2009 Vol. 24, No. 4

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Designing a power plant with highest efficiency:results from SFB 561
Dieter Bohn
2009, 24(4): 717-728.
Abstract PDF(1681KB) icon1465 icon680
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The goal of Collaborative Research Centre(SFB) 561 "thermally highly loaded,porous and cooled multi-layer systems for combined cycle power plants" is to expand the current technological and scientific knowledge on power plants in order to achieve total efficiencies of 65% in a combined cycle power plant in the year 2025.Therefore,the aero-thermomechanical,structural-mechanical,materials' scientific and production fundamentals for the development of steam and gas turbine components that are able to withstand highest thermal loads are being worked out within this SFB.This means for the gas turbine that combustion chamber outlet temperatures of 1520℃ at 1.7MPa are to be attained.In order to control these high temperatures,it is not only required to develop new materials' solutions,including thermal barrier coatings,but also to apply improved cooling techniques,as for example effusion cooling.This novel cooling concept is to be realised through open-porous structures.These structures can consist of drilled open-porous multi-layer systems or open-porous metallic foams.The development of graded multi-layer systems is also extremely important,as the grading will enable the use of coolant in dependence of the requirements.The live steam parameters in the high pressure turbine are expected to be increased up to approximately 700℃ with pressure of 30MPa.These elevated steam parameters can be encountered with Ni-base alloys,but this is a costly alternative,associated with many manufacturing difficulties.Therefore,the SFB proposes cooling the highly loaded turbines instead,as this would necessitate the application of far less Ni-base alloys.To protect the thermally highly loaded casing,a sandwich material consisting of two thin face sheets with a core of a woven wire mesh is used to cover the walls of the steam turbine casing.The current state of the research shows that by utilising innovative cooling technologies a total efficiency of 65% can be reached without exceeding the maximum allowable material temperature,thereby prolonging the life-span.
Isothermal study of effusion cooling flows using a large eddy simulation approach
W. P. Bennett, Z. Yang
2009, 24(4): 729-739.
Abstract PDF(1689KB) icon1251 icon433
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An isothermal numerical study of effusion cooling flow is conducted using a large eddy simulation(LES) approach.Two main types of cooling are considered,namely tangential film cooling and oblique patch effusion cooling.To represent tangential film cooling,a simplified model of a plane turbulent wall jet along a flat plate in quiescent surrounding fluid is considered.In contrast to a classic turbulent boundary layer flow,the plane turbulent wall jet possesses an outer free shear flow region,an inner near wall region and an interaction region,characterised by substantial levels of turbulent shear stress transport.These shear stress characteristics hold significant implications for RANS modelling,implications that also apply to more complex tangential film cooling flows with non-zero free stream velocities.The LES technique used in the current study provides a satisfactory overall prediction of the plane turbulent wall jet flow,including the initial transition region,and the characteristic separation of the zero turbulent shear stress and zero shear strain locations.Oblique effusion patch cooling is modelled using a staggered array of 12 rows of effusion holes,drilled at 30° to the flat plate surface.The effusion holes connect two channels separated by the flat plate.Specifically,these comprise of a channel representing the combustion chamber flow and a cooling air supply channel.A difference in pressure between the two channels forces air from the cooling supply side,through the effusion holes,and into the combustion chamber side.Air from successive effusion rows coalesces to form an aerodynamic film between the combustion chamber main flow and the flat plate.In practical applications,this film is used to separate the hot combustion gases from the combustion chamber liner.The numerical model is shown to be capable of accurately predicting the injection,penetration,downstream decay,and coalescence of the effusion jets.In addition,the numerical model captures entrainment of the combustion chamber mainstream flow towards the wall by the presence of the effusion jets.Two contra-rotating vortices,with axes of rotation along the stream-wise direction,are predicted as a result of this entrainment.The presence and characteristics of these vortices are in good agreement with previous published research.
Analytical solution of mixing efficiency of lobed mixer
LIU You-hong, XIE Yi
2009, 24(4): 740-745.
Abstract PDF(1629KB) icon1697 icon493
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The analytical solution of the mixing efficiency of the lobed mixer,in relation to that of the splitter mixer in the same cross-section area of outlet,was proposed by using the circular streamlines model,the planar diffusion flame model and the slender-body approach etc.,based on thoroughly study of the mixing mechanism of the lobed mixer.Then,the mixing efficiency of a practical turbo-fan engine lobed mixer was calculated in four flying cases.The results show that this analytical solution method is reliable and also applicable to the practical engineering calculation.
