Ignition studies of bio-based fuels for advanced combustion engines
As interest and use of bio-derived fuels continues to grow, there is a critical need to understand the fundamental chemistry involved in the combustion of these bio-based fuels. Fuel chemistry significantly affects ignition timing and pollutant emissions. Validated chemical models enable predictive simulations to be used in the design of advanced combustion engines employing new bio-fuels. The development of chemical kinetic mechanisms require experimental validation targets covering a wide range of conditions, including: temperature, pressure, dilution and stoichiometry.
This thesis focuses on ignition studies of bio-based fuels, aimed towards the validation of chemical kinetic mechanisms. In the first part, the low pressure shock tube located at the National University of Ireland–Galway (NUIG) was used to conduct experiments of n- and iso-propanol, two isomers of a three carbon alcohol. Experiments were conducted over a range of conditions, including temperatures from approximately 1350 to 2000K, a pressure of 1atm, equivalence ratios of 0.5, 1.0 and 2.0, and oxygen concentrations of 1.13 and 2.25%. Novel methods were used to compare the experimental data to simulations with a detailed kinetic mechanism developed at NUIG.
In the second part, studies have been conducted towards the development of an aerosol fueling system for a rapid compression machine (RCM) study the low temperature chemistry of low vapor pressure, involatile fuels, such as bio-derived methyl esters, the primary constituent of bio-diesels. This work included: modeling droplet evaporation to conduct a feasibility study of the concept, fabricating a system to generate a fuel-laden aerosol suspension with small enough droplet diameters to ensure evaporation, and exploring the machine charging process to prevent stratification during delivery of the aerosol. It was determined that at an initial temperature of 350 K and a pressure of 0.5 bar, n-dodecane droplets, a surrogate for methyl decanoate, as large as 8.5 &mgr;m can be vaporized before the bath gas reaches a temperature of 500 K, defined as the low temperature chemistry limit. An aerosol flow rate of greater than 20 LPM (ReRCM > 700) is needed in order to prevent stratification.
This manuscript discusses will discuss details of these experimental and computational studies.
0548: Mechanical engineering