Errors in NO Emission Prediction from Spark Ignition Engines

An extensive literature survey has been made of the formation mechanisms involved in NO generation within the flame front (“prompt NO”) and in the post-combustion gases. Computer models having a uniform temperature and composition in the burnt charge are showm to be inaccurate in predicting NO. Improvements can be achieved by the incorporation of a one-dimensional temperature gradient and partial mixing in the burnt gases. However, the development of models in which heat transfer is confined to a multi-element “thermal boundary layer” is required for the most accurate predictions. Limited results from one such model are presented.