Experimental Investigation of the Combustion Behavior of Single-Nozzle Liquid-FLOX®-Based Burners on an Atmospheric Test Rig

Abstract

As an alternative to the commonly used swirl burners in microgas turbines (MGT), the FLOX®-based combustion concept promises great potential for the nitric oxide emission reduction and increased fuel flexibility. Despite having to deal with a new set of challenges while utilizing liquid fuel in the burner, first steps are taken to gain more information on the influencing operational parameters. In this regard, a FLOX®-based liquid fuel burner is developed to fit into a newly designed combustor for the Capstone C30 MGT. The C30 combustor operates with three burners arranged tangentially to an annular combustion chamber and provides a total thermal power of 115 kW. In this work, operational properties of merely one of the three C30 liquid fuel burners are investigated and the rest of the two burners are emulated in form of hot cross-flow. As for the liquid burners, the experiments are conducted with three geometrically different single-nozzle burners at atmospheric pressure. The cross-flow is realized by utilizing a 20–nozzle FLOX®-based natural gas combustor. Measurements include visualization of the reaction zone and analysis of the exhaust gas emissions. By detecting the hydroxyl radical chemiluminescence (OH*-CL) emissions, the position of the heat release zone within the combustion chamber is attained. Correspondingly, the flame height above burner and the flame length are calculated. The investigated design parameters include air preheat temperature up to 733 K, equivalence ratio, burner geometry, and thermal power. Through variation of thermal power, the effect of liquid fuel preparation, i.e., atomization, evaporation, and mixing on combustion properties and exhaust gas emissions are examined. The results show that the burners with the medium diameter consistently performed remarkably at different flame temperatures and thermal powers. The lowest NOx and CO emissions for the medium diameter burner lied between 5 to 7 ppm and 8 to 10 ppm, respectively.