Turbochargers-A Dummies Complaint List

[The Californian]

Complaint/Question #1

How come you hardly hear/read any consideration of the turbine?

Purposely attempting to keep it simple or 'For Dummies'.

[hoffman900]

You're probably just not looking in the right places.

Hasn't most of your research been confined to vintage publications?

[vannik]

Complaint/Question #1

How come you hardly hear/read any consideration of the turbine?

You are right - there are almost no publications on the sizing of turbines for an enthusiast, it is either almost ignored or full blown engineering texts, nothing in between.

[ptuomov]

Complaint/Question #1

How come you hardly hear/read any consideration of the turbine?

Purposely attempting to keep it simple or 'For Dummies'.

If you want to just pick a turbocharger, once you match the compressor correctly to the engine, the turbine side that is matched to that compressor by the manufacturer is usually very close to right. There are a couple of geometry options available, and those can be chosen based on intended use. That’s the “for dummies” approach - match the compressor and don’t worry about the turbine - and it works well.

If you want to understand how the manufacturer matches the turbine with the compressor, the first thing to do is to understand the power requirements of the turbocharger at each point on the compressor map. The power requirements come from the work done per unit of time by the compressor plus inefficiencies in the turbocharger. This book has the formulas that, while not totally for dummies, are simple enough to implement in an excel spread sheet: https://www.goodreads.com/book/show/496 ... bocharging

[The Californian]

'Hasn't most of your research been confined to vintage publications?'

Yes.We have started at the beginning.Early days.

Attempting to keep it simple.

Okay.

How come there is no map for the turbine?

'the turbine side that is matched to that compressor by the manufacturer is usually very close to right. '

Well.Could you support that a little more?

[ptuomov]

'Hasn't most of your research been confined to vintage publications?'

Yes.We have started at the beginning.Early days.

Attempting to keep it simple.

Okay.

How come there is no map for the turbine?

'the turbine side that is matched to that compressor by the manufacturer is usually very close to right. '

Well.Could you support that a little more?

There are turbine maps for most Garrett turbines. They look like these. They don’t have rpm curves because the power extracted by the turbine doesn’t depend that much on the turbine shaft rpm:

CD567715-23DC-4CF9-9AC8-B0ECCBC8C500.jpeg

To interpret that map, one needs to go into a little bit of math and work out the power required to turn the shaft with a specific compressor. On a running engine, we just look at the MAF signal, EGT, and hot side pressures (pre and post turbine) to estimate where we are and don’t really worry about shaft speed. It’s a highly approximate computation anyway because the turbine sees pulses, so it is only really useful in detecting problems or bad mismatches.

[The Californian]

' power required to turn the shaft'

You are speaking 'For Dummies' fluently.

[ptuomov]

' power required to turn the shaft'

You are speaking 'For Dummies' fluently.

Corrected flow rate thru the turbine and the pressure ratio determine how much power the turbine extracts. Before the boost threshold is met, it’s just that. When the boost threshold is met, then the wastegate opens and one needs to estimate the mass flow thru the wastegate circuit.

This is the simplest way to both do it and to explain it, at least that I know of.

[The Californian]

'Corrected flow rate thru the turbine'

What does that mean?

' pressure ratio'

Same question.

'boost threshold'

What is that please?

[ptuomov]

'Corrected flow rate thru the turbine' What does that mean?
'pressure ratio' Same question.
'boost threshold' What is that please?

Yeah, ok.

General turbo tech:
https://www.garrettmotion.com/turbochar ... ks/expert/
https://www.garrettmotion.com/wp-conten ... pert-1.pdf

Corrected mass flow explanation:

Corrected mass flow is a measure of how much exhaust gas goes thru the turbine over a period. The pressure ratio is a measure of how much more (absolute) pressure there is in the turbine inlet vs. the turbine outlet. If more exhaust gas flows thru the turbine at the same pressure ratio, more work the compressor in the other end of the shaft can do. Similarly, if the pressure ratio over the turbine is higher, then at the same flow rate the turbine can extract more and compressor consume more power.

I use the word "boost threshold" to mean a condition where the intake manifold pressure meets the desired set point. It's loose terminology, take it to mean the point where you want to open the wastage. Even partially open wastegate means that both the pressure ratio over the turbine is lower and the mass flow is also lower, leading the compressor to doing less work than it would do with the wastegate closed, holding a bunch of other stuff constant.

Someone else should take a crack at explaining this, in case I'm either being imprecise or giving a too complicated explanation (or both).

[The Californian]

'It's loose terminology, take it to mean the point where you want to open the wastage'

You are getting warm.

Sent you a PM.

To stay on point here let me say this.

It seems like there would be a rating or a requirement for the turbine as far as this:

How much volume of exhaust does it need to spin it to it's maximum RPM?

Then you deal with what compressor you hang on the other end of shaft.

Thank you.

[Orr89rocz]

Thats not really how it works tho, the compressor gets attention because its what matters most. It gives the air flow you wish to have to make the power you desire to make, and because of that the shaft speed is set.

Turbines are always matched to provide the power to turn the compressor at that rpm. I think turbines are abit harder to understand. Exhaust temp has a big part in how the turbine operates and exhaust mass flow. These vary on engines depending where the turbo is located, the size of engine and fuel used etc. compressors just take atmospheric air and compress to a final pressure. Much easier to estimate its performance imo

[HiPer Express]

Here you see real turbine map from BW , they are usually not released for public because most dont understand them anyway. https://motoiq.com/turbo-tech-compresso ... p-details/

[77cruiser]

You are right about not understanding.

[ptuomov]

Here you see real turbine map from BW , they are usually not released for public because most dont understand them anyway. https://motoiq.com/turbo-tech-compresso ... p-details/

I think that the full turbine maps aren’t used for that reason, sure, but also for the reason that the efficiency and other measures of the turbine operation aren’t terribly sensitive to the shaft rpm. Because of this, it’s in my opinion ok to just show a graph wit a curve that connects the peaks of these mini-curves:

3AF3F303-CCCF-4BFF-B8B0-4B8EEFAF2910.gif