Analysis of the axisymmetric co-axial jet flow structure dominated by the inner jet
ZHOU Hua, XIA Nan
2009, 24(4): 746-752.
Abstract PDF(1266KB) icon1526 icon438
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Using Reynolds-averaged Navier-Stokes(RANS) as governing equations,the axisymmetric co-axial jet flow fields were simulated and compared with single nozzle jets.Based on the change rule of the field parameters including the turbulent kinetic energy (k),velocity (v) and pressure (p),the co-axial jet flow field has been divided into joint section,primary section and main section.A detailed analysis of the characteristic and flow mechanism was also carried out herein.With analysis of the interaction between inner and outer nozzle jets,it indicates that the level of the turbulent kinetic energy inside the primary section is lower than that of a single jet,which may lead to the reduction of the jets noise;the level of the turbulent kinetic energy inside the main section is higher than that of a single jet,which may lead to the enhancement of the mixing between the jets and the ambient gas.At the end of this paper,numerical results of flow rate are compared to the test data,validating the algorithm used in this work.
Numerical computation of view factor of complicated configuration
ZHANG Tao, SUN Bing
2009, 24(4): 753-759.
Abstract PDF(797KB) icon1976 icon495
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The formulas of view factor computation of ray uniform distribution on radiant semi-sphere were deduced.View factors were computed by combining finite element method(FEM) and ray uniform distribution according to the position of surface cells.Triangle grid was used to express outline of complicated configuration and judge shading.It was demonstrated by a comparison with FEM and Monte Carlo method that the computing precision and efficiency of this method is higher and shading judgment method is correct and highly efficient.
Study of aerodynamic ramp injector in supersonic combustion
WU Hai-yan, ZHOU Jin, SHAO Yan, ZHANG Shun-ping, SUN Ming-bo
2009, 24(4): 760-765.
Abstract PDF(830KB) icon2091 icon501
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The aerodynamic ramp was used to enhance mixing in supersonic combustion by forming two stream eddies.And the aerodynamic ramp was designed with injectors array.The schlieren and oil flow experiment of aerodynamic ramp were conducted on the straight united supersonic experimental equipment.The supersonic flow and combustion were simulated by the method of large eddy simulation(LES).The results show that the designed injectors array has the ability to accelerate the roll up course of streamwise vortices after the injection,which is beneficial for the mixing.And the combustion course enables the rise of the injection shear layer.Due to the smaller angle of injection,the ratio of total pressure loss of aerodynamic ramp is less than the physical ramp and transverse injection stream.
Flow visualization of micro/mini pulsating heat pipes
QU Jian, WU Hui-ying, TANG Hui-min
2009, 24(4): 766-771.
Abstract PDF(1153KB) icon1903 icon561
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Flow visualization was investigated for pulsating heat pipes(PHPs) of internal diameters(IDs) 2.5,2,1,0.5mm using a high speed charge coupled device(CCD).Under different heat inputs,both the alternating transformation of the quasi-static phase and oscillation phase vs.time lapse and the flow patterns were recorded.Bubbly flow,slug flow,semi-annular flow,wavy-annular flow and annular flow were observed.Results show that the ID has a significant effect on the flow patterns.As the ID decreases,the formation of the vapor slugs at the evaporation section due to the small/tiny bubbles aggregation is dominated by the single bubble growth and expansion.In addition,more elongated bubbles are observed in the evaporator section,and deformation and breakup of the vapor plugs will likely occur in the condenser section by reducing the ID of the PHP.For the micro PHP,the capillary wavy-annular flow is a fundamental flow pattern,and the transition from capillary wavy-annular to capillary slug flow occurs in the condenser section.
Influence of inlet preswirl on discharge and heat transfer characteristics of honeycomb and smooth labyrinth seals
YAN Xin, LI Jun, FENG Zhen-ping
2009, 24(4): 772-776.
