Terry Adams wrote:
Is the 10 psi pressurization differential really cummulative? I have five
air compressors of various sizes. All the tanks are made from the same
gauge material and are cylindrical in shape. My smallest compressor tank
holds 505 square inches. At 110psi pressurization differential is it
correct to say that 55,550 pounds are trying to escape? My largest
compressor tank holds 22,474 square inches. At 110psi pressurization
differential is it correct to say that 2,472,140 pounds are trying to blow
the ends off the tank? Someone should tell the manufacturers to make the
smaller tanks out of lighter gauge material.
<< As Vance recently pointed out it is nearly impossible to build a
light
> > weight pressure vessel that looks like a Burnelli fuselage.
> >
> > Structurally efficient pressure vessel tends to look like a sphere
or
> > a tube.
> >
> > Also, low aspect ratio lifting bodies have high induced drag if
> > in fact they indeed reach a high enough angle of attack to generate
appreciable
> > lift. If they don't they merely have excess skin friction drag due
to an
> > unfavorable surface area to volume ratio. In short the Burnelli
flies
> > in the face of aerodynamic and structural principle :-) >>
Should Boeing give up on it's blended wing research before it's too late?
Lynn E. Hanover
lehanover@aol.com
I think so. The Boeing project prompted Vance's response to the
pressurization
problem in the first place as I recall. I agree with Vance.
To give one a feel for this lets say the passenger compartment is 50 feet
wide
and 50 feet long or 2500 square feet. At 144 square inches per square foot
that
is 360,000 square inches. At 10 psi pressurization differential 3,600,000
pounds
is trying to rip the roof (top of the blended wing) off or blow the floor
(bottom of the blended wing) out from under you.
Let's compare this with the pressure due to fuel weight in a conventional
wing.
Let's say fuel weighs six pound per gallon and there is 232 cubic inches in
a gallon.
That is... it weighs .0258 pounds per cubic inch.
If the wing/fuel tank is four feet or 48 inches thick that would be a
column of fuel
one inch square by 48 inches high or 48 cubic inches of fuel.
At .025862 pounds per cubic inch that would be only 1.2 psi on the bottom
wing skin by my calculations. At 3 G's that would still be only 3.6 psi.
If we break the big 50 foot square room into smaller
rectangular rooms say ten feet wide to tie the roof and floor together you
have
cyclical stress concentrations in the corners. In other words the
rectangular
rooms want to become tubes. In addition the blended wing skins will have
waves in
them due to the deflections. A structural engineering nightmare.
Is all this worth what ever small aerodynamic advantage one can eke
out of a blended wing design? I don't think so. Perhaps there could be
columns every couple of feet or so tying roof and floor together.
I also like to look out of the window. I don't like flying around in
a large flat room without being able to see what is going on from time to
time.
Paul Lamar
Terry Adams wrote:
Is the 10 psi pressurization differential really cummulative? I have five
air compressors of various sizes. All the tanks are made from the same
gauge material and are cylindrical in shape. My smallest compressor tank
holds 505 square inches. At 110psi pressurization differential is it
correct to say that 55,550 pounds are trying to escape? My largest
compressor tank holds 22,474 square inches. At 110psi pressurization
differential is it correct to say that 2,472,140 pounds are trying to blow
the ends off the tank? Someone should tell the manufacturers to make the
smaller tanks out of lighter gauge material.
The smaller the tank the lower the tensile loads in the tank walls for a given pressure.
Pressurize a 747 to 110 psi and watch what happens. In fact just a little over
pressure supplied by a small bomb can blow a 747 apart big time.
Here are the formulas as supplied by Vance.
Paul Lamar
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