Flamelet-Based Time-Scale Analysis of a High-Pressure Gasifier

摘要

A computational fluid dynamics (CFD) multi-feed stream flamelet model is developed and coupled to a CFD solver to simulate single-phase gas turbulent reactive flow in a gasifier. The flow equations are solved using OpenFOAM, whereas the species mass fractions and the temperatures are taken from tabulated flamelet solutions. The look-up tables were generated for the three-feed stream system of fuel, oxidizer, and steam. The validity of the flamelet model for gasification conditions is investigated in detail using an analysis of the flow and the flamelet time scales. The flamelet time scale includes both mixing and chemical reactions. On the basis of the time scales, three zones can be identified in the gasifier, namely, the (i) flame zone, (li) recirculation zone, and (iii) post-flame or reforming zone. Good agreement is found when comparing the CFD-flamelet simulation results to the experimental values at the outlet The effects of different scalar dissipation rates on the species mass fractions and the outlet temperature are studied, which is shown to have a significant influence on the final results.