Flametube Studies of Wall Quench

Hydrocarbon wall quenching has been studied using a 19mm diameter, 1m long combustion tube, open at one end. Mixtures of propane, heptane, iso-octane and gasoline, initially quiescent, were burnt with the ignition source at the closed end. The post-flame HC levels were measured at a series of axial locations using a fast FID. The results indicate that the effective quench layer thickness increases significantly as the molecular weight of the fuel is increased. The diffusion/mixing time constant of the quench layer was found to be approximately 0.1s for propane, 0.4s for iso-octane and 1.0s for gasoline. The axial variation of residual HC levels suggests that flame stretch is a factor influencing the extent of the quench layer.