Researchers from the University of British Columbia (UBC) in Okanagan have improved the real-time response of aircraft ice-sensors. With an embedded antenna, the enhanced sensors can now immediately identify two types of crucial aviation data: ice accumulation and melting rate.

Currently, ice detection on aircraft is performed in one of two ways: with an old-fashioned eye-check, or with impedance sensing. Impedance sensing requires the build-up and then melting of the deposited ice before it can be detected.

The UBC system removes the reliance on visual confirmation and the need for liquid water to sense ice buildup, according to lead researcher and UBC Assistant Professor Mohammad Zarifi.

"This allows for detection far before the pilot could visually determine if ice is present," Zarifi told Tech Briefs.

(In a below video, see how Glenn Research Center used cameras to examine how ice build-up impacts an aircraft engine.)

By incorporating an antenna into the sensor, the results from the UBC-developed device can be shared in real-time with the operator in order to address any build-up.

The microwave sensor is, in fact, an optical nanostructure known as a split-ring resonator (SRR), operating at 5.82 GHz. The sensor, with built-in heating capabilities, effectively distinguishes between water and ice by detecting changes in the dielectric properties on or around its surface.

Water stores a greater amount of electrical energy than ice, and an SRR is especially equipped to measure the two specific permittivity levels.

Research related to the technology was published in the journal Applied Materials and Interfaces . The study, led by Prof. Zarifi, demonstrated the effectiveness of SRRs as ice detection sensors for applications where ice and frost are of great interest, such as on aircraft, roads, or walkways.

The patented sensor, which includes a protective layer, is now being tested for approval by the aviation industry. The UBC team also recently announced funding from Canada's Department of National Defense, which will enable the researchers to continue development

Zarifi is also collaborating with a number of wind turbine companies to adapt the sensors into wind farms.

Because the technology can sense salty ice, which freezes at colder temperatures, the device additionally may help to detect accumulation on oil rigs and marine infrastructure.

In a short interview with Tech Briefs below, Prof. Zarifi explains why the device has caught the attention of the aviation and renewable-energy industry alike.

Tech Briefs: An early press release from UBC  said that you received a great deal of interest from the aviation and renewable-energy industries, based on your initial findings. Can you say more about this? What was of interest to the aviation and renewable energy industries? And how did their reaction then inform the next step of your research?

Prof. Mohammad Hossein Zarifi: The initial interest received on our ice sensing device has come from applications where the aerodynamic properties of a structure is of extreme importance. Small changes to the shape of an aircraft wing or wind turbine blade due to ice formation can lead to drastic impacts on the lift or power generated by these structures.

Future work in the aerospace industry on this ice sensor will be to enhance the sensitivity of the device to ice formation in the presence of anti-icing fluids which are commonly sprayed to reduce the likelihood of an icing event.

Tech Briefs: What about with wind turbines?

Prof. Mohammad Hossein Zarifi: Ice detection on wind turbines is performed differently. The engineer monitoring the turbine can predict ice formation due to a drop-off in power production compared to the expected production at the same wind speeds. These sensors would have the capability to detect ice far before the power generation is impacted and allow ample time for the engineer to turn on de-icing systems. Based on information we have received from engineers in the wind industry, we believe the next step is to package the device and implement it in the field to perform further characterization and prepare it for industrial application.

Tech Briefs: What is your sensor able to detect, and how is the sensor’s information more valuable than the current detection options available on today’s aircraft?

Prof. Mohammad Hossein Zarifi: Our sensor is able to detect ice formation far before you can see it occurring on a surface. We are also able to extract information such as ice thickness and rate of deposition. This is valuable because it provides early warning to pilots who are experiencing an in-flight icing event, allowing them to activate anti-icing systems or simply change altitude to avoid the conditions.

Indication of ice thickness is important to people working on wind turbines from multiple reasons. First of all being that if you are working underneath the turbine, you want to be certain a thick sheet of ice isn’t going to fall off and possibly injure somebody. Another reason for accurate ice-thickness detection is because it can inform the engineer how to pitch the turbine blades to maximize power output during an icing event.

Tech Briefs: What applications are possible once you’re able to incorporate an antenna into the sensor?

Prof. Mohammad Hossein Zarifi: Recently, we have been investigating the use of antennas as the sensor. We are interested in using antennas for ice detection because they could significantly decrease the complexity of arraying the sensors. If we can implement an array of transmitting antennas, operating at different frequencies, and have the data transmitted to a single receiving antenna, the centralization and processing of the data is significantly simplified. This has applications in the case of needing to perform ice sensing over a large surface.

Tech Briefs: What’s next? What are you working on now?

Prof. Mohammad Hossein Zarifi: The next step in this project is to package the sensor and implement it in the field. We also need to further investigate methods that will allow us to perform detection in the presence of anti-icing materials for aerospace applications.

It’s all very exciting because we have had such an influx of interest from a variety of industries and so we look forward to meeting the unique challenges imposed by each application. Whatever the challenges are, extreme environmental conditions, sea spray, anti-icing materials, or simply complex aerodynamic structures, we believe we are capable of implementing successful ice sensors.

The research was funded by a National Sciences and Engineering Research Council of Canada Discovery Grant, Mitacs Accelerate Grant, and grants from the Canada Foundation for Innovation, and the Canadian Department of National Defense.

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