Nitrate esters are a class of compounds with properties that make them effective components in rocket propellant fuels. As such, comprehensive knowledge of their combustion mechanisms are of great importance to the design and improvement of rocket propellants. Despite this impetus, the combustion mechanisms of many such propellants are either wholly incomplete or built upon outdated or inaccurate thermochemical and kinetic libraries. This issue largely stems from two factors: (1) limited understanding of which reactions are important to overall mechanism, and (2) a lack of reliable theoretical and experimental studies on the constituent reactions. Overcoming these two obstacles makes the construction of new propellant combustion models a highly complex and involved task. Often, many research groups work for many years to build a complete and thorough model for a single propellant. Accumulation of necessary data via these means is often tedious and inefficient. Modern theoretical electronic-structure and kinetic programs allow for the determination of very accurate thermochemical and kinetic parameters for significant combustion reactions. Building on this success, we are developing codes that automate the set-up and execution of these programs as well as the parsing of their output into thermochemical and kinetic databases. This talk will discuss the features of these automated codes in brief. However, it will primarily focus on the data that has been obtained for use in the construction of a comprehensive combustion model for ethylene glycol dinitrate (EGDN). Despite being a well-known propellant, there is little information regarding its combustion mechanism. Therefore we have tailored our efforts to best approach building such a mechanism from scratch. EGDN is a an excellent model system for building thermochemical and kinetic libraries for nitrate ester propellants since it (1) shares many structural similarities with other propellant species (e.g. nitroglycerin and pentaerythritol tetranitrate) and (2) and is of a size which makes many of its reactions amenable to high-level theoretical treatments. To date, many key EGDN combustion reactions have been identified. Using the automated codes discussed above, we have computed optimized equilibrium geometries, anharmonic vibrational frequencies, hindered rotor potentials, and energetics for all stationary points on the reaction surface and used this information in RRKM/Master-equation kinetic treatments.

Building rocket propellant combustion models from scratch via automated procedures

2019 Spring National Meeting

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