Abstract
The effects of pressure on outwardly propagating laminar and turbulent flames were studied for propane-air mixtures at the equivalence ratios from 0.8 to 1.3 and the initial pressures from 0.10 to 0.50 MPa. Turbulence intensity, u' was set to 0.80 and 1.59 m/s. The Markstein number was employed to quanify the effects of the equivalence ratio and the pressure of the mixture on laminar and turbulent burning velocities. Turbulent burning velocities, utn did not become small with the increase in the mixture pressure although the unstertched laminar burning velocities, ul decreased with the mixture pressure. The ratios of turbulent burning velocities to unstretched laminar ones, utn/ul increased as the mixture pressure increased. They also increased with the increase in the equivalence ratio. We found that utn/ul increased with the decrease in the Markstein number irrespective of the equivalence ratio, the initial mixture pressure and the turbulence intensity if u'/ul did not vary so much. Turbulent burning velocities were affected not only by turbulence but also by the thermo-diffusive effects and flame instabilities both related to the Markstein number.
