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Out of various strategies to extenuate the diesel engine emissions, use of water-blended diesel fuel in emulsified form is found to be a prominent option. The studies carried out by various researchers give quite inconsistent results for optimum water concentration, surfactant concentration, and HLB value. An effort has been made in this paper to analyze this inconsistency of water concentration and surfactant for engine emissions and performance along with the effect of compression ratio. The work has been carried out on a non-road, constant rpm, VCR (variable compression ratio) diesel engine. Different emulsions of 5%, 10%, 15%, and 20% water-in-diesel with 3% emulsifier concentration were tested on the diesel-optimized engine at CR 21. The results showed that emulsion of 15% water-in-diesel is optimal on the basis of emissions and performance. Further, the selected 15% emulsion is tested with 4% emulsifier concentration. It improved the stability of emulsion and performance of the engine with slight adverse effects on the NOx emissions. Then, emulsion with 4% surfactant and 15% water is tested to determine optimum compression ratio for emulsified fuels. CR 20 is found in optimum. Remarkably 9.28% improvement in BTE is observed reaching up to 23.89% as compared to 21.86% with bare diesel. 25.1% reduction in NOx and more than 50% reduction in smoke is observed. Overall, it is concluded that the water-blended diesel emulsion could serve as a fuel-efficient cleaner combustion technology and needs to be standardized. Abbreviations HLB: Hydrophile–Lipophile Balance; Cv: Calorific Value; W/D: Water in Diesel; PM: Particulate matter; RPM: Rotation per minute; HC: Hydrocarbon; CR: Compression Ratio; EGT: Exhaust Gas Temperature; BTE: Brake Thermal Efficiency; NOx: Oxides of Nitrogen; BSFC: Brake specific fuel consumption [ABSTRACT FROM AUTHOR]

• A novel approach of cow-urine (gomutra) emulsification in diesel is explored. • 15% Cow-urine emulsification in diesel was found optimum. • Significant 13.2% improvement in brake thermal efficiency was observed. • Water and urea content of the GMD emulsion resulted in reduced exhaust emissions. • NO x and smoke emissions got reduced up to 31.8% and 36.9% respectively. Apart from the various emission reduction strategies, a novel concept of cow-urine emulsification in diesel has been explored in this study. In India, cow urine is easily and readily available as gomutra distillate. It constitutes of around 95% water and exhibits the benefits of water emulsification to improve the brake thermal efficiency. Additionally, it consists of urea which works as a reducing agent and significantly cuts-down the NO x emissions. Sodium, magnesium, calcium and potassium present in the cow-urine are also expected to enhance the fuel properties as found in various other researches. Emulsions containing 5%, 10%, 15% and 20% (v/v) cow-urine were tested on a stationary C.I. engine. The 15% emulsion was found to be optimum with a remarkable increase in BTE reaching up to 24.8% as compared to 21.9% with base diesel. In emissions, NO x and smoke got reduced by maximum up to 31.8% and 36.9% respectively. At lower loads, the CO emissions were found to be increased but at higher loads, it was also decreased. No significant variation in HC emissions was observed. Overall, cow-urine emulsified diesel fuel was found to be an energy-efficient and cleaner alternative fuel for stationary C.I. engine application. [ABSTRACT FROM AUTHOR]

This study investigates the characterization of the hydroxy-diesel fueled compression ignition engine under dual fuel (DF) mode on a stationary modified engine. Hydroxy gas (HHO) is supplied along with diesel at three different flow rates of 0.25, 0.50, and 0.75 lpm. A significant reduction in emission parameters was obtained in carbon monoxide, unburnt hydrocarbon and smoke emission as ~58%, ~60%, and ~49%, respectively under the DF mode (at 0.75 lpm HHO and 10 kg load). However, a slight increment in nitrogen oxides (NO X) emission is observed due to the O 2 contents in HHO gas. It increases the reaction temperature and results in increasing the NO X emission. The brake thermal efficiency and brake specific energy consumption also improved and found to be ~6.5% and ~6% at the optimized condition. Combustion analysis shows the rate of pressure rise increased due to quicker combustion and decreased combustion duration. A numerical simulation has been performed to optimize the engine load and HHO flow rate using the Hybrid Entropy-VIKOR technique. In addition, a good agreement has been found between simulation and experimental values for performance and emission parameters. The results can be further improved by optimizing the engine operating parameters, i.e., injection pressure, compression ratio, and injection timing in the near future. Overall it can be concluded the HHO can be considered as a prominent alternative fuel for the CI engine with increased efficiency and lower emissions. Image 1 • Engine performance parameters (BTE and BSEC) improved with the hydroxy energy share. • Significant reduction in HC, CO, and smoke emission was observed with the HHO addition. • ROPR, in-cylinder MGT, and NHRR improved for D+0.75HHO mixture. • The engine operating parameters were optimized using the hybrid Entropy-VIKOR approach. [ABSTRACT FROM AUTHOR]