1992 Vol. 7, No. 2

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EXPERIMENTAL INVESTIGATION ON BLADE LOSS TRANSIENT RESPONSE OF ROTOR WITH FLEXIBLE DAMPED SUPPORT
Li Qihan, Zhao Fuan, Zhang Shiping
1992, 7(2): 103-107,191.
Abstract PDF(356KB) icon1795 icon494
Abstract:
A rotor system with flexible damped support has been investigated experimentally under the conditions of simulated blade loss.Some results of the transient response dynamics are presented.Experiments under different sudden unbalances applied to the rotor system with various Squeeze Film Damper (SFD) film clearances were performed at different rotational speeds.The instability conditions characterized by limiting circle orbits for large amplitude at damper location can be determined,and some particular phenomena caused by nonlinearity of the rotor system such as lock up,bistable jump and subharmonic etc.have been observed.The effectiveness and the capability of SFD for suppressing instability of the rotor system are analyzed.
LIFE PREDICTION OF A MEMBER UNDER LOW-CYCLE FATIGUE CREEP INTERACTION
Xu Linyao
1992, 7(2): 108-112,191.
Abstract PDF(332KB) icon1655 icon409
Abstract:
A structural member model under low cycle fatigue creep interaction has been investigated experimentally and its life predicted with the help of several available methods.On the basis of the comparison between the expermental data and the prediction results,an approach is provided to analyze the cycle creep and influence of average stress according to difference between the properties of the material and the member.The rule of the low cycle fatigue creep interaction has been researched thoroughly.Finally,a better approach of life prediction is proposed.
PHASE MODULATING IN ESPI FOR VIBRATION PATTERN MEASUREMENT
Dong Benhan, Qiu Daming, Gao Penfei
1992, 7(2): 113-116,191-192.
Abstract PDF(365KB) icon1817 icon427
Abstract:
The conventional method of electronic speckle pattern interferometry (ESPI) for vibration pattern measurement is to freeze reference beam.This method enables to sweep over a wide frequence range and to identify resonant modes.However,the obtained fringe contrast is not too fine.In order to eNhance the visibility of fringe pattern,it is possible to subtract two time average pattern at any given frequancy.In result,the fringe pattern is obtained with high visibility but only valid at the given frequency.A phase shifting technique is adopted to overcome this shortcoming.A time average image is put into processor and frame store(renewed and put into processor per 40ms),then a subsequent image with a phase shift of ΔΦ resulted from sinusoidal modulation in object beam is recorded and subtracted from the first image.This method is similar to modulation of light intensity function of speckle pattern.The advantage of this method is the capabilities of obtaining real time fringe pattern of vibration with high resolution and of performing frequency scanning at a wide range.Its application to the vibration pattern measurement of disk blade coupling in an aeroengine is a great success.
ANALYSIS OF TENON AND MORTISE CONTACT PROBLEMS BY BOUNDARY ELEMENT METHODS
Wen Weidong, Gao Deping
1992, 7(2): 117-120,192.
Abstract PDF(295KB) icon1751 icon410
Abstract:
The boundary element equations of 2 D elastic contact problems are established by the incremental principle and some concrete approaches to solution of the contact procedure are considered.The contact stresses of the dove tail and the pine tree joints of the disk/blade assembly are numerically analyzed.From the comparsion of the numerical results of boundary element methods(BEM)with those of FEM and photoelasticity experiments it is concluded that the results of BEM are satisfactory in contrast with FEM,the BEM not only simplifies data preparation but also gives the results of the same accuracy level with fewer discrete elements and saves the computer time tremendously.
A COMPOUND FATIGUE INVESTIGATION OF PLATE SPECIMEN UNDER LOW-CYCLE LOAD SUPERPOSED ON HIGH CYCLE LOAD
Xu Fengjing, Nie Jingxu, Zhao Changzhan
1992, 7(2): 121-124,192.
