A 3D Coupled Approach for the Thermal Design of Aero-Engine Combustor Liners

Abstract

The adoption of lean burn combustion to limit NOx emissions of modern aero-engines imposes a drastic reduction of air dedicated to cooling combustor dome and liners. In the latest years many aero-engine manufacturers are hence implementing effusion cooling, which provides uniform protection on the hot side of the liner and significant heat removal within the perforation. With an industrial perspective, the development of such components is usually carried out with different strategies depending on the level of accuracy required in the design phase involved (i.e preliminary or detailed). In the collaboration between GE Avio and University of Florence, the preliminary design of these devices is carried out with Therm1D, an in-house thermal flow-network solver based on the 1D correlative approach proposed by Lefebvre. This strategy, however, is not capable of taking into account the complexity of the three-dimensional nature of the flow field and the interaction between swirling flow and liner cooling, making necessary the use of Computational Fluid Dynamics (CFD) in the most advanced phases of the design process. Nevertheless, notwithstanding the increasing popularity of CFD, even a RANS simulation of a single sector of an annular combustor still presents a challenge, when the cooling system is taken into account. This issue becomes more critical in case of modern effusion cooled combustors, which may contain thousands of holes for each sector. With the aim of of increasing the fidelity of the prediction, keeping in mind the industrial needs for limited computational efforts, a new tool has been developed: Therm3D. This approach involves the CFD simulation of the combustor flametube by modelling effusion cooling with point mass sources, whereas the fluid dynamic prediction of the remaining part is fulfilled exploiting the equivalent flow-network solver implemented in Therm1D, which provides the estimation of flow split and cold side heat loads. The solution is coupled with two separate calculations aimed at solving flame radiation and heat conduction within the metal. This paper describes the main findings of the application of Therm3D to a lean annular combustor. The results obtained have been compared to experimental data and the above mentioned numerical tools employed during the design process.

Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

“…Exploiting a past experience in the modeling of steady Conjugate Heat Transfer in the context of ANSYS CFX (i.e., THERM3D developed by Mazzei [ 26 ]), a new tool, called U-THERM3D, was developed to investigate multi-physics CHT problems in an unsteady fashion, taking advantage of the high-fidelity potential of Scale Resolving methods in predicting phenomena affected by turbulence. In order to have a wider library of models and more customization freedom, a migration from ANSYS CFX to ANSYS Fluent was required.…”

“…For example, in the developed approach for CHT problems on combustor liners, the additional modelings that actually are not possible with the standard solver are the decoupled solution of radiative problem using a mesh that is coarser than fluid domain one. To enforce this last sentence, Figure 1 highlights also the integration in the workflow of a dedicated solver for the heat sink effect of effusion holes that was a key task of the steady state methodology THERM3D [ 26 ]. It is based on the computation of the overall energy balance across the hole using a correlative approach.…”

“…The boundary conditions at inlet and outlet patches are evaluated through a dedicated imprinting technique, where the coolant is injected with a specified direction and velocity. As it will be discussed in the following, this feature is not adopted in the current investigation: the interested reader is referred to References [ 24 , 26 ] for further details. An example of application of a similar methodology can be found in Reference [ 30 ] for turbine blade cooling.…”

Low order modeling method for assessing the temperature of multi-perforated plates

“…In recent studies, effects of radiation have also been introduced. Mazzei et al [48] used a 3 solvers coupling approach to account for the interplay between fluid mechanics; solid heat diffusion and radiative transfers. Berger et al [10] used the same methodology but solved the fluid dynamics with a LES solver.…”

Network analysis of a coolant flow performance for the combined impingement and film cooled first-stage of high pressure gas turbine nozzle guide vane

“…Mazzei et al 21 developed an in-house thermal flownetwork solver named as Therm1D for the preliminary design of an aero-engine lean annular combustor dome and liners. The calculation of flow split and cold side heat loads using Therm1D have been validated with experimental results.…”