2005 Vol. 20, No. 5

  Previous Issue | Next Issue 
Display Method:
Prediction Method for Generalized Time-Varying ARMA Series
WANG Zhi-hua, FU Hui-min
2005, 20(5): 713-717.
Abstract PDF(908KB) icon1389 icon617
Abstract:
A method for predicting generalized time-varying ARMA series is proposed.The prediction formulas of time-varying and generalized time-varying series and their mean squared errors are presented.The method can analyze the generalized time-varying series(or signal) whose mean,variance,autoregressive and moving average coefficients vary with time.It can be used in meteorology,communication,automatic control,structure response analysis,fault diagnosis and other fields.The precision of the presented method is higher than the traditional method in predicting generalized time-varying ARMA series.
Experimental Investigation of Multi-Scale Eddy Structures' Intermittency in Turbulent Flow Using Probability Density Function of Wavelet Coefficients
JIANG Nan, CHAI Ya-bin
2005, 20(5): 718-724.
Abstract PDF(759KB) icon2015 icon589
Abstract:
The longitudinal velocity component in a fully developed turbulent boundary layer was measured by IFA300 hot wire anemometer and the statistical properties were studied experimentally.The velocity time sequence at different vertical locations in the turbulent boundary layer was obtained with resolution higher than the frequency that corresponds to Kolmogorov dissipative scale.The velocity signals were analyzed by wavelet transform,which described the local relative strain distortions for multi-scale eddy structures in turbulent flows.The Extended Self-Similarity(ESS) was applied to the statistical analysis of the multi-scale wavelet coefficients.The intermittency features,studied through the probability density function of the wavelet coefficients,were found to be influenced by multi-scale coherent eddy structures and were confirmed to be dependent on the distance from the wall.The intermittency features and the probability density function were compared between before and after excluding multi-scale coherent eddy structures.It has been observed that multi-scale coherent eddy structures were responsible for the anomalous scaling law in turbulent boundary layer.When such coherent eddy structures are eliminated,intermittency anomalies are no longer observed and the Kolmogorov linear scaling prediction is achieved.This phenomenon is obvious in the entire turbulent boundary layer.
Propagation of Circumferential Pressure Distortion in Axial Flow Compressors
WU Hu, FENG Wei-lin
2005, 20(5): 725-730.
Abstract PDF(484KB) icon1760 icon519
Abstract:
A new model was established for the prediction of the decay of circumferential pressure distortion in multistage axial flow compressors.An efficient calculation procedure was developed which could be used to predict the propagation of the total pressure,temperature and velocity distortion through axial flow compressors.The validity of this model was demonstrated by comparing the numerical results with experimental data.Based on the model given,suggestions can be made for the design of distortion-tolerant axial flow compressors.
Unstart Simulation of Scramjet Inlets
BAO Wen, CHANG Jun-tao, GUO Xin-gang, CUI Tao
2005, 20(5): 731-735.
Abstract PDF(832KB) icon1901 icon528
Abstract:
The 2-D internal steady flow of the scramjet inlet-isolator was numerically simulated by the prevailing software,the numerical simulation results of the process from start to unstart in the scramjet inlet were presented.The static pressure contours of the scramjet inlet-isolator under different back pressure and angle of attack were given.The distribution of static pressure of inlet-isolator was analyzed and the unstart judgement criterion was given.
An Engineering Method of Determining Turboshaft Engine Minimum Required Torque for Starting
CAI Jian-bin, YIN Ze-yong, XIONG Yan, CHENG Ben-lin, LI Liang
2005, 20(5): 736-739.
Abstract PDF(328KB) icon2227 icon526
Abstract:
Based on a turboshaft engine test data gathered during cold run,a method of calculating engine resistant torque and torque for acceleration was introduced.According to maximum acceptable start time at the temperature same as engine testing,a method for determining turboshaft engine minimum required torque for starting was put forward and it is proved by test that the calculated result is in accordance with the test data.
Research of Bump Inlet(DSI) Model Design and Its Aerodynamic Properties
ZHONG Yi-cheng, YU Shao-zhi, WU Qing
2005, 20(5): 740-746.
