2012 Vol. 27, No. 2

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Display Method:
A coupling dynamic model for whole aero-engine vibration and its verification
CHEN Guo
2012, 27(2): 241-254.
Abstract PDF(1659KB) icon2266 icon648
Abstract:
In order to study the whole aero-engine vibration,a generalized complex rotor-support-casing coupling dynamic model was established.In the model,the rotor and casing systems were modeled by means of the finite elements method;the support systems were modeled by the lumped parameter model,and the nonlinear factors of ball bearings and the squeeze film dampers were also included;the complex structures with multi-rotor and multi-casing was considered.A numerical integral method was used to obtain the system responses.Two aero-engine rotor testers were designed to verify the new model.The coupling dynamic model was established for the tester according to the new method,and the modal tests were carried out.The computation results were compared with the experiments results.The results indicate the effectiveness of the new method.
Experimental investigation on tension behavior of DD6 single crystal thin-walled cylindrical specimen under high temperature
HE Ai-jie, LI Shi-feng, LUO Qiu-sheng, ZENG Jun, MA Jian, WU Chang-bo
2012, 27(2): 255-259.
Abstract PDF(703KB) icon1786 icon597
Abstract:
The thin-walled simulative specimens of DD6 single crystal superalloy were prepared with selected-crystal method.The tensile properties of thin-walled tube with [001] crystallographic orientations were investigated at 850℃ and 980℃,and one half of the specimens were plates with film cooling holes.The results show that the [001] orientation tensile properties with film cooling holes are reduced by 10.5% than without film cooling holes at 850℃,and the [001] orientation tensile properties with film cooling holes correspond with those without film cooling holes at 980℃.It indicates that when the temperature is higher,the effect to tensile properties is more significant.However,the [001] orientation tensile properties with airing condition are increased by 16% than those without airing condition at 980℃.Therefore,the surface state and airing condition play a main role to affect the properties of single crystal thin-walled tube.Especially,it is the airing condition that the mechanical properties have obviously improved.
Application of damping ratio for turbine blades by modal testingon finite element analysis
WANG Chun-jian, CHEN Guan-feng, QING Hua
2012, 27(2): 260-264.
Abstract PDF(637KB) icon2072 icon591
Abstract:
For more accurately imitating turbine blade’s harmonic response characteristic by using finite element method, studied how to genetate damping matrix on finite element analysis, and selected a damping matrix model which was suitable for the design of real turbine blades. In the finite element harmonic response analysis of turbine blade, a method for generating damping matrix was made on the basis of the damping ratio which was measured in modal testing. The method can be used for any individual resonance frequency problem or coupling resonance frequency problem. After imitated turbine blade’s response experimentation, system damping ratio and imitated turbine blade’s displacement response was measured. According to the system damping ratio and the method, analyzed imitated turbine blade’s harmonic response which had individual resonance frequency. The analysis result indicate that the imitated turbine blade’s response is approximately consonant with the experimental result. So it is accurate that using the method to analyze harmonic response of turbine blade.
Approximate analytical model of oil-film force for finite length elliptical journal bearing
WANG Yong-liang, LIU Zhan-sheng, QIAN Da-shuai, HE Peng
2012, 27(2): 265-274.
Abstract PDF(1846KB) icon1827 icon476
Abstract:
The Reynolds equation of plain journal bearing lubrication was solved by separation of variables method,the pressure distribution expression of oil-film in plain journal bearing was obtained based on dynamic boundary conditions,and the approximate analytical expression of plain journal bearing oil force was deduced.The boundary conditions of elliptical bearing were analyzed.The approximate analytical model of elliptical bearing oil-film was obtained by combining the oil film boundary conditions of elliptical bearing with oil film force expression of plain journal bearing.The oil film force is verified with high accuracy and suitability for any aspect ratio by comparing with the finite difference method,long bearing model,and the short bearing model.The nonlinear rotordynamic behavior of a rigid rotor on elliptical bearing was investigated by Runge-Kutta method,the results of numerical simulation show that the model can describe the dynamic characteristics of elliptical bearing oil film well.
