Breakup Characteristics Of A Liquid Jet In Subsonic Crossflow PDF Download

Inasmuch as power generation systems, in both avionic and stationary applications, are typically powered by liquid fuels, the process of liquid fuel/air mixture preparation plays a key role in combustion (i.e., fuel burning) of these systems. One of the most efficient liquid fuel/air mixture generation techniques in a combustion chamber is by injecting liquid fuel transversely into a gaseous crossflow (JICF). Amongst the various features of this type of flow-field, data describing the trajectory and breakup length of a transverse liquid jet is highly required for combustor design in order to prevent fuel impingement onto the combustor walls. More importantly, it is needed for predicting fuel distribution in a combustor, which directly affects droplets breakup, collision, evaporation, mixing rate with oxidants, and consequently the overall combustion efficiency of an engine. Due to the complexity associated with the theory behind a transverse liquid jet, a large body of investigations on its features is experimental; however, several experimental challenges such as the limitations in observing the dense spray region hinder the progress in understanding this topic. Moreover, the liquid jet's trajectory and its breakup length vary significantly with changing liquid properties, test/operating conditions and nozzle/injector internal geometries, leading to huge discrepancies between published results/predictions. In this thesis, therefore, a phenomenological investigation, by integrating both theoretical and experimental approaches, has been carried out to gain a more comprehensive understanding of the complex process of a transverse liquid jet in a gaseous crossflow. A mathematical method was adopted to develop a model for predicting the penetration of a liquid jet in a subsonic gaseous crossflow over a wide range of liquid properties and test/operating conditions. In the near field zone, a force balance was applied to a control-volume, and forces acting upon the liquid column such as drag, gravitation and surface tension were introduced and then the mass and energy conservation equations were solved using the control-volume or an Eulerian approach, while considering the mass shedding from the liquid column (i.e., surface breakup). In the far field zone, a model for the trajectory of large droplets generated at the column breakup location was developed using a Lagrangian approach, while utilizing the information on the column breakup location obtained from the first zone as the initial conditions for the second zone. The impact of nozzle internal geometry on the jet exit conditions (i.e., turbulent or non-turbulent liquid jet), and consequently on the liquid jet's trajectory and its breakup length has been examined experimentally in order to reach a more reliable prediction of these features. The experimental data sets were used to validate and extend the applicability of the mathematical models developed in this study. As a result, two modified correlations were proposed to predict the trajectory and breakup length of a round liquid jet injected transversely into a subsonic gaseous crossflow for different liquid properties, test/operating conditions and nozzle internal geometries.