# About difference in Velocity and motion in Jet engines

• ZdMh
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.

#### ZdMh

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.

It sounds like you are leaving the combustion part out of your description...?

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

Don't forget the exhaust...

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?

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!

https://en.wikipedia.org/wiki/Components_of_jet_engines

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Lnewqban
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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ZdMh

## 1. What is the difference between velocity and motion in jet engines?

Velocity refers to the speed and direction of an object, while motion refers to the movement of an object in relation to a reference point. In jet engines, velocity is the speed at which the air is forced out of the engine, while motion is the movement of the aircraft in 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 air exiting the engine, the greater the thrust produced, resulting in a faster and more powerful aircraft. Velocity also affects the efficiency and fuel consumption of the engine.

## 3. What factors can affect the velocity of a jet engine?

The velocity of a jet engine can be affected by several factors, including the design and size of the engine, the temperature and pressure of the air entering the engine, and the speed and altitude of the aircraft. Changes in these factors can alter the velocity and performance of the jet engine.

## 4. How is velocity controlled in a jet engine?

Velocity in a jet engine is controlled by adjusting the amount of fuel and air mixture entering the engine, as well as the shape and position of the engine's nozzles. These adjustments can be made manually by the pilot or automatically by the engine's control system.

## 5. Why is understanding the difference between velocity and motion important in jet engines?

Understanding the difference between velocity and motion is crucial in jet engines because it allows engineers to design and optimize the engine for maximum performance. It also helps pilots to control and maneuver the aircraft effectively, taking into account the effects of velocity and motion on the engine and the aircraft's overall performance.