Position of the fan inside a convergent nozzle

In summary: It depends on many factors, such as what your goals are (highest flow rate, highest velocity, highest pressure?) and other constraints, such as is this the same nozzle/fan in both scenarios, type of fan, structural support issues, space constraints, flow smoothness/uniformity requirements, etc. There is no general answer to the question.
  • #1
T C
320
8
TL;DR Summary
What's the best position to set a fan/blower inside a convergent nozzle?
I want to present two scenarios here. First, there is a convergent nozzle shaped structure having a fan/blower fitted inside. In this case, the fan/blower is fitted at the throat of the nozzle. The inlet to throat ratio isn't important here. And the second scenario, the same nozzle is used but the blower is now fitted at the inlet. Just to mention that velocity of fluid is subsonic in both cases at every point. I want to know what's the best position of the fan/blower? The first one or the second one?
 
Engineering news on Phys.org
  • #2
T C said:
I want to present two scenarios here. First, there is a convergent nozzle shaped structure having a fan/blower fitted inside. In this case, the fan/blower is fitted at the throat of the nozzle. The inlet to throat ratio isn't important here. And the second scenario, the same nozzle is used but the blower is now fitted at the inlet. Just to mention that velocity of fluid is subsonic in both cases at every point. I want to know what's the best position of the fan/blower? The first one or the second one?
It depends on many factors, such as what your goals are (highest flow rate, highest velocity, highest pressure?) and other constraints, such as is this the same nozzle/fan in both scenarios, type of fan, structural support issues, space constraints, flow smoothness/uniformity requirements, etc. There is no general answer to the question.
 
  • Like
Likes jrmichler
  • #3
Correct! I just forgot to mention that in both cases the fan/blower power is the same too. And I have already mentioned that the velocity is subsonic in both cases, therefore no question of increase in pressure. And, to be precise, as you have asked, I want maximum velocity at the throat. And in my thread, I have clearly mentioned that the nozzle is the same in both cases.
 
Last edited:
  • #4
T C said:
Correct! I just forgot to mention that in both cases the fan/blower power is the same too.
Ok...
And I have already mentioned that the velocity is subsonic in both cases, therefore no question of increase in pressure.
That isn't true. The whole point of a fan/blower is to move air by creating a pressure difference. But I guess what you are after is a just an axial fan in a nozzle, with nothing else attached (no ductwork system)? In that case, the static pressure requirement is close to zero, and the type of fan fits that requirement.
And in my thread, I have clearly mentioned that the nozzle is the same in both cases.
I see now...

So you want to know how two different fans that you haven't selected or specified will perform under conditions you also haven't specified. Well, ok, just to throw something at the wall and see if it sticks:

An otherwise uncased axial fan should at least have an inlet bell because the inlet side of the fan has to pull air from all directions and converge it into a coherent stream, which creates turbulence if there is an abrupt entry. This will make it operate more efficiently than the same fan with no inlet bell.

https://www.thefanguy.ca/wp-content/uploads/2017/01/Inlet-Bell-Brochure-Motion-Canada-2017.pdf
 
  • #5
From the link, it seems that the best position is at the inlet.
 

1. What is the purpose of the fan in a convergent nozzle?

The fan inside a convergent nozzle serves to increase the velocity and pressure of the air flowing through the nozzle. This creates a more efficient and powerful flow, which is essential for many applications such as jet engines and rocket propulsion.

2. How does the position of the fan affect the performance of a convergent nozzle?

The position of the fan is crucial in determining the performance of a convergent nozzle. If the fan is placed too close to the throat of the nozzle, it can cause flow separation and reduce the efficiency of the nozzle. On the other hand, if the fan is placed too far from the throat, it may not be able to effectively increase the velocity and pressure of the air.

3. What factors should be considered when determining the optimal position of the fan in a convergent nozzle?

The optimal position of the fan in a convergent nozzle depends on several factors, such as the design and size of the nozzle, the speed and pressure of the air entering the nozzle, and the desired performance of the nozzle. It is important to carefully consider all these factors in order to achieve the best results.

4. Can the position of the fan be adjusted for different applications?

Yes, the position of the fan can be adjusted to suit different applications. For example, in a jet engine, the position of the fan may be adjusted to achieve the desired thrust and fuel efficiency. In a rocket engine, the position of the fan may be adjusted to optimize the nozzle for different stages of flight.

5. What happens if the fan is not positioned correctly in a convergent nozzle?

If the fan is not positioned correctly in a convergent nozzle, it can significantly affect the performance of the nozzle. This may result in reduced efficiency, lower thrust, and potentially even damage to the nozzle. Therefore, it is crucial to carefully consider the position of the fan during the design and operation of a convergent nozzle.

Similar threads

Sonic velocity at the throat of a convergent-divergent nozzle
    • Mechanical Engineering
Replies
3
Views
748
The most efficient nozzle shape
    • Mechanical Engineering
Replies
13
Views
2K
Blower fitted with De Laval Nozzle
    • Mechanical Engineering
3
Replies
92
Views
8K
What is the better way to create less turbulent flow with a blower?
    • Mechanical Engineering
Replies
9
Views
1K
Bernoulli's Principle and Fans [split]
    • Mechanical Engineering
Replies
12
Views
4K
Most efficient convergent nozzle
    • Mechanical Engineering
Replies
7
Views
3K
Blower fitted with a convergent nozzle
    • Mechanical Engineering
Replies
13
Views
1K
Fluid passing through a convergent-divergent nozzle
    • Mechanical Engineering
2
Replies
36
Views
4K
B Beam of air: Extending the range of a fan
    • Other Physics Topics
Replies
17
Views
2K
Fluid Dynamics: Maximizing Downforce Between a Robot and the Floor
    • Engineering and Comp Sci Homework Help
Replies
18
Views
1K

Hot Threads

Recent Insights

Back
Top