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running turbine directly to crank
3

running turbine directly to crank

running turbine directly to crank

(OP)
In doing some research I ran across some info relating to the use of a turbine(s) linked directly to the crankshaft. Application was the Wright Cyclone 3350TC radial aircraft engine. Three exhaust driven turbines were mechanically linked to the crank. Without this feature the engine was rated at 2,700 take off HP. amd BSFC was .45lbs/hphr. Turbines in place boosted power to 3,500hp (3,700 in Navy applications) and BSFC was reduced to .35lbs/hphr. Also there was a patent issued in 1959 for a turbine (looks like the turbine side of a turbocharger) geared to the flywheel on a diesel engine application. My question is anyone aware of any attempt to adapt this concept to a land or sea based engine? It would appear to be a logical addition to gain power,fuel economy, and be rid of the lag normally associated with turbos. Any thoughts?------Phil

RE: running turbine directly to crank

Those 3 turbines, on the R-3350. Were not connected directly to the crankshaft. The shafts first went through fluid couplings, to isolate the crankshaft vibrations.
Each turbine on that AC engine, recovered about 300 hp.
I agree with you, it is a great way to get more power out of a gallon of fuel. Since more than a 3rd of heat is lost in the exhaust. But what would keep it out of the automotive sector is, cost. I think it has been done on marine engines.

RE: running turbine directly to crank

Effectively this is already used on ships. In fact modern naval ships use a bewildering range of prime mover arrangements, to give good cruise range and high potential top speed in the minimum hull volume.

Here's a few of the current options:

    CODAG   = Combined Diesel and Gas (turbine) propulsion
    CODOG   = Combined Diesel or Gas (turbine) propulsion
    CODLAG  = Combined Diesel-Electric and Gas (turbine) propulsion
    COGAG   = Combined Gas (turbine) and Gas (turbine) propulsion
    COGOG   = Combined Gas (turbine) or Gas (turbine) proplulsion
    CONAS   = Combined Nuclear And Steam (turbine) propulsion
    COSAG   = Combined Steam (turbine) and Gas (turbine) propulsion

There are many many more ( I think about twenty, last time I saw a full list) most of which are concerned with taking the waste heat from one process and using it generate power.

It is unusual to find a turbo installation on a gasoline engine that is more efficient than the base engine, but it is quite common with diesels.

Depending on the power balance in the system, it can be convenient to think of the piston engine as being the first compression/burn/expansion part of the rest of the turbine.
 

Cheers

Greg Locock

RE: running turbine directly to crank

The engine you mention was used in the Lockheed Constellation, best known for its triple vertical stabilizer arrangement. It is true that it added about 700 hp to each engine, which was about a 20-25% increase in output.

But the Constellation worked in an environment somewhat different then the typical marine/land application; it typically was above 20,000 feet. The atmospheric pressure at 18,000 feet is one half what it is at sea level. The turbine was working against much less pressure than it would have been at sea level. This resulted in recovery of quite a bit more energy than would have been possible otherwise.

I might also note that the exhaust turbine wasn't completely reliable, as the Connie's engines had a terrible maintenance record.

When you pencil it out, you will only get about a 5% increase in power in diesel engines when you add an exhaust turbine.

RE: running turbine directly to crank

SBBlue - 5% is about two grannies worth of improvement, according to another thread.

Cheers

Greg Locock

RE: running turbine directly to crank

(OP)
Many thanks to all who have responded. I'm impressed enough with the #'s from previous efforts to want to give it a try. Maybe I won't have to sell family members into slavery.( However I'll gladly trade some efficiency if someone would take my mother in law off my hands). I also plan to use the cooling system to generate steam fed into the same turbine. I'm headed down the home stretch on this project. I'll report back when the #'s become avaiable.----------Phil

RE: running turbine directly to crank

Another engine that uses a crank coupled exhaust turbine is the Napier Deltic. These amazing engines are hard at work all over the world in all sorts of applications.

RE: running turbine directly to crank

And the powerplant of choice in electrical generation is steam and/or gas turbine compound systems.

That doesn't mean that either is suitable for a car or light truck.

