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One of the solutions for reducing greenhouse gas emissions in the transport sector is the electrification of mobility. The technology currently most widely used by car manufacturers is the Li-ion battery (LiB). Unfortunately, Li-ion batteries can suffer dramatic events with catastrophic consequences known as thermal runaway (TR). TR has many possible causes: excessive temperature, mechanical deformation, electrical overcharge, internal short circuit. Typically, TR causes violent combustion that is difficult or impossible to control, with the emission of potentially toxic gases and particles. TR is a major problem for manufacturers and can have serious consequences for users. Understanding TR is a key safety issue. This paper presents a new methodology to characterize the thermal runaway of Li-ion battery cells, combining gas analysis, thermodynamic measurements and high-speed imaging.

The electrification of mobility is a major inflection point for reducing greenhouse gas emissions and air pollutants from the transportation sector. In this context, the Li-ion battery is currently the technology shared by automakers to provide the energy storage needed to deploy electrified vehicles. However, Li-ion batteries can undergo incidents with dramatic consequences, referred to as thermal runaway (TR). This can result from abnormal conditions: excessive temperature, mechanical deformation, electrical overcharge, internal short circuit. TR is characterized by a violent reaction, that is, difficult to control and can release hazardous gases. This issue is today a crucial safety concern that strongly impacts the design and the battery management strategies. The objective of this study is to contribute to the understanding of the phenomena by focusing on the variability of the battery cell (BC) TR induced by thermal initiation.

The potential of ozone addition in compression ignition engines is investigated experimentally in this paper. Experiments were carried out in an optically accessible single cylinder engine equipped with a common rail direct injection system. A commercially available ozone generator (P < 100W) was used to add to the intake flow a controlled amount of ozone. EU Diesel fuel (cetane number 52) and a Naphtha fuel (cetane number 33) were tested investigating the impact of Ozone in conventional diesel combustion and LTC cases (e.g. high exhaust gas recirculation rate). Minimal ozone concentration in the intake flow (100 ppm) demonstrated to reduce significantly the ignition delay. However, the impact observed strongly depends on the engine conditions tested and, in general, this effect observed becomes significant in conditions characterized by a long ignition delay: low intake temperature, high dilution, and low cetane number fuel.

This paper is a contribution to the understanding of the formation and oxidation of soot in Diesel combustion. An ECN spray A injector (single axial-oriented orifice) was tested in a well characterized high-temperature/high-pressure vessel at engine relevant conditions. The size of the test section (>70mm) enables to study the soot formation process in nearly free field conditions, which constitutes an ideal feature for fundamental understanding and model validation. Simultaneous high-speed OH* chemiluminescence imaging and high-speed 2D extinction were performed to link together the information regarding flame chemistry (i.e. lift-off length) and the soot data. The experiments were carried out for a set of fuels with different CN and sooting index (Diesel fuel, Jet fuel, gasoline and n-dodecane) performing parametric variations in the test conditions (ambient temperature and oxygen concentration).

An existing three-stage ignition delay model which has seen successful application to Primary Reference Fuels (PRFs) has been extended to six surrogate fuels which constitute potential candidates for future Homogeneous Charge Compression Ignition (HCCI) engines. The fuels include petroleum-derived and oxygenated components and can be divided into low, intermediate and high cetane number groups. A new methodology to obtain the model parameters is presented which relies jointly on simulation and experimental data: in a first step, constant volume adiabatic reactor simulations using chemical kinetic mechanisms are performed to generate ignition delays for a very wide range of conditions, namely variations in equivalence ratio, Exhaust Gas Recirculation (EGR), pressure and temperature.

The Engine Combustion Network (ECN) has become a leading group concerning the experimental and computational analysis of engine combustion phenomena. In order to establish a coherent database for model validation, all the institutions participating in the experimental effort carry out tests at well-defined boundary conditions and using wellcharacterized hardware. In this framework, the reference Spray A injectors have produced different results even when tested in the same facility, highlighting that the nozzle employed and its fouling are important parameters to be accounted for. On the other hand, the number of the available Spray A injectors became an issue, due to the increasing number of research centers and simultaneous experiments taking place in the ECN community. The present work has a double aim: on the one hand, to seek for an appropriate methodology to “validate” new injectors for ECN experiments and to provide new hardware for the ECN community.

Transients in the rate of injection (ROI) with respect to time are ever-present in direct-injection engines, even with common-rail fueling. The shape of the injection ramp-up and ramp-down affects spray penetration and mixing, particularly with multiple-injection schedules currently in practice. Ultimately, the accuracy of CFD model predictions used to optimize the combustion process depends upon the accuracy of the ROI utilized as fuel input boundary conditions. But experimental difficulties in the measurement of ROI, as well as real-world affects that change the ROI from the bench to the engine, add uncertainty that may be mistaken for weaknesses in spray modeling instead of errors in boundary conditions. In this work we use detailed, time-resolved measurements of penetration at the Spray A conditions of the Engine Combustion Network to rigorously guide the necessary ROI shape required to match penetration in jet models that allow variable rate of injection.

This publication is the result of a multidisciplinary collaboration between the academia and the industry. An attempt to pre-ionize and influence the trajectory and the fluid mechanics of the injected fuel into an experimental injection system by means of electromagnetic fields was made. This collaboration project started from research proposal, which aims at exploring the effects of a highly ionized environment on the fuel injection event and how the momentum of the injected fuel droplets may be affected by the electromagnetic fields in form of quantified variables, such as spray penetration, spreading angle and the spray axis angle. An influence of the applied electromagnetic field on the fuel spray depending on the electrode configuration was observed and is presented and discussed in this publication.