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A.K. Boomer
01-10-2014, 12:07 PM
Due to all the engine talk lately I did want to bring something up in a separate post so not to intrude on Brians engine build O.P.

We are living in a time where new engine idea's are dime a dozen, there is allot of rubbish to sort through - engines with no particular benefits yet a ton of pitfalls, but there's one thing im sure of and that's that Variable Compression Ratio IC engines are not a fad, they will be made very simply and be so practical with the power and efficiency benefits that they will be hard to ignore,,,

Here is a little taste of some of the bennies, http://www.youtube.com/watch?v=DdM2VbbdtB4

I have to add - this is nothing new - VCR's have been around for several decades - people knew even back then all the potential benefits but with all the electronic controls we have now comes unbelievable benefits that could never be realized before - changing ratio's "at the drop of a hat" can reap rewards throughout the range - it can keep volumetric efficiencies high AND power production AND optimized fuel burning AND therefor fuel consumption AND also reduce NOx emissions all at the same time...

To show just how long this idea has been out SJ's post of the Armstrong engine looks like it has little eccentrics on the lower pivoting ends of the rocker links and im thinking that's exactly what they were used for - there's also a plethora of other examples old and new.
http://www.achatespower.com/diesel-engine-blog/wp-content/uploads/2013/02/armstrong_whitworth.jpg


But the point to all of this is the opposed piston engine offers a very simplistic solution beyond the complexities of many of example - and that is simply to split the crank and change the timing of the two crank throws in comparison to each other - furthermore - if there are intake or exhaust ports involved or if the crank halves are individually linked to intake and exhaust valve timing accordingly - the sky is virtually the limit as you can automatically incorporate VVT into the mix without any additional moving components --- the results would be a normally aspirated engine that could pull a stump out of the ground @ 1,500 RPMS and come on like an indy car at 10,000 RPMs +

The problem with allot of these newer engine designs is they simply don't get it - reciprocating pistons do not "waste power" they give back what they take --- and due to bore and stroke can be tuned to suit a variety of things and are easily serviceable, but that being said - just like any other engine they are "locked in" to a predetermined CR, sure you can add things like turbo chargers and such but you cannot "spool up" in an instant - you can go supers chargers but have to pay the fiddler in HP robbing parasitic drag,

With the invent of direct injection gas - turbo chargers make allot more sense - WHY? it's due to not having to run 7 to 1 compression ratio so they can now keep the thermal efficiencies up higher than before, but in comparison to VCR they are still crude cumbersome slow response devices...

Imagine a direct injection gas engine that runs without any spark plugs - and adjusts it's compression ratio within milliseconds to suit whatever needs are thrown at it, all whilst keeping control of the burn rate with pulse controlled injection, the possibilities are endless...

this is where we should be putting all our effort right now - mark my words this is the next biggest breakthrough - the mechanical's are nothing to create - we are already using hydraulic degree changing devises on most cars camshafts right now that are equipped with VVT... piece of cake... just one single beefy one for the two cranks to be linked too... that's your only added extra mechanical complexity...

dp
01-10-2014, 12:53 PM
When Brian started the current build several of the Armstrong style engines popped up including the VCR varieties (including that shown above). There is an article in the peer reviewed literature that discusses modern designs that incorporate OPOC and VCR features and yep - very interesting. The tend to have ported vs valved asperation and are supercharged two-stroke.

Edwin Dirnbeck
01-10-2014, 01:38 PM
" reciprocating pistons do not "waste power" they give back what they take" ?
I can see where a piston can give back SOME. of the enregy that it took to compress the mixture and the valve springs might give back SOME of the energy it took to compress them . There is still a lot of energy consumed in stoping and starting the piston and rods and valves.An example would be spinning a turbine engine in a vacuum chamber and spinning a piston engine in a vacuum .Even if you had loose teflon coated pistons and no friction robbing rings ,the engine would coast to a stop in seconds wilst the turbine would coast for a many minutes.Edwin

A.K. Boomer
01-10-2014, 01:41 PM
DP - we been putting the cart before the horse,
Due to a fixed ratio we start at a deficit and then try to adjust with multitudes of patchwork after the fact - in the form of enriched mixtures and retarded spark and built in compromised valve timing,

We should be introducing the most optimum compression ratio for any given load or RPM range and then running with the finer details afterwards...

the opposed piston engine is one of the most simplex engine forms for a VCR to be incorporated into,,, it is interested, and I usually do not get stoked about engine designs anymore - but Brian's engine and the other examples made me ask "what if" when it comes to VCR's - but so far as iv seen nobody is altering the two crank journals timing,,,
This would give you immense control - and if the segregated units are then individually linked to valve timing, one for intake and the other for exhaust, it could be a VVT "freebee"
I don't believe anyone is thinking along these lines ... the possibilities are endless...

It would have every potential to be the worlds highest HP per cubic inch normally aspirated engine ever in production - it could also prove to be the most efficient , and it could run on everything from gas to diesel to 1/3 bat urine...

A.K. Boomer
01-10-2014, 01:49 PM
" reciprocating pistons do not "waste power" they give back what they take" ?
I can see where a piston can give back SOME. of the enregy that it took to compress the mixture and the valve springs might give back SOME of the energy it took to compress them . There is still a lot of energy consumed in stoping and starting the piston and rods and valves.An example would be spinning a turbine engine in a vacuum chamber and spinning a piston engine in a vacuum .Even if you had loose teflon coated pistons and no friction robbing rings ,the engine would coast to a stop in seconds wilst the turbine would coast for a many minutes.Edwin


All engines have to deal with friction --- the piston engine by design gives back every bit of reciprocating energies it consumes - minus the friction,,, It may take x amount of energies to get the piston moving from TDC to max feet per second close to half way down the bore, but after that every bit of that energy is being returned back to the crank - every single bit minus the bearing friction and such,,,
I hear guys on here talking about the balance of their mills spindle at 6,000 rpms on here like they are going into the unknown,,, that's a totally round concentric part,,, now try upping the ante to 3 times that amount with connecting rods and pistons flailing about, Fact is - is the piston engine is very hard to beat, and it's actually a very good design for what it does...

