Turbocharger Performance Improvement through adding intake charge whirl

[MrDangerUS]

Turbo compressor performance improvement can be achieved by introducing of the air whirl motion in the turbo inlet (trunking) duct.
Air at the compressor inlet, if spun, can enhance compressor performance. So called positive pre-whirl occurs when intake air flow is rotated in the same direction as compressor wheel rotation, and negative pre-whirl is opposite.

At low engine speeds, the compressor impeller speed is too high in relation to the air flow velocity, so the incidence angle of the blade tip is away from the design point.

Adding pre-whirl in the rotational direction of the impeller (positive pre-whirl) can help to improve the incidence angle and the inlet Mach number is reduced. Since the flow already has a rotational component before entering the compressor wheel, the relative velocity, critical mainly at the wheel tip, is reduced. Inlet Mach numbers can be reduced as low as 1.5. This speed is associated with energy losses, reducing the surge margin. The lower the inlet Mach number is, the smaller the energy loss can be. If the incidence angle is optimized and the energy loss resulting from flow separation can be avoided, the surge margin is also increased. Hence the compressor wheel is able to speed up more freely. The flow already includes a whirl component, so the work done by the impeller can be reduced, which leaves more energy to speed up the impeller wheel.
This can help to improve transient response and increases the pressure ratio for a given turbine energy.
Taking into account information found in the literature, swirl of greater than +40 degree of vane angle is less effective.  http://publications.lib.chalmers.se/records/fulltext/211737/211737.pdf
Vanes angle of 20-25 deg (swirl ratio= 0.11), if placed in the uniform diameter tube, exhibit the lowest pressure drop.
Comparison of compressor maps with no swirl and 0.11 swirl coefficient, clearly show efficiency improvement for the latter and the trend for turbocharger efficiency "islands" to move towards lower mass flow (evident in lower pressure ratio area).
Because of the "necked down" encasement shape and vanes located outboard of the center of air stream, I decided to increase the vane angle to 38 deg (0.13 swirl ratio).
For more details, see:
D. Guentert, D. Todd, W. Simmons, "Flow tests of an naca-designed supercharger inlet elbow and the effects of various components on the flow characteristics at the elbow outlet", Tech. rep., National Advisory Committee for Aeronautic (1946).
http://naca.central.cranfield.ac.uk/...ca-tn-1148.pdf
https://www.google.com/patents/US392...YHAyIQ6AEIHTAA

Number of articles mentioned that improvement in turbocharger response time can be seen with swirling flow in the inlet.
For example, M. Toussaint, P. Podevin in their paper Guide-vanes upstream the impeller of centrifugal compressor, 5th European Conference on Turbomachinery Fluid Dynamics And Thermodynamics, stated, that at full load conditions, the turbocharger response time can be reduce by up to 24%, and at part load conditions even by 40%.
For years, BMW and MB have been using swirl generators in the intake manifolds of their turbocharged vehicles.

Following  https://www.google.com/patents/US6550446

I have developed an idea of the "stepped whirl generator" with a diminished pressure drop. 38 degree vanes are located at the larger 3" dia section to not to interfere with the central air stream flow.  More details on page 22 of http://www.lotustalk.com/forums/f164/x180-improvements-246153/index22.html

Also, necking down of the generator diameter (from 3" to 2.5"), increases compressor inlet initial pressure improving its spool-up time.

Simple, inexpensive, yet effective.

Edited May 21, 2017 by MrDangerUS

[Jacques]

Very interesting. Thanks for sharing.

I'd certainly like to know what effect it gives on your car.

What happens if the tract shape on your Picture is extended, I mean the conical shape is extended?

Marting at HGP in germany, have developed special turbo vanes in relation to in and outlet sides and mader over 20 turbos of his own, maximising the spoolup and perfomance plus managing energy loss. Not exactly the same, but never the less also worth working with.

Kind regards,

Jacques.

[MrDangerUS]

Jaques,

Very interesting.

Can you post a picture of Martin's turbo vanes?

Thanks

John

[Steve V8]

Extremely interesting idea, and something I've often thought about but don't have ability to put into practice. 

Could I suggest that increasing the diameter of the intake will reduce the density of the air at the critical point just before the turbo where you want it to be at its densist. 

My idea was a rifled intake tube which would cause the same 'swirl' effect but would act along the entire length, my other thought was a vortexed and fifled intake narrow end at the turbo intake to increase air density prior to turbo compression. 

[MrDangerUS]

Steve,

There is a "rifled" intake duct drawing in Patent US6550446

  https://www.google.com/patents/US6550446

If you enter any idea into a Google Patents search, often you can find similar topics with drawings and detailed description.

Edited December 21, 2017 by MrDangerUS

[Jacques]

Hi John,

No, I don't have pictures, as he wants to keep it for himself, but I'll try and see if he has let them out on the web or sniff some up from a friend who regularely visits Martin.

Kind regards,

Jacques.

[MrDangerUS]

Javques,

Here is a company, which makes best turbos on Earth. They are very innovative and on the leading edge of technology.

Pretty reasonable prices,(comparable to Garrett or Turbonetics new turbos), and fantastic performance!

Take look at their Technology information page:

https://www.compturbotechnology.com/our-ct-r-line

[Stuart Monument]

Enjoyed reading that. Learnt a lot. Can’t pretend I understood it all but I understand the principle. Great stuff. 

[MrDangerUS]

FYI: Great article explaining advantages of the twin-scroll turbos

https://dsportmag.com/the-tech/twin-scroll-vs-single-scroll-turbo-test-the-great-divide/

https://zilvia.net/f/showthread.php?t=460807&page=8

Edited March 21, 2019 by MrDangerUS

[MrDangerUS]

For all cars with an external w/gate, I found this twin scroll turbine cover, if you want to go this way

https://www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-HSG-215&Category_Code=NEW

[snowrx]

I'd prefer that one over the constricted V-band turbine mount mentioned in the comparison. I'm surprised it did as well as it did.

[HarryMann]

On 09/12/2017 at 23:35, Steve V8 said:

Extremely interesting idea, and something I've often thought about but don't have ability to put into practice. 

Could I suggest that increasing the diameter of the intake will reduce the density of the air at the critical point just before the turbo where you want it to be at its densist. 

My idea was a rifled intake tube which would cause the same 'swirl' effect but would act along the entire length, my other thought was a vortexed and fifled intake narrow end at the turbo intake to increase air density prior to turbo compression. 

I think reducing diameter might reduce the density at the intake, not increase it ?

rhou1 x V1/ T1 = rhou2 x V2 / T2

continuity ?

Edited November 30, 2022 by HarryMann
Forgot the content 😀

[plumdeplakmuis]

If you are not running the operating point close to the surge line at any point i the compressor map it will not bring much benefit. Pre-swirl only shifts the compressor map. For efficiency the pre-swirl vanes are only another drag increasing component within the air system. 

As both the I4 and V8 Esprit engines don't take a extreme amount of boost a situation that a compressor is benefitting from this pre-swirl system is very rare. Beter is it to select the best compressor and turbine combination to improve performance. Also a straight inlet before the compressor inlet important and overall as less restriction in the inlet as possible. (With a downside of increased intake noise)

[MrDangerUS]

FYI, here is a quite interesting paper:

https://www.semanticscholar.org/paper/Inlet-Swirl-on-Turbocharger-Compressor-Performance-Huang-Liu/cd3dc3022964c1ffe104f62f252c4246ecc05708

and

https://www.semanticscholar.org/paper/Effect-of-Prewhirl-on-the-Performance-of-Najjar-Akeel/c4434b77acbc869bf7f9afd0d12ab67f312b5f6a