The effect of carbon monoxide (CO_2) dilution on end-gas auto-ignition of stoichiometric iso-octane/oxygen/nitrogen mixture was studied using a rapid compression machine. Both the combustion process and pressure traces were recorded synchronously. Nine cases with the same energy density but with different compression ratios and CO_2 dilution ratios were tested. The results showed that CO_2 dilution could reduce the knock intensity but prolong the combustion duration. The reason for the knock intensity reduction was attributed to the suppression of detonation caused by the CO_2 dilution. Additionally, the dimensionless analysis was carried out using two parameters (ε and ξ) proposed by Bradley [1]. The results showed that ε decreased with the increasing CO_2 dilution ratio, and under high CO_2 dilution ratio ξ decreased with increasing compression ratio.
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