A Study on the Mixture Formation Process and Ignition Characteristics of an Alcohol Spray in a DI Diesel Engine

Abstract

This paper revealed the reason of poor self-ignition quality of alcohol spray from the viewpoint of mixture formation considering fuel properties. Ignition characteristics of Ethanol and Diethyl Ether blended fuels were experimentally investigated with changing their blend ratio in order to clear the effects of fuel's physical and thermal properties on ignition. Experimental results and prediction of mixture formation of blended fuels showed that stoichiometric air/fuel ratio (L_th) and latent heat for vaporization (γ) were main parameters on ignition. Alcohol spray becomes lean situation faster than conventional diesel fuel such as Gas oil due to their smaller L_th. On the contrary, temperature rise of alcohol spray up to ignition point is slower than Gas oil caused by their larger γ.This causes poor self-ignition quality of alcohol spray. Namely, it is difficult for an alcohol spray to be a mixture of suitable mixing ratio and temperature for self-ignition at the same time and place.