Recent experimental and numerical studies of nozzle cavitation have revealed that dissolved non-condensable gases can play a substantial role in determining both the degree of cavitation and the morphology of the vapor field. These phenomena are currently not well understood, and are challenging to simulate. A wide variety of physical submodels are used to model cavitation, yet the influence of non-condensable gases on the accuracy of these models has not yet been investigated, owing to the lack of available experimental data. To address this problem, new x-ray fluorescence measurements were performed at the 7-BM beamline of the Advanced Photon Source (APS) at Argonne National Laboratory. The fluorescence measurement was able to separate the contribution of dissolved gas and cavitation on the total line of sight void fraction. We consider the simplified case of a submerged cavitating nozzle with a sharp inlet and fixed diameter of 500 micron. Cavitation of a gasoline fuel surrogate was simulated with a compressible homogeneous relaxation model (HRM). Two implementations are considered, using Large Eddy Simulation to model turbulence in three-dimensional geometries. A range of conditions are considered, covering both incipient and strongly cavitating conditions, with and without dissolved gas in the fuel. A quantitative comparison between the simulations and line-of-sight x-ray measurements is made by projecting the volume fractions of cavitation vapor and non-condensable gas onto a plane. For the first time, both the concentration of dissolved gas in the fuel and the void fraction due to cavitation can be simultaneously validated.
Validation of Cavitation Simulations in Submerged Nozzles
BATTISTONI, MICHELE;
2015
Abstract
Recent experimental and numerical studies of nozzle cavitation have revealed that dissolved non-condensable gases can play a substantial role in determining both the degree of cavitation and the morphology of the vapor field. These phenomena are currently not well understood, and are challenging to simulate. A wide variety of physical submodels are used to model cavitation, yet the influence of non-condensable gases on the accuracy of these models has not yet been investigated, owing to the lack of available experimental data. To address this problem, new x-ray fluorescence measurements were performed at the 7-BM beamline of the Advanced Photon Source (APS) at Argonne National Laboratory. The fluorescence measurement was able to separate the contribution of dissolved gas and cavitation on the total line of sight void fraction. We consider the simplified case of a submerged cavitating nozzle with a sharp inlet and fixed diameter of 500 micron. Cavitation of a gasoline fuel surrogate was simulated with a compressible homogeneous relaxation model (HRM). Two implementations are considered, using Large Eddy Simulation to model turbulence in three-dimensional geometries. A range of conditions are considered, covering both incipient and strongly cavitating conditions, with and without dissolved gas in the fuel. A quantitative comparison between the simulations and line-of-sight x-ray measurements is made by projecting the volume fractions of cavitation vapor and non-condensable gas onto a plane. For the first time, both the concentration of dissolved gas in the fuel and the void fraction due to cavitation can be simultaneously validated.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