Abstract PDF(1088KB) icon2392 icon536
Abstract:
Using an engineering design software of bump inlet based on waverider theory,an under fuselage bump inlet was designed based on the conic flow accurate stream line method.With regard to distribution of Mach numbers in the symmetric plane,limiting stream lines on the bump surface and distribution of pressure recovery coefficient(Cp) in the cross-section,the flow characteristics of the inlet were analyzed.It is shown that flow characteristics of the designed bump inlet are well consistent with the theoretical analysis with ideal gas.Supersonic aerodynamic properties of the bump inlet were analyzed by comparing the experimental results with computational ones.The results show that under design point condition,the average total pressure recovery coefficient at exit of bump inlet is nearly 0.87 at design Mach number of 2.0,and no less than 0.91 at mach number of 1.8.
Fault Diagnosis for Aeroengines with Components' Characteristics Unavailable
XIAO Hong, XUE Qian, LIAN Xiao-chun, WU Hu
2005, 20(5): 746-750.
Abstract PDF(297KB) icon1732 icon561
Abstract:
A method was developed to simulate turbofan component characteristics.Nonlinear simplex optimization was used while keeping the deviation of engine performance and working process parameters a minimum as objective function and component coupling coefficients as optimized parameters.A fault diagnosis equation for the twin-spool mixed flow turbofan engine was established based on the simulation and gas path analysis.Investigation shows that the symptom parameters selection and their relatively deviations exert great influence on the diagnostic accuracy.The symptom parameters and their relative deviations should be kept not greater than one third of their threshold values.Relative errors between the deviation of the real fault symptom parameters and of the fault derived from the model are controlled less than 5%.Inaccurate fault isolation does not appear while the developed model was applied to the diagnosis of the available fault cases.
Blind Source Separation of Rotor Vibration Faults
LI Shun-ming
2005, 20(5): 751-756.
Abstract PDF(990KB) icon1834 icon559
Abstract:
The basic principle of blind source separation was introduced in the paper.Based upon the principle of minimum mutual information,a new method that estimates the separation matrix by independent component analysis was established.The method is named as speedup gradient method.Based on the method developed,the numerical simulation of vibration signal blind source separation was performed.The waveforms of separated signals are identical with source signals.This blind source separation method was applied to multi-sensor signals of a real rotor faults.The results show that the fault characteristics are separated satisfactorily.The real example shows the validity of this method and the practicability for rotors' faults separation.
An Approach to Reliability Allocation for Digital Aeroengine Control Systems
ZHAO De-zi, WEN Wei-dong
2005, 20(5): 757-761.
Abstract PDF(662KB) icon1787 icon469
Abstract:
The tendency factor was introduced into the voting model in Vague sets,and the weighting method for the influential factors of reliability was proposed.Combined with the fuzzy decision-making theory,the model synthetically assessing the relative failure coefficients between the units of a system was developed.The approach to fuzzy reliability allocation for an aeroengine digital control system with cold standby units was presented with the aid of the model and MATLAB.This approach is suitable for conceptual and preliminary design where there is lack of system reliability data.
Aero-Engine Turbine Blade Containment Tests and Numerical Simulation
XUAN Hai-jun, HONG Wei-rong, WU Rong-ren
2005, 20(5): 762-767.
Abstract PDF(447KB) icon2345 icon506
Abstract:
In order to have more understanding of the process of breaking off blade impact on containment ring,a series of impacting tests to investigate the aero-engine containment capability has been carried out in a high speed spin facility.Single plate blade was used during the tests.Impacting processes were simulated with finite element numerical method based on impact dynamics theory.Single released blade exerted two impacts one after another on the containment ring at two different points.The second impact is more dangerous than the first.Radial bulge of the containment ring at impact point increases linearly with the initial kinetic energy of the broken blade.However,circumferential distances between two impacted zones decrease linearly with initial kinetic energy.Numerical simulations show a good agreement of the predicted impacting process with the experimental results.The results can be used as a reference for the containment ring optimum design and blade containment capability check.
