Jet Engines: How Do They Move Forward?

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Discussion Overview

The discussion centers on the mechanics of jet engines and how they generate thrust to move forward. Participants explore the principles behind thrust generation, comparing jet engines to rocket engines, and consider the role of gas expansion and airflow in the process.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that a jet engine moves forward because the speed of the air being expelled is greater than the air being pushed aside, implying a division of force between pushing air out of the way and propelling the jet forward.
  • Another participant counters this by explaining that a rocket engine operates by creating hot gas that pushes equally on all walls of a closed chamber until a hole is made, allowing the gas to push on one side and resulting in forward movement.
  • This second participant draws a parallel to jet engines, noting that they pull in oxygen from the air and that the hot gas pushes on the back of the compressor blades, contributing to thrust generation.
  • A later reply expresses appreciation for the explanation provided, indicating a positive reception to the clarification offered.
  • Humorous exchanges occur among participants, with references to a "white dwarf" and self-deprecating comments about height, which do not contribute to the technical discussion.

Areas of Agreement / Disagreement

Participants present differing views on the mechanics of thrust generation in jet engines, with one perspective focusing on the interaction of expelled air and forward motion, while another emphasizes the principles of gas expansion and pressure differentials. The discussion remains unresolved regarding the initial claim about thrust mechanics.

Contextual Notes

Some assumptions about the mechanics of thrust generation and the behavior of gases in jet engines and rocket engines are not fully explored, leaving room for further clarification and discussion.

makster246
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O.k i understand that a jet engine gains its thrust by pushing heated air out its nozzel, but i was wondering if that the reason it goes forward is because the speed of it being released out the rear nozzel is moving faster than the air can get pushed out of the way so the some of the force is used to push air out the way, and the remaining is used pushing the jet forward
is this correct?
 
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No it's a lot simpler than that.
Consider a rocket engine (it's a little simpler )
You burn fuel in a closed box , the fuel creates hot gas which expands pushing on all the walls of the box equally - so no movement.
Now make a hole in the back of the box, the hot gas at the back doesn't push on this any more, but there is still gas pushing on the front of the box - so the box moves forward. This is why rockets can work without atmosphere.

A jet engine is basically the same except that instead of storing the oxygen it pulls it in from the air at the front. Instead of pushing on the front of the rocket chamber the hot gas is pushing on the back of the compressor blades.
 
Thanks very much that explains a lot :), your a star
 
makster246 said:
your a star

A white dwarf, to be specific... :rolleyes:

Okay, I'm leaving now.
 
Danger said:
A white dwarf, to be specific...
I prefer to think of myself as 5' 6 1/2" of slightly degenerate matter
 

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