Application of phase-measurement-profilometry in blade measurement
LI Hua-wei, SHEN Zuo-chun, QIN Yin-hong, BAO Hong, ZHOU Yan-zhou
2012, 27(2): 275-281.
Abstract PDF(1836KB) icon1772 icon440
Abstract:
In order to solve the problem that three-dimensional (3-D) profile measurement of blades was costly and had low efficiency,a 3-D profile measurement system based on phase measurement was built.After system calibration,a ball bearing was measured to test the system’s measurement accuracy and got the measurement accuracy of 0.08±0.01mm.Then data acquisition of a blade was carried on from different directions for six times.The 3-D point cloud of the whole blade was get through data fusion and got the different blade sections based on the point cloud,which provided datas for the detection of blade size and surface contours.Phase-measurement-profilometry is used in blade measurement, which ensures the measurement accuracy and has lower costs.So using phase-measurement-profilometry in blade measurement is very meaningful.
Method for analyzing two-dimensional coupled vibration of turbine blade with dry friction platform damper
HE Shang-wen, REN Xing-min, QIN Wei-yang, DENG Wang-qun
2012, 27(2): 282-288.
Abstract PDF(1113KB) icon1636 icon445
Abstract:
A two-dimensional micro slip model was presented by introducing parallel springs with sliding contact to simulate two-dimensional friction force in in-plane motion.Two coupling spring-damper elements were used to mimic the damping effect and the finite element model of the B-G (blade-ground) platform damper was set up.From the friction model and finite element model,the reducing vibration characteristic of blade at or near operating frequency is studied.The results show that there is a range of normal load,during which the steady amplitude of blade can be controlled to a minimum value,and that exciting frequency has no effect on reducing vibration characteristic of blade.The two-dimensional micro model can be developed to analyze blade with platform damper as contacting motion is in complicated in-plane.
Inverse method for estimating the vibration stress of turbine blades based on combined high-and-low cycle fatigue tests
SUN Rui-jie, YAN Xiao-jun, NIE Jing-xu
2012, 27(2): 289-294.
Abstract PDF(954KB) icon2174 icon595
Abstract:
An inverse method based on combined high-and-low cycle fatigue (HCF/LCF) tests and the outfield practical failure data was developed to estimate the vibration stress of the turbine blade in working condition.All the test specimens of the turbine blades owned the same production procedures as the outfield failure blades.Two groups of HCF/LCF tests were performed,one was median life test at six vibration stress levels,and the other was life dispersion test at a given vibration stress level.Then,P-S-N curves were extrapolated with the maximum likelihood method.Finally,vibration stress of the turbine blade in working condition was determined by the P99.87%-S-N curve combined with the statistical life of the outfield practical failure data.
Numerical analysis of real aero-engine first-stage fan blade containment
HE Qing, XUAN Hai-jun, LIU Lu-lu
2012, 27(2): 295-300.
Abstract PDF(1551KB) icon2807 icon613
Abstract:
To study the mechanism of the aero-engine fan blade containment process at the maximum operating speed and the effects of multiple blade interaction on it, several numerical simulations with three different computational models based on the real aero-engine first-stage fan component were carried out. Results show that uncontained failure is observed under the impact of the released blade. Initial cracks on the casing are caused by biaxial tensile stresses, and large-scale tearing is likely to arise along the initial cracks. The released blade suffers from complicated force and is torn into two parts. There are three major impacts during the containment process. The first impact is the interaction between the blade tip and the casing, which is slight and lasts for a short time. The impact force reaches maximum during the second impact. The influences of the remaining rotating blades afterward are noticeable during the third impact. Under the impact of the remaining rotating blades, the increase of the kinetic energy of the released blade is obvious.
Diagnosis of aero-engine with early vibration fault symptom using DSmT
ZHAI Xu-sheng, HU Jin-hai, XIE Shou-sheng, LIU Jia, LI Qiang
2012, 27(2): 301-306.
