Microwave Enhancement of Composite Solid Propellant Flames
Abstract
The aim of this project is to investigate strategies with which to efficiently deposit microwave energy to the flame structure of a propellant to enable dynamic control of propellant energy release rate and new functionalities. Specifically, techniques to interface microwave energy with either (1) the gas phase flame or (2) the propellant condensed phase are explored. Microwave energy deposition to the gas phase was found to be possible by either (1) increasing the electron number density of the gas phase flame in order to establish within the flame a weak microwave induced plasma (WMIP) or (2) to deposit energy to high-temperature metal oxide combustion products, whose dielectric loss increases exponentially with temperature (e.g. aluminum oxide). With respect to WMIP, it was found that doping of an energetic material with reagents producing strongly electro-positive species (i.e. alkali metals in form of metal nitrates of sodium, potassium, or cesium) within the flame, were effective. Experiments conducted on composite solid propellant demonstrated throttling enhancement of burning rate by up to 60% at atmospheric pressure. Simulations of a 1-D planar flames show that electromagnetic shielding of the flame/s inner core can be significant and is exacerbated by high alkali concentrations (i.e. high electron number density). An optimum dopant level, relative to the size of the flame in order to achieve microwave field penetration of the flame core. A new two-photon laser induced fluorescence scheme with an order of magnitude improvement in signal to noise ratio was also demonstrated and used to explore the WMIP initiation process in propellants.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 03, 2021
- Accession Number
- AD1132528
Entities
People
- James B Michael
- Joel Lynch
- Keke Zhu
- Stuart J. Barkley
- Travis R. Sippel
Organizations
- Iowa State University