Modeling and Experimental Study of PEM Fuel Cell Transient Response for Automotive Applications

This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane （PEM） fuel cell stack to step changes in load, which are charactedstic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and expedment are based on a low pressure 5 kW proton exchange membrane fuel cell （PEMFC） stack, which is similar to those used in several of Tsinghua＇s fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008.

Development and application of magnesium alloy parts for automotive OEMs:A review

China is currently vigorously implementing the“energy conservation and emission reduction”and“dual carbon”strategies.As the most resource-advantaged light metal material in China,Magnesium(Mg)alloy is progressively expanding its application in automobile,rail transportation,aerospace,medical,and electronic products.Chongqing University,Shanghai Jiaotong University,and Australian National University have conducted extensive research on the preparation,properties,and processes of Mg alloys.In the past 20 years,the proportion of Mg alloy in the automotive industry has gradually expanded,whereas currently the design and development of Mg alloy parts for automobiles has rarely been reported.Thus,the application models and typical parts cases of Mg alloy are summarized mainly from the four systems of the whole vehicle(body system,chassis system,powertrain system,interior,and exterior system).Subsequently,two actual original equipment manufacturers(OEM)cases are used to introduce the development logic of reliable die-cast Mg alloy,including forward design,formability analysis,process design analysis,structural redesign,manufacturing,and testing,aiming to share the methods,processes,and focus of attention of automotive OEMs for developing Mg alloy parts to enhance the confidence and motivation of applying Mg alloy in automotive field.Eventually,the multiple challenges faced by Mg alloy materials are sorted out and how to face these challenges are discussed.National policies and regulations,environmental protection and energy saving,and consumer demand will continue to promote the application of Mg.

A review of magnesium die-castings for closure applications

Vehicle mass reduction in the automotive industry has become an industry-wide objective.Increasing fuel efficiency and greenhouse gas emission targets for engine-powered vehicles,and ambitions for extended range electric vehicles have motivated these reductions in vehicle mass.Mass reduction opportunities in structural automotive applications are increasingly realized through lightweight alloy castings,such as magnesium,primarily due to the ease of component substitution.The traditional benefits of magnesium die-castings including lightweighting and associated compounded mass savings,excellent strength-to-weight ratio,part consolidation,near net-shape forming,dimensional repeatability,and integration of additional components can be realized in closure applications.One recent example is the application of a magnesium die-casting for the structural inner of the liftgate in the 2017 Chrysler Pacifica,replacing nine parts in the previous generation and resulting in a liftgate assembly weight reduction of nearly 50%.The work presented here reviews past and current developments of magnesium die-castings in closure applications and discusses the benefits and challenges of magnesium alloys for these applications,including casting design,corrosion and fastening strategies,and the manufacturing design and assembly methodologies.

Evaluation of hot pressing parameters on the electrochemical performance of MEAs based on Aquivion^(■) PFSA membranes

The membrane-electrodes assembly(MEA) is the core of the Polymer Electrolyte Fuel Cell(PEFC). It consists of a membrane, catalytic(CL) and gas diffusion layers(GDL). In order to manufacture MEAs with suitable performance, a hot-pressing procedure is generally used. The relevant parameters are the temperature, pressure and time of hot-pressing. Such variables need to be adjusted as a function of the type of ionomer used in the catalytic layer and membrane. In this study, an evaluation of the temperature of hot-pressing was carried out and its influence on MEA electrochemical performance was assessed. In particular, preparation trials of MEAs were carried out with reinforced experimental membranes based on Aquivion^■ short-side-chain PFSA(by Solvay Specialty Polymers). The membranes were coupled to gas diffusion electrodes, and MEAs were manufactured using different temperatures for the hot-pressing procedure in order to evaluate their influence on the electrochemical performance of PEFCs, in the temperature range of 80–95 °C, with low relative humidity of the reactant gases. The electrochemical performance of the prepared MEAs was tested in a H2/Air 25 cm^2 single cell in terms of polarization curves and accelerated stress test(AST).

