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highest brake thermal efficiency heat engine recorded?

highest brake thermal efficiency heat engine recorded?

highest brake thermal efficiency heat engine recorded?

(OP)
Hi guys

I remeber a thread that discussed the difference between 2 stoke engines and 4 storke engines, one member pointed out that the highest acheived thermal efficiency was acheived by a 2 stoke engine in a large cargo ship, diesel cycle. I searched through the 40+ pages of threads title's here and couldn't find it!!!

I am interested in the highest break thermal efficiency of ANY heat engine recorded. operating on any cycle, otto, diesel etc.

thanks

RE: highest brake thermal efficiency heat engine recorded?

I'm not sure what your asking for, but AFAIK the ultimate limit for specific HP is 2.0, thats 2.0 HP/Lb fuel/hr.

RE: highest brake thermal efficiency heat engine recorded?

(OP)
Thermal efficiency of most diesel cycle truck engines can are 40%, petrol engine general 25% at a higher rpm.

I'm after what is the highest thermal efficency, regardless of the type of engine, or particular fuel used. Just the highest thermal efficiency from any heat engine.(combustion engine, internal or external) i.e one that must obey the carnot cycle. i.e excl. fuel cells.

hope thats clearer??

RE: highest brake thermal efficiency heat engine recorded?

Yeah thats clearer, Though I remember some of that form P-chem, and metallurgy thermo classes its out of my feild of knowledge. I do remember some old Popyular science's were really big on sterling cycle engines.

nick

RE: highest brake thermal efficiency heat engine recorded?

this fan-site puts the Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel at about 50%.  I'm not sure that it's actually the most efficient.  

Do you want to count overall system thermal efficiency for cogen applications, or just (flywheel mechanical power)/(fuel power)?

RE: highest brake thermal efficiency heat engine recorded?

Cogeneration plants with a turbine and steam engine are above 55% efficiency as we speak.

RE: highest brake thermal efficiency heat engine recorded?

The big sulzers with power recovery and cogeneration most likely beat that 55%.
But think the fuel cell technology is the most efficient so far.

RE: highest brake thermal efficiency heat engine recorded?

(OP)
ohhh, I guess I'm not after co-geration either. I found this website for largest diesel diesel states over 50% BSFC. that is basically what I'm after. can anyone point out better? without cogeneration.

http://www.bath.ac.uk/~ccsshb/12cyl/

RE: highest brake thermal efficiency heat engine recorded?

hehehe... looks like I forgot to attach the link to my original message.

RE: highest brake thermal efficiency heat engine recorded?

"Thermal efficiencies of 54% have been demonstrated by single cylinder engine testing of advanced diesel engine concepts developed under Department of Energy funding"

http://www.osti.gov/bridge/product.biblio.jsp?osti_id=771103
 (if interested, get the paper, read the list of references, find the 54% test engine)


http://www.marintek.sintef.no/MarPower/SOARep1/SOAR1.HTML
1.  State of the art concerning thermal efficiency (see plot)
Not included in this figure is the hot combustion combined cycle diesel engine. This engine is designed for less cooling of the cylinder so that a greater part of the combustion energy is retained in the exhaust. The exhaust is subsequently led through a heat exchanger where steam is produced for expansion through a turbine. This system is capable of a 55% efficiency (7), but it's size and cost is makes it unfavourable with today's fuel prices. Similar efficiencies are reported for large diesels with turbo compounding, where part of the exhaust bypasses the turbocharger and is expanded through a power turbine geared to the shaft or camshaft.

http://www.manbw.dk/documents/p291_0108.pdf
see page 8 - plot shows system efficiency over 56% for combined cycle w/ steam turbine, 53% for diesel alone (I think)




RE: highest brake thermal efficiency heat engine recorded?

You'll find fuel cells at 80% effiency, but they use hydrogen.  The process to create hydrogen is only 50%, so net at 40% for a fuel cell.

RE: highest brake thermal efficiency heat engine recorded?

