Extinction behavior of addition of PMMA powder into counterflow diffusion flame of methane and nitrogen and high temperature air

Abstract

A counter-flow diffusion flame formed of a fuel consisting of methane and nitrogen, and a oxidizer of air heated to 500℃ was applied to clarify the influence on the extinction limit when fine powder of polymethyl methacrylate (PMMA) was added to the fuel. The flame stretch rate at the time of extinguishing flame was measured as function of the powder size and the weight concentration of powder in the fuel. The sizes of PMMA powder used are 15 μm, 30 μm and 50 μm. The weight concentration of PMMA powder in the fuel was changed to 20%, 25% and 30%. The flame stretch rate at the extinction limit for the methane fuel and air was increased with the increase of the air temperature. When the PMMA powder were mixed in the fuel, the flame stretch rate at the extinction limit increased with the larger fuel size, because the larger powders had slip to gas and did not trace on the gas flow. Therefore, the powder stayed longer in the flame. The flame stretch rate at the extinction limit was decreased with the increase of the weight concentration of the PMMA powder, because the combustion of powder needed longer time to that of gas.

Keywords

• plastic powder
• counterflow flame
• stretch rate
• extinction limit
• transfer number
• high-temperature air
• heterogeneous combustion