This paper focus on the dynamic of a spray issued from the shearing of a liquid jet injected in an air crossflow submitted to high acoustic perturbations. Experimental and numerical approaches are used. Characterization of the liquid jet close to the injection location is obtained from high speed visualizations performed with a back lighting technique. Phase Doppler Anemometry gives useful information on the spray dynamics. The phase-averaged post processing method is chosen to describe the flow oscillations during the excitation cycle. The numerical simulation is performed with the multi-scale LES approach. This method couples a multi-fluid solver for the liquid jet body with a dispersed phase solver dealing with the atomized spray. The experimental results show a swigging phenomenon of the liquid jet and the existence of velocity and concentration waves travelling downstream of the liquid jet. Coupled phenomena between the crossflow, the atomization of the liquid jet and the transport of droplets are observed, revealing different wave transport velocities. The numerical simulation is able to capture the global swinging phenomenon of the liquid jet main body as well. A very good agreement is obtained for the jet trajectories oscillations obtained either by the simulation or from the experiment during the whole excitation cycle.
The design of modern aeronautical propulsion systems is constantly optimized to reduce pollutant emissions while increasing fuel combustion efficiency. In order to get a proper mixing of fuel and air, Liquid Jets Injected in gaseous Crossflows (LJICF) are found in numerous injection devices. However, should combustion instabilities appear in the combustion chamber, the response of the liquid jet and its primary atomization is still largely unknown. Coupling between an unstable combustion and the fuel injection process has not been well understood and can result from multiple basic interactions. The aim of this work is to predict by numerical simulation the effect of an acoustic perturbation of the shearing air flow on the primary breakup of a liquid jet. Being the DNS approach too expensive for the simulation of complex injector geometries, this paper proposes a numerical simulation of a LJICF based on a multiscale approach which can be easily integrated in industrial LES of combustion chambers. This approach results in coupling of two models: a two-fluid model, based on the Navier-Stokes equations for compressible fluids, able to capture the largest scales of the jet atomization and the breakup process of the liquid column; and a dispersed phase approach, used for describing the cloud of droplets created by the atomization of the liquid jet. The coupling of these two approaches is provided by an atomization and re-impact models, which ensure liquid transfer between the two-fluid model and the spray model. The resulting numerical method is meant to capture the main jet body characteristics, the generation of the liquid spray and the formation of a liquid film whenever the spray impacts a solid wall. Three main features of the LJICF can be used to describe, in a steady state flow as well as under the effect of the acoustic perturbation, the jet atomization behavior: the jet trajectory, the jet breakup length and droplets size and distribution. The steady state simulations provide good agreement with ONERA experiments conducted under the same conditions, characterized by a high Weber number (We>150). The multiscale computation gives the good trajectory of the liquid column and a good estimation of the column breakup location, for different liquid to air momentum flux ratios. The analysis of the droplet distribution in space is currently undergoing. A preliminary unsteady simulation was able to capture the oscillation of the jet trajectory, and the unsteady droplets generation responding to the acoustic perturbation. Keywords multiscale numerical simulation, liquid jet in gaseous crossflow, acoustic perturbation, Euler-Lagrange coupling IntroductionThe liquid jet in crossflow (LJICF) configuration covers several applications in engineering systems, such as combustion, chemical or even agriculture fields. Particularly in aircraft combustion chambers, systems where the fuel jet is injected normally into an air crossflow are commonly used. Compared with a free jet into a quiescent flow, this configuration enab...
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