PStechPaul
01-10-2014, 02:23 PM
I remain skeptical. Some people believe what they are told, but I must be "Schoen". For all the many years of research and promises as presented in the YouTube video, it seems there has yet to be any publicly published hard figures for fuel economy or power/torque/RPM curves. The video seemed to be a cry for investors, and was not very convincing. Show me a car, put ten gallons of gas in it, and let me see it go 450 miles. Mine will, and it's a low end 1999 Saturn.

Here are other references to the technology:
http://en.wikipedia.org/wiki/Variable_compression_ratio
http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/vcr.html
http://www.docstoc.com/docs/160430654/Performance-Analysis-of-Variable-Compression-Ratio-Engine-using-Diesel (0.472 kg/kWh)
http://www.saabnet.com/tsn/press/000318.html
http://topics.sae.org/variable-compression-ratio-engines/papers/automotive/

According to the Wiki article (http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption) a diesel engine running at its best "sweet spot" has a BSFC of 206 (40% efficiency).

It is very possible to build a hybrid where a diesel engine runs at this "sweet spot" to charge batteries and/or supply mechanical and electrical power to high efficiency electric motors, and an electric vehicle is much more efficient than any other at very low speeds and consumes nothing when stopped in traffic. Perhaps a VCR engine can be more efficient at a wider range of conditions than its more conventional cousins, but that is because the overall efficiency of fossil fuel engines is so horrible that it takes very little "tweaking" to get the 30% increase as claimed. The cycle average for a gasoline engine is about 322 g/kWh, or 25%, and the best figure shown for the VCR engine is 472. So it appears to be much worse, actually!

If you can find any other hard figures, please provide them. The low figure for the research report may have been because it was for a 5 HP engine, and there is probably a size factor when compared to automotive engines of 100+ HP.

A.K. Boomer
01-10-2014, 03:09 PM
I did just pull that video out of a hat, it is somewhat complex in design but I did like some of the details of the benefits, and they did say most of the correct things, and had a fair level of sophistication about sensor/input/results related topics...

there really is no "smoke and mirrors" here - the science of thermal efficiencies being increased with higher compression ratio's is a proven fact, you just can't go around lugging an engine with high comp on cheap fuel and expect good results due to either having to retard the timing way back or have your engine die an early death of pre-ignition/detonation,,, it's also not good practice for emissions,

also - along with variable compression ratio is effective compression ratio and volumetric efficiencies - anotherwords - you can take in a full intake charge even though your at a very high RPM, this equates directly to more HP... and due to the engine catching up to the flame front you can get away with quite high ratio's when it's rapping its guts out...

A.K. Boomer
01-11-2014, 10:26 AM
I was just browsing around and found this - It's just a matter of time before someone really perfects these systems for automotive use,,, and they talk of getting it done the same way I mentioned yesterday;

The architecture of the Pinnacle opposed piston engine is well suited to the addition of a VCR system. This may be done through the use of a phaser, similar to the ones used to adjust the timing of a camshaft in a VCT system. The phaser for a VCR system requires a higher torque capacity than the VCT system.

There's also some in depth testing done by the FEV and the mention of incorporating VCR with valve or port timing,

http://www.greencarcongress.com/2013/05/pinnacle-20130515.html

This is where it's at , Its creating engines that go after proven facts of increased thermal efficiencies, Not some guy building a pile of sophisticated crap that does not address any of these issues...

First off - people need to get it through their heads that piston engines are not a big power waster - just because it reciprocates does not mean it's wasting energies, it gets back what it gives minus the friction,

get off the rotary kick - in a total seal IC engine there are no true rotaries as they either have to oscillate or have smaller pivoting or reciprocating movements of some kind, and many are nowhere near as direct in power transmission, not where the answers lie.

Right now the biggest thing to go after is VCR, and it can be done without being too complicated... It will open up a whole new way of engine management...

PStechPaul
01-11-2014, 01:46 PM
Perhaps I have spent too much time on the DIYelectricCar forum, and also perhaps my background as an electronics engineer with experience in motors, batteries, and power conversion, I am still "underwhelmed" by the VCR and VCT and other ICE technologies. The dinosaur has been dead for a long time, and the fossil fuels created in the millennia after its extinction are running low. We need to look at sustainable energy sources as well as ways to reduce our per capita use of energy, so that we can utilize petroleum for its other unique properties to make plastics and pharmaceuticals, rather than just burning it at 20% or even 40% efficiency for electric and mechanical power. The gasoline engine was developed during a time when petroleum was used primarily for heating oil and kerosene, and gasoline was a waste by-product. It was so cheap that even very simple and inefficient engines were practical, and there were not that many in use to cause pollution, global warming, or significant depletion of resources. But businessmen figured out how to market ever bigger, more powerful cars, and increased need for personal transportation with suburban sprawl, to generate huge profits.

Now we have reached the limits of an economy based on cheap energy from fossil fuels, and we are entering an era of inevitable downsizing and change to a lifestyle and aspirations much different from that of the '50s in the US. We have reached "Peak Oil" (as predicted by Admiral Hyman Rickover in 1957 (http://ourfiniteworld.com/2007/07/02/speech-from-1957-predicting-peak-oil/)), and we must deal with the consequences intelligently and realistically. It is good to pursue new technology for ICE power sources, but we are approaching the theoretical limits of energy extraction and conversion to mechanical power. For many years the "holy grail" was the 100 MPG car, but that has now been achieved and surpassed. However, it is impossible to make a 100 MPG SUV or heavy truck capable of towing 6 tons over mountains at 70 MPH. There are physical principles that determine a vehicle's MPG, and to a large extent they determine the fuel economy much more than the efficiency of the power plant. I made a calculator which shows the power and energy required for a vehicle depending on weight, frontal surface area, rolling resistance, speed, and acceleration (or slope), and the results may be surprising, although they are well understood by those who have or make their own EVs:

http://enginuitysystems.com/EVCalculator.htm

The information given in the OP's link does not really show the relative efficiencies of the engines themselves, because the design of the car, along with driving techniques and the terrain covered, have far more effect on fuel economy. The figures given may seem impressive to someone who drives a gas-guzzling SUV or pickup truck, or who drives aggressively, but my reasonably sized car, driven conservatively, already averages 35 MPG and has achieved 46 MPG on a long trip. And it is not a tiny foreign car as seems to have been used for the testing.

