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Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle

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Journal of Environmental Sciences 2024年第2期136卷 35-44页

作者： Yunhua Zhang Diming Lou Piqiang Tan Zhiyuan Hu Liang Fang School of Automotive Studies Tongji UniversityShanghai 201804China

In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis dynamometer.Results showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst loading.After using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading.Notably,the CDPF increased the accumulation mode particles proportion,producing a larger GMD.For the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation mode.The PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was removed.The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was weakened.The used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.

关键词： Catalyzed diesel particulate filter (CDPF) Catalyst loading Aging Particle Particle size distribution Geometric mean diameter

Effect of catalyzed diesel particulate filter and its catalyst loading on emission characteristics of a non-road diesel engine

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Journal of Environmental Sciences 2023年第4期126卷 794-805页

作者： Yunhua Zhang Diming Lou Piqiang Tan Zhiyuan Hu Liang Fang School of Automotive Studies Tongji UniversityShanghai 201804China

In this study, the effects of a diesel oxidation catalyst(DOC) coupled with a catalyzed diesel particulate filter(CDPF) with different catalyst loadings on the power, fuel consumption,gaseous and particulate emissions from a non-road diesel engine were investigated. Results showed that the after-treatment had a negligible effect on the power and fuel consumption.The reduction effect of the DOC on the CO and hydrocarbon(HC) increased with the engine load. Further reductions occurred coupling with the CDPF. Increasing the catalyst loading resulted in a more significant reduction in the HC emissions than CO emissions. The DOC could increase the NO_(2)proportion to 37.9%, and more NO_(2)was produced when coupled with the CDPF below 250℃;above 250℃, more NO_(2)was consumed. The after-treatment could reduce more than 99% of the particle number(PN) and 98% of the particle mass(PM).Further reductions in the PN and PM occurred with a higher CDPF catalyst loading. The DOC had a better reduction effect on the nucleation particles than the accumulation ones, but the trend reversed with the CDPF. The DOC shifted the particle size distribution(PSD) to larger particles with an accumulation particle proportion increasing from 13% to 20%, and the geometric mean diameter(GMD) increased from 18.2 to 26.0 nm. The trend reversed with the CDPF and the accumulation particle proportion declined to less than 10%. A lower catalyst loading on the CDPF led to a higher proportion of nucleation particles and a smaller GMD.

关键词： Catalyzed diesel particulate filter Catalyst loading Emissions Particle size distribution Geometric mean diameter

Fault Diagnosis of Proton Exchange Membrane Fuel Cell Based on Nonlinear Impedance Spectrum

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automotive Innovation 2023年第4期6卷 597-610页

作者： Hao Yuan Shaozhe Zhang Xuezhe Wei Haifeng Dai School of Automotive Studies Tongji UniversityShanghaiChina

Electrochemical impedance spectroscopy(EIS)contributes to developing the fault diagnosis tools for fuel cells,which is of great significance in improving service life.The conventional impedance measurement techniques are limited to linear responses,failing to capture high-order harmonic responses.However,nonlinear electrochemical impedance analysis incorporates additional nonlinear information,enabling the resolution of such responses.This study proposes a novel multi-stage fault diagnosis method based on the nonlinear electrochemical impedance spectrum(NEIS).First,the impact of alternating current excitation amplitude on NEIS is analyzed.Then,a series of experiments are conducted to obtain NEIS data under various fault conditions,encompassing recoverable faults like flooding,drying,starvation,and their mixed faults,spanning different degrees of fault severity.Based on these experiments,both EIS and NEIS datasets are established,and principal component analysis is utilized to extract the main features,thereby reducing the dimensionality of the original data.Finally,a fault diagnosis model is constructed with the support vector machine(SVM)and random forest algorithms,with model hyperparameters optimized by a hybrid genetic particle swarm optimization(HGAPSO)algorithm.The results show that the diagnostic accuracy of NEIS is higher than that of traditional EIS,with the HGAPSO-SVM model achieving a 100%accurate diagnosis under the NEIS dateset and self-defined fault labels.