Abstract PDF(379KB) icon1760 icon591
Abstract:
Multisensor network information fusion method was used to diagnose the aeroengine with early vibration fault symtom,and several vibration sensors had been fixed on different positions of the aeroengine to build the multisensor network.However the information collected from different sensors would highly conflicts when early vibration fault happens,and the information fusion result get by Dempster-Shafer rule would be unreasonable,so Dezert-Smarandache theory (DSmT) was applied to solve the problem.In the early vibration fault diagnosis system proposed in this paper,firstly,a method based on the intrinsic mode functions (IMF) energy entropy was used to extract the signal’s feature;secondly,basic belief assignment function was constructed based on the output of the back propagation (BP) neural network;lastly,DSmT combination rule was used to combine the different evidences and make the final decision.Two examples suggest the approach is available to solve the problem of high-conflict information fusion when early vibration fault happens,and the diagnosis results are reliable and effective.
Residual stress of laser peening processed TC17 and stress relax prediction model based on support vector machines theory
LI Qi-peng, LI Ying-hong, HE Wei-feng, WANG Cheng, TONG Chong-lou
2012, 27(2): 307-311.
Abstract PDF(463KB) icon1824 icon452
Abstract:
TC17 titanium alloy was laser peening (LP) processed by different power densities.X-ray diffraction method was used to measure the residual stress induced by LP.Vacuum thermal retardation at 280℃ and 450℃ for 160min was used to study the residual stress relaxation regularity.The prediction model was based on support vector machines (SVM) theory and the model was verified by experimental results at last.The results show that 4GW/cm2 is the optimal power density to process TC17 titanium alloy.The thermal relaxation is about 11.24%,27.11% at 280℃ and 450℃ for 150min respectively.And relaxation enhances to 33.9% after 280℃ and 450℃ alternate vacuum thermal retardation.The relaxation indicates that the majority of residual stress is preserved,and thus improves the fatigue resistance of titanium alloy.The residual stress prediction model can characterize the relaxation regularity accurately.And the model is useful to analyze the residual stress thermal relaxation of other metals.
Influence of search algorithm on optimized measurement positions of effective independent method for modal test
LIU Yuan, ZANG Chao-ping, LIU Zhong-hua
2012, 27(2): 312-318.
Abstract PDF(2499KB) icon1587 icon522
Abstract:
The influences of three different search algorithms,i. e.:direct search method,step accumulating method and step eliminating method,on the effective independent method were discussed with respect to the optimized measurement positions for modal test.An aero-engine component was taken as an example to demonstrate the application of the approach.The optimized measurement positions selected by these three search algorithms for the effective independent method were analyzed comparatively with respect to modal correlation,kinetic energy of each mode contributed to the measured positions and the Fisher information matrix.The results indicate that the step eliminating method can most effectively achieve the goal of the effective independent method by increasing the spatial resolution of the target mode shapes.
Experiment on flow and heat transfer characteristics in trapezoidal passage of turbine blade trailing with different pin-fins
TAN Xiao-ming, HU Xun-yao, ZHANG Jing-zhou
2012, 27(2): 319-325.
Abstract PDF(1439KB) icon1788 icon501
Abstract:
Experimental study was carried out to analyze the flow and heat transfer characteristic of trapezoidal channel fitted with staggered arrays of circle,ellipse,dumbbell and water-drop shaped pin fins.The results show that:with the same Reynolds number of inlet flow,the pressure loss of drop-shaped pin fins is about 57% of that of the circle pin fins.The cooling effect of the circle pin-fins was almost the same with dumbbell pin-fins which is 20% higher than that of elliptical pin-fins and 25% higher than that of drop-shaped pin-fins.The differences of the flow and heat transfer features of different inlet shapes were not distinct.The inlet flow through double arrays of holes had the higher pressure and better cooling effect in trapezoidal passage.
Numerical study of test gas vitiation effects on hydrogen-fueled scramjet combustion
CHEN Chao-qun, TIAN Liang, XU Xu
2012, 27(2): 326-334.
