Effect of Fuel Chemical Compositions on Combustion and Autoignition Characteristics in Gasoline Surrogate Fuel

Abstract

In this study, three types of gasoline surrogate fuels were used to investigate the effect of fuel chemical composition on combustion and auto-ignition characteristics. For the study, an optically accessible engine capable of velocity analysis was used to observe the combustion and auto-ignition behavior. The results showed that the knock intensity of TRF with high toluene content was lower than that of S5R due to the OH consumption effect during combustion, but the knock suppression effect of toluene weakened at higher temperature and pressure conditions. Next, as the reason why auto-ignition did not occur only for PRF 82.6, the combustion rate analysis and chemical reaction numerical analysis indicate that the cold flame reaction and H2O2 reaction loop are more active in PRF 82.6 than in the other fuels, resulting in a shorter ignition delay and faster flame spread speed, and thus no auto-ignition occurred. Conversely, in TRF and S5R, the OH consumption effect by toluene and the suppression of the cold flame reaction and H2O2 reaction loop resulted in a slower flame spread velocity than in PRF 82.6, which created a time delay before auto-ignition and thus auto-ignition occurred. In addition, it can be inferred that the main reason for the frequent occurrence of wall auto-ignition in S5R is that, unlike PRF 82.6, this fuel does not have an NTC region.