Journal of Chongqing Jiaotong University(Natural Science)

Hierarchical Scheduling Strategy for Free-Floating Bike-Sharing

GUAN Hongzhi, LU Sheng, SONG Maocan

2020, 39(02): 1-7. DOI: 10.3969/j.issn.1674-0696.2020.02.01

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In view of the characteristics of free-floating bike-sharing (FFBS), such as chaotic parking, high failure rate and uneven distribution of time and space, a hierarchical scheduling strategy was proposed, in order to solve the problems of low efficiency and high cost in scheduling work. The scheduling area was divided into road-layer and zone-layer, and different types of scheduling vehicles were used to complete the collection of faulty bikes, the collection and delivery of normal bikes. Taking the minimum time cost as the optimization objective, considering the capacity constraints and supply constraints of scheduling bikes, a static scheduling model with multiple bike trips was established. The case study shows that the proposed model can effectively guide the optimal adjustment of scheduling path; and the scheduling cost analysis of three kinds of strategies also shows that the proposed hierarchical scheduling strategy has obvious advantages in the economic cost.

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Bus Flexible Dispatching System in Off-Peak Hours of Urban Periphery

LU Baichuan1,2, HE Xiangyi1, HU Song1, SHU Qin1

2020, 39(02): 8-15. DOI: 10.3969/j.issn.1674-0696.2020.02.02

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Based on the traffic characteristics of the residents around the city and the contradiction between the bus operation cost and the passenger waiting time, a bus flexible scheduling system based on the Internet technology and the idea of network car-hailing was proposed. The operation mode of the flexible bus scheduling system was expounded, and the overall structure, module function and workflow of the flexible bus scheduling system were designed. The departure time of off-peak hours was determined by constructing a flexible departure interval function based on the number of passengers ordered, and the shortest path of response time and the comprehensive benefits of passengers and buses were calculated by using the flexible scheduling decision support model. Finally, taking180 road bus in Chongqing as an example, the comparison analysis between three appointment ratios of flexible scheduling mode and traditional operation modes was carried out. It is concluded that the flexible bus scheduling system can reduce the waiting time of passengers and the operation cost of public transportation.

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Multi-license Plate Location Based on Improved Two-Dimensional Discrete Wavelet Transform

LING Xiang, HUANG Bang, HUANG Liangjun, LAI Kun

2020, 39(02): 16-21. DOI: 10.3969/j.issn.1674-0696.2020.02.03

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Aiming at the problem of extracting multiple license plates from complex background, an improved two-dimensional discrete wavelet transform was proposed to locate multiple license plates. Firstly, according to the characteristics of wavelet multi-scale decomposition, the two-dimensional discrete wavelet transform was applied to the image to obtain a series of low-frequency wavelet information maps. A linear difference with the original image was made to obtain the detailed features of the license plate characters. Secondly, according to the difference between the characters of license plate and the background in the binary image, the gray level jump was generated, the line position of license plate in the image was roughly located, and the search range of license plate location was narrowed. Finally all license plates were accurately located by using color and shape features, in the small range image of rough location. The research results show that compared with the traditional two-dimensional discrete wavelet transform image, the improved two-dimensional discrete wavelet transform image has nearly doubled the gray level mean value, standard deviation and average gradient, which can effectively obtain the edge information of the original image to narrow the position of multiple license plates. The multi-license plate location method can achieve an accurate positioning rate of 98.96%, with an average time of 328 milliseconds. It can be seen that the proposed method can accurately and quickly locate multiple license plates.

