Resumen:
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[EN] 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 ...[+]
[EN] 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.
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