Experimental study of the effect of ullage height on flame characteristics of pool fires

Abstract

A series of experiments were carried out to investigate the effect of ullage height, i.e. the distance between fuel surface and the pool upper rim, on flame characteristics of heptane and ethanol pool fires. The pool diameters included 10 cm, 15 cm, and 20 cm. For each pool, ullage height was increased from zero to the value that the flame self-extinguished. During each test, the ullage height was kept constant by a fuel level maintaining device. Results show that ullage height has a significant effect on flame characteristics. When the ullage height equals zero, there is a stable conical structure near the pool upper rim, above which the unstable plume develops. Under lower ullage height conditions, plume puffing happens. The unstable plume begins to initiate around the pool upper rim, then rolling and expanding upward. At the same time, its beneath flame is stretched thinner and thinner and eventually breaks from the bulk. When the ullage height further increases, plume puffing becomes less evident. While for the mass loss rate, it generally decreases with the increase of h/D. It was proved in literature that the previous flame height model is inapplicable to pool fires with large ullage height. In this paper, to consider the effect of ullage height on plume flow structures, an equivalent hydraulic diameter, D eq. , is proposed to establish one new flame height correlation. By comparing previous model predictions with the current experimental data, it is found that conventional flame oscillation models are unsuitable to pool fires with large ullage height. Based on D eq. , two new dimensional and dimensionless flame oscillation models were proposed according to the current experimental data. The correlated flame height model and proposed flame oscillation models were validated and agreed well with reference data.

Experimental study and thermal hazard analysis of large-scale n-heptane pool fires under sub-atmospheric pressure

“…For the experiments with the circular pans, a load cell (Sartorius: maximum: 35 kg, precision: 0.1 g,) was used to record the real time mass loss of the fuel, based on which the burning rate was calculated. For the experiment with the square pan, the principle of the connector was used (Liu et al, 2020) to calculate the burning rate by measuring the mass of a small container connected to the large fuel pan, and the detail layout is shown in Fig. 1 (b).…”

Experiments and modeling of the temperature profile of turbulent diffusion flames with large ullage heights

“…In recent years, several major fire accidents involving storage tanks occurred, particularly for the tanks with a low liquid level (large ullage height) [3]. Once the fuel is ignited, the flame base will move up due to restriction of air entrainment by the sidewall, resulting in a significant change of the flame temperature profile [4], which in turn can affect the evolution of the fire accident and determine the likelihood of fire escalation. On April 6, 2015, a major fire accident involving a liquid fuel storage tank occurred in Fujian, China [5].…”

Effects of ullage height on heat feedback and combustion emission mechanisms of heptane pool fires

“…They found out that the flame initially anchored around the pool rim under small ullage height conditions, and then it partially covered the burner due to the plume axial flapping as the ullage height grew large. Liu et al [15][16][17] conducted experimental and numerical studies focusing on the effects of ullage height on the flame characteristics, plume centerline temperature, and plume flow and combustion characteristics.…”