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Dr. Paul Engine?
5

Dr. Paul Engine?

Dr. Paul Engine?

(OP)
What's the concensus on the 'Dr. Paul' Opposed Piston engine talked about in this Youtube video:

part1: http://il.youtube.com/watch?v=Fz8Z9geyOkk&feature=related
part2: http://il.youtube.com/watch?v=K6ahbdkJTN8&feature=related
part3: http://il.youtube.com/watch?v=hTnxsqX9FhE&feature=related
part4: http://il.youtube.com/watch?v=ihR1fCeEobQ&feature=related
part5: http://il.youtube.com/watch?v=y6OuUN2LlV8&feature=related

It was briefly referenced in this thread by someone who seemed to have been involved with the DARPA work on it:
http://www.eng-tips.com/viewthread.cfm?qid=237389&page=8

It sounds too good to be true of course, but it also sounds like too much development went into it for it to be worthless.

What's the deal?

RE: Dr. Paul Engine?

What's that?  Five videos of a guy talking?
I clicked on some of the other stuff provided by U-Tube; much more interesting.

The deal with opposed piston engines is that some of them can be made to actually run, but that's not enough.  Some of them have actually made it into production, because of some particular virtue that made them well adapted for a specific mission, where their faults could be tolerated.

Most of them suffer from one big flaw; mechanical complexity greater than current production engines.  In turn, that means additional manufacturing cost and/or higher service cost and/or more difficult packaging constraints.

In today's world, with many operations capable of EOQ of one, and computer aided design and simulation, odd engines stand a better chance than ever before of actually being constructed, and tested.  They don't stand a better chance of reaching mass production, because of new constraints and better analysis tools.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Dr. Paul Engine?

(OP)
Some juicy claims about prototypes of the particular opposed piston engine described in the video:
1. 80% efficiency
2. full fuel burn - no detectible pollution is emitted
3. can output ~900hp/liter due the design's extreme tolerance for boost
4. eliminates the piston scuffing issue
etc.

It does drive four crankshafts, which I'm sure complicates things, but it sounds pretty interesting.  What am I missing?

This blog lists a bunch of details from the video:
http://dreamer3000.wordpress.com/80-thermally-efficient-opposed-pistons-engine/

RE: Dr. Paul Engine?

It must be the electric turbocharger that makes the difference.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Dr. Paul Engine?

(OP)
Yes, the blog post is egregious, but it has some value as a thumbnail reference for those who want to witness the shocking  claims without watching the 35 minute video.

It's all about the electric turbochargers lol:
This design supposedly allows 147psi of boost and 30:1 compression because it eliminates the head and gives the combustion chamber two movable surfaces to absorb the shock.

Even if it were REALLY expensive to make, I think it'd find a green market somewhere since people could brag that it emits no greenhouse gas or pollution and can be up to 80% efficient using normal diesel, blah blah blah.

Assuming that it could be made to work, can anyone guess what it would be like based on previous opposed piston designs?
Would it have a usable rev or boost range or would it just have to hit a sweet spot and sit there?

Can anyone say it's impossible?  If so, why?

RE: Dr. Paul Engine?

The claims are suspicious.
{
1. 80% efficiency
2. full fuel burn - no detectible pollution is emitted
3. can output ~900hp/liter due the design's extreme tolerance for boost
4. eliminates the piston scuffing issue
}
1. Maybe you can 'measure' high efficiency with an electric turbo, by not counting the electricity into the motor.  That's probably the only way to get 'measured' efficiency this high.
2. If you're detecting no pollution from a combustion process, you have a broken detector.
3.  Extreme tolerance for boost?  I don't get it.  You mean because two cranks support each piston?
4.  I don't get this either.  Two cranks and two rods per piston might in theory get rid of side loads.  Which is a good thing, because there's no place to put a skirt on the piston.  You've also got the piston trying to separate the cranks by wedging the rods in there, with everything at a bad angle.  I see it as heavy, or fragile, or both.

With 30:1 compression plus 147 psi of boost, is there ROOM for enough fuel to combust all the air?


