ram effect

engineering

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Last updated

July 13, 2026

Quick Summary

The "ram effect" in engineering refers to the increase in static pressure within an air-intake duct due to the relative velocity between the air intake and the surrounding air stream. This effect is particularly important in jet engines operating at supersonic speeds.1

At speeds above Mach 2.5 or 3, the ram pressure becomes significant enough that a turbocompressor is no longer needed for thrust generation. This leads to the development of ramjet engines, which rely solely on the ram effect for compression. Ramjets are simple and lightweight, making them suitable for supersonic flight vehicles.2

For even higher speeds (Mach 4 or 5), specialized engines called scramjets (supersonic combustion ramjets) are used, where combustion occurs in a supersonic airstream. To address the inefficiency of ramjets at lower speeds, turboramjets combine a turbofan engine with a ramjet, providing propulsion across a wider range of flight speeds.23

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jet engine
Low-bypass turbofans and turbojets
…as the engine’s working fluid—the ram effect. At transonic flight speed this pressure ratio is almost 2:1, so that the engine’s compressor may be built to provide that much less pressure where peak pressure is otherwise limiting.
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…as the engine’s working fluid—the ram effect. At transonic flight speed this pressure ratio is almost 2:1, so that the engine’s compressor may be built to provide that much less pressure where peak pressure is otherwise limiting.
Read More