Abstract PDF(1253KB) icon1811 icon459
Abstract:
The effects of major vitiated species (H2O and CO2) and minor vitiated species (H,OH and O radicals) produced by combustion air preheater on ignition and combustion of hydrogen-fueled scramjet were numerically investigated.Firstly,kinetic analyses with CHEMKIN SENKIN code were conducted to evaluate the effects of contamination on the ignition delay times of hydrogen fuel over a range of temperature and pressure variations.Then numerical simulation of a three-dimensional reacting flow in hydrogen-fueled scramjet combustor was performed.The two-equation shear stress transport κ-ω turbulence model was used for modeling turbulence and 33 reactions finite-rate chemistry was used for modeling the H2/air kinetics.The results show that: free radical species such as H,O,and OH may significantly promote the ignition process of hydrogen-air at relatively low initial temperature and pressure.However,H2O and CO2 have inhibition effects on the ignition process.Under the same conditions,H2O has more effective inhibition effects than CO2.The temperature and pressure rise due to combustion are lower in the air vitiated with H2O and CO2 because of their higher heat capacities and more dissociation.Combustion efficiency and thrust calculated for vitiated air case are lower than clean air case.These results indicate the importance of accounting for vitiation effects when extrapolating performance data from ground test to flight demonstration.
Investigation on the performance of an ultrasonic/pressure-swirl hybrid injector
JIN Yi, HE Xiao-min, WU Ze-jun, DING Guo-yu, QIN Wei-lin
2012, 27(2): 335-342.
Abstract PDF(1546KB) icon1782 icon456
Abstract:
The feasibility for an ultrasonic/pressure-swirl hybrid injector to be applied in aero-engine combustors was investigated experimentally.Mass flow characteristics,atomization performance including Sauter mean diameter (SMD) and spray angle were obtained by cool spraying experiments.A single-dome rectangular combustor rig has been constructed with the cross section dimensions 117mm×60mm and series of experiments have been conducted.Results indicate that the mass flow characteristics are in accord with that of a conventional pressure-swirl injector,the SMD falls between 8~12μm without air supply,the SMD falls between 8~12μm under the existence of ultrasonic wave (kerosene is employed as the fuel),and the spray angle is strongly dependent on the air supply.Good flame stability has been obtained for all the combustion experiments conducted.Under certain situations,combustion efficiency of the combustor rig can achieve 99%.
Aero piston engine capacitor discharge ignition system optimization research and design
ZHANG Qi, XU Guo-qiang, DU Fa-rong
2012, 27(2): 343-349.
Abstract PDF(644KB) icon1798 icon451
Abstract:
Reliable and robust high energy ignition system was optimized and tested for aero piston engine. The traditional fixed-frequency PWM (pulse width modulation) flyback step-up charging method and its drawbacks were analyzed, and then a variable-frequency PFM (pulse frequency modulation) charging method and a way to sense output voltage without resistor arrays feedback were proposed, and the appropriate charge time computation algorithm was presented, lastly the capacitor charge circuit was designed and tested. The experimental result shows that the proposed charging method works correctly with more efficiency, and the charge time computation formula is precise.
De-icing experiment and numerical simulation of the electro-impulse de-icing system
LI Qing-ying, ZHU Chun-ling, BAI Tian
2012, 27(2): 350-356.
Abstract PDF(1131KB) icon1612 icon457
Abstract:
An electro-impulse de-icing system was developed to undertake the de-icing experiments.De-icing occurred when the circuit was trigged three times with the discharge voltage 500V.Meanwhile,the de-icing excitation exerting on the aluminum plate was numerically simulated in the eddy current field.A three dimensional finite model of ice and aluminum plate was introduced to analyze the ice failure in the nonlinear transient method by killing elements of the ANSYS FE(finite element) code.The ice failure criterion was checked by comparing the Labeas de-icing criterion with the first strength theory.It concludes that the latter is more suitable for simulating the de-icing process by loading the de-icing excitation in this test.
Numerical investigation on temperature distribution of an air-cooled and thermal barrier coating blade
WANG Li-ping, ZHANG Jing-zhou, YAO Yu
2012, 27(2): 357-364.