(OP)
dcasto,

"You'll find fuel cells at 80% efficiency"

show me a link to a fuel cell with 80% efficiency . . . you might like to comment in another thread I started in . . . .Home > Forums > Trends and Strategies > Keeping Ahead of the Curve > Where is Engineering Going In The Next 5 Years Forum . . . .


Internal Combustion Engine Or Fuel Cell Vehicles?
Thread730-96360

RE: highest brake thermal efficiency heat engine recorded?

Definitely not relevant, but I wonder how living organisms compare to mans efforts ?

Lbs/hour of food to mechanical work hehehe.

RE: highest brake thermal efficiency heat engine recorded?

Random web results:

Efficiency of plant turning light energy into glucose: 33%

Reputed mechanical efficiency of hard working human: 40%

So, solar equivalent efficiency: 12% - not bad actually!

The problem is you have to work your slaves hard, they burn 150 W even when idle.

Cheers

Greg Locock

RE: highest brake thermal efficiency heat engine recorded?

Reputed mechanical efficiency of hard working human: 40%

A number that was quoted to me in college was 2%, but without the "hard working" part...

RE: highest brake thermal efficiency heat engine recorded?

Sounds about right to me. I am sure some work 20 times harder than others for the same food intake.

Just look at the obesity trends in the developed world

Regards
pat   pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: highest brake thermal efficiency heat engine recorded?

I think that (40%) is a very poor estimate - I suspect it is the direct conversion efficiency for additional work done, ie does not include the baseline energy consumption.

You IC'ers have a similar measure, showing the incremental fuel required for incremental additional work done. I think it may be called the Wilson line ? I read a report recently showing the non existent improvement in this over the last 10 years - which, since it measures the basic thermodynamic efficiency of the combustion process, may or may not be a surprise.

Cheers

Greg Locock

RE: highest brake thermal efficiency heat engine recorded?

(OP)
best solar cells are from UNSW (uni New South Wales) stated at 26%. but solar cells are funny critors they can only be labbeled at that efficiency for particular light wavelengths and when the cell is directly facing the sun. Thus you can expect much lower overall efficiency when you consider the energy required to follow the sun. and the fact that the 26% is generally only reached during mid-day when the sun beams etc show little refraction through the atmosphere(but then again I'm no expert I'm just guessing) sun rise and sun set efficiency is almost useless in total.

The CSIRO Energy Centre (researching use of hydrogen) in newcastle has over 1 million dollars worth of solar cells on the roof of their building, not one follows the sun! why? It would require more enrgy to follow the sun then they get back from each cell, interesting!!(but on the same token some are pretty cool in the way that the solar cells are transparent and allow to put them on a standard window!! thus when you put them on a sky light, they generate electricity and the same time as save you useing a light during day light hours hence the way the energy centre office is set up.

I wonder how they go about measuring a plants solar efficiency? I would image some plants are more efficient than others? I wonder if they also use solar thermal energy?

On the topic of human's food to work output, we understand that control mechanism's require power too, EFI etc, thus I wonder how much goes to driving our brain, some of us seem to use them more then others too . . heehee

Thus if mechanical output is 40% of food, for some of us the other 60% might to the brain, and for some it seems to never gets there at all hee hee.

RE: highest brake thermal efficiency heat engine recorded?

From a purely engineering aspect, high body fat could be regarded as potential energy...... Or maybe ballast ?

There is a very nice simple way to track the sun with nothing other than solar energy. The way to do it is to mount your solar collectors on an equatorial mount so it can rotate freely parallel to the earths rotation.

You then fit interconnected freon gas cylinders far apart either side of the rotation axis. Simple shades can be arranged so more sunlight falls on one cylinder than the other if the collector is not directly facing the sun.

Gas will boil in the hot cylinder and condense in the cooler cylinder, and weight will transfer, maybe a lot of weight. Gravity will then steer the collector and it will track the sun.

