Numerical investigation of the effect of the spark plug electrode gap on flame propagation under engine-like conditions

Resumo

© 2023 American Society of Mechanical Engineers (ASME). All rights reserved.To attend the high demand for high performance, low fuel consumption, and low emissions, ethanol has become a potential candidate to replace gasoline applications worldwide. In this scenario, ethanol market share has increased in two spaces, blended with gasoline, where the goal is just to increase the knock limit during engine operation, and then leverage the thermal efficiency, or in its pure form, where the benefits of its green characteristics contribute significantly to Green House Gas (GHG) credits benefitting car manufacturers. The objective of this research is to analyze the effects of different spark plug conditions, representing nominal and outwearing conditions, on flame propagation in engine-like conditions applying numerical modeling. The commercial software STAR-CD is adopted for the 3D Computational Fluid Dynamics (CFD) model mimicking the Direct Injection Spark Ignition (DISI) optical engine adopted for the experimental tests. The numerical model adopts a 3-Zones Extended Coherent Flame (ECFM-3Z) and Imposed Stretch Spark Ignition Model (ISSIM), for the combustion and the spark plug modeling, respectively. The engine operating conditions adopted consist of direct injection of ethanol (E100) partial load and low speed. The model was built and validated according to experimental measurements. Afterward, the tuned model was used to study a set of cases intended to evaluate how different spark plug discharge energy and electrode gaps influence flame propagation in engine-like conditions. The results obtained identified the influence of non-optimal spark plug conditions in combustion propagation and indicated the influence of the parameters studied in engine performance.

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