Diesel engines are one of the most popular reciprocating engines on the market today owing to their great thermal efficiency and dependability in energy conversion. Growing concerns about the depletion of fossil resources, fluctuating prices in the market, and environmental issues have prompted the search for renewable fuels with higher efficiencies compared with conventional fuels. Fuel derived from vegetable oils and animal fats has comparable characteristics to diesel fuel, but is renewable, despite being manufactured from various feedstocks. Nevertheless, the direct use of these fuels is strictly prohibited because it will result in many issues in the engine, affecting engine performance and durability, as well as emissions. To make biofuels as efficient as fossil fuels, it is essential to alter their characteristics. The use of emulsification techniques to obtain emulsified biofuels is one of the many ways to modify the fuel characteristics. Emulsification techniques allow for a decrease in viscosity and an increase in atomisation during injection. To date, emulsification techniques have been studied less thoroughly for use with vegetable oils and animal fats. This article will discuss the preparation and characterisation of emulsified biofuels made from vegetable oils and animal fats. This current paper reviewed research studies carried out on different emulsification techniques for biofuels used in diesel engines.

Generally, the compression ignition (CI) engine that runs with emulsified biofuel (EB) or higher viscosity fuel experiences inferior performance and a higher emission compared to petro diesel engines. The modification is necessary to standard engine level in order to realize its application. This paper proposes a guide vane design (GVD), which needs to be installed in the intake manifold, is incorporated with shallow depth re-entrance combustion chamber (SCC) pistons. This will organize and develop proper in-cylinder airflow to promote better diffusion, evaporation and combustion processes. The model of GVD and SCC piston was designed using SolidWorks 2017; while ANSYS Fluent version 15 was utilized to run a 3D analysis of the cold flow IC engine. In this research, seven designs of GVD with the number of vanes varied from two to eight vanes (V2–V8) are used. The four-vane model (V4) has shown an excellent turbulent flow as well as swirl, tumble and cross tumble ratios in the fuel-injected region compared to other designs. This is indispensable to break up heavier fuel molecules of EB to mix with the air that will eventually improve engine performance.

This paper presents a numerical analysis of the application of emulsified biofuel (EB) to diesel engines. The study performs a numerical study of three different guide vane designs (GVD) that are incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. The GVD variables were used in three GVD models with different vane heights, that is, 0.2, 0.4 and 0.6 times the radius of the intake runner (R) and these were named 0.20R, 0.40R and 0.60R. The SCC piston and GVD model were designed using SolidWorks 2017, while ANSYS Fluent version 15 was used to perform cold flow engine 3D analysis. The results of the numerical study showed that 0.60R is the optimum guide vane height, as the turbulence kinetic energy (TKE), swirl ratio (Rs), tumble ratio (R_T) and cross tumble ratio (R_CT) in the fuel injection region improved from the crank angle before the start of injection (SOI) and start of combustion (SOC). This is essential to break up the heavier-fuel molecules of EB so that they mix with the surrounding air, which eventually improves the engine performance.

Compression ignition (CI) engines that run on high-viscosity fuels (HVF) like emulsified biofuels generally demonstrate poor engine performance. An engine with a consistently low performance, in the long run, will have a negative effect on its lifespan. Poor combustion in engines occurs mainly due to the production of less volatile, less flammable, denser, and heavier molecules of HVF during injection. This paper proposes a guide vane design (GVD) to be installed at the intake manifold, which is incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. This minor modification will be advantageous in improving the evaporation, diffusion, and combustion processes in the engine to further enhance its performance. The CAD models of the GVD and SCC piston were designed using SolidWorks 2018 while the flow run analysis of the cold flow CI engine was conducted using ANSYS Fluent Version 15. In this study, five designs of the GVD with varying lengths of the vanes from 0.6D (L) to 3.0D (L) were numerically evaluated. The GVD design with 0.6D (L) demonstrated improved turbulence kinetic energy (TKE) as well as swirl (R_s), tumble (R_T), and cross tumble (R_CT) ratios in the fuel-injected zone compared to other designs. The suggested improvements in the design would enhance the in-cylinder airflow characteristics and would be able to break up the penetration length of injection to mix in the wider area of the piston-bowl.