triple88a

iTrader: (2)

Nope even though they show the cylinders spin, they don't spin. The cylinders are stationary in a revolver style thing.

IMO the most efficiency will be out of a jet engine style engine. Every change of motion in the piston requires energy which = waste.

Currently jet engines are extremely inefficient however are well under developed.

Full_Tilt_Boogie

iTrader: (1)

Jet engines are underdeveloped? lol what?
I wouldnt say axial turbine engines are inefficient, just not efficient over a wide range of operating speeds, which is a problem for cars.

Cars are lame anyway. I want a rocket.

shooterschmidty

Jet engines are not well under developed. The aircraft industry goes to extraordinary lengths to eke out every last percent of efficiency they can. Look at some of the developments in film cooling, high temperature super alloy use in turbine blades, higher temperature combustion cans (Carnot's theorem states that max thermo efficiency is proportional to your max delta T) ect and you'll get a feeling for how well developed they are. Honestly, we're nearing the point where we'll likely only see relatively small improvements in the thermodynamic efficiency of turbine engines. When you consider that a 747 burns almost 25,000 lbs of fuel an hour the economic incentive for maximizing efficiency is obvious.

*edited to remove redundant picture

good2go

iTrader: (2)

Ok, but this still makes no sense to me regarding the head seal.

SO, let me get this straight: if the cylinders do not spin, then the cylinder 'head' MUST, right? Otherwise, how would each cylinder ever see the intake and exhaust porting, let alone a spark plug?

I just don't see any way around having to seal two surfaces (constituting a cylinder and head) which are moving against one another.

Or am I just having a senior moment?

y8s

iTrader: (8)

I can think of a car where a turbine would be the perfect gas motor.



simply make an electric car with a small turbine (pronounced tuhr BYNE, not turban) that spins up as needed. imagine a little pony keg sized turbine in a tesla. oh baby.

triple88a

iTrader: (2)

Indeed underdeveloped for the reason being is that if you look at the end of WW2 where they first began being used, for quite a while they were just barely made to run. The last 10-15 years is where progress started taking off. Progression marks such as the scramjet are big leaps. The scramjet was mainly a theoretical lab engine until 10 years ago.

Yes i know they were designed before WW2 however being researched on a large scale vs a 1 man show with a tiny budged in his garage are different.

Truth is piston engines have been researched for about twice as much time as jet engines. Give it another 40 years and see where jet engines are at.

triple88a

iTrader: (2)

Not sure how real this is but rather interesting story.

Full_Tilt_Boogie

iTrader: (1)

That is some seriously ancient creepypasta

Joe Perez

iTrader: (8)

Re: turbine engines.


Large, multi-hundred-megawatt stationary turbines of the sort used for grid-scale power generation can reach or even exceed 60% efficiency in the very newest designs, but only when used in combined-cycle operation; one where the exhaust gas of the turbine is then used to boil water to drive a conventional steam turbine external to the primary turbine. (Source)










Incidentally, BMW is experimenting with combined-cycle operation pairing an exhaust-powered steam engine to a conventional piston engine, claiming a 15% overall efficiency enhancement. (Source)








In single-cycle mode, large gas turbines operate at around 35-40% efficiency, about the same as a modern diesel or GDI engine. This is the mode employed when driving an airplane, helicopter, etc. The General Electric 9HA, which bills itself as "The world's largest, most efficient gas turbine" claims 41% net efficiency at the shaft. It also weighs 866,000 lbs. (Source)







So-called "microturbines," those with power outputs comparable to what might be used in a highly efficient hybrid-style automobile, have thermal efficiencies in the neighborhood of around 25%, far lower than that of a conventional fuel-injected gasoline engine. (Source) Also, note that the turbine cited here, with a net output of 28Kw / 37.5 HP, stands 7 feet tall, 2 feet wide, 4 feet deep, and weighs over 1000 lbs. Some of that is obviously packaging which would not be needed in an automotive application.






