3D CFD Combustion Evaluation of Hydrotreated Vegetable Oil (HVO) as a Potential Alternate Fuel for the Future CI Engines

Transportation industry is facing a growing challenge to reduce its carbon footprint and utilize the carbon neutral, more environmentally sustainable fuels to comply with the goal of carbon neutrality. Implementation of carbon free fuels such as Hydrogen, Ammonia and low carbon fuels such as Methanol, Ethanol can significantly reduce the greenhouse gas emissions, but these fuels are suitable for SI engine architecture due to their high-octane ratings. Hydrotreated Vegetable Oil (HVO) is one of the few fuel solutions available today with a high Cetane rating (70-80), that can be used as a drop-in fuel in the existing CI engines, with minimal modifications. The main constituent of HVO is pure alkane and it can be produced from feedstocks such as vegetable oils, animal fats, various wastes and by-products. A closed cycle 3-D CFD combustion simulation using a detailed chemistry-based solver has been conducted with the HVO, on a three cylinder, naturally aspirated water-cooled CI engine at its full load, rated rpm. Chemical kinetics file with 92 species and 1240 reactions has been used as a surrogate for the HVO to conduct the combustion simulation. The peak firing pressure has been observed to be lower by 3% and SoC is advanced by 2^o CA for HVO as compared to the baseline diesel. HVO combustion manifests the same thermal efficiency with respect to its diesel counterpart. Soot emission has been 36% lower for HVO due to the absence of unsaturated hydrocarbons and the NO_x emission is lowered by 32% for HVO, as a consequence of a lowered in-cylinder temperature. Simultaneously, a 13% reduction in CO, 77% reduction in UHC and 74% reduction in VOC have been observed for HVO as compared to diesel. A meticulous monitoring of unregulated emissions proves that the HVO exhaust is devoid of their presence. The 3D CFD combustion exploration unveils that the HVO indeed holds the potential to be a promising drop-in alternate fuel for the next generation CI engines.