abstract PDF(640KB) icon1769 icon960
Abstract:
Based on computational fluid dynamics method,airplane in idle condition was studied in conjunction with heat transfer in a nacelle.And different radiation computation methods including spherical harmonics,discrete ordinate and Monte Carlo method were adopted to simulate thermal radiation.The result shows that coupling effect of radiation and convection is obvious.In addition,compared with the simulation result of pure convection,nacelle ambient temperature predicted by coupling way is 7%~30% higher.While selective absorption of air under infrared radiation is taken into account,the ambient temperature rises further.Thus the effect of thermal radiation should not be ignored to simulate nacelle hear transfer in ground condition.
Numerical simulation of inertial particle separator with scavenge scroll
TONG Yue, TAN Hui-jun, ZENG Ping-jun
2013, 28(5): 1125-1133.
Abstract PDF(1459KB) icon1550 icon987
Abstract:
An inertial particle separator with scavenge scroll was numerically studied to obtain its flow structure and scavenge efficiency performance characteristics.Results indicate that the flow fields at the top and bottom of the scavenge path are not smooth.Thus,the gas from the circular inlet can not flow into the scavenge scroll equably.When the bypass rate is 19%,the total pressure recovery coefficient of the core flow is 0.982;AC coarse and C-spec separator efficiencies are 64.8% and 76.6%,respectively.The flow structure and performance characteristics of the inertial particle separator are improved,and especially the vortical structures in scavenge scroll are of advantage to sand separating when the flow divider is added to the top of the scavenge scroll.With the same bypass rate,AC coarse and C-spec separation efficiencies increase 18.1% and 20.9%,respectively.Besides,the total pressure recovery coefficient of the core flow does not decrease much.
Numerical simulation on a certain trapped vortex combustor
ZHAI Xiao-lei, PENG Ri-liang, FAN Wei-jun, ZHANG Rong-chun, WANG Wei-jian
2013, 28(5): 1134-1141.
Abstract PDF(1347KB) icon1699 icon933
Abstract:
A fuel injector was designed for a certain type of trapped vortex combustor.Then,experiments were conducted to check its atomizing performance under various conditions,including different gas to liquid ratios,gas pressures and liquid pressures.The cold and hot simulations of the combustor were conducted to study the performance,and the velocity field,the temperature field and mass fraction distribution of the combustor were obtained.The simulation results show that the combustor is reasonably designed with compact structure and high combustion efficiency.The wall temperature distribution of the cavity is ideal.The changing regularity of the pressure loss and the outlet temperature distribution were obtained by numerical simulation and experimental research.The total pressure loss of the combustor is a bit larger and the temperature distribution of outlet is uniform.The results can provide relevent reference for the engineering application of the trapped vortex combustor.
Experiment on performance of interstage turbine trapped vortex combustor with acoustic energy nozzle
TAN Mi, FAN Wei-jun, ZHANG Rong-chun, SONG Shuang-wen, XING Fei
2013, 28(5): 1142-1149.
Abstract PDF(1006KB) icon1803 icon1001
Abstract:

Performance of an interstage turbine burner with an acoustic energy nozzle was investigated experimentally.The experimental result shows that the air excess coefficient of lean blowout is in the range of 25~35 under the condition of Mach number being 0.20~0.40,and the range of stable combustion is relatively wide.The uniformity of outlet temperature distribution is improved with the increase of air excess coefficient.The combustion efficiency is in the range of 96%~98%,and it decreases as the air excess coefficient decreases.Inlet Mach number has little effect on ignition performance,lean blowout performance,outlet temperature distribution and combustion efficiency.The maximum wall temperature locates on the after-wall of the cavity.The total pressure loss coefficient is in the range of 0.03~0.11,and it is about 0.015 higher in hot state than in cold state.The emission index of CO is in the range of 20~46 and that of NOx is in the range of 0.9~2.1.The inlet Mach number and air excess coefficient both have significant effect on the pollutant emission.
Active stability control method for turbofan engine based on post-stall model
ZHANG Hai-bo, HUA Wei, WU Wei-chao
2013, 28(5): 1150-1158.
Abstract PDF(1088KB) icon1586 icon1490
Abstract:
A method to set up turbofan engine post-stall model was proposed in consideration of the volume effectiveness,the characteristics of post-stall of the fan and compressor,the combustors with rich fuel and lean fuel characteristics.The models of engine inlet's total temperature distortion,total pressure distortion,and the combination of two kinds of distortions were established.The active control method proposed was based on the correlation measure of pressure.Correlation measure threshold crossing events increased in magnitude and number as the compressor approached the limit of stable operation,so the stall margin could be calculated in a real-time manner.The active control mode was established based on robust control design method.At last,the numerical simulations were carried out.The results show that the active control based on the method of correlation measure successfully makes the compressing part of engine do not enter into stall during transient process,highly improving the dynamic response in the whole transient process.
Identification of T-S fuzzy model for aero-engine based on flight envelop division
WANG Lei, XIE Shou-sheng, MIAO Zhuo-guang, REN Li-tong, ZHANG Zi-yang
2013, 28(5): 1159-1165.
Abstract PDF(728KB) icon1703 icon1069
Abstract:
For the problems of time-consuming calculation and data dependence in Takagi-Sugeno(T-S) fuzzy model of aero-engine,a new T-S modeling algorithm based on flight envelop division was proposed.The premise structure of fuzzy model was confirmed by dividing the flight envelop and selecting the nominal points.The state space model at each nominal point was regarded as the consequence of T-S model.Finally,the parameters of premise structure were identified by training.Simulation results show that the new algorithm shortens the modeling time.The absolute error of high-pressure rotor speed is less than 0.25%,and that of low-pressure rotor speed is less than 0.10%.
