Leigh Nash

ELLIPSOMETRIC MEASUREMENTS OF THE THERMAL STABILITY OF ALTERNATIVE FUELS

Thermal stability is an important characteristic of alternative fuels that must be evaluated before they can be used in aviation engines. Thermal stability refers to the degree to which a fuel breaks down when it is heated prior to combustion. This characteristic is of great importance to the effectiveness of the fuel as a coolant and to the engines combustion performance. The thermal stability of Sasol IPK, a synthetic alternative to Jet-A, with varying levels of naphthalene has been studied on aluminum and stainless steel substrates at 300 to 400 °C. This was conducted using a spectroscopic ellipsometer to measure the thickness of deposits left on the heated substrates. Ellipsometry is an optical technique that measures the changes in a light beams polarization and intensity after it reflects from a thin film to determine the films physical and optical properties. It was observed that, as would be expected, increasing the temperature minimally increased the deposit thickness for a constant concentration of naphthalene on both substrates. The repeatability of these measurements was verified using multiple trials at identical test conditions. Lastly, the effect of increasing the naphthalene concentration at a constant temperature was found to also minimally increase the deposit thickness.

Shock Tube Ignition and CH4 Time-Histories during Propanal Oxidation

Propanal is an aldehyde intermediate formed during hydrocarbon combustion process. In this paper, we provide ignition delay time measurements behind reflected shock waves for stochiometric (Φ = 1) mixtures of propanal (CH3CH2CHO) and oxygen (O2) in argon bath gas at temperatures of 1100 < T < 1500 K and pressures around 1 atm. The measurements were conducted using the kinetics shock tube facility at UCF. The results were compared to data available in the literature as well as the predictions of three different aldehyde kinetic models. In addition, we used the laser absorption diagnostics for measuring methane (CH4) time-histories behind the reflected shock waves using a continuous wave distributed feedback interband cascade laser centered at 3403.4 nm. Methane concentration time histories were obtained for pyrolysis of propanal at 1300 K and around atmospheric pressures.

Thermal Stability Measurement of Alternative Jet Fuels Using Ellipsometry

Thermal stability is an important characteristic of alternative fuels that must be evaluated before they can be used in aviation engines. Thermal stability refers to the degree to which a fuel breaks down when it is heated prior to combustion. This characteristic is of great importance to the effectiveness of the fuel as a coolant and to the engine’s combustion performance. The thermal stability of Sasol IPK, a synthetic alternative to Jet-A, with varying levels of naphthalene has been studied on aluminum and stainless steel substrates at 300 to 400 °C. This was conducted using a spectroscopic ellipsometer to measure the thickness of deposits left on the heated substrates. Ellipsometry is an optical technique that measures the changes in a light beam’s polarization and intensity after it reflects from a thin film to determine the film’s physical and optical properties. It was observed that, as would be expected, increasing the temperature increased the deposit thickness for a constant concentration of naphthalene on both substrates. The repeatability of these measurements was verified using multiple trials at identical test conditions. Lastly, the effect of increasing the naphthalene concentration at a constant temperature was found to also increase the deposit thickness.Copyright

Jet Fuel Thermal Stability Investigations using Ellipsometry

Jet fuels are typically used for endothermic cooling in practical engines where their thermal stability is very important. In this work the thermal stability of Sasol IPK (a synthetic jet fuel) with varying levels of naphthalene has been studied on stainless steel substrates using spectroscopic ellipsometry in the temperature range 385-400 K. Ellipsometry is an optical technique that measures the changes in a light beam’s polarization and intensity after it reflects off of a thin film to determine the film’s thickness and optical properties. All of the tubes used were rated as thermally unstable by the color standard portion of the Jet Fuel Thermal Oxidation Test, and this was confirmed by the deposit thicknesses observed using ellipsometry. A new amorphous model on a stainless steel substrate was used to model the data and obtain the results. It was observed that, as would be expected, increasing the temperature of the tube increased the overall deposit amount for a constant concentration of naphthalene. The repeatability of these measurements was assessed using multiple trials of the same fuel at 385 K. Lastly, the effect of increasing the naphthalene concentration in the fuel at a constant temperature was found to increase the deposit thickness.