Simulating Dust Explosions with the First Version of DESC

Abstract

This dissertation describes the development and validation of a methodology for estimating the consequences of accidental dust explosions in complex geometries. The approach adopted entails the use of results from standardized tests in 20-litre explosion vessels as input to the combustion model in a computational fluid dynamics (CFD) code, and the subsequent validation of the model system by comparing with results from laboratory and large-scale experiments. The PhD project includes dedicated laboratory experiments designed to explore selected aspects of flame propagation in dust clouds, and to reveal similarities and differences between flame propagation in gaseous mixtures and mechanical suspensions of combustible powder in air. v Scientific environment The philosophiae doctor (PhD) project started in January 2004. The work progressed under the principal supervision of Professor Rolf K.

Accurate analytical models for fractional pressure rise in constant volume combustion

“…A linear x(p) relation, first introduced in their famous text book [1], is still used a lot in evaluating laminar burning velocities [4][5][6][7][8][9].…”

“…Senecal and Beaulieu [6] use the same model as Dahoe et al in order to obtain new values for the explosion constant K G (see Section 4.3) for several gases. In recent years, also Skjold et al [7], Frijters et al [8] and again Dahoe [9] have employed the linear relation (2) to derive burning velocities.…”

Determination of the maximum effective burning velocity of dust–air mixtures in constant volume combustion

“…It is not straightforward to unambiguously define an average velocity in a transient flow field, and hence to obtain well-defined values for the root-mean-square of the turbulent velocity fluctuations (Dahoe, Cant et al, 2001;Dahoe, van der Nat et al, 2001;Skjold, 2003), and certain assumptions must be invoked in order to extract decay laws for the turbulent integral length scale from such measurements (Dahoe, van (Pu et al, 1990); (b) in two cylindrical vessels, 7 and 22 l (Yan & Pu, 1999). performed with a very limited amount of dust in the system, and the influence of the presence of dust particles on the flow is usually unknown (Dahoe, van der Nat et al, 2001;Skjold, 2003). Finally, by using the level of turbulence at time of ignition as a reference, any decay of turbulence during the period from t ig to t* is neglected; an alternative approach involves using the level of turbulence at the inflection point as reference, hence neglecting any turbulence induced by combustion during the same period (Skjold, 2006;Skjold et al, 2005Skjold et al, , 2006.…”

“…The concept of maximum effective burning velocity was suggested by Pu et al (1990), and a similar approach has recently been adopted for analyzing results from 20-l explosion vessels as input to the CFD-code DESC (Skjold, 2006;Skjold, Arntzen, Hansen, Storvik, & Eckhoff, 2006;Skjold et al, 2005). The main purpose of the present study is to investigate practical procedures for determining u eff,max from measured pressure-time histories in closed combustion vessels, and to compare results obtained in different explosion vessels.…”

Impact of dissociation and end pressure on determination of laminar burning velocities in constant volume combustion

“…As a consequence, there are still many authors who prefer the simplicity and ease-of-use of the linear relation (2), as witnessed by a number of recent publications [8][9][10][11][12][13]. Obviously, such analytical approaches have clear advantages.…”