Hi Efficiency Engine Design

2/21/2002 | John Jamieson

[John Jamieson]

Hi Efficiency Engine Design
John Jamieson MIT67

I’ve been studying the reasons that modern internal combustion engines operate at 25 to 30% efficiency for the last year or so. There are basically three main areas that seem repairable but would lead to large efficiency increases.

1. Current engines are symmetrical stroke. They have the same compression ratio as exhaust ratio. About 10 to 1 is the limit for compression ratio with modern gasolines, but the ideal expansion ratio is more like 25 to 1. Atkinson realized this problem in 1896 and patented and built many engines to prove the concept. He was run over by lighter, smaller, cheaper Otto cycle engines. (Current “Atkinson cycle” engines are really “Miller cycle” engines, without asymmetrical strokes).

2. Current engines cannot adapt to variable displacement to adjust output. High output can very efficient but low output requires throttling of the air, reducing compression ratio and efficiency. (Most cars only require 10 to 20 horsepower to cruise at 60 mph).

3. Current engines generate about half their internal friction due to piston side loads. Several patents claim to correct this but most are statically indeterminate, which means they don’t work.

Come up with a new engine design that fixes these three problems and you’ll improve IC engine efficiency by 50 to 100%.

Please don’t tell me about any existing technology, I’m familiar with the vast majority of existing designs, having studied over a thousand patents. Most don’t close to solving these three problems in any practical way. Original ideas only please. Yes, I do have a design that solves two of the three problems, that I’d be glad to share with anyone interested. (Graphical simulation in VB available).

[John Jamieson]

Will happen soon. 42 volt power system first.

[mamelukesabre]

Now you have really thrown out a challenge to "Detroit". I always thought of it as the 2, 4, 6, 8 but that is probably extreme.

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Alright guys, I can't restrain myself anymore. READ the news once in a while, will ya! Cadillac IS reviving that old variable cylinder engine. They are working on it right now, maybe even have it finished. It is going to be a V8-6, I think. Only 2 combinations this time.

[John Jamieson]

Carnot efficiency goes up with extended power stroke ratio. (i've been calling it exhaust stroke) that's the point. we're looking for 50% not 100%.

[Dinsdale]

You would still need rings (assuming you want compression).

Engines today ride on the rings, the piston should not touch the walls (or you got problems).

The rings are spring loaded outward which is why you need a ring compressor to assemble.

The best a maglev piston could do is decrease the variability of the forces on the rings, perhaps allowing you to use rings with a lower spring constant.

Selinoid valves are thought to be the next big thing in F1, currently they use computer controlled phneumatically actuated valves. My bet is when the next breakthrough comes it will be from racing. Racing saves fuel.

[FreePaul]

Those two urban legends are sooo old,

All of this will be wasted effort when teleportation is in full effect. But, I'm afraid the same fate will befall the first successful teleportation system (if it hasn't already been perfected, bought up and hidden).

[Magician]

I thought of the same thing, but each part of the dual motor (turbine+generator) still has to be as heavy as necessary to make its power. In the last analysis, you could put the turbine and generator on opposite ends of a shaft and it would be little different.

Major problems with gas turbines are that they are fuel hogs innately, and very expensive to manufacture if they are to operate at temperatures where they are reasonably efficient.

I think that for reasons of practicality, reliability and cost, any ultraconomical car in the immediate future will get its economy via modest size, light weight, excellent aerodynamics, and a very small engine that provides marginal performance by today's standards.

[mamelukesabre]

Carnot efficiency goes up with extended power stroke ratio. (i've been calling it exhaust stroke) that's the point. we're looking for 50% not 100%.

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Let me see if I grasp the concept here. If you design an engine with a LONG stroke to run at SLOWER speed, you accomplish the same thing, correct? Isn't that why GM can get their new chevy impala to run at the same fuel efficiency as the honda accord? Even though the impala has nearly twice the engine displacement and approx 30% more horspower and the vehicle weighs at least 500 pounds more? Let those foreigners keep their little multi-cammed "motorcycle" engines. You guys ever checke the MPG ratings on one of those new bikes they call rice-rockets? It's really pathetic.

It seems to me that the guy that suggested keeping the valves open for a little while while the compression stroke started has the right idea. Just combine that concept with what Chevy is already doing and you got a real idea. Or is that what they are already doing with the miller cycle?

[mamelukesabre]

Engines today ride on the rings, the piston should not touch the walls (or you got problems).

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What exactly do you think a piston skirt is for??

[mamelukesabre]

Plug the turbochargers into the exhaust too far "downstream" and you get monstrous turbo lag. Also, not much heat energy is not actually *produced* by the catalytic converters - they sort of bottle-up exhaust heat (some of which is required for the catalyst to function).

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Turbo lag is a concern only for VARIABLE SPEED MOTORS. Cars arn't the only things that have engines.

[John Jamieson]

The piston does ride on the wall. On a film of oil. Rings cannot hold them off.

[mamelukesabre]

No, it isn't silly, perhaps you just didn't understand it. You can make a piston float just like the Japanese can make a mag-lev train float above its "tracks", except that in the case of an engine, the "float" would be between the walls of the cylinder and the head of the piston. Using permanent magnets in that manner would reduce the friction of every stroke.

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I understand that you don't realize these forces are cycling at a very rapid rate. They are going from zero to maximum several thousand times per minute.

[John Jamieson]

Thanks god for 6 speed gear boxes (Corvette). The only hope for big engines is to gear them way down at cruise. My Northstar Caddy gets 27 on the road and goes like skat.

[John Jamieson]

Electronics work real fast.

[Dinsdale]

What exactly do you think a piston skirt is for??

Engines move, sometimes they take a shock. The skirt keeps the piston aligned in these cases. If the piston was significantly wider then it was long, the edges could gouge when incidental contact was made at the bottom of the piston. My point is that the friction is caused by the rings. I've never seen a piston with significant 'normal' wear on the skirt bottom, broken skirts yes.

Why do some racing pistons have such short skirts?

[John Jamieson]

Electronic valves will also allow a asymmetric stroke engine to skip a stroke and go from short intake long power stroke to long intake and short power stroke for accelation bursts. then back to high eff cruise.

[Snow Bunny]

Hi and thank you Uncle George.

[John Jamieson]

Short rods and lenthened strokes. Smoky used to complain to GM about short rods.

[mamelukesabre]

Why do some racing pistons have such short skirts?

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Racing motors are not concerned with longevity. They reduce the weight of the piston to increase RPM's

[Billy_bob_bob]

Give that man a cigar!

[boris]

"Selinoid valves"

Solenoid.