Overview
Instrumentation is a key generic technology in the gas turbine industry which impacts the development cost, efficiency and competitiveness of gas turbine products in three areas:
- instrumentation used during product development to validate new product designs. The main impacts are on product development time and cost and improving efficiency;
- instrumentation fitted to engines in service to monitor engine health. The main impacts are on cost of ownership, availability and reducing spares consumption;
- instrumentation to enable optimum control of the engine operation.
The main impacts are on more efficient/environmentally friendly cycles. The gas turbine environment presents unique challenges to instrumentation. The drive to greater efficiency is steadily raising the temperatures and pressures in engines, and this increases the challenge to the instrumentation.
The HEATTOP project aimed to address the need for improved instrumentation to be used in development, design evaluation and performance monitoring of aero engines and industrial gas turbines for power generation. In the middle of interest were the hottest regions of engines, the combustors and HP turbines where temperatures reach 2 000 K. The objective of the HEATTOP project was to develop accurate high temperature sensors for measurement of pressure, temperature and tip clearances.
The temperatures directly effect engine efficiency and life time of components. As current sensors cannot be placed in the hottest regions, knowledge of conditions inside the turbine is gathered from outside measurements which are then extrapolated by using models and assumptions. Turbine parts and other hot gas components are very expensive, have a shorter life time due to heavy mechanical and thermal loads and are critical for engine reliability. Accurate knowledge of temperatures would be very beneficial in predicting their life time and verify the performance of a design. Other aerodynamic parameters as dynamic and static pressure and clearances affect efficiency, operation and health of an engine.
To achieve the project's goals within a period of 45 months, a work programme was set up to develop measurement technologies for high temperatures in four areas with specific development objectives:
- Advanced thermocouple technology
- Measurement of surface temperatures
- Gas path aerodynamic measurements
- Tip clearance measurement system
- Testing and validation of all developed techniques in rigs and engines.
- Dissemination of technology developments by the developers
The responsibilities and work were structured in three main areas and nine work packages (WPs):
- Specification and validation: containing WP 1 - Definitions, and two WPs for sensor validation in test facilities: WP 6 - Sensor rig tests and WP 7 - Sensor engine tests.
- Sensor design and development: containing four technical development WPs.
- Coordination and dissemination: dedicated to coordination and project management (WP 0) and dissemination of results (WP 8).
More specifically, the WPs included:
- WP 0 - Project management
- WP 1 - Definitions and specifications
- WP 2 - Life and accuracy optimisation of current instrumentation for high temperature measurement
- WP 3 - Advanced solid temperature measurements
- WP 4 - Gas path aerodynamic measurements
- WP 5 - Tip clearance measurement
- WP 6 and WP 7 - Validation of technologies
- WP 9 - Dissemination of results.
Funding
Results
Among the most important results obtained, the following can be reported:
- 1 and 2 - Improved fast response thermocouples. High frequency response time thermocouple for wall temperature measurement in engine environment. High stability K type thermocouples, after several thousands of hours on engine.
- 3 - Advanced stable thermocouple system as results of design of experiment. Optimised thermocouple system for exhaust gas temperature measurement. Better than class 1 accuracy (about 0.25 %) over the life of the thermocouple for temperatures up to 1 050 degrees Celsius.
- 4 - Advanced high temperature thermocouple. A new Ni-based thermocouple in MIMS configuration has been designed at the Department of Materials Science and Metallurgy of the University of Cambridge. The new thermocouple allows temperature measurements up to 1 200 degrees Celsius with a total drift of about 2 degrees Celsius: this is a significant improvement compared to the conventional Ni-based thermocouples which can have drift as high as 15-20 degrees Celsius.
- 5 - Ceramic-based thermocouple for temperature measurement up to 1 500 degrees Celsius, in engine environment.
- 6 - Embedded fibre optic sensors. Siemens has developed and demonstrated fibre Bragg gratings sensors embedded in high temperature components of gas turbines for solid temperature measurement. Together with the partners IPHT and AOS the first sapphire Bragg grating (FBG) sensor multiplexing was achieved. A sapphire-based FBG sensor was inscribed in IPHT Jena by high-energy FS laser and has been demonstrated at temperatures up to 1 200 degrees Celsius with temperature drifts below ±5 K. As a further unique feature, the highest temperature stability has been achieved with T > 1 750 degrees Celsius, as the most severe conditions a fibre-optic temperature sensor can be used.
- 7 - A pyrometer corrected / calibrated for transmission and fouling. A boroscope hole pyrometer has been designed and constructed. It includes a facility for on-line calibration for fouling and transmission losses, thus enhancing the instrument with self-inspection capability.
- 8 and 9 - Advanced pyrometer design know-how. Advanced pyrometer system that is insensitive to most types of lens contaminant for HP turbine blade measurement.
- 10 - Thermographic phoshors for quasi 2D temperature measurement on airfoils, under high temperature and pressure.
- 11 - A high temperature water-cooled fast response total pressure pr
Technical Implications
The HEATTOP project developed sensors and probes which are critical for efficient, economic, reliable and environmentally friendly operation of gas turbines in aero engines and in stationary power generation facilities. The current limits of instrumentation had to be stretched, while at the same time accuracy and reliability needed to be improved.