Efficiency Improvements for Internal Combustion Engines

[Frank Lee]

For perspective on piston slap... I recently had the cylinder heads off of a 1995 3.0 Ford with 150,000 miles on it. There were NO ridges at the cylinder tops, and the factory hone x-hatching was clearly visible throughout. Basically, the engine internals looked like new after 15 years and 150,000 miles, but the body is becoming a rotted out P.O.S....

[autoteach]

Originally Posted by NeilBlanchard

Thanks for the response, Frank. The trick seems to be combining as many of these features in one design, I guess?

This thread has flown along, and my design proposal has been buried:

http://ecomodder.com/forum/showthrea...tml#post206606

In a nutshell: a 2-stroke, rotary disk valve, opposed piston, with an offset that aligns the beginning of the power stroke with the crankpin at 45 degrees past top dead center -- oh, and only a turbo doing any compression; as there is no compression stroke...

I do see some slight problems with this design, not in the crank offset (although the amount seems to be excessive and with significant downsides in the exhaust stroke thrust) but in the filling of the cylinder. A typical engine would need about 120psi of compression to meet favorable conditions for gasoline combustion.

Engine Compression Ratio - Tech - Popular Hot Rodding Magazine

Knowing that, at a minimum, you need about 8:1 compression (but this is a problem if any wear occurs as it quickly drops from running to non), you need to provide similar amounts of pressure from the turbo. As a turbo works primarily on the turbine principles, how, at start up, does the turbo manage this? How does the exhaust, from an engine not running, spin the turbine to a speed fast enough to produce 120psi intake charge?

I think my problem may be that I am inside the box, and having some difficulty thinking about how these systems would work other than how they are normally used. Help me out of the box.

[NeilBlanchard]

Two things: the exhaust flow is nearly constant because it is a 2 cylinder opposed 2 stroke, and the turbo could be sized appropriately? The RPM's are low, so there is some time. Also, each piston is pushing the other through exhaust, and there is no throttle, so pumping losses are low.

What is it about compression that is required for favorable combustion? Is it heat only, or is the pressure required? I was hoping to avoid the "work" of compression.

Your point about the offset causing low power on the upstroke is key -- the whole aim of this is gain the downstroke advantage, and not really need the upstroke power. Otherwise, it would seem that a crankshaft design for ICE is inherently and fatally flawed in that it cannot achieve any better efficiency than it already has?

(It was invented for steam power after all, which has a large back pressure reserve, so the piston is pushed nearly constantly through the whole stroke; instead of a burst at the very beginning.)

[cr45]

Neil
Relative to the pistons being at tdc, at what stage in the cycle is the fresh charged introduced?

[dcb]

Originally Posted by NeilBlanchard

...
(It was invented for steam power after all, which has a large back pressure reserve, so the piston is pushed nearly constantly through the whole stroke; instead of a burst at the very beginning.)

This is what makes me critical of "%50 efficiency" claims. That burst charge in the cylinder isn't going anywhere till the exhaust valve opens, even with an ordinary crankshaft. More torque != more power.

[NeilBlanchard]

Hi,

Originally Posted by cr45

Relative to the pistons being at tdc, at what stage in the cycle is the fresh charged introduced?

The intake valve (two openings in the disk valve) would have to be right after TDC, I would imagine? The challenge would be to have the exhaust ports open as close up to TDC as possible. This is obviously very schematic -- a thought experiment to see if such a thing is feasible.

Whether or not it works, all depends on whether the expansion from just burning the fuel is enough to power the engine; balanced against the parasitic losses. Since it is a 2-stroke, there is only one "coasting" stroke; rather than three, and no compression which has to be a big savings. And rotary valves are much lower friction -- just a constant low drag rather than periodic peaks when the cam lobes have to push against the valve springs.

Edit: some further thoughts on the compression stroke. If the compression in and of itself is important, then this design is probably moot; but here is why it seems like it is about the heat generated by the compression and not the compression itself, per se. The compression itself is all done at a loss by using the momentum of the flywheel, and because there is friction loss as well, the compression itself can't be worthwhile -- the net gain must be coming from the fuel burn.

If it is the heat gain during compression that is important -- think about this: there is some much excess heat in ICE's as it is, right? If that "waste" heat could be transferred to the intake air *instead* of having to heat it via compression -- then we gain a whole lot of efficiency, right?

The intake manifold passages could be physically contacting the exhaust manifold, and these could be designed to transfer as much heat as possible. Aluminum with flutes that are parallel to the flow, and if EGR could be used, then that would use the "excess" heat instead of generating even more heat.

If the efficiency is high enough and enough of the heat is actually used by the engine, this would minimize the capacity of the cooling system, too.

Another major advantage of this design it seems to me is that is would require very little flywheel weight, since each 180 degree exhaust stroke is mostly offset by the 135 degree power stroke; leaving only the 45 degree "mini" intake stroke as a loss phase. So, bearings would have less load, as well.

[user removed]

Green Car Congress: Antonov Says New EV Transmission Technology Is Scalable to Wide Range of Passenger and Commercial Vehicles

Kind of contradicts the assumption that you do not need a transmission in an electric vehicle, as well as the generalization that electric motors are 93% efficient.

regards
Mech

[user removed]

Demonstration Vehicles | Clean Automotive Technology | US EPA

The best engine on the planet today is at 55%.

efficiency.http://en.wikipedia.org/wiki/Brake_s...el_consumption

It burns 285 tons of heavy fuel oil a day at 92 RPM.

Look at the VW and Audi engines, in the chart, and you can honestly think they will never reach 50% or possibly 60%.

They could do that by using the same technology that power plants use by converting the wasted heat energy from the prime generator into useful electrical energy.

The philosophy is as old as the triple expansion steam engine.

Use exhaust heat to boil water, or another liquid specially desinged for the purpose, run it through the previously linked u-tube demo pump and stick some magnets on the outside and a coil for an alternator.

Since 62 % of the heat energy is wasted, capture that energy the same way a powerplant does.

regards
Mech

[dcb]

those are extremely large engines, not really applicable to personal transport. Nothing is impossible, but many are impractical. peak bsfc tends to go down with smaller engines, though reducing the power demands is usually more effective, unless you are talking about (serious) mass transportation.

And I agree, an electric motor usually benefits, efficiency wise, from having some gears to choose from, electric motors only attain peak efficiency under certain loads and rpms. The batteries themselves benefit from reduced current demands.

[user removed]

Start with the already existing 44% efficient Audi engine, get another 6% from the 56% wasted heat and you have 50%. Get another 16/56 conversion efficiency from the wasted heat energy and you are at 60%.

Combine that with the 5 year old EPA linked HH and you are over 100 MPG average in a 3800 pound car.

No new tech, no waiting for the miracle battery, just basically off the shelf components.
Don't want to use my design, becasue I have an agenda, I could care less DCB. Do it with some other technology if it exists.

Just do it NOW and bury OPEC, instead of waiting for another miracle just around the corner.

regards
Mech