交通运输工程学报

Droplet size and velocity distribution function in sprays based on maximum entropy principle

CAO Jian-ming, HE Jian, LI Xian-guo

Abstract: A droplet size and velocity distribution function was theoretically derived based on the maximum entropy principle and the momentum conservation law.The numerical calculations for the function on the droplet size and velocity distribution of pure diesel and L30(mixed liquefied petroleum gas(LPG)/diesel fuel in a mass ratio of 30 per cent LPG) were done, and a comparison analysis of the spray characteristics between diesel and L30 was conducted.The result shows that because of the influence of flash boiling injection, the peaks of the droplet size distribution curve of L30 are evidently higher than those of diesel, the curve and its peaks move toward smaller droplet diameters region, which indicates that the droplets produced by injecting L30 are smaller than those of diesel; the peaks of the velocity distribution curves of L30 are higher than those of diesel, and locate a lower velocity region, which shows that the droplet number of lower speed is more than that of higher speed for the L30.The size-velocity(D-u) contour maps of diesel and L30 obtained by the droplet size and velocity distribution curves shows that smaller drops occupy a wide velocity space, and lower speed droplets have a wide size space.The size and velocity distribution of L30 converges faster than that of diesel, which indicates that the smaller size and lower velocity drops of L30 are more than those of diesel, and the spray quality of L30 is better than that of diesel.More>

2008, 8(5): 1-8.

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Work strategies of torque converter for vehicle with continuously variable transmission system

HE Ren, XIA Jing-jing, ZHANG Yong, WU Hai-xiao, HOU Su-li

Abstract: In order to improve the operating fuel economy of torque converter for vehicle with continuously variable transmission (CVT) system, the optimal lock-up and unlocking conditions were confirmed.To furtherly improve the work efficiency of torque converter in unlocking stage, PID controller was designed, so that engine and torque converter worked in optimal economy region by adjusting the speed ratio of CVT.To decrease the impact during the lock-up process of torque converter, the control strategies of lock-up clutch engagement were put forward according to the principles of stabilizing engine rotation and optimizing the performance of impact and sliding friction work, and the fuzzy controller with two inputs of impact degree and rotate speed difference was designed.The experimental result under two kinds of different lock-up states shows that the 1.92 s in quick acceleration is bigger than the 1.38 s in slow acceleration, the engagement time is prolonged, so the control measures can ensure the engaging smoothness of torque converter and stabilize engine rotate speed.More>

2008, 8(5): 9-14.

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Wheel-rail dynamic interaction characteristic on high-speed railway

WANG Kai-yun, SI Dao-lin, CHEN Zhong-hua

Abstract: In order to reveal the wheel-rail dynamic interaction characteristic on high-speed railway, wheel-rail geometric relationship and the random vibration properties of running safety and comfort were carried out by using vehicle-track coupled dynamics theory, and wheel-rail vibration was taken into account.Analysis result shows that there is obvious characteristic of wheel-rail contact geometric relationship when a train passes though curved track at high speed.At the speeds ranging from 160 to 300 km·h^-1, the sensitive wavelengths of rate of wheel load reduction and car body vibration acceleration are respectively in the scopes from 1.0 to 2.5 m and from 40 to 50 m.So it is benefit to improve the running safety and comfort of high-speed train while controlling the irregularity with the sensitive wavelengthes.More>

2008, 8(5): 15-18.

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Influence of wheel-diameter difference on running security of vehicle system

CHI Mao-ru, ZHANG Wei-hua, CENG Jing, JIN Xue-song, ZHU Min-hao

Abstract: The running state of the bogie with wheel-diameter difference was analyzed, and a dynamics model of vehicle was set up.As an example of a high-speed vehicle running on the tangent tracks with Germany low-disturbing spectrum at 300 km·h^-1, the influence of wheel-diameter difference on the running security of vehicle was analyzed by simulation, and the influences of the same phase's and opposite phase's wheel-diameter differences on the running security were compared.Analysis result shows that all of wheel-diameter differences affect the running security of vehicle system, the running security is getting worse with the increase of wheel-diameter difference, the opposite phase's wheel-diameter difference has larger influence, and the same phase's wheel-diameter difference has less influence.So in order to ensure the running security of vehicle system, the wheel-diameter difference should be minished by all means, especially, the opposite phase's wheel-diameter difference should be strictly controlled under permitted scope.More>

2008, 8(5): 19-22.