Abstract PDF(1120KB) icon1794 icon487
Abstract:
For a serpentine internal cooling flow path in which the impingement cavities were located on the pressure side and suction side alternately,the commercial code FLUENT was used for three-dimensional conjugate heat transfer simulation to determine temperature distribution on an air-cooled and thermal barrier coating (TBC) blade.The effect of TBC thickness on the temperature decreasing capacity for blade metal surface was analyzed,and the temperature difference with/without considering radiation heat transfer was also analyzed.In the case of primary flow temperature 1600K and cooling flow temperature 700K,the maximum temperature for the present air-cooled blade can be controlled within 1100K when the cooling massflow is about 7.47% of the primary massflow and the TBC thickness was 0.2mm.The temperature decreasing capacity for TBC reaches about 130-180K when the TBC thickness is 0.15-0.35mm assuming the emissivity of TBC is the same as that of blade metal surface.The temperature difference with/without considering radiation heat transfer is about 60K.
Experiment on overall temperature distribution of the inter-stage turbine double vortex combustor
WANG Wei-jian, DU Shang-ming, ZHANG Rong-chun, TAN Wen-long, FAN Wei-jun
2012, 27(2): 365-371.
Abstract PDF(959KB) icon1970 icon618
Abstract:
Based on the single vortex combustor,the influential factors of overall temperature distribution in the double vortex combustor were studied experimentally.The results of experiments were obtained showed that:(1) With the Mach number Ma of mainstream increase,the overall temperature distribution factor (OTDF) decrease.(2) The mainstream temperature has great impact on the overall temperature distribution,the OTDF decrease with the increase of mainstream temperature.(3) With the excess air coefficient increase,the OTDF increase firstly and then level off or decrease.(4) Different cavity structures have a great impact on the OTDF,after compare several test pieces,the piece which the aspect ratio is 0.8,the after-body intake is slot air intake could achieve the best OTDF.
Boundary layer bleeding of three-dimensional compression hypersonic inlet
YUE Lian-jie, YE Qing, XU Xian-kun, CHEN Li-hong, ZHANG Xin-yu
2012, 27(2): 372-378.
Abstract PDF(1912KB) icon1820 icon587
Abstract:
Various methods of boundary layer bleeding were investigated to control the streamwise vortices generated by shock/boundary layer interaction in the isolator of three-dimensional compression hypersonic scramjet inlet.The boundary layer flow patterns were visualized by oil dot technique and numerical simulation.And the effect of different bleedings on inlet performance was then analyzed.It was revealed that the streamwise vortices were mainly attributed to the boundary layer separation on the sidewall,and the bleeding on the sidewall separation is effective.Compared to the bleeding around the attachment line,the bleeding on the separation zone remarkably reduced the boundary layer separation and effectively diminished the development of the vortex structure,which ultimately contributed to higher total pressure recovery at the inlet exit.Moreover,the flow uniformity was improved as the bleeding area increasing,while at the cost of more mass loss.
Two attempts of passive control methods on hypersonic flow separation induced by a fin
LV Jun-ming, YUAN Xiang-jiang, WANG Qiang
2012, 27(2): 379-386.
Abstract PDF(1191KB) icon1660 icon431
Abstract:
Dual-mode scramjet engine may suffer unstart because of a large enough upstream or downstream pressure disturbance.Unstart would dramatically reduce the thrust and could compromise the stability and safety of the vehicles,so it is necessary and important to investigate the effective control methods.Fifth-order characteristic-wise weighted essentially non-oscillatory (WENO) scheme and third-order total variation diminishing (TVD) Runge-Kutta (R-K) method were applied to solve the three-dimensional Navier-Stokes (N-S) equations,to explore two passive control methods using trips and passive suck/blow respectively,and to explore corresponding control effect on the hypersonic flow separation caused by shock wave/boundary layer interaction induced by a fin.The results show that the vortex in flow direction induced by trips affects the flow separation structures evidently.The second separation and reattachment lines almost disappear.Control method employing passive suck/blow balances the pressure between the separation and reattachment areas and reduces the pressure gradient which depresses the separation structures.
Experiment of a Ma4 chin inlet with mixed-compression
JING Jian-peng, GUO Rong-wei, SUN Xiao-ping, HE Wei
2012, 27(2): 387-394.
