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The World's Most Powerful Diesel Engine
trex279 writes "The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the world's most powerful diesel engine built to date. Each cylinder displaces a whopping 111,143 cubic inches (1,820 liters, equivalent to a cube 4 feet on a side) and produces 7,780 horsepower. The engine is about the size of a small building." The engine is intended for use in container ships.
Not even close to as bad as gas. Gas 2 cycles have nasty problems due to the lube oil being in the gas (doesn't burn well, otherwise it wouldn't lubricate) and the intake/exhaust ports being open at the same time (and hence you get unburned crap blowing right through). All of this is for simplicity, and it does work. A 2 cycle gas engine is an exceedingly simple contraption, and will almost run in spite of anything you do to it.
2 cycle engines are very common once you start moving up into the larger diesels. They're very different creatures, though they operate on similar principles. Diesel 2 cycles have separate lube oil in the crankcase, similar to 4-cyc gas engines. Thus, no continuous cloud of semi-burned lube oil coming out. Also, they're all (at least all that I've ever seen) direct injected, meaning fuel is delivered directly to the cylinder once the intake/exhaust ports are closed, thus no unburned fuel flows through.
Since diesel cylinder always get a full air charge, 2 cycle makes since - it's simple, and since you're only flowing air, you don't have the wasted fuel as in a gas 2cyc. As a by-product, you also get twice as much power from the same space as the equivalent 4 cycle at equal rpms. They do have more particulate problems, but these have been resolved well enough in the last few years to meet the new EPA Tier II diesel exhaust requirements.
vary the power output based on amount
The MAN B&W 14K98MC7 has nearly 8% more power (116,875 HP vs 108,920 HP for this Wartsila-Sulzer) http://www.manbw.com/engines/TwoStrokeLowSpeedProp Engines.asp?model=K98MC7
Great fact-checking to start 2007 with...
If you are talking diesel, one big engine, from my limited experience. This is due to the engine working at very low RPMS and in a ship, you are producing a steady load, not "start and stop" like driving a car in the city. Diesels also power down nicely and use fuel according to the load, so running at half of potential power uses much less fuel.
I also note the article does NOT say 7780 HP, it says 108,920 horsepower at 102 rpm and more importantly, 5,608,312 lb/ft at 102rpm. I knew that 7780 HP was wrong because you can tweak the fire out of a 6 litre chevy diesel and get 1000 HP and 1500 to 2000 lb/ft torque.
Most diesels have a 3/2 to 2/1 ratio of torque over HP, but then most peak in the 2400-3800RPM area, not 102. That is an absurd amount of torque, which is what is needed to twist a prop, after all. At 1,556,002 cubic inches, this is 3.6 lb/ft of torque for every cubic inch, which is similar to the above example of a 6.0L engine (364 cu. in.) getting 1310.4 lb/ft. (stock would be closer to 650-850 lb/ft).
In otherwords, a pretty efficient engine.
Tequila: It's not just for breakfast anymore!
Now look at Diesels. The smallest working Diesels are the little glow plug engines that are used to power model aircraft - actually semi-Diesels whose spiritual big daddy is the classical single cylinder 9 litre like the Bolinder. The biggest are these marine monsters with their two-metre throws. But they all are constrained by a few parameters that are broadly the same - the MEP and the mean piston speed.
At the normal running speed of about 100rpm the engine in the article is doing about 6-7 metres per second. At its normal cruising rpm of about 2000, my car engine is doing 33 revs per second * 2 * 90mm stroke - or 6 metres/sec. I haven't checked, but I fully expect that the working MEPs are within the same ballpark. It's nice to see that engines ranging from grammes to kilotonnes are constrained by a simple law based in metallurgy and tribology.
The other nice thing is, that with the exception of the tiny toy engines, all Diesels work more or less the same way, and the direction of change is by downwards replacement - technologies developed for large marine engines find their way ultimately into small engines. Modern auto engines with their electronic solenoid operated injection systems are basically a shrink of the marine technology of the 80s and 90s. Turbochargers also undergo shrinkage as their technology moves from marine to auto use, so we get the variable vane turbocharger turning up on entry level cars.
It would be wrong to force too many analogies, but there are resemblances between Diesel systems development and computer development that are perhaps more than skin deep.
Pining for the fjords