Abstract PDF(1749KB) icon2040 icon464
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Three-dimensional Reynolds-averaged Navier-Stokes(RANS) equations were numerically solved to investigate the influence of the inlet preswirl on discharge and heat transfer characteristics in honeycomb and smooth labyrinth seals.The discharge and total temperature increase characteristics,as well as the leakage flow field of these two different seals,were also obtained under five different pressureratios at inlet preswirl ratios of-0.3,0,+0.3.The results show that the influence of the inlet preswirl on the leakage flow rate and meridian flow structure is nearly negligible for both honeycomb and smooth labyrinth seals.Positive inlet preswirl can decrease the total temperature difference between the seal inlet and outlet,while the negative preswirl will cause the opposite effect.The damping effect of the honeycomb can reduce the influence of the inlet preswirl on the total temperature difference.The computed windage heating power of the honeycomb seal is larger than that of smooth labyrinth seal with positive or without inlet preswirl,while it's smaller for the negative inlet preswirl condition.
Study of an improved aero oil cooling system design method
LI Lin-wei, GAO Hong-xia, YU Jian-zu, CHANG Li
2009, 24(4): 777-782.
Abstract PDF(724KB) icon1789 icon464
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The conventional design method of oil cooling system was introduced.Based on the synthetic analysis of the performance of heat exchanger,the heat transfer principle between the decelerator and oil,and the heat balance process of the oil system,an improved design method of helicopter decelerator oil cooling system was established to improve the heat balance temperature calculation and heat exchanger design,meanwhile the new heat balance process under other working conditions were considered to improve the reliability of the design.Based on this improved method,a helicopter decelerator oil system was designed as an example,showing the results consistent with theoretical analysis.
Thermal performance enhancement of inclined screen heat pipe using nanofluid
MA Qi, LIU Zhen-hua
2009, 24(4): 783-787.
Abstract PDF(799KB) icon1596 icon488
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An experiment was performed to investigate the effect of the inclination angle on thermal performance of screen heat pipe using nanofluid.The study key were the effects of the inclination angle and operating pressure on the heat transfer of both evaporator and condenser as well as the maximum heat flux of the heat pipe.The nanofluid consisted of water and CuO nanoparticles having a mean diameter of 50nm.The concentrations of nanofluid ranged from 0.5wt% to 2.0wt% and the operational pressures of the heat pipe varied from 7.45kPa to 19.97kPa which corresponds to saturated temperature ranged 40℃ to 60℃.The experimental results show that the effect of the particle mass concentration has a significant influence on the heat pipe thermal resistance.There exists an optimal concentration which corresponds to the minimum value of thermal resistance and this optimal concentration is 1% for all inclination angles.The inclination angle also has a very significant effect on the heat transfer enhancement effect for the heat pipe using nanofluid.There exists an optimal inclination angle which corresponds to the maximum enhancement of the thermal performance and this angle is.At the pressure of 7.45kPa,the evaporating heat transfer coefficients can be maximally enhanced about 20%,and the maximum heat flux averagely increased about 25%,while the thermal resistance decreased about 15%,when horizontal tube was replaced by the inclined tube of 45°.
Localization characteristics of vibratory mode for bladed disk assemblies
WANG Jian-jun, YU Chang-bo, LI Qi-han
2009, 24(4): 788-792.
Abstract PDF(750KB) icon1951 icon512
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It is well known that "deliberate mistuning" in blade design is effective for suppression of the aerodynamic stability (flutter).But the localization characteristics of vibratory mode for bladed disk assemblies with this mistuning are not yet researched deeply.In this paper the vibration characteristics of a typical bladed disk with deliberate mistuning were investigated,with particular regard to the localization characteristics of modal shapes for two mistuning strategies.For the cases considered it is found that "deliberate mistuning" in blade design can greatly increase the modal localization of bladed disk assemblies.
New approach of features extraction for rotor faults from continuous wavelet transform scalogram
CHEN Guo, DENG Yan
2009, 24(4): 793-798.
Abstract PDF(1009KB) icon1588 icon481
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By introducing the image analysis method,this paper proposed a new method of directly extracting the image text features from scalogram of continuous wavelet transform of rotor faults signals.Firstly,the rotor fault experimental rig was used to simulate unbalance,misalignment,rubbing and oil whirling faults,and faults samples were obtained;secondly,the scalograms of typical faults was analyzed,and the sensitivity of digital features of scalograms to faults was studied;finally,the integrated back propagation(BP) neural network was used to carry out the diagnosis based on digital features of scalogram.The results fully show the effectivity of the new digital features of scalogram put forward in this paper.
