Analyzing Primary Breakup in Fuel Spray Nozzles by Means of Lagrangian-Coherent Structures

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 the simulations, novel insights in the fundamental effects of primary breakup are established by analyzing the dynamics of Lagrangian-Coherent Structures (LCS). An inhouse 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 Lagrangian-Coherent Structures (LCS). It is demonstrated that FTLE fields are useful for understanding the interaction between the gas and the fuel flow leading to liquid disintegration. The FTLE fields of modified nozzle geometries are compared to each other 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 to suppress the formation of certain LCS leading to less fluctuation of the fuel flow emerging from the spray nozzle.