1987 Vol. 2, No. 3

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SOME PROBLEMS IN RESEARCH OF ROTOR DYNAMICS
Gu Jialiu
1987, 2(3): 193-198,379.
Abstract PDF(661KB) icon1710 icon427
Abstract:
This paper elaborates the state-of-arts of studies on some problems in rotor dynamics, which are as follows, l.some special vibration behaviours caused by the rolling bearings; 2.aero-elastic forces produced in the labyrinth seals; 3. vibrationmechanisms of the mistuned bladed disk; 4.mechanisms of the SFD; 5.vibration monitoring of the cracked shafts; 6.flutter whirling of the propeller rotor system.Some opinions of the author about these problems are stated, such as improving the model of a mistuned bladed disk may be one of the most important measures to gain the confident results of research on this subject, some aspects must be taken seriously in research of monitoring the cracked shafts,etc.
AUTOMATIC CONTROL OF VIBRATION OF A FLEXIBLE ROTOR WITH MICROCOMPUTER
Feng Guanping, Xin Nuan
1987, 2(3): 199-203,279.
Abstract PDF(483KB) icon1663 icon414
Abstract:
A combined theoretical and experimental study shows that it is possible to controlthe vibration of a flexible rotor by varying the support stiffness. The over-all rotor support stiffness can be tended to enable the rotor critical speed to shift desirably and to make good matching between the rotor and the support.A new construction of the pedestal with changeable stiffness is presened. Its stiffness can be changed continuously by changing the oil pressure which is exestedon the support by a special hydraulic system. A method for calculation of the pedestal stiffness is introduced. A microcomputer is used to control the vibrationof the flexible rotor according to the vibration signal of eddy current sensors.The controlling program uses the step approximation method. The results of the experiments are also given in this paper.
STUDY ON ROTOR VIBRATION ABSORBER WITH SQUEEZE FILM DAMPERS
Zhang Shiping, Liu Fanjie, Yan Litan
1987, 2(3): 204-208,280.
Abstract PDF(481KB) icon1736 icon399
Abstract:
A type of Rotor Vibration Absorber(RVA) used in parallel with Squeeze Film Dampers(SFD)is presented. The RVA is a symmetric ring with an elastic coupling mounted in a certain place of the rotor. One or more RVA may be applied to a rotor. The RVA may be mounted in a suitable place on the rotor to gain desira-bla vibration control and to attenuate the amplitude of the rotor system far away from the supporting position. The amplitude and transmissibility of the rotor can be greatly reduced in the working speed range. The introduction of the RVA to rotor-SFD system will greatly enhance the ability of the system to subject the impact unbalance loading and increase the stability of the rotor system.Both the steady-state and transient responses of the rotor system with the RVA have been analyzed. The primary experiments of the system have also been performed, which verify the effectiveness of the rotor vibration absorber.
MODE SYNTHESIS ANALYSIS OF VIBRATION CHARACTERISTICS OF ENTIRE ENGINE
Ou Yuanxia, Li Ping
1987, 2(3): 209-214,280-281.
Abstract PDF(611KB) icon2332 icon413
Abstract:
The mode synthesis is combined with the finite element method to analyze the vibration characteristics of the rotor-bearing-case system of an engine. The generalized state space mode synthesis method is adopted to calculate the coupling vibration characteristics between the axisymmetrical rotor and the case, and the complex mode synthesis method is applied to calculating those between the non-axisymmetrical rotor and the case. The finite element method is used to analyze the substructures.A program, named AROBEC, has been written for this purpose. It can calculatethe whirl frequence, critical speed, stability, unbalance response and transientresponse for engine system. The program includes preprocessing and postprocessingfunctions and provides conical shell finite elements and rotor finite elementswith viscous damping which take shear effect into account. The dynamic characteristics of three types of aeroengine have been analyzed with this program and the results are satisfactory.
