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Old 11-28-2010, 08:13 AM   #21 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
I have a couple of questions about piston ICE's:

How much pressure could be developed in the combustion chamber *just* from fuel burning? If there was no compression of the intake air (with only a turbocharger in place) would the resulting pressure from the burning fuel be enough to get decent torque?
That's a kinda tricky question to attempt to answer, since the fuel needs to be mixed with the air to ignite--especially with a compression ignition (diesel) engine.

However, the atkinson cycle engines do attempt to address this with overlapping of valve openings. IE some of the intake charge comes from spent exhaust gases.

Quote:
Particularly, if you did not have to "do the work" of compressing the air with the piston -- which uses the momentum of the flywheel, then would the net pressure gain be the same?

Do diesels get all their additional efficiency from the higher compression? Or, are other factors contributing?
Diesel efficiency compared to Otto cycle efficiency (gas engine) is due to higher compression ratio mainly, but also the ability to use extremely lean air:fuel ratios. IIRC, when given full power, the air:fuel ratio is still leaner than 18:1. At idle, it can drop even more to the neighborhood of 50:1.

There is also no throttle plate, which reduces the pumping losses drastically, and makes better use of a turbo. There is essentially no vacuum in the intake manifold while running.

Something else that comes into play is the use of a higher energy content fuel (diesel) that is sprayed at extremely high pressures, so the fuel is atomized much MUCH better.

More torque at low rpms also allows better highway gearing; I've heard of people putting the bumper of their diesel truck against an immovable object, putting the truck into gear, and slowly letting the clutch out, which instead of stalling the engine causes the drive wheels to break loose and start spinning in place. So for an efficient drivetrain you have lower rpms at cruise.

For the direct injected variety (which is nearly all modern diesels) they also enjoy more power and better efficiency. And the technology for the diesel is improving much quicker than for the gas engines, which have stayed nearly the same for years. The fuel efficiencies for particular models through the years have stayed good or gotten better, while the power available has continued to climb.

Generally speaking, a diesel powered vehicle will get nearly double the economy of a similarily powered gasser even if the same gearing is used.

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I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
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Old 11-28-2010, 03:04 PM   #22 (permalink)
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HP = making TORQUE faster and faster.
TORQUE = making FORCE more efficiently.

...that's why the "TORQUE KINGS" (farm tractors) have low engine RPMS, typically; while the "HP KINGS" Formula One race cars (and fuel dragsters) commonly rev up to 10,000+ RPMS or more to obtain their numbers.
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Old 11-28-2010, 04:25 PM   #23 (permalink)
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Open source engine design -- will it work well?

FYI, Formula 1 V8 have been slowed down to 18,000RPM...

Okay, I have been thinking about an engine design that uses just two stokes with disc valves that would have a power cycle every 180 degrees, that is turbocharged, with no compression stroke -- the main advantage would be the power stroke starts at 45 degrees past top dead center and the cylinder is offset to the side, so the connecting rod is straight at the beginning of the power stroke.

It would have less than a 1/3 of the pumping losses of a 4 stroke, and very low valve train friction losses, and the aforementioned mechanical torque. Here's a drawing of the cycle:



It could have very low RPM's and almost be self-starting.

The disk valve would be in the head just above the piston (I have not drawn it yet, sorry), and the 2 fuel injectors and 2 spark plugs would be in the sides of the top of the cylinder (also not shown).

There could be 2 intake ports (180 degrees apart) and 2 exhaust ports (also 180 degrees apart), and the heat could be transferred from the exhaust to the intake.

Some other possible advantages:

Good swirl when the fuel is injected.
Good flame spread.
Only 225 degrees of "coasting" (instead of 540 in a 4 stroke)

The Revetec engine just about doubles the efficiency by gaining mechanical torque; up to 38.6%. This design also gains by having very low pumping losses, low RPM because of frequent power strokes, very low valvetrain friction -- could it be over 50%?

