What makes the BIG boats go ! Wartsila-Sulzer RTA96-C

[brian eiland]

Maximum power: 108,920 hp at 102 rpm

Maximum torque: 5,608,312 lb/ft at 102rpm


The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today. The Aioi Works of Japan 's Diesel United, Ltd built the first engines and is where some of these pictures were taken.

It is available in 6 through 14 cylinder versions, all are inline engines. These engines were designed primarily for very large container ships. Ship owners like a single engine/single propeller design and the new generation of larger container ships needed a bigger engine to propel them. The cylinder bore is just under 38" and the stroke is just over 98". Each cylinder displaces 111,143 cubic inches (1820 liters) and produces 7780 horsepower. Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the fourteen cylinder version.

Some facts on the 14 cylinder version:

Total engine weight:

2300 tons (The crankshaft alone weighs 300 tons.)

Length:

89 feet

Height:

44 feet

Maximum power:

108,920 hp at 102 rpm

Maximum torque:

5,608,312 lb/ft at 102rpm

Fuel consumption at maximum power is 0.278 lbs per hp per hour (Brake Specific Fuel Consumption). Fuel consumption at maximum economy is 0.260 lbs/hp/hour. At maximum economy the engine exceeds 50% thermal efficiency. That is, more than 50% of the energy in the fuel in converted to motion.

For comparison, most automotive and small aircraft engines have BSFC figures in the 0.40-0.60 lbs/hp/hr range and 25-30% thermal efficiency range.

Even at its most efficient power setting, the big 14 consumes 1,660 gallons of heavy fuel oil per hour.

[brian eiland]

The internals of this engine are a bit different than most automotive engines.

The top of the connecting rod is not attached directly to the piston. The top of the connecting rod attaches to a "crosshead" which rides in guide channels. A long piston rod then connects the crosshead to the piston.

I assume this is done so the the sideways forces produced by the connecting rod are absorbed by the crosshead and not by the piston. Those sideways forces are what makes the cylinders in an auto engine get oval-shaped over time.

Installing the "thin-shell" bearings. Crank & rod journals are 38" in diameter and 16" wide:

The crank sitting in the block (also known as a "gondola-style" bedplate). This is a 10 cylinder version. Note the steps by each crank throw that lead down into the crankcase:

A piston & piston rod assembly. The piston is at the top. The large square plate at the bottom is where the whole assembly attaches to the crosshead:

The "spikes" on the piston rods are hollow tubes that go into the holes you can see on the bottom of the pistons (left picture) and inject oil into the inside of the piston which keeps the top of the piston from overheating. Some high-performance auto engines have a similar feature where an oil squirter nozzle squirts oil onto the bottom of the piston.

[brian eiland]

The cylinder deck (10 cylinder version). Cylinder liners are die-cast ductile cast iron. Look at the size of those head studs!:

The first completed 12 cylinder engine:

[Zappi]

Brian. thanks for posting this. That is incredible and where else can you find such things than right here. Awesome!!!
Aaron

[brian eiland]

And we use to have the capabilities to build that sort of thing in the USA :rolleyes:

[pistnbroke]

dont divert the americans brian just keep them focused on the GPS !!!

[FAST FRED]

"dont divert the americans, brian just keep them focused on the GPS !!!"

OOOPS! The US Air Farce made another bo- bo, seems they didn't sked or fund enough replacement GPS sat builds or launches.

And the village idot from KENYA just canceled the entire LORAN system , that was backup for when an IMP knocks all the GPS out!!

Break our the sextants and old RDF folks looks like accurate navigation is on the way out.Paper charts may be back in vogue!

FF

[brian eiland]

Break our the sextants and old RDF folks looks like accurate navigation is on the way out.Paper charts may be back in vogue!
Don't throw away your paper charts! - GPS failings to come (http://www.boatdesign.net/forums/onboard-electronics-controls/dont-throw-away-your-paper-charts-gps-failings-come-27458.html#post275245)

[apex1]

The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today.

Thanks Brian.
But the largest and most powerful and efficient engine is still a MAN at 100MW output!