A CALCULATION OF A ROTOR INTEGRAL STRENGTH WITH FINITE ELEMENT METHOD FOR FLEXIBILITY
Sheng Huiyu, Sun Botao, Li Fei, Niu Xiuyun
1987, 2(3): 215-218,281.
Abstract PDF(430KB) icon1541 icon422
Abstract:
A calculation method is presented to determine the integral strength of a complexrotor with both radial interference and axial pretension. The method is characterized by followings.calculating the flexibilities and free deformations at the connection nodal points of rotor substructures with finite element method at first; determining the inner forces at these points then; obtaining the deformations and stresses of the individual rotor substructures at last. The method is verified by using a conventional finite element method for a modal stage in good agreement. The present method has been applied to the final design of a disk-drum detachablerotor with bidirectional interferences, which consists of profile wheels, annulus spacers and conical shafts. The rotor is designed for a six-stage compressorand is divided into 2504 annular elements of triangular type by 2020 nodal points. The rotor integral strength calculation is performed on a small computer of only 16K memories. The rotor deformation and iso-stress line diagramsare drawn by computer. The mechanical relationship of the rotor with its individual parts is quite clear.
INVESTIGATION ON BLADE FORCE DEFECT IN END WALL BOUNDARY LAYER FOR MULTISTAGE AXIAL COMPRESSOR
Liu Songling
1987, 2(3): 219-224,281-282.
Abstract PDF(562KB) icon1721 icon417
Abstract:
In order to predict the blade force defect a new model is proposed which is based on the analysis of the deflection of the blade force in boundary layer due to the secondary flows in cascade both with and without tip clearance. It is assumedthat the scalar product of blade force defect and mainstream velocity is proportionalto the work done by the cascade secondary flow drag and can be expressedas equation(16) in the present paper. This equation approaches to the relationsuggested by Mellor et al. as the lift coefficient value of the blade is very low. A method using the values of blade force defect in boundary layer is pre- sented to estimate the compressor efficiency. The end wall boundary layer thicknessesare calculated and the blockage in meridional plane is obtained for two axial compressors and an inlet guide vane. The efficiency of a compressor is also estimated. The analysis indicates that reasonable results can be obtained by the use of this method.
SECONDARY FLOW LOSSES IN PLANE TURBINE CASCADES AND ITS MATHEMATICAL PREDICTION MODEL
Li Caixiu, Ni Zhong
1987, 2(3): 230-234,282.
Abstract PDF(417KB) icon1385 icon454
Abstract:
The phenomenon and cause of the secondary flow in plane turbine cascades are discussed and a mathematical prediction model of losses is presented. It is stressed that the secondary flow in turbine cascades is a dynamic but not a kinematiceffect and thus should be studied from the viewpoint of dynamics. Based on the results of plane cascade tests, a model that predicts the secondary flow loss distribution is suggested. The effect of inlet boundary layer has been consideredin the model. Precision obtained from the proposed model conforms more satisfactorily with experimental results than those given in previous literatures.
A STUDY ON DEPLOYMENT RULE OF SINGLE EXTENDIBLE EXIT CONE BY MASSCENTER MOVEMENT THEOREM
Ma Guobao
1987, 2(3): 235-238,283.
Abstract PDF(493KB) icon1617 icon391
Abstract:
The deployment rule of the single extendible exit cone is investigated in this paper. The cone is divided into four pieces in the direction of meridian. As a result, the actuators are just located in the middle of each piece. Each piece of the cone can thus be simplified into a moving mechanism. Based on the force balance between the mechanisms, a second ordes ordinary differential equation is derived by applying the mass center movement theorem. The numerical solutionof the equation can be obtained by means of the fourth order Runge-Kutte method. The time-dependent parameters, such as position, velocity and accelerationof the external sleeve of the actuator relative to the internal tube, and the time needed for fully deploying the cone can then be obtained by using other related equations.
