The numerical simulation of cryogenic combustion is crucial for a better
understanding of the complex physics involved in reactive flows of rocket
engines and to help to reduce the development cost of these engines. The
focus of this study is set on the oxidizer injection and its dispersion through
jet dense core destabilization and atomization or supercritical mixing. Specific
models have been implemented in the CFD code CEDRE created by ONERA to
address these physical phenomena.

Even though the technology of cryogenic rocket engines is well mastered today, and has been applied successfully in many launchers all over the world, research activities on the various elementary or coupled processes involved in these complex systems are still relevant and useful for future developments, cost reduction, and knowledge improvement.

Hybrid propulsion generally combines a liquid oxidizer with a solid fuel. Compared to solid or bi-liquid engines, this type of propulsion offers advantages in terms of cost and flexibility. For several years, ONERA has been providing expertise in this area, both in experimental and numerical simulations. Various hybrid rocket motors have been designed and tested on ground, including under low ambient pressure conditions and in flight.

This paper is devoted to a review of some recent studies conducted at ONERA
within the framework of solid rocket propulsion for missiles, as well as space

The reduction of fuel consumption in future propulsive engines is an ambitious target that will be reached only with a technological breakthrough. Two of the possible solutions are being investigated experimentally and numerically by MBDA France, ONERA, PPRIME and SAFRAN Tech. Changing the actual thermodynamical cycle through the use of Constant-Volume Combustion or Rotative Detonation concepts could theoretically enable this target to be reached.

An overview of selected ONERA research activities on supersonic combustion and scramjet propulsion for civilian applications since 1992 is presented. The main part is devoted to basic research on supersonic combustion, including experimental database acquisition and combustion modeling. More applied studies on injection and flame stabilization in research scramjet combustors are then described and the article ends with a presentation of activities dedicated to real scramjet combustor design and characterization.

The scientific activities presented in this article are within the field of the design of new concepts of combustion chambers and the exploration of their benefits to increase the combustion and environmental efficiencies of advanced air-breathing propulsion systems.

The paper describes the main mechanisms of NO_x formation (thermal, prompt NO_x and through N₂O). It is shown that, for combustion products when the gas temperature is less than 1650 K (T_gas<1650 K), the residence time has a weak influence on NOx formation. A concept for the simultaneous reduction of NO_x and CO in low-emission combustors with large residence time is suggested.

For a long time, engine noise has been dominated by fan and jet noise. With their reduction for modern turbojets, for instance, combustion noise is no longer negligible and efforts are concentrated on its understanding. The objective of the European project RECORD is to help to understand the fundamental mechanisms of core noise, in order to reduce it. In this paper, the recent advances achieved within the project for the noise generated through a nozzle are presented.

Combustion instability results from a coupling between acoustic and heat release fluctuations. From the analysis of published works by various research teams including ONERA, this paper describes the coupling lines involved, the model used to describe it and the methods developed to predict the thermo-acoustic risks. The application is focused on the liquid-fueled aero engine specificities.