Development of an Air/Fuel Premixer for a Gas-Fueled Two-Layer Porous Media Burner

Abstract

ABSTRACT Air-fuel premixers are integrated parts of the premixed burner systems. The present paper describes the modeling, design optimization, and testing of an air-fuel premixer for a 5 kW natural gas porous media burner. The design was aimed at decreasing NOx and CO emissions by forming a homogeneous mixture of air and fuel. The design parameters were optimized employing CFD analysis coupled with a design of experiments (DOE) method. Then, a test model, based on the optimized design, was built and installed in a porous media burner testing apparatus. The test results have shown that the new premixer successfully reduced NOx emissions. It also improved flame stability by preventing flashback in several cases which revealed a new flashback mechanism in such burners. This improvement is achieved by preventing locally near-stoichiometric zones with high flame speeds from being formed. The effect of the new premixer on CO emissions was shown to depend on the firing rate and equivalence ratio. While reduced CO emissions are achieved at high firing rates and equivalence ratios, the level of CO emissions is increased for low firing rate and equivalence ratio magnitudes.