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Experimental studies are conducted on extinction of non-premixed dimethyl ether (DME) flames stabilized in the counterflow configuration. Studies are carried out by injecting a fuel stream made up of fuel and inert gas (N2 or CO2) from one duct and an oxidizer stream made up of O2 and inert gas (N2 or CO2) from the other duct. Critical conditions of extinction are measured by increasing the flow rate of the counterflowing streams until the flame extinguishes. Numerical studies are also performed using detailed chemistry at conditions corresponding to those used in the experiments and compared with measurements. The present study highlights the examination of the influence of flame temperature, flame structure and kind of inert gas on extinction properties of DME. To examine the effect of flame temperature, inert gas is introducing to both fuel and oxidizer sides in such a way that the stoichiometric mixture fraction, Zst, is not changed, which means flame structure is not changed.

In combustion engines, turbulence generated by flow field motion in the cylinder affects the propagating flame initiated by a spark plug, resulting in the increase of heat release rate and thus power available from an engine of a given size. In this context the modeling and prediction of turbulent flame properties are of importance for smart control of engine performance. In the present work, turbulent burning velocities of outwardly propagating premixed flames for methane and propane are investigated under the framework of the flamelet concept. The primary objective of the present paper is to study experimentally the turbulent burning velocities and derive the fundamental equations.

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 NOx reduction and the improvement of combustion. Both experimental and numerical studies are conducted to scrutinize the effects of flame stretch on the burning velocity, which plays an important role in combustion performance not only for laminar flames but also for turbulent flames. In this study, experiments are conducted by using a spherical combustion bomb for applications to internal combustion engines. Then the effects of flame stretch are also investigated numerically and quantitative discussion is made in terms of Markstein number which represents non-dimensional sensitivity of the burning velocity to flame stretch. As a result it is found that Markstein numbers for both methane mixtures decrease with decreasing equivalence ratio.