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Traffic Capacity Calculation Method of Urban Mixed Entrance Lane

MA Yingying, LU Siyuan, QIN Xiaoran

2020, 39(02): 22-29. DOI: 10.3969/j.issn.1674-0696.2020.02.04

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In view of the serious problem of mixed traffic on urban roads, the calculation method of saturated headway and capacity of the entrance road with mixed straight left vehicles and mixed small vehicles and buses was studied, through the investigation and analysis of the traffic operation characteristics of signal controlled intersection on urban road. In order to get the traffic capacity calculation model of the mixed entrance lane of urban intersection, firstly, the traffic investigation and data collection of urban road signal controlled intersection were carried out; at the same time, the characteristic analysis of the headway of the mixed entrance lane was carried out to obtain the characteristic parameters of the fleet on entrance lane. Secondly, the analysis models of the mixed headway of the straight left vehicles and the bus and car were established respectively. Thirdly, the calculation method of the capacity of the mixed entrance lane based on turn ratio and bus ratio was established. Finally, the relationship among capacity, bus ratio and turn ratio was analyzed, combining with case study. The research results show that: the error between the morning and evening peak results calculated by the proposed method and the measured values is 1.5% and 6.95% respectively, which is smaller than that calculated by methods of CJJ 37-1990 “Code for Design of Urban Roads” and “Highway Capacity Manual”. The proposed method greatly improves the accuracy of the calculation results and may provide basis for the control and management of intersections.

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Accessibility of Public Transport of High-Speed Railway Station in Satellite City

GUO Zizheng1,2, LI Jianqiang1,2, CHEN Ruiya3

2020, 39(02): 30-34. DOI: 10.3969/j.issn.1674-0696.2020.02.05

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It is the key problem that whether the accessibility of the high-speed railway station in satellite city can be accurately analyzed to evaluate the distribution ability of the public transportation system to the high-speed railway passenger flow and optimize the routes and stations. In order to solve this problem, based on the passenger flow characteristics of high-speed railway in satellite city, a calculation model of public transport accessibility from “spot” and “panel” was proposed, which calculated and analyzed the public transport accessibility of high-speed railway station from “spot” and “panel”, in order to accurately locate the shortage of public transport stations and routes. Finally, the above methods were verified in the case of GIS simulation technology, and the analysis methods and results were given. The results show that the proposed model can accurately locate the local and overall deficiencies of the public transportation system, and provide the optimization direction of the system, which verifies the rationality and practicability of the proposed method.

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Multi-trip Vehicle Routing Problem Based on the Improved Difference Variable Neighborhood Search Algorithm

SONG Qiang1,2

2020, 39(02): 35-42. DOI: 10.3969/j.issn.1674-0696.2020.02.06

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Aiming at multi-trip vehicle routing problem, the optimal solution was successively found out by standard differential evolution-encoding and decoding-fitness calculation-variable neighborhood local search procedure, and an improved difference variable neighborhood search algorithm was established. The proposed algorithm adopted the encoding and decoding method based on roulette, and overcame the shortcomings of the standard differential evolution algorithm which couldnt be applied to the discrete problem. At the same time, the depth development ability and optimization performance of the standard differential evolution algorithm were further strengthened by using the variable neighborhood optimization technique. Finally, the simulation results were compared by the random function in MATLAB, which proved the superiority of the proposed algorithm in solving the multi-trip vehicle routing problem.

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Operation of New High-Speed Sleeper EMU Train and Setting of 4-Hour Comprehensive Maintenance Window

ZHANG Lei1, XIONG Jianchun1, TANG Yixiong2, ZHAN Shuguang2,3, PENG Qiyuan2,3

2020, 39(02): 43-49. DOI: 10.3969/j.issn.1674-0696.2020.02.07

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In view of the serious conflict between night train operation and comprehensive maintenance window of high-speed railway, which severely restricted the number of night train operation and comprehensive maintenance quality, a linear programming model for the integration of train diagram and comprehensive maintenance window was established, with the goal of minimizing the total travel time of high-speed sleeper EMU train. The model was solved by CPLEX, and the coordination scheme between the train diagram and comprehensive maintenance window setting of the new high-speed sleeper EMU train suitable for the opening of 4-hour comprehensive maintenance window was solved, which was based on the existing train diagram of Beijing-Guangzhou high-speed railway. The results show that the new high-speed sleeper EMU train can ensure that the comprehensive maintenance window can be opened for 4 hours in each section of Beijing-Guangzhou high-speed railway after running night train, and meet the requirements of comprehensive maintenance quality for daily operation.

