Thermal Ignition Promotion by Spark Discharge Synchronized with LTO

Abstract

A possibility of thermal ignition promotion by an interaction between low-temperature oxidation and spark discharge was investigated. A homogeneous-charge compression and expansion machine fueled with n-C7H16 was operated at equivalence ratio of 0.33 so that low-temperature oxidation appeared but thermal ignition didn't in it. A spark discharge was done at the center of a combustion chamber, synchronized with LTO preparation, LTO (low-temperature oxidation) or thermal ignition preparation of a fuel oxidation process. With the discharge at LTO, a rise of pressure was observed, showing that thermal ignition was induced by the discharge. In the atmosphere of LTO to thermal ignition preparation, a propagating flame was formed by the discharge even under the lean condition beyond the general flame propagation limit. The flame compressed the end gas in the atmosphere of thermal ignition preparation, resulting in the thermal ignition in an end gas zone. It is considered that activation of H₂O₂ loop reactions by the compression promoted the thermal ignition.