Hydrogen Addition Effects on Methane-Air Colorless Distributed Combustion Flames

摘要

The role of hydrogen addition to methane fuelled flames under high intensity colorless distributed combustion (CDC) conditions for application to gas turbine engines have been investigated. The CDC conditions require carefully tailored fuel-air mixture preparation through product gas recirculation and good mixing between the combustion air and recirculated gases prior to mixture ignition. Rapid mixing between the injected fuel and hot oxidizer is desirable prior to spontaneous ignition of the mixture to achieve distributed reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In this investigation the role of hydrogen addition in a reverse flow mode configuration, consisting of both non-premixed and premixed combustion modes, have been examined for the CDC flames. In the non-premixed configurations the air injection port is positioned at combustor exit end while the fuel injection port is positioned on the side so that the fuel is injected in cross-flow with respect to air injection. The thermal intensity of the flames investigated is 85MW/m3-atm to simulate the gas turbine combustion conditions. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flow field using numerical simulations. Ultra low NOx emissions are found for both the premixed and non-premixed combustion modes. Addition of hydrogen to methane fuel resulted in an increase of NO emission, decrease of CO emission and extended the lean operational limit of the combustor.