Experimental Evaluation of Combustor Configuration's Impact on a Swirl-Assisted Jet-Stabilized Combustor Performance

Abstract

A major challenge for gas turbine combustor technology is the emission of NOx and carbon monoxide (CO). Achieving an optimal premixed, prevaporized, dry low-NOx condition is a critical issue for liquid fuel combustors. To accomplish this, the relationship between combustor configuration and the performance of a newly developed swirl-assisted jet-stabilized combustor is investigated in an atmospheric combustion facility. The combustor consists of a pressure-swirl fuel atomizer, a prefilmer/mixing channel, an axial moderate swirler (swirl number = 0.6), and a jet nozzle. The jet nozzle allowed for bulk velocities of 50–130 m/s. The influence of each combustor component on combustion performance and fuel evaporation behavior is evaluated independently using optical combustion diagnostics. In addition, the effect of air and liquid fuel temperature on fuel evaporation is characterized. Jet A-1 was injected coaxially into the air stream under both spray and superheated conditions. During the experiments, five critical combustor components were varied to understand their individual effect on fuel vaporization and thus combustion performance. Exhaust gas emissions of NOx, CO, and unburned hydrocarbons (UHC) as well as OH* chemiluminescence images were used to evaluate combustor performance. Mie scattering technique was used to analyze the degree of liquid fuel evaporation for different test cases. It was found that the combustion performance indicator CO, height above burner, and flame length were well controlled by the degree of fuel evaporation, while NOx emissions showed little change with different combustor configurations. While the main factor influencing the level of NOx emissions was the adiabatic flame temperature, the quality of fuel evaporation played a minor role. It was found that the operating range of the combustor and the geometric shape of the flame are significantly influenced by the components of the combustor.