Number of blades on a turbine - cause/effect

[djvoodoo]

Number of blades on a turbine - cause/effect

Unsure if this has been covered in great detail at all on SAU.

With regards to turbo compressor/turbine blade design. What is the effect of having say 9 blades vs 11 blades on the turbine side if all else is equal (housing and wheel trims etc). Same said for the compressor.

E.G - standard R34 GTR turbos have like 5 blades vs -9's etc that have 6 on the comp side

From the 5 mins of searching i've done... 

The more blades the better it helps with low down rotational force, but can constrict top end. The more blades the more efficient at higher boost thresholds. I notice that a lot of billet wheel compressor blades are 11 single blade design

Does this sound anywhere near half correct?

 

[Trex]

 Less blades = more sutututu?

 

I can't tell you what the reasoning is behind more or less blades. But there are so many factors that the manufacturer would take into account.

Blade pitch, blade size, compressor size, ball bearing, etc etc

 

Keen to hear what other people think.

[jet_r31]

Roughly less blades on turbine is more top end

Comp wise 6+6 should outflow 11 blades

But theres so many factors there

Blade size/design

[Dale FZ1]

22 hours ago, djvoodoo said:

What is the effect of having say 9 blades vs 11 blades on the turbine side if all else is equal (housing and wheel trims etc).

The more blades the better it helps with low down rotational force, but can constrict top end. The more blades the more efficient at higher boost thresholds.

Does this sound anywhere near half correct?

 

It's much the same as for any pump, or even boat propellors.

Without changing ANYTHING other than the number of blades, it will pump more air earlier (compressor), or apply more drive to the driven shaft (turbine).  And then become less efficient at higher pressure ratios and mass flow levels.  More blade surface area to do the work helps shift air at lower rotating speeds, and the same factor eventually becomes a restriction.

The use of extended tip blades, light weight impellers, half-height blades etc are engineering solutions to either flow/response requirements from a given size package, or noise reduction.

 

It is still possible to option some turbos with different blade counts, with a realistic expectation it will perform differently. By how much is the unknown factor.  Kinugawa is one that I know of.

[djvoodoo]

As a real example.

Say we compare the HKS GT-SS and HKS 2510 turbos. They are in essence, the same item. The 2510 is just the predecessor of the SS

GT-SS uses 6 blades for comp, and 9 for turbine

2510 uses 6 blades for comp, and 11 for turbine.

Both use ball bearings, both use inconnel for the blades but there are slight differences in wheel trim and housing design.

2510 is rated at 600PS, whereas the GT-SS is rated at 560PS.

So apart from the number of blades, the difference in power, flow and boost thresholds are more now to do with blade design, material and housing trims?

 

Edited June 19, 2017 by djvoodoo

[Dale FZ1]

I haven't examined either of those units in any detail.  Not so sure that the flow (rated power) figures are for a single unit there though...

But it's an example that isn't in keeping with the original question.

eg. different housing, different trim size.  And without a detailed inspection, it's quite possible that the blade form (shape) is different.

 

The case I cited was for a TDO6H-25G.  Turbine rotor was available in either 11 blade or 12 blade when I purchased.  There was also a 9 blade with the same critical dimensions but completely different design. Compressor impeller options had 3 choices, but they were all different designs (and prices).  Two different compressor housings, and up to 5 different turbine housings were available. 

It would be very easy to get into a muddle with so many choices, which is probably why the engineers do the development work and the marketers generally offer only basic spec variations eg. turbine housing A/R. 

[Dose Pipe Sutututu]

Convert to a single turbo, twin gates, twin scroll.

Will be better than any set of twins, with 6+6 or 11 blades on the compressor side.

Twins on a GT-R is a fail. Even BMW went to a TS turbo on their N55 motor.

[sneakey pete]

Gt2510's are a completely different wheel diameter that gtss from memory?

 

Anyway, this is the sort of question that you do a PHD to answer. so many variables, as a pure thought experiment sure, more blades means more flow, but as blades aren't infinitesimally small that comes into it

[MagicMikeZ32]

I don't recommend cutting off any blades to get more top end

[djvoodoo]

2 hours ago, sneakey pete said:

Gt2510's are a completely different wheel diameter that gtss from memory?

 

Anyway, this is the sort of question that you do a PHD to answer. so many variables, as a pure thought experiment sure, more blades means more flow, but as blades aren't infinitesimally small that comes into it

Yep, we have had a good chat about this offline :-)