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Adjusting Method for Anchor-Span Cable Force of Steel Truss Suspension Bridge in the Cabling Phase

LIU Jiakui1, LUO Hao1, DU Bin2

2020, 39(02): 50-54. DOI: 10.3969/j.issn.1674-0696.2020.02.08

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In order to research the method of adjusting the anchor-span cable force of the steel truss suspension bridge in the cable-forming stage, the existing problems in the control of the cable force of the suspension bridge were analyzed and the cable force control countermeasures were put forward. The results show that in the stage of cable strand erection, the linear control of side span is the main method. After the cable strand is erected, the support frame of splay saddle shall be released. The redistribution of cable force and the movement of splay saddle in the process of adjustment may not be considered when the force of anchor-span cable is adjusted after the main cable is erected. According to the elastic theory, the deviation of cable force can be transformed into the adjustment of cable strand length, which can quickly complete the adjustment of cable force and ensure the error to meet the monitoring requirements.

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Experiment Study for Temperature Sensing Characteristics of Intelligent Steel Strand

XU Xiangfeng1,WANG Xin1，LIU Jiaqi2, LI Guanghao1,ZHANG Feng2

2020, 39(02): 55-61. DOI: 10.3969/j.issn.1674-0696.2020.02.09

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Aiming at the influence of FBG temperature on cross sensitivity, a water bath circulating device of intelligent prestressed steel strand was designed and manufactured. The water bath cycling test was carried out on steel strand under stress-free condition, and the temperature compensation model of intelligent prestressed steel strand was studied. The water bath cycling test of intelligent prestressing steel strand in stress state was carried out. The wavelength test results of the optical fiber sensor modified by the temperature compensation model were obtained and compared with the test results of the vibrating string pressure sensor, which verified the validity of the temperature compensation model of the intelligent prestressed steel strand. The research results show that the temperature sensing coefficient of FBG intelligent steel strand is 0.0226 nm/℃, which is about 2.3 times of that of bare fiber. The expression of the relationship between the change of optical fiber wavelength and the change of temperature and the expression of the relationship between the change of optical fiber wavelength and the change of tensile force are obtained. The test results of intelligent prestressing steel strand after temperature correction are consistent with those of vibrating string pressure sensor, and the correlation coefficient is 0.97.

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Value of Time Step in the Simulation of Fluctuating Wind Field by Weighted Amplitude Wave Superposition Method

ZHANG Junfeng, TU Baozhong, LIU Qingshuai, YANG Junhui, LI Huizhi

2020, 39(02): 62-68. DOI: 10.3969/j.issn.1674-0696.2020.02.10

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In order to make clear the value principle of each parameter in the weighted amplitude wave superposition (WAWS) method based on FFT technique, the particular attention was paid on the time step Δt and its influence on the following dynamic calculation results. Aiming at the SDOF spring oscillator model and the lightning rod high-rise structure of a transformer substation, a variety of parameters were used to simulate the fluctuating wind time history and calculate the time history dynamics. The value principle of parameters of WAWS, including the cut-off frequency fu, period T0, frequency point N, ratio of time point to frequency point M/N and the time step Δt, was given by comparing the results and analyzing the principle of WAWS and combining the characteristics of wind spectrum and modal force spectrum. The research results show that: in random field simulation based on WAWS with single index frequency, if the ratio of time-frequency points is taken as the commonly used value M/N=2, there are only two time points in each period of the harmonic wave corresponding to the maximum frequency fu. So the obtained broken line can't accurately reproduce the simulation target of the original cosine curve, moreover, the corresponding Δt may not be able to accurately account for the resonance effect of the structure in the dynamic time history calculation. In order to accurately account for the resonance effect in the dynamic calculation, fu and M/N can be increased to decrease Δt, and the effect of increasing fu or M/N is the same. The spring oscillator model has the most stringent requirements for Δt, which can be regarded as the upper limit of ordinary structure. And the specific value of Δt of ordinary structure can be determined reasonably through trial calculation under the guidance of the upper limit value.

