Volume 47,Issue 1,2024 Table of Contents

1 Simulation study on HCCI combustion of DME/methanol fueled engine

WANG Xin , TAN Ling , CHEN Zhaoyang

2024, 47(1):1-8. DOI: 10.11835/j.issn.1000-582X.2022.004

[Abstract](903) [HTML](57) [PDF 2.11 M](564)

Abstract:
To determine the effects of mixture concentration and fuel blending on the combustion performance of a dimethyl ether/methanol fueled HCCI engine, the combustion process under different excess air coefficients and dimethyl ether addition ratios was simulated. Parameters such as temperature, pressure, pressure rise rate and the heat release rate were examined, as well as the fuel consumption path. The results show that the peak values of the pressure, temperature, heat release rate and pressure rise rate decrease with the increase of the excess air coefficient, while the phases are delayed. Excessive excess air coefficient hinders the further oxidation reaction of CO, resulting in high CO residue. On the other hand, increasing the dimethyl ether (DME) addition ratio leads to higher peak values of pressure and temperature in the cylinder, advancing their phases, while the peak values of pressure rise rate and heat release rate decrease. The combustion heat release rate curve of dimethyl ether homogeneous charge compression ignition (HCCI) combustion exhibits three peaks. The first peak, occurring at a crane angle of 30° before topdead center (BTDC) with a temperature of 804 K, corresponds to the low-temperature-oxidation heat release of dimethyl ether. The second peak, appearing at a crane angle of 15° BTDC with a temperature of 1 193 K, corresponds to the heat release from reactions forming CO through formaldehyde and other intermediates. The third peak represents the heat release from CO oxidation when CO₂ is generated. The second and third exothermic rate peaks indicate the high-temperature oxidation exothermic stage of dimethyl ether. Additionally, when mixed with methanol, the low-temperature oxidation reaction of dimethyl ether promotes the combustion of the mixture.

2 Application of LOLIMOT to CNG engine NO_x emission prediction test

LIU Jiaqi , LU Chihua , LIU Zhien

2024, 47(1):9-20. DOI: 10.11835/j.issn.1000-582X.2022.112

[Abstract](846) [HTML](65) [PDF 4.78 M](429)

Abstract:
To solve the problem of insufficient prediction accuracy of the local linear model tree (LOLIMOT) emission model in the development of the selective catalytic reduction technology (SCR) control strategy, a method of optimizing the space boundary is proposed. This method aims to constrain the super-rectangular input space of the original model within the scope of physical definitions in the modified LOLIMOT model. Through the identification test of a compressed natural gas (CNG) engine, the effects of this method on prediction results are analyzed considering distribution characteristics and calculation principles. The results show that compared with the original algorithm, the linear correlation R² of the improved algorithm is increased by 1.9%, verifying the effectiveness of the proposed strategy. The modified LOLIMOT algorithm demonstrates higher convergence speed and stability, offering valuable application advantages in the field of emission models.

3 Effect of exhaust gas incident pipe parameters on EGR stratification in cylinder

YANG Chuan , LIAO Yong , DU Yongbo , LI Yuandong , ZHANG Li

2024, 47(1):21-30. DOI: 10.11835/j.issn.1000-582X.2022.008

[Abstract](831) [HTML](64) [PDF 3.47 M](442)

Abstract:
To realize exhaust gas recirculation (EGR) stratification in the cylinder of a motorcycle gasoline engine, so as to reduce pump air loss and NO_x emission, the intake bypass system in the original engine was transformed into an EGR system. The boundary conditions and initial conditions of the exhaust incident pipe, inlet and exhaust ducts under 3 000 r/min and 60 mg intake air were solved by using the GT-POWER model. These conditions were imported into the CONVERGE model of the engine for calculation, and the exhaust gas incident pipe parameters were determined by comparing the flow characteristics, velocity field and exhaust gas mass fraction in the cylinder under different exhaust gas incident pipe diameters, installation angles and installation distances. The results show that under the condition of 3 000 r/min and 60 mg intake air, EGR stratification can be realized in the cylinder when the exhaust gas incident pipe diameter is 5 mm, the incident pipe inclination angle is 17.5° and the installation distance is 22 mm.

4 Effect of route topography on real driving emissions based on neural network models

CHANG Hong , WU Dongmei , ZHANG Li , GONG Xiangkun , XU Hualong , FU Mingming

2024, 47(1):31-40. DOI: 10.11835/j.issn.1000-582X.2022.130

[Abstract](783) [HTML](53) [PDF 2.73 M](421)

Abstract:
It is difficult to separate the effect of route topography from that of other test boundaries in real driving emission (RDE) tests. We proposed an artificial neural network (ANN) weight method to quantitatively evaluate the impact of route topography on RDE tests. Based on 37 256 data window samples of RDE tests in Chongqing, a factor analysis method was used to reduce data and eliminate information overlap between test boundaries. Additionally, a neural network model was also established to predict pollutant emissions and calculate the relative importance of input variables. The results show that route topography significantly affects CO₂ emissions, with its relative importance far exceeding that of other test boundaries. Moreover, the influence of the route topography cannot be ignored for CO, PN (particle number), and NO_x emissions, having an impact on vehicle driving emissions comparable to that of trip dynamics, especially under high-speed driving conditions. However, the existing regulatory emission standards seriously underestimate the impact of the route topography on vehicle driving emissions.

