Self-Ignition of Diesel Sprays and Its Dependence on Fuel Properties and Injection Parameters

Abstract

The self-ignition process in diesel engines is influenced by many parameters, which are partially interrelated. In order to separate the influence of basic parameters, a special high-pressure, high-temperature vessel has been designed that allows injection in short intervals under defined and repeatable conditions. The evaluated parameters include: cetane number, viscosity and volatility, vaporization behavior, and ignition improving additives. In addition to other factors, the investigations showed that the cetane number itself is not sufficient to characterize the self-ignition properties especially of heavy fuels and fuels containing ignition improvers. Additionally, the influence of injection parameters was evaluated, including injection quantity, pressure level, and nozzle design.

Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector

“…In these figures it is possible to appreciate the effect that the test conditions have on these parameters and on the related time-dwell. While the effect of oxygen concentration and ambient temperature can be chemically explained (typically higher oxygen concentration and ambient temperature accelerate oxidation reactions as expected theoretically [32] and observed experimentally by other authors [33], [34]) the effect of ambient density and injection pressure is related to fuel-air mixing dynamics. At higher ambient density the spray spreading angle increases significantly [35]: in this condition the volume of air entrained in the spray is higher (and denser), causing therefore a faster heating of the fuel mixture.…”

Effects of nozzle geometry on direct injection diesel engine combustion process

“…In a similar study, Pischinger [29] included the effect of injection pressure, which has a lot to do with mixing and vaporizing and, consequently, on ignition delay. For this reason, he proposed the following expression:…”

Fuel temperature influence on diesel sprays in inert and reacting conditions

“…Fuel temperature influence on diesel sprays in inert and reacting conditions. Applied Thermal Engineering, 35,[185][186][187][188][189][190][191][192][193][194][195] 2 behavior of the spray a single-hole axial nozzle has been used; the advantage of this kind of nozzle consists in injecting toward the chamber, eliminating both, the effects and the uncertainties related to the temperature boundary layer close to the walls and the spray-spray interaction. The nozzle internal geometry has been characterized by means of the silicon molding technique [12], the results of this technique provide accurate measurement of the outlet orifice diameter of 0.089 mm with a k-factor of 2.1.…”

“…Fuel temperature influence on diesel sprays in inert and reacting conditions. Applied Thermal Engineering,35,[185][186][187][188][189][190][191][192][193][194][195] Fuel temperature influence on Diesel sprays in inert and reacting conditions Raul Payri (1) Jose Maria Michele Bardi (1) Julien Manin (2) ( …”