Development of cost-effective alternatives to conventionally-manufactured metal foam for industrial turbine combustors

Abstract

The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations. Ultimately, the optimal design should be a graded structure, starting with a very porous grid made from a large wire diameter to breakdown the incoming vortices. Additional grids should be rotated and offset to increase the tortuosity, as it improves the velocity homogeneity. The wire diameter of the subsequent grids should be progressively smaller to reduce the TKE. The spacing between the grids should be as large as possible and their numbers must be kept to a minimum to avoid excessive pressure losses. The porosity should only be reduced when the desired velocity uniformity cannot be obtained by other means.

Date	12 Apr 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Vladimir Brailovski (Supervisor) & Marlène Sanjosé (Co-supervisor)