No Such Thing As A Free Lunch

[Jens]

Yeah. CO, carbon monoxide is a weak engine fuel needing special engine setting up. Lots of ignition advanve timing for it's reletivly slow even when compressed burning speed. And for longest time in cylinder to compensate for this slow burning then needing late, late exhaust valve opening best past actual BDC making cylinder purging difficult.

I have seen reference to CO being a fuel a couple of times now. Isn't it a byproduct of combustion (partial)? Is there enough energy that can be extracted by converting to CO2 that it makes it worthwhile

[Jens]

IC engines are called heat engines...because they convert heat into mechanical work. They do this by heating air...inside a cylinder. Its important to realize that the exhaust gases present inside a cylinder are what is actually being heated, BUT they have the same properties as air.

This is the aspect that gives my the most headaches. I was always under the impression that the work that is extracted is from the conversion of fuel to exhaust gases - the explosion. The reacted gases were assumed to take considerably more physical space then the pre-reaction gases and not just because of higher temperature.. Are you saying that if we take a cylinder charged with fuel, make it go 'bang while containing the gases in an expansion chamber and if we then cooled the resulting mess, the gases would fit into the same cylinder that they started out in ?
This will take some time to sink in if that is what you are saying.
Is gas expansion linear with temperature ? Does the fact that gases are heated up before the combustion takes place affect it's power output ? What happens if the cooling system runs colder, or warmer? How does compression affect the whole cycle or why is the higher compression engine more efficient ? So many questions ....

[SteveU.]

Morning All
Hey BrucePJ I think I see where you are going with your stired up energized "box o' Bees!" molecule graphic.
Goona' let you expain this so I can be certain.

Take a look at this alternative Otto-Langnen hydrogen gas fuel engine from 1868.
Shows the open ignition  flame liteing and use ;  the slider valves and valve train tripping action really well:
"Oldest running gas engine in the USA"
http://www.youtube.com/watch?v=85HkjbrA

Hi Jens.
Yes enough energy in CO2 -> CO conversion gas to usefully power IC piston engines.
Charcoal gasifier guys doing this now today from small electrical generators, riding mowers to vehicle systems now.
Not as powerful as a blended true three fuels componet woodgas.
And very difficult to make the pre-refined wood charcoal unless you are really Rural for the smoky/steamy carcoal making end of it. And have to have a cheap/free wood supply for the conversion energy loss. Or have a sensible use for the flare-off gas heat.

Regards
Steve Unruh

[cgwymp]

What happens if the cooling system runs colder, or warmer?

A bit of a different application, but Smokey Yunick (NASCAR pioneer) had this to say about engine temps and cooling systems:

"It is easy to see how overheating can be a problem, but I think some racers overlook the fact that it is possible to 'overcool' the engine. Some guys go to great lengths to keep the engine temperature down to 180 degrees. And, though the engine doesn't overheat, they don't realize that they're putting energy (heat) into the cooling system that could be used to produce power at the crankshaft. Running the engine at 180 degrees will drop the overall horsepower by 2%-3%. For max power the cooling temp should be at least 200 degrees."

The problem is that the heat will want to take the path of least resistance out of the combustion chamber. Making the engine hotter makes it "harder" for the heat to escape into the castings so more goes into producing mechanical motion.

[Ronmar]

Jens
   For the most part your statement about taking all that went in and cooling it back to original temp and it fitting back in the original space is correct.  Maybe back to the same weight would be a more correct way of putting it.  Look at what goes into the chamber.  19.2% O2 and 80.8 percent mostly nitrogen and a few other trace gasses and water.  The O2 is blended evenly with the other gasses so the fuel needs to be also for efficiency.  Once the air/fuel is ignited, the flame front spreads very quickly thru the compressed gas cloud.  Flame is a chemical reaction which consumes O2 and releases a massive ammount of heat energy as it breaks down the hydrocarbons.  This superheats the nitrogen, and the newly created(released) CO. It is that superheated gas expansion that pushes the piston down.  There are of course hydrocarbons that are not consumed and a little bit of residual O2 which also expand with the heat applied, then it all passes out thru the exhaust.  That residual O2 is how O2 sensors can be used to fine tune EFI vehicles by measuring the un-consumed O2 in the exhaust stream.  This process is why IC engines are known as Heat engines, as they capture the pressure change caused by thermal expansion.

