# Questions tagged [bypass-ratio]

This is the ratio of air (by mass) that bypasses the combustion chamber of a jet engine, and instead is pushed through the outer shell of the engine by the main fan in the same way that a propeller pushes air.

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### What is physically happening when you use a bypass nozzle on a turbofan?

I am having trouble understanding how a fan affects the flow of air through the bypass in a turbofan engine. Solving for the flow of air using thermodyanic states requires using a bypass nozzle to &...
238 views

### Is it true that high-bypass engines are inherently inefficient at higher speeds?

Power consumption=Kinetic energy=$1/2mv^2$. Thrust=momentum change=$mv$. I keep being told that aircraft engines are most efficient when their exhaust velocity closely matches the freestream. The ...
3k views

### How does the bypass air provide thrust?

To my knowledge, bypass air produces 80% of total thrust. But I don't understand to how it does that. By accelerating the air, by increasing the speed or increasing the pressure of the air? Is it ...
34 views

### What is the flow rate through the bypass tubes on the J58 engine?

Does anybody know how large the mass flow rate through the bypass tubes on the Pratt & Whitney J58 engines at subsonic and supersonic conditions is? Also is there any information available to find ...
1k views

### How does the CFM LEAP-1B engine achieve the same efficiency as the LEAP-1A despite its lower bypass ratio?

The CFM LEAP engine comes in 3 variants (1A, 1B, 1C). The larger LEAP-1A and LEAP-1C variants have bypass ratios of 11:1, while the smaller LEAP-1B only has a bypass ratio of 9:1. For turbofan ...
823 views

### Does the P&W F100 turbofan engine of the F-16 really produce this much power?

I've been trying to calculate the power a P&W F100 engine on a F-16 is producing using some of the available data on thrust and velocity and I ended up with a number that I want to confirm. Here's ...
146 views

### What type of engine is mounted on the Cessna Citation Hemisphere?

What type of engine is mounted on the Cessna Citation Hemisphere? Image Source That does not look like a high bypass turbo jet engine. If its not a high by pass turbo jet engine, and given a high ...
410 views

### Does bypass air produce thrust?

How does bypass air exiting the bypass nozzle produce thrust in a turbofan engine? I thought that thrust was produced by air reacting with the fans. So if thrust happens when there is an action-...
883 views

### Why does the CF6 have a lower bypass ratio than the TF39?

The General Electric TF39, which powered the original C-5 Galaxy, was the very first high-bypass turbofan brought into mass production, with a previously unheard-of 8:1 bypass ratio. Yet, when it ...
4k views

### Can high-bypass turbofans cruise at high altitude?

They have talked for years about re-engining the B-52 with something more modern than its TF33-P-3/JT3D turbofans, which are fairly low-bypass (1.42:1 for the JT3D). Modern engines are much higher ...
517 views

### Bypass ducts and spinning blades [duplicate]

I want to start out by saying these questions will make me look a fool but i simply haven't found answers for them anywhere so i'm hoping you could help me! What is the purpose of bypass ducts? If ...
602 views

### How do aircraft engine manufacturers achieve a higher bypass ratio while still meeting the thrust requirements for a given aircraft?

I understand that a higher bypass ratio leads to greater efficiency as less air moves through the core, and therefore less fuel is burned. However, how is the thrust requirement for the same aircraft ...
4k views

### Is it possible to have an afterburner in a turbofan with bypass ratio greater than 1:1?

Is it possible to have an afterburner in a turbofan with a bypass ratio greater than 1:1? At 1.05:1, say, can it have an afterburner?
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### How was the high-bypass concept invented?

(Source) Wikipedia says: After [the Ryan XV-5 Vertifan demonstrated] that large amounts of air could be moved through a lift fan, an 80 in (2.0 m) tip drive fan turned through 90 degrees, driven ...
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### Why is the bypass ratio of a turboprop higher than turbofan?

Whenever, I come across turboprop, the author always mentions that they have higher bypass ratio than turbofan but no one explains the reason for this. So, is the bypass ratio higher due to higher ...
10k views

### What is the bypass air in a turbofan engine actually for?

I'm planning on building a small model turbofan engine for a bit of fun but I thought I'd better get a better understanding of how they work first. I understand the majority of it at the moment but I'...