Experimental investigation into dynamic compressive mechanical properties of LY12 at high strain rates and high temperatures
XIE Ruo-ze, ZHANG Fang-ju, DENG Zhi-fang, LU Zi-xing
2009, 24(4): 799-803.
Abstract PDF(721KB) icon1657 icon438
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The dynamic mechanical properties of LY12 aluminum were studied experimentally by Hopkinson Bar of diameter 5mm with an automatic assembling system and heating system,within the range of temperature from 20℃ to 400℃ and strain-rate from 5×103s-1 to 1.4×104s-1.In the experiments,a shaper was used to eliminate the oscillation of high frequency in the incident signal and to improve the experimental precision of bar system.The experimental results show that the effect of temperature on dynamic properties of LY12 is not great at temperature lower than 200℃;on the contrary,the thermal softening effect is obvious at temperature higher than 200℃,exhibiting the decrease of flow stresses and linear harden modulus with increase of temperature,which is similar to linear harden materials.From the experiments,the dynamic properties of LY12 don't show strong sensitivity to the strain rates.
Probability analysis for the low cycle fatigue life of a turbine disk
GAO Yang, BAI Guang-chen, ZHANG Ying-li
2009, 24(4): 804-809.
Abstract PDF(1492KB) icon1979 icon505
Abstract:
The standard deviation of fatigue life increases with reduction of elasticity and plasticity strain components.A standard normal random variable μ and linear standard deviations σe and σp were introduced into Manson-Coffin equation,so the probabilistic model of fatigue life was established,in which four parameters were expressed as the functions of μ.The parameters of the probabilistic model were obtained by the heteroscedastic regression analysis method based on the low cycle fatigue(LCF) test data,the fatigue life probability analysis for the pinhole of a disk was achieved by this model,and the distribution of the fatigue life of the pinhole was obtained.The results show that the life with the reliability of 0.9987 is well consistent with the technical life of the disk based on test evaluation.This model is suitable for engineering application with its good precision.
Reliability sensitivity analysis for crack propagation of rotating shaft
SU Chang-qing, ZHANG Yi-min, MA Hui
2009, 24(4): 810-814.
Abstract PDF(311KB) icon1813 icon423
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Based on the Paris-Erdogan crack propagation model,the effect of random parameters on the crack propagation model was considered.The reliability model for crack propagation of rotating shaft in rotating machinery was presented by the crack length failure criteria.The first four moments of state function were derived from the random perturbation theory and the Kronecker algebra.The reliability of crack propagation was determined by using the stress-strength interference theory and the fourth moment method.The reliability sensitivity analysis of crack propagation was studied by using the matrix calculus theory and sensitivity technique.
New type of flutter solution based on flutter determinant
GU Ying-song, YANG Zhi-chun, WANG Wei
2009, 24(4): 815-818.
Abstract PDF(605KB) icon1623 icon481
Abstract:
A new flutter solution method was presented based on flutter determinant as a combination of the concept of flutter and matrix analysis theories.This method could locate the flutter boundary by directly computing indicators,which include the modulus of flutter determinant and the minimum module eigenvalue of flutter matrix.These indicators were proven equivalent with each other at the critical flutter point.The corresponding algorithm was developed for flutter solution by frequency sweeping approach.It was demonstrated by standard numerical examples that these two indicators give the same flutter results which agree well with those obtained by the p-k method.The information of coupled flutter modes can also be determined quantitatively from the flutter eigenvector at the critical flutter point.
Study of aerodynamic damping in cascade flow field
YU Hang, LI Lin
2009, 24(4): 819-824.
Abstract PDF(1618KB) icon1621 icon475
Abstract:
Based on the theory of aerodynamic damping,the appropriate damping model was established;with the help of moving meshes technology and in combination with the equation of equivalent mode aerodynamic damping ratio,the weakly coupled method was applied.In the researches of Rotor 37 transonic blade with excitation of the 1st bend mode,the 1st torsion mode and the 1st bend-torsion mode,the aerodynamic damping was gained.The pressure and the blade amplitude were considered.The results demonstrate that when the pressure ratio of input pressure and output pressure has been fixed,aerodynamic damping has a linear relation with the pressure;with a small blade deformation,the blade deformation has little influences on aerodynamic damping.
Orthogonal experimental investigation of geometry structure of grooved casing treatment
WU Yan-hui, ZHANG Hao-guang, CHU Wu-li, DENG Wen-Jian
2009, 24(4): 825-829.
