I want to learn more about aerodynamics, and hypersonic aerodynamics (actually aerothermodynamics), plus I need a model of scramjet engine for XS Venture, so I decided to check out one configuration I found on the internet. It’s a fixed-geometry scramjet engine designed for 5 mach airflow.
Here’s the original URL: http://www.cfd-online.com/Wiki/Scramjet_intake.
You can see CFD pictures below, shockwaves are clearly visible, and you can see why engines loose efficiency outside of pretty small range of about 4.5 to 5.5 mach. The red area is area of high pressure. The fuel is injected into high-pressure area to increase volume of resulting gas, increasing its velocity. As you can see, the high-pressure area starts moving from it’s intended location when you increase or reduce airflow (at some point it even touches engine surface, which is very bad stress for engine structure).
All simulations are done at about 30km altitude, so the pressures are quite low. Static pressure does not affect distribution, it only affects absolute values, so it should be fine.
Mach 3:
Mach 5 (intended speed):
Mach 7:
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