Yes, keep working on new ICE designs, and maybe you can eke out a few percent greater efficiency, but the future belongs to electric cars, hybrids, vastly improved public transportation, railways instead of trucks, and a more efficient lifestyle with shared resources and greatly reduced need for daily commutes and traffic jams, as well as elimination of the resultant frustration, lost time, and road rage.

Yow Ling
01-11-2014, 02:39 PM
Instead of trying to make the engine ultra flexible with VC , hasnt it been easier to achieve greater efficiencies with CVT which allows the engine to operate in a very narrow rev range.
I cant see engine makers wanting to mess around with the complexity of VC when they are simply trying to make money, imagine trying to get one repaired.

Paul , you are right about ev's etc being the next big thing, but we will wait till the very last minute before we jump that hurdle, countries outside the US have shown that petrol can cost a hell of a lot more before we stop buying it. We pay equivalent US$7.11 per US gallon and nobody is screaming about it.

Poeople will downsize their cars to get the economy , rather than invest in more complex mousetraps to get a small efficiency gain, then eventually go to ev, hydrogen, producer gas etc

The Artful Bodger
01-11-2014, 02:47 PM
Put the effort into development of a free piston ICE for generating electricity.

darryl
01-11-2014, 03:25 PM
As long as we remain tied to the establishment for our transportation needs, we will be paying a high cost for it. As long as we prove that we are willing to keep paying this cost, we will be able to get alternate forms of transportation. It may be electric, it may be gasoline for the forseeable future- either way it will be expensive. Any means we use in a bid to decrease personal costs will eventually backfire as 'the powers that be' will strongly resist that in one way or another. I think it's likely that there will be taxes and fees impressed on those who are able, for instance, to supply their own power to recharge their electrics. In the case of the IC engine, we will be paying more for the fuel- which will just make it doubly expensive for those who don't have or can't afford the improved IC engine technology.

You can downsize your car, use a more efficient IC engine, make your own power to run your electric vehicle (and your home) but any large-scale disconnect from the burden of paying our 'suppliers' will be met with legislation etc designed to keep the money rolling in (and out of our pockets). No expense will be spared to keep this going, environmentally or otherwise. Until we can overcome this juggernaut, all these schemes to increase efficiency, etc will just be carrots on a stick.

I'm not against improving technology, but I don't see it ever resulting in cost decreases in general. We keep looking at it as if it will, and we are either deluding ourselves or being deluded. We are the cows, and our farmers (our owners) will use whatever means they have to in order to keep milking us.

We, as HSMers and like-minded, may be able to individually create savings and gains for ourselves, and I for one am certainly happy to be able to do that to some extent. If our group gets too large and starts to have some economic impact on the milkers, there's going to be an 'equalization' of sorts- you can bet on it. As I see it, that's the biggest hurdle to overcome, not the relative inefficiency of the IC engine.

PStechPaul
01-11-2014, 03:39 PM
Interesting thought, but if we truly believe in our democratic system and fully participate, we have the power to control the corporate interests that seek only profit without regard to long-term effects on people and the environment. I still believe in that system but I am dismayed at the lack of participation by the citizens who often do not vote, or who seem to lack the intelligence and education to identify lies and misrepresentations by political candidates in their desire to be elected. Many of them accept huge corporate "gifts" to finance dirty campaigns and devious tricks that delude people into believing their assertions and promises.

There have been some indications of excessive corporate practices and political pressure designed to discourage individual sustainable energy initiatives:
http://www.diyelectriccar.com/forums/showthread.php/conservative-political-group-aims-penalize-solar-92031.html

A.K. Boomer
01-12-2014, 10:22 AM
All good points but the closer you get the better off you and your wallet will be, for the most part it's the energy that will be taxed or when the supply can not keep up with the demands be priced higher and higher, as far as the vehicles themselves it may actually work in reverse as is what's going on today with tax breaks and such...

The fact is - is nothing is going to happen overnight, alternatives should be pursued to the fullest extent - but that also means alternatives for the masses of what we will be doing for some time to come - burning fossil fuel.

As far as VCR not being as applicable due to us creating CVT's that keep engines in one range - that is an extremely small percentage of vehicles but even they could benefit greatly just because it's not all "RPM" related, it's load related too, and having a VCR engine that "thinks ahead" and predicts and adjusts for the perfect compression ratio for optimum crank angle whilst the flame front going off is the way we should be utilizing this precious resource,

But instead every power stroke is a compromise due to a fixed compression ratio, therefor we either have to add a higher ratio of fuel for certain load and RPM's to keep the mix cool and from going off prematurely or retard the spark to the point of getting away from optimum crank angle,
If every power stroke is a compromise it is a direct effect on total efficiencies, We do have great computer control over all this stuff - but like I said earlier it's putting the cart before the horse,
we should be using this same bag of tricks but starting with the CR - then adjusting everything else to cover the finer details.

This is so important a fact that I see no other direction for things to go, we will inevitably be "going here" unless somebody comes out with an incredible breakthrough in another field...

wendtmk
01-12-2014, 10:37 AM
This probably tells my age, but when I first saw the title, I was trying to figger out howinell you were going to make an internal combustion engine from a video cassette recorder... ;)

Mark

topct
01-12-2014, 10:50 AM
Changing the compression ratio on the fly is just way to cumbersome. It involves serious mechanical means to do so, and that fact alone makes it impractical.

There is another way to adjust compression. That's by changing the dwell and lift and the timing of the valves. Doing away with the camshaft is going to be the next change we will see. That and a constant speed engine coupled to the mentioned CVT or a motor/generator is very possible. The technology is there to do it easily. And I believe we will see it, instead of, and or long before a variable compression engine.

A.K. Boomer
01-12-2014, 11:44 AM
Your not going to go from 8:1 compression to 16:1 just by changing the valve timing/lift and or duration

I agree that changing compression ratio is complex if we try to do it with a conventional engine ,,, but not with an opposed piston engine, it's as easy as many of the VVT designs out there right now for adjusting cam timing...

and there are not a whole lot more added complexities to some of the opposed piston design and actually a few short cuts as two pistons share the same bore,,, It's why I started this thread, not that far fetched of an idea and once accepted and proven could actually be downright practical...

vpt
01-12-2014, 11:48 AM
This probably tells my age, but when I first saw the title, I was trying to figger out howinell you were going to make an internal combustion engine from a video cassette recorder... ;)

Mark


Thats what I was thinking.

topct
01-12-2014, 12:03 PM
Your not going to go from 8:1 compression to 16:1 just by changing the valve timing/lift and or duration.

