Solving Supersonic Combustion Challenges with Detonations

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Discussion Overview

The discussion revolves around the challenges of achieving steady detonation waves in supersonic combustion systems, particularly in the context of air intake and fuel mixing. Participants explore theoretical scenarios and practical implications related to detonation dynamics and combustion stability.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the feasibility of generating a steady detonation wave in a combustion chamber with supersonic airflow, referencing the Chapman-Jouguet condition.
  • Another participant highlights the challenge of air intake in a continuous detonation scenario, noting that a stationary shockwave would complicate fuel inflow.
  • A different perspective suggests that a partially spherical or planar shockwave could be considered, but acknowledges the difficulty in achieving this without obstructing fuel flow.
  • One participant proposes a coaxial burner design where fuel and air are mixed, questioning if a detonation could occur under these conditions and whether there would be sufficient residence time for combustion.
  • A separate inquiry is made regarding the simulation of a one-dimensional ZND structure for detonation using a one-step Arrhenius model, seeking assistance from others who may have experience with this approach.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of achieving steady detonation waves in supersonic combustion, with no consensus reached on the feasibility of the proposed concepts or designs.

Contextual Notes

Participants acknowledge various assumptions related to shockwave behavior, fuel-air mixing dynamics, and the limitations of current understanding in detonation theory. Specific mathematical or experimental details remain unresolved.

Clausius2
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Ok. Let's suppose the next imaginary experiment. I encouragely promise that I don't know anything about nowadays supersonic combustion problems. I want to continue with the discussion spread in the "rocket thrust" thread, and what Enigma and Russ Waters said.
There is a supersonic flow at the entrance of combustion chamber, due to the intake of air. Why it does not possible generate a combustion steady wave (i.e. a detonation wave) in the combustion chamber. A weak detonation causes a supersonic flow behind it. I heard the Chapman-Jouguet detonations are possible oftenly.
How could I generate a steady detonation?, I mean a detonation that no moves in the laboratory reference axes.
I have another idea: what about heating the supersonic inlet current?.
The Mach number will decrease, but would it descent below M=1?. In this case would occur a shock wave at the intake?.
 
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I think one of the problems with continuous detonation is how to intake air into the fire. As you've pointed out, a detonation creates a supersonic shockwave which spreads outward in every direction away from the center. If the shockwave were stationary relative to the laboratory frame of reference, how would air get in?
 
I was not thinking of an spherical shock wave. It would be a part of an sphere, or a plane wave indeed.
I claim to the combustion expertises to try to get rid of my theory giving a powerful reason of why it is not possible (nowadays).
 
But I think it is the nature of any detonation to propagate outward in all directions equally. I can think of no way to make a partially spherical wave or planewave out of the shockwave from a detonation, other than blocking one side with a barrier, which would also prevent the inflow of fuel.

Do you know of a way to generate a blast of that shape so that fuel flow will be permitted? I keep trying to imagine one, but I keep running into dead-ends.
 
I was thinking like in a burner in which fuel flow and breathing air are mixed coaxially and axilsimmetrically, with the fuel inflow at the centre. It would be a diffusion flame, but now, Is it possible a detonation in such a burner, if the air intake is supersonic?. Would there be enough residence time for burning?. If that is possible, there would be a detonation-steady wave in the laboratory frame, with a flame shape (with a continuous fuel intake).
But the scientists are not dull at all, so I'm waiting an answer telling me this idea is something like a cock and bull story.
 
Dear all!
I have a problem in simulating the 1 dimensional znd structure for detonation. I want to use 1 step Arrhenius model for reactio. has anyone done it before? please help me.
Thanks
 

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