Supercharger stageing, compounding,

[Bville701]

hummm it seems to me airplanes need compounding and or staging because at the altitude they operate in there is no "air"!... down here on earth i don't see the benefit... my motors work well at 30 lbs boost, at 36lbs the head castings start to give up... we really don't need to talk about 60lb spikes....hahahahahahah
Kent

Kent,

The salt flats are about 4000 ft. above sea level. Is that not a high enough altitude to need/try compounding and or staging?

[1212FBGS]

naah i don't think so..... maybe 15k or better you should look at it.... now unless you have big displacement like Dunn's or Heaps diesels that move huge amounts of air, you can probably get all the boost through a conventional systems
Kent

[McRat]

hummm it seems to me airplanes need compounding and or staging because at the altitude they operate in there is no "air"!... down here on earth i don't see the benefit... my motors work well at 30 lbs boost, at 36lbs the head castings start to give up... we really don't need to talk about 60lb spikes....hahahahahahah
Kent

Kent,

The salt flats are about 4000 ft. above sea level. Is that not a high enough altitude to need/try compounding and or staging?

Let's say you get 9000' air (hot + altitude) at Bonneville, that's about 10.5psi absolute.  The best single chargers start to slide off the top of the map (overspeed) at 5:1 pressure ratio, but more typically, 4:1 for most common sizes.  Using 4:1 for "safe", that would be 45psi at sea level on a boost gauge, but only 32psi on a boost gauge at 9000' (open port gauge).  Last year, I think it was 6500' during SW, so uh, guess 35 psi?  If you really plan on running over 32psi boost, staging might start to help.

[Rex Schimmer]

I think that we need to define the difference between compounding and staging. I consider staging as multiple blowers in series, the diesel tractor pullers do this to get their 125 psi + manifold pressure. I consider compounding to taking power from the exhaust gases and connecting it to the engine output shaft. Just like the PW R 3350 engine. You can actually do a compound motor by staging a big turbo into a roots blower that is directly driven by the engine. If the turbo is big enough the inlet pressure to the roots blower will be higher than the outlet pressure and therefore it has turned onto a motor which is driving the engine directly. This is why the GMC two stroke diesel engines work so well.

Some day when I have an "pile" of money I am going to put one of the large centrifugal blowers on an engine and also the run the engine exhaust into a large turbo hot section, then connect them with a drive shaft. Instant compound motor with available parts. Once the turbine makes enough power to turn the blower every thing above that is extra horse power that would go right back into the engine crank by the drive belt. Remember at 60000 rpm you only need to transmit 100 inch lbs of torque to make 100 horse power so we are not talking about big stuff here.

As I have always said: "  Only money and time prevent me from completion"

Rex

Mike,
Looks like you must have worked at the "Bomb Factory" with Van Dyne, did you know Alan Brickey? I worked with him at Interscope. Drake Engineering did a small 60 inch 3 cylinder engine for one of the drones and and it had either a double or triple staged turbo for operation at 70,000 feet and  I remember that the engine weighted around 100-125 lbs and the blowers weighted about 150! Might be a little off in the weights but the blowers definitely out weighted the engine.

[Dynoroom]

Yep, I know Alan & Stewart very well.

I wish people in land speed racing had some real racing background and weren't just a bunch of shade tree mechanics.

/\    /\    /\    /\
 l      l     l      l   

The above was said with tongue firmly planted in cheek.   

[McRat]

I think that we need to define the difference between compounding and staging. I consider staging as multiple blowers in series, the diesel tractor pullers do this to get their 125 psi + manifold pressure. I consider compounding to taking power from the exhaust gases and connecting it to the engine output shaft. Just like the PW R 3350 engine. You can actually do a compound motor by staging a big turbo into a roots blower that is directly driven by the engine. If the turbo is big enough the inlet pressure to the roots blower will be higher than the outlet pressure and therefore it has turned onto a motor which is driving the engine directly. This is why the GMC two stroke diesel engines work so well.

Some day when I have an "pile" of money I am going to put one of the large centrifugal blowers on an engine and also the run the engine exhaust into a large turbo hot section, then connect them with a drive shaft. Instant compound motor with available parts. Once the turbine makes enough power to turn the blower every thing above that is extra horse power that would go right back into the engine crank by the drive belt. Remember at 60000 rpm you only need to transmit 100 inch lbs of torque to make 100 horse power so we are not talking about big stuff here.

