Optimisation of injection strategy, combustion characteristics and emissions for IC engines using advanced simulation technologies
Keywords: combustion, computational modelling, cycle to cycle variation, early DI Diesel engine, ignition, internal combustion engines, modelling, negative valve overlap (NVO), probability density function (PDF), SI engine modelling, stochastic reactor model (SRM),
Associated Project: Engines
Regulations concerning emissions from diesel and gasoline fuelled engines are becoming ever more stringent in all parts of the world. Historically these targets have been achieved through on-going technological development using an iterative process of computational modelling, design, build and test. Computational modelling is certainly the cheapest aspect within this process and if employed to meet more of the challenges associated with development, has the potential to significantly reduce developmental cost and timescales. Furthermore, computational models are an effective means to retain and apply often highly focused technical knowledge of complex processes within development teams thus delivering greater insight into processes. As such there is a great deal of interest in advanced simulation technologies; one such technology is srm suiteTM which has proven effective in simulating in-cylinder combustion processes to enable engineers to identify optimal injection, valve train and spark timing operating strategy to achieve a particular load-speed point with reduced target emissions. The model accounts for the impact of fuel injection strategies, detailed chemical kinetics, turbulent mixing, and heat losses on the inhomogeneities associated with the in-cylinder composition and temperature, within practical computing timescales. In order to account for the valve train dynamics and engine breathing within the context of engine cycle simulation, the srm suite has been coupled with standard 1D engine cycle simulators and applied to investigate three industry relevant problems (1) investigating cycle-to-cycle variations on emissions in an SI engine, (2) investigating emissions at different injection timings, speeds and loads in a diesel engine operated with pilot injection and high levels of Exhaust Gas Recirculation (EGR), and (3) simulating a dual injection Homogeneous Charge Compression Ignition (HCCI) engine operated with an injection (fuel reformation) during Negative Valve Overlap (NVO). In each context, computational results are compared with experimental observations and conclusions presented.
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