Ambient temperature and humidity effects on the performance and nitric oxide emission of spark ignition engined vehicles in Athens/Greece

Abstract

The present work investigates the effect of atmospheric temperature and humidity changes on the specific power output, specific fuel consumption and nitric oxide emissions from a typical spark-ignited petrol automotive engine. A simulation model of the combustion process and the emitted pollutants from such an engine, developed by the present author, is used. Special attention is focussed on the movement of the spherical flame front, the heat exchange of the two zones (burned, unburned), where eleven chemical species are considered, with the nitric oxide forming in a kinetically controlled manner. The analysis is modified accordingly for predicting the effect of variable humidity. The predictions of the effect of ambient temperature and humidity changes are compared, for the baseline values, with the results from a pertinent experimental investigation carried out at the laboratory of the author. The analysis is applied for typical (typical day of the month) temperature and humidity ratio values for the Athens/Greece area over one year interval, mainly to see the effect on the emitted nitric oxide which adds heavily to the acute Athens pollution problem. The investigation reveals clearly the effect of ambient temperature and humidity changes, showing good agreement with relevant reports from the literature, providing insight into the mechanisms involved.