Of course not. 16:1 is a bit much. But if you don't open the intake valve all the way and you can change when it starts to open and for how long, you could effect the calculated ratio.

Direct injection would solve any mixture issues and we still have the exhaust valve to play with.

dp
01-12-2014, 12:18 PM
In the case of the illustrated engine the stroke is also changed (length and where it happens) and that has implications for port timing, torque, RPM, and bearing load, but it is certainly quite easy to accomplish. The mechanism shown is also quite limited in range but that is a minor technical matter.

Yow Ling
01-12-2014, 01:01 PM
So we are back to opposed piston engines, which are usually diesel and 2 strokes. The problem with using them with petrol is the exhaust piston gets too hot and causes premature failure. To copy what Brian has done makes for pretty badly compromised ports. But I think you should build one anyway

jdunmyer
01-12-2014, 08:42 PM
I'm with Paul/EVGuru: bought a Nissan Leaf a couple of weeks ago and it has cut the use of my VW Diesel (45 Mpg) to 1 day/week. We seldom do a trip that's much more than 25 miles at one time, so it's easy to keep charged. The car is fun to drive and comfortable, should operate for less than half the cost of the VW, considering $4.00/gallon fuel.

As others have said, hybrids are also a very good solution to cut fuel use.

dp
01-12-2014, 08:46 PM
And you can jump start a Snow engine with that lil' guy. :)

A.K. Boomer
01-12-2014, 09:57 PM
I'm with Paul/EVGuru: bought a Nissan Leaf a couple of weeks ago and it has cut the use of my VW Diesel (45 Mpg) to 1 day/week. We seldom do a trip that's much more than 25 miles at one time, so it's easy to keep charged. The car is fun to drive and comfortable, should operate for less than half the cost of the VW, considering $4.00/gallon fuel.

As others have said, hybrids are also a very good solution to cut fuel use.

You have only had it for two weeks? soooooo no electric bill --- yet... ?


Im looking to a solution for the masses. Yes most everybody could be tooling around in a more efficient VCR vehicle - but try just 5% of us in electric and our grid super-nova's

PStechPaul
01-12-2014, 10:57 PM
An EV used for a 50 mile R/T commute uses about 250 Wh/mile, or 12.5 kWh. Plugged in overnight, 10 hours, it will fully recharge on 125 VAC 10 amps, about the same as an electric heater, and at $0.10/kWh that'll cost ya $1.25. How far can you go on a half-gallon of gasoline?

EVs usually charge at night, when demand is lower, so they help level the power transmission which allows the generators to run at maximum efficiency. There are also systems where EV batteries may be tied to the grid and help supply point-of-use power which lowers the long-haul transmission and distribution load during high-demand times.

And from the money you save over a few years driving an EV, you can install a grid-tied PV solar electric system which can essentially supply all your transportation energy needs as well as almost everything else. A 3000 watt system is now as low as $5000 and will pay for itself in a few years.

At this point in time, the overall cost of an EV, especially with a high capacity LiFePO4 battery pack, cannot be fully justified on economics alone, but it is a good thing because of the environmental benefits of a zero emissions vehicle, and in ten years when gas prices in the US achieve equity with Europe at about $7/gallon, the EV will pay for itself very quickly. A 20% improvement in fuel economy for "new-fangled" ICE vehicles just isn't going to cut it. Also, you can re-use the motor and controller from an EV, and perhaps even the batteries, after 10-15 years in service. Try that with any gas engine, and good luck rebuilding it for the cost of a couple of ball bearings. :p

andywander
01-12-2014, 11:04 PM
I am not understanding how changing the timing of the 2 pistons would lead to greater efficiency.

Seems to me like if the pistons were not exactly in phase, you would have one of them starting on exhaust stroke when the other is still on power stroke....

Willy
01-13-2014, 01:30 AM
So we are back to opposed piston engines, which are usually diesel and 2 strokes. The problem with using them with petrol is the exhaust piston gets too hot and causes premature failure. ...........................


I'm probably a little bit out of the loop here so to speak in regards to some of the new tech ICE stuff being discussed, but when have petrol engines operated at higher temps in the combustion chamber than diesels? Or is this just a characteristic of the technology being discussed here? Or maybe the fuel in this application?
In a conventional 2/4 stroke engine, diesel engines have always operated at a much higher temperature in the combustion chamber than a gasoline engine, contrary to popular belief.


What about heat recovery techniques? All the major players seem to have their hands in this game hoping for some very promising results.
MB, Honda, Renault, Toyota, Cummins, etc. and every other major player in the OEM prime power engine supply business, as well as the manufactures of propulsion systems for power generation systems are already very much involved in this venture.
The list already includes suppliers of large diesel engines and gas turbines that are used for the generation of electricity. These units are already embracing and using this technology as the next hurdle to achieving a more thermally efficient internal combustion engine.

When the the most efficient engines that are in use today...after well over a hundred years of development, can barely scratch the 40% efficiency mark, we have to start looking at waste heat and why it's there. Never mind better ways to either eliminate or use it.

Lets face it, if we had a furnace in our homes this inefficient it would be down the road.

Just as a bit of a side note, as of 2014 every participant in FI is required by the rules to utilize waste heat power recovery technology.
This is not something to be ignored.

A.K. Boomer
01-13-2014, 09:00 AM
Good point Willy - along with greater initial efficiencies I think this is also where its at too.
It can really work out well for a stable load situation like generators and such but there are much more flexible/responsive units being produced now, it is an entirely different system and takes allot of extra components/resources to produce, but so does the typical hybrid.

It would be very interesting to have something of the sort where I live - on mountain roads you would initially call on the throttle and be pouring the coals to it to get up a grade, then after a bit you would actually be backing off the throttle whilst still pulling the same % grade,
If the unit was capable of responding at light load highway speeds it would really jack with your cruise control and cycle it back and forth, sometimes even the typical turbocharger does this due to lag - but I could see a system like this really going through cycles like this - actually would be kind of cool as you would know how much it's helping out,
but when it kicks in it means you would be backing of the throttle - this in turn would cut it's own heat source some - then it would start to fall on it's face,

Yet if the units are turbine/electric or similar then can get around allot of this with storage and electronics...

