The Development of Ceramic-Based Thermocouples for Application in Gas Turbines

Abstract

A research and development project has recently been carried out to develop ceramic thermocouple probes (CTPs) capable of measuring temperatures up to 2000°C and rugged enough to withstand extended service in high-temperature gas turbine environments. Existing metallic thermocouple technology cannot withstand such conditions for sustainable periods of time. Following initial laboratory studies, CTP trials were carried out in power generation boilers (Farrell and Higginbottom, 1995). Prototype CTPs were subsequently developed for evaluation in gas turbine (GT) combustors (at atmospheric and elevated pressures) and in a Spey engine (Patent, 1996). The CTPs performed well under the harsh conditions imposed, demonstrating their mechanical integrity and consistency/sustainability of signal output. Initial studies have also been carried out with a view to applying ‘thin-layer’ ceramic thermocouples directly onto thermal barrier coatings to give surface temperatures on stator or other hot gas surfaces, and are briefly mentioned. Rowan Technologies and TÜV Energy Services are currently looking for companies interested in exploiting this new ceramic thermocouple technology.

Development of Thin Film Ceramic Thermocouples for High Temperature Environments

“…Ceramic-based thermocouples are known for their high stability and robustness at high temperatures, but are typically found in the form of rods or probes. 1 This investigation studies the feasibility of ceramics as thin film thermocouples for extremely high temperature applications thus taking advantage of both the stability and robustness of ceramics and the non-intrusiveness of thin films.…”

Thin‐Film Thermocouples Based on the System In2O3–SnO2

“…At high temperatures, phonon–phonon interactions become dominant and electron drag is no longer operant. This inhibits the flow of electrons, causing the thermoelectric voltage to level off 23,27 . The term “ n / T 1/2 ” deviates from a constant value and the Seebeck coefficient once again decreases.…”

“…A variety of ITO alloys were investigated in an effort to maximize the thermoelectric response and minimize the hysteresis between heating and cooling cycles during testing. Typically, thermoelectric voltage of bi‐ceramic thermocouples as a function of temperature exhibit a logistics function or an “S‐shaped” curve, which takes into account the effect of phonon–electron interactions as the temperature is cycled from low to high 23 . The relationship between thermoelectric response and temperature difference varies considerably from one bi‐ceramic combination to another and is normally described according to the following polynomial expression: …”

Microstructure and Properties of Thermal Electrode Material Si3N4–MoSi2 Composite Ceramics

“…The thermocouple is the most widely used temperature testing device in many industrial areas [1,2,3]. To realize accurate temperature testing in a high temperature and corrosive environment, a corrosive and high temperature resistance tube has to be used to protect the metallic thermocouple material [4,5,6,7,8].…”