Higher compression means more O2 is captured in the final combustion space.  More O2 means more fuel can be burnt.  Same goes for boosted applications. Charge air temperature and atmospheric pressure are also factors.  Cooler air is more dense as is lower altitude air, so a given volume of low altitude or cooler air will contain more O2 than a warmer or higher altitude air sample.   All(cold, low altitude, boosted or higher compression) put more O2 where it can release more heat energy from the fuel in the combustion chamber...   

[Jens]

So if I ran a Listeroid at let's say 300F, would I get more work out of it?
No, I wouldn't use water for cooling but a special synthetic coolant. It's been a long time since I saw details so I can't give a name of this stuff off the top of my head.

[cgwymp]

So if I ran a Listeroid at let's say 300F, would I get more work out of it?
No, I wouldn't use water for cooling but a special synthetic coolant. It's been a long time since I saw details so I can't give a name of this stuff off the top of my head.

Smokey's pet project was an "adiabatic engine" -- one without a cooling system at all. All heat was retained in the engine as much as possible except for that the produced mechanical motion. He never got all the bugs worked out.

So I'd say, "provisionally, yes." It would take some major re-engineering though to make sure everything could handle the heat....

[Dualfuel]

 I have been struggling with how to explain a concept called Heat Capacity...mostly because there are two types. The struggle has been that I don't want to take the easy way out. I have to talk about the heat capacity of a substance at constant volume...Molecules like oxygen, nitrogen (both naturally occurring as diatoms or pairs of atoms), carbon monoxide, all can store heat. The more heat is applied, the more they wiggle. Hence the cartoon. Molecules will absorb more and more heat the hotter they get. This heat is wasted to an engine because the wiggling doesn't do anything.
Another way of looking at it is that there are two types of heat, the internal heat that causes the wiggling, and changes the shape of the molecules, and then the heat that can be turned into work.
I guess the take home lesson is that in a gasoline engine with a constant volume of charge, the heat capacity varies widely as the peak flame temperature does. It varies crazily because as far as the molecules are concerned there isn't a constant volume because the piston is always moving.
In this case, the volume of charge is constant but the volume of the surroundings is changing constantly...and this means Billions of dollars testing engines to find out what is actually going on in the gasoline engine. An example of that, is a Prof down in Houghton put radio transmitters on the undersides of pistons so he could read the strength of the vibrations felt during combustion.
I am not saying there is magic, or nobody knows whats going on...but as far as putting exact numbers on such things as the heat capacity of the substances in the combustion chamber, not only are the relationships non-linear, but they require computational calculus to handle so many variables.
Thats the micro view, the macro view is much better understood.
If you look at pressures in an engine, the point after the charge is ignited is when the greatest pressure is present in the cylinder. In Ricardo's time (1915ish) peak cylinder pressure was a lot lower then in the 1960's (600to650psi) and even lower then nowadays (900 to 1000psi). Pressure is what moves the piston...if there is a 20 square inch surface on the crown of the piston then at peak cylinder pressure there is 10 tons of force moving the piston.
Heat is what caused the pressure, as the charge expands, the heat goes away, this is the work. Thermodynamics tell us that the limit of the amount of work that could possibly be done, lies in the difference in temperature between two reservoirs. In the cylinder's case, the "hot" reservoir is the point in time, in the cylinder, when the peak pressure is present. The "cold" reservoir is the time in the cylinder when the exhaust valve opens...to atmospheric pressure. So the limit of the efficiency of the engine can be found by percentage of difference between the two pressures...except we never expand the piston down a long enough cylinder to be able to lower the pressure to atmospheric.
To add to the fun, remember that mechanically speaking, the piston has to accelerate away from the charge like crazy til its half way down the cylinder, then it has to decelerate like crazy to be able to stop a BDC.
So in Ricardo's time 450psi was the peak cylinder pressure, and the resulting limit to efficiency was 47%. Those days, they didn't have tetra ethyl lead to stop detonation, so their compression ratios were low. 5:1 was pretty high. So if they couldn't raise the compression ratio to raise the peak cylinder pressure, they used long piston strokes to expand the burning charge to as low a pressure as they could before letting it leave the cylinder. This increased actual efficiency closer to the 47% limit.
The thing about long strokes is piston speed and acceleration. If the piston has to go a longer distance down the cylinder, then the acceleration and deceleration must be even greater. This insane acceleration quickly reaches the mechanical limits of cast iron pistons.
In order to survive, the long stroke engines didn't turn at very high rpm.
(Jens, I will leave it there and go into your questions next time) BPJ, or DF if you like...