Besides the typical pressure units,
I believe the next best place to start for waste heat recovery is the cat, they are consuming all the unburnt hydrocarbons and are glowing red hot because of it, but you can't milk too much off of them or you will cool them too much and therefore they will not produce heat and pollute - so some kind of two stage unit might be what's needed if the application is for automobiles due to them needing the flexibility...

wonder what water injection would do right after a cat, then a little electro/turbine to spool up as it turns to an incredible amount of steam..

A.K. Boomer
01-13-2014, 09:40 AM
I am not understanding how changing the timing of the 2 pistons would lead to greater efficiency.

Seems to me like if the pistons were not exactly in phase, you would have one of them starting on exhaust stroke when the other is still on power stroke....

It's pretty wide open what you want to do if it's an opposed piston engine - you are not totally committed to ports and can build a 4 stroke version that utilizes valves instead, these can be manipulated into the VCR mix depending when you want to open or close them.

I stated earlier that a VVT system would be a "freebee" and this is not entirely true, if you mapped out the best compromise between the VCR and the VVT and then let the computer handle the rest you could achieve good results no doubt, but your best results would come from having two separate phasing units - one for the VCR and then one for the VVT.

The only real issue I can see is engine balance, the best mechanical balance would be at maximum compression ratio, this may however go hand in hand at higher rpm's where the engine is trying to keep it's volumetric efficiency up - and higher rpm's is of course where you would want the better harmonics...
It would be a very interesting project to say the least... lots of challenges but at least your chasing something tangible...

MrSleepy
01-13-2014, 01:03 PM
Just as a bit of a side note, as of 2014 every participant in FI is required by the rules to utilize waste heat power recovery technology. This is not something to be ignored.

They have implemented 2 recovery strategies for 2014.
1) MGK - Motor Generator Kinetic....... uses the Drive Train..Used to be called Kers ,but now can use 120Kw per lap.
2) MGH - Motor Generator Heat.......... uses the Turbocharger.

The main use for the MGH will be to spool up the turbo to avoid turbo lag , as the mandated turbos are large and not allowed to use variable geometry.
Also hot and cold blowing using retardation to create gas flow have been curtailed.

Cars have used waste heat for decades to heat the passenger compartment , but it would be interesting to find out wether a exhaust fed stirling engine could be used to run the air con pumps etc.

Rob

Rob

jhe.1973
01-13-2014, 01:28 PM
......... reciprocating pistons do not "waste power" they give back what they take .......



I don't want to throw water on any new and useful ideas in designing anything and agree that this engine is intriquing. I just want to mention that from what I've learned, the above statement is not accurate.

If you total all of the power lost in a piston engine you will find that over half of it is lost at the piston and small end of the connecting rod.

When I was the Experimental Machinist for Harley-Davison's Racing Department (whoopee...official title :D) I spent a lot of time lightening piston pins and pistons just to help regain some of this lost power (energy).

A way that I have visualized this is to use the example of valve springs that may have 150 - 200 pounds of pressure (just to throw out numbers).

In order for the valve components, that are easily held in the hand, to overcome this pressure and float away from the cam at high RPMs (worst case hitting the pistons) they have to 'weigh' more that this. The 'weight' comes from the inertia and it can easily be seen that a piston moving over a far greater distance has to be restrained with a far greater force to keep it from breaking the connecting rod and hitting the cylinder head. Plus, once stopped it has to be reversed.

The energy to restrain the piston, stop it and reverse direction has to come from somewhere.

When I first saw a Wankel design I was skeptical that it would put out very much torque seeing as how it didn't have a connecting rod and crank, as such. The Wankel put out great torque mostly because it had no piston losses.

When I later learned that torque was more a result of cylinder filling than crankshaft leverage, the Wankel design made even more sense.

The Artful Bodger
01-13-2014, 02:16 PM
reciprocating pistons do not "waste power" they give back what they take

Not quite, there is friction of course from bearings and sliding surfaces, there is windage causing friction in the air getting stirred up and there is noise which is also friction. The metal is also being stretched and compressed, more friction.

PStechPaul
01-13-2014, 03:16 PM
I've often wondered just how much excess heat is created by a gas engine and where it goes. If a 100 HP engine is running at 40% efficiency then there must be 60% of the fuel wasted. So we might get 40 HP of mechanical power and 60 HP or 45 kW of heat. That is enough to heat a large building or five houses. Even with the cooling system putting out heat from the radiator, and the engine block and transmission running at 180F or so, and the catalytic converter running even hotter (but not red hot), it seems that there is nowhere near that much heat. So the only other possibility is that the exhaust gases still contain unused energy. CO2 and H2O are products of complete combustion, and no more energy can be extracted by chemical processes, so the only waste products that might have usable energy are carbon monoxide and perhaps other combustion byproducts such as NO2 and SO2. But these are limited to small amounts in a well-tuned engine with effective emissions controls. So where does the energy go?

The excess heat for warming the cabin is probably no more than 5000 watts, and under some conditions the main thermostat remains closed and the radiator must be blocked so that the engine can reach normal operating temperature where it runs more efficiently. And other factors such as the transmission and drive train are not counted in the efficiency of the engine itself. The efficiency from fuel input to actual power on the pavement is even worse, and highly variable.

I think the answer is, partly, that the actual power needed for a typical 3300 lb car moving 62 MPH on a 2% grade needs just 27 HP, and 16 HP on a flat road. So under these conditions, the 60% power loss is about 35 HP or 26 kW. That still seems like a lot. I don't really have an answer, but it just seems that there is another "energy leak" that is not simply heat.

Of course, there are other considerations that are not usually factored in when determining ultimate fuel economy. There is also the cost of extracting the crude oil, transporting it, refining it, and delivering it to the pump. There are also comparable costs for electricity and other energy sources, but at least electricity CAN be obtained by sustainable means, such as solar and wind. BUT, until recently, the total cost for manufacturing and maintaining PE cells over their lifetime could be shown to be greater than the equivalent cost of the energy extracted from the sun.
http://tinaja.com/glib/resbn48.pdf
http://sci.tech-archive.net/Archive/sci.electronics.design/2006-04/msg03160.html
http://www.tinaja.com/glib/energfun.pdf

A.K. Boomer
01-14-2014, 10:37 AM
The energy to restrain the piston, stop it and reverse direction has to come from somewhere.


