Search Results

Butanol has been proposed as a biologically derived fuel that has significant advantages over ethanol in terms of energy density and miscibility with diesel. This has generated the need to study separately and evaluate comparatively the in-engine combustion of the four isomers of butanol. Previous studies on the combustion of butanol isomers in laminar premixed flames have shown that while the isomers exhibit several similar combustion characteristics, including adiabatic flame temperature and flame speed, pollutant formation is highly dependent on the precise chemical structure of each isomer. The objective of this study is to build on these findings by investigating the effect of three of the four butanol isomers (n-butanol, isobutanol, and sec-butanol) on engine performance and emissions. The three isomers were blended as 30% butanol and 70% gasoline on a mass basis. These fuel blends were tested in a single-cylinder port-injection spark-ignition engine.

Butanol produced from agricultural sources is emerging as a potentially renewable bio-fuel. In this work, three bio-butanol fuel utilization technologies were considered to evaluate its potential: Electrostatic sprays, non-premixed flames and kinetic modeling. Butanol electrospray phenomenology was investigated through high-speed visualization and compared with the corresponding electrosprays of ethanol and heptane. Electrospray structure was probed using Phase Doppler Anemometry and both droplet size and velocity measurements were obtained for sprays of the three fuels under consideration. Particular emphasis was placed on the determination of the dependence of droplet size and velocity on mass flow rate and applied electric field. These results indicated an unstable, and polydisperse electrospray behavior and secondary droplet break-up due to high Weber numbers was investigated. Non-premixed flames were studied in a counter-flow burner configuration.

An experimental investigation was conducted using a Ford single-cylinder spark-ignition research engine to compare the performance and emissions of neat n-butanol fuel to that of gasoline and ethanol. Measurements of brake torque and exhaust gas temperature along with in-cylinder pressure traces were used to study the performance of the engine and measurements of emissions of unburned hydrocarbons, carbon monoxide, and nitrogen oxide ere used to compare the three fuels in terms of combustion byproducts. It was found that gasoline and butanol are closest in engine performance with butanol producing slightly less brake torque. Exhaust gas temperature and nitrogen oxide measurements show that butanol combusts at a lower peak temperature. Of particular interest were the emissions of unburned hydrocarbons which were between two and three times those of gasoline suggesting that butanol is not atomizing as effectively as gasoline and ethanol.

A single nozzle port fuel injector was modified to apply electrostatic charge to the fuel stream, with the intention of studying electrostatically assisted sprays in a practical, port-injected engine. The modifications were kept external to the injector and involved placing an electrode and insulating liner over the tip of the injector. The performance of the modified injector, which combined pressure driven and electrostatic atomization, was characterized in three phases: the injector sprays themselves were studied, combustion of charged fuel droplets was studied, and the injector was installed and tested on a single cylinder spark ignition engine. In the first phase, Fraunhofer diffraction measurements of droplet size, and particle image velocimetry measurements of droplet velocity were performed. The charge transferred by the sprays was measured using an electrometer, and typical forces exerted on droplets in the sprays were estimated.

The current work uses a method developed by the authors for both combustion irreversibility and working medium availability computations in a high speed, naturally aspirated, four stroke, internal combustion engine cylinder. The objective of the study was to extrapolate already published results of the second-law analysis of diesel engine operation by studying parametrically the effect of main operating parameters such as engine speed of rotation, injection timing, and fuel composition. Extensive experimental data were available for the case of dodecane injection, which were used for the determination of the fuel reaction rate. Computationally, the same reaction rates were used for methane and methanol injection. The production rate of irreversibility during combustion was analytically calculated as a function of the fuel reaction rate with the combined use of first and second-law arguments and a chemical equilibrium hypothesis.