Helicopter in a box....
Join Date: Oct 2003
Location: Over here
Posts: 1,030
Likes: 0
Received 0 Likes
on
0 Posts
Sid, you need a course in basic chemistry. Carbon and oxygen aren't produced, they're merely combined in different configurations. It's impossible to manufacture atoms of any element from nothing. Elements cannot just suddenly appear, they're all there all the time in a different form. The fuel is converted from a liquid to a gas, and the carbon and hydrogen in it are recombined with the oxygen in the air. The only thing that changes is the temperature, which changes the pressure, which is the cause of the water rising in your previous example.
Purveyor of Egg Liqueur to Lucifer
"The only thing that changes is the temperature."
Thank you GP, at last. Like pulling teeth!
So the temperature has risen and as we all know hot air rises therefore the scales will indicate less.
Got there eventually.
psst, how about this;
Does the TRT in the hover, actually EQUAL the a/c weight, or does it have to be ever so slightly greater in order to compensate for gravitational acceleration, due to momentary lapses in constant lift throughout the rotor disc area??
Thank you GP, at last. Like pulling teeth!
So the temperature has risen and as we all know hot air rises therefore the scales will indicate less.
Got there eventually.
psst, how about this;
Does the TRT in the hover, actually EQUAL the a/c weight, or does it have to be ever so slightly greater in order to compensate for gravitational acceleration, due to momentary lapses in constant lift throughout the rotor disc area??
Join Date: Apr 2003
Location: USA
Age: 75
Posts: 3,012
Likes: 0
Received 0 Likes
on
0 Posts
Silsoesid,
The scale will read higher when the aircraft is lifting up, since the aircraft is accelerating upward briefly (just as the scale bounces higher when you step on it) but when you are in a steady hover, the weight reading is the same as when the helo was sitting on the ground.
The high temp gasses rsing is a slight bouyant effect but does not change this discussion (it is an interesting side discussion, though!)
The scale will read higher when the aircraft is lifting up, since the aircraft is accelerating upward briefly (just as the scale bounces higher when you step on it) but when you are in a steady hover, the weight reading is the same as when the helo was sitting on the ground.
The high temp gasses rsing is a slight bouyant effect but does not change this discussion (it is an interesting side discussion, though!)
How is the helicopter actually going to hover when it is in the middle of recirculation - as fast as it displaces air downwards (accelerating it) the air is deflected round the box and enters the disc from above with a higher velocity - therefore more pitch is required to accelerate the air which then goes round the box faster and enters the disc faster than the last time it went through - eventually the blades are having to work at such high AoA that they stall - so how is it going to get off the bottom of the box. There is no constant supply of slow moving or static air for the rotor to accelerate and therefore it will not lift the helicopter.
"So the temperature has risen and as we all know hot air rises therefore the scales will indicate less."
SilsoeSid - Sorry but the hot gasses are not going to make the box appear lighter because they cannot escape the sealed system. The mass of the system has remained exactly the same (let's not get onto the subject of energy escaping the system in the form of heat!!!)
Cheers
TeeS
SilsoeSid - Sorry but the hot gasses are not going to make the box appear lighter because they cannot escape the sealed system. The mass of the system has remained exactly the same (let's not get onto the subject of energy escaping the system in the form of heat!!!)
Cheers
TeeS
Join Date: Mar 2004
Location: UK
Posts: 224
Likes: 0
Received 0 Likes
on
0 Posts
If the box is airtight and rigid, the gas mixture will not be able to expand so the pressure will increase. The overall mass of the box plus B206, fuel, pilot and air/exhaust mixture would remain constant, as would the volume of the box. Therefore the density of the box would remain constant and there would be no buoyancy effect.
From the pilot's point of view, it would be dark, noisy, smelly, hot and your altimeter would be lying. No change there then!
Beat me to it Tees!
From the pilot's point of view, it would be dark, noisy, smelly, hot and your altimeter would be lying. No change there then!
Beat me to it Tees!
Purveyor of Egg Liqueur to Lucifer
If he put his landing light on it wouldn't be dark any more. 
Besides, in this very strong cardboard box , if the pressure increases, would there be a point at which, if the door of the box was to suddenly be opened during this experiment, the pilot would suffer from the bends? (I'm not a scuba diver by the way so, 
)
Besides, in this very strong cardboard box
, if the pressure increases, would there be a point at which, if the door of the box was to suddenly be opened during this experiment, the pilot would suffer from the bends? (I'm not a scuba diver by the way so, )
Join Date: Dec 2004
Location: New Orleans
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Not likely. You need a pretty large pressure differential to experience the bends. For every 30 ft a diver descends, he experiences an additional 1 atmosphere of pressure (actually a little less but eh). A diver at 90 feet is therefore experiencing 4 atm, or 58.8 psi.