Abstract PDF(499KB) icon1775 icon494
Abstract:
Nine kinds of circumferential grooved casing treatment structures were designed by the orthogonal experiment's requirement.Optimized experiments of the geometry structure of circumferential groove were performed on a single stage subsonic axial compressor with the nine kinds of circumferential grooved casing treatment structures at two rotor speeds.The results of orthogonal experiments show that the orthogonal experiments are successful.It is not necessary to test all casing treatment of possible combination of structural factors.The structural factors of casing treatment were forecasted successfully by analysis of the orthogonal experimental results with orthogonal analytic method and the subsonic rotor gains the best stall margin improvement with this kind of circumferential grooved casing treatment of possible combination of structural factors at two rotor speeds.
Computational and experimental investigation of plasma aerodynamic actuation based corner flow separation control in a compressor cascade
WU Yun, LI Ying-hong, ZHU Jun-qiang, ZHOU Min, JIA Min, SU Chang-bing, SONG Hui-min
2009, 24(4): 830-835.
Abstract PDF(988KB) icon1812 icon468
Abstract:
Plasma aerodynamic actuation based corner flow separation control in a compressor cascade was investigated computationally and experimentally.Three dimensional corner flow separation,which is formed over the suction surface and end wall corner of a compressor cascade blade passage,could cause significant total pressure loss even when the incidence is 0 deg.When the free stream velocity is 50m/s(corresponding Reynolds number is 223000),plasma aerodynamic actuation controls the corner flow separation effectively.When the actuation voltage and frequency are 10kV and 22kHz respectively,the maximum relative reductions of total pressure loss coefficient at 60% and 70% blade span are 13.83% and 10.74% respectively.So,increasing the actuation voltage or the number of electrode pair can enlarge the actuation strength and then improve the control effect.
Numerical and experimental study of air flow field of a core engine with by-pass duct
XIAO Min, ZHUANG Huan, GUO Xin
2009, 24(4): 836-842.
Abstract PDF(1530KB) icon1783 icon500
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The flow field of the core engine inlet was numerically calculated to solve the problem that the air flow measured in the air simulated test facility was inconsistent with ground test.The results show that the static pressure is fairly even in the section away from the front edge of the guide disk at a distance between 1.2D and 1.45D.The above-mentioned problems were attributable to the unevenness of the distribution of static pressure along radial direction.The numerical analysis was consistent with experimental results by adjusting the measuring section,and the above-mentioned problem was solved.
Wake-boundary layer interaction on low pressure turbine cascade blades
ZHANG Wei-hao, LIU Huo-xing, LI Wei, ZOU Zheng-ping
2009, 24(4): 843-850.
Abstract PDF(2049KB) icon1807 icon520
Abstract:
The wake-boundary layer interaction had been investigated numerically and experimentally,and a periodicity moving bar wake had been used to imitate the upstream wake.The study shows that the wake has a significant influence on the boundary layer of cascade: the transition on suction surface has taken place in advance;the separation has been remarkably suppressed;the load of low-pressure turbine cascade has been increased obviously.
Research on turbofan engine HP-compressor rotor-12 blade tip clearance control
LUO Fei-teng, SONG Wen-yan, LI Jian-ping, LI Qiang
2009, 24(4): 851-857.
Abstract PDF(1758KB) icon1818 icon464
Abstract:
Using CFD numerical simulation method,the single-passage flowfield of high pressure compressor rotor-12 with different tip clearances were investigated,and the corresponding total pressure ratio and efficiency were analyzed and compared,then a tip clearance value of optimal performance was obtained.The flowfield structure under optimal performance was discussed next.Finally,based on the finite element analysis software——ANSYS,the radial strain of rotor blade and disc,which are under coupled effect of thermal-structure,were estimated.The research results provide good reference for rotor blade tip clearance assembling and control.
Loss model application study in the through-flow inverse design approach for centrifugal compressors
MA Ping, TIAN Xiao-pei, SHAN Peng
2009, 24(4): 858-866.
