Asymptotic analysis of detonation development at SI engine conditions using computational singular perturbation

The occurrence and intensity of the detonation phenomenon at spark-ignition (SI) engine conditions is investigated, with the objective to successfully predict super-knock and to elucidate the effect of kinetics and transport at the ignition front. The computational singular perturbation (CSP) framework is employed in order to investigate the chemical and transport mechanisms of deflagration and detonation cases in the context of 2D high-fidelity numerical simulations. The analysis revealed that the detonation development is characterised by: (i) stronger explosive dynamics and (ii) enhanced role of convection. The role of chemistry was also found to be pivotal to the detonation development which explained the stronger explosive character of the system, the latter being an indication of the system's reactivity. The role of convection was found to be enhanced at the edge of the detonating front. Moreover, the increased contribution of convection was found to be related mainly to heat convection. Remarkably, the detonation front was mainly characterised by dissipative and not explosive dynamics. Finally, diffusion was found to have negligible role to both examined cases

Computational analysis of an HCCI engine fuelled with hydrogen/hydrogen peroxide blends

In the current work, Chemkin Pro's HCCI numerical model is used in order to explore the feasibility of using hydrogen in a dual fuel concept where hydrogen peroxide acts as ignition promoter. The analysis focuses on the engine performance characteristics, the combustion phasing and NOx emissions. It is shown that the use of hydrogen/hydrogen peroxide at extremely fuel lean conditions (φeff = 0.1 − 0.4) results in significantly better performance characteristics (up to 60% increase of IMEP and 80% decrease of NOx) compared to the case of a preheated hydrogen/air mixture that aims to simulate the use of a glow plug. It is also shown that the addition of H2O2 up to 10% (per fuel volume) increases significantly the IMEP, power, torque, thermal efficiency (reaching values more than 60%) while also decreasing remarkably NOx emissions which will not require any exhaust after-treatment, for all engine speeds. The results presented herein are novel and promising, yet further research is required to demonstrate the feasibility of the proposed technology

Abstracts Of The Proceedings And The Posters From The Third Scientific Session Of The Medical College Of Varna

October 2-3, 201