Abstract

Recursive Sequential Combustion (RSC, introduced in paper GT2021-59592) is a new concept that maximises the interaction between burned gases and fresh reactants. The novelty compared to other concepts of flue gas recirculation in gas turbines is that this interaction is solely driven by the flow dynamics in the combustor. It consists of a novel inlet/outlet arrangement and an advanced flow design, which avoids complex extraction, reconditioning and re-injection of flue gases. The key feature is the burner arrangement which places the flames one after the other in a closed loop, maintaining a trapped circulation of constantly renewed hot gases flowing along annulus of the chamber. The aim is to achieve robust lean combustion supported by the high temperature of the flue gases, combined with the reburning effect of sequential combustion. The expected benefit of this technology is a steady lean operation with significantly lower NOx and soot formation than in conventional GT combustors.

This paper focuses on the flow design using a multiple discrete sector approach. A discrete sector has an inlet and an outlet accompanying the recursive hot gas flow, which is supplemented by fresh mixture injection, a flow mixer/conditioner, a flame tube and a flue gas separator. The N sectors are then arranged in a closed loop. Side feeds and outlets, as well as periodic boundaries along the annulus, allow circulation to occur.

An advanced discrete-sector concept designed for demonstration purposes is presented. The flow design is studied by CFD and supported by basic experiments. It is shown that the burnt gas circulation and interaction are effective, and that the closed loop recursive sequential combustion is within reach, demonstrating the plausibility of the concept.

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