In recent years there has been an increased interest in improving the thermal efficiency of spark ignition engines. Several solutions have been proposed, predominantly focused on igniting a fuel-air mixture under very lean conditions with minimal cyclic variability. Introducing a cross flow within the spark gap has shown to reduce the combustion fluctuations / cyclical variability by shortening the initial ignition period. &nbsp;Increased flow velocity stretches the spark channel, increasing the total volume within the fuel-air mixture effectively activated by the high-temperature plasma kernel. However, it is also found that large cross-flow velocities can cause the spark to blowout or restrike, resulting in a misfire, in which case the desired volumetric activation effect is not achieved. Predicting the spark stretch and restrike behavior under different operating conditions requires a fundamental understanding of the plasma physics, fluid dynamics, and circuit characteristics that simultaneously play a role in determining the evolution of the spark channel.This work presents a study of spark discharges in high cross-flow ignition environments using a high-fidelity, multi-physics equilibrium plasma solver VizSpark™. The VizSpark™ computational framework is designed to simultaneously model chemically reacting fluid flow coupled with electromagnetics, surface ablation physics and external circuit dynamics in a fully coupled manner. The VizSpark™ model predicts key parameters associated with the spark discharge such as the spark gap breakdown voltage, dwell current, restrike timing, and spark stretch, under different cross-flow velocities and operating pressures. The simulation domain, based on experiments by Shiraishi et al. &nbsp;[1], consists of a spark plug in a constant volume test chamber with a variable speed fan located at the chamber inlet. Spark channel simulations are performed over operating pressures ranging from 1-5 bar and cross flow velocities between 0 and 10 m/s. &nbsp;The generalizability of the spark simulation model is demonstrated by comparing the maximum spark channel length before restrike, time to first restrike, average dwell current and restrike voltage with experimental measurements for different operating conditions.&nbsp;[1] Shiraishi, Taisuke, Atsushi Teraji, and Yasuo Moriyoshi. "The effects of ignition environment and discharge waveform characteristics on spark channel formation and relationship between the discharge parameters and the EGR combustion limit."&nbsp;SAE International Journal of Engines&nbsp;9, no. 1 (2016): 171-178.

Multiphysics Modeling of Spark Discharges in High Crossflow Ignition Environments

Paper Proceedings: https://asmedigitalcollection.asme.org/ICEF/ICEF2021/volume/85512

ASME 2021 Internal Combustion Engine Division Fall Technical Conference (ICEF2021)

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