Did you just hear what you said? let's tune into the one particular spot what you said "stop it",

"stopping the piston" IS your energy return system, getting the piston moving up to speed extracts power from the crankshaft - putting the "brakes" on the piston after it reaches maximum feet per second gives back the exact same amount of energies that it took out of the crank in the first place - minus frictional losses of both speeding up and stopping and elasticity of materials blah blah blah,,,

Point being is it's not in the way most engineers think, yet that being said Iv built my fair share of race engines too, and the higher the RPM's the more critical this reciprocating weight is but it's only due to frictional losses in the form of a multitude of ways,,,
tapered piston pins - lightweight pistons and the machining of the small end of the connecting rod is a great way to handle this, Iv done hundreds of rods this way - the big end is not much of a factor but the small end is full reciprocation, when your race engines are held down to strict rules and regs on how light you can go on a connecting rod this is where you put your focus, we would take the small end down to where it looked outright scary,,, (never lost one) then still leave enough on the rods to where we could balance them "end per end" and not only match up total rod weight - but the more critical small end weight would be a direct match also - within 1/2 a gram...
We would get a competitors engine in and see that they had hogged all the material off the beam and big end - these were people who lacked an understanding of the dynamics of how to reduce high RPM frictional losses...

so YES it does help to keep these parts light - but that being said, one needs to know just why your keeping them light so your theory of operation remains solid,,,

And first and foremost is the fact that the weight itself is giving back exactly what it takes... (minus frictional losses) You would not believe how many "experienced engineers and race engine builders" don't know this,

When you get a grasp on proper theory of operation you then can recognize the finer details as to why things are the way they are,
You then come to grips with the realization that there is a "cost of doing business" involved with any total seal IC engine,,,
and rotary's will also never be immune to this - they will always have to have something to "pry off of" whilst the internals are under load - or in the free-run mode will still waste a certain amount of energies due to oscillations or smaller timed reciprocating or spring loaded components, it is theoretically impossible to build a total seal IC engine without,,,




When I first saw a Wankel design I was skeptical that it would put out very much torque seeing as how it didn't have a connecting rod and crank, as such. The Wankel put out great torque mostly because it had no piston losses.

When I later learned that torque was more a result of cylinder filling than crankshaft leverage, the Wankel design made even more sense.

Hmmm - wonder why they are some of the most inefficient gas pigs on the planet - they do not even come close to the cumbersome piston engine that's "wasting" all that power in "reciprocation"...

Again, no matter where you look you will find that there's a cost of doing business in this matter,,, and the piston engine is a damn good design and in fact that's why it's hauling 99.99% of us back and forth to work or to pick up and haul our precious machinery and the like... I spent about two years dabbling in rotary design when I was in high school - then it dawned on me that the piston engine gives back what it takes - minus the frictional losses - don't like the frictional losses?
get a roller crank and rods and your reciprocating energy return system will be more efficient - no matter what the weight of the parts...

pistons are a beautiful thing...

A.K. Boomer
01-14-2014, 10:40 AM
Not quite, there is friction of course from bearings and sliding surfaces, there is windage causing friction in the air getting stirred up and there is noise which is also friction. The metal is also being stretched and compressed, more friction.

See post above, "the cost of doing business" in a total seal IC engine, your statement and all the details within can be applied to any and all Total seal IC engines...

A.K. Boomer
01-14-2014, 10:44 AM
and the catalytic converter running even hotter (but not red hot), it seems that there is nowhere near that much heat.

Cats run above and beyond "red hot" - most cats could heat a small building...

PStechPaul
01-14-2014, 11:00 AM
Perhaps the transformation of energy from kinetic to potential and back are misunderstood. This is well known and used in EVs that have the means for regeneration. Piston engines can be used as pumps to compress air which can be used later.

An idea I just had is to make a sort of "double piston" with a strong spring connecting them in the same cylinder, so that the initial power stroke compresses it when the piston is at TDC and cannot move. The exploding fuel-air mixture might burn more efficiently if it is allowed to expand more quickly. As the crankshaft rotates, the pressure in the cylinder and the spring work together to provide power throughout more of the rotation, and it may have more force at the 90 degree point at which it has the best mechanical advantage. This would also reduce the stresses and shock on the bearings especially if there is any premature detonation or knocking.

A.K. Boomer
01-14-2014, 11:14 AM
The exploding fuel-air mixture might burn more efficiently if it is allowed to expand more quickly. .

It's a thought - but I think what completes burn rates and therefor better fuel efficiency within the combustion cycle is the extreme pressures which in turn create more heat which in turn complete the burn cycle,,,

might be some kind of way to create an engine that runs off of detonation though - keep the mix ultra lean to create the effect but then I think you would have the NOx peoples panties in a wad...

Getting back to the reciprocating thing - in a way we blame reciprocation for the losses when actually most of it's due to our archaic usage of crude plain bearings and such that screw up the energy return system... just another way of looking at it due to properly understanding theory of operation.

PStechPaul
01-14-2014, 11:34 AM
Cats run above and beyond "red hot" - most cats could heat a small building...
The critical minimum temperature of a catalytic converter is 400-600F, and the maximum normal operating temperature is 1380F.
http://en.wikipedia.org/wiki/Catalytic_converter
http://www.aa1car.com/library/converter.htm

Many years ago my friend and I worked on a display that would show the operating temperature of the cat, in the days before OBD and widespread sensors. It sensed not only the actual temperature, but the differential between input and output. I don't remember the exact thresholds, but they could be measured with a thermocouple.

Red hot is 500 to 800C, or 932 to 1472F, so I stand corrected. But I don't think the power is any more than 3000-5000 watts. The entire converter is roughly the size of a space heater, and its element gets red hot. A space heater is only about 1500 watts maximum. It should be possible to estimate the power dissipation from the temperature and surface area, but there are other factors involved, such as emissivity and air flow, which can be significant under a moving vehicle.

Is there a physicist in the house?

