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Combustion behaviour and emissions characteristics of different blending ratios of diesel and gasoline fuels (Dieseline) were investigated in a light-duty 4-cylinder compression-ignition (CI) engine operating on partially premixed compression ignition (PPCI) mode. Experiments show that increasing volatility and reducing cetane number of fuels can help promote PPCI and consequently reduce particulate matter (PM) emissions while oxides of nitrogen (NOx) emissions reduction depends on the engine load. Three different blends, 0% (G0), 20% (G20) and 50% (G50) of gasoline mixed with diesel by volume, were studied and results were compared to the diesel-baseline with the same combustion phasing for all experiments. Engine speed was fixed at 1800rpm, while the engine load was varied from 1.38 to 7.85 bar BMEP with the exhaust gas recirculation (EGR) application.

The demand for more efficient and clean engines have prompted the research and development of new engine technologies. Automotive engines expected to run with leaner mixtures and higher compression ratios. Lean burn is effective to increase fuel economy whilst reducing emissions but unreliable ignition of the lean mixtures by the conventional spark plug is one of the problems which causes concerns to the engine designers. Laser ignition is a promising technology and holds many benefits over the spark ignition because it can extend the ignitability of lean mixtures with flexibility of the ignition location and absence of electrode degradation for improved engine performance with lean burn. In this study, high-speed photography is used to investigate the flame kernel growth and propagation in an optical direct injection engine using laser ignition by an Nd:YAG laser.

n-butanol has been recognized as a promising alternative fuel for gasoline and may potentially overcome the drawbacks of methanol and ethanol, e.g. higher energy density. In this paper, the spray characteristics of gasoline and n-butanol have been investigated using a high pressure direct injection injector. High speed imaging and Phase Doppler Particle Analyzer (PDPA) techniques were used to study the spray penetration and the droplet atomization process. The tests were carried out in a high pressure constant volume vessel over a range of injection pressure from 60 to 150 bar and ambient pressure from 1 to 5 bar. The results show that gasoline has a longer penetration length than that of n-butanol in most test conditions due to the relatively small density and viscosity of gasoline; n-butanol has larger SMD due to its higher viscosity. The increase in ambient pressure leads to the reduction in SMD by 42% for gasoline and by 37% for n-butanol.

A study of Multiple Premixed Compression Ignition (MPCI) with heavy naphtha is performed on a light-duty single cylinder diesel engine. The engine is operated at a speed of 1600rpm with the net indicated mean effective pressure (IMEP) from 0.5MPa to 0.9MPa. Commercial diesel is also tested with the single injection for reference. The combustion and emissions characteristics of the heavy naphtha are investigated by sweeping the first (−200 ∼ −20 deg ATDC) and the second injection timing (−5 ∼ 15 deg ATDC) with an injection split ratio of 50/50. The results show that compared with diesel combustion, the naphtha MPCI can reduce NOx, soot emissions and particle number simultaneously while maintaining or achieving even higher indicated thermal efficiency. A low pressure rise rate can be achieved due to the two-stage combustion character of the MPCI mode but with the penalty of high HC and CO emissions, especially at 0.5MPa IMEP.

Little research has been done on spray characteristics of 2,5-dimethylfuran (DMF), since the breakthrough in its production method as an alternative fuel candidate. In this paper, the spray characteristics of pure fuels (DMF, Isooctane) and DMF-Isooctane blends under different ambient pressures (1 bar, 3 bar and 7 bar) and injection pressures (50 bar, 100 bar and 150 bar) were studied using Phase Doppler Particle Analyzer (PDPA) and high speed imaging. Droplet velocity, size distribution, spray angle and penetration of sprays were examined. Based on the results, DMF had larger SMD and penetration length than isooctane. The surface tension of fuel strongly influenced spray characteristics. Increasing the surface tension by 26 % resulted in 12 % increase in SMD. Higher ambient pressure increased the drag force, but SMD was not influenced by the increased drag force. However, the increased ambient pressure reduced the injection velocity and We number resulting in higher SMD.