Mechanical losses through turbos

[hugodc]

Ive got given the above as a title for part of a uni project and am struggling to find books or good info on the subject so any recomendations for reading or general info you want to share would be greatly appreciated.

thanks

[GreenV8S]

Never mind books, I have no idea what the title means. Turbos are not typically driven mechanically so the concept of mechanical losses doesn't make sense. If you can't work it out from the context I suggest you ask the person who set you the problem. If all else fails you could always re-read your course notes, it's a long shot but just barely possible they cover the subject they're asking you to do your project on.

[Fort Jefferson]

hugodc said:

.....and am struggling to find books or good info on the subject......

thanks

Corky Bell, Maximum Boost.

[Boosted LS1]

The losses may be pumping losses in the cylinders due to extra cylinder pressure, easily recovered though plus a lot of extra torque and HP. Could this be what the OP is looking into? If so, it's completely variable depending on the base engine specs, turbo specs, boost levels etc etc.

ETA, it's more likely a supercharger related question because of the crank to s/c connection.

Edited by Boosted LS1 on Sunday 8th November 17:16

[hugodc]

main mechanical losses are through bearings and seals so thats what ive got to look at,
Ive tried maximum boost and although interesting it i not very theoretical and is just based observations

[GreenV8S]

So basically you're investigating drag within the turbine? How big a project is this? If this is only part of a bigger project I can't imagine they expect you to go into much detail. What aspects are you expected to cover? Why the drag is important (impact on performance)? How much drag there actually is? Options to minimise it? There's scope for this to cover a huge amount of ground.

[hugodc]

Its the drag with in the mechanical parts that link the turbine and compressor- basically looking at how the frictionl losses change with shaft speed, temperature. Effects of different types of bearing configurations (i.e 2 plain bearings and a thrust bearing, angular contact bearings, ball or journel bearings)

[TheEnd]

In fairness, i think it's a fairly trivial point, but it's to show you can go out, study and research various factors, and i guess come up with a list of various ways to solve the "problem"

I think you starting point would be to ignore the turbo itself, and find out what the bearings and seals are, then search for drag in these vs speed and temperature, then go back and apply them to the turbo.

[GavinPearson]

I don't think it's trivial, for an Engineering student it is actually a useful project.

Read this:

http://books.google.com/books?id=h6X0NM7ME8IC&...

Then you probably want to give Holset / Cummins Turbo as they are now known a call:

http://www.holset.co.uk/mainsite/files/1_1_5-UK.ph...

[phumy]

Take a look in a book called, "Pounder’s Marine Diesel Engines and Gas Turbines Eighth edition" it has an excellent section on Pressure Charging and explains all mechanical losses, inc heat, bearings and thrust.

Can be found in Amazon but not cheap or im sure any decent uni or college library would have it.

http://www.amazon.co.uk/Pounders-Marine-Diesel-Eng...

[v8ian]

there are the obvious frictional losses within the Turbo, but there are also losses due to placing a restriction within the exhaust, if you run a NA engine you would build a free flowing exhaust without restrictions, if you ran an engine with a good exhaust, then ran the same engine with a turbo venting to atmosphere, you would get an idea of basic losses, then restricting the outlets measure boost, and calculate losses, and Im sure a turbo will upset scavenging effect of tuned length pipes, there must also be losses of gas speed [friction] within the plumbing boost side thru bends, joints, and intercoolers

[hugodc]

cheers guys, looks like those books could prove to be pretty useful

[Mave]

To give you a heads up, if you calculate more than a few % it's probably too high.

As an example, a gas turbine engine (which is like a turbo with a combustor in the middle!)has 10s of thousands of horsepower going down the shaft between the turbine and compressor, but only puts a few hundred horsepowe at most of heat into the oil system.

[phumy]

Mave said:

To give you a heads up, if you calculate more than a few % it's probably too high.

As an example, a gas turbine engine (which is like a turbo with a combustor in the middle!)has 10s of thousands of horsepower going down the shaft between the turbine and compressor, but only puts a few hundred horsepowe at most of heat into the oil system.

Actually the figure in modern gas turbines is nearer 40% efficient and thats a similar figure for turbo's too, the main losses on a gas turbine are, highest first:

Roughly;

35-40% = exhaust (heat)
5-10% = coolant
5-10% = charge cooler
5% = lub oil
5% = radiation

so you can see only around 30-40% is actaully work.

The gas turbines i work with are rated at 255MW each (they're monsters), so youre looking at around 335,570 Horse Power each, given that 1HP=0.745kW. However we dont suffer such great losses on the exhaust side of our gas turbines as we recoup the heat in a steam generator and run a steam tubine on from the waste heat, which gives us an overall, station efficiency, of around 62% as long as were running at base load.

[The Black Flash]

Fort Jefferson said:

hugodc said:

.....and am struggling to find books or good info on the subject......

thanks

Corky Bell, Maximum Boost.

I've got his one on supercharging and it is excellent, so based on that, I'd second the suggestion.

[Mave]

phumy said:

Mave said:

To give you a heads up, if you calculate more than a few % it's probably too high.

As an example, a gas turbine engine (which is like a turbo with a combustor in the middle!)has 10s of thousands of horsepower going down the shaft between the turbine and compressor, but only puts a few hundred horsepowe at most of heat into the oil system.

Actually the figure in modern gas turbines is nearer 40% efficient and thats a similar figure for turbo's too, the main losses on a gas turbine are, highest first:

Roughly;

35-40% = exhaust (heat)
5-10% = coolant
5-10% = charge cooler
5% = lub oil
5% = radiation

so you can see only around 30-40% is actaully work.

The gas turbines i work with are rated at 255MW each (they're monsters), so youre looking at around 335,570 Horse Power each, given that 1HP=0.745kW. However we dont suffer such great losses on the exhaust side of our gas turbines as we recoup the heat in a steam generator and run a steam tubine on from the waste heat, which gives us an overall, station efficiency, of around 62% as long as were running at base load.

He wasn't asking about overall efficiency though (unless I misunderstood the question?) he was asking about mechanical losses - so get rid of exhaust, coolant, charge cooler, and radiation from your list. Then you get to 5% lub oil - some will be form mechanical losses, some will be from heat transfer into the bearing chambers - so not a million miles from the few % I suggested? Incidentally, I'm surprised that you're getting as much as 30,000 HP into the lube system - how big are the coolers?