Abstract PDF(281KB) icon1718 icon491
Abstract:
According to real operating conditions of turbine engine blades in service,a series of combination tests of various load matching and frequency matching for plate specimens was carried out on the compound fatigue testing rig which can simulate operating loads on the blades.From the test results and theoretical analyses,some characteristics and the regularities of this compound fatigue are obtained.A new method of life prediction for this compound fatigue is presented in this paper.The calculated results of this method are in good agreement with the experiments.
RESEARCH ON DAMAGE TOLERANCE OF COMPRESSOR BLADE
Zheng Guanghua, Yu Juanhong, Hou Guichang
1992, 7(2): 125-128,192-193.
Abstract PDF(1093KB) icon1845 icon524
Abstract:
This paper discribes the damage tolerance analysis of compressor blade by fracture mechanics.Finite element method with 20 nodes solid elements is used for the stress calculation.A displacement method is provided to determine the stress intensity factors K Ⅰ,K Ⅱ and K Ⅲ versus crack length a of the blade.Based on the material toughness K ⅠC ,additional extension δ c and deviation of natural frequency f c of the cracked blade,the failure criterion of the compressor blade is discussed and the critical crack length is determined.By the use of Pris formula and in consideration of the influence of high cycles on low cycle fatigue crack propagation,the damage tolerance life of the blade is obtained.As an example,a calculation of a certain compressor blade is given.In order to investigate the relation of natural frequency versus crack length,the vibration of compressor blades has been tested.The presented method can be used for the strength evaluation of turbo jet engine.
FINITE ELEMENT ANALYSIS OF COMPLEX DISK BODY WITH ECCENTRIC HOLE
Peng Kejian, Sheng Yuansheng
1992, 7(2): 129-130,193.
Abstract PDF(207KB) icon1452 icon382
Abstract:
A strategy of discretization process for the 3 D disk body of complex cross section has been developed on the basis of available functions of I DEAS system.The cutting and mending techniques are employed to realize the mesh formation at the local regions of eccentric holes.In result,it is possible to solve effectively the contradiction between element distortion and over large scale of solution,and thus the 3 D analysis of the disk with eccentric hole can be completed at one time.Also in this paper an engineering optimum method is provided by adjusting the thickness of the disk so as to control the stress level at the edge of holes.
HOLOGRAPHIC VIBRATION MEASUREMENT OF DISC-BLADE COUPLING IN HIGH-SPEED ROTATION
Wu Qiufang, Jiang Guoliang, Zhao Kaining
1992, 7(2): 131-134,193.
Abstract PDF(303KB) icon1624 icon542
Abstract:
A new measuring technique is presented which combines holographic interferometry and image derotation to determine the behaviour of disc blade coupling vibration during high speed rotation.The measuring technique and its optical system have been verified by the test of a model circular disc.The primary test results of a real disc blade coupling are given which show the obtained holograms of rotating members to correspond to the results of vibration theory analysis and frequency spectrograms.Therefore,it is possible to expect this technique to be an effective testing measure for aeroengine designing and troubleshooting.
RESEARCH ON HIGH-LOW CYCLE COMPLEX FATIGUE AND ACCUMULATIVE DAMAGE FOR Ti-ALLOY TC11
Hou Jingyou
1992, 7(2): 135-138,193-194.
Abstract PDF(354KB) icon2198 icon469
Abstract:
The high low cycle complex fatigue behaviours of Ti alloy TC11 were researched systematically at room and elevated temperatures.At the same time,the effects of complex stress ratio m ,test temperature and prestress overload for SEN specimen on complex fatigue life N fL were taken into consideration.The work comes to the conclusion that:The complex fatigue life decreases obviously with m increased,especially when m =35%,the Nfl decreases more than 10 times,and there occurs a knee on the m —log NfL curve near m =10%.The complex fatigue of the alloy TC11 is very sensitive to test temperature under the same m ratio and LCF stress,as test temperature rises from room temperature to 150℃,the complex fatigue life NfL drops by 66% under m =10% and σ max =945MPa.If the temperature comes up continuously to 300℃,its fatigue life approaches to zero.In addition,a model of the accumulative damage for complex cyclic fatigue is formulated as follows: 1/NfL =1/N L+n/Nf .
