<p dir="ltr">This work seeks to study a novel, actively cooled aerodynamic probe nacelle with integrated optics to enable short focal length laser diagnostics in high-temperature supersonic flows, especially relevant for Hot Jet wind tunnels. The nacelle has been designed to: i.) survive the thermal loads generated at Mach 6 and total conditions of 1700 K, 44 bar, and ii.) minimize the flow disturbance generated by the front bow shock. By enabling measurements at shorter focal lengths, higher irradiance is achieved at the focal point for the same laser power.</p><p dir="ltr">The thermal survivability of the nacelle is studied first via a 1D conjugate heat transfer model including effusion cooling effects. The coolant pressure predicted by the model is used as boundary condition in 3D Steady RANS numerical simulations, where spatially resolved cooling effectiveness contours are extracted. Flow distortion is also studied from the numerical simulations. Modelling accurately the effusion holes allows to study the coolant jets-bow shock interaction and its effect on the shape of the shock. The distance between the focusing lens and the bow shock is studied and compared to the focal length achieved if the optics were placed outside the facility. The shift in laser trajectory due to refractive index gradients across the flow is predicted using ray propagation models.</p><p dir="ltr">The cooling jacket of the nacelle is tested experimentally in an Open Jet wind tunnel at low supersonic (Mach~1.1), long duration, heated conditions. “In-situ” calibrated infrared thermography is used to obtain temperature and cooling effectiveness contours in the front faces and Atomic Layer Thermopiles (ALTPs) are used to measure heat flux and adiabatic heat transfer coefficient, enabling validation of the numerical models. High-frequency accelerometer data and Camera-Based vibrations data are collected to identify vibration frequencies and peak to peak amplitudes in the nacelle, allowing to correlate them with the momentum of the Open Jet and study their impact on the location of the focal point.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/27642975 |
| Date | 12 November 2024 |
| Creators | Ignacio Lasala Aza (20151309) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Optical_Probe_Nacelle_for_Short_Focal_Length_Diagnostics_in_High_Temperature_Supersonic_Flows/27642975 |
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