Experimental Study on Microwave-Induced Plasma-Assisted Premixed Methane-Air Combustion

Microwave-induced plasmas (MIPs) are used in various fields where the effect of high-energy electrons is needed. In the case of plasma-assisted combustion (PAC), a range of combustion properties are significantly affected by the introduced and absorbed microwave power. MIPs are well-studied in the case of mono-component gases, but less knowledge is available regarding the effect of introduced microwave power on multicomponent gases, like in the case of combustion. Previous research has primarily relied on the effect of introduced microwave power on the flammability limits and the flame speed enhancement during fuel-lean conditions, but less knowledge is available on the effect of introduced microwave power on the flue gas components. Here, we report a quantitative analysis of dry flue gas of premixed methane (CH4)-air flame coupled with 2.45-GHz microwave power using a self-designed mono-mode plasma cavity. A rapid increase in NOx concentration in the flue gas was found by the formation of plasma. The carbon dioxide concentration in the dry flue gas is found to decrease with the applied microwave power to the premixed CH4-air flame, while the oxygen concentration increases, which can be originated from the flame temperature increase. This is also supported by the rotational temperature calculations of OH radicals, which are based on the flame’s spectral emissivity measurements.