Effect of Elastic Modulus on Parameter of Low Cycle Fatigue Performance
ZHANG Guo-dong, SU Bin, WANG Hong, HE Yu-huai, XU Chao, LI Cheng
2005, 20(5): 768-771.
Abstract PDF(900KB) icon2218 icon472
Abstract:
Low cycle fatigue tests and static tension tests were performed for steel 1Cr11Ni2W2MoV,with air temperature of 500℃.The difference between static elastic modulus and dynamic elastic modulus was investigated.The effects of elastic modulus on parameter of low cycle fatigue were studied also.When fatigue life is longer than 5 000 cycles,the results of fatigue life prediction showed that elastic modulus affected the precision of fatigue life prediction to a great extent,and there was large difference in scatter band.It is necessary to use elastic modulus measured in fatigue machine to predict low cycle fatigue life.
Influence of Inclusions on Crack Growth Life of Powder Metallurgy
ZHAO Yong-ming, SONG Ying-dong
2005, 20(5): 772-777.
Abstract PDF(290KB) icon1868 icon483
Abstract:
The influence of inclusion on crack Stress Intensity Factor(SIF) of Powder Metallurgy(PM) FGH 95 was investigated using singular element method with fine mesh at crack front.The effect of inclusion on crack growth life of PM was also calculated by Paris formula.The result indicates that the influence of inclusions on crack SIF of PM changes with the alteration of the inclusion's location relative to the crack.When the crack is in the range of three times of the inclusion's radius,the inclusion can affect the SIF and it will not affect on it if the crack exceeds this range.When the radius of the crack approaches the radius of the inclusion,the influence of soft inclusions on SIF is contrary to the rigid inclusions.For the crack growth life,the influence of soft inclusion is also contrary to the rigid inclusions.The crack growth life without inclusions is shorter than with soft inclusions,but it is longer than that with rigid inclusions.Because the elastic module of the inclusion is smaller than the matrix,the inclusion in FGH95 is soft inclusion and the crack growth life without inclusions is longer than that with inclusions in FGH95.The conclusion can make the analysis of the PM turbine disks life simpler.
Numerical Approach for Structure Reliability Evaluation
JIANG Xiang-hua, YANG Xiao-guang, WANG Yan-rong
2005, 20(5): 778-782.
Abstract PDF(360KB) icon1850 icon529
Abstract:
Stress-strength Integral method is the basis for structure reliability evaluation,but this method can not work properly when it is used to structure fatigue reliability estimation as the important parameter-material's equi-life strength-can hardly be obtained.A numerical approach based on the fuzzy probability integral method was studied.This method can give the structure reliability directly without the need of the equilife strength.A case study indicates that this approach is effective,and it is easy to implement and suitable for engineering applications.
Information Theory Method of Reliability Synthesis for Series-Parallel or Parallel-Series System with Hierarchical Exponential Units
SUN You-chao
2005, 20(5): 783-788.
Abstract PDF(262KB) icon1777 icon521
Abstract:
Using the hierarchical exponent test data,an information theory method for calculating approximate confidence limit of system reliability was presented.The equivalent system exponent data were obtained from the hierarchical test data based on the principle of equal information quantity.The approximate confidence limits of the system reliability were given from the equivalent system exponent data according to the principle of unit reliability assessment.The application of the method was described by way of examples.The results are very close to those of the traditional Classical and Bayes methods and show that the method is correct and valid.
Research on the Finite Element Impact-Contact Analytical Model of Dual-Rotor System and its Diagnosis Method
SHAN Ying-Chun, LIU Xiandong, HE Tian, LI Qi-han
2005, 20(5): 789-794.
Abstract PDF(707KB) icon1703 icon472
Abstract:
Considering the shortages of common rotor-stator rubbing models,using ANSYS software,a new rotor-stator rubbing model was presented based on the relationship between relative normal displacement and normal contact force.Then the rotor-stator dynamic equations were established by combining with the Whole Transfer Coefficient Method(WTCM).The dynamic characteristics were calculated by the WTCM,and then the transient responses of dual-rotor system were solved.The responses were analyzed by the time-domain curve,the Fourier transform and the wavelet transform respectively.Furthermore the fault characteristics were deduced and discussed.These results provide some reference for fault diagnosis of dual-rotor system.
