Effect of fuel properties on diesel spray development in extreme cold conditions

This paper presents an experimental and theoretical study with the purpose of quantifying and predicting the influence of fuel properties in extreme cold conditions on macroscopic diesel spray behaviour. The parameters studied were the fuel density and viscosity at different temperatures. Previous correlations available in the literature were analysed and extended in order to introduce the viscous term. A specific test rig that simulates the real engine in-cylinder air pressure and density was used. The fuel was injected from a convergent nozzle with eight holes at two injection pressures of 30 MPa and 120 MPa, two chamber densities of 23 kg /m(3) and 56 kg/m(3), and two temperatures of 255 K (winter) and 298 K (reference). In order to achieve cold conditions, the facility was introduced into a specialized climatic room with optical access, where the temperature and humidity were carefully controlled. The experimental results enabled the theoretical analysis that related the viscosity effect with the spray-tip penetration to be validated, obtaining high accuracy. The main conclusion of the paper is that fuel properties change significantly with the temperature in cold conditions, which affects the spray development, producing a shorter penetration in the transition stage. This phenomenon can be explained by a decrease in the fluid discharge coefficient in the outlet section of the hole as a result of the change in the fluid properties with the temperature.