Aerogels for thermal insulation applications usually take the form of thermal blankets it should be noted that thermal characteristics of aerogel blankets vary with manufacturing processes ( Bardy et al., 2007 Pacheco-Torgal et al., 2018). Most prominently, aerogels are utilized as thermal insulators in the areas of clothing, construction, aerospace, and energy due to their extremely low thermal conductivities. K) at 300 K), low density (ρ, Some unique properties of aerogels, including low thermal conductivity (k, 0.01–0.03 W/(m In addition, new materials for providing thermal barrier have been developed for improved cooling performance ( Goswami et al., 2004). In order to lower the metal temperature of combustor liner to improve the longevity of the component, cooling parameters, such as the shape of cooling holes and the amount of cooling air, have been the focuses of previous studies ( Goswami et al., 2004 Ahmed et al., 2019 Click et al., 2019). Inadequate cooling for combustor liners leads to reduced life expectancy of combustor liners and can further lead to premature failures of combustor components such as melted liners as reported in literature ( Ahmed et al., 2019). Rising pressure ratios of modern gas turbine engines make the cooling for hot gas path components more challenging as the compressor discharge air is at higher temperatures, making it less effective coolant for combustor liners and first stage nozzles. However, developments of more efficient gas turbine engines are usually associated with higher combustion temperatures, which in turn requires the usage more cooling air if cooling technology remains the same, in addition to the use of advanced high-temperature materials. Improvements can be made to the silica aerogel blankets for a more resilient thermal insulator, for example, by replacing glass fibers in silica aerogels.Īn effective way of improving the efficiency of gas turbine engines is to reduce the usage of cooling air for combustor and first stage nozzles, as cooling air for these hot gas path components has to be compressed to the highest pressure point of the entire engine. Test results suggest multiple degradation mechanisms to the silica aerogel blanket samples from the combustion tests. In addition, silica aerogel samples were examined before and after the combustion tests to understand their material degradation exposing to a typical gas turbine combustor environment using high-resolution scanning electron microscope (SEM). The measured temperature distribution of metal liner demonstrated superior thermal insulation of aerogel blanket under the protection of cooling film with a temperature difference as high as 1580 K between combustion products temperature and the metal liner temperature on the back side. The measured evolution of temperature distribution confirmed thermal equilibriums for every test condition with transpiration cooling. As the combustor was operated at a fixed equivalence ratio of 0.83, cooling air flow rates were varied to evaluate the effectiveness of transpiration cooling on the aerogel blanket as various cooling flow rates. To create a protective cooling film over the aerogel surface, cooling air was supplied from the back side of the perforated metal liner and was allowed to penetrate the silica aerogel blanket to be discharged to the combustor. Temperature distribution on the outer side of the combustion liner was measured using a calibrated IR camera. The silica aerogel blanket was attached to the inner side of a perforated combustor liner. In this study, a conical natural gas fired swirling-flame combustor was utilized for reproducing the combustion environment. Aerogels are a superior material for minimizing heat flux to the metal structure of the combustion liner due to their low thermal conductivity. An experimental study was conducted for evaluating the feasibility of using silica aerogel as thermal insulator for combustor liners.
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