Numerical Investigation of Various Atomization Models in the Modeling of a Spray Flame

Abstract

In modern aircraft and rocket engine combustors, the atomization characteristics of a fuel nozzle as defined by the spray dispersion angle, droplet-size and velocity distributions, and fuel vaporization play an important role in determining the combustor performance, e.g. the combustion efficiency, ignition and lean blowout conditions, exit temperature pattern, and emissions. The success of any spray calculation depends a great deal on the correct specification of the initial droplet conditions. However, the modeling of the atomization process is a very challenging task as it is influenced by a variety of factors: the aerodynamic liquid-gas interaction, the inner nozzle disturbances, the nozzle geometry, and the thermo-physical properties of fuel. So far in our previous spray computations, we have relied on either known experimental data or data generated from widely-used correlations in specifying the initial droplet conditions. In order to reduce some uncertainty associated with the specification of the initial droplet conditions, we have undertaken the task of integrating an atomization module into our spray calculation procedure of the national combustion code (NCC). The atomization module contains the following primary atomization models: (1) sheet breakup, (2) air blast, (3) blob jet, and (4) BLS (Boundary-Layer Stripping), together with the following secondary droplet breakup models: (1) Rayleigh-Taylor, (2) TAB (Taylor Analogy Breakup), and (3) ETAB (Enhanced Taylor Analogy Breakup). The paper provides complete details of various models contained in the atomization module. And it also summarizes the results from the study conducted to investigate the effect of various atomization models in the modeling of a spray flame.