Scaling criteria for the development of an acoustically stabilized dump combustor

Acoustic stabilization of combustion in a dump configuration results in completion of combustion in a relatively short residence time with simultaneously low emissions of oxides of nitrogen, carbou monoxide. and hydrocarbons. Acoustically stabilized combustion is also a potential means for achieving closed-loop active control of combustion. Therefore, a promising burner configuration identified through laboratory bench-top experiments was developed and scaled up for application as an afterburner for a starved-air incinerator with the objective of providing a compact device capable of achieving pollutant emissions performance better than required by current International Maritime Organization regulations. In the absence of established scaling criteria, factors governing vortex generation and jet mixing theory were examined. These provided useful guidelines for burner design as the dump combustor was successively scaled up from a 4.75 kW laboratory experiment to a nominal 700 kW unit tested on a starved-air incinerator Key parameters considered were the central air jet velocity, jet diameter (and area) acoustic driving frequency, and characteristic jet mixing time. Burner performance was maintained or improved as both jet velocity and jet area were increased approximately as the square root of burner scale. This resulted in increased in the acoustic driving frequency and bumps pressure drop with scale, which have implications for development of even larger burners using this technology. Initial development was contucted using simulated low-Btu gas mixtures at ambient temperature. Application as an afterburner required hardware modifications to accommodate higher gas volumes at higher temperatures. Despite significant changes in burner geometry, coherent vortex generation was established by acoustic excitation and contained to effect reductions in NOx and CO emissions. The higher combustion temperatures encountered with hot simulated and real pyrolysis products led to, higher CO and NOx emissions, but emission performance continued to exceed applicable regulatory guidelines by a substantial margin.