Diesels at high and low altitudes..

[bx23barry]

<The Power Bar (made from apple cores and waste newspaper) I ate at the bottom would be what propels me to the top of Mt. Whitney, not oxygen.>

O2 is what turns that power bar into useable energy.

<Where is it stated that that is the case with a diesel engine?>

Doesn’t matter. It is true with all internal combustion engines, but I was indeed referring to diesel engines.

<The amount of fuel injected is chosen by many factors engine durability being probably the foremost one.>

Yes but I am talking about maximum power.

<MUCH more power can be extracted from a diesel engine by simply adding more fuel. To illustrate this point, look at the immense columns of black smoke coming from a pulling tractor by simply injecting more fuel, you can see that for a normal diesel engine, the maximum amount of fuel is not being injected. In some cases, they even inject additional fuel (propane) into the intake air. How is it that this propane burns if all the available oxygen is already consumed? More fuel could not be added if there wasn't sufficient oxygen for it to burn.>

My point exactly, to produce maximum power all the available o2 must be ignited.

<As I have illustrated above, normal diesels do not fuel enough to produce maximum power at sea level because we want them to last a while.>

Ok so you are not talking about maximum power. A "lean" "normal" diesel may indeed not lose so much as a gas engine at slightly lower elevations but would lose power at all altitude because of lower effective compression ratio caused by the less air density. At some point it wouldn’t even run because there wouldn’t be enough heat generated from compression to ignite the fuel (why non-aspirated diesels don’t fly so well). "Lean" "normal" diesels do in fact lose power at altitude if you want to prove it just find some real mountains to take your diesel over.

 

[SkyPup]

--Although the amount of oxygen is reduced, there was a surplus to begin with. One would have to climb to an altitude of 20,000 feet just to get the diesel down in the lean range of the gas engine. So...same amount of fuel went in, enough oxygen is there to meet with it, and contrary to Skypup's assertion that there isn't enough time, there is--diesels typically have very long rods in proportion to the stroke of the engine which produces a longer time at TDC than a short-rod gas engine.

Nope, there isn't enough time or air available at 20,000 feet for a diesel engine to run the same as it does at sealevel.

Just get a fundamental diesel combustion engineering book at your local University mechanical engineering school and read it. Your hypothesis about diesel's high altitude operation would not pass Diesel Combustion 101......

 

[KICK]

this whole thread leads me to believe

you cant have it both ways.

 

[SkyPup]

Ok so you are not talking about maximum power. A "lean" "normal" diesel may indeed not lose so much as a gas engine at slightly lower elevations but would lose power at all altitude because of lower effective compression ratio caused by the less air density. At some point it wouldn’t even run because there wouldn’t be enough heat generated from compression to ignite the fuel (why non-aspirated diesels don’t fly so well). "Lean" "normal" diesels do in fact lose power at altitude if you want to prove it just find some real mountains to take your diesel over.

Yes, even turbocharged diesel engines lose power at high altitudes for the exact same reason...

 

[SkyPup]

As I have illustrated above, normal diesels do not fuel enough to produce maximum power at sea level because we want them to last a while.

Come on, you've got to be kidding us?

"Normal" diesels do not fuel enough to produce maximum power at sealevel because we want them to last for awhile?"

So, when we operate them at higher elevations than sealevel we want them to last even shorter than they should????

 

[SkyPup]

At Bonneville, I had to change out my fuel injector nozzles from 0.205 microns down to 0.150 microns due to excessive smoke, high EGT and lower power.

At sealevel the 0.205 micron nozzles put out lots more power and torque, plus the EGT is no problem.

Can't run that much fuel at Bonneville though or it would burn a hole through the piston from raw fuel being sprayed on it due to not enough air to mix with the fuel......

The reason our EGT was too high at this 5,000 foot elevation was due to not enough air to combust the diesel fuel that was being injected into the combustion chamber, even after decreasing the amount of fuel per injection event into the combustion chamber by 25%, there was still too much fuel for the available barometric air pressure to burn. Excessive EGTs are due to a rich air/fuel mixture, which is caused by too much fuel.

The High EGT is caused by unburned diesel fuel burning outside the combustion chamber post compression as it is evacuated on into the exhaust manifold......

The simple fact is that high altitude causes high EGT due to not enough air and unburnt fuel escaping the combustion chamber.

 

[orezok]

Your statement about EGT being high is because the"excess" fuel is being burned outside the combustion chamber. Are you saying that fuel burns hotter in the exhaust manifold in a lower pressure condition than in the combustion chamber under high compression? While it's true that a gas will cool somewhat when transitioning from high pressure to low pressure, there should not be a significant difference.

 

[SkyPup]

No, I'm saying the fact is that the fuel is still burning IN the exhaust manifold after NOT being consumed inside the combustion chamber.

That is what causes the EGT probe to register the increase in extreme heat from the excessive overfueling at higher elevations in the diesel engine due to a lack of sufficent air inside the combustion chamber.

 

[orezok]

Well if there is not sufficient air (oxygen) for the fuel to burn in the combustion chamber, just exactly does it get the air to burn in the exhaust manifold? There would have to be excess air available after the power stroke to continue combustion in the manifold.

 

[SkyPup]

You'll simply have to go back and re-read the previous information presented here if you cannot understand why the EGT in a diesel engine under load increases to dangerous levels at high altitudes.


Hint -> TIME.........