No abstract

In this study, a single-cylinder, water-cooled, direct-injection, compression ignition (CI) engine is operated on the homogeneous charge CI (HCCI) mode using acetylene and diethyl ether (DEE) as fuels. Acetylene is inducted as a main fuel and a small quantity of DEE is injected into the intake manifold for controlling combustion phasing. The engine performance and exhaust emission characteristics are investigated experimentally under various operating conditions. From the results, it is found that brake thermal efficiency of the acetylene-DEE HCCI mode is comparable with that of the conventional CI mode. It has a wide operating range of 0-4.2 bar brake mean effective pressure without exhaust gas recirculation compared with the liquid fuels-HCCI mode. The engine could easily start in the HCCI mode using DEE alone. Nitric oxide and smoke emissions are at ultra-low level. Hydrocarbon emissions are comparatively lower at lower loads and higher at higher load conditions. Carbon monoxide emissions are comparable with that of the conventional CI mode.

This paper deals with experimental investigations carried out to develop an exhaust gas recirculation (EGR) strategy for an acetylene-fuelled homogeneous charge compression ignition (HCCI) engine. This study involves an analysis of the external inlet charge heating, the use of a mix of hot EGR and cool EGR to extend the load range, and the performance of the engine in the acetylene HCCI mode. First, experiments are conducted on a single-cylinder engine in the acetylene HCCI mode with external electrical heating at different load conditions, and the best inlet charge temperatures at each load condition are obtained. Second, hot EGR or a mix of hot EGR and cool EGR (i.e. the EGR strategy) is used to reduce or eliminate external charge heating and to extend the upper load limit, or to improve the brake thermal efficiency. In both cases, the engine performance is compared with that of the conventional diesel compression ignition (CI) mode. It is found that with EGR, above 25 per cent of load, the upper load limit at different inlet charge temperatures increases by about 16 28 per cent without any external charge heating. Below 25 per cent of load, the electrical heating at different inlet charge conditions is reduced by about 67–87 per cent. The brake thermal efficiency increases by 5–24 per cent under all the load conditions and it is comparable with that in the conventional CI mode. In the HCCI mode, nitrogen oxide levels are less than 20ppm. Smoke levels are always lower than 0.1 Bosch smoke unit. Hydrocarbon and carbon monoxide emissions are relatively higher than for the conventional CI mode.