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Modelling method for reliability of traction power supply system

XIE Jiang-jian, WU Jun-yong, WU Yan

Abstract: Using a fitting method based on genetic algorithm (GA), a reliability modelling method of traction power supply system based on Weibull distribution model was proposed.Southern Zhengzhou traction power supply system (TPSS) on Jing-Guang railway was taken an example, its real failure ratio data for 14 years were analyzed, the reliability models of all components of the system were established by the method, based on these, the reliability model of whole system was analyzed by using binary decision diagram (BDD) algorithm, and the life-span of the system was calculated.K-S and W2 goodness-of-fit test result shows that the modeling method is feasible.The computation result of the life-span indicates that the life-span of the system is 3.116 years, the life-span of catenary system is 3.215 years, the reliability of the system depends on the reliability of catenary system to large extent.More>

2008, 8(5): 23-26.

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Stress spectrum analysis and fatigue life prediction about wheel axle of high-speed power car

ZHAO Li-hua, ZHANG Kai-lin, ZHANG Hong-jun

Abstract: Combining the dynamic response of vehicle under the excitation of track spectrum with fatigue strength theory, the wheel axle of China Star high-speed power car was taken as example, the nonlinear dynamics model of the power car was set up, the running property of vehicle on typical railway was simulated, and the random loads acted on vehicle wheelsets were obtained.Based on the nonlinear random cyclic constitution of the axle material, the finite element model of the wheelset was established, the stress time history of key region of the wheelset under the random loads was calculated, and the stress spectrum of hazard sections of the axle was obtained by statistical analysis.Using fracture mechanics theory and accumulative damage theory, the fatigue life of the axle was predicted, and its reliability was analysed.When the reliability was 0.9, the fatigue life was 16 years.More>

2008, 8(5): 27-32.

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Gas path fault prognosis of aeroengine based on support vector machine

WANG Xu-hui, HUANG Sheng-guo, SHI Ding-hao, SHU Ping

Abstract: In order to reality the online forecast of aeroengine gas path fault, the protocol and content of the gas path parameters' report in aircraft communication addressing and reporting system(ACARS) were analyzed, and an online forecast model of the parameters based on support vector machine(SVM) algorithm was established.A real-time processing system of aeroengine report was built by using portable air-ground data link transceiver for obtaining the training samples of the model.Final prediction error(FPE) principle was suggested to optimize the embedding dimensions of the samples, and the phase spaces of the samples were reconstructed.An adaptive grid search algorithm was put forward to optimize the parameters of the model, and the model was linked to route plane by using ACARS.Forecast result shows that the relative forecast errors of low-pressure compressor rotor speed, high-pressure compressor rotor speed, exhaust gas temperature and fuel flow are 2.5%, 2.1%, 1.9% and 2.3% respectively, so the model is feasible.More>

2008, 8(5): 33-37.

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New performance evaluation method of grab ship unloader

WANG Jian, YAO Zhen-qiang, BAO Qi-fan, ZHU Jian-long, LEI Xin-hua, WANG Xiao-ping

Abstract: The productivity calculation methods of different grab ship unloaders were analyzed, the advantages, disadvantages and applicability were compared, a new performance evaluation method was presented based on mechanical performance calculation approaches.The validity rules of testing record were established, some modified coefficients were defined to eliminate the influence of uncertain factors such as material attributes and operation conditions.Calculation result shows that the rating productivity of automatic operation mode is increased by 3.12% than that of manumal mode, and actual productivity is increased by 7.97%, so the evaluation result is acturate, and the new method can easily compare the automation degrees of different manipulation modes.More>

2008, 8(5): 38-43.

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Influence of gradations on aggregate segregations of asphalt mixtures

PENG Yu-hua, SHA Ai-min, LIANG Han-cheng, LEI Yu

Abstract: In order to compare the different degrees of the aggregate segregations for asphalt mixtures with different gradation types during construction, seven kinds of asphalt mixtures with typical gradation types were produced by adjusting the scale of hot bunker at mixer plant, and the granulometric composition conditions at different positions on cross section after spreading were analyzed.After the mixtures were rolled and molded, their construct depthes were measured at different positions on cross section, and their numerical characteristics were evaluated.Analysis result shows that, on the same condition, the gradations that influence the degrees of the aggregate segregations from large to small were in the following order: counter S type, discontinuous type, the micro bow type that is over the ultimate density curve, S type, 0.45 capital ultimate density curve, the gradation with superior middle particle size, the micro bow type that is below the ultimate density curve.More>

2008, 8(5): 44-48.

