Large Eddy Simulations for atomization in subcritical liquid rocket engines

https://www.youtube.com/watch?v=klsG9jvS-qg

This thesis addresses Large-Eddy Simulations (LES) of combustion chambers for space propulsion. Rocket engines may face various thermodynamic conditions, including subcritical regimes where liquid and gaseous phases coexist in a reactive, compressible environment.

In this context, a multi-fluid approach, which assumes equilibrium of temperature, pressure, velocity, and Gibbs potentials, is considered to simulate these flows. Surface tension forces, which play a crucial role in atomization phenomena, are accounted for in this work. The method is evaluated on a reactive configuration representative of rocket engine conditions (test bench investigated at Technische Universität München (TUM)), presenting very promising results and highlighting the benefits of simulating the liquid jet compared to a method that models it through the injection of Lagrangian particles.

Subsequently, an approach is proposed to transfer specific large liquid structures, predicted by an Eulerian framework, to a Lagrangian model following their initial separation from the liquid core. A secondary atomization model is then used to predict the characteristics of the final spray. A multi-species algorithm allowing the transfer of mass, energy, and momentum between these two formalisms has been implemented. The entire strategy is evaluated on a Jet In Cross Flow (JICF) configuration, leading to very encouraging results.

Finally, this coupling strategy is applied to the reactive TUM case configuration. Preliminary results demonstrate the capability and robustness of this methodology under reactive conditions.

Jury