A DESIGN METHOD FOR LENGTH OF CYLINDRICAL SEGMENT IN A THROTTLING CAVITATION VENTURI THROAT
Gao Hanru, Chen Qizhi
1987, 2(3): 239-242,283.
Abstract PDF(434KB) icon2545 icon485
Abstract:
A throttling cavitation venturi is one of the key components of the space variable-thrust liquid rocket engine. In order to reduce its pressure loss and improve its pressure recovery characteristics, a cylindrical segment is designed to be inserted in the venturi throat.Based on the experimental results obtained from the cold flow tests, the empiricalformula is proposed for the pressure recovery characteristics of the throttlingcavitation venturi. Through the theoretical analysis, the procedure for designingthe length of the cylindrical segment in the range studied and the availableinterval for choosing are presented. The analytical expression for the functionof venturi taper stroke H versus stroke difference Φ, maximum relativeerror ξ and throttling ratio E is derived. With the aid of correction factor λ, the value of the cylindrical segment length for ξ≠0 can be calculated from that for ξ = 0. The related graphics are also given. It is found that the throttling ratio E has a pronounced effect on the determination of the cylindrical segment length.
EXPERIMENTAL STUDY ON ATOMIZATION OF PLAIN JET INJECTOR IN HIGH PRESSURE CO-AXIAL AIRFLOW
Yang Guixian, jin Rushan
1987, 2(3): 243-245,284.
Abstract PDF(445KB) icon1610 icon381
Abstract:
An experimental study has been carried out on the effect of high ambient air pressure on the spray characteristics of a plain jet injector in coaxial high velocity airflow. The air pressures tested range from 1 to 16 atm, the airflow velocity from 60 to 120rn/s and the pressure drops of the injector tested from 0.2 to 2 MPa, Working fluid is water. The key feature of the experiment is to use a convergent-disvergent nozzle to maintain a high air pressure in the test chamber and at the same time to maintain a high airflow velocity in the atomi-zation zone. It totally eliminates the air recirculation and problem of slow droplet settling in a commonly used pressurized vessel for high pressure atomization. The results show that SMD decreases monotonuously with the increase of ambient air pressure, and at different air velocities the effect of the air pressure is different.The drop size distribution parameter N in Rasin-Rammler distribution decreasesslightly with the increase of ambient air pressure.
DISCUSSION ON DYNAMIC CHARACTERISTICS OF A ROTOR WITH CHANGEABLE SUPPORT STIFFNESS
Yan Litang
1987, 2(3): 246-248,284.
Abstract PDF(335KB) icon1657 icon394
Abstract:
In this paper the author identifies that the rotor system will be nonlinear provided the support stiffness varies at ? with the amplitude unchanged and no external load is added to the support (it is difficult to add rotating load to it). Its amplitude-frequency curve must be obtained in accordance with the nonlinearvibration theorem. Although the maximum amplitude of the rotor system with nonlinear support stiffness may be decreased, it never follows the curve of solid line in Fig.l as the addition of two curves with different linear support stiffness. In order to demonstrate this argument, a brief analysis of the vibrationcharacteristics of a nonlinear rotor system is completed and its amplitude-frequencycurve is plotted in Fig.4.
AN OPTIMAL DYNAMIC DESIGN OF AEROENGINE ROTORS WITH FREQUENCY CONSTRAINTS
Teng Xiaolei, Teng Hongfei, Zhang Lianxiang
1987, 2(3): 249-251,285.
Abstract PDF(331KB) icon1459 icon389
Abstract:
The present paper deals with the following optimization, given the structural natural frequency constraint and certain constraints on the design variables, findingout the minimum weight of the rotor consistent with the above constraints. By using the method of mathematical programming combined with the perturbationconverse solution, this problem can be solved. The combined method reduces times of re-analyses, and is simple and easy to understand. A practical example of dynamic design of an aeroengine rotor is given. The results may be useful to the practical engineering.