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Real-Time Detection Method of Compaction Uniformity of Asphalt Bridge Deck

MA Liying, LI Maoqi, CAO Yuanwen, DONG Qinqin

2020, 39(02): 69-74. DOI: 10.3969/j.issn.1674-0696.2020.02.11

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In order to accurately evaluate the compaction uniformity of asphalt pavement and realize the real-time monitoring of compaction uniformity of vibratory roller based on cloud computing, the effective value of acceleration was analyzed as the evaluation index of compaction uniformity through laboratory test firstly. Based on the Yunnan Provincial Transportation Technology Fund Project, the acceleration signals of the test sections were collected by using the DH5902 dynamic data acquisition analyzer. The longitudinal compaction uniformity of different rolling passes was calculated and compared. The experimental results show that Sr, SR, k, h are statistical indicators, which can well reflect the compactness of asphalt pavement. With a certain number of rolling passes, the compaction uniformity is positively correlated with the number of rolling passes. When the number of rolling passes is fourth and seventh, the values of k and h are all within the critical value and the compaction uniformity reaches the best. The proposed detection method provides a basis for a new real-time monitoring system for compaction uniformity of asphalt bridge deck.

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Grey Correlation Analysis on Low Temperature Performance and Evaluation Indexes of Calcium Sulfate Whisker Modified Asphalt

FAN Taotao1, WANG Xiushan2

2020, 39(02): 75-80. DOI: 10.3969/j.issn.1674-0696.2020.02.12

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To optimize the low temperature performance evaluation indexes of calcium sulfate whisker (CSW) modified asphalt, the correlation of 10 ℃ ductility, equivalent brittle point T1.2, 15 ℃ cone penetration and cone penetration index (CI) of CSW modified asphalt with -12 ℃bending creep stiffness test index (S) and stress relaxation rate (m) were analyzed by using grey correlation theory. The results indicate that it is feasible to use grey correlation theory to optimize the evaluation indexes of the low temperature performance of CSW modified asphalt. Among them, the correlation between the equivalent brittle point T1.2 and the stiffness modulus and m-value is the largest, followed by 10℃ ductility and cone penetration index (CI). The research results of influencing factors on the low temperature performance of CSW modified asphalt show that the low temperature performance of asphalt is reduced to some extent after the incorporation of CSW, and CSW types have significantly larger influence on the low temperature performance of asphalt than CSW contents do.

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Anti-Skidding Performance of Rubber Modified Asphalt Pavement Based on Viscoelasticity