Feasibility of 0.02% Nb-Based Microalloyed Steel for the Application of One-Step Quenching and Partitioning Heat Treatment

To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.

Development of 600MPa Cold Rolled Dual Phase Steel for Automotive Application in BX Steel

BX STEEL has developed 600MPa cold rolled dual phase in order to adapt to the market demand.This paper introduces the design of chemical composition,hot rolling,cold rolling and annealing process of experimental steel.The finished product property meets the technical standard,the microstructure is typical dual phase,F+M(14-16%).This product has been produced commercially in BX STEEL,and has been approved by end users.

Unified casting(UniCast)aluminum alloy—a sustainable and low-carbon materials solution for vehicle lightweighting

Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for load-bearing body and chassis components today are mostly made from primary Al with a low impurity Fe content typically less than 0.2 wt.%,owing to the requirements for high ductility and adequate fatigue strength.Primary Al is made directly from alumina which was refined from aluminum ore(bauxite),using an electrolytic process which consumes a lot of energy and produces GHG emissions that are much higher than those from steel making.The objective of this paper is to present a Unified Casting(UniCast)Al alloy concept as a sustainable materials solution for vehicle lightweighting.The UniCast alloy chemistry is intentionally designed to be more tolerant of Fe impurity.This chemistry can not only satisfy the requirements on castability,but also deliver mechanical properties needed for a variety of thin-walled and thick-walled automotive structural components that are produced by various casting processes.The UniCast alloy concept will contribute to the establishment of a closed-loop recycling system in the future as the shredded scrap obtained from the disposed end-of-life vehicles can be directly recycled back into UniCast alloy ingot with a more efficient sorting process.In addition,by setting the upper limit of Fe content in the UniCast alloy to a higher level,it will become possible to use a high fraction of post-consumer scraps to produce this alloy.To demonstrate the feasibility of this concept,an exemplary UniCast alloy chemistry has been elaborated in this article.Furthermore,challenges and future research opportunities related to the realization of UniCast alloy concept in the automotive industry are discussed.It is hoped that this article will be of great implication to industrial researchers and academicians for making concerted efforts to establish closed-loop recycling of Al castings for the automotive and other transportation industry segments.

Biomethane use for automobiles towards a CO_(2)-neutral energy system

To pursue the goal of sustainable mobility,two main paths can be considered:the electrification of vehicles and the use of biofuels,replacing fossil fuels,in internal combustion engine(ICE)vehicles.This paper proposes an analysis of different possible scenarios for automobiles towards a CO_(2)-neutral energy system,in the path of the use of biofuels and the production,distribution and use of biomethane.The study,an update of work presented previously,focuses on different scenarios that take into account numerous parameters that affect the overall efficiency of the production-and-use process.A Well-to-Wheel analysis is used to estimate the primary energy savings and reduction in greenhouse-gas emissions compared both to the use of fossil-based methane and to other fuels and automotive technologies.In particular,the study shows that the Non-Renewable Primary Energy Consumption(NRPEC)for biomethane is slightly higher(+9%)than that of biodiesel,but significantly lower than those of all the other power trains analysed:-69%compared to the battery electric vehicle(BEV)and-55%compared to bioethanol.Compared to the use of fossil natural gas,the NRPEC is reduced to just over a third(2.81).With regard to CO_(2) emissions,biomethane has the lowest values:-69%compared to BEV,-176%compared to bioethanol and-124%with respect to biodiesel.Compared to the use of fossil natural gas,the CO_(2) emissions are reduced over a third(3.55).Moreover,the paper shows that biomethane can completely cover the consumption of fossil methane for vehicles in Italy,proposing two different hypotheses:maximum production and minimum production.It is evident,therefore,that biomethane production can completely cover the consumption of fossil methane for vehicles:this means that the use of biomethane in the car can lead to a reduction in NRPEC equal to 28.9×10^(6) GJ/year and a reduction of CO_(2) emissions equal to 1.9×10^(6) t/year.