Analytical Modelling, CFD Simulation, and Experimental Validation of n-butanol-Diesel/Biodiesel Fuel Blends in a Microfluidic System

Abstract

Dilution of diesel/biodiesel fuel with n-butanol in engines has a significant role in reducing the pollutants and improving the performance of compression ignition engines. This can be achieved using microfluidic networks, which allow an optimum dilution ratio to be precisely defined in an automated and controlled manner. This paper presents a novel, comprehensive study for such a process. The dilution profile of n-butanol-diesel/biodiesel fuel blends in a microfluidic hierarchical network system was predicted at different conditions. An analytical model was provided for the prediction of the variables’ distribution within the network. The model allowed for a wide range of n-butanol-diesel/biodiesel blends dilution to be investigated and validated experimentally and with CFD simulations. The mathematical model proved successful, returning precise results. Excellent agreement was found with the real data for the distributions of the variables within the network including the volume fractions, viscosity, and density. It showed that mixing 10 vol% with 90 vol% of n-butanol in diesel fuel resulted in maximum deviations of: 0.037% and 0.061% in the volume fractions of outlet streams; 0.19% and 0.08% in the density, and 2.32% and 14.13% in the viscosity, from the experimental and CFD simulation results, respectively. In addition, finer dilution of 30 vol % n-butanol in diesel fuel with 10 vol% n-butanol in diesel fuel showed maximum deviations of 0.006% and 0.08% in the volume fraction, 0.018% and 0.008% in the density, and 2.86% and 14.27% in the viscosity distribution, from the experimental and CFD simulations, respectively. The network’s performance with n-butanol-biodiesel blends compared with n-butanol-diesel blends was also presented. This study is of great importance for optimizing alcohol ratios in diesel/biodiesel for the best engine performance and minimum greenhouse gas emissions. It also allows for predicting the properties of un-experimented ratios of blends. Possible applications of this study include areas where precise control of the additives to diesel/biodiesel has a significant effect such as improving the lubricity in an engine, monitoring the fuel droplets, and/or precisely specifying the fuel spray characteristics.