- Author
-
Macek, A.
- Title
- Flammability Limits: Thermodynamics and Kinetics. Final Report.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Report
-
NBSIR 76-1076; WSS/CI 75-28,
May 1976,
22 p.
- Distribution
- Available from National Technical Information Service
- Book or Conf
- Combustion Institute/Western States Section. Fall Meeting, 1975. October 20-21, 1975,
Menlo Park, CA,
1-20 p.,
1976
- Keywords
-
reaction kinetics
|
diffusion flames
|
flame extinguishment
|
flame temperature
|
flame velocity
|
flammability
|
flammability limits
|
oxygen index test
|
thermodynamics
- Abstract
- Extinction limits for both premixed and diffusion flames for n-alkanes and n-alcohols found in the literature are assembled. Several sets of theoretical flame temperatures corresponding to the limits are defined and presented. The implications of the view that flames fail to propagate at temperatures at which reaction rates become too low to overcome the dissipation proceses are discussed. Equilibrium flame temperatures indicate that at lean limits the excess oxygen does not act merely as a diluent but takes an active part in promoting the kinetics of flame reactions. The burning-rate data and the results of ignition experiments are shown to be pertinent to the interpretation of flammability limits. Extinction characteristics of methane are shown to be atypical (compared to other alkanes and alcohols) and demand a special explanation. It is also shown that the assumption of thermodynamic equilibrium at the limits is unrealistic, so there is need for experimental temperature and concentration measurements in both premixed and diffusion flames. When the assumption of equilibrium is removed, the chemical kinetic considerations suggest a simple qualitative explanation of the limit phenomenon, based on the stipulation of incomplete combustion. Quantitative data are presented in support of this view.