[Dualfuel]

Is gas expansion linear with temperature ? no...and a graph of pressure during combustion shows this...

Does the fact that gases are heated up before the combustion takes place affect it's power output ? Yes, it brings the charge, that much closer to the temperature required to ignite or flash. The problem is that being so close to ignition, the charge may accidently ignite, from some other hot object in the cylinder.
  What happens if the cooling system runs colder, or warmer? So far I have only been talking about conditions inside a spark ignition engine burning premium gasoline....I still am too. There is a boundary layer between the charge and the metal walls of the cylinder. This layer is where the combustion stops. If the cylinder walls are cool, the layer is larger, and if its warm, the layer is smaller.

How does compression affect the whole cycle or why is the higher compression engine more efficient ? http://www.youtube.com/watch?v=vjqIJW_Qr3c
This video shows a chain reaction. This takes place in a container. In the video you can see that the mouse traps are very close together. This would be the condition when the charge is close together...The nitrogen in the mixture damps out the fire, by shoving the oxygen and hydrocarbons close together they can "conduct" the heat from reacted gases to unreacted gases.
Another crazy problem is that there are left over burnt gases still in the cylinder, after the exhaust stroke. So you have nitrogen from the incoming charge, CO2, H2O, and the nitrogen from the old charge, all still present in the cylinder when the fresh charge is ignited. This would cause layering or stratification in the long stroke, slow turning engines. This is why they worked so hard to make "swirl" combustion chambers, and T-heads (think old Gravely Engines). Compression helps produce turbulent flow. Turbulence gets rid of exhaust gas stratification.
The math part of compression, shows us that everything else becomes equal and the  actual upper limit of engine efficiency can be found in the difference between peak cylinder pressure, and exhaust pressure. These pressures are determined by compression ratio.

[Dualfuel]

Ok, I have been going on and on, about Constant Volume, spark ignition, and heat capacity. Here is why, the modern gasoline engine, lets say a Kubota 5hp OHV four stroke generator engine....is NOT a constant volume engine. It is throttle governed. This means, the engine slows down because a butterfly closes and restricts the flow of air/fuel into the cylinder. Well....here we go...with less fuel and air in the cylinder, there is still the same volume for it to fill but less of it so it spreads out. This slows the flame speed, lowers the effective compression ratio, and lowers peak cylinder pressure...closing the throttle radically changes the engine's characteristics.
The engineering challenge that has been met by the Japanese is to keep the engine efficiency high regardless of the size of the charge in the cylinder.
Brake Specific Fuel Consumption....this is the macro way of testing an engine's fuel efficiency. When we step away from the Ivory Tower, into the real world, all we are concerned with is BSFC. It is measured in pounds of fuel per horsepower per hour.

pounds/(hp X hour)

