Charge temperature evaluation in self-ignition events

A thermodynamic method for the evaluation of charge “parcel” temperatures at the moment of self-ignition in SI engines has been applied to a series of combustion cycles which were ignited by pre-ignition events. The temperature evaluation method is based on measurement of the degree crank angle at which the rate of heat release surpasses the background noise level and numerical integration of the Livengood–Wu integral with ignition delay relations based on Arrhenius’ parameters for activation energy, temperature and pressure. A key variable of this method is the temperature “history” prior to self-ignition as such temperature history controls the heat input into the reactive gas. Results of the method, thus, provide a means to discuss pre-ignition events in view of potential root causes for charge heating including compression heating enhanced by hot spot heat transfer, the influence of intake air temperature or further mechanisms or sources of heat input.