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Significant improvements in exhaust emissions and engine performance in an ordinary DI diesel engine were realized with highly oxygenated fuels. The smoke emissions decreased sharply and linearly with increases in oxygen content and entirely disappeared at an oxygen content of 38 wt-% even at stoichiometric conditions. The NOx, THC, and CO were almost all removed with a three-way catalyst under stoichiometric diesel combustion at both the higher and lower BMEP with the combination of EGR and a three-way catalyst. The engine output for the highly oxygenated fuels was significantly higher than that with the conventional diesel fuel due to the higher air utilization.

The fundamental parameters related to engine combustion and performances, such as, heating value, theoretical air-fuel ratio, adiabatic flame temperature, carbon dioxide (CO2), and nitric oxide (NO) emissions, specific heat and engine thermal efficiency were investigated with computations for a wide range of oxygenated fuels. The computed results showed that almost all of the above combustion-related parameters are closely related to oxygen content in the fuels regardless of the kinds or chemical structures of oxygenated fuels. An interesting finding was that with the increase in oxygen content in the fuels NO emission decreased linearly, and the engine thermal efficiency was almost unchanged below oxygen content of 30 wt-% but gradually decreased above 30 wt-%.

The world is looking for an alternate fuel to replace the existing petroleum based products due to the depletion of natural resources and it has been projected for future unavailability and fluctuation of oil price in an international market. The EU directive targets 20% of all fuel should be from bio-fuels by 2020. There is a need to improve performance and emission levels in Compression Ignition (CI) or Spark Ignition (SI) engines to comply with stricter automotive norms and regulations due to the global warming issues. This research work is influenced by these factors and is expected to motivate the governing bodies to implement directives with higher bio fuel blends. In this context, a four stroke, single cylinder naturally aspirated (NA) direct injection (DI) diesel engine with 8 BHP @ 1500 rpm coupled with water cooled eddy current dynamometer was used for the experiments.

In this study, experiments were performed on a 4-stroke, 6-cylinder turbocharged, direct injection (DI) diesel engine using two oxygenated fuels blended with European auto diesel fuel (DF) to investigate the engine performance and exhaust emissions with special interest in fine particles. In the investigation, 20 vol% jatropha biodiesel was added to the DF; while 6.31 vol% diethylene glycol dimethyl ether (DGM) was added to the DF to maintain same oxygen percentage (2.26 wt%) in the blended fuels. The fuel is designated as DDGM for the DF-DGM blend and DB20 for the DF-biodiesel blend. The fine particle number was determined with a scanning mobility particle sizer (SMPS). Carbon monoxide (CO), total unburnt hydrocarbon (THC), smoke, total particulate matter (TPM) and oxides of nitrogen (NOx) were also measured.

Changes in exhaust gas emissions during starting in a DI diesel engine were investigated. The THC after starting increased until around the 50th cycle when the fuel deposited on the combustion chamber showed the maximum, and THC then decreased to reach a steady value after about 1000 cycles when the piston wall temperature became constant. The NOx showed an initial higher peak just after starting, and increased to a steady value after about 1000 cycles. Exhaust odor had a strong correlation with THC, and at the early stage odor was stronger than would be expected from the THC concentration. The THC increased with increased fuel injection amounts, decreased cranking speeds, and fuels with higher viscosity, higher 90% distillation temperature, and lower ignitability.

In this report diesel combustion and exhaust emission with neat diesel fuel and diesel-biodiesel blends is investigated. In the investigation, first, the making of biodiesel is done by esterification and second, experiment is conducted with neat diesel fuel and diesel-biodiesel blends in a four stroke naturally aspirated (NA) direct injection (DI) diesel engine. The volumetric blending ratios of biodiesel with conventional diesel fuel are set at 0, 5, 10, 15, and 20. Compared with neat diesel fuel, diesel-biodiesel blends show lower carbon monoxide (CO), and smoke emissions due to the improved properties after esterification and the presence of oxygen in the biodiesel. With diesel-biodiesel blends nitrogen oxide (NOx) is reduced at retarded injection timing but increased at advanced injection timing. Engine noise is reduced significantly with all diesel-biodiesel blends.