Comparison of Methanol and Gasoline Fuel Spray Vaporization Using Direct-Injection Technology

Considering the large opportunity to reduce net lifecycle carbon emissions through the use of renewable methanol, we address spray technologies needed to overcome the challenge of wall wetting and poor vaporization for methanol and the need for improved computational modeling of these processes. High-speed extinction imaging followed by computed tomography reconstruction is utilized to provide three-dimensional liquid volume fraction for reference fuel injectors, to be used for model validation activities. The first injector is the symmetric 8-hole Spray M injector for the Engine Combustion Network, and the second injector is an asymmetric 6-hole injector designed for lateral-cylinder mounting. The degree of plume interaction and vaporization are characterized at representative injection conditions, showing substantially higher concentrations of liquid for methanol than gasoline even with preheated fuel temperatures (90 degrees C). In light of higher injected mass requirements for methanol sprays in combustion applications due to its lower chemical enthalpy, an elevated injection pressure is explored to visualize their effects on spray morphology and improve our understanding of the accelerated evaporation from higher injection pressure. Differences between using collimated and diffuse lighting for extinction measurements are discussed along with the uncertainties associated with each diagnostic. The collimated light source provides higher fidelity optical thickness measurements compared to the diffuse light source but suffers from interference from vapor-phase beam steering. The beam steering effects creates difficulty on the determining the liquid boundary but has negligible impact on the total measured extinction at mild conditions.