 

Mike Halloran
Pembroke Pines, FL, USA

RE: Dr. Paul Engine?

So what? More bearing area more losses. Not much new there.
It runs on air real good, lots of talk that is all.

RE: Dr. Paul Engine?

(OP)
Thanks Mike.
For the sake of dialogue, I'm going to play devil's advocate with what was said in the video:

1. The whole system was 80% efficient including the electric supercharger (I imagine there was a sweet spot involved).
2. They were equipped with state of the art detectors circa 1988+. The cleanliness was the result of very late fuel injection and the  extremely high pressures. To illustrate the pressure: the exhaust would be very cool because of liquid nitrogen that would instantiate in the chamber.
3. The fixed head/headgasket is usually a limiting structural element for boost. Here, the head is gone and the combustion chamber is a cylinder with movable ends which can withstand, and harness, outlandish compression + boost extremes.
4. With one conrod per piston they'd get ovoid issues but with two they balanced it out so the piston stayed centered under stress.

Dicer, again, playing devil's advocate - if it can run 80% efficient and shoot butterflies out the tailpipe then bearing losses and supercharger complexity are less of a big deal.

RE: Dr. Paul Engine?

Snake oil.

RE: Dr. Paul Engine?

(OP)
TDImeister,
What is it that makes this design foolish and the Hofbauer/Ecomotors OPOC design worthwhile?

In the Ecomotor design I see that the crank situation is taken care of; and balance doesn't seem to be an issue.  What else makes the Dr. Paul concept a dead end?

RE: Dr. Paul Engine?

Ummm, the 80% efficiency claim doesn't ring any alarm bells???

RE: Dr. Paul Engine?

Nobody _here_ said the OPOC was worth a crap, either.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: Dr. Paul Engine?

Indeed.

RE: Dr. Paul Engine?

(OP)
Lots of things about it ring alarm bells so I'm seeking expert insights.  I understand that the claims are so absurd as to be dismissed without blinking BUT the presentation seems straightforward, transparent and not at all smooth or salesy.  And I've never heard of that kind of compression/boost situation; or liquid-nitrogen-forming chamber pressure; so I'm curious how to determine whether it's pure fancy or uncharted territory.

Extravagant claims aside, what about the 'Dr. Paul' concept it makes it absurd?

RE: Dr. Paul Engine?

OK.  I endured through some of the video, too, and they are just as bad.  Egregious, as was said.  That alone should give one reason not to believe.

As one simple example...He says a compression ratio of 20:1 increases pressure from 14.7 psi to 294 psi.  That's wrong.  The compression ratio is a volume ratio...not a pressure ratio.  (Yes, high rc improves therm efficiency, but he got that basic fact wrong.  That speaks volumes.)  Or another example.  He states that the reason engines are so inefficient is because the fuel isn't burned and just goes out the exhaust.  At stoich, the combustion efficiency of an SI engine is very high...well in the high 90% range...so not a lot of unburned fuel going out the tailpipe.  For DI engines which burn lean, it is nearly 100%.  The reason for "low" fuel-conversion efficiency is due to lower thermal-conversion efficiency, which has nothing to do with how much of the fuel is burned. It's more how the energy in the fuel is utilized.  Things like heat loss through the chamber walls, or heat loss out the exhaust from limited expansion, etc.  Then as someone else mentioned, there will be emissions.  At stoich, there is H2O, CO2, and N2 (complete combustion, low temps).  With dissociation at high temps, all kinds of stuff.  So no...no butterflies coming out of there.

The videos reminded me of that famous statement by Wolfgang Pauli, "This isn't right. This isn't even wrong."

As to the geometry, as Wai Cheng (MIT) summarized it during one class, there are very good reasons why the basic construction of current-day engines is the way it is.

Well...good luck to them.

RE: Dr. Paul Engine?

I agree with black2003cobra. I didn't see any video's of an operating engine...are there any? Also still sounds like a bunch of parasitic loss there. How do they get 80% efficiency with rotational and frictional losses, unless I'm just not seeing it.  

RE: Dr. Paul Engine?