MDO Technology Applied to The Aeroengine Turbine Blade Design
WU Li-qiang, YIN Ze-yong, CAI Xian-xin
2005, 20(5): 795-801.
Abstract PDF(878KB) icon2073 icon658
Abstract:
Research of Multidisciplinary Design Optimization(MDO) technology applied to the aeroengine turbine blade design was presented.The idiographic implementing process was introduced.Theory and methodology of multidisciplinary coupling optimization design taking account of aerodynamics,heat transfer,structure,vibration and life prediction and optimum algorithm,were discussed.Finally,an example was given.
Experimental Investigation on Kerosene/Air Pneumatic Valve Pulse detonation Engine
LI Jian-zhong, WANG Jia-hua, FAN Yu-xin, ZHANG Yi-ning, ZHANG Jing-zhou
2005, 20(5): 802-806.
Abstract PDF(696KB) icon1796 icon480
Abstract:
In order to investigate detonation wave charcteristics of kerosene/air pneumatic valve pulse detonation engine,a complete set of test facility was established.A lot of multi-cycle detonation experiments were carried out using a detonation tube with 100 mm inner diameter and 2000mm length,filling with heated liquid kerosene and air as detonable mixture.The detonation wave characteristics of kerosene and low polluted air as detonable mixture were investigated.This investigation is of importance to study kerosene and heavy polluted air as detonable mixture in depth and to provide theoretical and practical basis for the development of PDE's engineering application.
Numerical Simulation of Three-Dimensional Spray Combustion Flow Field by RNG k-ε Turbulent Model
GUO Shang-qun, ZHAO Jian-xing
2005, 20(5): 807-812.
Abstract PDF(850KB) icon2143 icon473
Abstract:
RNG(Renormalization Group) k-ε turbulent model was applied to the numerical simulation of the three-dimensional two-phase combustion flow field in an annular combustor.A body-fitted grid was generated by an elliptical grid generation procedure and the zone method.EBU-Arrhenius combustion model was used to determine the rate of reaction,and six-flux radiation model was used to predict the distribution of the heat flux.SIMPLE algorithm with the 3-D non-staggered grid system was employed to solve the governing equations.The liquid phase equations were solved with the particle trajectory model and the PSIC algorithm.The three-layer and two-layer wall function were applied to prediction of flow in the near wall region.Computations are in fairly good agreement with experiments.The comparison indicates that RNG k-ε turbulent model with three-layer wall function is more reliable for modeling 3-D spray combustion flow field.
Experimental Investigation on Thermally Driving Simulated Turbine Blade with Cooling Tunnels
YANG Min, CHANG Hai-ping, FANG Zhi-you
2005, 20(5): 813-817.
Abstract PDF(693KB) icon1746 icon464
Abstract:
Based on the fundamental studies of a turbine blade new cooling technique,the experimental investigation was carried out using a new experimental model with cooling tunnels in centrifugal field.The primary influence factors and heat transfer characteristics were studied.The results show that the rotational speed,density of heat fluxes and cooling air speeds significantly impact the thermally driving heat transfer effectiveness of the new cooling technique.The heat transfer effectiveness of this new cooling technique will be enhanced with the increase of the above mentioned parameters.
A Single-Cycle Performance Model of the Pulse Detonation Engine with Nozzle
QIU Hua, YAN Chuan-jun, XIONG Cha
2005, 20(5): 818-821.
Abstract PDF(731KB) icon2044 icon536
Abstract:
A performance analysis model of pulse detonation engine with convergent-divergent nozzle was established.By using detonation transmission analytical solution of characteristic method and processing method of homogeneous state of detonation chamber,the exhaust process through the nozzle after the detonation wave arriving the exit of detonation chamber or the contact face of purge gas was simplified to a fixed exhaust volume zero dimensional model.Compared with the experimental data,the model developed can be used for evaluating the engine performance trend of different nozzle sizes.Through applying some curve fitting,the model can be used for calculating the engine performance at different regimes.
