Structure, Extinction & Ignition of Non-Premixed Flames in the Counterflow Configuration

Counterflow burners consist of steady, axisymmetric, laminar flows of two counterflowing reactant streams toward a stagnation plane. These burners can be used to experimentally study and develop detailed chemical mechanisms of combustion under a wide range of conditions. Global flame parameters such as the critical limits of extinction and autoignition, as well as flame structure, including flame temperatures and species concentrations can be measured and tested against established reaction mechanisms using 1D numerical model with known conditions at the duct exits.

This presentation is a compilation of experimental and numerical investigations into the gas-phase combustion characteristics of nitramine monopropellants. An improved understanding of hydrocarbon and nitrogen containing compounds is a first step in understanding key aspects of combustion of hypergolic and gun propellants.

The fuel stream consists of a mixture of nitrogen diluted ethane (C2H6) or methane (CH4). The oxidizer stream consists of a mixture of oxygen, nitrogen and nitrous oxide (N2O). The two streams are momentum balanced such that the stagnation plane rests at the midpoint between the two ducts. Numerical studies are performed and validated against experiments using the DARS 1D counterflow diffusion model and the San Diego mechanism.

DARS proved to be significantly faster and more consistent at finding converged numerical solutions than other commercial solvers used, especially near the limits of extinction and auto-ignition, when the solver must jump from a flame solution to a frozen flow solution or vice-versa. This, along with the tools for reducing mechanisms, performing sensitivity analysis and identifying reaction pathways proved DARS to be of great use in this work.

Ryan Gehmlich
Speaker Company: 
University of California