On the other hand, the difference between sea level and outer space is only 1 atm. Good thing too, or you'd get the bends while driving in the mountains. I haven't done the math, but I imagine the temperature required to create that much pressure would cook the pilot long before he'd be subject to the bends
On the other hand, the difference between sea level and outer space is only 1 atm. Good thing too, or you'd get the bends while driving in the mountains. I haven't done the math, but I imagine the temperature required to create that much pressure would cook the pilot long before he'd be subject to the bends
Join Date: Jul 2002
Location: Denver, CO and the GOM
Age: 63
Posts: 515
Likes: 0
Received 0 Likes
on
0 Posts
Hi Sid,
If you heat air but do not allow it to expand, it does not get less dense.
If you take a fixed mass oxygen and hydrocarbons and rearrange the structure of their respective electrons, the total mass does not change (as you already saw).
However, the question remains - will NR go up or down as the CO2 content increases?
If you heat air but do not allow it to expand, it does not get less dense.
If you take a fixed mass oxygen and hydrocarbons and rearrange the structure of their respective electrons, the total mass does not change (as you already saw).
However, the question remains - will NR go up or down as the CO2 content increases?
Purveyor of Egg Liqueur to Lucifer
FW207, surely with a govenor and fuel controller fitted, the Nr would remain the same. (N2 = 100% and N1 altered to maintain constant Nr, unless of course the N2 govenor goes haywire)
Although as the air content was replaced with CO2, wouldn't the T4 soar, as the flame wouldn't be cooled as easily?
If we emptied the box and instead of the Jetranger and pilot placed in it an electric hot plate and a pot containing 1 litre of water. As the water reached and maintained boiling point, would the weight of the box plus contents remain the same?
Although as the air content was replaced with CO2, wouldn't the T4 soar, as the flame wouldn't be cooled as easily?
If we emptied the box and instead of the Jetranger and pilot placed in it an electric hot plate and a pot containing 1 litre of water. As the water reached and maintained boiling point, would the weight of the box plus contents remain the same?
Join Date: Mar 2004
Location: UK
Posts: 224
Likes: 0
Received 0 Likes
on
0 Posts
In a sealed box, the fuel will be converted to gas and the ambient temperature will increase. This will result in an increase in pressure and density (more gas in the system as the liquid fuel is converted to gas). There would be an increase in drag and providing the govenor is functional, Nr would be constant, but Tq will increase. Whether this increase would be seen on a torque meter is questionable. The T4 would increase and the efficiency of the engine would reduce since T1 increases. I would imagine this would cause an increase in Ng.
the fuel will be converted to gas and the ambient temperature will increase
Surely the ambient temperature would have to DECREASE to provide the energy to convert the liquid fuel to its vapour form, etc., etc., ......................
Boomerangben - But surely as the drag increased due to more dense air so would the lift, lower the lever to prevent it climbing and the drag will reduce!
Bomber ARIS - I think he meant from an Exothermic chemical reaction not evaporation!
(Note to self - TeeS get yourself a life!)
Bomber ARIS - I think he meant from an Exothermic chemical reaction not evaporation!
(Note to self - TeeS get yourself a life!)
Join Date: Mar 2004
Location: UK
Posts: 224
Likes: 0
Received 0 Likes
on
0 Posts
TeeS,
Agreed, in flight you would be able to reduce pitch. I was thinking about the flat pitch, ie burning and turning with skids on the bottom of the box.
Bommber,
A gas turbine does not vapourise the fuel, it atomises it (converts it to a very fine spray). In fact as the temperture goes up the fuel temp increases and viscosity will go down and the engine driven fuel pump will have to work less hard...........
Bollox to this, off to get myself a life.
Agreed, in flight you would be able to reduce pitch. I was thinking about the flat pitch, ie burning and turning with skids on the bottom of the box.
Bommber,
A gas turbine does not vapourise the fuel, it atomises it (converts it to a very fine spray). In fact as the temperture goes up the fuel temp increases and viscosity will go down and the engine driven fuel pump will have to work less hard...........
Bollox to this, off to get myself a life.
