Ramjets - Meduim or high-speed aerobic propulsion

This article, dedicated to ramjet engines, begins by describing the different systems in use or under development, for use in subsonic flight (Leduc...), supersonic flight (subsonic combustion ramjets for long-range fast missiles) or hypersonic flight (supersonic or mixed combustion ramjets). The main technological solutions implemented or planned are briefly presented. This is an opportunity to discuss the main choices available to meet specifications (aerodynamic formula, fuel, trade-off between range, acceleration, maneuverability, stealth, cost, etc.).

The second part reviews the various components involved in designing such an engine: air intake, combustion chamber, nozzle, fuel supply, thermal protection. In each case, a costed example is given, based on a ramjet running on hydrogen at Mach 3.

The third part allows you to finalize the exercise, quantifying your performance at Mach 3 and reminding you of what you can expect over a wider flight range.

The pre-project calculation method for a subsonic combustion ramjet is thus described and implemented on a case study, after defining the engine's operating parameters (richness, characteristic cross-sections, etc.). The requirements for its components (air intake, combustion chamber, nozzle, fuel supply) are presented in paragraph 2 .

The examples and data provided are taken from the open literature, as current applications of these engines inevitably lead to restrictions on certain particular points. The phenomena involved, the technological solutions and the calculation methods described in this article are representative of what is understood by engineers in teams in charge of real systems.

Finally, most of the definitions, orders of magnitude and equations required have already been described in previous articles [BM 3 000]