Doctorant : Challenging the URANS aerodynamics excitation predictions

Framework:

This thesis project is a part of the European project Clean Aviation HE-ART (Hybrid Electric propulsion system for regional AiRcrafT). The objective of HE-ART is to research and prepare a flight test of a Hybrid-Electric Regional Aircraft. Hybrid-electric propulsion is a significant challenge for the successful realization of the Hybrid-Electric Regional aircraft (HER) with a targeted fuel burn reduction of at least 50% at aircraft level. This thesis work on the propulsive system in particular to contribute to developing an ultra-efficient turboprop thermal engine.

Subject:

Modern compressor design relies intensively on numerical simulations. In the past decades,

CFD has increased flow dynamic knowledge and compressor performances. In the same time, the compressor geometry has become more complex and the impact of technological effects has gained in relative importance. In this context, even more advanced numerical technique for design has to be developed and validated. As such, URANS simulation is a key part in the prediction of the blades loading and its fluctuation in the successive rows.

A first step of the work is to establish a reference case with the URANS industrial state of the art methodology, including solvers setup and fluid domain definition. The next step is to challenge this prediction representativity by adding some ingredients, starting with the backface cavity. This cavity is necessary to allow the rotor displacement. It is connected with the compressor main flow through a small gap at the rotor trailing edge. Standard industrial

simulations do not include this feature. With new enhanced simulations, various topics will be investigated:

- The azimuthal organization of the flow inside the cavity, which can generate an additional

aerodynamic excitation on the rotor.

- The interaction of the cavity leakage flow with the compressor main flow, which can affect

the fluctuations in time and space of aerodynamic features already predicted inside the rotor

and diffuser.

- The pressure fluctuations inside the back-face cavity, which are affecting both previously

pointed mechanisms.

The targeted test case is the Turbocel centrifugal compressor research module, mounted on ECL-B1 test bench. It is heavily instrumented. An experimental database will also be produced at ECL in the overall HE-ART project. The candidate will be invited to participate to the test campaigns along the professional team in charge. An important part of the thesis work will be then the conjugated analysis of simulations and measurements results.

Knowledge and Skills:

University courses in fluid mechanics, including turbulent flows. Courses in aeronautic propulsion and/or turbomachinery as an advantage. Appetite for Computational Fluid Dynamics. Thoroughness, team work and autonomy.

Related publication:

- Unsteady Analysis of a Pulsating Alternate Flow Pattern in a Radial Vaned Diffuser. Nicolas Poujol, M. Buisson, P. Duquesne, I. Trébinjac. International Journal of Turbomachinery, Propulsion and Power (2022). DOI 10.3390/ijtpp7030023

- Effects of inlet guide vanes on the performance and stability of an aeronautical centrifugal compressor. Nicolas Poujol, I. Trébinjac, P. Duquesne. Journal of Turbomachinery (2021). DOI 10.1115/1.4050944.