Influence of surface roughness on burner characteristics and combustion performance of AM combustors

The transformation of the fossil fuel-based energy sector to a resilient, secure, and environmentally friendly equivalent, could potentially be achieved through the utilisation of “green” hydrogen-based energy. Although the introduction of pure, or blended hydrogen fuels to the power generation sector is associated with serious operability issues, novel manufacturing methods including Additive Manufacturing (AM) could assist in addressing such issues and facilitate the transformation of the power generation industry. Apart from the environmental, operational, and economic benefits afforded through AM, the latter is capable of delivering “manufacturable” surface roughness, enhancing the production efficiency of components and potentially improving gas turbine performance. This thesis aims to gain an understanding, through CFD and empirical investigations, of the impact of surface roughness on aerodynamics, combustion performance and emissions of a generic AM combustor characteristic of practical burners utilising conventional methane, pure hydrogen and an energy balanced mixture of methane and hydrogen. Parametric combustion studies of the selected fuel types are conducted in a new generic swirl burner under atmospheric pressure and elevated temperature conditions, relevant to practical burner designs. A system comprising of several diagnostic tools has been developed and operated to accommodate the empirical investigation of surface roughness and deliver the relevant research objectives. Additionally, a computational study of the impact of surface roughness on the resultant aerodynamic flow field has also been designed and implemented. The effectiveness of the employed computational method was supported by the experimental results. The analysis of the empirical and computational findings of the present thesis, aims to build upon the existing knowledge concerning the influence of surface roughness on burner characteristics and combustion phenomena, informing gas turbine manufacturers on potential advantages and economic incentives of AM burners. With increasing surface roughness, the flame location is shifted towards the centreline of the burner, due to the alteration of the aerodynamic flow field. This observation is further supported computationally. The trend is consistent under any fuel type studied and did not influence the NOx emissions or the burner stability envelopes

Additive manufacture and the gas turbine combustor: challenges and opportunities to enable low-carbon fuel flexibility

Advances in gas turbine (GT) combustion are enabled by metal additive manufacturing (AM) using selective laser melting (SLM) and other methods. In future low-carbon energy systems, AM will be critical for GTs operating on fuels such as hydrogen, ammonia, and biofuels. This paper evaluates the impact of AM on GT combustors, focusing on design freedom for novel geometries, reduced product development timelines, multiple component integration, and high-temperature materials suitable for harsh environments. Current AM challenges and research needs for GT combustors are discussed with industry input. These challenges are shown to be priority R&D areas across the GT value chain. Recent academic advances show the positive influence of widening access to SLM platforms and AM facilitates research using materials and geometries relevant to the GT community. Micro GTs are well-suited to SLM platforms, enabling novel geometries incorporating multiple functional parts including heat exchangers and porous media using advanced metal alloys. For industrial GTs, AM reduces new combustor product development time, as rapid prototyping and testing complements numerical methods. This review provides compelling evidence for continued AM R&D for GT combustion applications to meet future decarbonization goals