Why nitrogen for prop governor

Ajax

Ajax

¯\_(ツ)_/¯
I realize that other planes use different methods like a spring, but what is the purpose of some using nitrogen instead of another gas. My guess would be because of its inert qualities, but I couldn't find an exact answer. Any of you guys know?
 
Moisture/stability of the gas. It's less susceptible to moisture and pressure changes with temperature is my guess.
 
Last I checked, Nitrogen has less moisture than compressed air. Combine that with inert qualities and you've got a winner for this application.
 
Old Dominion Flyer said:
Last I checked, Nitrogen has less moisture than compressed air. Combine that with inert qualities and you've got a winner for this application.
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That's kind of what I was thinking, my instructor and I did some reading and we read a part about the moisture. I just didn't know if there was something I had overlooked. Thanks guys.
 
ALL gases increase in pressure as temperature goes up and decrease as temp goes down. Nitrogen is no exception.

Also moisture would be no factor since whatever part of the governor holds the nitrogen is sealed.

Nitrogen is chemically inert and does not burn, so that is the likely answer
 
Mike H said:
ALL gases increase in pressure as temperature goes up and decrease as temp goes down. Nitrogen is no exception.
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Not entirely true. Nitrogen is less suceptible to expansion/overheating than "air."

Test data indicate that at nitrogen concentrations between 80 percent and 90 percent (the atmosphere contains approximately 80 percent nitrogen and 20 percent oxygen), ignition of inner tire liner samples occurred in a test chamber with temperatures varying from 478 °F to 518 °F. Nitrogen concentrations between 90 percent and 95 percent raised the autoignition temperatures to a range of 520 °F to 531 °F. At nitrogen concentrations greater than 95 percent, there was no pressure increase in the test chamber, even at chamber temperature of 670 °F, indicating that there was no ignition. Based on these tests, it was concluded that any concentration of oxygen in a tire in excess of 5 percent of the total gas will support a reaction. At a concentration above 10 percent, this reaction is an abrupt autoignition. At concentrations from 5 percent to 10 percent, this reaction is assumed to be a low level autoignition, based on measurement of test chamber pressure and temperature.
http://rgl.faa.gov/Regulatory_and_G...6256a3100713354!OpenDocument&ExpandSection=-4
 
NJA_Capt said:
Not entirely true. Nitrogen is less suceptible to expansion/overheating than "air."
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The article is referring to "combustion", not the mere increase in pressure due to temperature. Given that pressure is produced by the impact of molecules on an object as they flitter about, and temperature increases the mean velocity of said molecules, I'm skeptical that there is no pressure increase of any gas as the temperature rises in a container.
 
Even when it comes to autoignition, I don't think the small amount of gas in a prop governor is going to be nearly as much of an issue as the 670 degree temperature is all by itself
 
Mike H said:
Even when it comes to autoignition, I don't think the small amount of gas in a prop governor is going to be nearly as much of an issue as the 670 degree temperature is all by itself
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Probably so. Our Seneca POH said air could be used, as long as it's dry. The point in favor of Nitrogen is that it's a diatomic molecule, meaning its form is normally N_2; it's larger than single oxygen molecules and doesn't leak out as quickly through any seals.
 
tgrayson said:
The point in favor of Nitrogen is that it's a diatomic molecule, meaning its form is normally N_2; it's larger than single oxygen molecules and doesn't leak out as quickly through any seals.
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I believe oxygen is diatomic as well, O_2. O_2 molecules would be larger than N_2 molecules, no?
 
Pilot Hopeful said:
I believe oxygen is diatomic as well, O_2. O_2 molecules would be larger than N_2 molecules, no?
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You are correct on the diatomic-ness of Oxygen, but apparently the greater atomic weight does not translate into larger size. See here:
Excerpt:

It is often mistakenly assumed that "molecular size" correlates directly with "molecular weight". O2 does have a greater molecular weight (32) than N2 (28), but O2 is actually smaller in size. Thus, O2 fits through the relatively tight passage ways between polymer chains in the rubber more easily than does N2. The difference is size between O2 and N2 is very small, only about 0.3 times 10 to the -10th meters (0.00000000003 meters). Among the various descriptions of the sizes of molecules, that most applicable to transport phenomena​
 
Mike H said:
Ok, I'll be sure to let The Bends know about your theory
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Know a little before you get wirey like that. There is a reason why you see people with green valve caps on their car tires. It is a bigger molicule (no spell check, forgive me), and it changes less pressure with temprature. Reason #2 is why it is often used in aircraft tires. And it also has a lower moisture content so it doesn't freeze while in cruise at high altitudes.

When I was wrenching on cars I was required to take a class about the advantages of nitrogen for auto uses. How does "The Bends" apply to what we are talking about. We are discussing how temp effects it's.
 
I don't know why they are recommending it in you case, but nitrogen weighs less and doesn't expand as much or as rapidly as compressed air when heated, plus has less moisture content... this is the reason we use it in race tires and is the very reason car & tire manufacturers are now starting to recommend its use... When looking at new cars if you notice a green valve stem cap, it simply means the tire is filled with nitrogen from the factory... However if you have a bicycle tire with a green valve stem cap, it might also mean your bicycle tube is a self sealing type that's filled with slime tire sealant... Nitrogen can also prevent the possibility of fire.
http://science.jrank.org/pages/4684/Nitrogen-How-we-use.html#ixzz0zY4PaB8W
 
sparky said:
I don't know why they are recommending it in you case, but nitrogen weighs less and doesn't expand as much or as rapidly as compressed air when heated, plus has less moisture content... this is the reason we use it in race tires and is the very reason car & tire manufacturers are now starting to recommend its use... When looking at new cars if you notice a green valve stem cap, it simply means the tire is filled with nitrogen from the factory... However if you have a bicycle tire with a green valve stem cap, it might also mean your bicycle tube is a self sealing type that's filled with slime tire sealant... Nitrogen can also prevent the possibility of fire.
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In everyday car use, N2 provides no practical advantages, but it does lighten your wallet, which makes your car lighter and saves you gas. :rotfl:
 
z987k said:
In everyday car use, N2 provides no practical advantages, but it does lighten your wallet, which makes your car lighter and saves you gas. :rotfl:
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drive one in Az & Nv where air temps exceed 115-120 during the summer and you'll soon learn the advantage of nitrogen which expands far less than compressed air when heated...
 
Just a correction to your thread title-there is no nitrogen in the prop governor. The nitrogen would be in the propeller hub.
 
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