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These videos demonstrate a prototype system that uses multiple wirelessly networked sensors to deliver detailed spatial-temporal flow temperature information on a gas turbine engine.
Measurement of temperature in a gas turbine engine is critical to its control and the assessment of its health and performance. Currently, gas temperature is measured predominantly by thermocouples installed at a number of sites within the engine. For example, in the exhaust region of the engine, the temperature is measured at different circumferential (and often radial) position via an array of thermocouples connected through harness cabling. Transmission of individual thermocouple data to the central control unit would require many individual cables and so, due to weight restrictions, measurements are arranged before transmission over a single heavy duty cable to the central control unit. Not only does this preclude the determination of a detailed picture of the engine gas temperature, which could indicate potential engine problems, but also prevents the diagnosis of individual sensor faults and/or de-calibration. For vibration sensor systems, used extensively for monitoring of airframe and engine structures (particularly rotorcraft), the connection and lead-out systems are complex and highly tailored to the aircraft. This is compounded by the need for multiple sensor arrays. Consequently there is a weight penalty associated with these systems as well as a complex design process.
The use of wireless technology to create a wireless instrumentation system could substantially increase the complexity of the data that could be sent to the engine control unit and hence enable more sophisticated engine health monitoring. Furthermore, replacing cables with wireless transmissions will reduce the monitoring system weight and lead to improved fuel efficiency and reduced carbon emissions. On-line statistical analysis if data using wireless system could permit a clearer understanding of engine/aircraft health. The proposed system will allow condition-based maintenance, whereby maintenance can be scheduled according to actual wear and usage rather than fixed intervals, thereby reducing through-life costs.
In addition, a wireless system could allow for the sensors in the network to communicate their "health metrics" with each other, in turn allowing fault and drift detection to be identified and possibly corrected for in the control systems. This would give much greater confidence in the accuracy of the measured temperature and vibration patterns and could, potentially, allow the engine to run with less safety margin. Therefore the engine will be more efficiently. (with similar benefits on fuel consumption and emissions.)
However, embedding wireless technology into an aerospace or industrial gas turbine will have some very significant challenges to overcome, particularly for aero-engines which require a very high degree of safety assurance and certification. With regard to temperature measurement, for example, the temperatures outside the casing of the engine can reach in excess of 250C, precluding the use of most conventional silcon-based electronic systems. Moreover, maintaining the integrity of an RF signal transmission in an environment that is largely composed of metal whilst not interfering with )or being interfered by) other electronic equipment will present major hurdles.
Powering the sensors also presents a significant challenge as battery power is not appropriate, so some means of energy harbesting will be required. However, if these hurdles can be overcome, the benefits to engine management will be significant and could also pave the for use with other types of engine sensors such as tip clearance and speed sensors.
The proposed research will aim for breakthroughs in two domains: