Is air motoring a valid process to develop engines on? 2

[jamesxi]

I'm sure a few of you have heard of the MYT Engine, which claims to have a design prototype that better than doubles fuel efficiency over conventional engine designs.

However, I'd like to know the validity of their methodology in arriving at their estimate. They use a process they call "air motoring" by which they develop the engine by testing it using compressed air @150psi instead of a fuel-air mix, and then seem to assume that when switching to a fuel-air mix that they can simply expect a fairly predictable and mostly linear increase in power output by assigning a psi rating to a certain volume of fuel in a fuel-air mix. They have decided to assign a 20:1 compression ratio mix at 1,500psi. Is that actually a valid estimate? Is the entire concept of doing this kind of estimation valid?

See details of their methodology at:

http://www.angellabsllc.com/docs/TheSignificanceOfAirMotoring.doc

Also, if they have only tested using 150psi, I would think that the results of bumping up to 1,500psi may cause quite unexpected and very damaging results given their prototype has never been stress tested like that. Do they have to test the engine using up to 3,000psi to know their design will hold up?

And lastly, the reasoning they use behind this method is that it allows them to more quickly develop the engine because failures @150psi are a lot less catastrophic. However, couldn't they simply have used an ultra-lean fuel mix to accomplish the same goal? Or maybe ignition would not be possible with a mix that would be lean enough for such low psi.

My personal guess is that you can't just say "yes that is equivalent to 1500psi of air". However the company could actually develop a test chamber to measure what the psi curve would be at various RPMs/compresion ratios/fuel-air ratios, and then you could say, yes since under air motoring the engine has x power then when switch to fuel-air the engine will have approximately y power so long as it does not break under the increased load. However, my opinion really is not very valuable, which is why I'm posting this in hopes others will be able to answer this question better.

 

[patprimmer]

It could be valid to a point, but falls far short of all testing required.

Regards
Pat
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[SomptingGuy]

I had a look at the link and stopped reading when I got to this bit and the mention of using ceramic coatings (i.e. adiabatic).

The calculation is as follows,
Ambient Air pressure: 14.7 psi
20:1 compression results in: 294 psi

Someone needs some basic thermo lessons.

- Steve

 

[BrianPetersen]

That MYT engine has been around so long, and has had dribs and drabs of PR issued over such a long period, that I put ZERO credibility into their claims.

"Air motoring" the way THEY seem to be using it, is of little real-world use and does not account for the real-world heat transfer, combustion time, etc., and operating at 1/10 of normal design pressure will in no way expose the true mechanical limits of the mechanism when the real world intrudes on their fantasy.

I see no reason why the MYT engine would be *any* more efficient than a normal production engine, and a whole lot of reasons why it would be LESS efficient (and less durable). It is, at its heart, still an Otto-cycle engine, and will have all the efficiency limitations of a normal Otto-cycle engine, plus a whole bunch of new ones.

 

[Lou Scannon]

 

[jamesxi]

Brian, since the engine has a very large displacement to work with over conventional motors, can't they use that displacement to ensure a more complete burn? The concept behind the MYT engine seems to be that a large displacement and compression ratio can be used for high efficiency. Seems like a reasonable assumption to me at least, even if the math is not exact.

 

[BrianPetersen]

A Chevy 454 also has large displacement. A Chevy 454 doesn't get fantastic gas mileage when used in a normal car.

The MYT engine supposedly acts like a normal engine with a lot more cylinders. A Mercedes V12 doesn't get fantastic gas mileage when used in a normal car.

If you want better efficiency out of an Otto cycle, you use the fewest cylinders and smallest displacement that you can get away with so that the engine can run at a high load rating (where its BSFC is normally best due to relatively lower pumping losses and relatively lower heat losses). The MYT concept ain't heading in that direction.

 

[patprimmer]

And the larger displacement has more torque so the entire drive train needs to be bulkier and heavier creating more drive line drag and if used in a vehicle, increasing vehicle size and weight and consequential loss in economy.

Regards
Pat
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[Nothegger]

I also wish they had done more testing and corroborated some of this claims with facts and test results.

I don't want to speculate how reliable this mechanism is, but regarding efficiency, I've read they do make some claims about improvements, but that's not what this engine is about. As far as i understand, it's not about mass producing cars with 1000's of hp or ft-lbs, but instead about producing vehicles with standard power levels and significantly reduced engine weight and size (and possibly the same with transmission if their claims about low end torque are correct). That's where the most of economy improvement should come from.

As for the large displacement and lots of cylinders, don't forget that is stated just for comparison, and the engine doesn't have 850 cid and certainly doesn't have 32 cylinders. The idea is to have an engine with small displacement (the actual displacement of prototype is 106 cid) and few cylinders (the prototype has only one!) and have performance of a much larger conventional engine(obviously it's not a cylinder, it's a torus, but you get the picture).

 

[dicer]

The MYT engine, looks like an ineffcient, high wear, difficult to seal combustion gas, affair.