Browse Publications Technical Papers 2019-24-0007
2019-09-09

Numerical Investigation of Methanol Ignition Sequence in an Optical PPC Engine with Multiple Injection Strategies 2019-24-0007

Methanol fuel is a genuine candidate on the alternative fuel market for internal combustion engines within heavy-duty transportation sector. The thermo-physical properties of methanol allow to achieve high thermodynamic efficiency and low emission levels with a good margin below the EURO VI standard using compression ignition (CI) engines with advanced injection strategies. However, due to a low stoichiometric air/fuel ratio and a high latent heat of vaporization there are two challenges that can be mentioned; (a) the tendency to a high pressure rise rate due to the rapid chemical kinetic driven ignition process and, (b) the required high inlet temperature to initiate compression ignition event. These challenges can be tackled for instance by employing multiple-injection strategies, which reduces both the maximal pressure rise rate and the demand on the high inlet temperature. In this paper numerical simulations and heavy-duty optical engine experiments are used to study multiple-injection strategies in terms of mixing and combustion characteristics of neat methanol. The injection strategies are selected to achieve a comparable combustion phasing and engine load in all studied cases with single, double and triple injection strategy. It is showed that by employing various pilot/main injections, the fuel/air mixture conditions become optimally stratified, which in turn reduces the velocity of reaction front propagation. It is also found how the combustion mode can switch between ignition driven and mixing controlled giving a significant impact on the engine performance.

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