Mixing and reaction in a tubular jet reactor: A comparison of experiments with a model based on a prescribed PDF

Large-eddy simulation and laser diagnostic measurements of mixing in a coaxial jet mixer

“…These investigations had been motivated by two following problems: the stabilization of the flame front and the saturation of air co-flow with the molecules of substances transferred by the internal jet. Investigations of jet mixers with emphasis on the jet mixer as a chemical reactor are presented in Guiraud et al (1991), Kruis and Falk (1996) and Baldyga and Bourne (1999). Unlike the papers mentioned above we investigate fully developed turbulent flows of the jet mixer both in the r-mode and in the j-mode.…”

Approximation of joint PDFs by discrete distributions generated with Monte Carlo methods

“…For example, it is often claimed that the β-PDF is suitable for the approximation of mixture fraction PDFs in mixing processes. In this case, the mixture fraction PDF would indeed be well characterized by its first two moments P( f ) ≈ P (2) ( f ;f , f 2 ). However, our results indicated that this is not always the case -we shall elaborate on this point below.…”

“…The factor ν i is computed as the difference of the stoichiometric coefficients of species i at the reactant ν i and product side ν i , respectively. Equation (2) shows that reaction rates depend in a non-linear fashion on temperature T and concentrations, making it a difficult task to determine mean reaction rates, since they cannot be computed from mean values of temperature and concentrations. In general mean values of an arbitrary variable or function g (e.g.…”

“…In general mean values of an arbitrary variable or function g (e.g. the formation rate) can be computed by convolution over a probability density function (PDF) P: In principle the PDF can be solved with ordinary partial differential equation solvers, but since those are not suited for solving high dimensional equations, two different methods are common, namely the approximation by presumed PDFs [2][3][4][5] or by transported discrete PDFs [6][7][8]. The latter approach makes use of Monte Carlo methods to transport particles through the computational domain and offers the significant advantage that the chemical source term in equation (1) can be closed directly.…”

“…For many technical applications in combustion [1] as well as process engineering [2] turbulent flow conditions are prevalent. The flow in this regime is characterized by large mixing rates, which make possible high reaction densities and therefore smaller combustors or chemical reactors.…”