WU Guoxiong1,2, YE Xinyu1, YU Miao1, YANG Dantong3

2020, 39(02): 81-86. DOI: 10.3969/j.issn.1674-0696.2020.02.13

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In order to study the effect of crumb rubber on the anti-skidding performance of asphalt pavement, based on SMA-13 asphalt mixture, the mixture ratio design of rubber modified asphalt mixture was carried out by using the internal mixing method to replace the corresponding aggregate with equal amount of rubber particles. The content of crumb rubber added were 0%, 1%, 3% and 5% respectively, and four groups of asphalt mixtures were prepared, including SMA-13A, SMA-13B, SMA-13C and SMA-13D. Rotary compacted specimen and rutting specimen were prepared respectively and the temperature of the specimen was maintained at 10℃, 20℃, 30℃, 40℃ and 50℃. The AMPT test was carried out by using uniaxial compression test method and the dynamic modulus E and the phase angle φ were obtained. Meanwhile, the anti-skidding performance test was carried out by using the self-developed tire-road dynamic friction coefficient test system, and the dynamic friction coefficient f was obtained. The results show that the order of the viscoelasticity of asphalt mixtures is SMA-13D＞SMA-13C＞SMA-13B＞SMA-13A, which indicates that the viscoelasticity of asphalt mixtures is improved after adding crumb rubber, and the greater the content, the better the viscoelasticity. When the specimen temperature is at 10℃, 20℃, 30℃, 40℃ and 50℃, the correlation between the dynamic friction coefficient f and the dynamic modulus E of asphalt mixtures is basically the same, indicating that the temperature of the asphalt mixture specimen has little influence on the correlation between f and E. Under the dynamic load of the vehicle, with the increase of crumb rubber content R, the dynamic modulus E of the asphalt mixtures decreases, the dynamic friction coefficient f increases but the phase angle φ decreases, indicating that the crumb rubber particles can improve the viscoelasticity of asphalt pavement, and thus improve the anti-skidding performance of asphalt pavement.

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Influence of Regional Climate Change on Summer Temperature Effect of Asphalt Pavement

FU Jun1,3, LIU Zhihong1,2, ZUO Xuena3, LAI Zehan1, WANG Xuezhi1, DING Qingjun4

2020, 39(02): 87-94. DOI: 10.3969/j.issn.1674-0696.2020.02.14

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Based on the regional climate change in central China (Wuhan), a three-dimensional temperature analysis finite element model of asphalt pavement was established, and the summer temperature effect of asphalt pavement was studied, and the representative daily cycle temperature field variation curve of asphalt pavement in summer was obtained. Combined with laboratory tests and references, the effect of temperature on the elastic modulus and Poissons ratio of asphalt mixture was analyzed, and the influence of regional climate change on the permanent deformation of asphalt pavement was calculated. The results show that there is a negative correlation between the temperature change rate of asphalt pavement and the depth of pavement structure. The regional climate change mainly affects the asphalt surface area, and will significantly reduce the elastic modulus of asphalt pavement material (about 30%) in summer, has little impact on Poisson's ratio. Regional climate change will increase the permanent deformation of asphalt pavement by more than 30% in future, which will aggravate the damage of asphalt pavement. The study can provide some reference for the influence of global climate change on asphalt pavement design and service performance evolution.

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Deformation Analysis on the Construction of Foundation Pit of Subway Station Adjacent to Railway Line

LI Xiaohui

2020, 39(02): 95-102. DOI: 10.3969/j.issn.1674-0696.2020.02.15

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When subway open-cut station is constructed near railway tracks, the two often have a negative impact on each other, which has an impact on the safety of construction and the normal operation of the railway. Based on the construction of the foundation pit of the Shangshagou Station of line 3 of Nanchang Subway, the influence of foundation pit excavation on adjacent railway lines was analyzed. Through the finite element modeling, the 3-D FEA model of the relationship between foundation pit excavation and railway subgrade in subway station was established, and the variation laws of ground settlement, internal force of support system and railway track settlement under the interaction between railway operation and foundation pit construction during construction were analyzed. Finally, the reliability and accuracy of the finite element numerical model were verified by comparing the actual construction monitoring data. The research results can be used as reference for the deformation prediction and interaction analysis of similar projects in the future.

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RFPA Numerical Simulation of Compression Failure of Variable Cracked Rock Mass

