Characterization of High Pressure Natural Gas Injections for Stratified Operation of a Spark Ignited Engine by Simultaneous Fuel Concentration and Air Entrainment Measurements - Friedrich, Wolfgang; Grzeszik, Roman; Helmich, M; Bossmeyer, Thomas; Wensing, Michael (18th Laser Lisbon Int. Symposium on Application of Laser Imaging Techniques to Fluid Mechanics, 2016)