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fulanito_chile
03-22-2004, 03:24 AM
ok a few questions...
1.)What happens when i get the "Overheat" sign, and i do nothing about it?
2.)when the radiators are open does this make you go slower?
3.)what do supercharges do and how do you use them well
umm... thats about it

"The Chilean Airforce" (FACH) The 4th oldest in the World...

fulanito_chile
03-22-2004, 03:24 AM
ok a few questions...
1.)What happens when i get the "Overheat" sign, and i do nothing about it?
2.)when the radiators are open does this make you go slower?
3.)what do supercharges do and how do you use them well
umm... thats about it

"The Chilean Airforce" (FACH) The 4th oldest in the World...

carguy_
03-22-2004, 03:40 AM
1)In some planes you can go on forever.But on most planes if you leave it,the engine will systematically lose power and will get louder.Normally I would recommend running on overheat not more than o minute.

2)Yes,and I mean considerably slower.50-70km/h at open.

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Zayets
03-22-2004, 03:52 AM
1.Not much.Say 10 minutes , for some planes is more , for some less. Most of the time you'll render yer engine unusable.You will notice this by the sound your engine is making.Lack of power and so on. Not a good idea to take no action when you see this message.On the jet planes going fast and reducing throttle for a bit will cool down the engine.
2.Radiator open increase drag thus making your plane going slower. I drive with radiator open always after T/O simply because 50 kmph don't count to much for my Sturmo. If you are fighter jock close your radiator when in battle.Speed is essential.
3.A crank-driven air/fuel-mixture compressor, also called a blower. It increases atmospheric pressure in the engine to produce more horsepower.That is, charger on, more power. In some german planes it kicks on by itself when reaching a certain altitude.

Hope that helped.

Zayets out
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fulanito_chile
03-22-2004, 06:17 AM
yes..yes thank you

"The Chilean Airforce" (FACH) The 4th oldest in the World...

AirBot
03-22-2004, 06:34 AM
Just a little correction to what Zayets said:

The supercharger doesn't help you produce more horsepower. It helps you maintain the same power with higher altitude.
The engine requires a certain density of air to work most efficiently. As you gain altitude, air density decreases and the engine begins to lose power. The supercharger is meant to artificially increase air density so that the engine works more efficiently.

Zayets
03-22-2004, 07:00 AM
Airbot,
Yes and no. Doon' forget that suprchargers were mounted on automobiles first.
To be honest,I never understood why they didn't simply called it air compressor,because this is what is bolted to the front of the engine.Engine running is turning compressor wheel which presurize the air reaching carburetor.
Too sum up, a supercharger provides a greater air charge to the cylinders at high main shaft (cranckshaft) speeds. Therefore increasing boost without increasing engine size.Because supercharging maintains maximum intake charge, it offers particular advantages at high altitudes, where the atmosphere contains less oxygen.I think you are confusing it with the air mixture,here yes,mantaining a low air quantity at high alts will reduce power, and yes, damage your engine.
One final thing, if you are reaching stall speed in aclimb and kick in the supercharger do you think it will make any difference?

Zayets out
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Tully__
03-22-2004, 07:05 AM
Part one of a six part article on turbo and supercharging here (http://www.avweb.com/news/columns/182102-1.html). Links to the remaining five parts can be found in the box in the right hand column of that page about half way down.

It would probably help your understanding some if you also read the "Manifold Pressure Sucks" article linked near the top of the page and further down the right hand column as well.

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Seedking1
03-22-2004, 09:33 AM
Correct me if I am wrong here - a turbo charger and supercharger are both compressors - one works off manifold pressure(exhaust) and a supercharger off the crank (hence no lag) - both do increase hp - and for a supercharger 1hp per cubic inch(engine size) over and above a normally aspirated engines hp at ground level.So at altitude it is all relavant? Both force more air (thus fuel) into the combustion chambers - unlike normally aspirated engines, which suck fuel / air - hence the increase in hp for turbo / supercharged engines. In laymans terms - thats it?

Tully__
03-22-2004, 09:40 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
Correct me if I am wrong here - a turbo charger and supercharger are both compressors - one works off manifold pressure(exhaust) and a supercharger off the crank (hence no lag) - both do increase hp - and for a supercharger 1hp per cubic inch (engine size) at ground level.So at altitude it is all relavant? Both force more air (thus fuel) into the combustion chambers - unlike normally aspirated engines, which suck fuel / air - hence the increase in hp for turbo / supercharged engines. In laymans terms - thats it?<HR></BLOCKQUOTE>

More or less the deal.

As a further benefit, charged engines suffer less loss of horsepower with reduced air pressure at altitude. Many turbocharged aircraft have turbochargers that supply enough boost to blow the engine up at sea level, but regulate the amount of boost using the waste gate. As altitude increase/air pressure decreases, the waste gate closes to keep the turbo augmented manifold pressure at peak performance levels.

Similarly, some supercharged engines are equiped with two speed superchargers. As altitude increases and the first speed setting on the super charger becomes inadequate to compensate for the lack of air, the pilot or an automatic system switches it into high gear, returning peak performance. The manual version of this system has the disadvantage (in real life) that the pilot can damage or destroy his engine by forgetting to change back to the low altitude setting as the aircraft descends.

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Seedking1
03-22-2004, 09:50 AM
And the BF109 had a varible superchager - against the Spits manual version - so in varible form, the supercharger through a seroius of 'vanes' would compensate for the alitude, leaving the pilot more time to manage other things - like where are the bogies...or something like that - I think thats what you ment by an automatic version Tully?

