fuels

[pasoleati]

The following is an interesting commentary by Samuel Heron from his book Development of Aviations Fuels:"It will be noted that in these mild engines the rich PN becomes the lean PN and as a matter of fact, in such engines rich mixture ceases to be of any use as a means of increasing knock limited power output. Whili rich mixture ceases to be of value in regard to increasing knock limited power in mild engines, it nevertheless may have to be employed even at a sacrifice of power in order to make the engines cool satisfactorily. Mild engines have been discussed in terms of the liquid cooled type. It appears that mildness is not confined to liquid cooled engines and that mild air cooled engines can be built if necessary although this will result in increased mechanical complexity. If milder engines had been generally available during the war [Heron must mean US situation, PL] , octanes such as alkylate might have been less important since cat cracked gasoline of about 90/130 PN could have given the same engine performance as Grade 100/130 did in the more severe engines."

[KG45]

fascinating!

[Wolfala]

Can someone translate this back into english for the non mechanical types

[hitech]

Ok I give: what is a "Milder Engine".

HiTech

[dedalos]

What?????

[Captain Virgil Hilts]

I read that. I know I read that. I read it 4 times. Having made  high performance internal combustion engines, inlcuding aircraft engines, a major focus of my life for around 30 years, I understood none of it. To quote Steve Martin:" What the Hell is that?"

I want my eyes back, and I want to be compensated for this headache and the lost time.

[Captain Virgil Hilts]

Originally posted by Wolfala
Can someone translate this back into english for the non mechanical types

To be fair, I'd be willing to bet this was "translated" into English from another language.

The language is not "mechanical" or "technical", at least not like anything I've read before, especially SAE or FAA papers for example.

[Wolfala]

Originally posted by Captain Virgil Hilts
To be fair, I'd be willing to bet this was "translated" into English from another language.

The language is not "mechanical" or "technical", at least not like anything I've read before, especially SAE or FAA papers for example.

I think Luis Black said it best when "Only taking LSD could prepare me for what I had just heard."

[joeblogs]

I have read this book before, and I have a pdf copy. I can't find a rererence to mild engines. I can find a reference to sensitive and insensitive fuels. How about a page number?

I am going to take a guess though. I think this is a passage referring to hot spots in engine cylinders...

-Blogs

Originally posted by pasoleati
The following is an interesting commentary by Samuel Heron from his book Development of Aviations Fuels:"It will be noted that in these mild engines the rich PN becomes the lean PN and as a matter of fact, in such engines rich mixture ceases to be of any use as a means of increasing knock limited power output. Whili rich mixture ceases to be of value in regard to increasing knock limited power in mild engines, it nevertheless may have to be employed even at a sacrifice of power in order to make the engines cool satisfactorily. Mild engines have been discussed in terms of the liquid cooled type. It appears that mildness is not confined to liquid cooled engines and that mild air cooled engines can be built if necessary although this will result in increased mechanical complexity. If milder engines had been generally available during the war [Heron must mean US situation, PL] , octanes such as alkylate might have been less important since cat cracked gasoline of about 90/130 PN could have given the same engine performance as Grade 100/130 did in the more severe engines."

[pasoleati]

The quote is from the end of Chapter 8 under the subheading "Effect of Engine Design on Performance at Lean Mixtures. Canīt give a page number for my my copy is a print out from and old scan on diskettes.

And it is no translation as suggested by some. Sam Heron was a native English speaker born in the UK. He is the fellow who developed sodium cooled valves.

[joeblogs]

I am traveling at the moment, but will take a look at my copy as soon as I am home.

Based on the title, I do lean to the cylinder hot spot theory I mentioned before.

- Bob

Originally posted by pasoleati
The quote is from the end of Chapter 8 under the subheading "Effect of Engine Design on Performance at Lean Mixtures. Canīt give a page number for my my copy is a print out from and old scan on diskettes.

And it is no translation as suggested by some. Sam Heron was a native English speaker born in the UK. He is the fellow who developed sodium cooled valves.

[Wolfala]

Originally posted by pasoleati
The quote is from the end of Chapter 8 under the subheading "Effect of Engine Design on Performance at Lean Mixtures. Canīt give a page number for my my copy is a print out from and old scan on diskettes.

And it is no translation as suggested by some. Sam Heron was a native English speaker born in the UK. He is the fellow who developed sodium cooled valves.

Ahh a Brit...that explains it. 2 people's seperated by a common language.

[joeblogs]

I did find the exact section that pasoleati  refers to, that is the good news.

There is a later section where Heron argues the Merlin is a very "mild" engine and as a result, the effective performance number of fuel used in it was much higher than for the reference engine used to rate fuels in the first place. That would explain why RR was able to run this engine at such high MAP.  

The bad news is that I have not yet found where Heron defines what he means by "mild" & "severe" engines. So I have started re-reading all the chapters Heron wrote for that book.

Heron did another version of this published by Ethyl Corp a few years later. That one might be better written, but I have yet to find an affordable copy of that volume.

-Blogs

Originally posted by Wolfala
Ahh a Brit...that explains it. 2 people's seperated by a common language.

[dtango]

A reference I ran across stated the mild/severe engine categories relates to the octane / PN demands of the engine - milder engines being water-cooled compared to air-cooled being more severe.

For a "mild" engine richening the fuel mixture doesn't add any value to reducing detonation with increasing manifold pressure.  Heron's statement basically says that theoritically 100/130 fuel for a mild engine effectively acts like a 130/130 fuel.

I'm guessing the thinking here is that generally water-cooled engines more evenly cool an engine vs. an air-cooled engine with the result that air-cooled engine might have hot spots that can more easily result in detonation at higher manifold pressures which can only be offset by a richer fuel/air mixture.

Interestingly enough Heron also states that air-cooled engines can be mild engines as well in his statement though at a cost of complexity.

Tango, XO
412th FS Braunco Mustangs

[joeblogs]

That is my guess too.

-blogs

Originally posted by dtango
A reference I ran across stated the mild/severe engine categories relates to the octane / PN demands of the engine - milder engines being water-cooled compared to air-cooled being more severe.

For a "mild" engine richening the fuel mixture doesn't add any value to reducing detonation with increasing manifold pressure.  Heron's statement basically says that theoritically 100/130 fuel for a mild engine effectively acts like a 130/130 fuel.

I'm guessing the thinking here is that generally water-cooled engines more evenly cool an engine vs. an air-cooled engine with the result that air-cooled engine might have hot spots that can more easily result in detonation at higher manifold pressures which can only be offset by a richer fuel/air mixture.

Interestingly enough Heron also states that air-cooled engines can be mild engines as well in his statement though at a cost of complexity.

Tango, XO
412th FS Braunco Mustangs