A REAL-TIME RAIN-FLOW METHOD OF CYCLE COUNTING AND ITS PROGRAM DESIGN FOR AEROENGINE SERVICE LOADS
Li Yongxin, Sui Hai
1992, 7(2): 139-143,194.
Abstract PDF(325KB) icon1491 icon502
Abstract:
The paper presents briefly a real time rain flow method of cycle counting and its program design for the service loads of aeroengines.The concept of real time counting and its value to engineering application are also discussed.A detailed program flow chart is given which can be used in software programming of small size airborne data processing equipment.
EXPERIMENTAL RESEARCH ON BLADE CONTAINMENT
Gong Mengxian, Wang Lü Sheng, Cao Fenglan
1992, 7(2): 144-146,194.
Abstract PDF(258KB) icon1792 icon486
Abstract:
This paper describes the blade containment tests for six sets of single model blade on a vertical breaking down tester with excess revolution.The experimental results indicate that the blade body fragment flying off impacts against the model aeroengine case time and again.The incident angle of the blade fragment against the case in the initial impact is smaller than in the later impacts,the case damage of the first impact is smaller than that of the final impact,and the impacts of the blade fragment against the case make the blade fragment crimple.In principle the experimental results of the blade fragment containment and non containment are consistent with the containment curve of single compressor blade (for use only in case of the blade body) in the Spey MK202 Stressing Standards (EGD 3) and are on the safe side.It is the preliminary conclusion that the containment curve of single compressor blade (for use only in case of the blade body) in EGD 3 can be used to predict the containment of the similar blade.
THE LOW-CYCLE-FATIGUE LIFE PREDICTION OF A MEMBER WITH HOLES
Rao Shouqi, Mao Yingyong
1992, 7(2): 147-149,194.
Abstract PDF(308KB) icon1330 icon457
Abstract:
The stress and strain field and the low cycle fatigue life of a structure member with holes are calculated theoretically and investigated experimentally.The calculated results show that it is reliable to calculate the stress and strain field of a member with holes by using the shell structural elasto plastic finite element program,which has been designed and developed by the author.The satisfactory results are obtained from LCF life prediction of a member with holes by the advanced local stress and strain method.The calculation and tests show that the stress concentration of the tensile plane member is intensified and the fatigue life reduces drastically when its holes are densified in the direction perpendicular to that of tensile;the stress concentration is mitigated slightly but the fatigue life is also shortened when they are densified in the tensile direction.
FATIGUE STRENGTH RESEARCH OF DZ-22 SUPERALLOY UNDER COMPLEX STRESS CONDITION
Yue Yanfang, Rao Shouqii
1992, 7(2): 150-152,195.
Abstract PDF(247KB) icon1299 icon492
Abstract:
Criteria for calculating low cycle fatigue strength of DZ22 superalloy under complex stress condition are considered.The fatigue life of the material under complex stresses can be predicted according to the criteria,provided its straight axial strengths and any straight axial S—N curve are available.For DZ22 as a kind of directionally solidified high temperature alloy,the low cycle fatigue comparative tests have been made between the uniaxial tension compression and tension torsion at 850℃ and show that the results of tests and calculations are in good agreement.
LIFE PREDICTION OF LOCAL STRESS-STRAIN METHOD
Liu Xangsheng
1992, 7(2): 153-155,195.
Abstract PDF(732KB) icon1527 icon433
Abstract:
The local stress strain method is applied to LCF life prediction.The method and procedure for determining reliability life and flight life are provided.The influence of the variable amplitude cycle loading on the lives and effects of the fluctuation of material fatigue constants on the lives are considered.In addition the present method is compared with the EGD 3 method.
A FIBRE-OPTIC AMPLITUDE MONITOR FOR BLADE VIBRATION
Deng Yong, Sheng Xizhi, Xue Xiusheng
1992, 7(2): 156-158,195.