TANG Hongmei, WANG Ping, WANG Linfeng

2020, 39(02): 103-110. DOI: 10.3969/j.issn.1674-0696.2020.02.16

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The structural plane characteristics of rock mass have important influence on the deformation and failure of rock mass. It is of great significance to study the characteristics of crack expansion, strength and energy during the failure of cracked rock mass. Selecting the physical and mechanical parameters of limestone and adopting the state of one-way compression stress, the influence of different horizontal position, dip angle and length of the initial fracture on the cracked rock mass was analyzed by numerical simulation software RFPA in 14 working conditions. The simulation results show that the horizontal position of the crack has little effect on the upper and lower propagation angles of the crack; with the increase of crack horizontal position a, the time of upper crack growth line appears earlier and earlier, and the influence of crack horizontal position on its peak strength is less; with the increase of crack dip angle, the upper and lower propagation angles decrease rapidly, and the peak strength of specimen increases; with the increase of crack fracture length, the upper and lower propagation angles increase rapidly, and the peak strength tends to decrease. The above three factors have little influence on the residual strength of cracked rock mass. Through the energy and acoustic emission activities of 14 working conditions, it is found that: when the prefabricated fracture is far away from the axis, it is of “double-peak” type; when the fracture is steep, it is of “thin-high” type; when the fracture is gentle to medium dip, it is of “short-fat” type. The research results are of great significance to the prevention and control of dangerous rock in limestone area.

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Cyclic Liquefaction Characteristics for Saturated Sand Based on Thermodynamic Dissipation

ZHOU Enquan, YI Sihang, XU Xiang, LU Jianfei

2020, 39(02): 111-117. DOI: 10.3969/j.issn.1674-0696.2020.02.17

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In order to study the dynamic characteristics of saturated sand under cyclic loading, the calculation method of cumulative dissipated energy () of saturated sand under cyclic loading was established by taking the straight line as the migration curve, based on thermodynamic equilibrium conditions and particle entropy theory. A series of cyclic triaxial tests of saturated Nanjing fine sand were carried out, and the influence of factors such as initial cyclic stress ratio (CSR) and effective confining pressure (σ′c) on the liquefaction characteristics of Nanjing fine sand was investigated. The test results show that the cumulative dissipation energy is found to be consistent with a three-stage development law: slow growth stage, transition stage and rapid growth stage. The pore pressure ratio (ru) corresponding to the transition stage is about 0.6 to 0.7. The required cumulative dissipation energy to liquefy Najing fine sand is independent of CSR, but positively related to the effective confining pressure. The pore pressure ratio increases with the increase of cumulative dissipation energy. The function relationship between the cumulative dissipation energy and the effective confining pressure in the initial liquefaction is established, and the energy model of the development of pore pressure ratio is established based on the cumulative energy consumption ratio R.

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Multi-scenario Simulation of Rainfall Runoff in Wushan County Based on SCS Model

MU Fengyun1, LONG Qiuyue1, YU Qing2, YANG Meng1, HE Yong1

2020, 39(02): 118-125. DOI: 10.3969/j.issn.1674-0696.2020.02.18

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The spatial distribution characteristics of runoff in Wushan County under different rainfall scenarios were simulated based on GIS, which provided a basis for disaster prevention, mitigation and emergency management of runoff flood in mountain area. Taking Wushan County of Chongqing as the research area, based on the SCS model, coupled with the data of land use and soil type, the rainfall runoff simulation was carried out and was divided into 5 grades, according to 8 scenarios of 24-hour rainfall, including 50, 75, 100, 125, 150, 175, 200 and 250 mm, which was started from the three scales such as the whole, township and highway. The results show that: (1) With the increase of rainfall intensity, the runoff gradually changes from grade I to grade II~V. The high-level runoff zones mainly distribute in zonal distribution in the middle and south of the study area, and distribute in cluster in the northwest of the study area. The total runoff has increased by 26.35 times, and the overall growth rate continues to decrease. (2) The average runoff of Guandu Town, Dachang Town and Wuxia Town in the study area is more than 100 million m3, which is vulnerable to floods, mudslides, landslides and other disasters. Therefore, key prevention and control should be carried out in flood season. (3) The total amount of road runoff in the study area has increased by 17.91 times, and the runoff of western roads and a few roads in the east is large, which is easy to cause road interruption due to flood disaster. (4) When there is a heavy rainstorm, the highway runoff of Dachang Town, Guandu town, Wuxia town and other towns in the study area is V-grade, which is the section with high rainfall runoff and flood disaster. The multi-scenario simulation of rainfall runoff based on SCS model can better represent the spatial distribution of rainfall runoff, and the calculation results can be used for disaster prevention, mitigation and emergency management.

