High-ignitability spark plugs are increasingly being used in high-efficiency gasoline engines. However, studies regarding combustion simulation for predicting spark plug effectiveness, which consider the engine conditions and misfire phenomenon, are rare. Therefore, a method was developed for predicting ignitability through simulation of the spark plug using detailed chemical kinetics.
In this method, the ignition process is initiated by introducing an energy source obtained from actual discharge waveforms into the spark discharge region. Detailed chemical kinetics are considered for prediction of misfires.
Schlieren photographs and calculation results were compared and analyzed, targeting propane fuel combustion in the combustion chamber. The predictability of the effect of plug shapes and discharge positions on ignitability was confirmed for two types of spark plugs in a static field. Spark curves and ignitability are significantly affected in flow fields. Hence, a curved spark program was developed. The effects of flow velocity and ground electrode orientation on ignitability were simulated successfully.
Next, predictions of the effects of engine conditions and ground electrode orientations were confirmed by comparing the measurement results obtained through particle image velocimetry and the flow simulation results of an optically accessible engine. Ethane (C2H6) was adopted as fuel surrogate for gasoline based on the result of 0D and 1D simulations.
Lastly, we modeled gasoline engine combustion to determine the effectiveness of two types of spark plugs with different ground electrode shapes. Based on this, we developed a method to predict spark plug effectiveness through simulation.