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Background

Economical, geopolitical and social trends mandate electrification of vehicles. However, the constantly increasing energy needs associated with the expansion of urbanisation, population growth and the ever increasingly transportation needs in developing economies, are/will be met by medium/large Diesel internal combustion engines (ICE), for which no foreseen electrification strategy is in place. As a result, hydrocarbon sources are expected to cover more than 2/3rds of the total energy usage in the next two decades. Currently, Diesel engines are responsible for ~30wt% of soot and ~17% of man-made CO2 emissions. Despite the immense reduction achieved, soot is one of the deadliest forms of air pollution: such particles inhaled at city centres, are linked to serious health effects, including premature death, heart attacks and strokes, as well as acute bronchitis and aggravated asthma among children. To mitigate the inevitable environmental/health effects, partial substitution of conventional Diesel engines by high-octane liquid or gaseous fuel with lower carbon-to-hydrogen ratio represents the only practical and imminent solution. The so-called dual-fuel internal combustion engines (DFICE) primarily burn a premixed high-octane fuel/air mixture or even hydrogen, with a moderate quantity of pilot high-cetane fuel employed only as an ignition agent. DFICE have applications to a non-exhaustive list of applications, including power generation, cargo ships and tankers, light and heavy duty trucks, tractors, earth-moving machines and haul trucks. Utilisation of such fuel mixtures can allow engine operation that satisfies the strictest emission legislation e.g. EURO VI or Tier IV standards, in Europe and in the US, respectively; moreover, they comply with the Tier III limit of the International Maritime Organization (IMO) that dictates further reduction of NOx emitted by marine engines. Utilisation of a high-octane fuel or hydrogen produces virtually no soot. Moreover, it assists the oxidation of soot formed due to the liquid-fuel combustion. The margin for emissions reduction from DFICE has been found to be significant and lying in the range of 20-80% for NOx/PM emissions and 10-50% for CO2 (depending on the degree of bio-fuel/hydrogen utilisation) without significant penalty in their performance compared to conventional operation. To achieve this, fuel injection equipment (FIE) configurations for DFICE have been developed over the years; the vast majority of them falls within two broad configurations: New injection strategies pose new challenges for the design of injectors that must be capable of handling Diesel fuel in the, so called, ballistic mode, where short injection duration under high pressure must be accomplished. Referring to gaseous fuels, natural gas (NG) and hydrogen are widely employed candidates to serve as primary fuels in DFICE. To achieve these targets, development of computational models suitable for the design of DFICE and their FIE represents a key priority.

Motivation

Computational fluid dynamics (CFD) models have been long utilised for the design of efficient ICE. However, existing models fail to predict processes where a variety of fuel mixtures are injected and combust simultaneously. This is due to simplifications made for the mixing, phase-change and combustion, which all are happening at scales not resolved by the grid resolution and require sub-grid scale physical modelling. The EDEM proposed programme is aiming to develop such models, which in turn will be utilised by engine and FIE manufacturers for the design of DFICE. The programme is international (includes partners from the EU, US, China, UAE and S. Korea), interdisciplinary (includes partners from manufacturers and ship operators, modellers and experimentalists working in diverse areas) and inter-sectoral (includes academic and non-academic institutions). The proposed studies provide a unique training opportunity to the ESRs to: (a) obtain new experimental data by utilising the most advanced experimental techniques, (b) develop, improve and validate new state-of-the-art CFD models and (c) trained in industrial practice on site at the non-academic partner institutions, which is expected to enhance their career perspectives.