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Discussion Starter #1
Hi again everyone-

I decided to get all my pesky questions out today. This one is general:

I understand about a lean fuel to air ratio making the engine run hot and increasing the NOx output. What I have never understood is why decreasing the amount of fuel/air/combustion cycle makes an engine hot. It seems like less fuel would make smaller explosions > less heat > cooler running engine.

Humbly submitted for your entertainment.
 

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Well my memory didn't serve me farther then remembering the book to look the facts up in.

From:

Motorcycle Tuning for Performance, by Carl Shipman Copyright 1973

"The reason power is reduced" (my note: And therefore temperature) "is a complexity. The chemical reaction between gasoline and air requires some elevated temperature to start it, after which it should generate enough heat to maintain the burning process.

Combustion moves outward from the point of origin (the spark plug) just like a grass fire spreads from the burning match that started it. Each part of the periphery of the flame front raises the temperature of the adjacent fuel to the combustion temperature. If the grass is green, wet or not present, it won't burn.

Similarly, if there are an overabundance of fuel (gasoline) molecules in the combustion space, they tend to insulate one set of burning fuel-air molecules from the next set and prevent the transfer of heat outwards to unburned mixture. This leads to unburned" (My note: un-used) "pockets of the air and possibly pockets of mixture that never burn at all.

There are other factors. The vaporization of excess droplets of fuel tends to cool down the entire combustion volume, reducing the effective pressure. The fuel vapor exerts part of the total pressure in the cylinder, during induction, reducing the pressure which the air can attain, and thus the weight of air in the cylinder." (My note: reduces the overall amount of fuel air charge, read heat potential)

"The net effect is that power" (My note: and therefore heat potential) "is reduced when the mixture is made rich..."

"Major internal cooling results from evaporation of the fuel droplets..."

Just remember _YOU_ asked. <VBG>

HTH! :)
 

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Discussion Starter #3
Hi John-

I appreciate you looking it up for me, and relaying this complex process.

In the explanation you sight it seems to me that the key is the line: "Major internal cooling results from evaporation of the fuel droplets..."
Paragraph #3 uses the word “overabundance” and paragraph #4 uses the word “excess” so to me they seem to be describing why an overly rich mixture would not produce as much power (heat) as a properly balanced mixture.

Thanks again!
 

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Hmm, that sounds fishy to me. To my knowledge, a slightly rich mixture generates more power than an "ideal" mixture, so long as it's not gone overboard.
 

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You are correct Foxpaw. There is an ideal ratio for maximum power around 12:1, different from the chemically correct ratio of 14.7:1. And to mix it all up the Insight by virtue of its stratified charge runs as lean as 24:1 without the detrimental effects that a normal internal combustion engine would suffer.

And all gasoline internal combustion engines require different ratios depending engine temperature, load, & speed. One reflection as to why the lean burn window feels so small.

Poor Dan, I can hear him struggling now. <VBG>
 
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Hi Insightful Trekker:
Insightful Trekker said:
Poor Dan, I can hear him struggling now. <VBG>
___Good god man, poor the rest of us as well :D

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:5bl3zup1][email protected][/email:5bl3zup1]
 

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Discussion Starter #8
Hi all-

As so often in life, I was looking for a simple answer to a complex problem. Now that I have learned a little more I see:
-The error of my ways
-The path to greater enlightenment (the library)
-The inappropriateness of using a lot of space here in pursuit of an answer only peripherally related to Insights.

I will restrain myself from inquiring upon the reaction sequence of a fast breeder reactor :roll:
 
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Hi Dan:
dan said:
I will restrain myself from inquiring upon the reaction sequence of a fast breeder reactor :roll:
___Would you like to instead hear about the internal workings of a Graphite Moderated RBMK like that used in Chernobyl’s Unit 4 back in April of 1986 ;)

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:2cyjcvm9][email protected][/email:2cyjcvm9]
 

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Discussion Starter #10
Hi xcel-

Only if you can explain it to me in Russian. :lol:
 

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Hi xcel-

That would be perfect! Although my vocabulary is restricted to those words used by the Beetles in “Back in the USSR”. I’m sure you are up to it. :wink:
 

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To Dan;

Humbly and humorously stated! How much better can a NG get. You made my effort worth the while. :)

To xcel;

I knew better than to ask you anything about nuclear power generation. <g> But I did have a neighbor that worked on the fast breeder reactor project back in the 80's. :)
 

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Ahem...

Ядро стало очень горячим и начатым, чтобы таять здание сдерживания. Люди убежали очень быстро! эй обещанный никогда снова вещи, которым позволяют, пока не выходят из-под контроля.

:roll:

Okay, okay, here it what it (roughly) means:

The core became very hot and started to melt the containment building. People ran away very fast! They promised to never again let things get so far out of control.

:lol:
 

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Actually, Chernobyl did not have containment. Now, let's try to contain this thread and stay on topic.
 
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Hi Tim:

___And Chernobyl’s Graphite moderated core had a huge positive reactivity addition with any amount of steam voiding in the HP coolant channels, positive reactivity added on initial rod insertion, and an unstable core below 20% thermal. You wouldn’t believe me if I told you what else was going on with that reactor and safety systems to protect it.

___The US Army’s experiments with nuclear power were pulled for a similar reason when they stuck a guy to the ceiling of a reactor building with a rod that blew out of a experimental core a long long time ago … They had guys manually manipulating rods by hand way back when!

___We were talking about the Insight, right?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:3fialq82][email protected][/email:3fialq82]
 
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