Experimental Study of Natural Gas and Hydrogen Co-Firing Characteristics Using Different Types of Single Nozzles of F-Class Practical Gas Turbine Combustors

Recently, research through the co-firing of natural gas and hydrogen, a carbon-free clean fuel, is attracting attention because to reduce greenhouse gas emissions from aging gas turbine power generation is one of the key energy issues. This can enhance the capability of old gas turbines and contribute stably to an increase in the proportion of combined cycle power plant utilization following the gradual shutdown of coal-fired power plants in Korea. The purpose of this study is to find the optimal operating conditions of mixed fuels without hardware modification of the F-class gas turbine combustor. The experiment was performed according to the load and the co-firing rate using four different types of fuel nozzles (F-Class DLN combustors), and the flame characteristics according to the change in conditions could be analyzed. Under this study, co-firing test was performed with natural gas and hydrogen. The test conditions were selected based on actual machine operating conditions from 30% to 100% thermal load and the hydrogen co-fired with natural gas up to 70% at each load. OH high-speed imaging and an OH-PLIF technique were used to analyze the flame structure, and flame characteristics of co-fired flame in detail. In addition, dynamic pressure was measured to check the combustion instability and exhaust gas emissions were measured to evaluate combustion characteristics of co-fired flame. Major findings are critical co-firing rates of each nozzle based on NOx emission level and combustion dynamics. As the hydrogen co-firing rate increased, the flame length decreased compared to natural gas combustion, and it was confirmed that NOx increased rapidly with the co-firing rate over about 30%vol. In addition, the measured dynamic pressure oscillation results for each nozzle did not show significant variations compared to natural gas combustion. Through this study, it was possible to derive the characteristic operation map of a single nozzle according to the hydrogen co-firing rate.