Sample probe measurements on a hydrogen-ethane-air-2-H-heptafluoropropane flame

This paper describes experiments and numerical modeling of a lean premixed, atmospheric pressure (phi = 0.55) hydrogen-ethane-air flat flame with 1.5 mol % of CF3CHFCF3, Stable species concentrations as a function of height a bove the burner were obtained by sampling with a water-cooled quartz probe; these gases were subsequently analyzed by infrared spectroscopy. Numerical modeling of this flame was performed with a detailed chemical kinetic mech anism. Discrepancies between modeled and experimental concentrations were a ttributed to external probe-induced distortions. A phenomenological treatme nt of the external distortion gave reasonable agreement for all species. Pl ug-flow calculations were performed to determine the extent of sample compo sition change within the probe. These showed that homogeneous gas-phase rea ctions did not cause any changes to the sample. A surface oxidation channel was included to simulate CO loss. Reaction flux analyses revealed that fla me inhibition arises from H- and O-atom, and to a lesser extent CH3 radical , consumption by the fluorinated fragments CF3, CF2, and CFO. Consumption o f OH radicals appeared to be relatively inefficient. A concentration sensit ivity analysis on the species CO and CF2O was performed to show that reacti ons between CFB radicals and the major flame radicals were sensitive. The c oncentrations of these species were only mildly sensitive to reactions invo lving larger fluorinated species.