The Use of Emulsion, Water Induction and EGR for Controlling Diesel Engine Emissions

A comparative experimental investigation into the use of water-in-diesel fuel emulsion, inlet manifold water induction and Exhaust Gas Recirculation (EGR) as means of controlling diesel engine emissions has been carried out. The tests were performed on a 2.5 l, four-cylinder, direct injection Ford diesel engine. The engine was modified to incorporate a water injection system into the air intake and an EGR system. Water-in-fuel emulsion was prepared by mixing and circulating the mixture for an appropriate length of time prior to injection into the engine. A computerised data acquisition system capable of logging the engine performance parameters (cylinder pressure, engine speed, engine load … etc) was also developed and used to obtain the required data. The amount of water in the emulsion was varied, as was the amount of water introduced into the intake manifold and the amount of EGR. The exhaust emissions from the engine were analysed for smoke, NO_X, uHC, CO, CO₂ and oxygen.

The findings of this study are presented in this paper. The results from all the tests are discussed and compared. The advantages and disadvantages of each method are highlighted and the most suitable method for a particular set of engine operating conditions is identified. It is shown that while EGR can effect a substantial reduction in NO_X emissions; this is achieved at the expense of increased smoke. Water induction on the other hand can result with up to 60% reduction in NO_X at no real cost in terms of engine performance or other pollutants. The use of emulsified fuel is seen to effect reductions in both NO_X and smoke at no cost to the engine performance (as indicated by specific fuel consumption and thermal efficiency). It is concluded that the use of emulsified fuels or a combination of EGR and water addition could prove beneficial in terms of controlling diesel engine emissions.