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Thesis by Songzhi Yang*

Numerous technological applications requiring the use of numerical simulation involve complex two-phase flows, as is the case with the engine injection context. Most calculation software in the field of fluid mechanics can simulate single phase (liquid or gas) flows, potentially in a supercritical regimea, or two-phase flows (liquid-gas) in a subcritical regime. This research proposes a complete modeling approach to simulate both cases, including the transcritical regimeb, as well as any phase transition (evaporation or condensation). For this, a totally compressible, diffuse interface two phase flow model was developed, based on a Eulerian-Eulerian approachc with real fluids assuming liquid-vapor equilibrium(1).

It made it possible to simulate transcritical injection in the Spray A reference injector of the ECNd (2). It also proved capable of predicting the cavitation phenomenone in a three-dimensional nozzle, thereby highlighting the importance of taking into account dissolved gases in injection modeling(3). In particular, its use has provided a greater understanding of the phenomenon of bubble nucleation, as a function of the quantity of non-condensable dissolved gases.

Yang
Transcritical injection simulation on the Spray-A injector (temperature field at 112 μs).

Numerous other applications incorporating complex two-phase flows can now be simulated more realistically, such as gas turbines and cryogenic rocket engines, or coolant boiling for electric powertrain power electronics or computing centers.

*Thesis entitled "Modeling of Diesel injection in subcritical and supercritical conditions"

a - State of a pure body when its pressure P>Pc or its temperature T>Tc. In the opposite case, the fluid is in a subcritical state
b - Condition generated when a subcritical fluid is injected into a supercritical fluid
c - Eulerian approach for both the liquid and gas
d - Engine Combustion Network (https://ecn.sandia.gov/workshop/ECN1/intro.pdf)
e - Formation of gas or vapor bubbles in a liquid subject to a pressure drop

(1) P. Yi, S. Yang, C. Habchi, R. Lugo, 2019. Phys. Fluids 31, 026102.
https://doi.org/10.1063/1.5065781

(2) S. Yang, P. Yi, C. Habchi, 2020. Int. J. Multiph. Flow 103145.
https://doi.org/10.1016/j.ijmultiphaseflow.2019.103145

(3) S. Yang, C. Habchi, 2020. Phys. Fluids 32, 032102.
https://doi.org/10.1063/1.5140981

Scientific contact: chawki.habchi@ifpen.fr

>> ISSUE 43 OF SCIENCE@IFPEN