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Old 09-08-2006, 12:40 PM   #41
RangerRover
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Default Re: Basic Engine Operations

Ok lets review:

Quote:
Originally Posted by project92SC2
Look up your scientific facts again. The pull of the earth's gravity, and the weight of atmospheric pressure is stronger at sea level than it is at a higher level. Therefore you weigh more.
And titanium's response:
Quote:
Originally Posted by Titanium48
o lets do some calculations. Earth's sea level radius is 6367km+/-20km depending on latitude (being closest to average near 45N or S). Going from sea level to Denver (altitude 1600m) will alter the accelleration due to gravity by a factor of (6367^2)/((6367+1.6)^2) = 0.999498, making you 0.05% lighter (199.9 lb instead of 200) at the higher elevation.

The universal gas law is PV=nRT, solving for n gives us n=PV/RT. 1 cubic meter of air at 101.3kPa and 294K (21C) contains (101300Pa*1m3)/(8.314J/K.mol*294K)=41.443 moles of gas molecules. With a mean molecular weight of about 29 that gives a density of 1.20 kg/m3. Moving up to 1600m (average air pressure of 84 kPa) gives us (84000Pa*1m3)/(8.314J/K.mol*294K)=34.365 moles of gas, for a density of 1.00 kg/m3. If you weigh about 200lb your volume will be about 100L (0.1m3), resulting in a buoyancy effect of 0.12kg at sea level and 0.10kg at 1600m. Thus you would be 20g (0.05 lb) LIGHTER at sea level if gravity was the same, which it would be if your trip back to sea level took you to the Gulf of Mexico (lower latitude = larger radius of Earth).
Project92Sc2's response to cold, hard math numbers:

Quote:
Originally Posted by project92SC2
Do your homework some more....... The very term "pressure" pwns you. get your science straight before you try to prove me wrong again plz.
Ok, so you didn't believe the math the first time, lets try again:

Quote:
Originally Posted by Titanium48
For example: Day 1 - (RH) = 40%, barometric pressure = 102kPa, temperature = 30C. Day 2 - RH=90%, barometer = 100kPa, temperature = 20C.
At 30C the saturated vapor pressure of water is 4.2kPa, so the equivalent dry atmospheric pressure is 102-(0.4*4.2)=100.3kPa. The equivalent dry density is then (100300Pa)(1m3)/(8.314)(303)=39.82 mol/m3 or 1.15kg/m3.
At 20C the saturated vapor pressure of water is 2.3kPa, so the equivalent dry atmospheric pressure is 100-(0.9*2.3)=97.9kPa. The equivalent dry density is then (97900Pa)(1m3)/(8.314)(293)=40.19 mol/m3 or 1.17kg/m3.
Project92Sc2's response to cold, hard math numbers: Nothing.

Quote:
Originally Posted by Gerry Proctor
I vote we let it circle the thread drain and go down as quickly as possible.
Agreed 100%. There is some good info in here but too much to wade through to make it permanent.

Quote:
Originally Posted by dhymers
What... is the air-speed velocity of an unladen swallow?
African or European?

...
You can tell Linux is made by geeks.

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Old 09-08-2006, 05:37 PM   #42
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Default Re: Basic Engine Operations

OMG! ROTFLMFAO

I'm normally a quiet lurker, but I have to say:

This thread contains more claptrap than Scientology and the Book of Mormon combined!

The most accurate post in this thread:

" think I know where the extra 12 pounds came from. Some people just retain it, some just visit the latrine and get rid of it. From reading your many posts, it appears that you are full of it." -Titanium48

Titanium48, I think you know more of basic physics and chemistry than I do, but I disagree with you on the density of humid air. Since water vapor only wieghs about 18g/mol and N2 (main component of air) weighs about 28g/mol, I believe that humid air is less dense than dry air (if all else is equal).

I don't think this thread is informative or useful, but it is a riot!

Sincerely,
David

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Old 09-08-2006, 05:59 PM   #43
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Default Re: Basic Engine Operations

Looking back over some posts,
Quote:
Originally Posted by project92SC2
In a low pressure front, the air is cooled, and condensed, with added humidity, it is already more than 14.7psi in weight by volume.
I am beginning to wonder if we have been trolled.

Also, that his weight changed by 12 pounds due to a difference in air pressure reads like trolling.

Saying that air has condensed in a low pressure front may be an honest misunderstanding of the meaning of the word "condensed," but "psi in weight by volume"? What on earth could that string of words mean? I would only write that if I was trolling.

Okay, I'm done. I'm going back to lurking now.

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Old 09-08-2006, 06:59 PM   #44
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Default Re: Basic Engine Operations

Quote:
Originally Posted by chopperdave
" think I know where the extra 12 pounds came from. Some people just retain it, some just visit the latrine and get rid of it. From reading your many posts, it appears that you are full of it." -Titanium48
That wasn't me...but it was funny.