Effect of Bleeding Holes on Heat Transfer Characteristics Inside U-Shaped Channel with 60° Skewed Ribs
LIU Xiang-yun, TAO Zhi, DING Shui-ting, XU Guo-qing, DENG Hong-wu
2005, 20(5): 822-826.
Abstract PDF(734KB) icon1556 icon551
Abstract:
The internal coolant channel in an actual turbine blade was simplified into a variable cross-section channel with ribs and bleeding holes.The effect of bleeding holes on the heat transfer characteristics was experimentally studied.The bleeding holes were located in the secondary pass only.Hole opening ratio was defined,and the local analysis method was applied.The effects of the hole opening ratio and the exit mass flow rate on heat transfer and the effect on the pressure distributions at the location of the bleeding holes were experimentally studied.Analysis of the results lead to the following conclusions:with the increase of the hole opening ratio,the heat transfer is enhanced while the exit mass flow rate keeps constant;the local Nusselt Numbers decrease with the increase of the exit mass flow rate while the hole opening ratio keeps unchanged.
Experimental Study of Flow Characteristics in Two-Pass Channel with Ribs and Cell Film Cooling
LIU Jun, XU Guo-qiang, DING Shui-ting, TAO Zhi, DENG Hong-wu
2005, 20(5): 827-830.
Abstract PDF(381KB) icon2073 icon615
Abstract:
Experiments have been carried out to study flow characteristics of film cooling outflow in two-pass channel.The two-pass channel of a real turbine blade was simplified.Film bleed hole are distributed along the outlet section surface.Experimental data have been analyzed by dividing the outlet section into several typical cells with rib and film cooling.Experimental results indicate that the effective pressure distribution of the outlet section changes significantly compared with no film cooling outflow and that the flow friction of the whole section decreases due to the influence of film bleeding.The outflow rate of the film bleed hole is the largest at the back of a rib.
Computational Analysis of the HP Turbine Nozzle Guide Vane Internal Flow Characteristics
GUO Wen, JI Hong-hu, CAI Yi, LIU Bo
2005, 20(5): 831-835.
Abstract PDF(273KB) icon1823 icon493
Abstract:
The temperature distribution of the nozzle guide vanes are affected greatly by the flow and heat transfer of the internal cooling passages.It is important to research the flow and heat transfer inside the nozzle guide vanes.Calculations based on network methods and experiments were carried out to investigate the complex air-cooled nozzle guide vanes internal flow and heat transfer characteristics.The results show that the mass flow,pressure and temperature distribution of the internal cooling passage can be simulated perfectly,and the calculated results are in good agreement with the experimental ones.
Numerical Investigation of the Influence Factors and Flow Characteristics for a Synthetic Jet
TAN Xiao-ming, ZHANG Jing-zhou
2005, 20(5): 836-840.
Abstract PDF(1115KB) icon1658 icon615
Abstract:
In order to obtain the characteristics of flow filed and the influence of some parameters of a synthetic jet,numerical simulations were performed in this paper.During the simulation,moving grid technique was used for modeling the periodic movement of the piezoelectric membrane so that the field of the cavity and the external flow field could be coupled computed.The flow phenomena agreed well with the experimental results.When the frequencies,diaphragms of the piezoelectric membrane and the geometrical sizes of the cavity are changed,the velocity profile of the synthetic jet changes accordingly.The results show that the simulation model is logical and the results provide theoretical foundations for the experimental parameters determination and the optimum design of the experimental parts.
Numerical Simulation of Three-Dimensional Flows in a Ramjet Combustor
YAN Shu-sheng, WANG Yu-feng, LI Gao-chun, LIU Hui, WANG Xiao-wei
2005, 20(5): 841-846.
Abstract PDF(1489KB) icon1916 icon559
Abstract:
The incompressible flow in a ramjet combustion chamber with a V flame stabilizer was numerically simulated.It was aimed at determining the flow field in the combustor through numerical simulation and give help to experiments.The calculation was performed in Cartesian co-ordinates.The finite volume method was employed to solve the N-S equations.The SIMPLE algorithm was used for the pressure-velocity coupling.The standard two equations model,the EDM model,and the P-1 model were employed as the computational models.The feature of the field was discussed;especially the effects on the flow field by the variation of different factors were discussed.The results show that the variation of different factors has important influence on flow field.
