Fuel effect on the liquid-phase penetration of an evaporating spray under transient diesel-like conditions

Abstract

Measurements of the maximum liquid-phase penetration have been performed injecting five different fuels through a single-hole nozzle in an optical engine under a large set of thermodynamic and injection conditions. The focus of this paper is twofold. First, it intends to study fuel physical properties on liquid-phase fuel penetration. The choice made on Fischer-Tropsch diesel (FTD) and biodiesel fuels has been highly motivated by their potential to be, at short or middle term, possible substitutes to the conventional diesel fuel. Extensive characterization of fuel physical and chemical properties under ambient conditions are provided and related to the liquid-phase penetration in order to provide an accessible tool to predict liquid spray behavior based on cheap, off-engine measurements. Fischer-Tropsch fuels appeared to be the easiest to vaporize while biodiesel blends were getting always harder to vaporize as the Rapeseed Methyl Ester (RME) rate was increased. The second objective of this work is to study the time-response of liquid-phase penetration when subjected to density and temperature variations. Injections of 8 ms at three different pressures have been performed in transient diesel-like conditions with density and temperature time derivatives up to 2000 kg m -3 s -1 and 20,000 K s -1. In most cases, the spray appeared to closely follow predictions made from empirical models built out of steady-state ambient conditions, leading to the conclusion of an instantaneous adjustment of the spray to its environment, validating: (1) the hypothesis made in 1D spray models; (2) the use of empirical models in unsteady-state environment when obtained under steady-state conditions.