Feasibility Study of Ethanol Applications to A Direct Injection Gasoline Engine 2007-01-2037
Feasibility studies concerning ethanol utilization in direct injection gasoline engines were conducted in order to clarify the effects of ethanol on engine performance, exhaust emissions and injector deposit formation. The investigation results indicate that E100 (100% ethanol fuel) can improve full load engine performance around whole engine speed range in a high compression ratio engine (ε=13:1), compared to that of a base compression ratio engine (ε=11.5:1) operated on a premium gasoline. This was caused by the volumetric efficiency (ηv) improvement and engine knock suppression in the high compression ratio engine.
On the other hand, HC emissions remarkably increased under lower engine speeds at a full load condition. This phenomenon suggests that poor combustion occurred due to insufficient mixing of air and E100 fuel under these conditions, in which the amount of ethanol injected was too large and fluidity in the cylinder was weak. However, compared to premium gasoline, E100 has a somewhat better thermal efficiency and lower HC and NOx emissions at a partial load.
Furthermore, the results of feasibility study shows that ethanol could suppress injector deposit formation and this effect was observed in the fuel of only a 20% ethanol blending. It is considered that this is caused by the synergy effects of high latent heat of ethanol vaporization, resulting in reduction of injector nozzle temperature, and reduction of aromatics and sulfur contents in a fuel.
The results of feasibility study reveal that application of ethanol fuel to direct injection gasoline engines can produce some customer merits such as a full load performance improvement, injector deposits suppression, and so on. However, there are also some technical issues and it is necessary to optimize the direct injection gasoline engine system for using ethanol fuel.