Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Metal Temperature

Abstract

Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation, however, involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. A reduced coolant mass flow rate in conjunction with higher compressor discharge temperature negatively affect the cooling potential thus requiring the exploitation of efficient schemes such as effusion cooling. This work describes the experimental and numerical final validation of an aeronautical effusion-cooled lean-burn combustor. Full annular tests were carried out to measure temperature profiles and metal temperature distributions at different operating conditions of the ICAO cycle. Such an outcome was obtained also with an in-house developed CHT methodology (THERM3D). RANS simulations with the Flamelet Generated Manifold combustion model were performed to estimate aerothermal field and heat loads, while the coupling with a thermal conduction solver returns the most updated wall temperature. The heat sink within the perforation is treated with a 0D correlative model that calculates the heat pickup and the temperature rise of coolant. The results highlight an overall good capability of the proposed approach to estimate the metal temperature distribution at different operating conditions. It is also shown how more advanced scale-resolving simulations could significantly improve the prediction of turbulent mixing and heat loads.

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

“…In order to have a wider library of models and more customization freedom, a migration from ANSYS CFX to ANSYS Fluent was required. In this context, an early application of THERM3D in ANSYS Fluent can be found in Reference [ 24 ], giving the basic framework for the development of the coupling code applied in the present work.…”

“…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.…”

“…Hence, to speed-up the flow field simulation without an appreciable lack of accuracy, a domain including only the flametube and an upstream plenum was taken into account. An investigation of the whole system, including hot and cold sides, is illustrated in Reference [ 24 ] using a RANS approach, highlighting how the wall temperature is driven by the hot side. This domain choice has little or nothing effects on the radiative fluxes because the cold annulus does not see the flame and the contribution of radiation is negligible compared against the convective ones, as reported on the energy budgets in Reference [ 24 ].…”

“…Concerning solid and radiation grids, these were the same exploited in Reference [ 24 ]. In the second one, it was strongly coarsened starting from the mesh of the convective problem, obtaining a 4 M tet-only elements grid.…”

“…The full scale tests performed at the Central Institute of Aviation Motors (CIAM) provided fundamental validation results at different operating conditions in terms of outlet temperature maps, pollutant emissions, and wall temperature. Steady-state CFD analyses were carried out on the very same annular combustor with the THERM3D tool in Reference [ 24 ] to predict liner temperature, whereas Scale Resolving modeling was adopted in Reference [ 25 ] for an accurate description of aerothermal field focusing on profile temperature and pollutant emissions at the combustor outlet. The results revealed that CHT analyses can take advantage of high fidelity CFD models for turbulence.…”