From RocketSlinger@SBCGlobal.net (email me there please)… This is a sub-site
to main site at www.rocketslinger.com …
This web
site last updated 04 April 2018
A Method of Actively, Constantly Re-Balancing a
Spinning Turbine
This
sub-page to www.rocketslinger.com is
meant to continue off of ideas presented right before “figure 47” (use that as
a search-string at the main root web page).
If a turbine design (as presented there) is susceptible to becoming
un-balanced in mid-flight, for any reason really, then we’d want to re-balance
it with an active correction re-balancing technology. Specifically in this case we are envisioning
a method of changing a jet engine (turbine) into a rocket engine at high
altitudes, AKA “ variable engine geometry”, using pyrometric ceramic-containing
composite turbine blades. Please refer
back to the main page, of course!
As mentioned there, any automobile owner who pays a tiny
bit of attention at the tire shop will realize that his or her tire, mounted on
a truck or car wheel, has to be spin-mass or spin-momentum balanced by adding
an appropriately-sized mass to the spinning assembly of wheel plus tire. Otherwise, destructive wobbling can set it. Now suppose (as would analogous to the case of
a variable-geometry jet engine) that your wheel-plus-tire assembly is going to
somewhat chaotically shed bits and pieces of itself, and/or be shifting pieces
of itself to a different spin radius (different from its originally installed
position), so that “angular momentum” and spin-balancing is going to start
bouncing all over the place, half-way through your high-speed road trip. Constant and active re-balancing “in flight”
here would be way handy, right? So let’s
go there!
This
sub-page here will try to focus on what I think are the BEST options, ignoring
the rest. The main page mentions some
other alternate options for spin-balancing.
A SUMMARY of what follows below is this:
For SENSING the degree and orientation of a wobble or a state of the
spinning mass (turbine) being off-center, we simply rely on the fact that
centrifugal force (in what engineers would call a potentially destructive run-away
process of “positive feedback”) will take the off-center mass, and bend, warp,
and twist the structure of the spinning mass, to allow the highest off-center
mass to go yet FURTHER away from the center, aggravating the problem yet
more. So we put a fluid-filled tube all
around the outer perimeter of the spinning mass. The outermost (or most-off-balanced,
highest-mass) part of the perimeter tube is going to gather the most fluid (and
mass of the fluid)… Aggravating the
problem, yes! But if we can use SENSORS
to immediately, actively sense where the fluid is concentrating, then other
activators and masses (on the spinning turbine blade in this case) can increase
the mass concentration (or degree of pulling-outwards, centrifugal force) on
the exact OPPOSITE wall of the turbine, which lacks sufficient mass, compared
to where the fluid is gathering or concentrating most heavily.
What,
exactly, might a simplest and most effective method of measuring such fluid
distribution in a spinning tube be like?
What is the fluid, what is the tube made of, and how do the sensors
work? Many choices are possible… Liquid mercury would work, but is expensive
and toxic. Saltwater is reasonably
conductive, not horribly toxic at all, and is tolerably compatible with metals
and ceramics, and so will be the choice described here. For the TUBE, metals work really nicely, but
are highly conductive of electricity, and so are not compatible with electronic
sensors that could be used, otherwise, to test the conductivity (or inversely,
the resistance) of saltwater in the tubes.
Ceramics, on the other hand (just like metals) can be
high-temperatures-tolerant, for our high-temperature jet-turbine environment
here… BUT, ceramics, unlike metals, are
NOT conductive, and so it would be easy enough to embed a ceramic tube with
saltwater conductivity sensors. Yet on
the other hand, unlike metals, ceramics are not malleable or ductile, and so a
ceramic tube, in such an environment, would be quite susceptible to shock and
vibrations, and to temperature changes, causing it to crack or even shatter,
losing its contents. A purely ceramic
tube here is highly unlikely to be practical.
So what
is envisioned here is a combination of metal tubing, which would comprise the
majority of this spinning tube. However,
PARTS of the tube (in small scattered segments spread evenly around the round
“inner tube” here) would be made of ceramics, which in turn would be embedded
with the sensors. A few alternate
schemes for the details, mechanically and electronically, will be discussed
here.
