highest brake thermal efficiency heat engine recorded?

[HydroScope]

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

 

[NickE]

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.

 

[HydroScope]

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??

 

[NickE]

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

 

[ivymike]

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)?

 

[SBBlue]

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

 

[enginebob]

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.

 

[HydroScope]

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/

 

[ivymike]

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

 

[ivymike]

"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)

 

[dcasto]

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.

 

[HydroScope]

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

 

[Warpspeed]

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

Lbs/hour of food to mechanical work hehehe.

 

[GregLocock]

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

 

[ivymike]

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...

 

[patprimmer]

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.

 

[GregLocock]

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

 

[HydroScope]

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.

 

[Warpspeed]

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.

 

[ivymike]

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