Combustion dynamics and thermal structure of a planar spray flame
An experimental exploration of the dynamic nature of the burning phenomenon and of the thermal structure of a planar spray flame has been performed. Initially, the influence of important spray parameters on the flame front motion has been investigated. Subsequently, the performance of micro-thermocouples for the measurement of gas-phase temperature in the presence of droplets has been studied as a means to analyze the thermal structure of the planar spray flame. Finally, the influence of important spray parameters on the thermal structure of the flame was investigated. Higher fuel vapor concentrations, smaller droplet sizes, or more volatile fuels caused the average flame speed to increase while reducing the flame speed fluctuations and the intermittent combustion zone. In contrast, the presence of higher gas phase turbulence intensity caused the average flame speed to increase while also increasing the flame speed fluctuations and the intermittent combustion zone. Some of the observed phenomena has been qualitatively explained through the ignition mechanism in the spray. A spray flame with a premixed-gas flame ignition mechanism presents less flame speed fluctuations and a smaller intermittent combustion zone than a spray flame with a relay ignition mechanism. A threshold temperature of 350/sup 0/C was found when investigating the performance of micro-thermocouples in the presence of hexane droplets in a dilute spray flame. Above 350/sup 0/C, the droplets impinging the microthermocouple bead did not affect the measurements of average temperature and of temperature fluctuations in the gas phase. A change in the heat transfer mechanism, from nucleate boiling to film boiling was the explanation proposed for the existence of the threshold temperature. The hexane droplet size did not seem to affect the threshold temperature value.
- Research Organization:
- Carnegie-Mellon Inst. of Research, Pittsburgh, PA (USA)
- OSTI ID:
- 6710871
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
ALKANES
CHEMICAL REACTION KINETICS
COMBUSTION KINETICS
CRYSTAL STRUCTURE
DROPLETS
ENERGY TRANSFER
FLAMES
FLUIDS
FUELS
GASES
HEAT TRANSFER
HEXANE
HYDROCARBONS
IGNITION
KINETICS
MATTER
MICROSTRUCTURE
ORGANIC COMPOUNDS
PARTICLES
REACTION KINETICS
SPRAYS
TEMPERATURE DISTRIBUTION
TEMPERATURE MEASUREMENT
TURBULENCE
VOLATILE MATTER