Turbo Compounded 3 rotor by Paul Lamar

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Will Aldridge

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This project was one Paul Lamar was working on a few years ago and back burnered it for various reasons. He hooked a Detroit Diesel 15 Turbo to a 3 rotor 20B driveshaft to create a Turbo Compounded engine as a demonstrator. It was not suitable for flight as he says just to demonstrate the technology. I had forgotten about it till it came up in discussions about his Time to Climb record attempt and he posted some pics. Below is quoted from his email list about it:

I put a turbo compound on a three rotor. I was invited to the World
Motor Sport Symposium and talked the Formula 1 crowd into turbo
compound so there was no need for me to dyno mine. Mercedes,
Renault, Ferrari and Honda have built dozens of turbo compound
engines, dynoed and raced them in 30 or so races for the past three
years.

Turbo compound is rumored to become available on the RX9.

If so I achieved my goal.

My guess is we are throwing away half the exhaust energy in the TTC
engine.

Paul Lamar

Does that mean you’ve abandoned your three rotor turbo compound
project, Paul?

Dave Klingler

It is way on the back burner. This set up is not suitable for an aircraft.

I would work in a boat.

Do you want to buy it? I'll sell it for $11,000 as is.

I'll deliver in the lower 48. Cost depends on where you live?

Paul Lamar


DD15-turbine [14565].jpgcat-turbo-compound-RPM-V-Temperture [14562].jpgP1140766 [14568].jpg3-rotor-DD15-TC [14559].jpg
 

wsimpso1

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The big successful turbo-compound engines had fluid couplings in torque path back to the crankshaft. Why? Because the torque that can be produced by a turbine is is proportional to the rpm squared, which means that the turbine and compressor would have to be VERY carefully matched to the powerplant to be very good at just one engine speed and power setting per altitude, or only along one curve of altitude, engine rpm, and power setting. To make it good over a wider range going from climb power to cruise power to approach/descent power, they incorporated a fluid coupling, which allowed the turbine to run where it had to, transmitted all of the spare torque to the crankshaft, and wasted power only in proportion to the 1 minus the Speed Ratio of the fluid coupling. Yeah, a lot of waste heat had to be handled, but it was better than finding your self with a turbine and compressor running at a set ratio to the engine speed that is way off of optimal under almost all operating conditions.

The upshot is that this turbo compound of Paul's is likely to have no more than one place in the operating range that works well, and everywhere else, it will hinder the turbos... Ugh.

Billski
 

Billrsv4

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The big successful turbo-compound engines had fluid couplings in torque path back to the crankshaft. Why? Because the torque that can be produced by a turbine is is proportional to the rpm squared, which means that the turbine and compressor would have to be VERY carefully matched to the powerplant to be very good at just one engine speed and power setting per altitude, or only along one curve of altitude, engine rpm, and power setting. To make it good over a wider range going from climb power to cruise power to approach/descent power, they incorporated a fluid coupling, which allowed the turbine to run where it had to, transmitted all of the spare torque to the crankshaft, and wasted power only in proportion to the 1 minus the Speed Ratio of the fluid coupling. Yeah, a lot of waste heat had to be handled, but it was better than finding your self with a turbine and compressor running at a set ratio to the engine speed that is way off of optimal under almost all operating conditions.

The upshot is that this turbo compound of Paul's is likely to have no more than one place in the operating range that works well, and everywhere else, it will hinder the turbos... Ugh.

Billski
Bill,
While I often consider Paul's turbo compound items flights of fancy, this one actually had/has some real parts and some practical possibilities. It was only a test bed for the compounding turbine and the gearbox. I'm with you that it would be wise to have some form of overrun clutch or coupling to only have the turbine coupled when it is making power. (which is difficult) Since the supercharging turbo/s have first crack at the exhaust flow and no direct connection to the compounding turbo I don't believe they would be appreciably hindered by the compounding turbine. Most engines still use a muffler downstream of the supercharging turbo. Especially on a rotary! The compounding turbine would be returning some of that energy. What Paul has constructed has the possibility of working as a proof-of-concept example. Yes it might only produce ADDITIONAL power at specific RPMS but it would be a minimal restriction. If directly coupled you would need to drive it up at low RPM but I think it would be worth testing. Yes T.C. has and does work, but is rarely simple. (And believe me that I am as reluctant as you to give tacit agreement to many of the ideas that pop out of many heads, including Paul's)