The newest and most cutting edge designs are the so-called millimeter-scale "engine on chip" turbines, presently under development at places like MIT, which eventually promise to deliver hydrogen-fueled turbines to drive our laptops, cell-phones, etc. These devices are among the least efficient engines ever created by man, peaking at around 5-10% efficiency. (Source)









Also, triple88a, seriously? Comparing a RAMJET / SCRAMJET engine to a commercial turbofan engine in the context of a thread discussing engine efficiency is like comparing an NHRA top fuel dragster to a Toyota Camry.









Besides, everyone knows that wood gas is where it's at.

Joe Perez

iTrader: (8)

On the subject of turbines...

The A-10 Thunderbolt II, also known as the Warthog, uses turbine engines.



Money shot:



I mean, just look at that ******* thing. You half-expect it to be piloted by this guy:



In addition to looking like death incarnate, it also contains the largest cannon to which an airplane had ever been attached; the 30mm GAU-8 Avenger.

It's one thing to merely say "this is a big ******* gun," but it's another entirely to have a sense of scale. So here is the gun sitting next to a VW Beetle:



It should be noted that this is not an anachronistic comparison. The VW Beetle was still in current production and being sold in the US in 1972 when the A10 first flew, and in 1977 when it entered active service with the USAF. (The Beetle was last sold in the US in 1979.)

This also gives you a sense of perspective on the normal service life of airplanes. Not enough of one, however.

For that, you need to consider the B-52.



No, not that one. This one:



The B52 first entered service in 1955, the same year that Marty McFly went Back to the Future. And production ceased in 1963, meaning that the very youngest of the B52s presently in service are 51 years old. And get this- ACC (née SAC) expects them to continue operating into the 2040s, a 90 year lifespan! There will come a time when not a single active-duty member of the United States Air Force was even alive when the B52s under their command were built.

Or, put another way, imagine if this airplane were still in active military service today, facing off against SAMs, phased-array radar and supersonic interceptors like the F-22 Raptor:



That's kind of cool, actually.

Braineack

iTrader: (62)

sixshooter

iTrader: (12)

good2go

iTrader: (2)

Negatory! That distinction may be held by the Lockheed AC-130U gunship (or similar variants) which is equipped with no less than a 105mm howitzer AND a 40mm Bofors cannon:

miata2fast

iTrader: (2)

Lets make that bigger.

Tw34k

good2go

iTrader: (2)

Hey, that's no joke. I actually had a fuel tank in a 1995 BMW 750 implode and leak gas all over my driveway due to a charcoal canister vent line that was clogged by spider webs. BMW even knew about the issue; had a TSB out for it and all, but refused to issue a actual recall. Their great flagship V-12 model, crippled by a ******* spider! Just one of many of my pet peeves about BMW.

SI.New.Evaporative.%28charcoal%29.Canister.Purge.Line.pdf

rmcelwee

iTrader: (1)

My best friend in high school joined the airforce and was shot down in his A-10. He lived (but his wingman was killed) and was a POW for about 3 weeks or so. Even though he has a bunch of really interesting and scary stories about it, Rob tells a little about it here (starting around 20:55). I talked to him a few weeks ago about them getting rid of the A-10s but he didn't have too much to say about it.

Joe Perez

iTrader: (8)

Fair enough. I wasn't thinking about crew-served weapons, but it's a valid point. I mean, we are talking about a gun that's more commonly understood as naval artillery.






My specific phrasing of "the largest cannon to which an airplane had ever been attached" was not incautious. It was meant as a reference to the following poorly-written but humorous observation which everyone except for you has already seen.






Of course, crew-served weapons are inherently safer than light arms in the hands of children. They also build teamwork skills.







Which brings us to the Count-a-Shot MOD.1, a device being marketed by Leitner-Wise to the US Arms for the purpose of keeping a realtime count of rounds fired and providing a visual representation of same.







So that's cool.

TrickerZ

iTrader: (6)

I always wondered why no one did this. So much loss is due to heat and just taking that heat and using steam pressure would be an incredible increase in efficiency. You could use the engine heat as well as the exhaust, but you'd probably need to run the engine hotter for that to work. Not sure what other issues you'd run into in that case.

mx5autoxer

iTrader: (1)

Star being pulled near a black hole.

Edit: Apparently it is a computer sim and is the equivalent of a 139 day time lapse.