Homogeneous Charge Compression Ignition: Formulation Effect of a Diesel Fuel on the Initiation and the Combustion - Potential of Olefin Impact in a Diesel Base Fuel

Abstract

Résumé -Combustion en mode HCCI : impact de la formulation d'un carburant Diesel sur l'initiation et la combustion -Potentiel de l'ajout d'oléfine dans une base gazole -L'objectif de ce travail est de proposer une amélioration du contrôle et de l'initiation de la combustion en mode HCCI via la formulation du carburant. L'article présente l'impact de l'addition d'oléfines (et en particulier l'addition de 1-octène et d'octa-1,7-diène) dans une base gazole. Les tests sont effectués à l'aide d'un réacteur auto-agité et d'un banc moteur. L'indice de cétane d'un carburant Diesel n'est pas réellement adapté pour un contrôle parfait de la combustion en mode HCCI. Dans des conditions de combustion en mode HCCI, l'autoinflammation de la base gazole se produit trop tôt dans le cycle moteur. Cette étude montre, sur réacteur auto-agité, que le 1-octène réduit l'avancement réactionnel de la flamme froide du n-octane. Sur banc moteur, à 1500 tr/min, l'ajout de 1-octène et d'octa-1,7-diène diminue le délai physique et augmente le délai chimique d'auto-inflammation de la base gazole. Ces résultats s'expliquent par la chimie des oléfines : les doubles liaisons des oléfines impliquent des réactions compétitives (avec des radicaux) à celles donnant lieu à la flamme froide. De plus, les espèces intermédiaires sont stabilisées par mésomérie. Au niveau des polluants, les oléfines diminuent les émissions d'HC de la base gazole. Ajouter des oléfines légères à une base gazole est une voie d'amélioration envisageable pour la combustion en mode HCCI. Abstract -Homogeneous Charge Compression Ignition: Formulation Effect of a Diesel Fuel on the Initiation and the Combustion -Potential of Olefin Impact in a DieselBase Fuel -In this work, attention is paid on initiation and HCCI combustion control through fuel formulation. This article shows the effect of olefin addition (and in particular 1-octene and octa-1,7-diene addition) in a Diesel base fuel. Tests are made with a jet-stirred reactor and an engine bench. The current Diesel fuel cetane numbers are not really adapted for a perfect control of HCCI combustion. In HCCI conditions, the autoignition of a Diesel fuel occurs too early in the cycle. This study shows that, with the jet-stirred reactor, 1-octene addition allows decreasing the advancement of the cool flame reaction of n-octane. Engine bench experiments show that, at 1500 rpm, 1-octene and octa-1,7-diene addition decrease the physical delay and increase the chemical auto-ignition delay of the Diesel base fuel. These results can be explained by olefin chemistry: olefin double bonds imply reactions (with radicals) that are in competition with the cool flame reactions. There is also the fact that the intermediate species are stabilised by mesomery. About pollutants, olefin addition decreases HC emissions of the Diesel base fuel. Adding light olefins in a Diesel base fuel could improving the HCCI combustion.

Computational studies on the reactions of 3‐butenyl and 3‐butenylperoxy radicals

“…However, the knowledge on the kinetics of the oxidation of alkenes is limited compared to that for alkanes. Several studies have been reported for the development of a detailed kinetic mechanism for alkene combustion [1][2][3][4] based mostly on analogy to the mechanism of the combustion of alkanes, by taking into account the stability of allyl and substituted allyl radicals which seem to be the most characteristic difference from the alkane oxidation. An extensive quantum chemical investigation has been reported for the reaction of allyl (C 3 H 5 ) radicals with O 2 [5], which is a prototypical oxidation step of alkenes.…”

Experimental Combustion Analysis of a Small Size Diesel Engine Fueled With Tire Derived Fuel/Diesel Fuel Blends

“…Moreover, the olefin content increase and the cetane number decreases as the proportion of TDF in the fuel blend increases. Increased olefin content reduces the physical ignition delay and increases the chemical ignition delay due to olefin chemistry explained in detail in Ref [23]. The reduced cetane number of TDF blends also prolongs the chemical ignition delay and the total effect of the above-mentioned factors leads to the TDF blend having a longer ignition delay.…”

“…The lower the distillation range and flash point, the higher the fuel volatility. In addition, the higher olefin content of fuel decreases the temperature of the distillation range, makes the fuel more evaporative, leads to greater heat absorption from the combustion chamber, and results in a delay in the combustion process [23]. The hydrocarbon composition of fuels such as aromatic and olefin content affects the cetane number.…”

“…However, the TDF fuel blend causes a higher temperature drop and greater heat absorption in the combustion chamber due to its lower distillation range, better volatility and higher density. This phenomenon overcomes the above-mentioned effect and may lead to a larger physical ignition delay [20,22,23,30]. Increased ignition delay owing to a higher density of TDF blends can be accounted for by the drop in temperature during the delay period due to increasing evaporation as more fuel is injected [31].…”

Implementation of PC-SAFT and SAFT+Cubic for modeling thermodynamic properties of eight 1-alkenes and their mixtures

“…It is widely agreed that presence of olefins affects the quality of Diesel fuels as well [4,5], due to their relatively low cetane numbers [6] and smoke points [7]. At the same time, Alseda et al [8] have demonstrated the advantage of the light olefins addition in Diesel fuels. Furthermore, C 10 -C 18 olefins such as 1-dodecene or 1-tetradecene meet viscosity and pour points specifications for formulation into oil based muds and exhibit good biodegradability while being non-toxic to marine organisms and less irritating to skin than many alternatives.…”