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The present work is focused on getting insight into premixed hydrogen fueled spark ignition engine using numerical simulations. Combustion simulations with reduced kinetics have been validated with experiments and the validated model has been used for a parametric study. A clear transition in combustion characteristics has been observed at a threshold of 0.6 equivalence ratio. Flame propagation speed has been estimated by image processing OH mass fraction contours from simulations. This has been compared to laminar flame speed obtained from 1D tools to understand the transition of flame towards turbulent. NO formation has been observed to increase till an equivalence ratio of 0.8 due to an increase in flame temperature and decrease with further increase in equivalence ratio due to late cycle dissociation. The findings reported in this study shall be helpful in optimizing combustion systems for hydrogen fueled spark ignition engines to overcome flame extinction and reduce NO emissions.

Detailed soot models based on method of moments have been reported for combustion engines for more than twenty years. However, these models have always been validated against soot measured at exhaust and none of the modeling works have validated the spatial and temporal evolution of modeled soot with in-cylinder data. In this article a soot model based on method of moments has been evaluated by comparing simulations with the published experimental data for varying operating conditions of the heavy-duty optical engine at Sandia National Laboratories. Closed cycle combustion simulations have been performed using CONVERGE, a computational fluid dynamics solver for reacting multiphase flows. Before modeling soot, confidence in non-reactive modeling has been ensured by validating spray and equivalence ratio distributions from simulations with experimental optical images at different crank angles for each operating condition.

The mixture generation in Diesel engines is mainly driven by the combustion chamber geometry and the fuel spray characteristics. Thus, combustion chamber geometry is considered as an important parameter for Diesel engine in-cylinder emission control strategy. In this work, effect of nozzle tilt angle and various combustion chamber geometries such as mexican-hat combustion chamber (MHCC), double-lip combustion chamber (DLCC), bow combustion chamber (BCC) and toroidal combustion chamber (TCC) on in-cylinder processes and emissions has been studied numerically using a CFD-tool called Converge. Converge code has been validated against the experimental results of a Diesel engine. Results showed that a significant reduction in soot, HC and CO has been achieved with the optimum (156°) nozzle tilt angle; but NOx was increased.

In this work, optimization of various parameters, such as injection timing, compression ratio (CR) and amount of ultra-cooled exhaust gas recirculation (EGR) has been done for a variable compression ratio engine. The CR can be adjusted dynamically by changing the clearance volume through a tilting cylinder block arrangement. An EGR system, suitable for achieving ultra-cooled as well as treated EGR and large range of flow rates, has been implemented. Taguchi analysis was employed to carry out minimum number of experimental runs and still get the essence of large number of test cases. Effect of these parameters on engine performance and exhaust emissions has also been studied with the help of signal to noise (SN) ratio analysis. Flatter and wider HRR traces were observed in previous work of Brijesh et al., indicating a low temperature combustion (LTC) mode for the runs having optimized input parameters.