Modeling Lifted Methane Jet Fires Using the Boundary-Layer Equations

Abstract

The focus of this paper is turbulent lifted jet fires. The main objective is to present a lifted jet fire methodology using the boundary layer equations as a basis. The advantages of this are finite volume mesh independent predictions of the mean flow fields can be calculated on readily available computer resources which leads to rigorous model calibration. A number of lift-off models are evaluated. The model of choice is one based on the laminar flamelet quenching concept combined with a model for the large-scale strain rate.

A computational flame length methodology for propane jet fires

“…Sanders and Lamers based on an isothermal jet calibration concluded the small-scale strain rate model to be the superior of the two with respect to predicting the lift-off heights in methane jet fires; however in a recent paper Cumber and Spearpoint, [32] demonstrated that the largescale strain rate model gave a better calibration against Wittmer's lift-off measurements, [33] the data used by Sanders and Lamers. Further studies not reported here, comparing Kalghatgi's liftoff height measurements [6] with the predicted lift-off height using the two strain rate models, for a range of methane and propane jet fires further confirmed the superiority of the large-scale strain rate model.…”

Modelling lifted hydrogen jet fires using the boundary layer equations

“…The issue of robust calibration is a particularly important one as without it, model development looses rigour. Cumber and Spearpoint (2006) showed that Sanders and Lamers (1994) adoption of the small-scale strain rate model for lifted methane jet fires was incorrect as the large scale strain rate model gave far closer agreement with observed lift-off heights once both models were calibrated appropriately. In the next section the mathematical model is presented.…”

“…A wide range of small-scale, Kalghati (1984) and Pitts (1989) and large-scale experimental studies of lifted fires, Birch and Hargreave (1988) exist in the open literature. There are also a number of theoretical studies, Sanders and Lamers (1994), Cumber and Spearpoint (2006) being examples.…”

“…In this paper a model originally proposed by Sanders and Lamers (1994) and modified by Cumber and Spearpoint (2006) based on the laminar flamelet quenching concept is extended to predict lifted hydrogen jet fires. The original model was applied to lifted methane jet fires, Cumber and Spearpoint (2006) demonstrating that for lifted methane jet fires the large scale strain rate, the eddy strain rate was the important parameter in determining the lift-off height rather than the strain rate at the smaller scales nearer the molecular scale.…”

“…The original model was applied to lifted methane jet fires, Cumber and Spearpoint (2006) demonstrating that for lifted methane jet fires the large scale strain rate, the eddy strain rate was the important parameter in determining the lift-off height rather than the strain rate at the smaller scales nearer the molecular scale. The lifted jet fire methodology presented in Cumber and Spearpoint (2006) is based on a parabolic flow model and as such the use of laminar flamelet quenching is a convenient lift-off model. The methodology presented with minor modification could be implemented with other lift-off models.…”