Combustion-Driven Oscillations in Residential Gas Appliances with Ceramic Surface Burners

Modern residential gas appliances are often equipped with fully premixed ceramic surface burners to minimize nitrogen oxide and carbon monoxide emissions. The combustion process is characterized by short flat flames, which may be described as a one-dimensional combustion zone. Unlike a combustion system featuring long diffusion flames, such a system is unable to attenuate accidental pressure disturbances which may therefore result in undesired oscillations. These oscillations increase NOx, CO and noise emissions. In spite of substantial experimental and theoretical research, it is still not possible to predict this thermo acoustic behavior when new gas appliances are developed. Gaswaerme-lnstitut e.V. (GWI) has installed an advanced fast-response measurement system to carry out research intended to provide a better understanding of the mechanism underlying combustion-driven oscillations. Main data used to analyze the thermo acoustic behavior of gas appliances include the pressure in the combustion chamber, the heat release rate and the fuel flow rate. The detailed analysis of these data with respect to frequency and time produces the information required to determine the important parameters which influence oscillations. The experimental and theoretical work of GWI enabled the solution of thermo acoustic problems associated with a specific gas appliance and the elimination of combustion-driven oscillations. (author)