Efficient low-emission burners for natural gas domestic cooktops

Three new partially-aerated burners have been developed for Australian cook tops fired with natural gas, with maximum thermal inputs of 12, 7.5 and 5.5 MJ h(-1). These novel burner designs minimise the NO2 emission per unit of useful energy, since NO2 is the more toxic nitrogen oxide of concern for i ndoor air pollution. They provide lower values of the ratio of NO2 emission to thermal efficiency than production burners, with respective reductions of 42, 13 and 23% compared with production burners of corresponding size. T he traditional combustion diagrams of these prototype burners have been def ined, on plots of primary aeration Versus thermal input, to identify the re gions of stable flame operation. However, the regions of satisfactory opera tion are further limited at low primary aeration by the Australian Gas Asso ciation requirement for CO/CO2 ratio <0.01 and at low thermal inputs by the requirement for re-ignition after exposure to a standard draught of 5 km h (-1). To achieve the full emission reduction potential of these burners, th e air-gas supply system needs to be re-designed to increase the primary aer ation at the maximum thermal input to similar to 62%, from the similar to 5 0% achieved by production air-gas supply systems. The required turndown of 5:1 can be achieved by these prototype burners, provided the operating curv es of primary air/gas ratio versus thermal input for the re-designed air/ga s systems lie within the regions of stable and satisfactory flame operation defined on the combustion diagrams.