The reason for the crosshead is a much simpler (these slow turning, long stroke engines would´nt make the piston oval), the connecting rod would touch the cylinder if connected directly, due to the very long stroke!

http://www.boatdesign.net/forums/attachments/diesel-engines/31844d1242776190t-what-makes-big-boats-go-wartsila-sulzer-rta96-c-rta96-c.jpg

and the picture above shows a MAN B&W engine built in Germany.
btw: 70% of the worldwide merchant fleet is propelled by MAN diesels.
Regards
Richard

[Jimbo1490]

The reason for the crosshead is a much simpler (these slow turning, long stroke engines would´nt make the piston oval), the connecting rod would touch the cylinder if connected directly, due to the very long stroke!

http://www.boatdesign.net/forums/attachments/diesel-engines/31844d1242776190t-what-makes-big-boats-go-wartsila-sulzer-rta96-c-rta96-c.jpg


Regards
Richard


Even in the absence of a possible collision between components, a crosshead is often used in very large engines, especially, those with very low B/S ratio (which restricts R/S ratio by simple logistics :) ) because on engines with such architecture, the side loads on the cylinder become extraordinarily high causing excessive wear. The round cylinder's main function should be to contain expanding gases, not a sliding bearing surface. The crosshead is optimized for this function, which greatly extends the life of the cylinders.

Jimbo

[apex1]

Naturally wear is a issue and another good reason, but a 3 meter stroke (usual on these monsters) is just not to manage without a crosshead. So there is no "absence" of possible collisions. And that was found already by our grandfathers, they invented crossheads on steam engines for exactly that reason.
Regards
Richard

[FAST FRED]

The crosshead is optimized for this function, which greatly extends the life of the cylinders.


The EMD (Detroit) train engines use a 2 piece piston with a ratcheting gear that turns the piston a tiny bit on each stroke, to equalize the wear.

As large as a train engine is tho, it would probably drop into one cylinder of a ship mover.

FF

[Jimbo1490]

I was going to mention these. Actually EMD got the crosshead piston design from Cleveland Diesel, whom they absorbed after WWII. The EMD engines are 'only' 710 in^3 (11.7 liters) per cylinder, so yes, much smaller.

Jimbo

[Jimbo1490]

See Wikipedia's description of a crosshead. (http://en.wikipedia.org/wiki/Crosshead)

Jimbo

[apex1]

See Wikipedia's description of a crosshead. (http://en.wikipedia.org/wiki/Crosshead)

Jimbo


Thanks Jimbo!
nice example the "Wiki" fails quite often.
See a professional version of that issue:

http://de.wikipedia.org/wiki/Kreuzkopf

Naturally, as mentioned before, sideforces and the resulting tear and wear are one point (not that very much on a piston with a 2 meter skirt), but on a engine that size (we are talking about only one single engine here!!!), the first reason to have a crosshead is to make the engine design possible! Thats it! No crosshead, no engine that size.
Regards
Richard

[Jimbo1490]

In the absolute case it would always be possible to construct any such long stroke engine with a longer connecting rod and no crosshead. This is what i was alluding to in my first post when I mentioned logistical constraints. The connecting rod needed would be very very long indeed and make the engine unpractical and inefficient as the uber-sized connecting rod would result in very high reciprocating mass. Reciprocating mass is always a parasite on efficiency. This engine already looks to be 4 stories tall, so making it 8 stories is obviously out of the question :D

[apex1]

Took a while, but it seems we agree now....

[Jimbo1490]

Yes, of course. It's just that the wear issue is really just as big as the collision issue. The true crossheads (and even the quasi-crossheads, like with EMD and also Sulzer) appear even before collision becomes an issue, as it is in the really big boys. After all, It does no good to build an engine costing millions of Euros that only lasts for a couple of thousand hours before needing new cylinders, so crossheads are needed also to make these engines practical.

Jimbo

[apex1]

Nothing to complain!

[AlbaDiesels]

The crosshead is optimized for this function, which greatly extends the life of the cylinders.


The EMD (Detroit) train engines use a 2 piece piston with a ratcheting gear that turns the piston a tiny bit on each stroke, to equalize the wear.

As large as a train engine is tho, it would probably drop into one cylinder of a ship mover.

FF

The Wartsila ZA40 uses a similar rotating piston design. It has a spherical bearing with a ratchet mechanism that rotates the piston.

Have a look here http://www.marinediesels.info/4_stroke_engine_parts/The_4_stroke_piston.htm