Low calorific value fuelled distributed combustion with swirl for gas turbine applications

Abstract

Distributed combustion offers significant performance improvement with near zero emissions for industrial gas turbine applications. Our efforts to further develop zero emission distributed combustion are explored here by utilizing swirl to the flow. The beneficial aspects of distributed swirl combustion using a cylindrical geometry combustor has shown low emissions of NO and CO, and significantly improved pattern factor using methane as the fuel at high thermal intensity. Biofuels, syngas and landfill gases offer superior use in gas turbine combustion. However, they are characterized by their low calorific value. Results are presented here from the distributed swirl combustor with simulated low calorific value fuels with defined mixture of methane diluted with nitrogen. The calorific value of the fuel obtained provided comparable adiabatic flame temperature and flame speed to those characteristic of low to medium calorific value syngas fuels. The results are compared with the methane fueled combustor. Experimental results from the distributed swirl combustor using methane fuel at an equivalence ratio of 0.6 and a heat release intensity of 27MW/m3-atm showed low levels of NO (∼9PPM) and low CO (∼21PPM) under non-premixed conditions. Novel Premixed Combustion design demonstrated 4PPM of NO and 11PPM of CO. In contrast methane diluted with nitrogen resulted in a dramatic decrease of NO emissions (30–50%), to provide NO emission of 7PPM (for non-premixed case) and 2.8PPM (premixed case), at the same conditions, with minimal impact on CO for all the conditions examined here. The combustor provided no instability or flame flashback at higher fuel flow rates (to maintain the same thermal load as with methane fuel). Results obtained with different calorific value fuels on the emissions of NO and CO, lean stability limit and OH* chemiluminescence are presented. The results showed favorable operation of the distributed swirl combustor for applications with both high and low calorific value fuels, such as, methane, synfuel and landfill gases to power the gas turbines without any combustor modifications.