It is fascinating to see several of these wake up in the morning and quickly race each other back from the previous sunset position, to seek the new sunrise. Some hydraulic damping will stop wind turbulence from rocking things too much.

Sorry to hi-jack the thread, but this stuff fascinates me.

RE: highest brake thermal efficiency heat engine recorded?

I was just going to mention the threadjacking taking place.  Perhaps another thread (but which forum?) would be more appropriate?  

RE: highest brake thermal efficiency heat engine recorded?

At the risk of threadjacking...

"Reputed mechanical efficiency of hard working human: 40%"

Hmm, for man powered flight the estimate is 1kW heat dissapation for 200Watts mechanical output. This makes cooling, without introducing drag, an interesting problem. I make that 20%, which probably falls into line with Gregs comments. For more relaxed cycle touring, that output is nearer 100Watts (still at 20% I assume).

Kindof makes you wonder why we don't all commute in light aerodynamically shelled recumbent bicycles...

Mart

RE: highest brake thermal efficiency heat engine recorded?

Kindof makes you wonder why we don't all commute in light aerodynamically shelled recumbent bicycles...
because it'd be too darn hot inside, and most people would just fall over.

RE: highest brake thermal efficiency heat engine recorded?

The CSIRO Energy Centre (researching use of hydrogen) in newcastle has over 1 million dollars worth of solar cells on the roof of their building, not one follows the sun! why? It would require more enrgy to follow the sun then they get back from each cell, interesting!!

I can't believe that's true. Though I can believe they might think it. My son bought a couple of crêpes about a month back and the guys cooking the crepes were using reflectors to shine sunlight onto the bottom of the metal plate that the pancake mix cooked on - a solar powered crêpe cooker. To make the reflector follow the sun they had a crude mechanism with a chain driven by an electric motor and probably some gearing - I didn't study it in detail, I was just buying a crêpe for a 6 year old.

The electric motor was connected to two small solar cells, say about 6 square inches each (ie 6" by 1"), and I had the impression it was just used to determine a voltage difference. Whichever cell generated the bigger voltage or current or whatever would determine which way the motor turned, if at all.

They had a couple of strange old glass bottles (filled with water) where the diameter seemed to have been chosen to focus a large width of sunlight onto the narrow solar cell strip.

So if the reflector was a bit off track, one cell would produce more than the other, feed the motor, motor would run a touch, and gearing would move the reflector.

==

In the Science and Industry Museum at Manchester they have a toy for kids to play with. Its a marble sphere weighing just under 100 kilograms, over 200 pounds say if you want to think imperial units. My 6 year old used to have fun spinning it round as fast as he could.

The point is it takes very little force to spin it, since it revolves around its own centre of gravity. So while you cannot stop it or start it moving quickly in a short time, it is surprisingly easy to manipulate given that the thing is near impossible to lift up. It is litterally child's play.

Moving something around its center of gravity once in a day takes very little work.

==

So the problem might be that you have a load of experts in hydrogen power where solar power experts are required. Or they might be over engineering things.

If you stir a scotch on the rocks, the drink doesn't warm up until the ice cubes have melted. If you over-engineer that problem you could have teams of scientists studying deflections in the gulf stream and trying to calculate net global changes in ocean temperatures due to global warming, instead of just saying nothing much happens until Greenland is green again. Trying to calculate the temperature at any point in your scotch on the rocks is a pointless exercise for the people that haven't grasped the basic principle that the drink only really starts to warm up after the ice has melted.

RE: highest brake thermal efficiency heat engine recorded?

Yes I agree with you up to a point, but it is not that simple. Concentrating radiant solar heat with a tracking and focusing system to generate high temperatures is fairly simple.

But with solar panels you will have a vast exposed area that needs to be kept perpendicular to the incident solar radiation without concentrating or focusing it.

Suppose you have five hundred square meters of panels, a tracking mechanism will be a fairly impressive piece of hardware no matter how you go about it. And then there is also the problem of wind loading, especially gusts and turbulence on the structure.

