Study on Robust Fuel Performance with Differing Fuel Types in a 2-Stroke CAI Combustion Engine 2019-32-0573
This study sought to achieve robust combustion with the differing fuel types and levels of fuel quality that are present in various areas of the world. The tests used the 2-stroke controlled auto ignition (CAI) engine from our earlier report , which was proven to have potential as an efficient, clean engine for diesel fuel. This study verified whether efficient, clean CAI combustion of gasoline fuel could be achieved with the same basic structure and engine system.
Diesel and gasoline have very different volatility, viscosity and ignition characteristics, all of which significantly affect combustion in an engine. It is particularly necessary in CAI combustion to adjust the ignition timing according to the fuel used, as the difference in auto-ignition temperature from gasoline and diesel affects the CAI ignition timing. This issue was addressed by conducting experiments with a test engine to determine how the ignition timing is affected by the equivalent ratio, compression ratio and in-cylinder flow, and the ideal solution was verified.
The results indicated that the ignition timing for CAI combustion can be effectively adjusted by changing the shape of the scavenging port to alter the in-cylinder flow. Computational fluid dynamics (CFD) analysis confirmed that the change in the scavenging port shape increased the in-cylinder flow velocity and the turbulence kinetic energy at the compression end. This indicates that the in-cylinder flow during the compression stroke affects the ignition timing for CAI combustion.
The results produced by this study also indicated that equivalent thermal efficiency and emission levels can be achieved for both diesel and gasoline by setting an appropriate equivalent ratio, compression ratio, in-cylinder flow and exhaust valve lift profile for each type of fuel.
In conclusion, this study confirmed that 2-stroke CAI is a combustion process with extremely robust fuel performance and the potential to be suitable for various fuel types with significantly different properties.