Sensors are a vital enabling technology for gas turbines and are critical to validation of design tools, new products, engine control, and health monitoring. The limitations of sensors in terms of survival temperature, accuracy, stability, and degradation limit where measurements are made during development and the operating ceiling of the gas turbine. Engines are run with safety margin in order to safeguard components against mechanical failure. Consequently, they are not run at their most optimal, which impacts overall efficiency. For example, a 10C uncertainty on turbine entry temperature changes the specific fuel consumption by 0.2%. Also a 0.2mm change in turbine tip clearance changes the specific fuel consumption by 0.4%. It is believed that with better sensing techniques, in excess of 500,000 tonnes of kerosene could be saved per annum, which equates to a CO2 saving of over 1.5 million tonnes. Despite some successes in recent research, it has become clear that the capability gaps are not closing quickly enough. Further research in to sensors and instrumentation is, therefore, absolutely essential if the capability gaps are to be filled at an adequate rate.
The headline objective of this project is to develop a suite of advanced sensors, instrumentation and related systems in order to contribute to the development of the next generation of green and efficient gas turbine engines.
The project will develop a range of advanced new sensors for high temperature gas path, surface, and structural measurements. The project also contains some detailed studies on wireless sensing. The sensors will be validated using both laboratory and rig trials to define their performance against specific targets. The project is being led by Meggitt UK and includes 5 of the EU's foremost gas turbine manufacturers.
Accurate condition monitoring for aero engines
EU-funded researchers have developed advanced sensors to collect accurate and reliable temperature measurements from all parts of aero engines under extreme conditions.
The efficiency of gas turbine engines increases with increasing gas temperature, allowing for a significant reduction in fuel consumption and carbon dioxide emissions. To achieve this reduction, the engine parts are protected by thermal barrier coatings (TBCs). These ceramic materials are able to withstand high temperatures and minimise the thermal input to the substrate.
The EU-funded project STARGATE (Sensors towards advanced monitoring and control of gas turbine engines) was launched to develop the technology needed to measure the critical parameters of thermal insulation layers up to temperatures of 1 600 oC. During the project's three-year lifetime, researchers succeeded in surpassing the limitations of existing sensors.
Among the sensors developed is an infrared radiation thermometer. Unlike short-wavelength infrared-range thermometers currently used, the new instrument is particularly suitable for non-contact temperature measurements of the surfaces of TBCs. Ceramics are semi-transparent in the short infrared region of the electromagnetic spectra, but not in the long infrared range.
In addition, STARGATE partners designed and validated a high-temperature pyrometer able to measure thermophysical properties of TBCs. Specifically, the thermal conductivity of the coating and the degree of emission of its surface can be measured in situ during gas turbine operation. Importantly, meaningful values would be obtained for use in optimising turbine operation.
STARGATE technology is expected to contribute to improving the next generation of green and efficient aero engines. To date, gas turbines are operated within safety margins safeguarding parts from mechanical failure because of the uncertainty in key parameter measurements. However, with the new sensing technology, it will be possible to operate these close to the maximum operating ceiling.