Reukers, Rachel (2024) Air Properties Measurements Using Tunable Diode Laser Absorption Spectrometer. [USQ Project]
Abstract
Ice Crystal Icing (ICI) is a phenomenon where small ice crystals enter aircraft engines and accrete on the surface of key components. This can have damaging effects to the engine which, in some cases, causes engine power-loss. Unfortunately, modern ice sensors on aircraft are not capable of detecting these small ice particles. Therefore, current methods of preventing ICI-related power-loss events involve avoiding flight areas where ICI is likely to occur. This is not an effective solution as it increases flight time and costs, and does not provide an accurate prediction of if ICI is likely to occur. Obviously, there is a need for a robust, non-intrusive method to measure the concentration of small ice crystals during flight, to allow real-time updates on if ICI is likely to occur. Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a measurement technique which is capable of simultaneously measuring the temperature, pressure and concentration of a single gas with a laser. This thesis demonstrates the application of TDLAS in the measurement of the temperature, pressure and concentration of water vapour, and small ice crystals for the application as an on-board aircraft ICI detection device. It is expected that TDLAS can be used to measure ice crystal concentration and warn pilots of the potential of ICI.
The TDLAS method was first assessed for local conditions where the humidity, pressure and temperature of the water vapour in the air in a controlled laboratory was determined. These TDLAS results were compared to readings from established measuring devices to determine the accuracy. It was found that the errors for the TDLAS results were varied and ranged from 2.84%-98.09%. Overall, this shows that the results were poor. However, from further investigation it was determined that the likely cause of this inaccuracy was the quality of the data that was collected.
Next the TDLAS method was assessed for gas cell conditions where the concentration, pressure and temperature within a controlled gas cell at varying conditions was deter- ii mined. These TDLAS results were compared to readings from established measuring devices. It was found that the errors were large, with the smallest error being 43.82%. This was determined to be due to, both the gas cell not being able to hold low pressures for the length of the experimental reading, and the use of direct detection in place of balanced detection.
Finally, the TDLAS method was assessed for the measurement of the concentration of ice crystals in the USQ Icing Wind Tunnel. It was found that there is a clear correlation between the output signal and the concentration of ice particles due to the scattering of the laser. This shows that TDLAS may be an effective device for ICI detection; however, further research and testing is required to investigate this relationship before it can be used on aircraft.
Overall, it can be seen that while the results of the first two experiments for measuring water vapour were poor, TDLAS shows promise as an effective technique for measuring ice particles. In future, balanced detection should be used to increase the quality of the data and therefore the accuracy of the results. Additionally, the use of TDLAS for detection of ice particles should be researched further to determine the details of its implementation.
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| Item Type: | USQ Project |
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| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -) |
| Supervisors: | Saleh, Khalid |
| Qualification: | Bachelor of Engineering (Honours) (Mechanical) |
| Date Deposited: | 17 Mar 2026 05:46 |
| Last Modified: | 17 Mar 2026 05:46 |
| Uncontrolled Keywords: | Ice Crystal Icing (ICI); aircraft engines; Tunable Diode Laser Absorption Spectroscopy (TDLAS) |
| URI: | https://sear.unisq.edu.au/id/eprint/53155 |
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