A.K. Boomer
01-14-2014, 12:07 PM
Well your allot closer than what I thought too, all's I know is I have to work under them sometimes and it's unreal the amount of heat their throwing off, and that's a mild little stop and go drive to my shop not pulling a grade or even on the highway,,,

I did however "witness" the amount of heat that's involved when a V8 quattro valvola Maserati hit's on only 7 cylinders for only a brief period and then starts throwing out chunks of molten ceramic honeycomb from it's exhaust pipe... but that's a whole nuther issue...

jhe.1973
01-14-2014, 12:36 PM
Did you just hear what you said? ..............

so YES it does help to keep these parts light ............



Thank you for making my point for me. By admitting that it helps to keep these parts light you have agreed with me that if left heavier they absorb more power.

All power in a heat engine comes from the expansion of the fuel. The piston does not create any of this power so it cannot ‘give back’ what it has never created.

The inertia – not friction – of the piston assembly (mass) is what robs the power. Reducing this mass reduces the energy lost through inertia. Friction has nothing to do with it.


When you get a grasp on proper theory of operation you then can recognize the finer details as to why things are the way they are, You then come to grips with the realization that there is a "cost of doing business

Several of your statements such as this show me that you are more interested in debate than discussion and I refuse to be manipulated into a debate.

I am so sorry that I don’t have a grasp on proper theory and I concede that you are the more skilled debater.

The Artful Bodger
01-14-2014, 02:14 PM
Again, no matter where you look you will find that there's a cost of doing business in this matter,,, and the piston engine is a damn good design and in fact that's why it's hauling 99.99% of us back and forth to work or to pick up and haul our precious machinery and the like.
pistons are a beautiful thing...

They are not really beautiful, just the best we have right now for road vehicles, ships and locomotives.

ikdor
01-14-2014, 05:59 PM
To answer an earlier question as to where most of the energy goes, it goes out the tailpipe and through the cylinder wall.
This graph looks like a decent one, I've seen fancier ones in the office. This one is in German but you can have a guess at what's what:exhaust 34.8, wall losses 29.4, charge pumping losses 4.1, friction 8.4.
http://www.e-sankey.com/uploads/tx_ifugallerydiagrams/sankey_diagramm_pkw_wirkungsgrad.png

To come back to using waste heat recovery, it's indeed possible to harvest the energy from the exhaust. The trick is finding the best cost/performance ratio. There's a couple of favourite topics:-
- exhaust heated steam engine by BMW already a few years ago
- exhaust heated thermo electric generators
- and the one we'll see soon on long haul trucks, the organic rankine cycle powered by exhaust gas. On a commercial truck you'll be able to harvest about 10kW using this. It will take some engineering though to take the cost out and package it in the trucks.

Formula one is harvesting not only heat, but also the pressure and kinetic energy in the exhaust gas. They basically put a large generator on a turbo-like turbine wheel and feed that energy back to the car. There is a some loss from the increased back pressure but the energy harvested is worth it.

Igor

A.K. Boomer
01-15-2014, 11:39 AM
Thank you for making my point for me. By admitting that it helps to keep these parts light you have agreed with me that if left heavier they absorb more power.

That's never been an issue, but understanding the reason as to "why" is - and your theory of operation is flawed...


All power in a heat engine comes from the expansion of the fuel. The piston does not create any of this power so it cannot ‘give back’ what it has never created.

of course it does, your getting power production mixed up with parasitic drag dynamics... All engines have to pay the fiddler on the latter, like I stated before there is and always will be a "cost of doing business"...



The inertia – not friction – of the piston assembly (mass) is what robs the power. Reducing this mass reduces the energy lost through inertia. Friction has nothing to do with it.

Your still not getting it at all, Friction has everything to do with it, it's simple kinetics, the crank gets robbed accelerating the piston from TDC to maximum feet per second - after that fact it's payback time as the piston that wants to keep moving @ MFPS is then forced to slow down, but - it's forced to slow down in the direction of crankshaft travel that then puts the same identical kinetic energy (minus the frictional losses) back into the crank, it's simple physics and cannot be disputed - toss a base ball from one hand to the other - the energies to toss the ball and catch it are identical - minus the frictional losses of the ball traveling through the air,

You totally ignore the most simplest of physics laws, "To every action there is always an equal and opposite reaction"

reciprocating pistons are kinetic devises attached to a rotating crankshaft and flywheel that stores energies, in one half of a crankshaft revolution starting from TDC and ending @ BDC - pistons take X amount of energies from the crankshaft and give the exact same energies back - minus the frictional losses...

Don't blame the baseball for not hitting the other hand with the same amount of energies - because in a vacuum it would, blame the air for taking some of the "umph" out of it,

again, don't blame the identical give and take reciprocating energies of the piston engine because your theory of operation is then "tainted"
You made the statement that friction has nothing to do with it, Friction has EVERYTHING to do with it - and the more mass of these reciprocating parts the more friction...
that's why you keep them light - also helps to keep them from self destruction...


Several of your statements such as this show me that you are more interested in debate than discussion and I refuse to be manipulated into a debate.

I am so sorry that I don’t have a grasp on proper theory and I concede that you are the more skilled debater.

I made this statement right after talking about the guys who removed the weight off of the wrong end of the connecting rod;

"And first and foremost is the fact that the weight itself is giving back exactly what it takes... (minus frictional losses) You would not believe how many "experienced engineers and race engine builders" don't know this,

When you get a grasp on proper theory of operation you then can recognize the finer details as to why things are the way they are"

But now I have to make it towards you due to you thinking that friction has nothing to do with it and somehow Sir Isaac Newton is incorrect,
fact is is if you make the reciprocating parts strong enough to hold together and run everything on needle bearings you can achieve less losses than the same engine running on plain bearings that has lighter reciprocating components - both at redline...
It's all about friction, but the far easier solution is to lighten up the parts so your connecting rods (and bearings) are not trying to hold up small buildings at 7,200 RPM's, it's either that or build a tractor engine and don't worry about it...

no matter the weight, pistons give back the identical power that they consume - minus the frictional losses...

frictional losses increase with more weight...

andywander
01-15-2014, 11:58 AM
Umm-a piston(or anything else) that is moving in a certain direction needs to be accelerated(have a force applied to it) in order to change direction.