Mcspeed continues to ask why the "Dr. Paul" engine is impossible - the answer is that it probably is possible - just highly impractical and the claims are exaggerated.
 There is nothing magical about the "Dr. Paul" engine layout that would make it more able to withstand the internal pressures. Tractor pull diesels reportedly operate at 300psi boost (although not with 30:1 CR). A diesel's boost and CR are limited only by the mechanical strength of the engine.
 A "Dr. Paul" (or conventional) engine of 30:1 CR and 147psi boost could be built (and in fact probably has been built in conventional form) but would have to be enormously strong and heavy to stay in one piece for more than a few seconds.  By my calculation 30:1CR/147psi boost equates to about 17000psi (probably less than this depending on cam timing but maybe still 10000psi or so) after compression and would be several times this after combustion.
The 80% claim probably comes from the fact that a 30:1 expansion ratio would give about this theoretical thermal efficiency - but nowhere near this much in real life.
A more practical engine would be a conventional diesel with a 30:1 CR and Atkinson Cycle to limit the compression pressure - research engines like this have been built and tested.       
  "Dr. Paul" engine - possible but unlikely.

RE: Dr. Paul Engine?

(OP)
Thanks for the feedback guys.  I learned a lot.

For clarification, the Part 4 @ 3:50 talks about using some kind of liquid nitrogen setup to cool the exhaust which happened to reduce pollutants - I guess by avoiding the disassociation temps blackcobra2003 mentioned.  I'd previously thought he said the liquid nitrogen was forming in the combustion chamber and being somehow utilized from there.

RE: Dr. Paul Engine?

mcspeed,

I worked with Marius Paul on the TRC opposed piston diesel project almost 20 years ago.  I did some redesign on the reciprocator test rig hardware (pistons, liner, rings, etc.).  The TRC concept was never run as a complete system, with the opposed piston reciprocator, rotary expander/compressor and turbocharger.

We did some dyno work with just the 2 stroke uniflow reciprocator and fuel system, with the scavenge work done by an electric screw compressor.  The engine was run at some very high cycle pressures and BMEP rates.  We never got good reliability from the engine, but while it was running it seemed to be getting some excellent SFC/thermal efficiency numbers, even after adjusting for pumping losses.  Nowhere near 80% though, it was closer to 52%.

Regards,
Terry

RE: Dr. Paul Engine?

(OP)
Wow thanks for the firsthand info tbuelna!
Do you think the design is any more promising 20 years later?  Or is it just a novel approach that has run its course?

RE: Dr. Paul Engine?

mcspeed,

I took a quick look at the first video.  It looks like the same engine from 15 or 20 years ago, except that there are now a pair of rotary valves.  

The engine had lots of basic issues regarding combustion efficiency, heat transfer and tribology.  It doesn't appear that those issues have been addressed, so I'd say the engine does not appear to be any more promising now than it was back then.

Regards,
Terry

RE: Dr. Paul Engine?

(OP)
Much appreciated!  Have a great weekend

RE: Dr. Paul Engine?

Professor Fred Major!
If you developed something that was any good, the last thing you would do is get this turkey to publicise it on YouTube. Those videos contain about 5 fallacies or engineering inaccuracies per minute - eg. "Muscle car engines of the 60's were more efficient than today's engines. The reason today's car achieves good fuel economy is weight reduction"  BALDERDASH! It is the exact opposite. Current engines are the most efficient ever and cars today are much heavier. I don't know what he is supposedly a Professor of, but it sure isn't engineering.

RE: Dr. Paul Engine?

I commented on the blog, lets see what happens.

RE: Dr. Paul Engine?

Grunt - I agree with your comments on engine efficiency - but are today's cars heavier?  I thought that with thinner higher-tensile steel in the bodies and plastic bumpers etc. that they were lighter on average than the older cars.  

RE: Dr. Paul Engine?

The bodies are thinner and lighter, but there's a lot of additional crap to be carried within them, like airbags, evaporative emission systems, fuel return lines, ABS plumbing, lots more wires, etc.  Additionally, frames (or structural body parts) with crumple zones must be heavier than simpler straight-ish frames.

