City Research Online

Abstract

In-nozzle flow dominates primary break-up characteristics and therefore the combustion efficiency. However, predictive methods of the internal nozzle flow and its link with the spray characteristics have traditionally used constant fuel properties, which may lead to large inaccuracies. Surprisingly enough, neither the effects of using realistic surrogates have been closely examined. In this work, the fuel property variation as function of pressure and temperature of three diesel surrogates are modelled using the PC-SAFT state-of-the-art EoS; these include n-dodecane and two mixtures comprising four and eight components, named V0 and V1 respectively, based on a grade no. 2 diesel emissions-certification fuel. Then, the surrogates used in simulations for a common rail 5-hole tip injector. The needle is assumed to be still at a lift of 105µm, similar to that used for pilot injections. The injector operating pressure is 180MPa and the collector back pressure is 5MPa. Heat effects are omitted and no turbulence model is used. The bulk fluid is considered to be a single phase whose density varies according to a barotropic-like scheme, following an isentropic line. Results show that the mixture surrogates V0 and V1 have a greater vapour pressure than that of n-dodecane, although they are significantly heavier both in density and viscosity. Predicted cavitation clouds occupied a ∼14% larger volume for V1 than that for n-dodecane. Slight differences were observed on mass flux, where V1 gave an increase of ∼7% with respect to n-dodecane. Interestingly, the amount of vaporised components which appear simultaneously in the two mixtures were not the same, which may show that there exists an interaction between the components during the vaporisation process. Despite its exploratory nature, this study offers some insight for the first time into the use of complex EoS and surrogate mixtures, which may be worth to capture the particular properties of diesel fuel during high pressure injections.

Publication Type:	Conference or Workshop Item (Paper)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Engineering

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