CERFACS and CNRS Perform First-Ever Large Eddy Simulation of Instabilities in a Rocket Engine

In a collaborative work with CERFACS, Institut de Mécanique des Fluides de Toulouse, Centralesupelec, ONERA, DLR and TU Munchen, researchers have been able to use the CERFACS LES code AVBP (http://www.cerfacs.fr/en/computational-fluid-dynamics-softwares/) to simulate the instabilities which appear in certain rocket engines under extreme conditions. The simulation was performed thanks to a PRACE allocation of 80 M hours. The massively parallel capacities offered by AVBP have allowed to run on 65 536 processors in production mode (the code itself scales up to 200 000 cores) on the Bluegene Q machine of CINECA.

Dr A. Urbano (supported by an European Research Council advanced grant: intecocis.inp-toulouse.fr) and her colleagues have created a digital twin of a rocket engine installed and operated at DLR Lampoldshausen. This numerical model is based on a Large Eddy Simulation of cryogenic H2/O2 combustion inside the exact DLR rocket geometry. This small engine (typically 20 cm long) has the power of 1000 car engines and can exhibit very violent combustion instabilities which have been captured by the LES code with precision for the first time.

Fig. 1 displays a view of the flame surface colored by the axial velocity field and shows how combustion is organized in this high-performance engine.

Fig. 1: Large Eddy Simulation of combustion inside a rocket engine.

LES results have allowed to identify the unstable modes appearing in the experiment with precision. The paper published by Dr Urbano et al has been selected as one of the best papers at the last Symp. (Int.) on Comb. in Seoul which is the most famous symposium in the field (Urbano et al 2016a). Her paper in Combustion and Flame, the leading journal in the field of combustion, has also been heavily cited (Urbano et al 2016b).

This task must now be extended to real rocket engines as companies such as SPACE X and AIRBUS SAFRAN Launchers compete to develop the new generation of launcher engines based on methane / oxygen combustion and wonder whether combustion instabilities will represent a danger or not for these technologies. High Performance Computing is, of course, the key issue in this simulation process and CERFACS continues to lead research in this field as well as to ensure advanced formation of European PhD students at the best level (see http://cerfacs.fr/en/jobs-at-cerfacs).

References:

a/ Urbano, A., Douasbin, Q., Selle, L., Staffelbach, G., Cuenot, B., Schmitt, T., Ducruix, S. and Candel, S. (2016) Study of flame response from the Large-Eddy Simulation of a 42-injector rocket engine, Proceedings of the Combustion Institute, 36, doi:10.1016/j.proci.2016.06.042

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