Abstract PDF(1167KB) icon1805 icon476
Abstract:
Experiment of a Ma4 chin inlet with mixed-compression had been done,the pneumatic performance of the inlet was obtained.The results showed that: (1) When Ma=3.5,angle of attack and angle of yaw are both 0 degree,the total pressure recovery coefficient increased at first and then decreased with the increasing of back-pressure,the total pressure recovery coefficient got its maximum at the critical state. (2) Under the critical states of angle of attack and angle of yaw are both 0 degree.The total pressure recovery of inlet decreased linearly with the increasing of flight mach number. (3) The inlet performance declined under pitch or yaw conditions. (4) The inlet has restarting character in the unstart process caused by back-pressure,phenomenon of hysteresis is not obtained in the loop from start to restart induced by the back pressure during the mass adjustor moving forward/backward process(AFBP).
Full-scale crash test and FEM simulation of a crashworthy helicopter seat
HU Da-yong, ZHANG Xiang
2012, 27(2): 395-400.
Abstract PDF(1290KB) icon1660 icon465
Abstract:
Crashworthy seat structure with considerable energy absorption capacity is a key component for aircraft to improve its crashworthiness and occupant survivability in emergencies.According to Federal Aviation Administration(FAA) regulations,seat performance must be certified by dynamic crash test which is quite expensive and time-consuming.For this reason,numerical simulation is a more efficient and economical approach to provide the possibility to assess seat performances and predict occupant responses.A numerical simulation of the crashworthy seat structure was presented and the results were also compared with the full-scale crash test data.In the numerical simulation,a full-scale three-dimensional finite element model of the seat/occupant structure was developed using a nonlinear and explicit dynamic finite element code LS-DYNA3D.Emphasis of the numerical simulation was on predicting the dynamic response of seat/occupant system,including the occupant motion which may lead to injuries,the occupant acceleration-time histories,and the energy absorbing behavior of the energy absorbers.The agreement between the simulation and the physical test suggestes that the developed numerical simulation can be a feasible substitute for the dynamic crash test.
Effect of asymmetric exciting on space-time structure and characteristic of cascades
YAN Jia-chao, YUAN Wei, ZHOU Sheng
2012, 27(2): 401-409.
Abstract PDF(1300KB) icon1507 icon454
Abstract:
Based on the unsteady cooperative flow,when the exciting frequency was kept,asymmetric wake impact effect (WIE) could make better performance than the symmetric circumferential distribution.The author studied the mechanism of the asymmetric WIE.Firstly,the way of intermittent cooperative flow caused by intermittent jet in one passage was discussed to learn the trait of the intermittent cooperative flow.Secondly,a two-dimensional computational fluid dynamic (CFD) simulation of a 1/4 low speed compressor mid-span flow field was analyzed.The space-time structure of the compressor was studied.And then the asymmetric inlet guide vane (IGV) affection on that was studied.Thirdly,an experiment was designed to prove the result get from the former research.The result is the circumferential distribution of IGV decides the space-time structure of the downstream rotor flow field.The length of the excitation decides the effect of the WIE,and the dispersed IGV can improve the quantity of the space-time structure of the flow field and reduce the loss of the compressor.
Stator wake variability in a combined compressor
ZHAO Ben, YANG Ce, ZHANG Ji-zhong, LI Du, Qi Ming-xu
2012, 27(2): 410-418.
Abstract PDF(2904KB) icon1737 icon451
Abstract:
The unsteady flow in a combined compressor,which consists of axial flow and centrifugal compressor impellers,was simulated numerically at mass flow of 1.15kg/s and speed of 60kr/min (design point).The objective was an in-depth analysis of the factors caused stator wake variability.In addition,a method about changing cycle and amplitude of stator wake variability was presented.The results indicate that:stator wake variability is influenced by geometric factor,up- and downstream moving rows.The blade passaging frequencies of up- and downstream rotor are related with the cycle of stator wake variability.Note that the equal blade passaging frequencies in all stages,the clocking positions have much effect on the amplitudes of stator wake variability.Moreover,along the blade’s highness,the amplitudes of stator wake variability are different,which located at low span was greater than that at mid-span and high-span.
