Investigation of Mixing Models and Finite Volume Conditional Moment Closure Applied to Autoignition of Hydrogen Jets
Title | Investigation of Mixing Models and Finite Volume Conditional Moment Closure Applied to Autoignition of Hydrogen Jets PDF eBook |
Author | Andrew Buckrell |
Publisher | |
Pages | 164 |
Release | 2012 |
Genre | |
ISBN |
In the present work, the processes of steady combustion and autoignition of hydrogen are investigated using the Conditional Moment Closure (CMC) model with a Reynolds Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) code. A study of the effects on the flowfield of changing turbulence model constants, specifically the turbulent Schmidt number, Sct, and C epsilon 1 of the k - epsilon model, are investigated.
Investigation of an Inhomogeneous Mixing Model for Conditional Moment Closure Applied to Autoignition
Title | Investigation of an Inhomogeneous Mixing Model for Conditional Moment Closure Applied to Autoignition PDF eBook |
Author | Adrian Milford |
Publisher | |
Pages | 129 |
Release | 2010 |
Genre | |
ISBN |
Autoignition of high pressure methane jets at engine relveant conditions within a shock tube is investigated using Conditional Moment Closure (CMC). The impact of two commonly used approximations applied in previous work is examined, the assumption of homogeneous turbulence in the closure of the micro-mixing term and the assumption of negligible radial variation of terms within the CMC equations. In the present work two formulations of an inhomogeneous mixing model are implemented, both utilizing the [beta] -PDF, but differing in the respective conditional velocity closure that is applied. The common linear model for conditional velocity is considered, in addition to the gradient diffusion model. The validity of cross-stream averaging the CMC equations is examined by comparing results from two-dimensional (axial and radial) solution of the CMC equations with cross-stream averaged results. The CMC equations are presented and all terms requiring closure are discussed. So- lution of the CMC equations is decoupled from the flow field solution using the frozen mixing assumption. Detailed chemical kinetics are implemented. The CMC equations are discretized using finite differences and solved using a fractional step method. To maintain consistency between the mixing model and the mixture fraction variance equation, the scalar dissipation rate from both implementations of the inhomogeneous model are scaled. The autoignition results for five air temperatures are compared with results obtained using homogeneous mixing models and experimental data. The gradient diffusion conditional velocity model is shown to produce diverging be- haviour in low probability regions. The corresponding profiles of conditional scalar dis- sipation rate are negatively impacted with the use of the gradient model, as unphysical behaviour at lean mixtures within the core of the fuel jet is observed. The predictions of ignition delay and location from the Inhomogeneous-Linear model are very close to the homogeneous mixing model results. The Inhomogeneous-Gradient model yields longer ignition delays and ignition locations further downstream. This is influenced by the higher scalar dissipation rates at lean mixtures resulting from the divergent behaviour of the gradient conditional velocity model. The ignition delays obtained by solving the CMC equations in two dimensions are in excellent agreement with the cross-stream averaged values, but the ignition locations are predicted closer to the injector.
Applied Mechanics Reviews
Title | Applied Mechanics Reviews PDF eBook |
Author | |
Publisher | |
Pages | 724 |
Release | 1996 |
Genre | Mechanics, Applied |
ISBN |
MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools
Title | MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools PDF eBook |
Author | Alessandro Parente |
Publisher | Frontiers Media SA |
Pages | 160 |
Release | 2021-11-26 |
Genre | Technology & Engineering |
ISBN | 2889717003 |
Mixing of Hydrogen Injected from Multiple Injectors Normal to a Supersonic Airstream
Title | Mixing of Hydrogen Injected from Multiple Injectors Normal to a Supersonic Airstream PDF eBook |
Author | R. Clayton Rogers |
Publisher | |
Pages | 42 |
Release | 1971 |
Genre | Aerodynamics, Supersonic |
ISBN |
A Study of Reacting Free and Ducted Hydrogen/air Jets
Title | A Study of Reacting Free and Ducted Hydrogen/air Jets PDF eBook |
Author | |
Publisher | |
Pages | 50 |
Release | 1975 |
Genre | |
ISBN |
A-priori of Conditional Moment Closure Modeling of a Temporal Ethylene Jet Flame with Soot Formation Using Direct Numerical Simulation
Title | A-priori of Conditional Moment Closure Modeling of a Temporal Ethylene Jet Flame with Soot Formation Using Direct Numerical Simulation PDF eBook |
Author | |
Publisher | |
Pages | 9 |
Release | 2007 |
Genre | |
ISBN |