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Influence of Heat Convection on the Energy Distribution Characteristic of the Gasoline Engine Based on Atkinson Cycle

HE Yituan, HAN Cuijie, LIU Yang, YUAN Chenheng, SHAO Yiming

2020, 39(02): 126-131. DOI: 10.3969/j.issn.1674-0696.2020.02.19

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A gasoline engine simulation model was established based on GT-Power software and validated by experiment. The original Otto cycle model was modified to an Atkinson cycle model with a higher geometric compression ratio by designing a new valve lift curve. The heat convection factor of the heat transfer model was changed to calculate and analyze the effect of heat convection on the energy distribution characteristics of the Atkinson cycle under the condition of 2000 r/min, 50% load, and theoretical air fuel ratio. The results show that compared with the Otto cycle, the heat loss of the Atkinson cycle is increased by 3.5% under the normal heat rejection conditions, but the energy taken off by the exhaust gas is greatly reduced owing to the longer expansion stroke of the Atkinson cycle, so the indicated thermal efficiency of the Atkinson cycle is still increased by 2.9%. The weaker heat convection intensity leads to the lower heat transfer rate in the cylinder and the higher level of isochoric heat release, which resulting in the less heat loss and the higher indicated thermal efficiency. The energy saved after reducing heat dissipation is converted into the indicated work or taken off by exhaust, and under different convective heat transfer intensities, Atkinson cycle is more efficient in converting the saved energy into the indicated work, which is more than 6% higher than that of Otto cycle. It is beneficial to optimize the energy distribution characteristics of the Atkinson cycle, further exert the energy saving advantages of Atkinson cycle and improve the power performance by reducing the heat convection intensity. However, the heat load in the cylinder is increased.

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Simulation and Research of IGBT Radiator under Multiple Gaps Based on Icepak

YING Baosheng1, LIU Dongdong2, WU Huawei3, SU Yedong4

2020, 39(02): 132-137. DOI: 10.3969/j.issn.1674-0696.2020.02.20

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In view of the limitation of the heat dissipation of the water-cooled radiator with fork row needle column, a kind of fork row needle column water-cooled radiator with various clearances arrangement was proposed, which improved the heat dissipation performance of the radiator by increasing the turbulence of the cooling water in the water channel. Based on ANSYS Icepak simulation software, the thermal simulation of two kinds of radiators was carried out, and the distribution of temperature field and flow field was obtained. The results show that at the same flow rate, the heat dissipation performance of the fork row needle column water-cooled radiator with different clearance arrangement is better. The thermistor is used to verify its three points, the deviation between the experimental data and the simulation data of the proposed radiator is less than 5.5%, which has a high consistency. It is further verified that the radiator has a good heat dissipation performance.

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Numerical Simulation Study on Air Filter Forward Intake System for Heavy Truck

WANG Renren1, SHI Pidong2, CAO Fang2, LIU Zhihao2

2020, 39(02): 138-144. DOI: 10.3969/j.issn.1674-0696.2020.02.21

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The internal 3D fluid model of the forward intake system of the heavy truck air filter was built. By using the two-phase coupling method of computational fluid dynamics, the effects of different structures, single blade channel and blade axle on the flow field characteristics and filtration efficiency of the forward intake system were studied, and the parameters of the forward intake system were optimized. The research shows that: with the increase of the geometric diameter parameters of the blade axle, the overall average pressure drop trends to increase slowly first and then rise suddenly; the filtration efficiency shows a trend of high and low bimodal changes. Finally, when the geometric diameter parameter of the blade axle is 57.78mm, the particle efficiency is significantly improved and the filtration efficiency is increased by 10.07%, compared with the original structure.

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