All things considered it is usually more economical to just increase the area of panels rather than attempt to build a tracking system.

RE: highest brake thermal efficiency heat engine recorded?

(OP)
crysta1c1ear,

most of your points have been talking about using solar thermal energy and not using solar light energy (solar cells)

As you pointed out you can use two solar cells when one has more light the cells can be rotated until both are equal. this in fact would ensure a large percentage of solar cells are never exactly facing the sun at any point in time (same as if they are fixed), and then some of the energy from the cells receiving low level light goes towards turning the motor. thus you are back to square one you may as well have them fixed in one position. the idea is too investigiate this before putting them in place Im sure the csiro has done this and they know what they are doing.

The point I was trying to make is that if the tracking of the sun require an amount of energy that comprimises the overall energy obtained from the cells then you obviously are not talking about much energy obtained from the cells in the first place.

RE: highest brake thermal efficiency heat engine recorded?

Hi-
      The highest reported brake thermal efficiency that I have seen was 57 % for an opposed piston diesel operating at very high cylinder pressures.  The place where I think that I saw this reported was in WARD's Automotive Weekly.  This was a research project probably done for the US army and/or the EPA.  
       The peak temperatures were quite high, which is part of how they achieved such high brake thermal efficiencies.
       The designers of this engine did NOT try to recover any of the exhaust waste heat, so the potential brake thermal efficiency was even higher.  
       Recovery of some of the exhaust energy is possible for IC engines but generally the added cost / complexity make it not worth the effort.


RE: highest brake thermal efficiency heat engine recorded?

"The highest reported brake thermal efficiency that I have seen was 57 % for an opposed piston diesel operating at very high cylinder pressures."

Now that is interesting! Any further info?

Mart

RE: highest brake thermal efficiency heat engine recorded?

The designers of this engine did NOT try to recover any of the exhaust waste heat  

It was a diesel w/o turbochargers?

RE: highest brake thermal efficiency heat engine recorded?

Hi-
      This was a diesel with turbochargers.  The exhaust temperatures out of the turbocharger were still pretty hot.  By "recover the exhaust heat",  I meant use a Rankine cycle (steam cycle) or other bottoming cycle to recover more work from the exhaust heat.
      I believe that this project was sponsored by the US government so there must be more info out there somewhere.  I don't know where the info is.
      If I remember correctly, the engine had two connecting rods per piston to deal with the large forces generated.  Cylinder pressures were very high and emissions were probably very high as well.
        

RE: highest brake thermal efficiency heat engine recorded?

The only opposed piston diesel I ever saw was the Commer Knocker.

It had 2 con rods per piston, because it only had one crank and used piston, con rod, rocker arm, con rod, crank layout.

Maybe I don't have a clear picture of the layout you refer to, but I can't imagine how two smaller rods would be stronger than one large one.

Regards
pat   pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: highest brake thermal efficiency heat engine recorded?

"I believe that this project was sponsored by the US government so there must be more info out there somewhere.  I don't know where the info is."

Thanks J2prometheus, I'll do some googling...

Mart

RE: highest brake thermal efficiency heat engine recorded?

Pat:

There are lots more opposed piston diesel engines, just in the UK.

The English Electric 'Deltic' was famously successful in rail locomitives from 1950s to 1980s - developed 3300 hp.

Chieftain tanks used a multi-fuel 2-stroke 6-cylinder (12 piston) blower-scavenged engine developing about 750 hp. Designed by Leyland and called the L60. A smaller brother (K60) powers the ubiquitous FV 430 vehicle.

Don't know about efficiencies of these, though.

Cheers - John

RE: highest brake thermal efficiency heat engine recorded?

scania`s DTC1101 turbocompund diesel in mid-90`s has the brake effinciency 46%, todays scania`s turbocompound engines might be also somewhere there if not higher.
However, the highest brake efficiency is (was) reached by large low-speed Sulzer 2-stroke engine, uniflow scavenging, turbocharged, and it is (was) 56%.

