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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]

Continuous growing population and a rise in living standards are creating widespread use of vehicles. Motor vehicle emissions contribute significantly to air pollution and other adverse environmental and health effects. The primary contaminants from internal combustion (IC) engines are NOx, CO, CO2, unburnt hydrocarbons (HC), and PM. Their control strategies were considered seriously throughout the discussion. This analysis summarises emissions from both compression ignition (CI) and spark ignition (SI) engines with government-setting emission regulatory standards. This article also gives detailed insight into pollution monitoring methods and their control policy for both CI and SI engines. Emissions from SI engines are more harmful to human health, with more CO and HC emissions in comparison with CI engines. CO emissions are insignificant in CI engines due to lean-burn nature. High temperatures and significant oxygen supply in the combustion chamber make CI engines prone to NOx emissions. This analysis will help researchers to obtain comprehensive emission and their reduction methodologies information for IC engines. [ABSTRACT FROM AUTHOR]

Aligning to water-in-diesel emulsion technology, a newer work has been proposed in this study by introducing gomutra-in-diesel emulsion (GMD emulsion) fuel for application in CI engine. Experimental investigations have been performed in this study for ignition delay and combustion duration to understand the underlying mechanisms of combustion with this fuel. The complete work has been performed over a variable compression ratio (VCR) stationary diesel engine. Emulsions of different gomutra-in-diesel (5%, 10%, 15% and 20%) concentrations were taken for the study. The ignition delay was found to be 24°, 27°, 29°, 32°, and 34° crank angle (CA) with diesel, 5%, 10%, 15%, and 20% water-in-diesel emulsions respectively. The effect of injection timing on the engine performance was also analysed. It was observed that the combustion duration got decreased by a maximum of 12 degrees CA with 20% GMD emulsion. It is estimated that after the optimisation of other engine parameters like injection pressure and compression ratio, the performance of the engine could further be improved. [ABSTRACT FROM AUTHOR]

Latest research on fuels focused on exploring better alternatives for compression ignition engines. A large number of studies reported that the properties of biodiesel are comparable with traditional diesel fuel, which makes it a suitable alternative source of energy. Among various available feedstocks, waste cooking oil is considered as the most viable source for biodiesel production. Apart from being economical, it also reduces waste disposal issues. High free fatty acids and water content in waste cooking oil cause the production of biodiesel difficult. In order to overcome this difficulty, two-step transesterification method is preferred for commercial-scale biodiesel production. Several factors like catalyst concentration, alcohol to oil molar ratio, reaction temperature, and time of reaction affect the yield of biodiesel. This article provides a comprehensive review of biodiesel production from waste cooking oil and its use in compression ignition engines. In this review, fatty acid composition, pre-treatment process, catalytic and non-catalytic approaches of biodiesel production with their advantages and limitations are included. The effect of transesterification reaction parameters on biodiesel yield is also covered. The high viscosity of biodiesel than diesel fuel causes an increase in brake specific fuel consumption and a decrease in brake thermal efficiency of engines. Significant reduction in CO, HC, PM, and smoke emissions are identified; however, NO X and CO 2 emissions found increased due to the oxygenating nature of biodiesel. Overall, it could be concluded that biodiesel produced from waste cooking oil serves as a cleaner and economical alternative source of fuel for compression ignition engines. [Display omitted] • Approximately 30% of per capita edible oil consumption is generated as waste. • Two-step transesterification is the most efficient method for biodiesel production. • Yield of biodiesel is most influenced by the type of catalyst and its concentration. • Brake specific fuel consumption increases due to poor atomization of biodiesel. • CO, HC, PM, and smoke emissions from engine exhaust are reduced significantly. [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]