As far
as the active re-balancing goes, the main page scenarios (masses on tracks or
on flexible helical screws for instance, travelling under some sort of motor
control around the outer perimeter of the spinning turbine) are hereby rejected
as possible but not plausible. Some
stubby “turbo-prop” propeller blades mounted on the outside of the spinning
turbine walls, as described on the main page, would help, in the lower
atmosphere, to propel our envisions jet-becomes-a-rocket vehicle here. Why not put small motors, and track or
helical screws, and masses, on each (or at least on many) of these blades? In the lower atmosphere (where we want these
masses out of the way of airflow) the masses would be kept close to the outer
wall of the turbine. In the high
atmosphere (thin air), immediately before the active (and chaotic)
re-configuration of the jet-engine-becoming-a-rocket is about to begin, the
masses (mounted on these outer turbo-prop, propeller blades) would all actively
be re-positioned to a “middle” position (half-way between the turbine wall and
the outermost extent of their ability to be positioned further out). Now when the chaotic re-configuration of the
partially-melting pyrometric-ceramic-containing turbine blades starts, these
outer-mounted masses are prepositioned to countervail. The actively re-positionable masses on these
outer blades, that are positioned where the sense fluids have concentrated (too
much pulling-outward centrifugal force) will be actively brought inwards,
closer to the turbine wall. The actively
powered masses on the OPPOSITE wall will be pushed further OUT, away from the
center of the spinning mass of the entire assembly. This will correct the spin imbalance. As the hippies learned in the 60s, you know,
the more far-out you are, on a spinning mass like our planet, the more “pull”
you have (with those among your fellows who adore far-out-ness, at least; the
analogy goes only so far, as you are a fellow far-out “Dude”!). J
So there
you have it… A plausible sensor system,
and a plausible method of actively re-distributing the centeredness (or lack of
off-centeredness) of the spinning assembly, here. Now all I need to do is to spell out some
more details and options or variations, and make some pretty drawings to
clarify… As soon as I find some more
time! Back to my day job for now… I am a C Plus Ranger by day, and a
Rocketslinger by night, but only when I find some ideas, and some time…
OK, I’m
back, here we go… Pressure sensors and
vibration sensors might be part of the scheme(s) here, you can “Google” and
“Wiki” this as well as I can, or see http://en.wikipedia.org/wiki/Pressure_sensor
, http://en.wikipedia.org/wiki/Piezoelectric_sensor
, etc. A fluid (like saltwater) arrayed
around a tube around the periphery of the turbine, with the fluid allowed to
concentrate (become deepest) at the furthest-away-from-the-center-of-the-spinning-mass
would, especially under high spin speeds, have greater fluid pressure (due to
centrifugal force) than the opposite side of the spinning assembly. This is obvious, and I have no special
creative ideas to add here. However, I
believe (I might be wrong, it HAS been known to happen!!!) that reaction speeds
on such pressure sensors, and perhaps resolution as well, would leave something
to be desired, for this use here.
Near-instantaneous fluid-depths measurements could be gathered as
described below.
First
off, let’s describe a very simple method of detecting the presence or absence
of electrically conductive fluid (saltwater) in a ceramic tube. A minus “-“ voltage (ground, AKA “GND”, or
-12 VDC, or -48 VDC, whatever is handy) is applied to small wires filling small
holes in the ceramic tube, at the “bottom” of the tube, along the length of
this segment of tube. “Bottom” being the
part, in this case, of the tube that is furthest away from the center of the
spinning mass. Yes, our sensors here are
NOT going to work until the turbine is spinning rapidly, but that shouldn’t
matter much… Low spin rate means wobbles
are less troublesome. … OK, so then we array more holes with more
wires, and “pullup resistors”, pulled up to +12 VDC or +48 VDC or whatever DC
power-supply voltage is handy. The
“pulled up voltage” is then routed off to the central sensing and control
computer. A solidly high sensed voltage
means “high and dry”, a fluctuating one bouncing all over the place means you
are on the “water line”, and a solidly
low sensed voltage means your sense point if thoroughly underwater. The central computer of course “knows” where
each sense point is located, and takes correcting control measures
accordingly. Here is a cross-section of
tubing showing the wiring as described here.