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Heat transfer model and solution of microwave hot recycling for asphalt pavement

SUN Tong-sheng, SHI Jin-fei, ZHANG Zhi-sheng

Abstract: In order to achieve the temperature field of microwave hot recycling for asphalt pavement, heat transfer form was analyzed based on heat transfer theory, the corresponding 3D unsteady heat transfer model was built, boundary conditions were studied, convective heat transfer coefficient and radiation heat transfer emissivity were solved, the strength of internal heat source was studied according to energy conservation principle, and transformation between electric field and thermal field was realized, the numerical solution of heat transfer model was researched by adopting alternation direction explicit (ADE) scheme, the mathematic models of heat transfer boundary conditions were established by fitting experimental temperatures, and visualized numerical solution was obtained by simulation.Computation result shows that the temperatures of asphalt mixture in most region approach to 70 ℃ after heating for 450 s, reach about 80 ℃ after heating for 600 s, and reach about 110 ℃ rapidly after heating for 750 s; heat transfer is nonlinear and the heating time must be chosen accurately to guarantee repair quality.More>

2008, 8(5): 49-53.

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Strength and mechanic property of expansive soil

LI Zhen-xia, WANG Xuan-cang, CHEN Yuan-zhao, MAO Yuan

Abstract: Strength, over consolidation and compression index of expansive soil were studied by triaxial test and confined compression test, the relationship between swell-shrinking index and shear strength was set up, the influences of structural feature, mineral composition and outside factors on deformation and strength property were analyzed.Study result shows that expansive soil has the property of over consolidation, shear strength increases with the over consolidation, the better the fissures develop, the higher the compressibility is, the weaker the over consolidation is, and the smaller the shear strength index is.The variation extents of shear strength index are put forward, cohesion changes from 19.8 kPa to 25.5 kPa, and internal friction angle changes from 10° to 19° under consolidated-drained compression test; cohesion changes from 23.0 kPa to 35.3 kPa, and internal friction angle changes from 3° to 14° under consolidated-undrained compression test; cohesion changes from 37.0 kPa to 55.0 kPa, and internal friction angle is 0° under unconsolidated-undrained compression test.More>

2008, 8(5): 54-60.

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Partial factor optimization of stable reliability design for reinforced embankment

QUE Yun, HU Chang-bin

Abstract: In order to perfect the limit state design method of reinforced embankment, partial factors of stable reliability design was analyzed, the statistic results and probability distribution model of uncertainty coefficients of random variables such as filler density, cohesion, angle of internal friction, vehicle load, tensile strength of geosynthetics, pseudo-friction coefficient and geometric parameters of embankment, were obtained preliminarily based on statistical analysis of field data and literature material.According to the least square principle of structure resistance, partial factors of resistance, partial factors of dead load, partial factors of live load of reinforced embankment were optimized in four failure modes including the fracture of geosynthetics, pullout of geosynthetics, basal slide and global slide.Calculation result indicates that resistance is larger than sum of dead load and live load under four failure modes, and safe factors can meet standard requirements, so the optimized partial factors are reasonable.More>

2008, 8(5): 61-66.

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Numerical analysis of application for pile-supported reinforced embankment in subgrade widening engineering

QIAN Jing-song, LING Jian-ming

Abstract: In order to investigate the mechanical behavior and treatment effect of pile-supported reinforced embankment under load in subgrade-widening engineering, a 3D finite element model was established, foundation soil was simulated by using soil-water coupling element, geogrid was simulated by using 3D membrane element, the changing-status non-linearity of pile-soil interface was considered by surface-to-surface contact elements, and the working mechanism of pile-supported reinforced embankment was validated by soil arching effect, tensioned membrane effect of geogrid and pile-soil interaction.Analysis result indicates that the maximum tension in geogrid occurs at the edge of pile cap under the toe of existing slope, and geogrid tension gradually decreases from the edge; pile-supported reinforced embankment can reduce the differential settlement of foundation from 50.0 cm to 8.3 cm, excess pore pressure from 63.7 kPa to 11.0 kPa, and avoid the appearance of reverse slope at the top of old embankment.Meanwhile, there are significant settlement and excess pore pressure at the foundation under the old embankment, so it is important to treat the foundation under the old highway slope.More>

2008, 8(5): 67-71.

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Data processing model of highway landslide monitoring network based on GPS

YAO Wan-qiang

Abstract: The data processing model based on station orthogonal coordinate system for 3D GPS highway subsidence monitoring network was analyzed and derived, a mathematical model based on clustering analysis method was put forward to test the relative stability of quasistable points(or datum points), and a quasistable adjustment method in the data processing course was proposed to compute minitoring data adjustments.A software system of data processing for the network was developed by using VC++, and the adjustments of three periods observation data of a highway subsidence from the network were computed by using the software.Calculation result shows that the middle square error of the plane coordinate is 1 mm, and the plumb one is 2 mm, so the mathematical model is more suitable for the data processing in the network.More>

2008, 8(5): 72-75.

