Development of Thermophysical and Transport Properties for the CFD Simulations of In-Cylinder Biodiesel Spray Combustion

Abstract

This paper reports the development, validation, and application of the thermophysical and transport properties of coconut, palm, and soy methyl esters for fuel spray and combustion modeling under light-duty diesel engine conditions. The developed fuel library is implemented in an open-source CFD code. The fuel properties are validated for both constant volume combustion chamber and compression ignition (CI) engine operation at a wide range of conditions. Sensitivity analysis on the effects of individual fuel properties is also investigated under both conditions. The properties of interest for the study are density, vapor pressure, heat of vaporization, liquid heat capacity, vapor heat capacity, second-virial coefficient, liquid dynamic viscosity, vapor dynamic viscosity, liquid thermal conductivity, vapor thermal conductivity, surface tension, and vapor diffusivity. From these twelve physical and transport properties, only five have significant effects on fuel spray structure, combustion, and emission characteristics. These are vapor pressure, vapor diffusivity, surface tension, liquid density, and liquid dynamic viscosity. However, only vapor pressure and surface tension have the strongest influence on the mixture preparation process.

Numerical Studies of In-Cylinder Combustion and Soot Emission Characteristics of Biodiesel Fuels from Different Feedstock

“…The evaporation rate of SME shown in Figure 6 is slightly higher than that of PME at the beginning 3 CAD for all levels of engine power, which is then followed by slight fluctuations at similar magnitudes between the two fuels. At low temperatures, SME has similar vapour pressure as compared to PME, but lower surface tension leading to a higher initial evaporation rate [20]. SME and PME demonstrate different combustion characteristics at different engine powers although their IDs are similar.…”

“…The initial evaporation rates are of concern here as they directly affect the IDs. It is observed that within 4 CAD from the SOI, diesel fuel demonstrates the highest evaporation rate which can be attributed to its physical properties of diesel [20]. The surface tension, vapour pressure and density of diesel are at values favourable to high evaporation rate.…”

“…The key properties include density, vapour pressure, heat of vaporisation, liquid heat capacity, liquid dynamic viscosity, liquid thermal conductivity, surface tension and binary diffusivity. The fuel properties of SME, PME and CME utilised in this study have been developed and validated in a constant volume combustion chamber with operating conditions of a compression ignition (CI) engine [20].…”

Review of Experimental and Computational Studies on Spray, Combustion, Performance, and Emission Characteristics of Biodiesel Fueled Engines

“…However, as the SoI timing approached closer to TDC, the effect of fuel properties on mixing processes significantly reduced. Ismail et al [229] performed fuel spray and combustion modeling of coconut methyl ester (CME), palm methyl ester (PME), and Soyabean methyl ester (SME) using the measured fuel properties. Since each methyl ester is from a different source, the composition of each ester was analyzed and the properties were measured for an individual biodiesel.…”

“…Hexadecanoic acid, methyl ester 17 Octadecanoic acid, methyl ester 9 9-Octadecenoic acid, methyl ester 30 9, 12-Octadecadienoic acid, methyl ester 44 Fig. 23 Experimental and numerical axial penetration length for (a) PME vapor and liquid and (b) PME, CME, SME, and mineral diesel in liquid phase [229] Fig. 25, the updated constants could capture biodiesel spray characteristics based on reference results.…”