Assessment of Combustion and Emission Characteristics of Various Gas Mixtures under Different Combustion Techniques

Abstract

In this study, flame characteristics of 50%CO–50%H2, 80%CH4–10%C2H6–10%N2 and 40%CO–40%H2–20%CO2 blends under different combustion techniques, namely; oxy-fuel combustion, flameless distributed combustion and oxy-flameless distributed combustion, were investigated using ANSYS Fluent CFD code. Such combustion techniques were employed through substituting combustion air with high O2 content (above 21%) O2/CO2 mixture, low O2 content (below 21%) O2/CO2 mixture, and diluting combustion air with 90% N2/10% CO2 mixture to simulate controlled involvement of post combustion gases, respectively. Initially, 2D axisymmetric model of an experimentally tested combustor were utilized to model CH4/air combustion so as to validate applicability of the numerical tool. Later on, premixed combustion of 50%CO–50%H2, 80%CH4–10%C2H6–10%N2 and 40%CO–40%H2–20%CO2 mixtures were simulated at 2 kW thermal load, 0.8 equivalence ratio and 1.0 swirl number to evaluate effects of oxidizing atmosphere on combustion and emission characteristics, and to determine gas composition dependence of studied combustion techniques. Main findings of this study are: regardless of the gas composition and oxidizing atmosphere; temperature, reaction rate and species profiles are similar in trend by indicating gas composition versatility of studied combustion regimes; positive impacts of increased turbulent mixing with O2 dilution dominates reaction rates at and near burner outlet, however O2 enrichment effects overwhelm further downstream.

Keywords

• flameless distributed combustion,oxy-fuel combustion,oxy-flameless distributed combustion

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