Experimental Study on the Characteristics of Short Circuits and Restrikes of Spark Channels

Ignition performance is critical for the implementation of diluted combustion for spark-ignition engines. The short circuit and restrike phenomena can influence the initial ignition volume and discharge duration which are important for the stable ignition processes. In this study, the short circuits and restrikes of spark channels are studied with various flow velocities, spark plug gaps and discharge energies. The development of the spark channels is captured by using the direct imaging technique with a CMOS camera equipped with an image intensifier. A multi-coil ignition system is designed to enable flexible control of discharge energies. The results show that the spark plug gap size is a critical parameter to suppress the phenomena of short circuits and restrikes. With the enlargement of spark plug gap, the maximum and average lengths of the spark channel effectively increase. Meanwhile, increasing discharge power is another effective method to improve the short circuit and restrike phenomena. However, for the discharge strategy of single strike, further increasing the discharge power cannot improve the restrike phenomena. The spark channel growth rate has no correlation with the spark plug gap and the discharge energy, but linearly relating to the flow velocity around the spark plug gap. An enhanced flow velocity increases the events of short circuit and restrike. The restrike voltage increases with decrease of the discharge current or increase of the flow velocity, while, the restrike voltage is lower than the breakdown voltage of the spark onset from the same discharge process. Finally, a new spark plug prototype is given to suppress the short circuit and enhance the spark plasma channel under high-velocity flow conditions.