Numerical simulation on internal flow characteristics in the discharge chamber of an afterburning fuel pump under off-design conditions
XUE Mei-xin, WU Di, PIAO Ying
2012, 27(2): 419-424.
Abstract PDF(1608KB) icon1762 icon559
Abstract:
The unsteady flow in an afterburning oil pump on a certain type of aero-engine was simulated for the uncommon cavitation damage problem near its casing tongue,with arbitrary sliding mesh technology.The discharge chamber internal flow characteristics at off-design conditions were investigated to find out possible conditions causing the casing tongue cavitation.The results showed that:under large flow-rate condition,there are two separated vortices of different sizes located in the cone-shaped tube passage,while the fuel flowed past the casing wall without obvious separation in the annular chamber,which hardly trigger cavitation;under small flow-rate condition,the two separated vortices extend to take up most part of the cone-shaped passage,incoming flow of the diffuser is choke up with a part of the fuel blocked at right side flowing back to the annular chamber around the tongue.As a result,serious flow separation is raised with a high pressure decrease,which is expected to generate cavitation and following damage on the casing tongue.
Influence of shock waves/leakage vortex/boundary layer separation interaction in a single-stage transonic axial compressor
XIE Fang, CHU Wu-li, ZHANG Hao-guang
2012, 27(2): 425-430.
Abstract PDF(896KB) icon1956 icon477
Abstract:
Three-dimensional(3-D) numerical simulations were conducted to analyze the flow field in transonic rotors Rotar 37. The results with design tip clearance were compared with no tip clearance condition. Mutual influence of shock, boundary layer separation, clearance leakage the vortex accelerated the occurrence of stalled. Reduce clearance can enlarge the steady border. The suction position applied on passive control technology to improve port flow condition was given.
Rapid prototype design for turbo-fan engine fault diagnosis
LU Feng, HUANG Jin-quan, KONG Xiang-tian
2012, 27(2): 431-437.
Abstract PDF(672KB) icon1751 icon637
Abstract:
In order to meet the requirements of turbo-fan engine fault diagnosis,a kind of rapid prototype simulation design way based on the baseline of the engine for gas-path fault diagnosis was proposed.Considering the precision of the fault diagnosis in the flight envelope influenced by the engine baseline,optimal transformation index was selected in simulation transformation for the setup of baseline.The weighted least-squares algorithm was used to design the fault diagnosis model,which was downloaded to National Instrument (NI) CompactRIO to form rapid prototype simulation system.A series of test experiments on a turbo-fan engine show the effectiveness of this rapid prototype design method for gas-path fault diagnosis.
Aero-engine stability seeking control based on improved SVR-PSO
WANG Lei, XIE Shou-sheng, JIANG Ai-wu, MIAO Zhuo-guang, ZHAI Xu-sheng
2012, 27(2): 438-444.
Abstract PDF(854KB) icon1621 icon437
Abstract:
In the seeking control of multivariable aero-engine,general optimization algorithm may find the locally optimal solution.An improved algorithm based on particle swarm optimization (PSO) and support vector regression (SVR) was applied to aero-engine stability seeking control,setting the lower limits for surge margin to keep aero-engine working stably.The working point with minimum surge margin was searched globally.The simulation results show that the designed stability control algorithm could reduce the surge margin while keeping the thrust constant and reduce the turbine inlet temperature and specific fuel consumption effectively.
Partition optimization in the flight envelope for control design of aero-engines
LI Shu-qing, ZHANG Sheng-xiu, HU Wei-hong
2012, 27(2): 445-449.
Abstract PDF(708KB) icon2242 icon439
Abstract:
According to the optimization theory and linear system theory,the method of flight-envelop optimization partition for aero-engines is researched.First,linear state variable mode (LSVM) was used to describe aero-engine’s dynamic characteristic of small perturbation on steady operating point,and the perturbation between LSVMs was denoted by the perturbation of coefficient matrix eigenvalues and low-frequency gains of the LSVMs.Then,a general distance based on the perturbation of eigenvalues and low-frequency gains of the LSVMs was put forward.And the problem of dividing the flight envelope and selecting the nominal points in a flight envelope was translated into a most overlay problem.Thus,based on the general distance,a set of least number of nominal points could be found to divide the flight envelope by using optimizing method.Last,a flight envelope area of a turbofan engine was divided by using this method,and the results indicated that this method was proper.
