The spray characteristics play a crucial role in determining the performance and emissions of compression ignition (CI) engines at the pre-combustion stage. With the advent of many types of alternative fuels and their blends with diesel, it is necessary to investigate the effect of fuel properties and various injection conditions to determine the penetration length, spray cone angle and spray area for a viable fuel with similar or better dispersion characteristics to diesel. Hence, this study reviews and summarizes the spray visualization techniques, along with in depth analysis of macroscopic spray properties of various fuel blends with diesel. It was found that higher injection pressures typically led to higher penetration lengths, better atomization with reduced Sauter mean diameter. Liquid properties such as viscosity, surface tension, and evaporation as well as structural properties play a crucial role in spray formation in fuel blends with various types of alcohols, ethers, biodiesel, aliphatic, aromatic, as well as nanoparticle additives. This review compares these fuel additives and their types to present a comparative study with diesel to determine the ideal conditions with minimal changes to the engine for replacing diesel with a sustainable fuel consisting of better combustion efficiency due to its enhanced spray characteristics.

Fuel spray characteristics influence combustion, which in turn has a direct impact on engine performance and emissions. Recently, there has been an increasing interest in novel castor oil biodiesel. However, few investigations have been performed that combine both numerical and experimental biodiesel spray analyses. Hence, in this paper, we aim to explore the spray behavior of castor and jatropha biodiesel by employing numerical and experimental methods under non-evaporating, varying injection, and ambient conditions. The experimental study was carried out in a control volume vessel (CVV) at high injection and ambient pressures. The fuel atomization was modelled in ANSYS Fluent using a Lagrangian/Eulerian multiphase formulation. The results revealed that the Kelvin–Helmholtz and Rayleigh–Taylor (KHRT) model coupled with the Taylor Analogy Breakup (TAB) model provide a better estimation of the penetration length (PL) and spray cone angle (SCA) compared to the KH and TAB models. On average, Jatropha biodiesel (JB-20) and castor biodiesel (CB-20) showed a 10% to 22% longer PL, 8% to 10.6% narrower spray cone angles, and 3% to 6% less spray area, respectively, compared to diesel. The numerical predictions showed that JB-20 and CB-20 had an around 24.7–48.3% larger Sauter mean diameter (SMD) and a 38.6–73.3% average mean diameter (AMD).

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