Axial-flow turbo/superchargers?

Why are superchargers and turbochargers all centrifugal-flow instead of axial-flow?
Axial-flow is superior for jet engines, pic related being an example. But why isn't it used in automotive technology? Surely it's more efficient in terms of energy consumed for mass flow, or just permits higher mass flow?

It's been bugging me for a while, and wikipedia isn't forthcoming with answers.

Other urls found in this thread:

en.wikipedia.org/wiki/Napier_Nomad
twitter.com/SFWRedditImages

It's literally the same thing you idiot.

buddy it's xmas, try and relax

/thread

Also how are you going to connect the turbine to the compressor? a chain, or a belt? why. that's like 2 times as much space required.

>Surely it's more efficient in terms of energy consumed for mass flow
Why? Nothing is happening. It's accelerating and then expanding. It doesn't matter what direction it goes in. All compressors are 100% efficient at a certain pressure differential and flow rate (if heat and friction didn't exist).

Energy is converted 100% unless lost through heat and friction. No matter how you're converting it.

It probably has to do with the pressure ratio needed. Car engines generally have one compressor stage. An axial compressor might not have a high enough pressure ratio (PSI) for the first stage, though it might flow a lot. I'm speculating. I don't know much about axial compressors.

We do have axial flow turbines on turbochargers. I guess the impeller is placed further down the neck, and the gas isn't changing direction as much as it passes through the blades.

It is not the "tube" design you are describing, though.

No it fucking isn't, you moron.

it's literally the same thing.
cars don't need axial compressors because the compressed air isn't driving the turbine directly behind it and it would be pointlessly complex.
you're not losing energy by making the air change direction.

A radial turbine turns the air stream 90° as part of it's design. Pic related, a radial jet engine.

An axial turbine lends itself towards air going straight through it, as in the modern jet engine. You'd still have to make the air stream turn for it to be of any use in an automotive application, so why not use something that does it as part of it's design.

not an argument

Congratulations, you spotted it was a declaration of fact and not an argument.
Go fucking look it up yourself, I'm not your mommy, I'm not spoonfeeding you.

>You'd still have to make the air stream turn for it to be of any use in an automotive application
Yes, but WHY? That's what I want to know. Why can't you suck air in and just feed it into the intake axially?

You don't know shit idiot. Changing the direction of the air doesn't "sap" energy. Take a physics course sometime.

>Why can't you suck air in and just feed it into the intake axially?
Hmm maybe because there's a fucking turbine attached to the back driving the compressor by a shaft.
There's no room, it has to be radial

Radial compressor is very simple and robust design that can have 1:6 to about 1:10 pressure ratio in one stage.

Axial flow compressor usually have 1.1:1 to 1.6:1 pressure ratio per stage consisting of rotor and stator. You will need multiple stages to get to the same pressure as one stage radial compressor. The design is also not that robust as there are so many blades that can fail and it will be much bigger than radial compressor.

Also I do not understand the point of turning the airstream and what it has to do with this. Since in axial compressor the airstream is re directed in every stage by stator blades. So in axial compressor the air indeed has more directional changes than in radial compressor.

You can have axial flow with centrifugal compression, it's called a jet engine.
Op is specifically wondering why there's no axial flow.

And it's because the combustion happens outside of the turbine it'self.

>And it's because the combustion happens outside of the turbine itself.

Why would that make a difference, though?
I'm honestly trying to understand it, here; the why as well as the what and the how.

The combustion isn't happening inside the nozzle.
So the only way to get it to the engine and back to the turbine is from the side.

Unless you want to connect the turbine to the compressor with a bunch of belts.

Which you could do.. but it would be pointless.

Ahh, okay.

It's a shame turboshafts aren't fuel-efficient enough to be worth it on cars. I'd love to see cars riced with bypass chambers..

Because HOW THE FUCK ARE YOU EVEN SPINNING IT

And people have already pointed out they compress like shit and have way more blades.

A centrifugal compressor stage has a higher compression ratio than an axial compressor stage, and are easier to manufacture. They are also more robust and deal with debris ingestion better than axial compressors.

In order to achieve the same compression with an axial flow compressor you would need several stages, which adds a lot of weight and complexity.

en.wikipedia.org/wiki/Napier_Nomad

Now THAT has potential for improved truck engines.

There are many axial turbosuperchargers in use from manufacturers like MAN Diesel and Turbo, ABB and KKK which is now owned wholly by Borg Warner.

Axial turbochargers utilise the entire turbine wheel for drive versus the radial using the perimeter of the wheel. This makes the unit very effective at converting drive (pressure, velocity, heat, mass, pressure differential across the wheel) into mechanical energy to rotate the compressor section while keeping drive pressure relatively low. It is far easier to flow gas from the drive side to the exhaust side when there is little to no volute around the turbine wheel.

Axial turbochargers are often a good one to one and a half points of Pressure Ratio higher in delivery than the same frame size radial turbocharger using the same level of drive. I am not sure where everyone is getting their information that the opposite is true? The compressor used on an axial turbosupercharger is still a radial compressor wheel.

This combination of effective and efficient conversion of drive to mechanical energy coupled with an efficient compressor makes the axial turbosupercharger ideal for large swept volume engines operating at a governed speed with drive changing based on the quantity of fuel injected. Where they are not ideal are on engines where the operating speed varies. At present, the rotating assembly of an axial unit is always significantly heavier than the same frame size radial unit. As a result they do not adjust to vastly different VE requirements as quickly or with the stability that a radial unit can.

When an axial unit aerodynamically stalls it can be very violent. Many units and even engines has been lost to stall.

Picture is related, a low speed MAN Diesel and Turbo two-cycle using an axial turbine, radial compressor. This engine is designed to be operated between eighty and ninety RPM. Once at this speed drive is changing only with the governor trimming fuel to keep the engine at target speed.