Comparison of spray characteristics for diesel and its blends with diethyl ether: an experimental study

Compression ignition (CI) engines have wide applications and are explored for alternative fuels as the sources of fossil fuels are anticipated to be exhausted within a few decades. Using alternative fuels that are cheaper and more sustainable to replace conventional fossil fuels has captured the attention of researchers. Diethyl ether (DEE) is explored in the present study for partial replacement of diesel. Fuel spray development starts with liquid fuel being injected into an environment at high pressure and temperature. After fuel injection, the spray approaches the cylinder liner, while it interacts with the hot ambient air leading to the fuel vaporization and followed by combustion. Spray atomization has a great effect on the spray's local mixture formation, which influences spray penetration and structure. The present study investigates the spray characteristics of diesel and its blends with DEE under various fuel injection pressure (FIP) and ambient pressure (Pamb). The spray parameters like liquid axial penetration, radial penetration, spray area, and droplet diameter were investigated experimentally. Macroscopic results revealed lower axial penetration and spray area for DEE40 due to its lower viscosity, density, and surface tension. However, radial penetration was higher for DEE40 due to more dispersion of finer droplets in the radial direction. A higher FIP of 1200 bar showed longer axial and shorter radial penetration compared to 700 bar. This is due to the formation of finer droplets at higher FIP, which are losing their momentum in an axial direction and getting dispersed due to air entrainment in a radial direction. The atomization of diesel spray was improved by the introduction of DEE. The droplets with the addition of DEE spray showed a smaller diameter, reducing the spray inertia and thus resulting in a lower liquid penetration. The higher FIP of 1200 bar and/or DEE40 spray showed lower chances of droplet coalescence with increasing Pamb from 10 to 30 bar. This study strongly suggests the blending of DEE in conventional diesel for improving the atomization and evaporation properties of the fuel spray.