Study of Solid Propellant Combustion and Aluminum Particles at High Pressure
Open Access
- Author:
- Hillstrom, Alexander
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 16, 2023
- Committee Members:
- Robert Francis Kunz, Program Head/Chair
Richard A Yetter, Thesis Advisor/Co-Advisor
Samuel Grauer, Committee Member - Keywords:
- Solid Propellant
Ammonium Perchlorate
Composite Propellant
High Pressure
Combustion
High Pressure Combustion
Aluminum
Aluminum Particles
Aluminum Combustion
AP
APCP - Abstract:
- Ammonium perchlorate's burning rate as a function of pressure has an exponent break around 4000 psi where the pressure exponent becomes greater than 1. This causes AP to be highly sensitive to pressure fluctuations that can damage or destroy ammonium perchlorate composite propellant-based solid rocket motors. Studies conducted on AP at these high pressure are few and there is a lack of direct qualitative data due to the challenges posed by the high-pressure environment and optical window structural limitations. This has left the cause exponent break mechanism unknown and difficult to study. The High-Pressure Combustion Lab has built an Ultra-High Pressure Optical Chamber (UHPOC) that allows for optical measurements at these higher pressure regimes. Testing visual measurement techniques using the UHPOC and a telescope zoom lens to take detailed images of the propellant surface during the burn was conducted. Non-aluminized propellant and aluminized propellant samples were tested to observe the mechanisms of aluminum particle combustion in a propellant at high pressures and the behavior of the propellant past the exponent break region. \par At atmospheric, detailed high-speed images on the propellant surface were obtained using a high-powered lamp to light the surface brighter than the flame. At higher pressures, however, the luminosity of the flame was significantly greater than the lamp, creating shadow images of the propellant. Binder agglomerates were observed coming off the surface which increased in size and magnitude as the pressure increased. This is attributed to AP decomposition becoming the dominant burning rate mechanism which burned faster than the surrounding binder as has been observed from previous studies and numerical models. This leaves the binder only partially pyrolyzed, forming the agglomerates which detached from the surface. Aluminum particles were found to ignite at all pressures with the binder agglomerating the same amount in both aluminized and non-aluminized samples. Atmospheric tests show aluminum particles with detached flames and high-pressure tests show aluminum particles with surface flames.