The other Bill
 

Vigilant1

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It would seem that the tricky and expensive part is smoothly getting the mechanical power back into the main drive system to turn the prop. The "low hanging fruit" would be to at least use the available energy in the Wankel exhaust (via a turbine wheel and gearing) to do "other stuff:"
-- Forced induction (i.e. the traditional role of a turbocharger)
-- Make electrical power for the aircraft (and a lot would be available, maybe a few dozen HP, for "free," aside from the weight of a larger alternator)
--- Provide cabin pressure
--- De-icing
--- Fun extra credit project: Limited electric hybrid drive (e.g a 10 HP electric motor with an 18" prop. Speed of motor is electronically controlled to provide an RPM adjusted for airspeed so that it is always "pulling." Small prop diameter keeps the tips subsonic even at high RPMs.) Even 10-20 lbs of thrust at climb and cruise would be welcome and will cut the fuel flow a bit.
-- etc.

Every bit of accessory load taken off the main engine and moved to the TC system frees up more power to turn the prop.
 
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Himat

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Maybe not all low hanging fruit, but today I think the way to go with turbo compound would be to generate electricity with the turbine and maybe spin a compressor for supercharging and cabin pressure. The electricity could then be feed to an electric motor on the same shaft as the internal combustion engine. This would look part like the Rotax hybrid drive. The load on the exhaust turbine would then be controlled by regulating the generator and the loads. No easy engineering as the internal combustion engine is part of the control loop too. Still, it might be possible and it could squeeze a little more fuel efficiency.
 

wsimpso1

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It would seem that the tricky and expensive part is smoothly getting the mechanical power back into the main drive system to turn the prop. The "low hanging fruit" would be to at least use the available energy in the Wankel exhaust (via a turbine wheel and gearing) to do "other stuff:"
-- Forced induction (i.e. the traditional role of a turbocharger)
-- Make electrical power for the aircraft (and a lot would be available, maybe a few dozen HP, for "free," aside from the weight of a larger alternator)
--- Provide cabin pressure
--- De-icing
--- Fun extra credit project: Limited electric hybrid drive (e.g a 10 HP electric motor with an 18" prop. Speed of motor is electronically controlled to provide an RPM adjusted for airspeed so that it is always "pulling." Small prop diameter keeps the tips subsonic even at high RPMs.) Even 10-20 lbs of thrust at climb and cruise would be welcome and will cut the fuel flow a bit.
-- etc.

Every bit of accessory load taken off the main engine and moved to the TC system frees up more power to turn the prop.
There is more too it than just that. The engine is trying to accelerate and decelerate with the power pulses while the turbine is trying turn a steady high speed. The turbine with its gearing will act as a big flywheel to tone down the accelerations, but the gear set will see the torque from it. Unless the gearset is really sturdy, it may not run long enough to even get good data on the engine...
 

Vigilant1

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There is more too it than just that. The engine is trying to accelerate and decelerate with the power pulses while the turbine is trying turn a steady high speed. The turbine with its gearing will act as a big flywheel to tone down the accelerations, but the gear set will see the torque from it. Unless the gearset is really sturdy, it may not run long enough to even get good data on the engine...
We may be referring to different things. I'm suggesting that the exhaust-driven turbine be used to drive a compressor (for induction air--i.e. a conventional turbocharger) and also an (big) alternator that takes the place of the "regular" engine driven alternator. In this way there is zero "hard" mechanical connection from the exhaust-driven turbine to the main mechanical drive, we use the electricity from the large alternator to reduce the load on the main drive. That electricity runs the normal ship's power, could provide pressurized air, electric heating to de-ice leading edges, and could even run an electric motor to turn a separate prop (or, I suppose, provide torque to help turn the main prop, reducing fuel burn for a given RPM). Going from mechanical to electrical and back to mechanical will not be especially efficient, but the power is essentially "free", and avoiding a hard, direct mechanical link to the prop avoids some complexity and the problems you've pointed out.
 

wsimpso1

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I am not talking about other schemes for making use of an exhaust driven turbine, I am talking about getting the power from the turbine fed back to the crankshaft. That is turbo compounding.

Turbo-generator hybriding is way more complicated to manage, but if you can talk Paul Lamar into running it, go for it.

Billski
 
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