Measurement of Solid Propellant Burning Rates Using Photodiode Arrays
Open Access
- Author:
- Stevens, Matthew
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Richard A Yetter, Thesis Supervisor
Kenneth Steven Brentner, Thesis Honors Advisor - Keywords:
- Solid Propellant
Solid Rocket Motor
Burning Rate
Solid Propellant Burning Rate
Combustion
Measuring Burning Rate - Abstract:
- The measurement of solid propellant burning rates provides critical information for the successful design of solid rocket motors. By knowing the burning rate of a propellant across a range of pressures, the mass flow through the motor can be determined through mass conservation. Typical burning rate determination methods require extensive preparation of propellant samples, significant post processing work, or a combination of both. This study focuses on the development of a photodiode array measurement system for tracking the burning surface of solid propellant in a strand burner. Pressures in the range of 100-1000psi were tested with both a heterogenous propellant, Advanced Solid Rocket Motor Propellant (ASRM), and a homogenous propellant, JA2. Tests were completed at The Pennsylvania State University’s High Pressure Combustion Laboratory (HPCL). A 16-element photodiode array was acquired and supporting circuitry and software was developed to process the output signals from the photodiodes and produce a burning rate. Final rates were very close to those determined using the more traditional camera-based method, with an average percent difference across all tests of 3.16%. ASRM propellant had slightly higher percent differences, with an average of 4.29% while the JA2 propellant had an average of 2.03%. The differences in flame structure of the JA2 and ASRM propellants are reflected in the outputs of the photodiodes, and the increased variation, or “flickering” of the ASRM is thought to be a potential cause of the increased percent differences. The JA2 was shown to exhibit an asymptotic decrease in radiance along the burning direction of its flame structure, while the ASRM had a more linear decrease. An amplification PCB was developed for the photodiodes along with MATLAB code to automatically process output data and determine burning rates. A linear actuator was acquired and mounted with an IR LED to simulate a burning surface for initial testing of the system. Various methods for determining burning rate from the photodiode outputs were compared. It was found that a threshold-based approach of the voltage outputs along with a regression line through the position-time plot of the burning surface provided the most accurate burning rates.