The effect of different class of hydrocarbons on laminar flame speeds of three C7 fuels

The effect of different class of hydrocarbons on laminar flame speeds of three typical C7 fuels was investigated experimentally and numerically in this study. The three classes of C7 hydrocarbons are the n-heptane (alkane), methylcyclohexane (cycloalkane) and toluene (aromatic). Their laminar flame speeds were measured in a constant volume combustion bomb. The experimental results are Su,n-heptane(alkane)0>Su,methylcyclohexane(cycloalkane)0>Su,toluene(aromatic)0 under all tested conditions, and the difference in their speeds are found to be insensitive to the initial pressure. Analyses of the three classes of C7 hydrocarbons show that the alkanes with the highest H/C ratio have the greatest laminar flame speed, while the aromatics with the smallest H/C have the slowest laminar flame speed. The laminar flame speed discrepancy between the alkanes and cycloalkanes is smaller because their difference in H/C ratio is less than that between aromatics and cycloalkanes.