ÉTUDE EXPERIMENTALE ET THERMODYNAMIQUE DE L’INJECTION D’EAU A L’ADMISSION D’UN MOTEUR DIESEL AUTOMOBILE POUR LA REDUCTION A LA SOURCE DES EMISSIONS POLLUANTES

摘要

The pollutant emission reduction of automotive Diesel engine has become a difficult challenge during the last decade. NOx aftertreatmentis still complex and expensive, thus in cylinder reduction remains of interest. For that purpose, there are some wellestablished technologies, such as exhaust gas recirculation (EGR). The aim of this study is to evaluate water injection at the engineintake, which is already in use on some industrial engines.First a bibliographic survey is presented. State of the art Diesel combustion and corresponding pollutant emissions descriptions andanalyses are summarized. Previous studies on water injection are then detailed: the various techniques of water injection are describedand compared, in particular, their effects on combustion and emissions.The experimental setup is then presented. This includes the engine itself as well as the water injection system with a short history ofits development to its present, stable, form. Measurement methods are also explained and detailed.Following that, thermodynamic relations are developed to describe liquid water mixing with the intake air and its evaporation.They are used to evaluate the quantities of vaporised water in the intake track and eventually inside the cylinder, during intake andcompression strokes.Finally, the results obtained on the engine test bench with the water injection system are presented. These results are analysed andcompared to both baseline operating points and also to low-pressure exhaust gas recirculation. In light of the obtained test results,conclusions are drawn discussing the different effects of water injection on diesel engine combustion and emissions.