NOx and PM emissions reduction on an automotive HSDI Diesel engine with water-in-diesel emulsion and EGR: An experimental study

摘要

Automotive Diesel engines exhaust emissions must constantly be reduced to comply with more and more stringent regulations, all over the world. The introduction of water in the combustion chamber is already used on some large marine diesel engines to cut down NOx emission. In this paper an experimental study is conducted on a modern automotive 1.5 1 HSDI Diesel engine while injecting a water-in-diesel emulsion (WDE) with a volumetric water-to-fuel ratio of 25.6%. Four injection strategies are considered with and without pilot injection, with two levels of injection pressure. First, the injection of WDE is compared to diesel-fuel in terms of combustion and NOx and PM emissions without using exhaust gas recirculation (ECR). Depending on the WDE fuelling rate and injection strategy (with or without a pilot injection before main injection), NOx emissions are most often reduced (of up to 50%), and PM emission are most often decreased as well (the maximum relative reduction being 94%). The combustion is largely affected by the injection of WDE as compared with pure diesel-fuel, the main observations being an increased of the ignition delay and an improved mixing-process between the fuel and the surrounding gases. After that, the use of WDE in parallel with EGR (with various EGR rates) is tested with the aim at improving the NOx-PM trade-off (reduction of NOx emission at a given PM emission level or reduction of PM emission at a given NOx emission level). The results show that this method is an effective way for NOx and PM emission reduction on an automotive Diesel engine.