OXIDATION OF HYDROCARBONS AND OXYGENATED FUELS WITH CHEMICAL SENSITIZATION BY OZONE/NOX/RADICALS

Abstract

This thesis aims to study the gas phase chemistry of hydrocarbons and oxygenated fuels and the chemical sensitization effects of O3/NOx/radicals on the fuel oxidation. The first part of this thesis focuses on the O3 and NOx sensitization on low and intermediate temperature fuel oxidation in homogenous reaction systems such as laminar flow reactor (LFR) and jet stirred reactor (JSR). Chapter 3 studies the ozone assisted low temperature oxidation of dimethyl ether (DME) in an LFR. The results reveal that ozone enhances DME oxidation at low temperatures and amplifies the uncertainties of some important pathways of DME oxidation. Chapter 4 and Chapter 5 examine the NO and NO2 sensitization effects on low and intermediate temperature n-pentane oxidation. Their distinct characteristics on inhibiting low temperature oxidation, suppressing the negative temperature coefficient effect, and prompting intermediate and high temperature oxidation are demonstrated. An improved NOx sensitized kinetic model for n-pentane is developed and validated.

The second part of this thesis emphasizes the effects of radical sensitization on the high temperature flame chemistry by measuring laminar flame speed in a low pressure flat flame system and a high pressure spherical bomb. Chapter 6 studies the high temperature chemistry of esters (methyl formate and methyl propionate) by using low pressure flat flames coupled with an electron-ionization molecular beam spectrometer (EI-MBMS) and by measuring high pressure spherical flames speeds. The models developed herein extended the knowledge of biofuel combustion chemistry. Chapter 7 studies the CH2O/HCO chemistry, including a recently discovered pathway of the prompt HCO dissociation by measuring the high pressure formaldehyde flame speed. The CH2O/HCO chemistry is updated in the Princeton high pressure mechanism (HP-Mech) and should be included in all the current C1-C4 combustion models. Chapter 8 studies the high pressure laminar flame speed of 1, 3-butadiene by using H2 and O2 sensitization. Experimental and modeling studies reveal that H2 and O2 sensitization in flames provides an important approach to identify the model uncertainties for flames.