Nicolas Meynet

Application of continuation techniques to ammonium perchlorate plane flames

We investigate an interface model for ammonium perchlorate (AP) monopropellant flames. The model includes complex chemistry and detailed transport in the gas phase and heat conduction in the solid phase. The interface condition considers sublimation of AP as well as reaction products obtained through a liquid phase. The resulting parameterized two-point boundary value problem is solved by a phase-space, pseudo-arclength, continuation method that employs Euler predictors, Newton-like iterations and global adaptive gridding techniques. We establish that the use of Dirichlet boundary conditions for temperature at the solid phase cold boundary leads to unphysically extinguished flames. We simulate preheated low pressure flames as well as high pressure flames in good agreement with experimental results. We finally obtain qualitative pressure extinction limits of AP flames subjected to heat losses. The work represents a critical step in the ultimate solution of the multidimensional coupled gas and condensed phase propellant problem.

Numerical assessment of accurate measurements of laminar flame speed

In combustion, the laminar flame speed constitutes an important parameter that reflects the chemistry of oxidation for a given fuel, along with its transport and thermal properties. Laminar flame speeds are used (i) in turbulent models used in CFD codes, and (ii) to validate detailed or reduced mechanisms, often derived from studies using ideal reactors and in diluted conditions as in jet stirred reactors and in shock tubes. End-users of such mechanisms need to have an assessment of their capability to predict the correct heat released by combustion in realistic conditions. In this view, the laminar flame speed constitutes a very convenient parameter, and it is then very important to have a good knowledge of the experimental errors involved with its determination. Stationary configurations (Bunsen burners, counter-flow flames, heat flux burners) or moving flames (tubes, spherical vessel, soap bubble) can be used. The spherical expanding flame configuration has recently become popular, since it can be used...