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Free vibration characteristics and experiment study of composite box girder with corrugated steel webs

ZHANG Yong-jian, HUANG Ping-ming, DI Jin, ZHOU Xu-hong

Abstract: In order to accurately calculate the vibration frequency of composite box girder with corrugated steel webs, the formula about the natural frequencies was deduced based on energy variational principle, and the analytical solution was obtained according to the effects of shear lag and shear deformation.The natural frequencies of a model were tested, and were compared with the results of simply beam theory, the theoretical formula and 3D finite element model.Comparison result shows that the effects of shear lag and shear deformation to vibration frequency are obvious, the frequencies of composite box girder with corrugated steel webs will decrease when the effects are taken into consideration, and the effects increase sharply with the increase of frequency order, so the effects can not be neglected in the frequency calculation.More>

2008, 8(5): 76-80.

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Traffic volume conditions of setting diagonal ramp

LI Ai-zeng, WANG Wei, LI Wen-quan

Abstract: In order to get the traffic volume conditions of setting diagonal ramp, time headway distributions on mainline outer lane in merging area were analyzed, gap acceptance theory and piecewise integral method were used, the adaptive traffic volume model for diagonal ramp vehicles driving into mainline was established.Considering the right-turn traffic volume driving into diagonal ramp and its time headway distributions, adaptive left-turn traffic volume models were developed based on gap acceptance theory, and the constraint conditions of left-turn and right-turn traffic volumes driving into diagonal ramp were obtained.Analysis result indicates that traffic volume conditions of setting diagonal ramp are related to mainline traffic volume, ramp traffic volume, length of acceleration lane, interval status of time headway distributions on mainline outer lane in merging area, critical gap and follow-up time of merging vehicles, and left-turn and right-turn traffic volumes driving into diagonal ramp.More>

2008, 8(5): 81-85.

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Constrained Kalman filter combined predictor for short-term traffic flow

NIE Pei-lin, YU Zhi, HE Zhao-cheng

Abstract: In order to avoid the unstableness of single traffic flow prediction model, a constrained Kalman filter combined(CKFC) predictor was proposed for short-term traffic flow, the weight of each single predictor was used as state variable for the predictor, traffic flow was used as measurement variable, CKFC predictor's result was a weighted sum of single predictor, the weights were decided by constrained Kalman filter dynamically, and CKFC predictor was tested using traffic flow data collected on Guangshen freeway.Analysis result indicates that CKFC predictor is better than or at least as good as the optimum single predictor, it is not influenced by poor predictor and has high robustness.More>

2008, 8(5): 86-90.

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Filling method of missing data for traffic flow based on rough set theory

WANG Xiao-yuan, WU Fang, PO Ji-nan

Abstract: In order to solve the problem of missing data detected from traffic detectors, the algorithm of filling missing data was proposed based on rough set theory, information system was constructed by the detected traffic flow data, distinct matrix was extended and analyzed repeatedly, the missing data of information system were filled, the algorithm was validated with the data of Southampton.Analysis result shows that, at the same period, when only one attribute datum is missed, the filling precision based on rough set theory is higher, the absolute relative error is lower, and basically keeps between 0 and 5%;when different attribute data are missed simultaneously, the filling precision is lower, and the absolute relative error is up to 20%;when all attribute data are missed, the filling is unable to realize, so the algorithm is very effective to fill a spot of missing data.More>

2008, 8(5): 91-94.

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Design method of forecast system on passengers up and down buses

MA Rong-guo, LIU Hong-ying, LIANG Guo-hua

Abstract: In order to improve the operating efficiency of bus and the security of waiting passengers, application cost and working convenience were considered, the concept of forecast system on passenger up and down buses was defined, the benefit of forecast system was analyzed, the design process of the system was put forward based on riding information put out by passengers and received by drivers, the method to calculate the radius of forecast system was given, the way to realize the function of the system was researched.Application result indicates that the average operation efficiency of buses increases by 43.1人·s at every traffic station, so the benefit is obvious, the system is feasible.More>

2008, 8(5): 95-99.

