The Role of Diffusive Transport on Low and Intermediate Temperature Hydrocarbon Oxidation: Closed Reactor Experiments Using Equimolar n–C₄H₁₀ + O₂ Premixtures at Reduced-Gravity

Abstract

Experiments were conducted in a closed, spherical reactor aboard NASA's KC-135 reduced-gravity aircraft using an equimolar n–C₄H₁₀ + O₂ premixture (Le = 1.3) at subatmospheric pressures to compliment model predictions and further explore the reactive-diffusive structure of cool flames and ignitions. The pressure and radial temperature histories were recorded and analyzed for different initial conditions. In addition, the visible light emission from excited formaldehyde was recorded using an intensified video camera and was observed to be radially symmetric in all cases. Unexpectedly, however, the measured temperature distributions during (and after the passage of) the cool flames and ignitions were not parabolic as predicted by conduction models, which suggests the onset of weak convection at 10⁻² g.

Keywords:

• Cool flames
• Microgravity
• Reaction-diffusion
• Static reactor
• Two-stage ignition

Acknowledgments

Special thanks are extended to Ming-Shin Wu, Richard Chapek, Donna Neville, and Scott Numbers at NASA GRC for programmatic and flight support for the microgravity experiments. This work was funded by NASA under grant NCC3-1006. The authors acknowledge financial support for MF from the NSF Graduate Research Fellowship Program.