Experimental Analysis of the Fuel Flexibility of a Jetstabilized Micro Gas Turbine Combustor Designed for Low Calorific Gases

Fuel flexible burners are an important concept to aid in the advancement and implementation of renewable energy sources into existing infrastructure. As focus shifts from conventional to renewable fuel sources, designing gas turbines which meet both the technical and load requirements for fluctuating fuel compositions and heating values is imperative. The present work aims to study the stability and fuel flexibility of a two-stage burner, consisting of a jet-stabilized main stage and a swirl-stabilized pilot stage. Various fuel compositions, consisting of natural gas, hydrogen, carbon monoxide, carbon dioxide and nitrogen, with lower heating values ranging from 7MJ/kg to 49MJ/kg at an air preheat temperature of 873K were tested. Additionally, differing power loads (60kW to 100kW) and air-fuel equivalence ratio ranges (1.5-3.6) were examined. This study utilized OH* chemiluminescence measurements in conjunction with exhaust gas analysis of carbon monoxide and nitrogen oxide levels to assess the operation and reliability of the burner. Moreover, the experimental results are supported by steady state computational fluid dynamics simulations to provide explanation of the flame flow field characteristics and kinetics. The results indicate flame stability and low emissions levels for the majority of fuel compositions and thermal loads tested, therefore signifying high fuel flexibility of the burner. Additionally, optimal combustor operating points, which display emissions levels below the proposed German legal limits (German Federal Ministry for the Environment, 2016), were determined. Furthermore, the computational fluid dynamics simulation results indicate a good match to the experimental results, providing insight into the burner flow field characteristics and kinetics