running turbine directly to crank 3

[SMOKEY44211]

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

 

[enginesrus]

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.

 

[GregLocock]

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

 

[SBBlue]

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.

 

[GregLocock]

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

Cheers

Greg Locock

 

[aorangi]

Beautiful CAD pics of the R-3350 here:

http://www.enginehistory.org/vicenzi.htm

It was also proppelling the the DC7s

Vovo and Scania produce turbocompound truck's engines.

Turbocompounding history here:

http://www.histomobile.com/histomob/tech/2/113.htm

Cheers
Aorangi

 

[SMOKEY44211]

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

 

[Warpspeed]

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.

 

[JayMaechtlen]

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

 

[Andy330hp]

funny one greg

 

[Andy330hp]

 

[enginesrus]

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.

 

[GregLocock]

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

 

[JayMaechtlen]

"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/pg200303017e/index.cfm

"...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

 

[GregLocock]

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

 

[Pancholin]

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

 

[DouginJapan]

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

 

[microhenry]

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

 

[MechAeroAuto]

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.

 

[GregLocock]

what flywheel would that be exactly?

Cheers

Greg Locock