An Experimental Study on the Improvement of Engine Performance and Exhaust Emissions from Small-scale PCCI Engines Fuelled by Natural Gas 2005-01-2124

To characterize the suitable conditions for a natural gas PCCI (premixed charge compression ignition) engine to provide both high efficiency and low emissions, an experimental study was demonstrated using a small-scale, single-cylinder engine. Engine tests were systematically carried out with various parameters, including compression ratio (18 to 22), intake-air temperature (160 to 220 °C) and engine speed (800 to 2400 rpm). It was shown that the maximum specific power can be improved in proportion to an engine speed up to 2400 rpm, while both the indicated thermal efficiency over 32% and the NOx emission below 100 ppm can be retained. However, an increase in engine speed extends the combustion duration especially under lean conditions, which decreases the indicated thermal efficiency.