5 Deep reinforcement learning hierarchical energy management strategy for hybrid electric vehicles

DAI Kefeng , HU Minghui

2024, 47(1):41-51. DOI: 10.11835/j.issn.1000-582X.2022.012

[Abstract](1014) [HTML](57) [PDF 3.88 M](853)

Abstract:
To improve the fuel economy and control strategy stability of hybrid electric vehicles (HEVs), with taking the third-generation Prius hybrid electric vehicle as the research object, a hierarchical energy management strategy is created by combining an equivalent fuel consumption minimization strategy (ECMS) with a deep reinforcement learning (DRL) method. The simulation results show that the hierarchical control strategy not only enables the agent in reinforcement learning to achieve adaptive energy-saving control without a model, but also ensures that the state of charge (SOC) of the hybrid vehicle meets the constraints under all operating conditions. Compared with the rule-based energy management strategy, this layered control strategy improves the fuel economy by 20.83% to 32.66%. Additionally, increasing the prediction information of the vehicle speed by the agent further reduces the fuel consumption by about 5.12%. Compared with the deep reinforcement learning strategy alone, this combined strategy improves fuel economy by about 8.04%. Furthermore, compared with the A-ECMS strategy that uses SOC offset penalty, the fuel economy is improved by 5.81% to 16.18% under this proposed strategy.

6 Hybrid power pack configuration and energy management strategy for rail transit equipment

LEI Yanlei , KONG Linghao , HU Minghui , CHEN Shuang , MENG Fanjie

2024, 47(1):52-68. DOI: 10.11835/j.issn.1000-582X.2023.211

[Abstract](771) [HTML](55) [PDF 5.27 M](560)

Abstract:
The main type of rail transit equipment used in non-electrified railways is diesel multiple units (DMUs) powered by traditional fossil fuels, which suffers from low efficiency and high fuel consumption. To address this issue, a configuration scheme for a hybrid power pack for railway equipment was designed, and a mathematical model for the hybrid locomotive was established. The operational status of this configuration scheme under different modes was investigated, and an energy management strategy based on dynamic programming algorithm was proposed, with considering the operating conditions. Simulation results demonstrate that with this energy management strategy, the fuel economy of the hybrid powertrain locomotive is improved by over 32.11% compared to that of the pure fossil fuel locomotive.

7 Vertical dynamic characteristics of electromechanical coupling of in-wheel motor drive system for electric vehicle

LI Tiancheng , DENG Zhaoxiang , ZHANG Heshan , LU Panping , ZENG Pengfei

2024, 47(1):69-83. DOI: 10.11835/j.issn.1000-582X.2022.102

[Abstract](685) [HTML](56) [PDF 4.45 M](790)

Abstract:
Due to the double action of road excitation and vehicle weight, the stator and rotor of the in-wheel motor (IWM) for electric vehicles (EVs) are relatively eccentric, thus generating an unbalanced magnetic force (UMF). When the vertical component of UMF is coupled with the vertical vibration of the suspension system of the vehicle, the ride comfort and other properties of EV are affected. To study this electromechanical coupling problem, by taking a permanent magnet IWM as the research object, the vertical dynamic characteristics of electromechanical coupling of an IWM drive system for electric vehicle were investigated. Firstly, the air gap flux density distribution of IWM under load was obtained by superposition method of magnetic field. By introducing complex relative permeance and correction coefficient of permeance when the motor was eccentric, analytical models of the eccentric magnetic fields of IWM and UMF were obtained with the stator slotting effect taken into account, and the validity of the analytical models was verified by finite element simulation and prototype test. Then, according to the real-time coupling relationship between the vertical vibration of the suspension system and the eccentric UMF of IWM, the dynamic equation of the vehicle was solved by using the Lagrangian method, and the vertical coupling vibration model of a quarter car body was established. Finally, taking the vertical vibration acceleration of the stator of IWM, the vertical vibration acceleration of the car body, the dynamic deflection of the suspension and the dynamic load of the tire as the main indexes, the effect of electromechanical coupling on the vertical dynamic characteristics of EV was studied, and the mechanism of electromechanical coupling between the output characteristics of UMF and dynamic response of EV was revealed. The results show that the electromechanical coupling effect impairs the ride stability, operation stability and safety of EV.