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Dynamic signal timing algorithm at single-point intersection based on queuing condition

LI Ming-li, ZHAO Xiang-mo, ZHANG Li-chuan

Abstract: The queuing states in the green end were taken as objective, the dynamic signal timing at single-point intersection under the control of two-phase signal was studied, a queuing model was built according to the queuing and discharging process, and the effects of signal cycle, split and arrival ratio on the queuing states were analysed.A signal timing simple algorithm following the fluctuation of arrival ratio was put forward when two phases were in little under-saturation queuing states, the cycle was calculated according to the total ratio of flow volume, and the split of main phase was adjusted depending on the higher ratio of flow volume.Simulation result indicates that the cycle slowly changes both phases queuing conditions in the same direction, the split changes them in the reverse direction, and the arrival ratio only alters the queuing conditions of corresponding phases.When saturation flow rates are 0.50 pcu·s^-1, the times of yellow and green former losses are 4 s, and the arrival ratio varies from 0.10 to 0.26 pcu·s^-1, two phases are in little under-saturation queuing states, so the algorithm is effective.More>

2008, 8(5): 100-103.

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Multi-flight and multi-luggage claiming model

LU Xun, ZHU Jin-fu, TANG Xiao-wei

Abstract: In order to resolve the overcrowding state of luggage claiming area at hub airport terminal and improve the efficiency of luggage claiming, the limitation of static luggage claiming model was analyzed.Based on single-flight and single-luggage claiming dynamic model, two kinds of actual situations were considered, which one luggage turntable could handle the luggages of several flights at the same time, and several pieces of luggages belonging to one passenger did not always arrived at the luggage turntable of destination airport at the same time, a multi-flight and multi-luggage claiming model was build by math deduction, and the overcrowding states with different demands were analyzed.Analysis result shows that there is about 9 min passenger density over 1 passenger per meter under the single-flight and single-luggage condition, which is below E class service level, there is about 8 min passenger density over 0.6 passenger per meter under the multi-flight and multi-luggage condition, which is below C class service level, so the new model is more efficient.More>

2008, 8(5): 104-108.

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Vehicle routing method of hands-free travel system based on spatial character

LI Lin-bo, YANG Dong-yuan

Abstract: In order to improve the efficiency of initial solution for vehicle routing problem(VRP), the spatial characters of demand points for hands-free travel system in Shanghai World Expo were studied under uncertainly conditions.Vehicle routing method was put forward based on the spatial characters, and the Single-LINkage(SLINK) clustering method for the spatial characters and the estimation method for the clustering analysis result were built.Computation result indicates that the Single-LINkage clustering method can get the total distance of 583 for the initial solution, and the SWEEP method gets 595 when the demand points are clustering, so the analysis of spatial character for demand points contributes to the last solving for the VRP under the uncertainly conditions.More>

2008, 8(5): 109-113.

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Local search alogrithm of dynamic vehicle routing problem with time window

LIU Xia, QI Huan

Abstract: In order to effectively solve dynamic vehicle routing problem with time windows, the mathematical model was established, the planning period was cut into slices, and the dynamic problem was partitioned into a series of static sub-problems, the initial solutions were constructed by intertion method.Three inter-route local search approaches including relocation, exchange and 2-opt*, and two intra-route local search approaches including 2-opt and Or-opt were introduced, different approaches were combined to improve initial solutions.The influences of arrival time, distribution of geographical location and time window range on route selection were analyzed, and the solving results of standard example were compared.Result shows that relocation method is the best, 2-opt* is the second and exchange is the worst for inter-route local search, 2-opt is better than Or-opt for intra-route local search, and the vehicle number, traveling distance and delay of all routes decrease with early requests, concentrated customers and wide time windows.More>

2008, 8(5): 114-120.

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Risk analysis on Bohai Strait Cross-sea Channel investment based on analytic hierarchy process

WU Ai-hua, ZHANG Fang-fang, LI Tian-lu

Abstract: In order to evaluate the risk of Bohai Strait Cross-sea Channel, analytic hierarchy process(AHP) was applied, the factors of impacting the project were decomposed, the various factors were ranked based on the risk degree to the project, and several key factors for the project were studied.Analysis result indicates that the factors of impacting the project from large to small are geographical conditions, technological level, accidents, capital, resource use, policy and legislation.Four ranks are divided based on the risk degree to the project, the risk of submarine geology conditions is the highest, the risks of disaster prevention and rescue system and lighting system in tunnel project are higher, the risks of flood prevention facilities and tunnel monitoring system are lower, and the risk of plan function is the lowest.Last the results are explained, and the planners and investors of the project can carry out the risk management according to the result.More>

2008, 8(5): 121-126.

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2008 Vol. 8, No. 5

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