Aero-Engine Fault Diagnosis Using Neural Network Ensemble Method
XU Qi-hua, SHI Jun
2005, 20(5): 847-852.
Abstract PDF(659KB) icon1622 icon433
Abstract:
This paper developed a multiclass fault diagnosis method for aero-engine,which used three-layer perceptrons(feed-forward neural networks) as weak classifiers and then they were combined together to create an aggregate hypothesis with AdaBoost algorithm.A final fault classifier is the neural network ensemble which was formed by the simply trained three-layer perceptrons and this made it possible to design practical neural network fault classifiers easily.A simulation experiment for the gas path components of a turbojet engine was conducted to demonstrate the effectiveness of the method.Through the experiment,24 groups of fault-test data of the turbojet engine were all correctly classified into 5 classes.The experimental results show that the generalization ability of the final fault classifier is improved effectively.
Method of Restricting Aero-Engine Maximum Rotor Speed Based on Nonlinear Predictive Control
SONG Zhi-ping, Han Chong-zhao, WEI Rei-xuan
2005, 20(5): 853-856.
Abstract PDF(389KB) icon1927 icon451
Abstract:
Restricting the engine maximum rotor speed based on nonlinear forecast was studied.The dynamic process was described by the Volterra series model,and then the nonlinear close loop forecast model was established.According to the input constraints and control objective,the roll control algorithm of rotor speed forecast restriction was proposed.The simulation was carried out.The forecast restriction curve of fuel flow change versus rotor speed under the excess fuel flow during acceleration was obtained.Compared with the proportion feedback restriction,the forecast restriction can be used to avoid the affection of fuel burning delay and engine inertia,and to realize the rotor speed restriction accurately.As the volume of calculation is less,it fulfills the real time requirement.
Design of Self-Scheduled H_∞Control for Turbofan Engine
SUI Yan-feng, YU Da-ren, SUI Peng
2005, 20(5): 857-861.
Abstract PDF(770KB) icon1650 icon478
Abstract:
The LPV (Linear Parameter-Varying) system of turbofan engine was put into apolytopic expression by a convex decomposition,and the polytopic features were used to simplifythe controller design to a vertices' controller design.By using a LMI (Linear Matrix Inequality)approach,a feedback controller with the pole placement in a given region and with unique Lya-punov function for every vertex was designed, which satisfied H∞performance requirement.Aglobal continuous gain scheduled controller was then obtained by the synthesis of the vertex con-trollers.As compared with PID controller, the designed controller demonstrates its feasibility.
Multi-Variable Self-Tuning Control for Aero-Engines
PAN Mu-xuan, HUANG Jin-quan
2005, 20(5): 868-872.
Abstract PDF(1094KB) icon1643 icon412
Abstract:
Based on the least square estimation with forgetting factor μ,the multi-variable self-tuning control was proposed for aero-engines with strong nonlinearity.The control parameters were obtained from estimation directly.The closed-loop control system was identifiable through the analysis.The simulation results show that the system features the rapid response,the high precision and the ability to restrain disturbance and coupling and the estimated parameters converge quickly.
Investigation on the Theoretical Model Combined with the Novel Casting Treatmentwith Rotating Stall
YU Wei-wei, WANG Xiao-yu, SUN Xiao-feng
2005, 20(5): 873-881.
Abstract PDF(606KB) icon1843 icon427
Abstract:
The effect of a new casing treatment on the axial flow compressors rotating stall precursor wave was comprised in a three-dimensional rotating stall stability model presented in this paper.It is verified to be accurate enough in prediction of the inception of rotating stall compared with several experimental results.With the application of the equivalent surface source method,the interaction between the precursor wave and the casing treatment could be calculated.This means that there is a theoretical way to design the casing treatment.Some numerical experiments were conducted to evaluate the roles played by the structural parameters of the casing treatment.The result shows that adequate combinations of these parameters could extend the stall margin of a high-speed compressor.
