How does the shape of a scramjet engine affect its thrust?

[xj420]

I'm trying to fully understand scramjet engines but I can't seem to find a good source of information. I know the gist of what a scramjet engine is; I want to really understand the physics behind how it works and how the air flows thru the structure. If anyone help me and or knows a site or book that can help me out, please let me know.

 

[enigma]

How much math have you had? I can recommend some books if you have access to a university library.

 

[xj420]

Im a sophmore in college so I don't have a great deal of knowledge in math. I know a good deal of calc. Yes I do have access to a university library.

 

[LURCH]

There's a fairly good explanation here, from HowStuffWorks. I was particularly interested in the shape of the engine. It broadens out as one progresses aft of the combustion chamber, causing me to wonder how much of the thrust is provided by the burning gasses expanding laterally. If the airflow remains supersonic throughout combustion, it would seem that gettnig forward thrust from the explosion is impossible, and all the thrust must be from lateral pressure on the sides of the vent. Can anyone conform or refute?

 

[Clausius2]

There's a fairly good explanation here, from HowStuffWorks. I was particularly interested in the shape of the engine. It broadens out as one progresses aft of the combustion chamber, causing me to wonder how much of the thrust is provided by the burning gasses expanding laterally. If the airflow remains supersonic throughout combustion, it would seem that gettnig forward thrust from the explosion is impossible, and all the thrust must be from lateral pressure on the sides of the vent. Can anyone conform or refute?

I would say the same, Lurch. The combustion chamber has the mission of pressurizing additionally the flow. My doubts are in the combustion process. In fact I wrote something in the Chemistry forum https://www.physicsforums.com/showthread.php?t=40661 trying to undertand how the flame is formed, but no body except an spanish colleague answered me. The question is a little bit specific, and it involves the importance or not of the molecular diffusion transport in the chemical reaction. If anyone goes to that link, he will find a numerical simulation of a supersonic flame made in Fluent 6.0. I found it in a webpage.

To say the truth, XJ420, understanding how the Scramjet works is a little bit hard if you do not have some knowledge about elements of Gas Dynamics. The supersonic flow regimen is not an intitiuve subject.