Fractals and turbulent premixed engine flames
- Princeton Univ., NJ (USA). Dept. of Mechanical and Aerospace Engineering
The fractal nature of premixed turbulent flames in an internal combustion engine is examined. A sheet of laser light, approximately 200{mu}m thick is shone through the cylinder of a single-cylinder ported internal combustion engine. The homogeneous charge of propane and air is seeded with submicron TiO/sub 2/ particles and the scattered light is collected through a quartz window in the engine head and is imaged on a 100 x 100 diode array camera. The number density of the TiO/sub 2/ particles scales with the gas density so that a two-dimensional map of reactants and products is obtained. A field of view 2 x 2 cm in the center of the cylinder is examined and fractal analysis is performed on the front separating reactants from products. Results are presented for two equivalence ratios and three engine speeds, corresponding to different laminar flame speeds S/sub 1/, laminar flame thickness {delta}/sub 1/, turbulent intensities {mu}', and Kolmogorov scales eta. The examined flames were found to exhibit fractal character within a range of length scales as low as 200 {mu}m and as high as 4.5 mm, which is twice the measured lateral integral length scale in this engine configuration. At stoichiometric conditions, the fractal dimension of the flame surface is found to be statistically different for engine speeds of 300, 1200, and 2400 rpm ({mu}'/S/sub 1/=0.5, 2, and 4). It increases with increasing {mu}'/S/sub 1/. At lean conditions (phi=0.59), when {mu}'/S/sub 1/>>1, the fractal dimension does not change with engine speed. The 4 {le} {mu}'/Si/sub 1/<50 and 0.1
- OSTI ID:
- 5521760
- Journal Information:
- Combustion and Flame; (USA), Journal Name: Combustion and Flame; (USA) Vol. 77:3; ISSN 0010-2180; ISSN CBFMA
- Country of Publication:
- United States
- Language:
- English
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10 SYNTHETIC FUELS
33 ADVANCED PROPULSION SYSTEMS
330100 -- Internal Combustion Engines
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
42 ENGINEERING
420400 -- Engineering-- Heat Transfer & Fluid Flow
ALKANES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
COMBUSTION KINETICS
ENGINES
FLAMES
FLUID FLOW
HEAT ENGINES
HYDROCARBONS
INTERNAL COMBUSTION ENGINES
KINETICS
LAMINAR FLOW
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROPANE
REACTION KINETICS
STOICHIOMETRY
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TURBULENT FLOW
TWO-DIMENSIONAL CALCULATIONS