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Old 02-07-2013, 06:11 AM   #761
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Isnt that the same thing you said?
No.

A diesel engine only injects the amount of fuel required to produce the power it is tasked to deliver.

At idle or low power there is very little fuel injected and the huge majority of the cylinder volume never sees fuel at all. Diesel engines do not have a homogenous mixture or burn like a spark ignition (SI) engine.

The plume of injected fuel begins to burn at the points where the fuel droplets are small enough to heat the quickest and have enough oxygen available ... that condition described the outer edges of the plume. The center is almost free of oxygen and is relatively cold. The volume outside the plume has no fuel so there is nothing to burn.

With regard to smoke at high loads, it results from an excess of fuel for the amount of oxygen available to burn it. Semantically, you could say it is an over-rich mixture but since there is not a homogenous mixture of fuel and air across which a flame front moves but is relatively narrow plume of fuel with distinct areas of combustion surrounding or surrounded by areas where the fuel is "baked" into little bits of carbon called soot, it does not smoke from a "rich mixture." That is an unfortunate bit of shorthand for a very complex set of combustion chamber conditions.

Since every kid grew up knowing everything about gasoline engines, when they grew up and bought a diesel they try to explain or understand diesels from the same point of view and it doesn't work that way.

Getting back to your comments about diesel fuel being a cylinder lubricant, if the injector plume ever reaches the piston or cylinder wall it is a major problem. It should never ever happen. If unburned fuel remains to coat the cylinder wall or piston crown it is a major problem. All the fuel should be burned without contact with the cylinder walls or piston.

You guys need to just forget this "mixture" thing when you are talking about diesels. It just confuses things for the members who are contributing more myth and nonsense to the thread.

I don't want to come across like Marin in the Boeing ignorance posts but I am beginning to understand why he wrote what he did.
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Old 02-07-2013, 06:16 AM   #762
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I think his numbers are incorrect. Life support would have to include energy used to run the main engines since without them there is no life support. If he is referring to creature comforts his 30% may be correct. 70% for engine systems friction drag losses and actual prop
HP may even be in the ball park. Interesting thought. thanks

Oh Lard tunderin' Jayzuz Jarge! Talk about the blind leading the blind!

"engine systems friction drag losses"

Please take this conversation offline or something, it makes me queasy.
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Old 02-07-2013, 06:42 AM   #763
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Never mind Rick. Just have a quick coffee and a lie down, and all will be well. Some of us are indeed learning new things. They say you learn a new thing every day if you open your ming to it. I found that explanation re how diesel burns, as compared to a sparked ignition with petrol, (our word for gas - but you knew that), very interesting. I knew there was quite a lot of difference, but not that much...explains a lot.
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Old 02-07-2013, 11:03 AM   #764
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So from an annual perspective, the cost difference between operating one engine or two is pretty insignificant as I described earlier.
And that is more than offset by the pleasure of operating twins over singles. The maneuverability, peace of mind and reduced load on the engines is significant to justify them in my mind. Plus resale will hold up better as some point as well.
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Old 02-07-2013, 11:17 AM   #765
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Old 02-07-2013, 01:43 PM   #766
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Old 02-07-2013, 01:49 PM   #767
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Old 02-07-2013, 03:11 PM   #768
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Old 02-07-2013, 04:58 PM   #769
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No.

A diesel engine only injects the amount of fuel required to produce the power it is tasked to deliver.

At idle or low power there is very little fuel injected and the huge majority of the cylinder volume never sees fuel at all. Diesel engines do not have a homogenous mixture or burn like a spark ignition (SI) engine.

The plume of injected fuel begins to burn at the points where the fuel droplets are small enough to heat the quickest and have enough oxygen available ... that condition described the outer edges of the plume. The center is almost free of oxygen and is relatively cold. The volume outside the plume has no fuel so there is nothing to burn.

With regard to smoke at high loads, it results from an excess of fuel for the amount of oxygen available to burn it. Semantically, you could say it is an over-rich mixture but since there is not a homogenous mixture of fuel and air across which a flame front moves but is relatively narrow plume of fuel with distinct areas of combustion surrounding or surrounded by areas where the fuel is "baked" into little bits of carbon called soot, it does not smoke from a "rich mixture." That is an unfortunate bit of shorthand for a very complex set of combustion chamber conditions.

Since every kid grew up knowing everything about gasoline engines, when they grew up and bought a diesel they try to explain or understand diesels from the same point of view and it doesn't work that way.

Getting back to your comments about diesel fuel being a cylinder lubricant, if the injector plume ever reaches the piston or cylinder wall it is a major problem. It should never ever happen. If unburned fuel remains to coat the cylinder wall or piston crown it is a major problem. All the fuel should be burned without contact with the cylinder walls or piston.

You guys need to just forget this "mixture" thing when you are talking about diesels. It just confuses things for the members who are contributing more myth and nonsense to the thread.

I don't want to come across like Marin in the Boeing ignorance posts but I am beginning to understand why he wrote what he did.
Did I say cylinder lubricant? I think I said that diesel fuel is not only a fuel but acts as a lubricant inside the engine. Dosen't the fuel act as a lubricant for the injectors and some valve train components? If this were not so people would not have experianced engine failures due to the decrease in the lubricity of the reformulated diesel fuel a few years ago. Thats when i began to use an additive and have never stopped. Modern fuel has additives to increase the lubricity in some qareas by the mixing of bio D.
Now correct me if I'm wrong, I'm learning, well attempting to anyway. A diesel engine is really just a pump and each stroke it will result in the intake of the same cylinder volume. Since each stroke will result in the same intake volume how exactly does the throttle work?
Hey Rick, thanks for taking thr time to give us a detailed explanation it helps jog my memory to better understand whats going on
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Old 02-07-2013, 05:35 PM   #770
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Older jerk injection pumps like the CAV/Minemec/Simms pump on the FL120 use the fuel they are pumping to lube the plungers in their bores and also the moving parts in the injectors. I don't know the role of fuel lubricity in more modern injection systems.
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Old 02-07-2013, 07:19 PM   #771
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Did I say cylinder lubricant? I think I said that diesel fuel is not only a fuel but acts as a lubricant inside the engine.
Yes you did, post # 744:

"If the mixture is lean the result is less hp and more engine wear due to lack of lubrication."


Quote:
Dosen't the fuel act as a lubricant for the injectors and some valve train components?
Only in the injection system. Why do you think it lubricates "some" of the valve train?


Quote:
Now correct me if I'm wrong, I'm learning, well attempting to anyway. A diesel engine is really just a pump and each stroke it will result in the intake of the same cylinder volume. Since each stroke will result in the same intake volume how exactly does the throttle work?
Keep learning but stop posting nonsense as if you knew what it meant or was true.

The "throttle" on a mechanically injected diesel (with a very few exceptions) is merely a lever connected to a another lever that applies or removes spring tension from a component of the governor that converts centrifugal force into mechanical motion that in turn controls the amount of fuel injected.

On an electronic diesel, it changes a setpoint in the feedback loop that measures and adjusts rpm.
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Old 02-07-2013, 07:46 PM   #772
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Rick wrote;

"The "throttle" on a mechanically injected diesel (with a very few exceptions) is merely a lever connected to a another lever that applies or removes spring tension from a component of the governor that converts centrifugal force into mechanical motion that in turn controls the amount of fuel injected."

So it's a fuel Limiter? Limiting the amount of fuel that can be injected at a given rpm? And the spring limits the fuel even down to very low loads including idle where the load is only the friction of the engine? The governor seems to be the secret of the system.
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Old 02-07-2013, 07:48 PM   #773
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i made a mistake then. I thank you for pointing that out. Sometimes i get in a hurry and i just write without properly reveiwing my work.

