Measurement and Simulation of Radiative Heat Transfer Through Thermal Barrier Coatings in Reacting Environments
Abstract
The purpose of this action is to provide FY25 CR2 funds in the amount of $20K. GRANT#14233224.--Approved for public releaseIncreasing engine performance and hot-section component durability is an important goal for Navy aircraft engines. These systems run at high temperatures under extreme operating regimes, including high-power operation and rapid transients. These kinds of extreme operations can drive high levels of heat load from the flame to the hardware through both convective and radiative heat transfer modes. The PIs# previous work explored the relative contribution of radiative vs. convective heat transfer in a canonical backwards-facing step geometry. It was shown that the radiative properties of the gases, both in terms of their radiative emission and absorption, played a significant role in heat flux to the walls. Further, a novel methodology for separating radiative and convective heat flux through combined experimental measurements and simulations provided a pathway for better understanding hot-section heat transfer in realistic reacting environments.The previous study, however, did not consider the material response to this heat transfer or use realistic hot-section materials, including thermal barrier coatings (TBC). Previous work by co-PI Zhao andexperimental measurements in typical TBC formulations have shown that significant portions of radiation in the mid-wave infrared wavelengths, between 1 and 8 microns, can penetrate the topcoat of the TBC. Unfortunately, the range of wavelengths at which TBC topcoats are translucent align with many strong radiation bands of the products of combustion, including CO2 and H2O, resulting in potentially high levels of radiation heat transfer to the bond coat of the TBC. This radiative heat loading has been identified as a potential damage mechanism for bond coats that can lead to TBC delamination and spallation. As such, improving the measurement and prediction capability of radiative heat flux in aviation-relevant TBCs could facilitate better prediction of part life and longer operating times for engines on-wing.The proposed work addresses this issue of measuring and simulating radiation heat transfer to and through TBC in reacting environments with a highly connected experimental and computational study. We will develop a two-wavelength diagnostic for measuring the heat flux through the topcoat of the TBC in reacting environments. In this technique, simultaneous imaging inthe mid-wave infrared (MWIF) and long-wave infrared (LWIR) will allow for measurement of the temperature of the bond coat and topcoat surfaces, respectively. Careful consideration of measurement in a reacting environment must be made, given the spectral absorption and emission of gases in these wavelengths of interest. This new technique will be used to measure heat flux in reacting environments with variations in gas temperature, gas composition, and the presence of soot, which can significantly alter the radiative heat transfer in the system. The experimental work will be highly coordinated with simulations. Current modeling capability includes a Monte Carlo ray tracing solver (MCRT) for solving radiation within the TBC, accounting for absorption, emission, and scattering. A MCRT solver has also been developed to be coupled with LES for solving combustion and radiation within the combustor. The radiation solvers will be validated using the novel experiments first. Subsequently, detailed analysis will be conducted to understand the spectral characteristics of radiation within TBC and upon the bond coats. Insights on designing spectral windows of the TBC will be proposed based on the analysis. Finally, temporal variations of temperature and heat flux within the TBC and on the bond coats will be analyzed to understand the dynamic inputs to the TBC in reacting environments.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 10, 2025
- Source ID
- N000142512230
Entities
People
- Xinyu Zhao
Organizations
- Office of Naval Research
- United States Navy
- University of Connecticut