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).

[boris]

"Do the "Turbo Compound" thing, like on the Lockheed Constellation airplane. Uses a turbine in the exaust to capture wasted energy and directly powers the drive shaft. This uses up the wasted expansion ratio."

In automobiles, this is called a 'supercharger'. You may have heard of it.

--Boris

[Dinsdale]

Short skirts reduce weight but the are usually for clearance on stroker cranks with correspondingly short rods.

Old motors have wear patterns on the cylinder walls that correspond to the range of motion of the rings. That tells me which part is generating the lions share of the friction.

[Dinsdale]

A supercharger blows air using the crank to drive the blower.

A turbocharger blows air using a turbine in the exaust gas to drive the blower.

[realpatriot]

Ultrsonic nebulization of the gasoline?

Conbine with ulrasonic nebulization of water (or EtOH, or other?)

Maybe this will "cover" or "coat" the nebulized H20 (or ? EtOH) with the gasoline increasing the surface area of the gasoline and converting (quickly) the H20 to steam.

I've thought about this for some time and wonder what you think.

[realpatriot]

Damn,we need a spel ckecker on this think!

[John Jamieson]

Turbo compound is not a super charger. The output of the turbos is geared directly to the engine output shaft.

[nightdriver]

"More efficient means more power out of a smaller package."

Actually, just the opposite is the way it works. A highly efficient engine of any process tends to be very large for its power output.

The diesel engine outshines the gasoline (spark-ignited) engine every time in efficiency because of its higher compression ratio. However, it will weigh over twice as much as an equally powered SI engine.

[John Jamieson]

Water injection is often used to lower cylinder head temps but does nothing to the burning of the gas.

[realpatriot]

Okay, how 'bout ultrasonic nebulization of gasoline without the water?

[longshadow]

There was a WWII radial aircraft engine where the cylinders rotated around a fixed shaft.

LeRhone (sp?)

It was WWI.

[Blood of Tyrants]

You are only considering the efficiency of scale and not taking into account new technology. For example, a 1965 VW bug had a 1600cc engine that put out about 40 hp and got about 30-35 mpg. Yet today it is routine to get 130 hp and 35-40 mpg out of an engine of the same size.

[Poohbah]

The guy who came up with the Pogue carburetor (Charles Pogue), the accept-no-substitutes "original" 100 MPG carbuertor, is in a nursing home in Winnipeg, Canada.

So much for your theory.

[nightdriver]

There's certainly something to be said for computerized engine management. There are, unforutnatley, thermodynamic limits - probably the most salient being that a Carnot cycle (which cannot be built) is the upper limit on engine efficiency.

I've always thought that more effort should be put into designing a good stratified charge system. It would allow higher compression ratios by increasing the "apparent" octane rating of this miserable quality gasoline we have to use these days.

[zog]

--judging by my output, I would be forced into accepting the turbocharged dual over head dyslexic version of the spel chekker meself...,

%^(

[John Jamieson]

OK, what's nebulization?????

[mamelukesabre]

Short skirts reduce weight but the are usually for clearance on stroker cranks with correspondingly short rods.

Old motors have wear patterns on the cylinder walls that correspond to the range of motion of the rings. That tells me which part is generating the lions share of the friction.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Old motors also have "out of round" cylinders and piston slap. I'm glad you brought up the wear due to rings. It is the ridge created at the top of the cylinder from this wear that breaks the rings. Not the side load on the piston.

[mamelukesabre]

Actually, just the opposite is the way it works. A highly efficient engine of any process tends to be very large for its power output.

The diesel engine outshines the gasoline (spark-ignited) engine every time in efficiency because of its higher compression ratio. However, it will weigh over twice as much as an equally powered SI engine.

~~~~~~~~~~~~~~~~~

I'm not sure I totally buy your theory about higher compression ratios being the reason for the higher efficiency. I think it has more to do with the fact that diesels engines operate at higher temperatures and that there is a great deal of leftover heat "recycled" to vaporize each subsequent charge of fuel.

[mamelukesabre]

In automobiles, this is called a 'supercharger'. You may have heard of it.

--Boris
~~~~~~~~~~~~~~~~~~

Boris, I'm afraid you're all wet here. A supercharger on a car is just the opposite. The device he was talking about takes energy from gas flow and adds energy to a rotating shaft. The device you are talking about takes energy from a rotating shaft and "charges"(adds energy) a gas flow.

[mamelukesabre]

A supercharger blows air using the crank to drive the blower.

A turbocharger blows air using a turbine in the exaust gas to drive the blower.

~~~~~~~~~~~~~~~~~~~~~~~~~

If you want to get really technical, "turbocharger" is an incorrect term. It is really a turbo-supercharger. That is what they were called when they were invented for use on airplane reciprocating engines. Therefore, a supercharger is a device that "charges" the intake, and a turbo-supercharger is a device that does the same thing, only by use of a turbine.

[John Jamieson]

Carnot cycle math from 100+ years ago shows direct relationship between compression ratio and eff. Also desiel fuel contains more BTUs.