关键词： Fuel cell Nonlinear electrochemical impedance spectrum Fault diagnosis

Evaluation of Automatic Lane-Change Model Based on Vehicle Cluster Generalized Dynamic System

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automotive Innovation 2022年第1期5卷 91-104页

作者： Yangyang Wang Xiaolang Cao Xinyuan Ma School of Automotive Studies Tongji UniversityShanghaiChina

The lane-change transportation research usually focuses on the efficiency and stability of the macro traffic flow while ignoring the driving comfort of individual vehicles.And many studies of lane-change models are often limited to the performance of a single vehicle,which leads to a lack of macroscopic evaluation.To solve the above limitations,an automatic lane-change generalized dynamic model is adopted.In this model,the lane-change behavior of an individual vehicle is considered as the generalized excitation and the restraining force between vehicles is described with the car-following model.Macro and micro evaluation indexes are also adopted to evaluate the automatic lane-change behavior in traffic flow.Furthermore,this paper proposes a modified intelligent driver model(IDM)to describe the state change process during lane change.The hyperbolic tangent transition function is used to eliminate the vehicle state mutation.The simulation results show that the proposed automatic lane-change generalized dynamic model can reflect the macro and micro parameters of the traffic flow.And compared with the traditional IDM model,the proposed HC-IDM model achieves higher comfort performance and lower fluctuation of traffic flow.

关键词： Lane change model Generalized dynamic system IDM car-following model

A Trajectory Planning Method of Automatic Lane Change Based on Dynamic Safety Domain

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automotive Innovation 2023年第3期6卷 466-480页

作者： Yangyang Wang Xiaolang Cao Yulun Hu School of Automotive Studies Tongji UniversityShanghai 200092China

Traditional research on automatic lane change has primarily focused on high-speed scenarios and has not considered the dynamic state changes of surrounding vehicles.This paper addresses this problem by proposing a trajectory planning method to enable automatic lane change at medium and low speeds.The method is based on a dynamic safety domain model,which takes into account the actual state change of surrounding vehicles,as well as the upper boundary of the safety domain for collision avoidance and the lower boundary of comfort for vehicle stability.The proposed method involves the quantification of the safety and comfort boundaries through parametric modeling of the vehicle.A quintic polynomial trajectory planning method is proposed and evaluated through simulation and testing,resulting in improved safety and comfort for automatic lane change.

关键词： Automatic lane change Dynamic safety domain Trajectory planning Autonomous driving

An Innovative Argon/Miller Power Cycle for Internal Combustion Engine: Thermodynamic Analysis of its Efficiency and Power Density

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automotive Innovation 2023年第1期6卷 76-88页

作者： Chenxu Wang Shaoye Jin Jun Deng Liguang Li School of Automotive Studies Tongji UniversityShanghai 200092China

Increasing efficiency and reducing emissions are fundamental approaches to achieving peak carbon emissions and carbon neutrality for the transportation and power industries.The Argon power cycle(APC)is a novel concept for high efficiency and zero emissions.However,APC faces the challenges of severe knock and low power density at high efficiency.To elevate efficiency and power density simultaneously of APC,the Miller cycle is applied and combined with APC.The calculation method is based on a modification of the previous thermodynamic method.The mixture of hydrogen and oxygen is controlled in the stoichiometric ratio.The results indicate that to obtain a thermal conversion efficiency of 70%,in the Otto cycle,the compression ratio and the AR(argon molar ratio in the argon-oxygen mixture)could be 9 and 95%,respectively.In comparison,for the Miller cycle,these two parameters only need to be 7 and 91%.A lower compression ratio can reduce the negative effect of knock,and a reduced AR increases the power density by 66%with the same efficiency.The improvement effect is significant when the expansion-compression ratio is 1.5.Meanwhile,increasing the expansion-compression ratio is more effective in the argon-oxygen mixture than in the nitrogen–oxygen mixture.For the next-generation Argon/Miller power cycle engine,the feasible design to achieve the indicated thermal efficiency of 58.6%should be a compression ratio of 11,an expansion-compression ratio of 1.5,and an AR of 91%.