<<If the mixture is lean the result is less hp and more engine wear due to lack of lubrication.">>

Rick, big time error thank you sir.

<<On an electronic diesel, it changes a setpoint in the feedback loop that measures and adjusts rpm.>>
Go on Rick I am listening. I understand the old tractor diesel controls but not the new systems. I assume you are referring to a charactoristic cure that is programmed in the cpu which is used to control fuel volume in relation to engine rpm?
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Old 02-07-2013, 08:06 PM   #774
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<<Keep learning but stop posting nonsense as if you knew what it meant or was true. >>
....maybe someday i will know everything. You my friend have also have made nonsensical typos during this exchange which have been pointed out during this conversation. as stated I am appreciative of your corrections
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Old 02-07-2013, 08:14 PM   #775
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So it's a fuel Limiter? Limiting the amount of fuel that can be injected at a given rpm? And the spring limits the fuel even down to very low loads including idle where the load is only the friction of the engine? The governor seems to be the secret of the system.
Be careful using the term "limiter" as that has a very specific meaning in terms of engine control. For instance a "start fuel limiter" controls the amount of fuel delivered during start to avoid smoke and an overspeed. Your mechanical governor is at "full throttle" when the engine is at rest and when it is started.

Look up flyball governor, there are some outstanding descriptions of how they work. Unless you have an electronic engine, you have a good old fashioned flyball whirling around at the end of your fuel injection pump.

And yes, the governor is the heart and brains of the outfit.
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Old 02-07-2013, 08:18 PM   #776
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That's still an irrelevant statistic because when the one engine fails in a single you're through boating for the rest of the day other than as a barge on the end of a line. And while the odds of the one engine in your boat failing are exactly the same as the odds of either of the two engines in a twin failing, the odds of you being left adrift and hoping that a tow arrives in time are almost infinitely greater than the odds of a fellow with a twin engine boat who experiences a failure of one of his engines being left adrift and hoping that a tow arrives.

So the real question is, do you want to be left adrift when an engine has to be shut down or do you want to keep going when an engine has to be shut down? That's the only question worth asking as far as I'm concerned.
Marin, you are forgetting that there are DeFevers out there with electric get home motors..........would those technically be twins?
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Old 02-07-2013, 08:23 PM   #777
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Be careful using the term "limiter" as that has a very specific meaning in terms of engine control. For instance a "start fuel limiter" controls the amount of fuel delivered during start to avoid smoke and an overspeed. Your mechanical governor is at "full throttle" when the engine is at rest and when it is started.

Look up flyball governor, there are some outstanding descriptions of how they work. Unless you have an electronic engine, you have a good old fashioned flyball whirling around at the end of your fuel injection pump.

And yes, the governor is the heart and brains of the outfit.
Hey Rick, what do you think of the four piston eight cylinder direct injection engines that will soon be powering helicopters?..some kind of configuration like that. anyway the piston fires both ways acting like two cylinders. I read of this design a while back
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Old 02-07-2013, 09:25 PM   #778
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Hey Rick, what do you think of the four piston eight cylinder direct injection engines that will soon be powering helicopters?..some kind of configuration like that. anyway the piston fires both ways acting like two cylinders. I read of this design a while back
I'll have to look that up. Sounds interesting. I used to work on 8 cylinder, 16 piston diesel engines. Rick probably did too, if I recall his background correctly.
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Old 02-07-2013, 10:15 PM   #779
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Didn't ALCO diesel engines of WWII era (used in both submarines and railroad locomotives) fire both (up and down) ways? Those were rather tall engines.
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Old 02-07-2013, 10:20 PM   #780
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The opposed pistons in a single cylinder is something Fairbanks-Morse perfected prior to WWII as it was the diesel that was used in a lot of our submarines and later in F-M railroad locomotives. I'd not heard of a single piston moving back and forth in a cylinder with a combustion chamber at each end, however. How does the piston connect to something to transmit the power it generates to something that turns?
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