High Pressure Effects on CH4-H2 Premixed Flammes: Application to Gas Turbine Burners

This study is a numerical simulation of pressure effects (2.2 to 22 bars) on CH4-H2 (50%-50% by volume) turbulent flames. The studied burner is designed for gas turbine application used in power generation. The geometry is cylindrical with 9 radial vanes generating swirled flow. All simulations were conducted for a constant reactive mixture richness of 0.55 and for an inlet temperature of approximately 570 K. A 3D approach was adopted using RANS k-ε Realizable variant for turbulence treatment, Probability Density Function (PDF) model for chemistry and NO model for pollutants. The analysis focused primarily on the thermal and dynamic fields (velocity and temperature) without forgetting NOx and CO formation. The results show that the increase in power induced by the rise in pressure did not significantly affect the flow or the flame structure. A variation in the size and position of the central recirculation zone (CRZ) and the outer recirculation zone (ORZ) was observed, without compromising the stability of the flames. However, the increase in power necessarily implies a higher heat release rate, which led to an intensified production of NOx; from 5.5 ppm to 11.2 ppm for a power increase from 84 kW to 840 kW. These values remain acceptable considering the achieved power level. On the other hand, this variation resulted in a decrease in CO emissions; from 10 ppm to 4 ppm for the same tested power range due to the intensification of the reaction rate. The data obtained show that CH4–H2 reactive mixtures injected at high pressure (around 20 bar) represent a promising solution to explore for hydrogen utilization and decarbonization. These results are preliminary, and more in-depth tests must be carried out to assess the feasibility of using hydrogen in gas turbines (G.T) safely and without risk.