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Simultaneous Optical Measurement of Soot Volume Fraction and Temperature in Heptane Pool Fires.


pdf icon Simultaneous Optical Measurement of Soot Volume Fraction and Temperature in Heptane Pool Fires. (305 K)
Choi, M. Y.; Hamins, A.; Rushmeier, H.; Hubbard, A.; Kashiwagi, T.

Combustion Institute/Eastern States Section. Technical Meeting, 1993 October 25-27, 1993, Princeton, NJ, 366-369 pp, 1993.

Keywords:

soot; optical measurement; volume fraction; temperature; heptanes; pool fires; heat flux

Abstract:

In large pool fires radiative heat transfer governs the burning and flame spread rates and therefore is a key factor in assessing potential fire hazards. The radiative heat feedback from the flame to the fuel surface is controlled by the temperature and soot distribution inside the fire. Early attempts at modeling this process involved several assumptions including the use of average flame emissivity, constant flame temperatures, absorption/emission cofficients as a function of height and effective flame shapes. Due to the turbulent nature of these fires, the use of mean radiative properties can lead to significant differences between the predicted and measured fuel burning rates. Markstein investigated spatial and temporal variations of the emission intensity for pool fires and suggested the importance of turbulent fluctuations of temperatures and soot volume fractions on the heat transfer mechanism. Direct integration of the turbulent radiative heat transfer to the fuel surface requires the time-varying local temperature and emissivity distributions within the region between the fuel surface and the flame. The primary motivation for this study is to understand the mechanisms governing the gasification and heat feedback rates to the fuel surface. The 3-line emission/absorption technique was used to measure the temperature and soot volume fractions in pool fires burning heptane. The temporal and spatial results will be used to determine the radiative feedback to the surface and the burning rate using a reverse Monte Carlo method for comparisons with the measured values.