Internal model control method based on predicted torque feed-forward for turbo-shaft engine
LU Chen-hao, LI Qiu-hong, JIANG Jie, LI Ye-bo
2013, 28(5): 1166-1172.
Abstract PDF(699KB) icon1898 icon1173
Abstract:
The power turbine rotor speed controller based on internal model principle was designed for turbo-shaft engine.To suppress the disturbance of the torque variation of the main rotor to the power turbine rotor speed,a torque prediction method based on extreme learning machine was proposed.The training of extrem learning machine(ELM)was based on the data of dynamic simulation,and the input variables were obtained by correlation analysis approach.The internal model based on power turbine rotor speed controller was designed by pole placement.The internal model of input signals was embedded into the controller to obtain robust tracking.In order to achieve effective compensation of the engine's load variation,the proportional-differential feed-forward compensator was adopted.The simulation results indicate that the torque prediction based on ELM has excellent accuracy,and the relative prediction error is less than 1.5‰.Compared with the control without torque feed-forward,the proposed control method reduces both the overshoot and droop of the power turbine rotor speed more than 30% during maneuvering flight.
Oil-free vacuum system design based on vacuum plume experiment
LING Gui-long, CAI Guo-biao, ZHANG Jian-hua
2013, 28(5): 1173-1179.
Abstract PDF(759KB) icon1517 icon880
Abstract:
An oil-free vacuum system for vacuum plume and thermal vacuum experiments was established.The composition of vacuum system,scheme design and working modes were described in detail.The vacuum pumping time under different working modes was calculated.The vessel ultimate pumping speed tests were conducted on the roots pump,molecular pump and cryopump,respectively.The test results show that the technical indexes of the instruments are attained.Finally,the pressure maintenance ability of the vacuum vessel was measured.The average pressure rise rate of the vessel is 0.111Pa/h,corresponding to an average leakage rate of 7.24Pa·L/s,which demonstrates that the vacuum vessel has achieved a high process level.According to the experimental requirements and the selection of failure mode,the vacuum system has several working modes to choose,which increases the practicality and economy of the vacuum plume investigation experiment system.
Orthogonal optimal design of solid fuel formulation for H2O2/HTPB hybrid rocket motor
ZENG Peng, TIAN Hui, LI Xin-tian, CAI Guo-biao
2013, 28(5): 1180-1186.
Abstract PDF(1781KB) icon1796 icon999
Abstract:
Nozzle two-phase flow in H2O2/HTPB hybrid rocket motor was numerically simulated by the stochastic trajectory model.Accuracy of the simulation results was verified by comparison with experimental data.A parametric study of different condensed phase mass fractions and particle mean diameters was performed to investigate the influence of condensed phase parameters on nozzle performance,and the results show that the nozzle efficiency decreases with the increasing of condensed phase mass fraction and particle mean diameter.An orthogonal design of fuel formulation was conducted to investigate the effect of different fuel additives(Al,Mg,AP and B) on the motor performance,and an optimal formulation was obtained.The results indicate that the condensed phase mass fraction increases with the increasing of mass fractions of Al and Mg,and is low dependent on the mass fractions of AP and B;the addition of Al,Mg,AP and B has little effect on the maximum specific impulse,and can enhance the maximum density specific impulse effectively.Moreover,the addition of Al and Mg reduces the nozzle efficiency,the actual specific impulse and the actual density specific impulse,while the addition of AP and B has little effect on the nozzle performance.
Estimation of thermal conductivity of solid propellants based on particle packing model
ZHI Shi-jun, SUN Bing, ZHANG Jian-wei
2013, 28(5): 1187-1191.
Abstract PDF(644KB) icon1984 icon874
Abstract:
To better estimate the thermal conductivity of solid propellants,the molecular dynamics method was adopted to match the size distribution and volume fraction of solid propellants.The finite element method was employed to compute the steady heat conduction of solid propellant meso-scale models.According to the homogenization method,the mean temperature and mean heat flux were calculated.Based on the mean temperature,mean heat flux and steady heat conduction equation,the effective thermal conductivities of two- and three-phase solid propellants were obtained.The error between the simulation result and test data of two-phase solid propellants is only 3.63%. The results show that the effects of particle size and random distribution of particles can be fully considered when the particle packing model is employed in the process of estimating the thermal conductivity of solid propellants. The particle packing model is more consistent with the micro-structural features of real solid propellant, and the results are accurate and reliable.
A contact finite element method for dynamic analysis of continuous engaged gear pairs
WU Yong-jun, WANG Jian-jun
2013, 28(5): 1192-1200.
Abstract PDF(1363KB) icon1969 icon1282
Abstract:
Based on the analysis of the characteristics for different typical meshing states, a dynamic contact finite element analysis method, considering the variation of the engaged tooth pairs, the loaded elastic deformations and the sliding friction, was presented for the continuous engaged gear pairs. Then the dynamic transmission errors and the dynamic contact force for three kinds of continuous engaged gear models were compared using the presented method, and the effects of each factor on the dynamic meshing characteristics were obtained. The results show that the presented method is effective on simulating the more actual dynamic meshing characteristics of continuous engaged gear pairs in single or double tooth pair contact, including the pitch point impact caused by sliding friction, the meshing impact and the time-varying meshing stiffness excitation caused by elastic deformation. The impact force and time of the approach and recess meshing impact, the influence of the sliding friction and tooth profile modification on dynamic meshing characteristics were also obtained by the presented method. And the dynamic meshing characteristics gotten from the presented method is quite accordant with the characteristics of the continuous engaged gear drives for typical meshing states.

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