Abstract PDF(2442KB) icon1959 icon514
Abstract:
The design scheme of quasi-3D streamline curvature through-flow inverse problem on S2,m stream surface needs to employ the non-viscous control equations with a loss model of the rotor,vaneless diffuser and stator.For developing a loss model in the centrifugal compressor through-flow design code,among several available centrifugal compressor 1D loss models established by previous papers in 1960s-70s,this paper,at first,selected a model proposed by Galvas M.R.as an original model.Secondly,It modified the original model to adapt to the modern quasi-3D computing techniques.Finally,It proposed and applied a new calling method of the loss model in the design process.The newly revised loss model can not only offer relevant losses at each blade row outlet according to various geometry and flow parameters,but also affect the integration of the velocity field through distributing the entropy increment to every computing station.Thus the new loss model satisfies the request of the through-flow method and reflects more closely to the flowfield in centrifugal compressors.The amount of losses estimated by the new model meets the pragmatic engineering requests.It will be verified further by engineering projects or experiments.
Power extraction method for acceleration and deceleration control law design of turbofan engine
CHEN Yu-chun, XU Si-yuan, LIU Zhen-de, TU Qiu-ye, YU Shou-zhi
2009, 24(4): 867-874.
Abstract PDF(1470KB) icon1836 icon482
Abstract:
A new and effective method——power extraction method(PEM),which is a simple,rapid and accurate tool of turbofan engine for acceleration and deceleration control law design,was proposed in this paper.Based on the steady-state performance computing model,the virtual power extractions of fan shaft and compressor shaft were introduced to make the steady-state operating points(line) move from normal operating points(line) at the constant corrected line of compressor,and the speeds of fan shaft and compressor shaft were maintained at given values.While taking into account the surge margin limit of compressor and fan,total temperature limit of turbine inlet and the flameout limit of combustor,an appropriate form was used to describe the acceleration and deceleration control law.In combination with the experiences of research and the development of turbine engines,the acceleration and deceleration control law of turbofan was designed rapidly and accurately.The computing results of the improved acceleration control law of some turbofan engine indicate that the VPEM is accurate and effective.
Aero-engine wavelet neural network PID control
LI Qiu-hong, XU Guang-hua, SUN Jian-guo
2009, 24(4): 875-879.
Abstract PDF(475KB) icon2132 icon469
Abstract:
An aero-engine proportion integration differentiation(PID) control method based on wavelet neural network on-line identification was proposed in this paper.The network structure was available with a three layers feed-forward neural network.The wavelet function was used as the activation function of the network's hidden layer.The network parameters were trained off-line.The derivative of the network's output to input was used as the engine model's derivative,and it was used to adjust the PID parameters on-line.The step response tests show that the settling time of PID control system adjusted by wavelet network is less than 2 seconds,and the steady state error is zero.The system works normally and steadily in the whole envelop.
AGA-LSSVR compensation for on-board self tuning model of aero-engine model
LU Feng, HUANG Jin-quan
2009, 24(4): 880-885.
Abstract PDF(1592KB) icon1747 icon485
Abstract:
The accuracy of aero-engine model-based fault diagnosis is directly influenced by the matching accuracy between the self tuning model and real engine.The parameter selection of support vector regression by adaptive genetic algorithms was proposed and applied to the real-time on-board self tuning model,thus effectively improving the matching accuracy.After analyzing the influences of parameter selection of support vector regression(SVR) on the performances of the SVR model,optimal parameters in the given region were selected in the search area by genetic algorithms.Different methods such as back propagation neural network(BP-NN),SVR,adaptive genetic algorithms-least square support veitor regression(AGA-LSSVR) were compared in the compensation of aero-engine model error;the results indicate that the proposed AGA-LSSVR is most feasible.
Application of boundary scan technique in electronic controller
DENG Zhi-wei, XU Kai, ZHANG Tian-hong
2009, 24(4): 886-891.
Abstract PDF(766KB) icon1647 icon448
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With the development of electronic engine controller(EEC) in terms of performance and integration,the traditional test method can not meet the demand.Boundary scan technique was proposed to solve the problem of testing the kernel electronic circuit of EEC.A testing platform including a testing adapter and a testing circuit was designed.Testing experiment for the circuit was carried out based on boundary scan.The testing experiment of principal instructions was accomplished.Fault injection to testing circuit by boundary scan chain was realized,which can be used to validate the performance of the built in test(BIT) functions of EEC.
Application of the wavelet network in fault diagnosis for some kind of aero-engine
JIANG Chuan-shang, FAN Ding, MA Chong
2009, 24(4): 892-895.
