How RF Sensors Optimize Heat Transfer Tests in Gas Turbine Engines

Heat transfer tests, especially as related to turbine blade surface temperature, are among the most challenging measurements in gas turbine engines. Traditional temperature sensor technologies all suffer from crippling inefficiencies and limitations in the extreme environment of a gas turbine heat process or other area of the engine interior.

Optical technologies such as pyrometers and infrared cameras are known to be costly on a per-data-channel basis as well as inaccurate at higher temperatures.  Furthermore, any tech relying on infrared radiation will struggle to measure emissivity on reflective surfaces such as the metals within a turbine engine, making a near-black-body optical target necessary (which must also survive well inside the engine). Wired thermocouple sensor arrays also require complex, heavy wiring harnesses that are costly and difficult to deploy, often necessitating engine teardowns and machining of components to create holes for running wires.

Wireless RF Sensors Make Heat Transfer Tests Easy

A remotely operated, battery-free, passive RF temperature sensor is the perfect solution to the inaccuracies and inefficiencies of earlier solutions. Wireless sensor networks can acquire data and help you monitor heat transfer with fast deployment, more positional flexibility, and much lower sensor maintenance costs.  

Polymer-derived ceramic contact sensors (which double as both an RF resonator and an antenna) come in the form of tiny film patches that are smaller than a postage stamp. They’ll fit into really tight spaces that are tough to instrument with traditional sensors. Not only are compact films patches convenient and durable, but they’re also more precise instruments than pyrometers and IR cameras.

Here  are a few ways that RF sensors can optimize heat transfer tests for gas turbines:

• Rapid Multi-Sensor Deployment: Since these compact wireless sensors can be instrumented without an engine teardown, even in normally hard-to-reach spots, it’s much faster to deploy (and maintain) a multi-sensor array with dozens or even hundreds of data channels. A large number of channels routing data wirelessly into monitoring software will provide a more complete picture of heat transfer performance and a more accurate calculation of heat transfer coefficients than the limited number of data points that are feasible with other methods.
• The Accuracy of On-Blade Contact: Blade metal surface temperatures should always be tracked directly rather than using non-contact, optical, or gas flow measurements to infer blade temperature. RF sensors track subtle changes in the resonant frequency of the sensor (the resonator), which will gradually drop as the temperature in the sensor rises. The direct contact with the blade ensures the sensor will match the exact temperature of the blade surface.
• Real-Time Temperature Measurement: Wireless RF sensors are the only solution that can provide continuous, real-time temperature data throughout a thermal cycle (and even throughout the life of the engine). Unlike solutions that only identify the maximum temperatures experienced during engine tests, RF sensors can alert you to uneven spikes in temperature and display data on hotspots in any instrumented location, at any stage of the heat transfer test.
• Cost-Efficient Components: Durable, polymer-derived ceramic RF sensors are much less expensive per channel than full infrared camera implementation, and the bonding adhesive makes cost-effective deposition of the thin film RF sensors simple within the complex shape of a turbine engine. No pricey wiring, drilling, or engine modifications required.

The bottom line is that RF sensors will help you quickly and easily trend surface temperatures and calculate your heat transfer coefficient in real-time on rotating components. Ultimately, this will make it possible to improve cooling schemes and optimize the heat transfer performance of your cooling configuration while also providing valuable data for predicting component life.

Working on heat transfer tests? The team at Sensatek is eager to help you optimize your test measurements while minimizing the costs and time that these tests typically take. Contact us today to discover more about how our wireless, passive RF sensors can improve your tests.