A Multicomponent Blend as a Diesel Fuel Surrogate for Compression Ignition Engine Applications

Abstract

A mixture of n-dodecane and m-xylene is investigated as a diesel fuel surrogate for compression ignition (CI) engine applications. Compared to neat n-dodecane, this binary mixture is more representative of diesel fuel because it contains an alkyl-benzene which represents an important chemical class present in diesel fuels. A detailed multicomponent mechanism for n-dodecane and m-xylene was developed by combining a previously developed n-dodecane mechanism with a recently developed mechanism for xylenes. The xylene mechanism is shown to reproduce experimental ignition data from a rapid compression machine (RCM) and shock tube (ST), speciation data from the jet stirred reactor and flame speed data. This combined mechanism was validated by comparing predictions from the model with experimental data for ignition in STs and for reactivity in a flow reactor. The combined mechanism, consisting of 2885 species and 11,754 reactions, was reduced to a skeletal mechanism consisting 163 species and 887 reactions for 3D diesel engine simulations. The mechanism reduction was performed using directed relation graph (DRG) with expert knowledge (DRG-X) and DRG-aided sensitivity analysis (DRGASA) at a fixed fuel composition of 77% of n-dodecane and 23% m-xylene by volume. The sample space for the reduction covered pressure of 1–80 bar, equivalence ratio of 0.5–2.0, and initial temperature of 700–1600 K for ignition. The skeletal mechanism was compared with the detailed mechanism for ignition and flow reactor predictions. Finally, the skeletal mechanism was validated against a spray flame dataset under diesel engine conditions documented on the engine combustion network (ECN) website. These multidimensional simulations were performed using a representative interactive flame (RIF) turbulent combustion model. Encouraging results were obtained compared to the experiments with regard to the predictions of ignition delay and lift-off length at different ambient temperatures.

Effects of ambient pressure on ignition and flame characteristics in diesel spray combustion

“…[10]. [19,25], a recently updated n-heptane model (the Zhang1268 mechanism) [26], and an integrated model of n-dodecane and myxelene (the Pei163 mechanism) [27]. [30], the most reactive mixture (Zmr) is characterized as the mixture which has the shortest IDT, and the associated IDT can serve as a reference for the comparison against the results from inhomogeneous and turbulent mixtures [30].…”

Large eddy simulation of a reacting spray flame with multiple realizations under compression ignition engine conditions

“…The spray experiments presented in this work were performed in a constant volume pre-burn chamber, which has provided a platform for model development and validation at engine relevant conditions [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. A detailed description of the experimental setup and measurement procedures can be found in the literature [28][29][30].…”

The effect of nozzle geometry over ignition delay and flame lift-off of reacting direct-injection sprays for three different fuels

“…In particular, the Surrogate fuel is of interest, since it is conceptualized to better mimic the soot-related behavior of real diesel fuel, as its PAH content should increase soot formation in comparison to pure n-alkanes. However, it is also possible that the SSI delay induced by the a-methylnaphthalene content is large enough so to delay ignition to a point where the local equivalence ratio is very low, which would render a less-sooting flame: a similar situation what was found for the secondary fuel of the ECN, which is a mixture of n-dodecane and m-xylene [36,56].…”