A Novel Quasi-Dimensional Model for Transient Mixing Prediction in Two-Phase Multicomponent Sprays under Flash-Boiling Conditions

A novel one-dimensional multiphase and multicomponent spray model - hereafter referred to as the Kattke-Weigand model - has been developed to predict the penetration length of both vapor and liquid gasoline sprays under flash-boiling conditions, such as superheated injections. Its formulation is based on mass and momentum equations for unsteady jets and is therefore capable of capturing dynamic effects. Experiments were conducted in a constant volume chamber using various ambient and fuel temperature conditions and a six-hole GDI injector with a separated jet. Macroscopic spray parameters were extracted from the measurements to verify the model's ability to predict both liquid and vapor penetration length and the corresponding spray angles.

Apart from the separated jet of the injector used, the other five jets interact strongly with each other under flash boiling conditions, resulting in spray collapse, and thus affecting spray characteristics. The prediction of collapse is very sensitive to calculations of vaporization and air entrainment. Since these submodels cannot be validated directly, a calibration method was developed, that is based on a three-dimensional reconstruction of all fuel sprays of the injector used. For this purpose, all optical measurements performed in the constant volume chamber are utilized. As a result, a three-dimensional representation of the spray collapse can be calculated from the combination of the 3D spray reconstruction and the entrainment and vaporization submodels. The validation of the collapse leads indirectly to the calibration of the entrainment and vaporization submodels in the Kattke Weigand model. Latter is applied to gain a deeper understanding of the interaction between spray collapse and both liquid and vapor phase penetration.