Experimental and numerical assessment of the effects of hydrogen admixtures on premixed methane-oxygen flames

Abstract

Thermal utilization of hydrogen is becoming increasingly important as the climate change progresses. Fossil fuels such as natural gas are replaced by green hydrogen in the natural gas grid to reduce CO2 emissions. However, the switch to hydrogen causes significant changes in combustion properties, such as higher flame temperatures or higher burning velocities. As a result, this change in flame properties impacts application processes. In order to prevent a reduction in quality, the processes must be optimally adapted to the fuel switch. Therefore, the combustion properties of the gas mixture have to be investigated in more detail.In this work a premixed oxy-fuel combustion of hydrogen-methane mixtures under atmospheric conditions has been investigated. Therefore, two scenarios are of further interest, low hydrogen admixture (0 vol-%, 10 vol-%, 20 vol-%, and 35 vol-%) and high hydrogen admixture (50 vol-%, 75 vol-%, 95 vol-%/100 vol-%). In this study, a premixed burner is utilized at three different burner powers with a maximum power of 1.2 kW. The flame characteristics has been analyzed by optical (chemilumicence and OH-PLIF), spectroscopic, and thermal measurements. This study aims to determine the change in flame shape, the temperature profiles at different flame heights, and the species formed in the combustion zone. For this purpose, various compositions of hydrogen-methane-oxygen mixtures at different equivalence ratios ϕ=0.8–1.2 are experimentally investigated at atmospheric conditions. The effect of hydrogen addition to the methane-oxygen flame has been numerically considered utilizing three different mechanisms (GRI 3.0, Glarborg, and Aramco). The adiabatic flame temperature, laminar burning velocity and radical formation have been studied numerically for different gas compositions.