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The combustion and emission characteristics of a diesel engine running on butanol-diesel blends were investigated in this study. The blending ratio of n-butanol to diesel was varied from 0 to 40 vol% using an increment of 10 vol%, and each blend was tested on a 2.7 L V6 common rail direction injection diesel engine equipped with an EGR system. The test was carried out under two engine loads at a constant engine speed, using various combinations of EGR ratios and injection timings. Test results indicate that n-butanol addition to engine fuel is able to substantially decrease soot emission from raw exhaust gas, while the change in NOx emissions varies depending on the n-butanol content and engine operating conditions. Increasing EGR ratio and retarding injection timing are effective approaches to reduce NOx emissions from combustion of n-butanol-diesel blends.

Due to the increasing consumption of fossil fuels, alternative fuels in internal combustion engines have attracted a lot of attention in recent years. Ethanol is the most common alternative fuel used in spark ignition (SI) engines due to its advantages of biodegradability, positively impacting emissions reduction as well as octane number improvement. Meanwhile, acetone is well-known as one of the industrial waste solvents for synthetic fibers and most plastic materials. In comparison to ethanol, acetone has a number of more desirable properties for being a viable alternative fuel such as its higher energy density, heating value and volatility.

In order to comply with the stringent emission regulations, many researchers have been focusing on diesel-compressed natural gas (CNG) dual fuel operation in compression ignition (CI) engines. The diesel-CNG dual fuel operation mode has the potential to reduce both the soot and NOx emissions; however, the thermal efficiency is generally lower than that of the pure diesel operation, especially under the low and medium load conditions. The current experimental work investigates the potential of using diesel-1-butanol blends as the pilot fuel to improve the engine performance and emissions. Fuel blends of B0 (pure diesel), B10 (90% diesel and 10% 1-butanol by volume) and B20 (80% diesel and 20% 1-butanol) with 70% CNG substitution were compared based on an equivalent input energy at an engine speed of 1200 RPM. The results indicated that the diesel-1-butanol pilot fuel can lead to a more homogeneous mixture due to the longer ignition delay.

Butanol, which is a renewable biofuel, has been regarded as a promising alternative fuel for internal combustion engines. When blended with diesel and applied to pilot ignited natural gas engines, butanol has the capability to achieve lower emissions without sacrifice on thermal efficiency. However, high blend ratio of butanol is limited by its longer ignition delay caused by the higher latent heat and higher octane number, which restricts the improvement of emission characteristics. In this paper, the potential of increasing butanol blend ratio by adding hot exhaust gas recirculation (EGR) is investigated. 3D CFD model based on a detailed kinetic mechanism was built and validated by experimental results of natural gas engine ignited by diesel/butanol blends. The effects of hot EGR is then revealed by the simulation results of the combustion process, heat release traces and also the emissions under different diesel/butanol blend ratios.