An experimental and numerical investigation of the aerodynamic characteristics of a flameless combustor

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Abstract

The flameless combustion (FC) regime is a promising technology for gas turbines, as it potentially yields lower NOx emissions while maintaining high combustion efficiencies. However, the application of FC to gas turbines is still challenging as required conditions for its occurrence depend on several factors such as reactants mixing, residence times, heat losses, and chemical time-scales. Since the mixing of the reactants and incoming fresh air-fuel mixture plays an important role in FC, the aerodynamic characteristics of the combustor are instrumental in determining the combustor emission performance. Focusing on the aerodynamic characteristics, this paper is dedicated to the visualization and description of the flow inside a jet-based combustor designed to operate under FC. The cylindrical combustor has a FLOX® burner head with 12 concentrically placed nozzles, while an acrylic cylinder allowed full optical access to the flow field. The investigation was performed for non-reactive flow. Using Particle Image Velocimetry and a Reynolds-averaged Navier-Stokes CFD analysis, the flow was visualized and modelled. The simulations were run with the Standard and Realizable k-ε (SKE and RKE, respectively), as well as a Reynolds Stress turbulence model. The effect of modifying the SKE model C constant was also investigated. In the experimental campaign, the influence of combustion chamber length, nozzle diameter, and jet velocity were investigated with respect to flow structure, recirculation ratios and entrainment behavior. The results show that the flow structure is mainly dependent on nozzle diameters, while the jet momentum is the correct parameter to assess the recirculation impact of a certain jet flow. The numerical investigation shows that the turbulence intensity at the boundaries is an important parameter to accurately simulate the jet spreading. None of the used turbulence models fully represented the flow field. Nonetheless, the SKE model with model C = 1.44 was the best at representing the jets penetration and vortex core positions, and the recirculation ratio values predicted by it were in good agreement.

Original languageEnglish
Title of host publicationCombustion, Fuels, and Emissions
PublisherASME
Number of pages11
Volume4A-2019
ISBN (Electronic)9780791858615
DOIs
Publication statusPublished - 2019
EventASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, GT 2019 - Phoenix, United States
Duration: 17 Jun 201921 Jun 2019

Conference

ConferenceASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, GT 2019
CountryUnited States
CityPhoenix
Period17/06/1921/06/19

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