Effects of dilution with CO2 on Stretched Premixed Laminar Methane Flames

Abstract

The purpose of this paper is to investigate the combustion properties of CH4/O2 mixtures diluted by CO2 compared to those of CH4/O2/N2 mixtures to study the feasibility of the new combustion method, which is expected to be effective in the NOx reduction and the improvement of combustion. Both experimental and numerical studies were conducted to scrutinize the effects of flame stretch on the burning velocity and the effects of flame instability which may play an important role in combustion performance not only for laminar flames but also for turbulent flames. In this study, experiments were conducted by using spherical combustion bomb for applications to internal combustion engines. First the effect of flame stretch was investigated experimentally and numerically and quantitative discussion was made in terms of Markstein number which means not-dimensional sensitivity of the burning velocity to flame stretch. As a result it has been found that Markstein numbers for both methane mixtures decrease with decreasing equivalence ratio. In addition CH4/O2/ CO2 mixtures have the low values of Markstein number compared with CH4/O2/N2 mixtures over the whole equivalence ratio.