Analyzing the Interaction of Vortex and Gas–Liquid Interface Dynamics in Fuel Spray Nozzles by Means of Lagrangian-Coherent Structures (2D)

Predictions of the primary breakup of fuel in realistic fuel spray nozzles for aero-engine combustors by means of the SPH method are presented. Based on simulations in 2D, novel insights into the fundamental effects of primary breakup are established by analyzing the dynamics of Lagrangian-coherent structures (LCSs). An in-house visualization and data exploration platform is used in order to retrieve fields of the finite-time Lyapunov exponent (FTLE) derived from the SPH predictions aiming at the identification of time resolved LCSs. The main focus of this paper is demonstrating the suitability of FTLE fields to capture and visualize the interaction between the gas and the fuel flow leading to liquid disintegration. Aiming for a convenient illustration at a high spatial resolution, the analysis is presented based on 2D datasets. However, the method and the conclusions can analoguosly be transferred to 3D. The FTLE fields of modified nozzle geometries are compared in order to highlight the influence of the nozzle geometry on primary breakup, which is a novel and unique approach for this industrial application. Modifications of the geometry are proposed which are capable of suppressing the formation of certain LCSs, leading to less fluctuation of the fuel flow emerging from the spray nozzle.