Usually the graph of this measurement is a parabolic looking curve...the engineering challenge is to flatten out that curve. We want our engine to use just as little fuel per horsepower at idle as it does at top RPM.
So what happens is, the engineers get more and more intricate trying to build engines that have that flat BSFC curve. We went from cheap T or F head cast Iron engines to variable valve timing, over head valve, fuel injected, etc. etc.
But wait there's more....
They pulled some real crap on us...they made these very special engines with exotic materiel, and carefully designed combustion characteristics...all built around the idea of one kind of fuel...gasoline but then they changed the fuel...and have been changing the fuel since the twenties...
with the introduction of Tetra Ethyl Lead, we were able to get away from low compression long stroke engines and go to high compression, high revving engines...gasoline was cheap, so was lead, so all that remained was to build giant displacement engines out of cheap components, and dump gasoline into them. Lots of power, done cheaply.
Then gasoline got expensive, and lead was outlawed....so they switched to methyl tertiary butyl ether as an anti-detonation additive, and mixed it with low octane "cheap" gasoline.
Whoops! MBTE leaks from gas storage tanks and contaminates ground water, so they outlawed that and simply added ethanol to cheap gasoline.
Each change in the fuel supply requires a different specialized engine. There cannot be a one size fits all, that has high efficiency. If you wonder why your lawnmower from the 1970s has died, its because it was never designed to burn the non-gas they sell now. If you wonder why your truck costs $50000, its because it needs more computer power to keep it running then the Saturn V rocket needed to get to the moon. All, this because the fuel keeps changing, and these engines are designed around one very specific type of fuel.
I know this is sort of a rant, but the point is, things are very complex over in the spark ignition side of internal combustion, and it helps tremendously to go back and study the very basics in order to be able to plan ahead for the next fuel change. Despite the complexity, spark ignition has some real advantages...especially here in the north...they start in the winter. They are also still relatively plentiful, often times free. All they want, is fuel, lots of fuel.

Next I want to step into the realm of Constant Pressure engines....a much nicer place....

[SteveU.]

Morning All
Very good so far.
That "box of bees" when whanged on with a stick get very energized indeed. Make one side of the box movable and we could get power from their randomized trying to fly out, apart. Only on one this one side though. Their randomized flying movements against the other sides is wasted energy.
Same number of bees as in the original dense quiet handful.
Want more immediate power? Bang the box harder.
The moving box side will at some point have to be re-set.
Best to then to expell out all of the old tired bees and put in a handfiul of new ones at this re-set point. Ha! Never can quite get all of the old bees out. Helps to squeeze the space down with the movable box side. The more bees put in the more force to make power. Until then too bee "Rich" and they then have no room to fly apart.
Want more power yet? Use a more energetic breed of bees like hornets or wasps!
Want even more power yet?? Cycle change them out for fresh ones more frequently.

Yes I read and followed Smokey Yunicks engine developements. On his adiabatic engine he was trying to use precision silicon carbide castings for the heat resistance, smoothness and hopefully self lubricating capabilities. Problem as I undertand it these silicon carbide parts could not with stand the variable high freqency shock loadings (BPJ's Micro effects) in a piston IC engine. Same problem that the Japanese Kyrocera Company ran into locally here much later trying to break into the auto parts market with precision ceramic castings.

Yeah. As IC piston engine developement has gotton much better and advanced the actual engines are more and more particular about the actual fuel characteristics.
Why the old, old like the CS Listers have shown the great alternative fuels capabilitites.
My two different still relitively simple single cylinder OHC Honda four stroke lawn mowers; and ALL of my post 2005 2-stroke Stihl chain saws are real picky now about gasoline grades, and whether "clear" non-alcohol or a modern "clean air" "reformulated" swamp fuel. Big noticeable difference on these small ones in ueable power and overheating.