Air turbine starter pressure controller modeling and numerical simulation based on AMESim
SUN Mu-qiao, SU San-mai, CHENG Jian, SONG Rui-tao
2012, 27(2): 450-456.
Abstract PDF(875KB) icon2140 icon445
Abstract:
Based on the structure and principle of pressure controller (which is a pressure feedback control system composed of several pneumatic components) of air turbine starter system (ATS),the mathematic model was established through theoretical analyze.Then a pressure control system simulation platform was developed based on the AMESim simulation environment by using the modularization modeling method.Take a kind of ATS as the object for simulation,the pressure characteristics was simulated by giving ramp signal,random square wave signal and sine signal.The result show that output pressure can maintain within required range,and compared with the test data of typical operation state,the simulation error is less than 3%.The model of pressure controller is suitable for engineering.
Structural optimization of elliptical-tip star propellant grain using sub-problem approximation
Muhammad Adnan, SUN Bing, ZHANG Jian-wei, Ali Sarosh
2012, 27(2): 457-464.
Abstract PDF(762KB) icon1362 icon470
Abstract:
A method is presented here for structural optimization of elliptical-tip star grain.The grain structural integrity was improved by minimizing the most critical area of inner bore hoop strain during cool down.Optimization was done by sub-problem approximation method in conjunction with finite element analysis.Both radii of the ellipse were varied during optimization to find the optimal ellipse.The optimization resulted in grain geometry having minimum level of Inner bore hoop strain without violating the preset limits of burning perimeter.The von mises strain at grain inner bore was also reduced in resultant grain.
Flow field simulation of N2O cavitation Venturi
SHI Gang, LIANG Guo-zhu
2012, 27(2): 465-471.
Abstract PDF(1205KB) icon1794 icon460
Abstract:
In order to get the distribution of cavitation flow field of N2O in cavitation Venturi,governing equations of two-phase mixture flow were solved based on state equation for real gas and full cavitation model.According to the special properties of N2O,numerical simulation was performed on a cavitation Venturi under three experimental states.Two different methods:with and without the influences of latent heat were used respectively and comparison and analysis of two different results were made.The cavitation area calculated by the method considering the influences of latent heat was smaller and obvious change of temperature in and around the cavitation area was found.The results indicate that the necessity and correctness of calculation considering the influences of latent heat,which can be a certain guide for the design of Venturi.
Research on gas film force of aerostatic gas bearing and its coupled dynamics with rotor
ZHAO Guang, LIU Pan-nian, YU He-chun, MA Wen-qi, CUI Ying, LIU Zhan-sheng
2012, 27(2): 472-480.
Abstract PDF(1285KB) icon1848 icon613
Abstract:
For aerostatic bearings with tangential gas supply,a three dimensional solid model was developed.Combining structured mesh with unstructured mesh,three-dimensional compressible Navier-Stokes (N-S) equations were solved with computational fluid dynamics (CFD) commercial software based on finite volume method.According to the simulation results,gas film supporting force model related to rotor eccentricity and speed was derived with data fitting.Dynamics model of aerostatic bearing-rotor system was built with finite element method and critical speed and unbalance response were solved using Newmark integration method.Experimental tests were performed to verify the numerical simulation results.Research results show that film main supporting force changes linearly in the state of low-speed,small eccentricity,whereas increases rapidly under high-speed and large eccentricity,and effect of dynamic pressure of aerostatic bearing significantly enhances.Coupling supporting force between x and y directions changes nonlinearly with speed and eccentricity;First and second critical speed are sensitive to the current structural stiffness while the third one is not.Therefore,nonlinear characteristics of gas bearing and coupled dynamics of rotor-bearing system are complex;in the case of bearing structure design,coupling between gas bearing and rotor,work speed range should be taken in to full account.

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