EXPERIMENTAL INVESTIGATION ON HEATING CHOKE AND COMBUSTION INSTABILITY
Ji Heming, Zhang Xiaoxian, Liu Fengxian, Wang Hungzhuo
1987, 2(3): 255-254,285.
Abstract PDF(367KB) icon1899 icon466
Abstract:
A phenomenon of combustion instability with frequency 106Hz was found in afterburner of a turbofan engine at testbed. The traditional approaches for excludingcombustion instability, such as resigning damping inner liner, changing fuel concentration distribution, appeared ineffective. Theoretical analysis and experimentalinvestigstion show that this combustion instability is a kind of heating choke due to aerodynamics of internal flow. This heating choke leads up to instableburning in overall afterburner. The conditions of emergence of this combustioninstability and approaches to eliminate it are elaborated in accordance with various test results.
NUMERICAL METHOD FOR CALCULATING WALL TEMPERATURE OF FLAME TUBE WITH FILM COOLING
Zhu Changqing, Dong Zhirui
1987, 2(3): 258-260,286.
Abstract PDF(369KB) icon1934 icon407
Abstract:
This paper deals with a numerical method for calculating the wall temperature profile of turbo-jet flame tube with film cooling. The following factors affecting the accuracy of the calculation are considered: the longitudinal heat conduction in flame tube wall; the heat conduction at the interface of the film-cooled section with the corrugated strap; the convective heat transfer on two end surfaces of the film-cooled section; the temperature rise of cooling air in the annular cooling passage; the effects of temperature on physical propertres. A sample computation using this numerical technique is performed for calculating the temperature profile of the corrugated film-c.ooled sections of spey-25 flametubes. Owing to improvement of the calculation method, the obtained temperature profile agrees quite well with the experimental one.
PROBLEM OF FILTER POSITION IN THE PREDICTION OF MAXIMUM INSTANTANEOUS DISTORTION
Liang Dewang, Zhang Shiying
1987, 2(3): 258-260,286.
Abstract PDF(310KB) icon1510 icon415
Abstract:
Fluctuating pressure filtering in Motycka method of predicting maximum instantanneous distortion is modified by instantaneous distortion filtering. Comparisonand analysis of the statistical properties of the instantaneous distortion and its maximum value with different filtering position are carried out. Relationships between the results obtained by the mentioned methods are established. It is shown that fluctuating pressure filtering in Motycka method can be modified by instantaneous distortion filtering to predict the maximum instantaneous distortion values and computing time can be greatly reduced.
EXPERIMENTAL INVESTIGATION ON TEMPERATURE FIELDS IN THREE-DIMENSIONAL SWIRLING COMBUSTOR
Zhu Hulling, Tang Ming, Yan Chuanjun
1987, 2(3): 261-263,286-287.
Abstract PDF(345KB) icon1780 icon392
Abstract:
This paper introduces the experimental results of temperature fields in a modelcombustor with a swirler and primary holes. Acetylene is used as gaseous fuel. Under several steady conditions the temperature distributions in primary combustionzone are measured by a pyrometer. The experimental results reveal the effectsof air-fuel ratio, primary holes and secondary holes on the temperature distributionsin the combustor.
AN IMPROVED METHOD FOR PREDICTION OF MAXIMUM TOTAL PRESSURE DISTORTION
Liu Sheng, Bao Yun, Chen Fuqun
1987, 2(3): 261-263,286-287.
Abstract PDF(393KB) icon1273 icon376
Abstract:
Jacocks' method has been improved by deriving a difference correction matrix of second derivatives for Gauss-Newton iteration method. The numerical tests justify that the improved method enables the calculation to converge more rapidly and reduces the CPU time. The combination of the distortion prediction described in reference[4] with Jacocks' method avoids the necessity of experimental extreme values as input data for the Jacocks' method. The comparison of the distortion prediction results with the experimental data demonstrates better agreement.
