Laser-Induced Fluorescence Measurements of OH in Laminar C₂H₆/O₂/N₂ Flames at High Pressure

Abstract

Using the laser-induced fluorescence method, we have measured relative OH concentration profiles in flat laminar, lean premixed C₂H₆/O₂/N₂, flames at 3.2, 6.3, 9.5, and 12.6 atm. By employing a range of flow rates of the combustible mixture, we demonstrate that the reaction zone can be probed at these pressures. In comparison to atmospheric flames, the reaction zone was small and accordingly the [OH] gradient was large; we also observed large gradients in the OH recombination zone. A result of the large gradients is an increase in the noise of the fluorescence signal compared to that at atmospheric pressure. Another impediment to making measurements was beam steering resulting from flame instability, which increased with pressure. We therefore limited our measurements to 12.6 atm.