Mechanism Analysis on the Effect of Fuel Properties on Knocking Performance at Boosted Conditions of S. I. Engine 2019-01-0035
Recently, boosted and downsized engines are widely spread as a promising technology to improve fuel economy. To understand the knocking phenomenon under boosted conditions of such downsized engines deeply, fuels with different research octane number(RON) and motor octane number (MON) are prepared. Then the knocking performance of these fuels was evaluated using a single cylinder engines. Experimental results showed that the knocking performance at boosted conditions depends on both RON and MON. While higher RON showed better anti-knocking performance, lower MON showed better anti-knocking performance.
Furthermore, this tendency of negative sensitivities of MON became stronger at lower engine speed and higher boost pressure. To analyze the mechanism of this knocking dependency on fuel properties and operating conditions, zero dimensional knocking prediction with elementary reactions was conducted. The different knocking dependencies on RON and MON at various operating conditions were well explained by the contribution of low temperature oxidation which changes with actual time length and oxygen density.