UNS: High Pressure Ring Contraction of Cyclic Hydrocarbons

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

1510039 (Brezinsky) This project studies the behavior of some basic fuels under high-pressure and high-temperature conditions (typical in engines and power plane combustors), such as how fast/slow the fuel molecules will be fragmenting or contracting. The results have the relevance on how soot particulates might form under these conditions, and thus help to develop cleaner combustion technology. Graduate students from under-represented groups will be involved in the research activities. The objective of the proposal is to measure the pressure-dependence of cyclization vs. beta scission branching fraction of midsize alkenyl radicals. Using a shock tube, the PI seeks to identify the shape and position of pressure-dependent uni-molecular fall-off curves that extend to the high pressures and also the often overlooked effect of pressure on the rate constant expressed through the activation volume. These fuels undergo increasing amounts of ring contraction (due to molecular caging effects) under the high-pressure and high-temperature conditions instead of fragmentation into smaller molecules, leading to increased soot and coke formation. In addition to ring contraction pyrolysis reactions, bimolecular oxidation reactions will have negative activation volumes which lead to a significant increase in the rate constant with pressure and, depending on polar interactions with surrounding molecules such as combustion generated water. The PI will investigate these mostly overlooked activation volume effects as well as the extended shape and position of the uni-molecular fall-off curves.