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Ammonia is a promising carbon-free alternative fuel for use in combustion systems. The main associated challenges are its relatively low reactivity and high NOx emissions compared to conventional fuels. Therefore, the combustion behaviour of ammonia and ammonia blends still needs to be better understood over a wide range of conditions. To this end, a comprehensive chemical kinetic mechanism C3MechV3.4, which is an update of C3MechV3.3, has been developed for improved predictions of the combustion of ammonia and ammonia blends. C3MechV3.4 has been validated using a wide range of experimental results for pure ammonia and ammonia/hydrogen, ammonia/methanol and ammonia/n-heptane blends. These validations target different data sets including ignition delay times, species profiles measured as a function of time, and/or temperature and laminar flame speeds over a wide range of conditions.

Based on a composed PRF/ethanol/PAH mechanism, simulations were conducted to investigate the combustion characteristics of n-heptane spray under premixed ethanol/air and iso-octane/air atmosphere in a combustion vessel. The effects of premixed ethanol and iso-octane on ignition delay, important soot precursors and soot volume fraction of n-heptane spray were studied. Also, simulated results with and without considering the cooling effects of premixed fuel vaporization were compared. When the cooling effect of premixed fuel vaporization was not considered, simulations showed that premixed ethanol could increase the ignition delay of n-heptane spray at ambient temperatures below 850K. However, premixed iso-octane showed little inhibition effect on ignition of n-heptane spray. Also, it was found that both premixed ethanol and iso-octane contributed to faster ignition under high ambient temperatures.

In this paper, experiments and simulations were conducted to investigate the cyclic variations of gasoline/diesel and ethanol/diesel dual-fuel combustion. For both dual-fuel modes, gasoline and ethanol were injected into the intake port during the intake stroke and diesel was directly injected into the cylinder. The influences of engine load and port fuel proportion on the cyclic variability of both dual-fuel modes were investigated. At each test condition, in-cylinder pressure traces of 150 consecutive cycles were acquired. Then the cyclic variations of ignition timing (CA5), combustion phasing (CA50), accumulated heat release (Qf) and indicated mean effective pressure (IMEP) were calculated based on the in-cylinder pressure. The experimental results showed that the cyclic variation of IMEP was mainly caused by the variation of Qf for both dual-fuel modes.

PPCI in diesel engine is a combustion mode between conventional diesel combustion and homogeneous charge compression ignition (HCCI) combustion, which has the potential to simultaneously reduce NOX and soot emissions and improve thermal efficiency. N-butanol as a kind of clean and renewable biofuel can effectively prolong ignition delay and enhance fuel/air mixing because of their low cetane number, high volatility fuel characteristics, which make it a better alternative fuel to achieve PPCI. In this paper, PPCI combustion in a boosted four-cylinder diesel engine fueled with n-butanol-diesel blends is realized by adjusting injection timing and EGR rate based on single injection. The results show that both early and late injection have long premixed duration, which is helpful to form more homogeneous mixture, and no diffusion combustion is found in heat release rate curve. Premixed combustion and low temperature combustion are the key factors to reduce PM and NOX.