High-speed Visualisation of Methanol Sprays under Flash Boiling Conditions

Motivation: Methanol is widely considered as a promising route to carbon reduction for maritime applications as a drop-in fuel to meet future IMO targets.Low boiling point of methanol at 338 K can contribute to flash boiling and atomisation at the injector leading to flash boiling and unpredictable fuel spray behaviour.Understanding the influence of the degree of superheat upon the spray characteristics is key to the optimisation of the combustion system. Aim:To conduct an experimental study to examine the spray characteristics of the Sandia National Laboratories, Engine Combustion Network (ECN) standard multi-hole injector (spray G) under flash boiling conditions.The eight hole ECN injector chosen has a wide cone angle, advantageous for larger bore engines.Methodology: Experiments were performed in an optically accessible sealed chamber at gas pressures below ambient conditions.Methanol between 50-200 bar was precisely metered by a syringe pump.The injector temperature was controlled at 363 K by a heating jacket.Chamber wall (and gas) temperatures were controlled to 333 K. ECN standard test conditions G2 and G3 were studied.High-speed shadowgraphy images were captured using a Phantom TMX 5010 and long-range microscope (K2 Infinity) and back lit LED illumination.Image processing using in-house code was used to measure spray penetration, cone angle and maximum width of spray envelope.