The aims of this work are to achieve a better understanding of thermal fluxes around a multi-perforated plate and obtain correlations for heat transfer coefficient on the hot as well as cold side and in a perforation. A 3-dimensional, RANS, conjugate simulation and an adiabatic one are performed for different aerothermal conditions already studied experimentally. Convective heat flux, wall temperature and adiabatic temperature are averaged on a periodic pattern around each hole. A mean heat transfer coefficient is calculated based on these quantities and correlations are deduced for this coefficient. Such results as fluid temperature rise in a perforation or the contribution of flux in the perforations to the whole cooling flux are also given in this article.
An experimental and numerical study is carried out on a cooling film issuing from a multiperforated wall of a simplified combustor. The objectives of this work are to achieve a better understanding of the dynamics of the film and to construct an experimental database on a simplified geometry in order to test numerical models. A parametric study of film cooling efficiency based on the direction of the cooling air injection is presented and shows that a swirling injection greatly enhances the cooling efficiency. As accounting for multiperforated walls in numerical simulations cannot be done at the jets scale because of computing resources, in this article are presented RANS computations performed using a uniform boundary condition to provide the injection of coolant. Two injection models are applied on this boundary and numerical results are compared to experimental data in the recovery region. The standard model is shown to be totally inappropriate while the multiperforation model delivers promising results although some weaknesses appear very close to the wall.
When a gas turbine combustor is manufactured, small geometrical differences between production runs are unavoidable. These geometrical differences potentially influence performances such as service life, lighting, lean blow off, pollutant emissions. To ensure performances, manufacturing tolerances are kept tight enough so as to neglect their impact. However, loosening some key manufacturing tolerances can result in lower manufacturing costs, while maintaining combustion performances at a satisfactory level. The present study aims at challenging some cost-driving manufacturing tolerances of Safran Helicopter Engines new turboshaft combustor, using state-of-the-art 3D numerical tools. The objective is to guarantee robust and long lasting combustor performances at a reasonable manufacturing cost. To this purpose, an optimized Latin Hypercube Sampling of 30 geometrical configurations around the nominal geometry has been simulated with a 3D LES solver. Simulation parameters had to be chosen to keep computation costs manageable and to have a high representability when comparing geometries. These aspects are checked using theoretical considerations and comparisons with both experimental data and previously validated simulations. The temperature field at the combustion chamber exhaust has been analyzed in detail using metamodeling. In particular, the Radial Temperature Distribution Factor (RTDF) at the combustor outlet appears to be robust. Such large designs of numerical experiments (DonE) are computationally expensive but they provide a reliable tool to assess the robustness of a combustor design, and define optimized manufacturing tolerances.
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