Aircraft and power plants run at constant speed most of the time, at a large percentage of rated power. Autos and light trucks spend most of the time running at small percentages of rated power. I think that most of these 'bottoming cycle' devices really work at the top end of the power curve. There are easier and cheaper ways to get a bit more power at the top end, when it is only needed occasionally.

Actually, as hybrids improve, perhaps in concert with CVTs, the compounding may make more sense. You then have a smaller engine running in bursts at a higher percent of rated power, and at a nearly constant speed.

cheers
Jay

Jay Maechtlen

RE: running turbine directly to crank

funny one greg

RE: running turbine directly to crank

:)

RE: running turbine directly to crank

Jay, does a gas turbine or steam turbine, come close to 50% efficency?
This does.  http://www.bath.ac.uk/~ccsshb/12cyl/
My understanding is a gas turbine is the most ineffient engine there is. I suppose BSFC is better now than it was in years past though. I though I had read some place that the navy was replacing gas turbines with recips.

RE: running turbine directly to crank

No of course they don't. Gas turbines are used for power to weight ratio and small footprint and reliability and low cost,  not economy.

Steam turbine plants would be lucky to hit 35% efficiency at best, and on a ship things would be even worse.

BTW you should also consider when the engine is efficient - a gas turbines part throttle performance is terrible, wheres a diesel works fairly efficiently over a wide range of loads.

Cheers

Greg Locock

RE: running turbine directly to crank

"small" gas turbines are not very fuel-efficient.
"small" steam engines are worse.

big steam turbine power plants are pretty good.
big gas turbine power plants likewise.

(Greg - in school, 20+ years ago, we were told 35-40% was state of the art. It ain't any more!)

http://www.siemenswestinghouse.com/en/press/pg200303017...
"...The Huntstown combined-cycle power plant in Ireland attains an efficiency level of over 55 percent, making it the country's most efficient plant.
...
For the Huntstown multi-shaft plant Siemens PG supplied one V94.3A gas turbine, one steam turbine and the two generators. If the power demand is significantly lower than plant output, the gas turbine-generator in this versatile type of plant can also be operated alone. In so-called open-cycle operation a around of 220 megawatts are generated."

ok?

Jay Maechtlen

RE: running turbine directly to crank

I agree combined cycle plants can be much more efficient than 'pure' cycles, I was talking about a conventional steam turbine, ie  the efficiency of the 'cycle'

fuel burned->steam->turbine->shaft power

http://www-waterloo.ansys.com/cfx/PDF/PDF0378.pdf

claims 48.5% for the turbine itself, which needs to be multipled by the boiler efficiency etc, for which I have a ballpark figure of 88%

So, yes, 35% was too low, it looks like 43% is now achievable.

Cheers

Greg Locock

RE: running turbine directly to crank

Auto engines usually run 500 to 5000 RPM. The 3350 crankshaft probably ran a considerably more limited range. The prop was geared down and I don't know the ratio or if the engine ratings are crankshaft or propshaft, but the turbine wheel has a limit that 5000 Rpm could exceed.
Pancholin

RE: running turbine directly to crank

Hello ,

I'm new to this forum and I have been researching preparing to test a turbo compound system on a three rotor mazda engine that will go in my aircraft.  I'm in the process of searching for the turbine and designing an oiled cooled helical gear box and clutch so that I can divert power to the e-shaft when over 50% power.

It is possible.   The turbo can and does put out from 10 to 30 Hp over the needs to drive the compressor.
I am finding delivering it to the eshaft may be tricky but I have a few theories on what is happening.

DouginJapan

RE: running turbine directly to crank

Why not connect the turbine to an alternator?
You can draw off excess power, and when you need a boost,
cut the field current to the alternator.  That will sudden
drop the load on the turbo

RE: running turbine directly to crank

so basically this engine would run similar to a turbo prop with the pistons being the compressor.  it looks on those auto cad drawings that the turbine was not geared down.  seeing how the turbine on a regular turbo charger spins much faster than the crankshaft of the engine, would the air craft engine in question be made more efficient if there was some sort of gear ratio between the turbine and the crank?  if i imagine this correctly this would allow the turbine to spin faster, and with the gears would apply more torque on the crank shaft.  
Another question is could that turbine be used to replace the flywheel on a formula one car?  the turbine would keep the crank spinning against compression and would allow the engine to be more responsive due to the lack of flywheel mass.   just a hunch.