RE: highest brake thermal efficiency heat engine recorded?

Don't shoot the messenger if you disagree. I was just checking the CO2 figure for the car (CO2 figure of 81 g/km) and noted that they gave a figure relevent to this thread.

http://motoring.excite.co.uk/display/visualizzanew...
These Volkswagen diesels are capable of converting up to 43 per cent of the thermal energy in the fuel into mechanical energy for powering the car, better than for any other liquid-fuelled production car.

RE: highest brake thermal efficiency heat engine recorded?


NickE says "I'm not sure what your asking for, but AFAIK the ultimate limit for specific HP is 2.0, thats 2.0 HP/Lb fuel/hr."

Converting that number to figures I'm familiar with gives a specific fuel consumption of 303.6 g/kWh - which is not very good. Diesels should get around 220 g/kWh and I've heard of 200 as an achievable figure. Possibly large marine low-rpm diesels can get substantially better than this.

Perhaps NickE was talking about petrol engines, which I'm not so familiar with.

In either case, there must be a limiting theoretical system efficiency assuming a 'perfect' cycle and frictionless bearings etc. I'll dig around in my old thermodynamics text books and see if I can come up with a number.

John

RE: highest brake thermal efficiency heat engine recorded?

Perhaps NickE was talking about petrol engines, which I'm not so familiar with.

Maybe more important than knowing what engine he was talking about is what fuel is he talking about.

Based on fundamentals.
I calculate the energy density of Octane to be 44,877,982 Joules/kg, not shown here.
Dividing by 3600 that's 12.466 kilowatt hours/kg
And taking reciprocals, that's 80 grams per kilowatt hour.

Based on NickE, harrisj
A pound is 0.453515 kg.
An hour is 3600 seconds.
So dividing these, a pound per hour is 0.0001259763 kg/s.
2 HP is 1491 Joules per second.

Dividing one by the other gives
11,840,748 Joules per kg or
0.000000084454 kg per Joule,
take your pick which unit you like on the top.
A Joule is a Watt for a second. Multiply the later number by 3600 seconds per hour ...
0.000304034834 kg per Watthour and move the word kilo to get
304 grams per kiloWatt hour, as harrisj said.

=================

So when NickE says "... the ultimate limit for specific HP is 2.0, thats 2.0 HP/Lb fuel/hr." we can interpret that for a particular fuel.

We can compare the 80 grams per kilowatt hour of Octane with 304 grams per kiloWatt hour embedded in NickE's statement determine that his ultimate limit would be 80/304 efficiency, or 26%.

His limit may be different. I depends on the fuel he is referring to.

RE: highest brake thermal efficiency heat engine recorded?

harrisj & crysta1c1ear - I was referring to petrol engines. wich I believe is supported from Hydroscope's post following mine. However the number I gave is from a story about the Bourke Engine in this thread:

javascript:openindex(450,350,'http://www.tipmaster.com/includes/refinfo.cfm?w=45...')

(I hope that worked) if not here is the link to the story.

http://www.niquette.com/books/sophmag/bourke.htm

and If you follow the hyperlink at the bottom of the explanation of 2.0 you get:

"Hypernote: The expression "specific horspower" (hp/lb/hr) has been adopted for the general audience in place of "specific fuel consumption" (lb/hp-hr), which is the more common technical phraseology, inasmuch as "specific fuel consumption" has been appropriated in recent times to characterize fuel economy of motor vehicles (variously gm/mi, gal/ton-mile, kg/tonne-kilometre). Typical specific fuel consumptions run about 0.5 lb/hp-hr for gasoline engines and 0.4 lb/hp-hr for Diesels." -by Paul Niquette

Nick
I love materials science!

RE: highest brake thermal efficiency heat engine recorded?

The Prius mk I uses a petrol, spark ignition, engine. Its maximum efficiency is 36%. The new model may be more efficient.

26% isn't even in the ballpark of an ultimate limit.

Cheers

Greg Locock

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