High-Temperature Heat Flux Sensor Based on Composite Ceramic Thermal Resistance Layer

Surface heat flux density is critical for aerospace components, especially engine blades and turbine disks that operate at high temperatures. Conventional water-cooled sensors are impractical for in situ testing, and thin-film heat flux sensors (HFSs) have limited high-temperature durability. To overcome those shortcomings, this study proposes a design method for the high-temperature HFS (HTHFS) that eliminates the need for a water-cooled structure and has excellent high-temperature performance. The HTHFS features a three-layer coated structure comprising a 99% Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic substrate, PtRh10/Pt thermopile sensitive layer, and composite ceramic thermal resistance layer (TRL). The effective hot junctions of the HTHFS contact the heat source directly, while the rest of the sensor surface is coated with the TRL of low thermal conductivity and high temperature resistant. The proposed design improves the oxidation resistance, sensitivity, and transient response. The HTHFS was fabricated using screen-printing and air spraying processes. Repeatability, stability, and temperature resistance test results for the HTHFS reveal that the average heat flux at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1400~$ </tex-math></inline-formula>°C was 403.27 kW/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, with a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.58~\mu $ </tex-math></inline-formula>V/(kW/m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\text {)}$ </tex-math></inline-formula>. The dynamic response time (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}_{{90}}\text {)}$ </tex-math></inline-formula>, measured via the laser impulse response method, was 1.08 ms. Notably, the HTHFS operated at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1400~^{\circ }$ </tex-math></inline-formula>C for more than 5 h without failure. Characterized by low thermal impedance, high-temperature resistance, rapid response, and high reliability, the HTHFS can accurately measure the heat flux, making it highly valuable for in situ sensing applications in high-temperature aerospace components.