Hot Section Materials and Durability

Relative Contribution of Radiation vs. Convection on Combustor Liner Heat Transfer

Overview

Increasing engine performance and thermal efficiency can be achieved through increasing combustor firing temperature. Increasing temperature can also result in durability issues for the combustor hardware, including surface burning, thermal stresses, and accelerated component degradation. Prediction of these durability issues is difficult, however, as combustor flow fields are complex and computational fluid dynamics (CFD) predictions often do not properly capture the multi-physics nature of combustion. There are three goals of the proposed work. First, use tightly-integrated experiments and simulations to quantify the relative contributions of radiation vs. convection on wall heat transfer in a combustor with realistic flow features. Second, determine the necessary fidelities of radiation and convection wall models through parametric comparison among models and between models and experiments. Third, quantify the impact of transient heat loading on the thermal state of the combustor liner for a range of different transient timescales. In the proposed program, experiment and simulation will work in close concert to address the three goals of the project. The results of the work will allow the Navy to better understand potentially damaging processes in mission-critical components, including gas turbine main combustors and augmentors.

Data from project is publicly available for use with attribution:

Funded by the Office of Naval Research

In collaboration with Dr. Xinyu Zhao, University of Connecticut

Colborn, J., Tricard, N., Denman, J., Zhao, X., O’Connor, J. (2024). “Interpreting Measurements of Total and Radiative Heat Flux in a Vitiated Backward-Facing Step Flow.” AIAA Journal, 62(8), p. 2967-2978.

Colborn, J., O’Connor, J. (2024) “Impact of flame-wall interactions on combustor liner heat flux.” Spring Technical Meeting of the Eastern States Section of the Combustion Institute. Author accepted pre-print available here.

Colborn, J., O’Connor, J. (2024). “Measurement of Heat Flux in Reacting Flow in a Backward-Facing Step Combustor.” AIAA SciTech Forum, Orlando, FL. Accepted author version here.

Colborn, J., O’Connor, J. (2023). “Variation in Convective and Radiative Heat Transfer with Reynolds Number and Temperature in a Backward-Facing Step Combustor.” AIAA SciTech Forum, National Harbor, MD. Accepted author version here.

Toumey, J., Zhang, P., Zhao, X., Colborn, J., & O’Connor, J. (2022). “Assessing the wall effects of backwards-facing step flow in tightly-coupled experiments and simulations.” In AIAA SciTech 2022 Forum.

 

Long-term impact of high-hydrogen combustion on gas turbine hot-section materials

Decarbonization of gas turbines will require the switch from natural gas and distillate fuel oil fuels to low-carbon fuels, including hydrogen, ammonia, and e-fuels like methanol. The objective of this project is to better understand the long-term impacts of the use of high-hydrogen fuels on gas turbine hot-section materials, including alloys and coatings. There are several potential issues that arise for the materials with high-hydrogen fuels because of the increased water content in the combustion products. Water increases the heat capacity and thermal conductivity of the gases, increasing convective heat transfer to the parts. Increased water content can also change thermal and mechanical loads, as well as the oxidative environment. The long-term impact of these issues, however, is not well understood, and so this project begins to address this lack of knowledge.

Funded by EPRI.

O’Connor, J., Noble, D., Bridges, A., Shingledecker, J., Scheibel, J., Gagliano, M. (2024) “Review of the impact of hydrogen-containing fuels on gas turbine hot-section materials.” ASME Turbo Expo, London, England, UK. (open access)

 

Enhancing CMC Temperature Performance in High-Hydrogen Environments using Field Assisted Sintering Technology

The ceramic matrix composite (CMC) class of materials offers several advantages for next generation ultra-high temperature (UHT) applications. Their overall compositions, typically Ox/Ox, Cf/Cm, or SiC/SiC, boast low densities and high melting temperatures, which make them favorable for aerospace and power generation applications. However, manufacturing CMCs requires several design considerations such as the fiber material, the fiber placement and layup, any applied coating on the fiber itself, and the matrix material. Properly engineered, the proper material formulation allows for enhanced toughness, strengths, and moduli that result in a class of materials that meets many of the needed design targets for UHT applications. Implementation of CMCs will help overcome many of the hot-section durability and lifing challenges associated with high-hydrogen combustion, which is a pathway to rapid decarbonization of a large portion of the electricity-generation sector. Increasing the fraction of hydrogen in natural gas fuel, and eventually transitioning to 100% hydrogen gas turbines, will require a new design paradigm for combustors, including flame stabilization, component cooling, and durability of ceramic coatings.  The objective of the proposed work is to significantly improve (>150° C) the temperature performance of ceramic matrix composite (CMC) materials in high-hydrogen environments through the use of field assisted sintering technology (FAST) to manufacture CMCs. These materials are tested in realistic combustion environments to understand their behaviors as a function of fuel composition and flame temperature.

Funded by the US Department of Energy

In collaboration with Drs. Doug Wolfe and Stephen Lynch

Richens, P., Surrency, C., O’Connor, J., Lynch, S. (2024) “Experimental design for testing the total heat flux through high-temperature components in high-hydrogen combustion environments.” Spring Technical Meeting of the Eastern State Section of the Combustion Institute. Author accepted pre-print available here.

 

Combustor/Turbine Interaction

Overview

In a gas turbine engine, high levels of vorticity are intentionally generated in the combustor to improve combustion efficiency and stability, but are also convected downstream to the turbine vanes. In the subsequent interaction with the vanes, both pressure and temperature fluctuations are critically important, since the vane material is subject to gas temperatures exceeding its melting temperature. The vane is designed with advanced internal and external cooling schemes to allow for extended operation, but industry trends of shorter combustor lengths and more vigorous fluid mixing mechanisms in the combustor indicate that understanding the nature of the unsteady vorticity interaction with the vane thermal boundary layer is more critical than ever. The goal of this work is to better understand the behavior of large-scale structures from the combustor as they interact with the turbine, and how these fluid-mechanic effects drive changes in heat transfer in the turbine.

In collaboration with Dr. Stephen Lynch

Publications

Leonetti, M., Lynch, S., O’Connor, J., Bradshaw, S. (2017) “Combustor Dilution Hole Placement and Its Effect on the Turbine Inlet Flowfield.” Journal of Propulsion and Power, 33(3), p. 764-775.