Improving fuel combustion in engines and consequently reducing environmentallyunfavorable emissions is of prominent importance in addressing some of the main challenges of the current century, i.e., global warming and climate change. Fuel additives are considered as efficient way for improving fuel properties and to diminish engine emissions. In line with this, the present research was focused on the simultaneous application of water (3, 5, and 7 wt%) and cerium oxide nano particles (90 ppm) as metal-based additive into biodiesel/diesel fuel blend (B5) and their impacts on the performance and emission characteristics of a single cylinder four stroke diesel engine were investigated. The findings revealed that the aqueous nano-emulsion of cerium oxide improved the overall combustion quality. More specifically, the brake specific fuel consumption (bsfc) of B5 containing 3% water and 90 ppm cerium oxide (B5W3m) was measured 5% and 16% lower than those of neat B5 and neat B5 containing 3% water (B5W3), respectively. Moreover, the B5W3m fuel blend increased brake thermal efficiency (bte) by over 23 and 11% compared with B5W3 and B5, respectively. B5W3m also considerably reduced CO, HC, and NOx emissions by 51, 45, and 27% compared with B5W3. To the best of our knowledge, this is the first report exploring the impacts of low-level water containing cerium oxide in B5 on engine performance and emission characteristics.
Conventional compression ignition engines can easily be converted to a dual fuel mode of operation using natural gas as main fuel and diesel oil injection as pilot to initiate the combustion. At the same time, it is possible to increase the output power by increasing the diesel oil percentage. A detailed performance and combustion characteristic analysis of a heavy duty diesel engine has been studied in dual fuel mode of operation where natural gas is used as the main fuel and diesel oil as pilot. The influence of intake pressure and temperature on knock occurrence and the effects of initial swirl ratio on heat release rate, temperature-pressure and emission levels have been investigated in this study. It is shown that an increase in the initial swirl ratio lengthens the delay period for auto-ignition and extends the combustion period while it reduces NO x . There is an optimum value of the initial swirl ratio for a certain mixture intake temperature and pressure conditions that can achieve high thermal efficiency and low NO x emissions while decreases the tendency to knock. Simultaneous increase of intake pressure and initial swirl ratio could be the solution to power loss and knock in dual fuel engine.
The present paper aims to assess the impacts of diesel injection timing and two bowl geometries including re-entrant and wide-shallow combustion chambers on the combustion characteristics, emissions formation, and fuel consumption in a reactivity controlled compression ignition diesel engine under low and high load (five and nine bar indicating mean effective pressure) conditions. The results revealed that diesel injection at −60 CA ATDC under low load conditions significantly decreased soot and NOx emissions simultaneously for both piston bowl geometries. The use of the wide-shallow chamber decreased the period of the ignition delay and increased the engine operable load range as a result of more stable combustion under high-load conditions compared to the re-entrant chamber. Moreover, at all diesel injection timings, the indicated specific fuel consumption was decreased by nearly 4.8 and 6.6% under low and high load conditions, respectively when the wide-shallow combustion chamber was used since the heat transfer loss was lower than that of the re-entrant chamber. However, NOx emission under high load conditions at the center of the combustion chamber and more soot emission in the exhaust gas are two disadvantages of the wide-shallow chamber versus the re-entrant combustion chamber.
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