Investigation on combustion characteristics and emissions of biogas/hydrogen blends in gas turbine combustors

Abstract

In the present work, numerical investigations are performed to study the combustion characteristics of biogas fuel blended with hydrogen at various compositions for a non-premixed swirling flame in a can-type gas turbine combustor. The amount of hydrogen enrichment varies from 0 to 50% by volume. A numerical approach using the non-premixed flamelet model, turbulent standard (k–ε) model, and P-1 radiation model was adopted for simulating the can-type combustor power at a fixed operating power of 60 kW. The steady laminar flamelet model was used to analyze the effect of hydrogen enrichment, global equivalence ratio with different swirl numbers on a stable flame operation, temperature distribution and contours, velocity streamline contours, NO emissions, and species concentrations. The results indicate that hydrogen enrichment and the variation of the equivalence ratio and the swirl numbers significantly impacted the flame macrostructure. Hydrogen enrichment in the fuel intensifi combustion, leading to higher flame temperature and wider flammability than bure biogas. Maximum NO emissions in the outlet chamber have been dropped by 43 and 78 (ppm @15 % by volume of O2) for the biogas and biogas-50% H2, respectively, due to the reduced flame temperature leading to reduction in thermal NOx formation with reduction equivalence ratio from 0.5 to 0.2. The flame temperature and NO emissions at ϕ=0.2 with a high rate of hydrogen (50% H2) are close to the results of pure biogas (0% H2) at the same equivalence ratio. The results show that CO and CO2 emissions decrease with increasing hydrogen addition and decreasing the equivalence ratio; due to a decrease in the amount of carbon, the cooling effect, and an increase in the OH concentration.