As I have always said: "  Only money and time prevent me from completion"

Rex

Mike,
Looks like you must have worked at the "Bomb Factory" with Van Dyne, did you know Alan Brickey? I worked with him at Interscope. Drake Engineering did a small 60 inch 3 cylinder engine for one of the drones and and it had either a double or triple staged turbo for operation at 70,000 feet and  I remember that the engine weighted around 100-125 lbs and the blowers weighted about 150! Might be a little off in the weights but the blowers definitely out weighted the engine.

I think the resistance to "compounding" turbochargers, is because in that definition of compounding, you have a single turbocharger and a gas turbine combined.  A hybrid between a true internal combustion engine and a turbine driven engine.  Stage the turbines, and you have a turboshaft engine and can discard the pistons.

[jl222]

  McRat

   On the R3350 as the diagram shows there is no compressor on the turbine all the energy goes back to the crank. Supercharged air is supplied by a large centrifugal mounted on rear of motor.Previous engines had two turbochargers blowing into the centrifugal [13 in. inpeller] ''stageing'' + water injection.

     JL222

[jl222]

  Rex

  This is one reason I started this topic, to get people thinking about different ways of supercharging and to inform racers on turbo compounding. A lot of magazines have articles on blowing one supercharger or turbo or two turbos into another and call it compounding when its actually stageing. I really don't think they know what the WW2 aero engines accomplished.

  JL222

[McRat]

  Rex

  This is one reason I started this topic, to get people thinking about different ways of supercharging and to inform racers on turbo compounding. A lot of magazines have articles on blowing one supercharger or turbo or two turbos into another and call it compounding when its actually stageing. I really don't think they know what the WW2 aero engines accomplished.

  JL222

Perhaps the semantic problem lies in what to do with sequential turbocharging.  Several different engines have been sequentially turbocharged, which is not "staged", or is it?  One charger is for low CFM, then the second, larger charger kicks in to extend the effective map width.  It doesn't amplify boost, but there are two turbo in line with each other.  So for certain types of competitions where "staged" turbocharging is common, they adopted the term compound turbocharging to separate it from sequential or parallel twins.

PS - I will stop using the term Compound Turbocharging in LSR circles. 

[Rex Schimmer]

JL222,
I never knew that the R3350 was a compound engine until I was visiting the SAC meusum in Omaha, Nebraska several years ago  and was standing under the engine if a B29, got to looking at some of the details and I could see this small tubine that was driven by a couple of cylinders, it went into a small gear box then a long shaft ran down to the main shaft. Really pretty neat!!

The compound engine was the prerunner of the gas turbine, once they found out that they could get more power out of the turbine than the engine they just went to a combustion chamber for the hot gases and "Bobs your uncle" you have a gas turbine!

Rex

[interested bystander]

Since Ricardo was brought up in another post, in "The High Speed Internal Combustion Engine" Sir Harry proposes tying an exhaust compresser into the driveshaft as Rex mentioned wanting to do. Energy is energy, why waste it?

Some of his sleeve valve ideas are bit hard to buy. Technology seemingly has passed them by. 
(Although the Hawker Sea Fury planes might have had Bristol sleeve valve engines in them and they was FAST.

[McRat]

If someone were to look for one of the 3350 recovery turbines, where would you begin to look?

I assume the power calculations were done based on a comparison to conventional turbocharging?  If it was running a centrifugal supercharger, it consumed crankshaft HP, then the recovery turbine drives the crankshaft.  It sounds like a conventional turbocharger with an extension of the center shaft.  The Holset system uses a normal turbocharger, then it recovers some extra HP with a second turbine.  It's not much IIRC, about 20 hp.

[McRat]

Couldn't find the Holset system, here's the Volvo OTR truck system.  They call it turbo-compound technology? 

http://www.theicct.org/documents/Greszler_Volvo_Session3.pdf

[McRat]

I should have read all the way to the bottom.  The E turbocompound system looks like the cat's meow, and should be legal since it doesn't actually drive the crankshaft.  It has an electric motor/generator in the center of the turbocharger.  When you want to use it for turbine recovery, you switch it to generator, when you want to get instant boost on demand you turn it to motor mode.  No more turbo lag.

[McRat]

What puzzles me on the first Volvo design (normal turbocompound) is why the drive recovery turbine 100% of the time.  They say in low load applications, it causes parasitic losses and poor exhaust after-treatment temps, but if they would have driven it from wastegate gases instead, the losses would negligable at low throttle, and kept the exhaust temps up.  Only under high load would the recovery turbine add some power.

In any case, they see only 5% gains in power output due to the "cost" of running more backpressure to drive the turbine.