Quantification of differential diffusion in nonpremixed systems.
- University of Utah, Salt Lake City, UT
Most attempts to quantify differential diffusion (DD) are based on the difference between different definitions of the mixture fraction. This paper presents a general method for evaluating differential diffusion in premixed or nonpremixed systems based on conservation equations for the elemental mass fractions. These measures form a basis for analyzing differential diffusion. Casting these in terms of a mixture fraction gives particular insight into differential diffusion for nonpremixed systems, and provides a single DD measure. Furthermore, it allows direct evaluation of the validity of the traditional assumptions involved in writing a mixture fraction transport equation. Results are presented for one-dimensional opposed flow simulations of hydrogen and methane flames as well as direct numerical simulations (DNS) of CH 4 /H 2 -air and CO/H 2 -air flames. For a common definition of the mixture fraction, the DD measure can be approximated well by considering only the contribution of H 2 and CH 4 in methane-air flames. Differential diffusion is largely driven by production of H 2 in the flame zone for hydrocarbon flames. Effects of strain rate and filter width on the relative importance of differential diffusion are examined.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 953315
- Report Number(s):
- SAND2004-2935J; TRN: US200915%%179
- Journal Information:
- Proposed for publication in Combustion Theory & Modelling., Journal Name: Proposed for publication in Combustion Theory & Modelling.
- Country of Publication:
- United States
- Language:
- English
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