Distributed combustion mode in a can-type gas turbine combustor – A numerical and experimental study

Abstract A novel combustor design assisted with increased hot air jet momentum is used to enhance the internal recirculation. Geometric modifications are incorporated in terms of altered air injection scheme to improve the mixing and internal recirculation of hot combustion products. The combustor operates with liquefied petroleum gas in a distributed combustion mode, and thermal intensities vary in the range of 20–40 MWm−3atm−1. Numerical calculations of the reacting flow field show the presence of large recirculation zones, and they are quantified using reactant dilution ratio, Rdil. It is greater than 2.5 for the most part of the combustor, thereby creating a sufficiently heated and diluted environment for sustaining the distributed combustion at high thermal intensities. OH* chemiluminescence studies are carried out for the first time to observe the combustion zone structure for the conventional and distributed combustion regime in a gas turbine combustor. The distribution of OH* becomes increasingly uniform with reduced maximum OH* intensity in this combustion mode. The measured NOx is less than 8 ppm, and CO emission is below 25 ppm for all the operating conditions (ϕ = 0.2–1). Acoustic emissions drop significantly, as the combustor switches its operation to a distributed combustion mode. The novelty of this study lies in the application of this combustion mode in a gas turbine engine. This article also sheds light on the importance of the internal recirculation of combustion products, to achieve a distributed combustion mode in a generic can combustor at gas turbine relevant conditions.