Date of Award

2022-12-01

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Advisor(s)

Evgeny Shafirovich

Abstract

Chemical heat integrated power systems are of great interest for space missions where solar energy, nuclear energy, and batteries are not available or are not practical to use. A new concept of a power system is a metal combustor coupled with a chemical oxygen generator, where the generated oxygen infiltrates through the metal powder or combustion products. The combustion of lithium and magnesium powders under these conditions has not been studied yet. The present work investigates combustion of magnesium powder and stabilized lithium metal powder (SLMP) ignited by a laser inside a closed chamber filled with O2 or CO2. It also includes experimental studies on the reactions of SLMP with O2 and CO2 by using non-isothermal and isothermal methods of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The combustion of Mg and Li powders in vertical quartz tubes at natural infiltration of oxygen has been demonstrated at atmospheric or lower pressure. It has been shown that laser ignition of either powder leads to a counterflow combustion wave at low conversion. This process is followed by a backward coflow combustion wave or, in some tests with Li, by a continued reaction of the entire sample. In CO2, self-sustained combustion did not occur, apparently because of formation of byproducts that hinder CO2 transportation to the reaction zone. During oxidation in both O2 and CO2 environments, Li powder reacted mainly after melting, leading to the formation of hollow spheres. Oxidation by O2 to Li2O involves transition from a slow to a faster stage, which is explained by formation and decomposition of Li2O2. In CO2, Li is first oxidized to Li2O, which is then converted into Li2CO3. High-pressure DSC has shown that the increase in pressure from 10 to 30 bar promotes the conversion of the sample into Li2CO3.

Language

en

Provenance

Received from ProQuest

File Size

76 p.

File Format

application/pdf

Rights Holder

Kevin Samuel Estala Rodriguez

Download

Share

COinS