Tully__
03-22-2004, 10:05 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
And the BF109 had a varible superchager - against the Spits manual version - so in varible form, the supercharger through a seroius of 'vanes' would compensate for the alitude, leaving the pilot more time to manage other things - like where are the bogies...or something like that - I think thats what you ment by an automatic version Tully?<HR></BLOCKQUOTE>

That goes beyong my knowledge of specific aircraft/engine design http://ubbxforums.ubi.com/images/smiley/16x16_smiley-sad.gif

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JR_Greenhorn
03-22-2004, 10:21 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
both do increase hp - and for a supercharger 1hp per cubic inch(engine size) over and above a normally aspirated engines hp at ground level.<HR></BLOCKQUOTE>No!
Be wary of such "rules of thumb," as they are often misleading. Usualy supercharging gains are best given in percentage increase in power, but even percentages can range from less than 20% to more than 50% increases.
Any power increases gaind via supercharging are dependent on the engine (type, displacement, equipment, condition, etc.) as well as the supercharger (design, type, drive, etc.) there are just way too many variables to assign a simple 1hp/ci rule of thumb.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
So at altitude it is all relavant?<HR></BLOCKQUOTE>Not exactly. As altitude increases, generally air density decreases. To compensate for this change, the supercharger in an aero engine attempts to increase the air density to as close to sea level as possible. With a mechanical supercharger, the only practical means (esp. in those days) to ajust the supercharger was changing its drive speed.
Many of the allied engines had a 2-speed gearbox driving the supercharger, so one can imagine that each speed was not the ideal setting, but rather a compromise for a range of altitudes. Thus, at some altitudes, the supercharger would do a better job of increasing air density than others.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
And the BF109 had a varible superchager - so in varible form, the supercharger through a seroius of 'vanes' would compensate for the alitude...<HR></BLOCKQUOTE>
Some of the DB600-series engines used in the Bf 109 aircraft had a fluid coupling drive (similar to the torque converter in an automatic transmission in a car) for the supercharger. This fluid coupling was controlled by barometric pressure. In this system, the supercharger drive gear ratio was fixed at some maximum value. Then the fluid coupling would allow slip based on the barometric pressure read by the control sensor. This system then, was designed to be self-adjusting or automatic.



By "vanes," I assume you're thinking of a more modern development used in some gas turbine engines, and, more recently, the Variable Area Turbine Nozzle system used in Aerodyne Aerocharger Turbochargers. This VATN system is used in exhaust driven turbochargers to change the area that the exhaust gas must squeeze through just before it gets to the turbine side of the turbocharger. By changing this area, exhaust gas stream flowrates can be controlled, thus controlling the output of the compressor side of the turbocharger.

Fillmore
03-22-2004, 11:55 AM
One of the recent patches fixed the drag with open radiators, they still slow you down but not the big 50-60kph like they used to.

Overheat warning will result in damaged engine, some planes as quickly as 2-3 minutes. Best to take your favourite planes and test them to see how long before engine damage. When I get the overheat warning I dtart counting, when I get to 120 I throttle back to 100 and open radiator (for 190As I ease up after count to 100).

Seedking1
03-23-2004, 05:06 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by JR_Greenhorn:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
both do increase hp - and for a supercharger 1hp per cubic inch(engine size) over and above a normally aspirated engines hp at ground level.<HR></BLOCKQUOTE>No!
Be wary of such "rules of thumb," as they are often misleading. Usualy supercharging gains are best given in percentage increase in power, but even percentages can range from less than 20% to more than 50% increases.
Any power increases gaind via supercharging are dependent on the engine (type, displacement, equipment, condition, etc.) as well as the supercharger (design, type, drive, etc.) there are just _way_ too many variables to assign a simple 1hp/ci rule of thumb.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
So at altitude it is all relavant?<HR></BLOCKQUOTE>Not exactly. As altitude increases, generally air density decreases. To compensate for this change, the supercharger in an aero engine attempts to increase the air density to as close to sea level as possible. With a mechanical supercharger, the only practical means (esp. in those days) to ajust the supercharger was changing its drive speed.
Many of the allied engines had a 2-speed gearbox driving the supercharger, so one can imagine that each speed was not the ideal setting, but rather a compromise for a range of altitudes. Thus, at some altitudes, the supercharger would do a better job of increasing air density than others.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Seedking1:
And the BF109 had a varible superchager - so in varible form, the supercharger through a seroius of 'vanes' would compensate for the alitude...<HR></BLOCKQUOTE>
Some of the DB600-series engines used in the Bf 109 aircraft had a fluid coupling drive (similar to the torque converter in an automatic transmission in a car) for the supercharger. This fluid coupling was controlled by barometric pressure. In this system, the supercharger drive gear ratio was fixed at some maximum value. Then the fluid coupling would allow slip based on the barometric pressure read by the control sensor. This system then, was designed to be self-adjusting or automatic.



By "vanes," I assume you're thinking of a more modern development used in some gas turbine engines, and, more recently, the Variable Area Turbine Nozzle system used in Aerodyne Aerocharger Turbochargers. This VATN system is used in exhaust driven turbochargers to change the area that the exhaust gas must squeeze through just before it gets to the turbine side of the turbocharger. By changing this area, exhaust gas stream flowrates can be controlled, thus controlling the output of the compressor side of the turbocharger.<HR></BLOCKQUOTE>

Seedking1
03-23-2004, 05:07 AM
Thanks JR - that clears that up then for me.