Combustion control and mechanism with direct injection of reaction suppressors in a premixed charge compression ignition engine

Abstract

Direct in-cylinder injection of reaction suppressors was effective to successfully control ignition timing and suppress rapid combustion in a premixed charge compression ignition (PCCI) engine. The experimental results showed that the reaction suppressor injection significantly reduced the heat release at low-temperature oxidation reactions which suppressed an increase in the charge temperature after the onset of low-temperature oxidation reactions and in the rapid combustion. Chemical kinetic modeling showed a reduction of OH radical concentration before the onset of low temperature oxidation with injection of suppressors. Among the various ignition suppressors, alcohols had a greater impact on OH radical reduction resulting in stronger ignition suppression than other oxygenated and unoxygenated hydrocarbons, water, and hydrogen. The mechanism of the low temperature oxidation suppression with alcohols was considered to be caused by the consumption of OH radical reacting with hydrogen atom in alcohol molecules.