Class
Article
College
College of Engineering
Department
Mechanical and Aerospace Engineering Department
Faculty Mentor
Nicholas Roberts
Presentation Type
Poster Presentation
Abstract
The exhaust plumes of rocket and jet propulsion systems feature highly-oxidizing, potentially corrosive, extremely high temperature flows. The hostility of these environments makes obtaining in-situ thermal flow measurements extremely difficult. The conventional method for these measurements uses Gardon heat-flux gauges requiring complex and highly invasive installations which cannot be used for flight applications. More recent work has used fiberoptic cable installations to sense internal flow conditions of hybrid and solid fuel rockets. In this configuration, fiber optic cables inserted through the fuel and into the flow are consumed by the flame as the fuel surfaces pyrolyze, but the cable tips remain at the solid fuel inner boundary and continue to optically transmit optical signals from the flame zone to external spectrometers. Assuming a near-black-body radiation profile, the data are curve fit to Planck’s black-body radiation law, and Wien’s displacement law allows the mean combustion temperature to be estimated. Local maxima in the associated spectrum also appear to correlate with combustion species theoretically predicted to exist in the exhaust plume. This approach is minimally invasive and could potentially be adapted for flight applications. This project will apply these fiber-optic methods for use on fixed geometry configurations such as hard-walled combustion chambers and exhaust nozzles. Key questions include survivability of the sensing end of the fiber optic cable and identifying the appropriate cable type for light transmissibility and appropriate frequency response over the required optical bandwidths. Techniques for estimating the optical response function and using this function to sense the plume stagnation temperature and exhaust species will be also developed and evaluated. The system will be tested with a legacy USU hybrid rocket thruster using ABS plastic as fuel and gaseous oxygen as oxidizer. For these tests the fiber-optic cable will be inserted into a fixed geometry fairing mounted downstream of the nozzle. All collected spectrometer data will be analyzed and compared to flame temperature and exhaust species from equilibrium chemistry calculations and other combustion models.
Location
Logan, UT
Start Date
4-12-2023 2:30 PM
End Date
4-12-2023 3:30 PM
Included in
In-Situ Optical Measurements of Combustion Plumes
Logan, UT
The exhaust plumes of rocket and jet propulsion systems feature highly-oxidizing, potentially corrosive, extremely high temperature flows. The hostility of these environments makes obtaining in-situ thermal flow measurements extremely difficult. The conventional method for these measurements uses Gardon heat-flux gauges requiring complex and highly invasive installations which cannot be used for flight applications. More recent work has used fiberoptic cable installations to sense internal flow conditions of hybrid and solid fuel rockets. In this configuration, fiber optic cables inserted through the fuel and into the flow are consumed by the flame as the fuel surfaces pyrolyze, but the cable tips remain at the solid fuel inner boundary and continue to optically transmit optical signals from the flame zone to external spectrometers. Assuming a near-black-body radiation profile, the data are curve fit to Planck’s black-body radiation law, and Wien’s displacement law allows the mean combustion temperature to be estimated. Local maxima in the associated spectrum also appear to correlate with combustion species theoretically predicted to exist in the exhaust plume. This approach is minimally invasive and could potentially be adapted for flight applications. This project will apply these fiber-optic methods for use on fixed geometry configurations such as hard-walled combustion chambers and exhaust nozzles. Key questions include survivability of the sensing end of the fiber optic cable and identifying the appropriate cable type for light transmissibility and appropriate frequency response over the required optical bandwidths. Techniques for estimating the optical response function and using this function to sense the plume stagnation temperature and exhaust species will be also developed and evaluated. The system will be tested with a legacy USU hybrid rocket thruster using ABS plastic as fuel and gaseous oxygen as oxidizer. For these tests the fiber-optic cable will be inserted into a fixed geometry fairing mounted downstream of the nozzle. All collected spectrometer data will be analyzed and compared to flame temperature and exhaust species from equilibrium chemistry calculations and other combustion models.