8 Inference method of proton exchange membrane fuel cell gas diffusion layer composition based on pyramid scene parsing network

WANG Hu , YIN Zequan , WANG Wenjie , HUANG Lizhou , FANG Ningning , SUI Junyou , ZHANG Jiale , ZHANG Ruiming , SUI PangChieh

2024, 47(1):84-92. DOI: 10.11835/j.issn.1000-582X.2022.119

[Abstract](848) [HTML](73) [PDF 2.57 M](484)

Abstract:
To rapidly determine the morphology of the gas diffusion layer for proton exchange membrane fuel cell (PEMFC) and improve its fabrication process, a method of gas diffusion layer (GDL) component identification and proportional reasoning based on a combination of pyramid scene parsing network (PSPNet) and multilayer perceptron (MLP) is proposed. First, labeled GDL scanning electron microscope （SEM) images are input into the neural network to obtain a feature extraction map. This map is used in the pyramid pooling module to extract both deep and shallow features of the SEM images. Subsequently, these feature layers are input into the fully convolutional network (FCN) module to produce a predicted image of the same size. Finally, the proportion of pixels for each component is calculated, and the inference of component proportion is achieved by using the MLP. The accuracy of the proposed method is 81.24%, with an accuracy of proportional reasoning reaching 88.89% within a 5% deviation range. The proposed method can be effectively used for gas diffusion layer quality detection, numerical reconstruction, and process improvement.

9 Temperature field and its influencing factors of friction pair of wet clutch of hybrid electric vehicle

CAI Yang , WANG Zhengwu , WANG Huan , HU Minghui

2024, 47(1):93-103. DOI: 10.11835/j.issn.1000-582X.2022.129

[Abstract](820) [HTML](53) [PDF 3.39 M](589)

Abstract:
The sliding process in the friction pair involves highly nonlinear behavior, and the temperature field of the friction pair is affected by numerous parameters. To gain a comprehensive understanding of the temperature field distribution in the friction pair of a hybrid electric vehicle clutch, a thermal structure coupling analysis model of the hybrid electric vehicle clutch was constructed to simulate the sliding process. Building upon this model, an in-depth study was conducted to analyze the impact of various parameters, such as initial speed, engagement oil pressure, dual steel plate thickness, and friction lining material, on the temperature field of friction pair.

10 Adaptive fuzzy control of torsional vibration of hybrid electric vehicle engine under start-stop condition

CHEN Long , TAO lei

2024, 47(1):104-114. DOI: 10.11835/j.issn.1000-582X.2023.103

[Abstract](855) [HTML](48) [PDF 2.58 M](563)

Abstract:
The starting and stopping process of a hybrid electric vehicle engine often results in torque ripple, leading to torsional vibrations in the vehicle’s powertrain system and causing irregular vehicle power delivery. To solve these problems, an active control method for torsional vibrations based on active control of electromagnetic damping torque of the motor is proposed. Firstly, a dynamic simulation model and engine start-stop control logic under engine start-stop condition is established. Additionally, an adaptive fuzzy control strategy for engine start-stop torsional vibration is proposed. Finally, the simulation model is used to simulate the engine starting and stopping conditions under two driving conditions of the vehicle. The torsional vibration response curves of the driveline under the proposed control method and without any control are compared and analyzed. The results show that the average torsional vibration attenuation rates achieved by the proposed method are 23.8% and 30.1%, respectively, during stationary stop engine conditions, compared to the uncontrolled state. Moreover, the average attenuation rate of torsional vibration under the starting-stopping conditions during vehicle travel is 12.1% and 23.6%, respectively. This proposed method effectively attenuates the torsional vibrations of the driveline during engine starting and stopping conditions, thereby improving the NVH (noise, vibration, and harshness) performance of the hybrid electric vehicle during these operational states.

11 Reliability evaluation of distribution network with distributed generation and electric vehicle

WANG Hui , LI Xuyang , WANG Baoquan , WANG Yifan , FANG Hang , JIN Zirong

2024, 47(1):115-126. DOI: 10.11835/j.issn.1000-582X.2022.211

[Abstract](855) [HTML](75) [PDF 2.37 M](613)

Abstract:
The integration of large-scale distributed generation and electric vehicles into the distribution network can have an impact on its reliability. To address this issue, a reliability evaluation method for a new distribution network containing distributed generation and electric vehicles was proposed. Firstly, with considering the uncertainty and correlation of wind and power output, the best fitting Frank-Copula function was selected and a joint probability model of wind and solar power was established. Secondly, the behavior characteristics of electric vehicle users were analyzed, and an orderly charge and discharge control strategy of electric vehicle was proposed based on dynamic time-of-use pricing. Finally, using the main feeder F4 of the improved IEEE-RBTS Bus6 test system, the reliability index of the system was calculated and analyzed. The results show that the proposed wind solar joint output model and orderly charge-discharge control strategy can effectively reduce the impact on the reliability of the distribution network.

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