Search Results

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.

Fuel quality, including antiknock rating, plays a critical role in enabling optimal operation of advanced gasoline engines. As new designs introduced into the market implement technologies to improve fuel efficiency, the overall octane level of the gasoline pool may need to be increased to ensure optimal performance. Turbocharging, higher compression ratios and downsized displacement all lead to higher combustion pressures and temperatures that make engines more susceptible to knocking. All modern gasoline engines are equipped with knock sensors that detect abnormal combustion resulting from autoignition caused by insufficient octane quality. The ability of an engine to account for the use of lower octane fuel by retarding spark timing and enriching air-fuel ratio to reduce knock is limited, and engine efficiency is directly and adversely impacted when the use of lower octane gasoline is accommodated, resulting in higher fuel consumption.

Unregulated emissions have become an important factor restricting the development of methanol and ethanol alternative alcohols fuels. Using two light-duty vehicles fuelled with pure gasoline, gasoline blend of 10% and 20% volume fraction of ethanol fuels, gasoline blend of 15% and 30% volume fraction of methanol fuels, New European Driving Cycle (NEDC) emission tests were carried on a chassis dynamometer according to ECE R83-05. High performance liquid chromatography (HPLC), Gas chromatography - Mass spectrometry (GC-MS), Fourier transform infrared spectrometer (FTIR) were used to measure methanol, formaldehyde, acetaldehyde, acetone, benzene, toluene, xylene, ethylene, propylene, 1,3-butadiene and isobutene emissions in the exhaust during the NEDC.

In this paper blends of diesel and gasoline (dieseline) fuelled Partially Premixed Compression Ignition (PPCI) combustion and the comparison to conventional diesel combustion is investigated. The tests are carried out using a light duty four cylinder Euro IV diesel engine. The engine condition is maintained at 1800 rpm, 52 Nm (equivalent IMEP around 4.3 bar). Different injection timings and different amounts of EGR are used to achieve the PPCI combustion. The results show that compared to the conventional diesel combustion, the smoke and NOx emissions can be reduced by more than 95% simultaneously with dieseline fuelled PPCI combustion. The particle number total concentration can be reduced by 90% as well as the mean diameter (from 54 nm for conventional diesel to 16 nm for G50 fuelled PPCI). The penalty is a slightly increased noise level and lower indicated efficiency, which is decreased from 40% to 38.5%.

A new combustion mode namely multiple premixed compression ignition (MPCI) for gasoline engines was proposed. The MPCI mode can be realized by two or more times gasoline injections into cylinder with a high pressure around the compression TDC and featured with a premixed combustion after each injection in the cylinder, which is different from the existed gasoline direct injection compression ignition (GDICI) modes such as homogeneous charge compression ignition (HCCI) mode with gasoline injection occurred in intake stroke, and partially premixed compression ignition (PPCI) mode with multiple gasoline injections in intake and compression strokes before the start of combustion (SOC). Therefore the spray and combustion of the MPCI mode are alternatively occurred as "spray-combustion-spray-combustion" near the TDC, rather than "spray-spray-combustion" sequence as traditional PPCI gasoline engines.