RE: running turbine directly to crank

what flywheel would that be exactly?

Cheers

Greg Locock

RE: running turbine directly to crank


Hello  microhenry.

Good idea.  I share your thoughts.

This is how Catapillar does turbocompounding. They are also exploring electro-turbo generation.

http://www.westwardscania.com/trucks/NTR/technology/turbocompound/how_does_it_work.asp?ComponentID=43343&SourcePageID=56704


My engine has two much potential to just go just with the generator feeding a flywheel motor however.  I am talking about recovering from 35 to 50Hp.  A electric motor in that catagory is large, heavy, high voltage, with expensive  heavy controller and probably if  the motor is anything like some of the hybrid cars it will be high voltage and in need of a buffer battery.  I explored that road already.  

Lovely concept but beyond the weight/performance of the long distance flier.  Short trips in a motor glider are being done now with hybrid and all electrics.

My n/a 300 hp engine has one low rpm high torque turbine connected to a gearbox with two outputs. One output uses through a small carbon fiber shaft does something like you suggested for controlling the boost pressure (compressor rpms) by clamping the field on the attached generator.  This energy can be sent to the alternator/starter motor that resides where the flywheel was, thus  technically making the engine a hybrid in this flip mode.  The other shaft sends the rest  of the torque through a step down set of gears to a foward running electric clutch and cogged belt pully to the drive shaft at slightly higher rpms.  The belt absorbs slight torque variations that would normally destroy gears.
If you think about it the concept is the same as Catapiller but I am going about it in a different manner,
with the generator thrown into the mix.

I am still in the testing phase but what appears to happen at some power settings is that the additional torque added to the engine power makes the engine speed up to try and match the turbo compound output rpms.  If the rpm overage is set a the right parameter the engine never  catches up but the increased rpms indicate an increase in performance.
 The turbine must be bogging down very slightly but  still we are talking about small efficiency losses  for a large gains in BSFC.  
 
The real test is to get  the engine off the dyno installed in the plane and flying.  Some parameter will change no
doubt. This depends how high  and fast I fly, the air density,  or in short how much boost I want to give the engine. More boost more fuel and more Hp. Also more  turbo power output.  Magically  the efficiency curves show the excess energy (after boost) is greater the higher the rpm.  Before we get to excited we have to remember the DRAG on the airplane also increases.

Efficiency sweet spots differ from plane to plane.  Since I am running 95% pure ethanol, my long distance record attempt will be at 130 to 140 mph using  a high compression three rotor wankel engine with a slight boost to 'normalize' the engine up the 8,000 ft density altitude I will fly at.   The engine will be at 40 to 50% rated output and the turbo compound system will be designed to operate in that narrow range.  80% or the remaining energy will go to the compound. At these setting I could see from 10 to 20% increase in BSFC.

For aircraft operation the engine rpm can be controlled by changing the propellar load (called pitch) .  Thus the plane can fly faster at the same fuel burn rate or remain at the same speed and extend range.  

I am now searching for ways to reduce the size of the gear box , and sourcing gear manufacturers.

Have a great  new year.

Doug

RE: running turbine directly to crank

"Warpspeed (Automotive) Dec 12, 2003
Another engine that uses a crank coupled exhaust turbine is the Napier Deltic. These amazing engines are hard at work all over the world in all sorts of applications."

Check out the Napier Nomad, 0.345 lb/ehp/hr.
http://www.home.aone.net.au/shack_one/nomad.htm

RE: running turbine directly to crank

That Nomad engined was certainly an incredible piece of engineering to be sure, but by all accounts it was a real dog to get started. Cost and complexity were probably its undoing.

Further development of the gas turbine really put it out of business.

The Deltic engine is still in marine use, the Australian navy have many, and they are used in locomotives.

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