- Flat, laminar, premixed hydrocarbon-air flames were stabilized
on a porous-plate burner. In addition to temperature profiles,
concentration profiles were measured for methane, ethane, ethylene,
propane, acetylene, propylene, carbon monoxide, carbon dioxide and
oxides of nitrogen. Dead space thickness, luminous flame zone
thickness and hydrocarbon disappearance point responses were also
monitored. The experimental parameters investigated were hydrocarbon
fuel type: propane and propylene; equivalence ratio: .90 to 1.10; plate temperature: 600°F to 800°F; and sampling position:
.005 to .335 cm.
A completely randomized nonreplicated factorial experiment
was used to statistically detect the presence of main and two-factor
interaction effects. Higher order three and four-factor interaction
terms were pooled as an estimate of the error term. Null and alternative
hypotheses were proposed concerning the presence of main
and two-factor effects. The results of these tests indicate:
1. Stable species hydrocarbons exist in the reaction zone under
all of the conditions investigated. Their concentration is a function
of fuel type, equivalence ratio, sampling position and in some cases
plate temperature. Several significant interaction terms are also
2. Ethylene is the major stable hydrocarbon species for both
propane and propylene as fuels. The quantitative ranking of the
other hydrocarbon species is a function of fuel type, equivalence
ratio, and plate temperature.
3. Dead space thickness is a function of fuel type, equivalence
ratio, and plate temperature but no significant two- factor interaction
terms are present. For each fuel, dead space thickness may be expressed
in the functional form Y = β₀ + β₁X₁ + β₂X₂ + β₃X²₁ + β₄X²₂, where X₁ plate temperature °F. X₂ equivalence ratio. β's constants. 4. Luminous flame zone thickness is a function of fuel type
only. Propylene exhibits a greater flame zone thickness than propane.
5. Hydrocarbon disappearance point is a function of equivalence ratio and plate temperature. Its response may be expressed
in the function form Y = β₀ + β₁X₁ + β₂X²₁ +β3X²₂ where, X₁ plate temperature °F. X₂ equivalence ratio. β's constants. 6. Oxides of nitrogen concentration is a function of fuel type,
equivalence ratio, plate temperature, and sampling position.
Several significant interaction terms are also present. In order to
examine the true fuel structure effect, the predominant covariant
flame temperature effect must be removed.
One-dimensional flame equations were applied to the experimental
data. Sample calculations indicate that the presence of carbon
monoxide and carbon dioxide concentrations at the surface of the
burner cannot be completely attributed to diffusion processes.
Therefore, one must conclude that chemical reaction takes place
within the dead space.