Quote:
Originally Posted by chopperdave
Titanium48, I think you know more of basic physics and chemistry than I do, but I disagree with you on the density of humid air. Since water vapor only wieghs about 18g/mol and N2 (main component of air) weighs about 28g/mol, I believe that humid air is less dense than dry air (if all else is equal).
Yes, you are right. In the example when I suggested that humid air was more dense "all else" was not equal. The humid air was 10C cooler and the absolute humidity was only slightly higher. 90% RH at 20C = 50% RH at 30C

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Old 09-08-2006, 07:08 PM   #45
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Default Re: Basic Engine Operations

Quote:
Originally Posted by project92SC2
The reason I said fuel is not a power additive, is because if gasoline engines had the same compression ratio as a diesel engine, they could run without fuel. Diesels will run without fuel..... but only for a few short seconds until something blows.
ROTFLMA! (You do realize that the way most running diesels engines are noramally shut down is by shutting off the fuel supply...right? )

Quote:
A supercharger is not more efficient than a turbocharger, as the parasitic loss in power is greater. You know a lot, I'll give that to you, but these are the few that I KNOW for a fact, and can bet my life on.
A supercharger has to use power from the crankshaft to turn, thus, the parasitic power loss increases as boost increases....... it is about a 20%-25% powerloss to make good horsepower....... but you're right, they are easier to tune.... which is why that is my first setup.
A turbocharger is less parasitic....... and yes...... at low spool rates, it does restrict exhaust flow..... but at max spool rates, it's actually moving nearly with the exhaust due to inertia, with little resistance so that it doesn't loose speed.
I know my forced induction, had 12 weeks straight of training in it. This is why the military uses turbochargers instead of superchargers now....
Actually the military is using turbochargers because they are CHEAPER, are more tolerant of inconsistant fuel, and hold up better in DUSTY environments with less maintenance than super chargers do, due to the larger clearances between the compressor vanes and their housings...

Oh, and there are two common types of superchargers in use now...the "Roots" or "Vane" type and Centrifugal. A centrifugal supercharger is essentially just the compressor end of a turbocharger driven by a belt and reduction gear set up...which are you referring to as far as efficientcy is concerned?

...
Old Saturns never die, people KILL them, so check your damn oil!
"Unthinking respect for authority is the greatest enemy of truth." Albert Einstein

Last edited by wolfman; 09-08-2006 at 07:19 PM..

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Old 09-08-2006, 07:33 PM   #46
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Default Re: Basic Engine Operations

Well, really there are three. The screw supercharger is the third common type. While to many it looks to be a roots blower, it is very different in design and operation. It compresses air inside the case and discharges it into the manifold. There is a fourth, but it is very uncommon. And that's the axial flow supercharger. Latham built these in the 60s and 70s but their cost put them completely out of reach and made them uncompetitive with they typical roots blower. But I guess after 10,000 plus posts, a minor correction ain't bad.

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Old 09-08-2006, 08:41 PM   #47
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Default Re: Basic Engine Operations

Thanks, I had forgotten about the axial flow supercharger. IIRC used strictly for domestic V8's and sold under the name "Latham Axial Flow Supercharger". This was built from 1956 to 1965 in Florida, and again and for smaller applications from around ~1983 to ~1992. They are apparently available again now, though I do not know about the cost or if the comapny is still called "Latham". Axial superchargers function much the same way a turbine jet engine's compressor does.

I also generally used "Roots" as a blanket description for the screw type blowers as the only real difference (IMHO) is the shape of the internal compressor bits. (I always thought one looked like meshing coarse thread screws and the other meshing fine thread screws)

...
Old Saturns never die, people KILL them, so check your damn oil!
"Unthinking respect for authority is the greatest enemy of truth." Albert Einstein

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Old 09-09-2006, 03:41 PM   #48
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Default Re: Basic Engine Operations

Quote:
Originally Posted by project92SC2
if gasoline engines had the same compression ratio as a diesel engine, they could run without fuel.
And... the energy would come from... where?

You never did tell me what you wanted me to see in your post

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Old 09-10-2006, 03:42 AM   #49
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Default Re: Basic Engine Operations

To reply to wolfman's post about diesels shutting off the fuel supply.... yes, that's how they shut off, but my instructor showed us a malfunction in diesels, he set-up the malfunction on a 6V53 Detroit Diesel (military engine for the M113A2 APC) and did a few turns to the crank with an extreme duty impact, and turned it, and it ran for a few moments without fuel, extremely crappy, but it ran. I can't remember quite how he did that, but I guess it's better I didn't, since I would probably do something like that if I was drunk off my rocker.

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