So -- what do you think? Will it work? Will it be uber-efficient? Will not having a compression stroke doom it? Am I crazy?
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Last edited by NeilBlanchard; 11-28-2010 at 04:35 PM..
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Old 11-28-2010, 07:02 PM   #24 (permalink)
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...since, typically, low-speed torque is the holy grail of fuel economy, I'd assume an opposed, simultaneously-firing, two-stroke, two-cylinder, turbo-charged engine with direct injection would be best for fuel economy.
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Old 11-28-2010, 07:32 PM   #25 (permalink)
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Been thinking about engines for forty years but no one wants to listen.
No valves or valve train.
No connecting rods.
No supercharging or turbocharging necessary with compression ratios as high as 50 to 1.
Variable compression and displacement
No reciprocating parts
Stores energy in it's own mass as a flywheel.
One injector for 3 cylinders, one intake port and exhaust port.
Spark or compression ignition, could even vary between two and 4 cycle operation.

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Old 11-28-2010, 07:41 PM   #26 (permalink)
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Vehicle Technologies Program: Retooling Today's Engines for the Hydrogen Economy

How about 60% efficiency about the same as a fuel cell.

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Old 11-28-2010, 11:34 PM   #27 (permalink)
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Yeah, 60% efficiency would be very good!

The disk valve, by the way, could have a plain bearing set up for both thrust and radial forces.
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Old 11-29-2010, 12:14 AM   #28 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
...since, typically, low-speed torque is the holy grail of fuel economy, I'd assume an opposed, simultaneously-firing, two-stroke, two-cylinder, turbo-charged engine with direct injection would be best for fuel economy.
Unless you are running it like a two stroke with cylinder ports and crankcase pumping, you would need a supercharger (positive displacement). this would not be difficult to do, but the problem would lie in the energy density, or rather the heat that would build up having 2 times as many firings per X rpm. Not saying impossible, that is for sure.
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Old 11-29-2010, 12:46 AM   #29 (permalink)
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Quote:
Originally Posted by Old Mechanic View Post
Been thinking about engines for forty years but no one wants to listen.
I listened It's well past time to stop thinking and start verifying though.

and 60%?!? you know that's too good to be true, like electricity, hydrogen is not a "primary fuel", and the books have been cooked in the 60% example certainly.
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Old 11-29-2010, 07:45 AM   #30 (permalink)
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Quote:
Originally Posted by dcb View Post
I listened It's well past time to stop thinking and start verifying though.

and 60%?!? you know that's too good to be true, like electricity, hydrogen is not a "primary fuel", and the books have been cooked in the 60% example certainly.
LOL I agree it's well past time, could have been done 50 years ago .

What I know is you may have read the information but you, like the opponents of the first flying machines, have adopted the "doubting Thomas" attitude, in that you will believe it when the evidence is overwhelming and you can no longer doubt the evidence.

I would be wary of making statements like "you know that's too good to be true" because when it becomes fact, your attitude will be in the majority of those who promoted failure. It's a safe majority position when it's convenient and when the time comes when the combination of developments show your position to be mistaken this conversation will be long forgotten.

Is it really necessary to have an agenda that includes statements that basically allude to me being a purveyor of things false, when the same time could be better spent trying to understand that it is possible.

But then I guess we should keep spending billions on the dream battery that will replace the iC engine and predicting the valhalla of batteries is just around the next corner in development. Been listening to that for many decades as well.

In any pursuit with the goal of energy independence, the effort should never be confined to a single pathway to success. In the Manhattan project they built two different bombs, and even on the day before the first successful test, there were those who believed we would ignite the atmosphere itself and incinerate the whole planet.

So try to remember this in another decade, when the 60% level is no longer unattainable.

Like the conversation between Abraham and God, are you still going to be saying "I told you so and you are a charlatan" if the efficiency is 47% (already done) or 53%. Maybe 57% or even 59%. Will you still be convinced it is not possible? I guess your safe position will only be shown to be short sighted when it actulaly surpasses 60%, but of course then you could argue the method of testing or the integrity of the testing institution.

And while you are nah nahing into irrelevance, please refrain from trying to tell me how to get the job done, since you are not even trying.

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