Abstract PDF(254KB) icon1506 icon397
Abstract:
The fibre optic amplitude monitor is developed by our institute as a non contact vibration measuring system for rotator blades,in which a magnetic needle is adopted as a one per rotation sensor and a fibre optical cable as a blade passing sensor.Multiple application of the present monitor in development of new type engines demonstrates reliability and convenience in operation.It features high temperature resistance,it can work up to 350℃ and up to 400℃ in the near future.This monitor has been put in service as a main instrumentation to monitor the blade vibration in the high pressure compressor of our new type engine during its development.
ROTOR EXIT FLOW MEASUREMENTS IN A HIGH-SPEED MULTISTAGE FAN
Jiang Haokang, Li Yuchun, Zhao Quanchun, Xu Qixing
1992, 7(2): 159-163,196.
Abstract PDF(340KB) icon1860 icon431
Abstract:
A single hole cylindrical high frequency response pressure probe characterized by high frequency,small size,high accuracy and reliability has been developed for rotor flow measurements in a high speed multistage fan.With the help of a two axes traverse mechanism and a high speed data acquisition and processing system,the periodic two dimensional flow field at the exit of the third rotor of the fan has been successfully measured by using an on line calibration technique to determine the pressure sensitivity and null pressure reading (zero offset) during the compressor measurements.The results with the high accuracy and fine resolution provide an important basis for redesign of the third stage.Furthermore,the probe,measuring method and data reduction procedure are proved simple,precise,practical and reliable.
A METHOD FOR MEASURING HIGH-SUBSONIC TWO-DIMENSIONAL PERIODIC FLOW FIELD USING A SINGLE-HOLE HIGH-RESPONSE CYLINDRICAL PRESSURE PROBE
Li Yuchun, Jiang Haokang
1992, 7(2): 164-166,196.
Abstract PDF(243KB) icon1386 icon585
Abstract:
This paper presents in detail a method for measuring high subsonic two dimensional periodic flow field with a single hole cylindrical pressure probe with high frequency response.The method normalizes the probe calibration curves at different Mach number and simplifies the compressibility correction.The probe is set in nine azimuthal angles while measuring the flow.Sampled and averaged data are used to determine flow angles by least square fitting, Mach number and stagnation pressure are then obtained from solving a set of non linear equations.The method has been successfully applied to measuring the rotor exit flow field in a multistage compressor with high accuracy.
APPLICATION LDA TO INVESTIGATION OF 3-D VELOCITY PATTERN IN INLET DISTORTION SIMULATOR
Lin Qixun, Zhang Li, Zhang Dong, Shi Chunying
1992, 7(2): 167-168,196-197.
Abstract PDF(256KB) icon1421 icon415
Abstract:
A two measurement at one point method with a two colour LDA(Laser Doppler Anemometer)has been used for measuring three dimensional velocity field.Various velocity distortions of the simulator have been investigated.The velocity and turbulence patterns of 90 degree torus quadrant and of torus with 20 degree slanted cut are shown.It can be seen clearly how the low velocity and large turbulence region will be caused by the flow separation from the duct lips.In order to estimate maximum instantaneous distortion,the vortex size must be measured.It is defined classically by velocity crelation and more directly than by total pressure.Some typical results are shown in a table.The vortex size is increased by the flow velocity.At 1D section the vortex size of torus with 20 degree slanted cut is about two times larger than the size of 90 degree torus quadrant.But at 3D section the former decreases and the later increases slightly.
EXERGY ANALYSIS OF AEROENGINE AND ITS SIGNIFICANCE
Li Ruhui, Qiu Xiaomei
1992, 7(2): 169-172,197.
Abstract PDF(329KB) icon1595 icon486
Abstract:
An exergy analysis method of an aeroengine is presented and compared with the traditional energy analysis method.The significance of the exergy analysis for the aeroengine engineering is considered.It must be underlined that the main part of the energy loss in the aeroengine comes out of the combustor.Therefore,to eNhance of the exergy efficiency of the combustor is an essential measure to improve aeroengine performance.
STATISICAL ANALYSIS AND PREDICTION OF AEROENGINE DETERIORATION
Li Jia, Tao Zengyuan
1992, 7(2): 173-176,197.
