A computational flame length methodology for propane jet fires

Abstract

This paper presents a flame length methodology that mimics the human eye or camera using a CFD framework to calculate the flame structure. A parabolic flow model which accounts for turbulent combustion, soot kinetics and visible radiation distribution is extended to predict both rim-stabilised and lifted jet fires. The model is calibrated using a selected set of jet fire experiments and then validated against a wider range of data. Good agreement over a range of scales is demonstrated particularly when taking the degree of repeatability of the experiments into account. The flame length prediction is found to be insensitive to receiver location so long as the receiver is one or more flame lengths from the fire.

Experimental study on propane jet fire hazards: Assessment of the main geometrical features of horizontal jet flames

“…A temperature contour from IR images can also be used as a flame boundary. Cumber determined that the visible boundary is equivalent to a heat flux of 40 W/m2 (Cumber and Spearpoint, 2006), Upatnieks a temperature contour of 600 K (Upatnieks et al, 2004), and Palacios 800 K (Palacios and Casal, 2011). In this study, both IR and CCD camera were used to visualize the jet fires, similar to Palacios (Palacios and Casal, 2011).…”

Measuring Radiation Heat Fluxes from a Jet Fire Using a Lumped Capacitance Model

“…The dimensionless group for determining the importance of source momentum compared to buoyancy effects is the Froude number, where U 0 is the source velocity, D is the burner diameter and g is the acceleration due to gravity. Cumber and Spearpoint [5] stated that a Froude number of 5,000 or more was required to predict the flame length of a propane jet fire using the computational model described above. The Froude number for the low speed jet fire is…”

“…This scenario is a primary motivation for research into experimental techniques for characterising the flame structure [1] and radiation fields of jet fires [2,3]. There has also been a great deal of research undertaken to develop mathematical models of jet fires with a view to ultimately producing software tools for consequence assessment and safety analysis of high pressure plant [4][5][6]. These mathematical models are rigorously validated using experimental measurements such that appropriate confidence can be placed on their predictive capability.…”

“…The optically thin approximation is valid for laboratory scale methane jets. This approach has been used successfully in other computational studies [4,5,21]. Physical properties such as the specific heat capacity at constant pressure are evaluated from curve fits in temperature to JANNAF thermodynamic property tables [22].…”

Accelerating ray convergence in incident heat flux calculations using Sobol sequences

“…To account for radiation heat loss a transport equation for a specific enthalpy perturbation is solved, where radiation heat loss is introduced using the optically thin approximation [16]. This approach is more sophisticated than accounting for the radiative heat loss by adjusting the temperature flamelet and has been used successfully in other computational studies [6,31,36]. The incident heat flux calculations and the flame structure model are uncoupled.…”