APPLIED PROGRAM OF IDENTIFYING TRANSFER FUNCTION
Tang Runxin, Li Ping
1987, 2(3): 264-266,287.
Abstract PDF(316KB) icon1356 icon376
Abstract:
The algorithm and the computer program TFIP used to identify the transfer function models from experimental freguency response data are presented. It is also considered how the selection of the model orders, the selections of the equationerror and real error tolerance, and the modes for updating weight coefficientsaffect the convergent speed and identification results. The new term rejectioncriterion and the method for updating weight coefficients by variable mode are proposed, the former can simplify the program, and the latter may greatly accelerate the convergence of the weight coefficients.
A SCHEME OF CONDITION MONITORING AND MAIN FAULTS DIAGNOSING SYSTEM FOR A TURBOJET ENGINE
Zhou Zongcai, Li Yinghong, Wang Zengyi
1987, 2(3): 267-269,287.
Abstract PDF(329KB) icon1535 icon391
Abstract:
In order to enhance the ability of diagnosing faults and improve maintenance,we develop a condition monitoring and main faults diagnosing system for a turbojetengine. The whole system is divided into two sub-systems, the engine operationmonitoring and the ground computer data processing. The former is used for analysing engine performance tendency and diagnosing some main faults in the engine, i.e., engine-surge, exceeding drop rpm, auto-flameout and ;so on. Inaddition, it can record the parameters at take-off or before and after fault occurs. When faults take place in the engine, it can also give pilots warning. The latter is used for analysing reasons of faults and estimating engine performance tendency.
MATHEMATICAL MODELLING AND DYNAMIC ANALYSIS OF A BOOSTER STATION DRIVEN BY WZ5G AEROENGINES
Lu Zehua, Ye Bosheng, Yang Yiming, Xu Chaoqun
1987, 2(3): 270-272,287-288.
Abstract PDF(400KB) icon1798 icon407
Abstract:
A split-shaft gas turbine adapted from WZ5G aeroengine is quite suitable for driving a booster compressor station in a long gas pipeline. A mathematical model is established for a booster station with two series centrifugal compressors driven separatelyby the split-shaft gas tnrbine of WZ5G aeroegine. The model is simplified by a static state optimization. Its transfer functions are obtained through a nonsin-gulartransformation. The model is applied to analysing the stability and dynamic responses of the system. Some conclusions are drawn which are helpful to controllingof the long gas pipeline.
A DIGITAL ELECTRONIC CONTROL SYSTEM RST-6 FOR WZ6G ENGINE
Zhu Zhihua, Chen Shengyu
1987, 2(3): 273-275,288.
Abstract PDF(331KB) icon1648 icon413
Abstract:
A digital electronic control system RST-6 for WZ6G engine, in which a CMC-80 microcomputer and a step-motor driven by a needle metering valve are used. In order to enhance the accuracy of control and the speed of system response, variable coefficient dual-speed control with PID feedback is adopted. A large number of integratedelements and anti-interference measures are employed to increase the reliabilityof the system.The present system has run on trial 4200 hours in the Zhongyuan oil field.
A FULL-AUTHORITY DIGITAL ELECTRONIC CONTROL UNIT QSK-06 FOR AEROENGINE WJ6G2B
Gao Yunhe, Zhang Shaoji, Xing Jiarui
1987, 2(3): 276-278,288.
Abstract PDF(441KB) icon1970 icon485
Abstract:
A full-authority digital electronic control unit QSK-06 has bees designed for industrial application of turboshaft aeroengine WJ6G2B. By adopting the dual channelstructure and some effective measures in both hardware and software, high reliabilityis achieved, A gain-variable PI control is considered to offset the influence of system performance caused by engine conditions. The design ensures meeting the special requirements for long-time operation of industrial gas turbine. The QSK-QG has undergone a verification test on the WJ6G2B rig with a compressor as a load. This paper covers the design of QSK-06, the approaches to enhance the operating reliability and the engine test results.

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