Figure 1
The
above drawing almost definitely shows more sense points than would be needed,
but hopefully get the point across.
Also, the points will be spread out across the length of a tube segment
as well as along the internal circumference of the tube, they would not have to
be horribly densely placed as is implied in the drawing.
Figure 2
The
above drawing hopefully clarifies that there is a hollow fluid-filled tube
running around the full outer circumference of the spinning turbine, and that
the fluid is free to let centrifugal force, force it to gather deepest at the
most-distorted or most-off-center, outermost reaches of the spinning
assembly. That is (refer back to main
page), a chaotic process of transforming a turbine section of a jet engine
(think “variable geometry engine”, perhaps incorporating
partially-pyrometric-ceramic blades) into a rocket engine will almost
inevitably lead to wobbles or asymmetries.
The spinning structure will deform to allow the highest concentrations
of mass to bulge outwards, the furthest away from the central spin axis. This tube is meant to sense the degree and
orientation of such asymmetries or wobbles.
The wobbles can then be removed by corrective actions to be described
later.
In
passing (with credit to my XYZ relative, person anonymous, for mentioning
this), here is a possible but probably implausible idea (we DO want to fend off
as many patent trolls as we can, now, don’t forget!): Like the cilia inside structures in the
living ear’s sense parts (“cochlea”), we COULD even equip the turbine-mounted
sense tube described here, with internal hairs or “cilia” that sense the FLOW
direction (and perhaps also speed) of the sense fluid, here, as well as
pressure or depth. Cilia-based sensing
could provide even yet more data, and faster data, than depth alone, probably,
but probably adds too much complexity, and more data than we want! However, PASSIVE (non-sensing elements) of
stiff metal “hairs” (cilia-like, or, think of bristles on a VERY stiff brush, a
wire brush) should almost definitely be included inside the tubes of the
here-described apparatus, to “dampen” waves inside the sense tube. Otherwise, we will have waves travelling
around and around the fluid surface inside the tube, constantly introducing a
noise nuisance. Alternately,
periodically-spaced semi-obstructions of mesh screen would perform the
wave-suppression function as well.
As
mentioned before, making the WHOLE tube out of ceramics alone is probably not
plausible, because of the brittle nature of ceramics. Making the whole tube out of metal won’t
work, because metals are better than saltwater for being electrically
conductive; the sense elements of the tube have little practical choice other
than to be made of ceramics. In passing,
let me mention (fend off the patent trolls as usual!), it MIGHT be possible to
put the ceramic elements INSIDE a sealed-metal tube, but this would be hard to
do, manufacturing-wise, I suspect, and would be a maintenance nightmare as
well, for lack of easy access to internal elements (lacks modularity).
So how
do we manufacture the sense tube? With,
say, copper tubing, or some other suitable metal… It would be nice, where the metal tube meets
the ceramic tube segment, to try our best to have the “thermal coefficient of
expansion” of the metal, match or almost match, that of the ceramic. The I/F (interface) between metal and ceramic
may or may not be threaded, and it may or may not have a hose clamp on the
outside of the metal that encloses the ceramic (the other way around would make
no sense at all). I suspect that the
hose clamp arrangement is probably best. Since this will be a stress point, the
total thickness of the ceramic tube-wall should be thicker (stronger) here than
elsewhere. The actual fluid channel should
be uniform in carrying capacity, and in radial distance away from the central
spin axis, throughout the entire length of the tube. BUT, the actual thicknesses of various points
along the tube may vary. Also, more hose
clamps, and a more complex (convoluted) surface at these pinch-points, will
help reduce leakage. Some small amount
of leakage at the metal-to-ceramic I/F may be inevitable… Unless we add some high-temperature-resistant
gasket or sealant material in there?