Analysis and Experiments of the Tiltrotor Transient Response During Transition Flight
YANG Wei-dong, DONG Ling-hua
2005, 20(5): 882-889.
Abstract PDF(1571KB) icon1785 icon506
Abstract:
The time domain analytical model of the tiltrotor transient response during transition flight was described.Based on multi-body analysis,the equations of motion were derived.The effects of rotor wake curvature on induced velocity were considered to improve the dynamic inflow model of the tiltrotor during transition flight.The multi-body dynamic differential equations were combined with the equations of the unsteady dynamic inflow model to obtain the complete time domain unsteady coupling analytical model of the tiltrotor.Using the 2-blade teetering rotor as an example,the transient responses of the tiltrotor during transition flight were calculated.The experiment of transient rotor thrust during transition flight has been carried out on whirling beam test facility,and the experimental results show excellent agreement with theory.The experimental results and the numerical simulations demonstrate that the time domain analytical model derived in this paper has a capability of capturing the transient characteristics of tiltrotor during transition flight.The effects of wake curvature on unsteady dynamic inflow of tiltrotor are considerable and the modification to the unsteady dynamic inflow is necessary.
Nonlinear Analysis of the Process of loosing Compressor Aerodynamic Stability in a Turbojet Engine
WU Yun, LI Ying-hong, ZHANG Pu
2005, 20(5): 890-894.
Abstract PDF(757KB) icon2231 icon397
Abstract:
The process of loosing compressor aerodynamic stability in a turbojet engine was analyzed using the correlation integral method.Phase space was reconstructed based on compressor static pressure signal during throttling of the engine.Distinct change among attractor structure of the reconstructed phase space was observed and corresponding correlation integral values were calculated to quantify the change of the compressor internal flow.It showed that the tip region of 1st stage lose its stability first,and then 2nd stage,followed by 3rd and 4th stages during throttling.1st and 2nd stages manifested progressive stall while 3rd and 4th stages manifested abrupt stall.Instability symptom was first detected in the root region of 3rd stage,which developed rapidly and led to full-span stall.Low-pass filtering can improve the effectiveness of correlation integral method in stall precursor detection.Thus,nonlinear correlation integral method is an effective means in the investigation of the process of loosing compressor aerodynamic stability.
Experimental Investigation on Multiple Pipe Detonation Wave Ignition
GUO Hong-jie, LIANG Guo-zhu, MA Bin
2005, 20(5): 895-899.
Abstract PDF(821KB) icon1880 icon451
Abstract:
To investigate the synchronization characteristics,reduplication characteristics and torch characteristics of detonation wave multiple-unit ignition technique of the liquid rocket engine,the experimental apparatus has been set up.Gas hydrogen and gas oxygen were used as working substance.Many experiments were carried out under normal temperature and 0.1～0.5 MPa gauge pressure conditions and with the mixture ratio of 1.8～7.2.The results show that the detonation wave ignition technique can provide high temperature(>1 300℃) and high pressure(>1 MPa) with low supply gas pressure which accommodates to the vapor pressure in fuel tanks of the liquid rocket engine.It has excellent synchronization and reduplication characteristics and the synchronization errors of both reduplication and multi-unit ignition are less than 0.3 ms.The detonation wave ignition technique is suitable to synchronization ignition of multi-chamber liquid rocket engine.
Noise Characteristics Analysis of Aero-Engine Testing Signals
LI Wen-feng, WANG Yong-sheng, YANG Ji-ming, WANG Su
2005, 20(5): 900-904.
Abstract PDF(907KB) icon2072 icon504
Abstract:
The acquired data of aero-engine are somewhat contaminated with noise or disturbances.Different methods of noise separation such as the spectrum analysis,filtering,wavelet decomposition,bi-spectrum and auto-correlation analysis were discussed.Besides,the types and characteristics of noise radiated from the engine were analyzed.The results show that the engine noise is additive weak-intensity continuous spectrum or compound spectrum and for some frequencies it is both continuous and linear.The noise contains not only internal complex white noise but also non-stationary variance intrusion colored noise.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.