Abstract
Yttria-stabilized zirconia (YSZ)-based thermal barrier coating (TBC) has been integrated with thermographic phosphors through air plasma spray (APS) for in-depth; non-contact temperature sensing. This coating consisted of a thin layer of Dy-doped YSZ (about 40 µm) on the bottom and a regular YSZ layer with a thickness up to 300 µm on top. A measurement system has been established; which included a portable; low-cost diode laser (405 nm); a photo-multiplier tube (PMT) and the related optics. Coating samples with different topcoat thickness were calibrated in a high-temperature furnace from room temperature to around 900 °C. The results convincingly showed that the current sensor and the measurement system was capable of in-depth temperature sensing over 800 °C with a YSZ top layer up to 300 µm. The topcoat thickness was found to have a strong effect on the luminescent signal level. Therefore; the measurement accuracy at high temperatures was reduced for samples with thick topcoats due to strong light attenuation. However; it seemed that the light transmissivity of YSZ topcoat increased with temperature; which would improve the sensor’s performance at high temperatures. The current sensor and the measurement technology have shown great potential in on-line monitoring of TBC interface temperature.
Highlights
Increasing the turbine inlet temperature has been a straightforward and effective approach to improve the efficiency of power machines
A remote temperature sensing technology has been developed for air plasma spray (APS) thermal barrier coating (TBC) based on phosphor
A remote temperature sensing technology has been developed for APS TBC based on phosphor thermometry
Summary
Increasing the turbine inlet temperature has been a straightforward and effective approach to improve the efficiency of power machines. For modern aero engines and gas turbines, the gas temperature at the turbine inlet is well beyond the melting temperature of the nickel-based superalloys commonly used for turbine blades and other engine components [1]. Thermal protection and cooling are usually required for safe and stable engine operation. Thermal barrier coatings (TBCs) with excellent insulation capability have been commonly used for protecting the turbine blades from excessive heat [2]. A 10–15 ◦ C increase would usually result in 50% reduction of the alloy’s lifetime [1]. Knowing the temperature beneath the coating during engine operation is highly desirable for the evaluation of the TBC’s performance. There is no doubt that determining the temperature at the interface between the TBC and the alloys would be critically
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