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Abstract:The PEM fuel cell model presented in this paper is based on modelling species transport and coupling electrochemical reactions to species transport in an innovative way. Species transport is modelled by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the gas-flow and coupling consecutive 2D solutions by means of a 1D numerical gas-flow model. The 2D solution is devised on a jigsaw puzzle of multiple coupled domains which enables the modelling of parallel straight channel fuel cells with realistic geometries. Electrochemical and other nonlinear phenomena are coupled to the species transport by a routine that uses derivative approximation with prediction-iteration. A hybrid 3D analytic-numerical fuel cell model of a laboratory test fuel cell is presented and evaluated against a professional 3D computational fluid dynamic (CFD) simulation tool. This comparative evaluation shows very good agreement between results of the presented model and those of the CFD simulation. Furthermore, high accuracy results are achieved at computational times short enough to be suitable for system level simulations. This computational efficiency is owed to the semi-analytic nature of its species transport modelling and to the efficient computational coupling of electrochemical kinetics and species transport.

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The paper presents a comprehensive study on engine performance improvement attributable to application of different electrically assisted turbocharger topologies. Performance of a baseline turbocharged high-speed direct-injection (HSDI) diesel engine is compared to the performance of an engine utilizing an electrically assisted turbocharger, an engine utilizing a turbocharger with an additional electrically driven compressor, and an engine utilizing an electrically split turbocharger. Analyses are performed based on a validated physically based engine and vehicle model comprising detailed models of all vehicle components, thus ensuring adequacy of results. Analyses are performed for various driving conditions, including tip-in in the fixed gears and the new European drive cycle (NEDC). Results reveal that electrically assisted turbocharger topologies improve transient response of the engine and thus driveability of the vehicle. Additionally, over a limited period of time, electrically assisted turbocharger topologies are able to improve steady-state torque output of the engine with retained fuelling, which is made possible by the availability of energy in electric storage devices. It was also revealed that the utilization of electrically split turbocharger enables considerable reduction in fuel consumption when driven according to urban drive cycles.

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System level simulations, which are gaining on importance in the product concept design process and in the “Hardware‐in‐the‐Loop” (HiL) applications, require models that feature high level of accuracy, high level of prediction capability and short computational times. This paper presents an innovative mechanistic quasi 3D model capable of real time computation of steady state and transient fuel cell operation. This model relies on a hybrid 3D analytic‐numerical model (HAN) approach, which models species transport by taking 1D numerical model for pipe gas‐flow and superimposing onto it a 2D analytic solution for concentration and velocity distribution in the plane perpendicular to the gas‐flow. The main innovative contribution of this paper comprises a significant mathematical reduction of the previously published HAN approach to a computationally optimized approach featuring a minimal amount of computational points yielding a real‐time capable model (denoted HAN‐RT), which complies with 1kHz HiL constraints while retaining HAN's quasi 3D nature. Presented results confirm that the computationally optimized HAN‐RT model displays real‐time capabilities at sampling rates above 1 kHz while producing results that agree very well with spatially resolved results generated by the 3D multiphase CFD tool and with the experimental results of steady state and transient fuel cell operation.