I suggest that weight reductions implemented at considerable effort and investment in pursuit of better fuel economy have been mostly offset by mandatory safety equipment, and additional doodads installed by default as market pressures and/or manipulation by marketing operations has pushed up the amount of stuff installed on a 'base' car.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Dr. Paul Engine?

It might vary from region to region, but cars here are heavier. While they use lighter materials, the increased power, requires beefier axles, drive shafts, transmissions and brakes.

Wheels tyres and suspension are heavier, air conditioning and power steering are std on base models, air bags and ABS are also very common now and crash performance requirements are ever increasing as is torsional rigidity and control over suspension and chassis compliance on bumps and curves

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Dr. Paul Engine?

A 1970's Honda Civic was a 1600 lb car. A new one is 2700 lbs.

A 1970's VW Golf was an 1800 lb car. A new one is 3000 lbs.

Both of those have grown substantially in size ... the current Civic is bigger than the 2nd-generation Accord, nevermind the 1st-generation. A Honda Fit is bigger than the 2nd-generation Civic, and it weighs more.

A Chevrolet Aveo is a 2500 lb car.

RE: Dr. Paul Engine?

I drive Alfa Romeo, in Europe. The average alfa 33, considered a small midsized car here, weighed less than 900 kilo when first on the market. It could be bought with a 1.5 liter engine with over 100 bhp. Fuel economy was about 1 liter in 12 km. The replacement I own is a 145, 2 liter, 1250 kilo car. It does about 1 liter in 11 km, has 155 bhp and is just as fast to drive on the road. It does have way more crumple zones, safety beams, air conditioning sound padding and is emitting substantially less CO, NOx and HC than the 33. Fuel efficiency is up, the engine is cleaner, but most of it is offset by the extra safety and luxury indeed.

In Europe, where the focus already was on small, efficient cars, this is the trend. I think that in the USA, where technology wasn't pushing towards smaller, more efficient cars, people were buying trucks with large, gas guzzling engines. Only recently, when economics started demanding people to size down, the market has been going towards smaller cars. This may be the explanation that sales and car population have shown a different trend than engineering trends world wide have been.

RE: Dr. Paul Engine?

How much bigger and heavier are the tires wheels and brakes on your new Alfa?

How many more gears does it have?

How much quieter is it?

How much stiffer is the body?

I bet the old Alfa didn't have as many electric motors to do all those tiresome jobs like moving the seat and the windows and the mirrors.

Even silly things like the number of speakers affect the weight - you have to reinforce the panels to make up for the holes the speakers go in.

The reason cars get bigger and heavier with time are based on trying to sell the same vehicle to the old customer (who is generally somewhat more affluent one model later) as well as the new customers for that model.

 

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies  http://eng-tips.com/market.cfm?

RE: Dr. Paul Engine?

Tires,wheels and brakes are bigger, mostly because the car is heavier. I compared the two top spec models to keep it fair and yes, the trend is that wheels are bigger and heavier. In fact, apart from this top model, the cars both have 254 disc brakes in front and drums in the back. The difference is that the newer model has ventilated brakes. As I said, it's much stiffer, mostly because of the safety regulations. There are exactly 2 more electric motors in the new one, for the wing mirrors. The rest is also present in the old one.

The car I picked to compare is maybe not totally representative of the european market, since Alfa already was putting quite a bit of features in their cars and kept it to "essential luxury" so the car would remain sporty. Power to weight ratio and suspension/brake features is rather good for a small midsized car and always has been with them. I picked it because it's the brand I've been driving for the last 11 years and I've been working on a lot of these cars, so I know the technology and features best.

If you look at for instance the VW golf, now in their sixth generation, the creeping featurism is much more defined. The first golf in the seventies curb weight started at 790 kilo's, the GTI at 836 kg being slightly heavier because of the bigger engine and brakes. The second generation already was at 120 kg more. The 3rd golf GTI was much slower than the first generation golf GTI and weighed 1088 kg.