关键词： Argon power cycle engine Miller cycle Hydrogen Thermal conversion efficiency Power density

Numerical Investigation of the Centrifugal Compressor Stability Improvement by Half Vaned Low Solidity Diffusers

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Journal of Thermal Science 2021年第2期30卷 696-706页

作者： CHEN Siyue ZUO Shuguang WEI Kaijun School of Automotive Studies Tongji UniversityShanghai 201804China

Centrifugal compressors for the fuel cell vehicles often operate near the surge line compared with the turbocharger compressors.Low solidity and half vaned diffusers are recognized as good ways to improve the stability of the centrifugal compressor.The presented work investigated four diffuser configurations (i.e.,the vaneless diffuser (VLD),full-height low solidity vaned diffuser (LSVD),hub-side half vaned diffuser (HVD) and shroud-side half vaned diffuser (SVD)) through steady-state and unsteady numerical simulations.The results show that the best performance is achieved by the LSVD,HVD and SVD at the design,surge and choke conditions.The flow rate at the surge operating point of the HVD has decreased by 15.53% compared with the LSVD,and 9.21% compared with the VLD.At near surge operating point,a longitudinal suction side passage vortex is formed on the hub of the LSVD and rotates as circumferential stall cells.A hairpin vortex is formed along the leading edge and is dragged by the main flow along the suction side as a local vortex shedding.The mechanism of the stability improvement by half vaned diffusers is that the tip leakage vortex migrates from the clearance side to the vane mounting side and replenishes the low-momentum zone on the mounting side.The best position where the half vaned diffuser should be mounted is based on the impeller outlet flow conditions,namely,the location of the wake region,where the meridional velocity and relative stagnation pressure is low.

关键词： centrifugal compressor low solidity diffuser half vaned diffuser flow control numerical simulation

Accelerated Test of Silicone Rubbers Exposing to PEMFC environment

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Progress in Natural Science:Materials International 2020年第6期30卷 882-889页

作者： Daijun Yang Jingwen Ma Qing Zhang Bing Li Pingwen Ming Cunman Zhang Clean Energy automotive Engineering Center Tongji University School of Automotive Studies Tongji University

The durability of sealing material is one of the major challenges to the overall lifetime of proton exchange membrane fuel cell(PEMFC). In order to study the failure mode and aging mechanism of fuel cell seals, this paper focuses on the most widely used commercial silicone rubber, and an ex-situ accelerated aging method was employed by simulating the circumstance of PEMFC, including higher temperature and clamping force, lower p H value and F-with higher concentration. The main factors that affect the performance of the seal were obtained through the test of their morphologies and mechanical properties. The failure mode of the aging mechanism of the rubbers were analyzed through scanning electron microscopy(SEM), energy dispersive spectrometer(EDS),attenuated-total-reflection infrared spectroscopy(ATR-IR), mass loss, compression set(CS), etc. It was found that temperature played an important role in the deterioration of seal performance, and the change of the parameters of the compression set with time conformed the dynamic empirical formula, which provides the experimental basis for the lifetime prediction of the seals.

关键词： PEMFC Sealing material Simulating experiment Durability Lifetime prediction

Stress Relaxation and Sensitivity Weight for Bi-Directional Evolutionary Structural Optimization to Improve the Computational Efficiency and Stabilization on Stress-Based Topology Optimization

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Computer Modeling in Engineering & Sciences 2021年第2期126卷 715-738页

作者： Chao Ma Yunkai Gao Yuexing Duan Zhe Liu School of Automotive Studies Tongji UniversityShanghai201804China

Stress-based topology optimization is one of the most concerns of structural optimization and receives much attention in a wide range of engineering designs.To solve the inherent issues of stress-based topology optimization,many schemes are added to the conventional bi-directional evolutionary structural optimization(BESO)method in the previous studies.However,these schemes degrade the generality of BESO and increase the computational cost.This study proposes an improved topology optimization method for the continuum structures considering stress minimization in the framework of the conventional BESO method.A global stress measure constructed by p-norm function is treated as the objective function.To stabilize the optimization process,both qp-relaxation and sensitivity weight scheme are introduced.Design variables are updated by the conventional BESO method.Several 2D and 3D examples are used to demonstrate the validity of the proposed method.The results show that the optimization process can be stabilized by qp-relaxation.The value of q and p are crucial to reasonable solutions.The proposed sensitivity weight scheme further stabilizes the optimization process and evenly distributes the stress field.The computational efficiency of the proposed method is higher than the previous methods because it keeps the generality of BESO and does not need additional schemes.

关键词： Stress-based topology optimization aggregation function stress relaxation sensitivity weight bi-directional evolutionary structural optimization