Abstract
Diesel engines NOx and particulate emissions are subject to regulatory standards which will decidedly become more stringent in coming years. One solution to reduce both pollutant emissions is the use of alternative fuels like fuel-water emulsions. The objective of the work presented is to evaluate the potential of Aquazole TM , a 13%-water content emulsion developed by Elf, to improve the combustion process in a high-speed direct injection Diesel engine with a high pressure common-rail injection system (HDI engine from PSA Peugeot-Citroën).The study, based on the comparison between standard fuel and Aquazole TM is divided into three steps:
- Characterisation of the fuel influence on the hydrodynamics of the common-rail injection system and on the injection rate shape.
- Characterisation of the fuel influence on the macroscopic behaviour of the spray (tip penetration, air entrainment ) and on the atomisation process. The tests are performed in a high-density gas injection rig with high-speed visualisation and PDA analysis.
- Determination of the final influence on the combustion process, due to the modification of the injection characteristics and the properties of the Aquazole TM . The combustion characterisation is performed in a single cylinder HDI Diesel engine, mainly through heat release law analysis and pollutant measurements. The tests are performed in a wide range of operative conditions, from idle to full load.
The tests performed on the HDI single cylinder in hot conditions gave the following trends: the balance of the use of Aquazole TM is variable as a function of operative conditions but is globally positive, with no negative effect on the engine efficiency, a slight reduction of the combustion noise, at part load, a decrease of the NOx and an important improvement in smoke emission, particularly at full load conditions.
This global study of the whole injection-combustion process allows identifying the main effects of Aquazole TM on pollutant emissions on a HDI engine.