Correlation of Internal Flow and Spray Breakup for a Fuel Injector Used in Ship Engines

Paper in proceeding, 2013

A full-scale fuel injector for a large marine engine has been studied inside an optically accessible, high pressure spray research chamber. The injector tip was made of quartz and it had two holes oriented nearly normal to the injector centerline. Realistic nozzle internal flow passages were used, but a Scania XPI injector body delivered the fuel. The injector body was mounted in the side of the high pressure and temperature spray chamber at Chalmers (one of the windows was replaced), and the jets it produced pointed downward into a spray catch facility. Commercially available Diesel fuel was provided by an accumulator at 110 bar delivery-line pressure. The spray was ejected into flowing air at room temperature and pressures of 10 bar (to achieve relevant cavitation numbers), with injection durations on the order of hundreds of ms. The steady flow portion of the injection process was studied. Internal flow was observed using white light imaging, while spray breakup dynamics were observed using a Ti:sapphire laser-based, time gated ballistic imaging system. Spray dynamics were also studied using a spray impingement measurement inside the chamber. The internal and external (near field breakup) flows seemed to be correlated. Under high levels of cavitation the spray appears to break up similar to an aerated spray, producing a dense field of large primary drops at a fairly large spray angle. Under non-cavitating conditions the spray seems to break up similar to a more classical Diesel injector; including such features as an intact core, surface waves, some bag breakup, and what appears to be air entrainment.