Influence of Fuel Injection Pressure on Spray Characteristics of Diesel-Diethyl Ether Blends for Diesel Engine Applications: An Experimental Study

Di-ethyl ether (DEE) belongs to the family of oxygenated fuels, which have been investigated as an alternative to conventional diesel. However, increasing the proportion of DEE in DEE-diesel blends changes its physicochemical properties. This work shows the non-evaporating and non-reacting spray characteristics of diesel, DEE20 (20% v/v DEE and 80% v/v diesel), and DEE40 (40% v/v DEE and 60% v/v diesel) were investigated. The effect of fuel injection pressure (FIP: 500 and 800 bar) on the spray morphology and droplet size distribution at different axial locations along the spray axis was done. FIP of 800 bar showed a reduction in Sauter mean diameter (SMD) of spray droplets with increasing axial distance due to improved spray atomisation because of the drag forces of the surrounding air on the fuel droplets. DEE20 showed a higher number of droplets having a smaller diameter than DEE40. DEE20 and DEE40 showed superior spray atomisation characteristics than diesel. A slight increase in radial velocity was also observed with the axial location for all test fuels. DEE40 exhibited lower radial velocity compared to DEE20 and diesel. Higher fluctuation in the axial velocity of droplets was observed at an axial distance of 60 mm compared to 20 mm for diesel. This was due to increased droplet velocity distribution after the end of the injection. An increased number of smaller droplets resulted in lower jet momentum in the axial direction at the FIP of 800 bar. As a result, the average axial droplet velocity was higher at lower FIP. DEE40 showed more fluctuations amongst all test fuels, possibly due to drastic droplet diameter changes due to its superior evaporation characteristics. In this study, DEE40 at a FIP of 500 bar showed superior atomisation and evaporation characteristics. This indicated that a low-cost fuel injection system could be used for the maximum diesel replacement by DEE.