Closed vessel combustion modelling by using pressure-time evolution function derived from two-zonal approach

Abstract

In this paper a new method for burned mass fraction - pressure relation, x-p relation, for two-zone model combustion calculation is developed. The main application of the two-zone model is obtaining laminar burning velocity, SL, by using a pressure history from a closed vessel combustion experiment. The linear x-p relation by Lewis and Von Elbe is still widely used. For linear x-p relation, the end pressure is necessary as input data for the description of the combustion process. In this paper a new x-p relation is presented on the basis of mass and energy conservation during the combustion. In order to correctly represent pressure evolution, the model proposed in this paper needs several input parameters. They were obtained from different sources, like the PREMIX software (with GRIMECH 3.0 mechanism) and GASEQ software, as well as thermodynamic tables. The error analysis is presented in regard to the input parameters. The proposed model is validated against the experiment by Dahoe and Goey, and compared with linear x-p relation from Lewis and Von Elbe. The proposed two zone model shows sufficient accuracy when describing the combustion process in a closed vessel without knowing the end pressure in advance, i.e. both peak pressure and combustion rates can be sufficiently correctly captured

Characterization of critical stretch rate using outwardly propagating spherical flames

“…This is understandable given the small, highly stretched flame kernel, surrounded by cold unburned reactant. Heat release from the spark must be sufficient to raise the thermal conduction in proportion to reactant mass diffusion, and generate enough heat to enable the flame to be- Lean CH /air mixtures 4 Rich CH /air mixtures 4 Lean C H /air mixtures 3 8 Lean CH OH/air mixtures 3 Lean C H OH/air mixtures 2 5 Accuracy come self-propagating. Taking this to the limit, region A would not exist, with flame growth starting at the origin as determined by non-linear extrapolation equation, fig.…”

“…Operational issues resulting from fuel variability and combustor flexibility necessitate detailed research in the fundamental aspects of combustion control [1][2][3]. The study of extinction stretch rates, K ext , is key for the reduction of pollutants formed from turbulent flames, prevailing within power or propulsion systems, and preventing extinction by stretch [4,5].…”

“…The aim of this work is to appraise the hypothesis that α Cr is quantitatively equivalent to K ext as quoted in the literature for counter-flow burners [16] proposed critical radius as the radius above which an ignition kernel can lead to a successful ignition. This work thus presents analysis and discussion of experiments undertaken with four fuels (two gaseous, and two pre-vaporised liquids) namely methane, propane, methanol, and ethanol (CH 4 , C 3 H 8 , CH 3 OH, and C 2 H 5 OH), with measured values of α Cr benchmarked against corresponding published values of K ext derived using the counter-flow technique. It is worthy to note that the same analysis followed in the present work can be applied also to biodiesel and biogas, among others, fuels commonly used in internal combustion engines [17][18][19].…”