Just because it moves back in the opposite direction with the same speed, does NOT mean it has the same velocity. In fact, it has exactly the opposite velocity. if it was originally 10m/s north, it will now be 10m/s South, or in other words, it goes from +10m/s to -10m/s velocity.

The energy in the piston is 1/2mv^2, so reversing the velocity means that twice this amount of energy must be supplied in order to reverse the piston motion. This is supplied by the inertia of the crank and flywheel, along with that of the other pistons on a power stroke(if any), and acts to slow the rotation of the crankshaft. Twice the energy of the moving piston is thus used to accelerate the piston, and this happens every time it reverses direction. The only thing that keeps the engine running is the fact that one of those strokes is a power stroke where an external source of energy(the expanding combustion gases) is introduced.

The idea that a moving piston being reversed somehow "gives back" it's energy to the system is just wrong. disintegrate the piston pin or teh connecting rod and it will just keep going in the same direction, without reversing.

PStechPaul
01-15-2014, 02:24 PM
The chart posted by ikdor shows that heat from friction is only 8.4% of the total power consumption of an engine with about 18% total efficiency from fuel to the wheels. Most (64%) of the losses are heat through the walls of the combustion chamber and out of the exhaust. If you have an engine with only the pistons and crankshaft in the block and operate it by hand, it takes little effort to keep it moving by exerting pressure on the pistons, and the faster you turn it, to some degree, the easier it is, due to rotational inertia. A fully assembled engine (with plugs removed) takes more effort because of the valve springs and camshaft operation, but much of the energy absorbed in the springs is returned when they decompress.

It may be difficult to envision, but the linear acceleration and force of the piston is converted to rotational inertia in the crank, and in a well designed engine the mass is balanced so that the conversion is very efficient. The entire mechanical process of using the pressure of the burned fuel-air mixture into rotational energy at the crankshaft is just conversion from potential to kinetic and back again, with the only mechanical losses being due to friction and stresses on the components (consider the heat generated by bending metal).

I think the actual inefficiency is based on the way the fuel-air mixture burns in the confined space of the combustion chamber. At TDC, the pressure increases rapidly and exerts a powerful force on the cylinder head and the piston, which cannot move. But since the crankshaft is moving, the volume of the chamber increases and the pressure decreases. The exact (thermo)dynamics may be complicated, because the combustion does not take place evenly and the volume is changing in one direction (two directions in an opposed piston design), and the efficiency is a trade-off based on burning rate and compression ratio and speed.

The idea I proposed would allow an immediate expansion of the combustion chamber to several times the volume at TDC, storing the energy in a spring rather than extremely high pressure and temperature as it is in a conventional engine. Then the spring would return this energy to the piston as it moved, so that the combustion chamber volume would remain relatively constant for a significant portion of the power cycle, and perhaps deliver the most power at the 90 degree crankshaft angle where there is maximum mechanical advantage.

The Artful Bodger
01-15-2014, 02:44 PM
Just because it moves back in the opposite direction with the same speed, does NOT mean it has the same velocity. In fact, it has exactly the opposite velocity. if it was originally 10m/s north, it will now be 10m/s South, or in other words, it goes from +10m/s to -10m/s velocity.

Ummm, you have me thinking about that. I thought the piston went from 0m/s to +nm/s then back to 0m/s on each stroke. I dont see any carry over of piston inertia from one stroke to the next.

MrSleepy
01-15-2014, 02:55 PM
The idea I proposed would allow an immediate expansion of the combustion chamber to several times the volume at TDC, storing the energy in a spring rather than extremely high pressure and temperature as it is in a conventional engine.

The camless Koenigsegg engine aims to be able to store braking energy as compressed gas , as the engine works equally aswell as a compressor.....so possible could use your idea aswell.

F1

The inclusion of the Motor Generator- Heat is a bit of a red herring for heat energy recovery.

The size of the FIA mandated turbo is massive (as shown in the Renault engine PDF below)...and would have led to a turbo lag of 2-3 seconds..The MGH is being used to spool up the tubine to reduce the lag to acceptable limits.
http://www.renaultsport.com/IMG/pdf/rsf1-moteur2014-presskit-en_final2.pdf

Rob

andywander
01-15-2014, 03:49 PM
Ummm, you have me thinking about that. I thought the piston went from 0m/s to +nm/s then back to 0m/s on each stroke. I dont see any carry over of piston inertia from one stroke to the next.

Sure, I was trying to simplify things. It does not go from full speed in one direction to full speed in the other instantaneously.

Let's start with the piston at the bottom of it's stroke, and not moving. The work to accelerate the piston on the next upstroke needs to come from the crank. At some point in the stroke the piston reaches maximum speed. It has some kinetic energy. Now, we need to slow the piston down, and eventually stop it, before reversing direction. The crank is still trying to rotate in the same direction, but now it acts to slow the piston down---hmmm, so the piston is still trying to move at the same speed, but the crank is slowing that reciprocating motion down, meaning that the reciprocating motion is trying to speed up the crank rotary motion.......well, I think I have convinced myself that I was wrong, at least some of the energy due to piston motion will be returned to the crank....

The only thing that can slow it down is the crank(besides friction), and if you think about it, the crank does this fairly gradually because of teh mechanis of teh conversion of rotary to reciprocating motion.

A.K. Boomer
01-15-2014, 08:07 PM
Sure, I was trying to simplify things. It does not go from full speed in one direction to full speed in the other instantaneously.

Let's start with the piston at the bottom of it's stroke, and not moving. The work to accelerate the piston on the next upstroke needs to come from the crank. At some point in the stroke the piston reaches maximum speed. It has some kinetic energy. Now, we need to slow the piston down, and eventually stop it, before reversing direction. The crank is still trying to rotate in the same direction, but now it acts to slow the piston down---hmmm, so the piston is still trying to move at the same speed, but the crank is slowing that reciprocating motion down, meaning that the reciprocating motion is trying to speed up the crank rotary motion.......well, I think I have convinced myself that I was wrong, at least some of the energy due to piston motion will be returned to the crank....

The only thing that can slow it down is the crank(besides friction), and if you think about it, the crank does this fairly gradually because of teh mechanis of teh conversion of rotary to reciprocating motion.


Good duty,,, plain and simple - you "get it"...