These figures are quite a good representation of the trends in European cars. They got heavier, more features got added, engines gained power and efficiency, but in the end, the cars weren't going faster and fuel economy wasn't much better either. Only emissions of CO, NOx and HC are down because of the cleaner way the cars now burn fuel. CO2 is still roughly the same in real world use. The "euro test cycle" has been instated and altered a few times, but it's in no way representative for most of the driving done in the real world.

I live in the Netherlands and our government is traditionally taxing both ownership and usage of automobiles quite heavily. Purchasing a new car means that over 50% of what you pay is taxes, unless it's one of the "A label" cars that is environmentally friendly, then it's exempt from some of the taxes. The more a car pollutes (euro cycle used) the more tax you pay at purchase. You also have to pay road tax, based on the curb weight and the type of fuel used. Then there is fuel tax. Current prices for 95 ron, the most common fuel here (93 MON I believe) would be about 8.30 US dollar/gallon (1.54 euro/liter) The taxation on purchasing new vehicles based on pollution is new, it used to be a static percentage of the purchase price.

There's another phenomena here, but that's rather unique for the Netherlands, because of taxation, company lease cars. Quite a few people get a company provided lease car. They get to drive it as a personal car too, add a percentage of the catalog value of the car to their income (for tax) and usually don't have to pay for the first 10.000 km each year or so. For most, this is cheaper than buying a new car themselves so many companies offer this to their employees. They changed the tax rules for these cars as well, the A label cars get taxed 14%, the B labels 20% , and C and higher get 25% of the catalog value after taxes added to your income for tax reasons.

This means that a lot of the new cars sold here are in fact hybrids and "micro cars" as I call them, since they are the modern equivalent of the BMW Isetta in my eyes. We do see a few 3 cylinder turbo diesel cars that are slightly larger appear now, since they are very fuel efficient and the taxation criteria are only based on CO2 emissions per distance traveled.

A lot of governments are now trying to regulate what cars are being bought with tax and emissions regulations. Safety regulations seem to make meeting these emissions regulations hard, because you can't just put people inside a paper bag with wheels attached anymore.  

RE: Dr. Paul Engine?

Yeah, the newer cars are absolutely marvelous, but it does cost weight and money to make it happen.
Air bags and guard beams and crumple zones, oh ####!
Actually, I bet the crumple zones add a lot more weight than the 'strength' / stiffness would otherwise require.

But - when something bad happens, you have a real good chance of surviving it.

My "Corvair" is almost 2500 lb, with its Iron 3.8 and no safety equipment to be seen. (well, it does have seat belts.) It encourages me to drive defensively.

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Dr. Paul Engine?

Food for thought.  A 2006 VW GTI (US spec) weighs within a couple dozen pounds of a 383ci '68 Dodge Charger.

Chargers are not small cars by any stretch of the imagination.
 

RE: Dr. Paul Engine?

izzmus,

Maybe not a "couple dozen pounds", probably more like 200 to 300 lbs.  But it's still an amazing statistic.  

Both are unibodies by the way.

Terry

RE: Dr. Paul Engine?

The specs I found were ~3313 for the VW, ~3360 for the Dodge.

Multiple layers of carpeting and padding, sound deadener inside and out, and the complex wiring harness needed to control all of the modules and power everything do not come light.

People expect to drive cars with the silence and solidity of a tomb, though.  Or, at least, the magazine reviewers expect it.

RE: Dr. Paul Engine?

I looked at the first video and quickly got bored. maybe not snake oil but, boring nonetheless. Clicking on some of the links on the right-hand column, within 3 links I was at the "Searl Engine". Oh man, what utter snake oil bull THAT is! Luckily, within 3 more links I was able to find two cute women having a pillow fight.  

RE: Dr. Paul Engine?

I looked at the first video and quickly got bored. maybe not snake oil but, boring nonetheless.

Have to disagree with you there. It's definitely snake oil!

Engineering is the art of creating things you need, from things you can get.

RE: Dr. Paul Engine?

NAVISTAR just announced an agreement to further develop the OPOC engine.

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