Abstract PDF(1116KB) icon2043 icon501
Abstract:
Advantages of wavelet network in model identification were analyzed.By combining wavelet analysis theory,a wavelet network algorithm was designed based on error back propagation algorithm.Through simulation test for a kind of aero-engine,wavelet can predict the output of engine accurately and in time,meanwhile the engine fault can be detected through error analysis by wavelet transform.
Power plant selection in a carbon constrained world the TERA(technoeconomic environmental risk analysis)
Stephen Ogaji, Pericles Pilidis, Vishal Sethi
2009, 24(4): 896-902.
Abstract PDF(778KB) icon1373 icon379
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There is an increasing concern that current trends of consumption of natural resources cannot continue.It is imperative that major targeted investments are made into economical and reliable environment friendly propulsion and power solutions.Many novel and promising concepts are being proposed.The selection of the best candidates to pursue for investment becomes a very difficult choice.A detailed TERA(techno-economic environmental risk analysis) framework is described here to quantify risks and to compare and rank competing schemes on a formal and consistent basis.This technique is based on detailed and rigorous thermodynamic representations of power plants.A layer of environment,economic,weather and other models to describe the appropriate local conditions is superimposed to this.The outcome is a techno-economic environmental risk analysis framework with appropriate detail of each power plant as applied to the appropriate conditions.The results for each concept can then be compared and contrasted to make appropriate selections.
Numerical simulation of flowfield of helicopter rotor and fuselage in forward flight based on unstructured embedded grid technique
YE Liang, ZHAO Qi-jun, XU Guo-hua
2009, 24(4): 903-910.
Abstract PDF(2291KB) icon2180 icon433
Abstract:
A numerical method has been developed to simulate the flowfield of the helicopter rotor,fuselage and the combination of them in forward flight.In this method,unstructured embedded grid technique was used to simulate the position transformation relationship between the rotor and its fuselage,the three-dimensional unsteady Navier-Stokes(N-S) equations were discretized by a second-order upwind finite-volume scheme and the lower-upper symmetric Gauss-Seidel(LU-SGS) scheme was employed in time-stepping.A new method was given to solve the problem of the "donor searching" when the space between the rotor and its fuselage was too narrow.Based on this model,the flowfield of the single rotor,fuselage and the combination of them were calculated,the comparisons of the calculated results with the experimental data indicate that the present method is very effective to analyze the helicopter flowfield in forward flight.
Research on scramjet integration design and numerical simulation
LI Jian-ping, SONG Wen-yan, ZHENG Ya-ming, LOU Fei-teng
2009, 24(4): 911-917.
Abstract PDF(1373KB) icon1881 icon454
Abstract:
Scramjet components were preliminarily designed in this paper according to concept of integration design.The flow-fields and performance of the two-dimension configuration were simulated using CFD methods,and the numerical results were found to agree well with experimental data.The flow-field and performance variation-trends of each component and the whole engine were analyzed and summarized,and the difference of engine performance under work and off-work state was compared.The research results can provide a reference for researches on integration design and performance of scramjet.
Impact of suction position on starting of hypersonic inlet
WANG Wei-xing, YUAN Hua-cheng, HUANG Guo-ping, LIANG De-wang
2009, 24(4): 918-924.
Abstract PDF(977KB) icon2083 icon443
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To research the ways of relieving inlet unstart phenomenon,the flow of a typical hypersonic 2-D inlet with different suction positions was analyzed in this paper.The result shows that,the inlet with suction can start easily,but the position of suction decides the impact.In the presence of suction in internal passage,the starting ability improves obviously with the growing suction flow,and the phenomenon is more obvious.The start ability improves finitely in the presence of suction in external pressure surface.The flow of suction can adjust with flow Mach number where suction with pressure changes largely before throat,and the start ability can be improved markedly.The impact on aerodynamic performance is that,the pressure efficiency increases with suction in external pressure surface,but declines with suction in internal passage and isolator.
Experimental study of inlet total-pressure distortion on four kinds of flat baffles
LI Liang, HU Jun, WANG Zhi-qiang, TU Bao-feng
2009, 24(4): 925-930.
Abstract PDF(698KB) icon1660 icon454
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To determine the reason why the single lunette-shaped flat baffle is used for inlet total-pressure distortion assessment regulated in GJB/Z64-2004(K),validity research was carried out experimentally for four kinds of flat baffles in the two-stage low-speed axial compressor,and complex distortion descriptor characteristic was compared in detail for each flat baffle.The experiment results indicate: outcomes adopting single lunette-shaped flat baffle tend to be conservative and rigorous,time-variant distortion descriptor and steady-state distortion descriptor are equivalent in the proportion of the complex distortion descriptor,and flat baffle experiment can bring great enough time-variant distortion.
