SOME STUDIES ON ENHANCEMENT OF DIESEL ENGINE CHARACTERISTICS AND FUEL PROPERTIES BY USING FUEL ADDITIVES

Abstract

Diesel engines continue to hold a dominant position in the global energy and transportation divisions due to their high efficiency, robustness, and cost-effectiveness. According to the International Energy Agency (IEA), diesel engines account for over 40% of the energy used in global transportation and are pivotal in freight logistics, power generation, and agricultural mechanization. In India, diesel engines power approximately 70% of freight vehicles and over 60% of agricultural machinery, making them indispensable to economic activity. However, their extensive use poses a significant environmental challenge. Diesel combustion emits high levels of nitrogen oxides, particulate matter (PM), carbon monoxide (CO), and unburned hydrocarbons (HC), contributing to both regional pollution and worldwide environment concerns. To counteract these environmental impacts, governments have enforced stringent emission regulations. In India, the implementation of Bharat Stage VI (BS VI) norms, aligned with Euro 6 standards, has mandated a substantial reduction in vehicular emissions. A cornerstone of this transition is the shift to Ultra-Low Sulfur Diesel (ULSD), which contains sulfur content below 10 ppm. While this has effectively reduced sulfur-related emissions, it has simultaneously led to deteriorated fuel lubricity, lower energy density, and an increase in engine component wear, particularly in fuel injection systems. Though renewable energy solutions are being promoted as long-term alternatives, their universal implementation is constrained by intermittency, high upfront infrastructure costs, and limited feasibility in remote, off-grid locations. In India alone, millions of agricultural diesel engines operate in regions lacking consistent electricity, making full-scale replacement with renewables impractical in the near term. Some Studies on Enhancement of Diesel Engine Characteristics and Fuel Properties By using Fuel Additives Page | vii To diversify energy sources, the National Biofuel Policy (2018) encourages biodiesel production from waste cooking oil and other non-edible feedstocks. However, challenges persist in feedstock collection, supply chain logistics, and fuel quality assurance. These limitations hinder the large-scale implementation of biodiesel blending, despite its potential to reduce fossil fuel dependence and carbon emissions. This research addresses the dual challenge of diesel fuel degradation post-desulfurization and limited biofuel integration by developing a novel multi-purpose additive. The additive is synthesized by combining a Lubricity Enhancer, Cetane Booster, Antioxidant, Combustion Catalyst, and Surfactant, mixed in specific ratios into a refined base oil to optimize physical and chemical compatibility with diesel fuels. A novel multipurpose solution was blended with ULSD and diesel-biodiesel blends in three volumetric concentrations: 0.5, 1.0, and 2.0 ml per 100 ml of fuel. The test samples for pure diesel were designated as D100MPS 0.5, D100MPS 1.0, and D100MPS 2.0, while blends containing 95% ULSD and 5% waste cooking oil-based biodiesel were labelled as D95WCB5MPS 0.5, D95WCB5MPS 1.0, and D95WCB5MPS 2.0. In accordance with the National Biofuel Policy, WCO was collected and converted into biodiesel via base-catalyzed transesterification. The resulting fuel was characterized using Gas Chromatography- Mass Spectrometry (GC-MS) to analyze Fatty Acid Methyl Ester (FAME) profiles, focusing on the percentage of unsaturated fatty acids that influence combustion behavior and oxidation stability. Physicochemical properties of all fuel samples were assessed using ASTM standard methods. All tested blends conformed to ASTM standards and showed compatibility with baseline diesel. Tribological performance was evaluated using a High-Frequency Reciprocating Rig (HFRR) to determine wear scar diameter and coefficient of friction. The aromatic-rich composition of MPS Some Studies on Enhancement of Diesel Engine Characteristics and Fuel Properties By using Fuel Additives Page | viii facilitated tribo-film formation, leading to MWSD reductions of 25.79%, 46.08%, and 56.23% for D100MPS 0.5, 1.0, and 2.0, respectively. Notably, D100MPS 2.0 also reduced the coefficient of friction by 55.08% compared to untreated BS-VI diesel. Results showed that D100MPS 2.0 significantly reduced both parameters, confirming enhanced lubricity due to the additive. Engine trials were conducted on a Kirloskar make single-cylinder, four-stroke, direct injection compression ignition engine to evaluate engine characteristics. Findings indicated that the addition of additive solution improved brake thermal efficiency and reduced brake-specific energy consumption in both pure diesel and biodiesel blends on an unmodified engine. The incorporation of MPS, enriched with antioxidants and cetane improvers, led to NOx emission reductions from 1196 ppm to 1154 ppm for neat diesel and from 1298 ppm to 1185 ppm for the D95WCB5 blend at peak BMEP. All MPS- treated fuels showed consistent decreases in HC, CO, and smoke emissions. These outcomes highlight the additive’s effectiveness in reducing overall exhaust emissions. However, increase in exhaust gas temperature (EGT) were observed, although all values remained within acceptable emission limits. In summary, this research presents a comprehensive, scalable, and cost-effective strategy to overcome the tribological, performance, and emission challenges associated with ULSD and biodiesel-diesel blends. The Multipurpose Additive Solution (MPS) not only restores the lubricity lost during desulfurization but also enhances combustion characteristics and reduces harmful emissions without necessitating changes to existing engine hardware. The findings hold relevance for countries like India, where diesel engines remain critical to agriculture and transportation and where the transition to full electrification is a long-term endeavour. By bridging current fuel use with future sustainability targets, this research supports the advancement of cleaner and efficient diesel engine technologies aligned with national biofuel strategies and global energy commitments.