Combustion Modeling Lab at UC Berkeley

Past Research

Reduced Mechanisms for Prediction of NO2 Formation in Methane-Air Combustion

J.Y. Chen (CML)

R. Homma (Tokyo Gas Co., Ltd. Energy Research Technology Institute)

The Second Asia-Pacific Conference on Combustion (ASPACC-99), Tainan, Taiwan, 1999


Two new 14-step and 16-step reduced mechanisms for methane-air combustion were developed with the emphasis on their capabilities to predict NO2 formation. The systematic reduction was carried out by assuming the quasi-steady state for 26~28 species in the starting mechanism with the help of a automatic mechanism reduction code. The two reduced mechanisms reproduce NO2 formation behaviors obtained with the starting mechanism both in post flame region and in opposed diffusion flames. The promotion of NO2 formation by hydrocarbon additive was also successfully predicted by the reduced chemistry. In addition, the reduced chemistry is accurate in predicting the diffusion flame structure and the ignition delay time.


Nitrogen dioxide emission from combustion devices is a concerned issue because of its higher toxicity than nitrogen oxide. In spite of this fact, there have been no previous studies attempted at developing concise reaction mechanisms that can be used in practical CFD simulations. The present paper is aimed at proposing such new reduced mechanisms based on quasi-steady state assumption(QSSA). The development of reduced mechanisms for NO2 formation is also of great interest in terms of exploring the applicability of QSSA to low temperature combustion phenomena.

In this study, we will present two new 14-step and 16-step reduced mechanisms aiming at the use in turbulent flame simulation. Since even a single turbulent flame contains fundamentally different combustion zones, the reduced mechanisms were tested extensively under various situations such as post flame mixing region, CO/H2-air diffusion flame and CH4-air diffusion flame. The ignition delay time of the methane-air mixture was also examined, since it possibly affects the global flame structure through local flame stability.

Paper (.pdf)

Mechanism Desciption File (14-step)*
Chemical Source (14-step)**
Mechanism Desciption File (16-step)*
Chemical Source (16-step)**
Chemical Source (16-step, NEW)** (mathematically equivalent, but faster)

*The input file for CHEMKIN interpreter (ckinterp.f)
**Please replace subroutine CKWYP in CHEMKIN(cklib.f) with this file