Another reality in the purist engine soup is that the in cylinder pressure changes because actual combustion is a time drawn out process; NOT an instantanous BOOM. And this temperature/pressure build up and decrease is greatly affected by the changing in-cylinder volumn rate. That volumn change rate is related to the piston to connecting rod length ratio and crankshaft throw stroke versus TIME (rpm). Adult power Bicycling and firearms cartridge handloading optimizing have taught me as much about these relationships rates changes as actual engines useage and rebuilding.
At a certain point with many fuels before the piston reaches the bottom the combustion fire will go out. Fuel starved "lean" to prevent fuel wastage and you will have less heat and power - need to engine diaspacement oversize for actual net power needs. Intentionally over fueled to keep the in-cylinder heat and pressure UP as long and high as posible and than you waste fuel with unconverted pressure spewed out the exhaust port. That wonderful smell and sound race followers love.
All gets complicated fast. NO free lunches with engine/fuel dynamics  - just lots of "Eat your lunch as served, and shut up!" compromises.

And now that emissions standards are set around the evolving very high now IC piston engine capabilities it makes it even more remote any other engine type could reach legal commercial developement and deployment. THIS is why GM wisely pulled the plug on thier 70's Wankle leaving thier own Monza and AMC's Pacer caes engineless with then stuffed in piston substitutes. Non-compeditive Wankle emmisions/fuel ecomomy IS what damn near killed off late 70's Mazda. Did kill off NSU. Weakened AMC for eventual French buyout by Renault.
Never put all your eggs in one basket! Spread out the risks. Always have a Plan B. Falling back on Plan B you then no longer have any backup! Just one step then from failure. Have a tentative Plan C without a lot invested ready to move up to be a new PlanB.
Edison always concurrently developed 2-3 ideas simultaneously never quite sure which would actually make it to produce the results he wanted.

Regards
Steve Unruh

[Dualfuel]

Ok, I will turn the corner on this... up to now I have been describing a cylinder that gets filled with an flammable mixture, sealed up, and then the mixture gets ignited, forcing the piston down...This mixture burns very fast, in fact, most of the engineering has gone into keeping the mixture from igniting until it is supposed to. Then once it is burning, keeping its flame speed down low enough to simply keep it from exploding all at once.
The other way of doing things is using a constant pressure approach to things...on the physical chemistry side of things, micro level, most of all experiments are performed under constant pressure, namely that being atmospheric pressure or 14.7 psi at sea level. So from the beginning there has be excellent data about the heat capacity of air under constant pressure. It turns out to be more then that of air at a constant volume. Also constant pressure  has been understood by engineers because of steam engineering.
Constant Pressure engines fill a cylinder with air only and then compress it. The volume of air in the cylinder contains a certain quantity of heat. The temperature of the air in the cylinder before it is compressed reflects its surroundings or you could say it was room temperature. When all the uncompressed volume of air is forced into a very small space it concentrates the heat, and with no where to go, the heat raises the air's temperature. Rudolph Diesel, thought to compress the air far enough that its temperature would be above the flash point of the fuel to be burned in the cylinder. His system used compressed air to blow or inject oil into the cylinder during the time the air was compressed and hot.
The fuel droplets ignite immediately but burn in a uniform pattern, producing a pressure wave that forces the piston down...just like a gasoline engine, only there is more! The injector keeps injecting fuel and keeps the burning going, and even though the piston is moving down, and the volume expanding, the cylinder pressure remains fairly constant. The fuel spray is eventually cut off, and the pressure falls off as the piston expands until BDC, and the opening of he exhaust valve.

[Dualfuel]

I know this sort of baiting you guys...but why would you pick an engine that isn't made in America, doesn't have parts available at Carquest, and weighs a billion pounds? What advantage would there possibly be in owning a Lister or a Listeroid?
They are nothing I would want, for the above reasons, but from a thermodynamic stand point I can see some fantastic reasons for wanting them...
BPJ

[LowGear]

I know this sort of baiting you guys...but why would you pick an engine that isn't made in America, doesn't have parts available at Carquest, and weighs a billion pounds? What advantage would there possibly be in owning a Lister or a Listeroid?

Open your ears and think with your heart.

Stop surviving and start living.

There's four.

Casey

[quinnf]

I think it has something to do with the sound they make and the way the ground trembles when you stand next to one.  And the smell of diesel smoke.  That's what does it for me.

q.