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This paper presents a novel methodology to investigate engine behaviour using an original numerical approach based on the direct temporal coupling between IFP-ENGINE, a 1D engine simulation tool used for the simulation of the gas exchange system, and IFP-C3D, a 3D CFD code used to simulate combustion and pollutant emissions. The coupling method is used to compute steady conditions of the whole engine dynamic system but could also be applied for transient operating conditions. To demonstrate the capabilities of the model a 4-cylinder turbocharged gasoline engine is modelled at two different operating points and the comparison with experimental measurements is shown.

Meeting diesel engine emission standards for heavy-duty vehicles can be achieved by simultaneous injection of fuel and water. An injection system for instantaneous mixing of fuel and water in the combustion chamber has been developed by injecting water in a mixing passage located in the periphery of the fuel spray. The fuel spray is then entrained by water and hot air before it burns. The experimental work was carried out on a Rapid Compression Machine and on a Komatsu direct-injection heavy-duty diesel engine with a high pressure common rail fuel injection system. It was also supported by Computational Fluid Dynamics simulations of the injection and combustion processes in order to evaluate the effect of water vapor distribution on cylinder temperature and NOX formation. It has been concluded that when the water injection is appropriately timed, the combustion speed is slower and the cylinder temperature lower than in conventional diesel combustion.

In the present work, a model with the thermophysical properties of Heavy Fuel Oil, typically used in marine diesel engines, has been developed and implemented into the KIVA CFD code. The effect of fuel properties on spray atomization is investigated by performing simulations in a constant-volume high-pressure chamber, using the E-TAB and the USB breakup models. Two different nozzle sizes, representative of medium- and low-speed marine diesel engines, have been considered. The simulations have been performed for two values of chamber pressure, corresponding to operation at partial and full engine load. The results indicate that, in comparison to a diesel spray, the Heavy Fuel spray is characterized by comparable values of penetration length, and larger droplet sizes. These findings are correlated to experimental results from the literature.

The reduction of pollutant emissions of marine diesel engines can be achieved by employing multiple injection strategies, similar to the ones used in automotive engines. In the present work, the options for advanced injection strategies, in terms of pilot injections, are explored for a large two-stroke marine diesel engine operating at full load, by utilizing Computational Fluid Dynamics simulations coupled with an Evolutionary Algorithm. The goals of the present Multi-Objective constrained optimization are the minimization of nitrogen oxides (NOx) emissions and engine specific fuel consumption. The constraint, imposed by structural limitations of the engine, is the maximum cylinder pressure. The design variables include parameters controlling the pilot and main injections, and the injected total mass. The problem is handled as a Multi-Objective Optimization Problem, and the final set of elite solutions is identified based on the Pareto dominance.

A numerical study has been conducted to investigate possible extension of the low load limit of the HCCI operating range by charge stratification using direct injection. A wide range of SOI timings at a low load HCCI engine operating condition were numerically examined to investigate the effect of DI. A multidimensional CFD code KIVA3v with a turbulent combustion model based on a modified flamelet approach was used for the numerical study. The CFD code was validated against experimental data by comparing pressure traces at different SOI’s. A parametric study on the effect of SOI on combustion has been carried out using the validated code. Two parameters, the combustion efficiency and CO emissions, were chosen to examine the effect of SOI on combustion, which showed good agreement between numerical results and experiments. Analysis of the in-cylinder flow field was carried out to identify the source of CO emissions at various SOI’s.

In the present work, the effects of water introduction in a large two-stroke marine diesel engine operating at full load are studied via Computational Fluid Dynamics, utilizing a modified version of the KIVA-3V code. The impact of two techniques, namely intake air fumigation and Direct Water Injection (DWI) on pollutant emissions and Specific Fuel Oil Consumption (SFOC) is investigated. It is concluded that DWI is more effective in reducing NOx emissions; however, its performance in terms of soot emissions and SFOC is inferior. The analysis shows that the 2016 NOx emission standards set by the International Maritime Organization, dictating an 80% reduction, could be met with water addition strategies. The present results demonstrate the potential of water addition techniques, and suggest that a substantial improvement of engine operation with optimized water addition strategies may be feasible.

Modern diesel engines operate under injection pressures varying from 30 to 200 MPa and employ combinations of very early and conventional injection timings to achieve partially homogeneous mixtures. The variety of injection and cylinder pressures results in droplet atomization under a wide range of Weber numbers. The high injection velocities lead to fast jet disintegration and secondary droplet atomization under shear and catastrophic breakup mechanisms. The primary atomization of the liquid jet is modeled considering the effects of both infinitesimal wave growth on the jet surface and jet turbulence. Modeling of the secondary atomization is based on a combination of a drop fragmentation analysis and a boundary layer stripping mechanism of the resulting fragments for high Weber numbers. The drop fragmentation process is predicted from instability considerations on the surface of the liquid drop.