Abstract
Premixed charge compression ignition (PCCI) engine has been widely studied due to the potentials for simultaneous reduction on the NOx and Particulate Matter (PM) emissions , however, early fuel injection timing with conventional multi-hole nozzle diesel engine increase wall quenched fuel onto the piston surface and cylinder wall. These engines have problems such as high unburned hydrocarbon (UHC) and CO emissions and the difficulty of ignition timing control. In this study, direct fuel impingement and distribution system, named Onishi Shototsu Kakusan (OSKA) was applied to PCCI engine in order to reduce UHC emissions. A commercially available single cylinder DI diesel engine was modified for OSKA-PCCI engine. The cylinder head was modified as to set pintle type fuel injection nozzle vertically in center of cylinder. Piston cavity was also modified from toroidal type to re-entrant type cavity with impinging part in the center of cavity. An impinging part is set in the center of piston cavity, as fuel spray is trapped in piston cavity to prevent fuel spray cylinder wall quenching, even if very early fuel injection timing is employed for PCCI engine operation condition. The Ethyl Tertiary Butyl Ether (ETBE) is one of oxygenated fuel which has the properties of low boiling point and low ignitability. The ETBE blended diesel fuels were tested to control the ignition delay for PCCI engine. Three different ETBE blenede fuels with ETBE content of 0 % (diesel fuel), 20 %, and 40 % in weight were used. With the high ETBE content fuel, since the longer ignition delay was observed, the operation with high compression ratio is possible without suffering from the early ignition. As a result, the brake thermal efficiency was shown same level of base DI diesel engine. And very low NOx emissions and relatively low unburned emissions were obtained with ETBE 40% fuel.
Keywords: Compression Ignition Engine, PCCI Engine, Exhaust Emissions