About difference in Velocity and motion in Jet engines

In summary, the conversation discusses the role of combustion in jet engines and how it creates motion. The process of compressing air at high speed, colliding with turbine blades, and heating the gas through combustion all contribute to the forward motion of the engine. The output of 100 m³/s is an arbitrary example used to understand the relationship between volume and velocity.
  • #1
ZdMh
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I was watching a video about jet engines, and it was obvious for me and for the instructor that if we compress air at high speed from the gas turbine inlet, then after multiple stages collide with the turbines blades inside, the body will move in the sense of difference in velocity, so forward. At a moment it was obvious, but I can't really explain it why? Can you help me with that using some formulas.
 
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  • #2
It sounds like you are leaving the combustion part out of your description...?
 
  • #3
berkeman said:
It sounds like you are leaving the combustion part out of your description...?

But the combustion itself can't necessarily provide a motion
 
  • #4
Don't forget the exhaust...
 
  • #5
ZdMh said:
... the body will move in the sense of difference in velocity, so forward.
ZdMh said:
But the combustion itself can't necessarily provide a motion

Could you explain these parts a little better, please?
 
  • #6
ZdMh said:
But the combustion itself can't necessarily provide a motion
Maybe not necessarily, but in a jet engine it sure as heck does! :smile:

1619099906470.png

https://en.wikipedia.org/wiki/Components_of_jet_engines
 
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  • #7
The combustion heats the gas causing the volume to increase.

Choosing an arbitrary number, suppose we have
one cubic meter per second coming in and 100 m³/s going out. What does that tell you about the velocities?
 
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1. What is the difference between velocity and motion in jet engines?

Velocity refers to the speed of an object in a particular direction, while motion refers to the movement of an object from one position to another. In jet engines, velocity is the rate of change of the aircraft's speed, while motion is the movement of the aircraft through the air.

2. How does velocity affect the performance of a jet engine?

Velocity plays a crucial role in the performance of a jet engine. The higher the velocity of the exhaust gases, the greater the thrust generated by the engine. This thrust is what propels the aircraft forward and allows it to maintain its speed and altitude.

3. Can jet engines operate at varying velocities?

Yes, jet engines are designed to operate at different velocities depending on the phase of flight. During takeoff and climb, the engine operates at high velocities to generate the necessary thrust. In cruise, the velocity is reduced to maintain a constant speed and fuel efficiency. During descent and landing, the velocity is further reduced to safely slow down the aircraft.

4. How is velocity controlled in a jet engine?

Velocity in a jet engine is controlled by adjusting the amount of fuel and air entering the engine, known as the fuel-air ratio. This is regulated by the engine's control system, which constantly monitors and adjusts the fuel flow to maintain the desired velocity.

5. What are some factors that can affect the velocity and motion of a jet engine?

The velocity and motion of a jet engine can be affected by various factors such as air density, temperature, altitude, and weight of the aircraft. These factors can impact the performance of the engine and may require adjustments to maintain the desired velocity and motion.

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