Abstract PDF(784KB) icon1774 icon413
Abstract:
An aeroengine deteriorates in the course of its service.Although its perfomance may be restored to some extent after overhaul,it goes down gradually in general.Based on the statistical information analysis of the test bed performance decay of 500 engines after 0 to 3 overhauls,a concept of an overall performance index is proposed to reflect the overall performance of the engine.According to this concept,a mathematical model of the engine deterioration is presented which is established by means of the exponential smoothing theory.The prediction of the engine deterioration has been made whcih is quite consistent with the practice.The final analysis shows that it is necessary and also feasible to adopt the method of statistical and synthetic analysis for the overall engine performance decay of both randomness and regularity and,what is more,with many parameters.
A DIRECT-PROBLEM CALCULATION METHOD FOR GAS TURBINES WITH BOWED AND TWISTED BLADES
Wang Zhongqi, Yang Hong, Liu Fengjun, Huang Yinghong, Feng Guotai
1992, 7(2): 177-180,197-198.
Abstract PDF(360KB) icon1458 icon517
Abstract:
The necessity of the direct problem calculation in aerodynamic design of gas turbines with bowed and twisted blades is discussed and a practical direct problem calculation program is developed for the S 2 stream surface transonic flow in a multi stage gas turbine.In the calculation,the shape of the mean S 2 stream surface is taken as that of the blade mean camber surface which is modified properly to guarantee a reasonable S 2 stream surface shape,and the circulation is specified by the stream surface shape and the axial velocity.In the supersonic region,the density is corrected by means of the artificial compressibility treatment to make the calculation stable and the velocity is solved by density.This calculating method is applied to modification of a gas turbine.Meanwhile,the effects of different blade bowing methods on the radial distribution of gas parameters are analyzed.The calculation results demonstrate the improvement on the flow pattern in the turbine cascade with bowed and twisted blades and the necessity of the proof calculation with the direct problem method.Finally,several instructive opinions about the aerodynamic design of the bowed and twisted turbine blades are proposed.
A CIRCUMFERENTIAL NON-UNIFORM EFFECT MODEL FOR MULTISTAGE AXIAL-FLOW COMPRESSOR THROUGHFLOW
Li Shiming, Chen Maozhang
1992, 7(2): 181-185,198.
Abstract PDF(912KB) icon1798 icon496
Abstract:
The effects of momentum and energy transportation caused by circumferential non uniformities of the flow in a multistage axial compressor are studied.A model has been developed to represent the circumferential non uniform stresses and heat flux.A preliminary comparison between experimental results and the model demonstrates that this model is feasible.This study comes to the conclusions that:1.The momentum transport effects of circumferential non uniformities are not distinct,but the energy transport effects of the non uniformities are quite strong and have the same order of magnitude as the turbulent diffusion;2.The relative importances of the turbulent diffusion and the non uniformities depend on compressor configuration,loadings and spanwise positions in the compressor;3.Compared with the effects of their main stream counterparts,the circumferential non uniform stresses can be sometimes neglected,according to the compressor loadings,configuration and the calculation tolerences as well.
VIBRATION OF GEAR SYSTEM WITH WEB STRUCTURE
Fang Zongde, He Dawei, Shen Yunwen
1992, 7(2): 186-189,198.
Abstract PDF(348KB) icon1746 icon497
Abstract:
The web structure has been widely used in design of aviation gears,and its structure vibration has attracted much attention.But the function of web as a torsion spring in the dynamic behaviour of gear system needs a thorough investigation still.In this paper,a typical gear transmission is taken for example,its dynamic model has been built up to analyze the vibration mode of the system.The dynamic responses of this system at various speeds have been obtained with Fourier method by considering the transmission error of the pair of gears as excitation.Further,the influences of web flexibility and attached damping on the dynamic responses have been studied,the dynamic loads on the teeth when the web thickness is changed,and the damping,both attached and unattached,have been calculated respectively.Some useful conclusions have been drawn which show that the combination of flexible web and attached damping can lower the vibration level and decrease the dynamic loads obviously.

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