Conditional probability density functions measured in turbulent nonpremixed flames of methane near extinction

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Combust. Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(88)90073-9· OSTI ID:6538456

Masri, A R; Bilger, R W ^[1]; Dibble, R W ^[2]

---

1. Dept. of Mechanical Engineering, Univ. of Sydney, NSW 2006 (AU)
2. Combustion Research Facility, Sandia National Labs., Livermore, CA (US)

Spontaneous Raman-Rayleigh measurements of temperature and species concentrations have been made in turbulent nonpremixed flames of methane close to extinction. For each data point, five different values of reactedness are calculated from the measured temperature and the mass fractions of CH/sub 4/, O/sub 2/, H/sub 2/O and CO/sub 2/. These data are then sampled with respect to five ranges of mixture fraction and the conditional single and joint probability density functions (PDFs) of reactedness calculated from the various reactive scalars are presented for each range. Conditional means and root mean squares (rms) of fluctuations of reactedness, temperature, and species mass fractions are also presented. It is found that for mixture fraction ranges lying below the rich reaction limit, xi < xi/sub R/ (xi/sub R/ = 0.087 for methane) combustion is generally bimodal and fluid samples are either fully burned or unburned. For ranges with xi > xi/sub R/, the majority of mixtures are partially reacted and the conditional PDFs have centered distributions. The correlation between the conditional PDFs of various reactive scalars indicate that more than a single-step reaction mechanism is required to adequately describe the chemistry. Close to extinction, the flame was kept alight by fully burned pockets of fluid that provide a source of reignition for mixtures with slower mixing rates. The flame blows off when the frequency of occurrence of these pockets becomes small.

• OSTI ID: 6538456
• Journal Information: Combust. Flame; (United States), Journal Name: Combust. Flame; (United States) Vol. 74:3; ISSN CBFMA
• Country of Publication: United States
• Language: English

Related Subjects

090110* -- Hydrocarbon Fuels-- Properties-- (1979-1989)
10 SYNTHETIC FUELS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800 -- Combustion
Pyrolysis
&amp; High-Temperature Chemistry
ALKANES
CALCULATION METHODS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
COMBUSTION PROPERTIES
ELEMENTS
ENERGY DENSITY
FLAMES
HYDROCARBONS
HYDROGEN COMPOUNDS
METHANE
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PROBABILISTIC ESTIMATION
TEMPERATURE MEASUREMENT
WATER