Numerical simulation of gas-particle flow in nozzle of solid rocket motor
YU Yong, LIU Shu-yan, ZHANG Shi-jun, ZHANG Xia
2009, 24(4): 931-937.
Abstract PDF(2325KB) icon2322 icon468
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In order to study the influences of particles on gas flow in nozzle of solid rocket motor and the rules of particles flowing at different sizes,an Eulerian-Lagrangian approach was employed,Particle trajectory model was used for particle phase and compressible N-S equations were solved.MUSCL-Roe total variation diminishing(TVD) scheme with high order accuracy,and two-stage,time-stepping Runge-Kutta method with TVD character have been used to solve two-dimensional axis symmetric compressible N-S equations by a home codes "Solve2D".Simulation results indicate that the influence of particle primarily lies in throat and expansion segments of nozzle.Compared to pure gas flow,Mach numbers decreased along centerline,and the reduction became larger with smaller size particle.The gas temperature increased in two-phase flow,and the enhancement became higher with smaller size particles.The region without particles was smaller with smaller size particles.Big size particles had serious collision with wall of convergent region,and the region without particles was larger.
Basic parameters analysis of first stage engine system for heavy lift vehicle
LI Xiang-ning, LIU Yu
2009, 24(4): 938-944.
Abstract PDF(486KB) icon1808 icon477
Abstract:
The structure and basic parameters of propulsion system for existing heavy lift launch vehicles were analyzed.The structure and task requirements were proposed to meet the manned lunar-landing demand.Considering the performance,economics,technical difficulties and working reliability,a scheme of the first stage engine system for heavy lift launch vehicle was proposed,including the thrust level,propellant type and engine cycle.System simulation models were established for 9 model engines using the object-oriented sequential analysis method,and the maximum chamber pressures and balanced system parameters were computed.The influence of chamber pressure and mixture ratio on the engine performance was analyzed.Based on integrative analysis,4 500～5 000 kN liquid oxygen/ kerosene engine system of stage combustion cycle with oxygen-rich preburner is preferred.
Fuzzy prediction of rolling bearing friction torque using information poor system theory
XIA Xin-tao, JIA Chen-hui, WANG Zhong-yu
2009, 24(4): 945-950.
Abstract PDF(1521KB) icon1624 icon473
Abstract:
Friction torque of rolling bearings with uncertain fluctuation belongs to a poor information system,wherein both probability distribution and trend are unknown.This impedes small sample analysis and overall understanding of friction torque of rolling bearings.For this end,empirical probability density function and fuzzy prediction model of rolling bearings for space applications were proposed,and upper boundary of mean friction torque and maximum friction torque were predicted,starting from small samples based on fuzzy-set theory.Experiments on friction torque parameters of two kinds of rolling bearings HKTA and HKTB show that,at the 99%～100% confidence level,errors between results of prediction and experiment are very small,maximum absolute error is only 0.081 1 unit,and maximum relative error is only 10.165%,which could satisfy the requirements of space engineering.
Dynamic virtual simulation of deep groove ball bearing:based on elastohydrodynamic lubrication theory
LI Chang, SUN Zhi-li
2009, 24(4): 951-956.
Abstract PDF(1908KB) icon1843 icon496
Abstract:
Practical researches showed that lubrication oil slick produced a great effect on bearing gluing,scuffing and contact fatigue.But,all the previous bearing simulations neglected its existence,causing obvious errors.In this paper,a new simulation method was proposed by assuming that bearing rings are rigid firstly.Based on Hertz contact theory,mechanical ball bearing model under radical and axial feed was set up with quasi-dynamics.Using Newton-Raphson method as a key calculation tool when solving the model,contact load and deformation were obtained,contact stiffness between each ball and inner ring,or each ball and outer ring were calculated.Considering the effect of lubrication oil slick on bearing dynamic characteristic on the basis of elastohydrodynamic lubrication(EHL) theory,oil slick rigidity was obtained.A new concept of equivalent synthetic rigidity was presented and solved.In view of above mathematical computation,exact dynamic simulation on ball bearing was carried out using ADAMS software.

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