PDF MODELING OF CO AND NO FORMATION IN LEAN PREMIXED METHANE FLAMES

Abstract

In this paper, CO and NO formation in a premixed turbulent methane flame is simulated with a stochastic model of combustion. The model proposed is a combination of both the computational fluid dynamics and the Monte Carlo methods for the solution of the joint probability density function. Finite chemical kinetics is represented by a GRI-derived reduced-chemistry model. This resultant model is used to simulate a lean, premixed, bluff-body, stabilized flame for which experimental data are available. Under this condition, the prediction of NO formation is a challenge because of its low concentrations (typically a few parts per million) and because every NO-formation route is relevant. The model used for the molecular mixing includes a variable mixing time, covering the range from the Kolmogorov scale to the integral scale. A lookup table is used to estimate the thermochemical properties and is found to be more adequate than direct integration. The results are compared with an experimental database.

Keywords:

• PDF
• lean premixed combustion
• CFD
• Monte Carlo method
• NO_x

The authors are very grateful to J.Y. Chen (University of California at Berkeley) for his advice and stimulating discussions. Work in PDF modeling for turbulent flames by the Fluid Mechanics Groups from the University of Zaragoza and UNAM is partially supported by the European Union under project BE 95-1927 and at the Instituto de Ingeniería under project FI³.