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Injection timing variations have a significant effect on the performance and pollutant formation in diesel engines. Numerical study was conducted to investigate the impact of injection timing on engine performance and pollutants in a six-cylinder turbocharged diesel engine. Diesel fuel with different amounts (5%, 15%, and 25% by volume) of n-butanol was used. Simulations were performed at four distinct injection timings (5°, 10°, 20°, 25°CA bTDC) and two distinct loads of brake mean effective pressure (BMEP = 4.5 bar and 10.5 bar) at constant engine speed (1800 rpm) using the GT-Power computational simulation package. The primary objective of this research is to determine the optimum injection timing and optimum blending ratio for improved efficiencies and reduced emissions. Notable improvements in engine performance and pollutant trends were observed for butanol-diesel blends. The addition of butanol to diesel fuel has greatly diminished NOX and CO pollutants but it elevated HC and CO2 emissions. Retarded injection timing decreased NOX and CO2 pollutants while HC and CO2 emissions increased. The results also indicated that early injection timings (20°CA bTDC and 25°CA bTDC) lowered both CO2 and unburned hydrocarbon emissions. Moreover, advanced injection timing slightly improved brake thermal efficiency (BTE) for all engine loads. It is concluded that retarded injection timing, i.e., 10°CA bTDC demonstrated optimum results in terms of performance, combustion and emissions and among the fuels 15B showed good outcome with regard to BTE, higher heat release rate, and lower pollution of HC, CO, and NOx.

In recent years, due to stringent emission regulations vehicle manufacturers have been compelled to cut down noxious pollutants released from diesel engines. Different alternative solutions have been recommended to achieve this challenging task. One of these alternative solutions is the utilization of biogas in addition to the use of liquid diesel. In this regard, the current study investigates the combustion characteristics and exhaust emissions of a turbocharged, direct injection, diesel engine operating at constant speed (1800 rpm) and under dual fuel mode with diesel as the pilot fuel and biogas (generated from pig manure and corn straw) and methane enriched biogas. Simulations were carried out at four various engine loads corresponding to brake mean effective pressure (BMEP) of 0.425, 0.85, 1.275, and 1.7 MPa using GT-Power package. The BTE values of biogas-diesel were higher as compared to diesel fuel. The CO2 ratio of biogas did not impact BTE considerably. The highest BTE value of 38.22% was recorded for BG45. However, the Brake specific fuel consumption (BSFC) values for the biogas-diesel fuels were higher than that of diesel fuel operations. With respect to emissions, compared to diesel fuel operation, the hydrocarbon (HC) and CO2 of the biogas-diesel were higher, but NOx and CO pollutants were much lower. The utilization of biogas with diesel by all accounts is attractive to cut down discharges and improve performance of the engine. The engine performance did not deteriorate with up to 45% CO2 proportion in biogas.

The demand for higher output efficiencies, greater specific power output, increased reliability, and ever reduced emissions has been rising. One promising alternative is the use of a gaseous fuel as partial supplement to liquid fuel. In this study, the effects of diesel-natural gas substitution ratios on the engine performance parameters like brake specific fuel consumption (BSFC), and gaseous emissions of nitrogen oxides (NOX), hydrocarbons (HC), carbon monoxide (CO) and carbon dioxide (CO2) were investigated for natural gas-diesel fuel operation and then compared with the original diesel operation. The engine was modeled with GT-Power computational simulation tool. The diesel fuel was injected into the cylinder while natural gas was injected in to air -intake pipe then compressed together with air. The simulation was carried out at constant engine speed of 1800 rpm for four different natural gas fractions (15%, 25%, and 50% and 75%). NOX and CO2 emissions decreased sharply by more than 45% and 50% respectively in dual-fuel mode when compared to only diesel fuel mode. However, an increase was observed in CO and HC emissions in dual fuel mode. The results also indicated that higher BSFC and lower brake thermal efficiency (BTE) in dual fuel mode when compared to those of the corresponding diesel engine.

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