More on that later… But anyway,
more surface area of metal mating to ceramics, under the hose clamps, may help
to reduce leakage. OK, so finally, here
is your drawing of the ceramic to metal tube I/F:
Figure 3
Notice
that the metal tube-walls do not need to be as thick to have as much structural
integrity as the ceramic tube-walls, AND that the ceramic tube-walls are
thickened even more to withstand the “stress point” where two types of
materials meet, AND the compressive forces of hose clamps are added. Hose clamps (which can be made of metal),
metal tube, and ceramics are all readily available as non-toxic and
high-temperature-resistant, and so this all looks to be very plausible (for use
in a hot jet-engine environment). One
weak spot may be at the metal to ceramic I/F, where temperature cycling and
vibrations may lead to fluid leaks… We
may have to add some gasket or sealant (caulking) material(s) there… Which must be high-temperature tolerant! Sounds like asbestos time to me!
And now,
please forgive me, but I have to momentarily divert to some asbestos-related
ranting and raving for a few paragraphs, please skip a few if you are just
after the purely engineering-related matters…
I have
read that gasoline and asbestos are roughly equal as toxins (sorry, I have no
search results for you on that one). We
all know that gasoline is highly toxic, to say the least. Yet…
Speaking of search results, check this out: I put into “Google” the phrase “asbestos
toxicity” and get 11,700 hits, then I put in “asbestos toxicity” AND also
“lawyer” into the same search, and I get 11,500 hits (associate between lawyers
and asbestos cooties is WAY strong). Now
I put in “gasoline toxicity” alone and get 7,070 hits, v/s when I add “lawyer”
there, 7,070 drops WAY down to a mere 1,040 hits. What does that say to you? To me, the “Google” results-math is telling
me what I already know social-political-math wise: Lawyers have taken away our asbestos because,
well, because they can… And it gets them
power and money. And we collectively let
them get away with it, because we think only a few fat-cat special interests
are at stake anyway. They have NOT taken
away our gasoline away from us, only because they KNOW darn well that if they
tried, we’d start turning zealous, greedy lawyers into feed-stocks for
biodiesel!
What we
don’t pay enough attention to, though, is “How the Health and Safety NAZIs are
Killing Us”. (Someone PLEASE write a
book with that title?!?!) Asbestos was
NOT merely used to enrich corporate fat cats; it was used to improve health and
safety for large numbers of us mere non-fat-cats (AKA low-fat cats). Forthwith, some examples for you; the Health
and Safety NAZIs ARE yea verily killing us:
‘1) CFCs are bad, and so we will
eliminate them EVERYWHERE, even though we could safely help a LOT of people
with just a few VERY small exceptions…
Like Asthma inhalers. See http://www.cbsnews.com/8301-505123_162-42849822/fdas-cfc-asthma-inhaler-ban-becomes-a-light-bulb-issue-for-conservatives/
and http://www.savecfcinhalers.org/
… Classic case of, killed by the health
NAZIs! … ‘2) CFC case #2, http://www.dvorak.org/blog/2005/08/04/today-in-investors-business-daily-stock-analysis-and-business-news/
, a multi-billion dollar space shuttle, and seven astronauts, were killed by
the health and safety NAZIs, because NASA had to use “politically correct foam”
to insulate the fuel tanks, because one in ten trillion people might cough due
to CFCs used in the older, better, politically incorrect foam insulation. ‘3) Asbestos case #1, another shuttle (and
another 7 astronauts) was lost because NASA was too politically correct to use
enough asbestos to properly seal the o-ring seals on Challenger. (That one may not be true according to some
sources). ‘4) Asbestos case #2, the twin towers came down
in NYC on 9-11 because of some evil Islamofascist killers, as primary cause,
yes… But, those towers MIGHT still be
standing, had they been completed as originally designed, with
asbestos-insulated, TRULY “fire-proof” steel structures, not with inferior
materials. Speculative, perhaps,
yes… But, “Killed by the Health and
Safety NAZIs” is certainly not an entirely speculative rant. I have seen the statistic that the FAA spends
$100,000 to save a life, statistically speaking, while the EPA spends
$6,000,000,000 (!!!) to do the same! In
a rational world, we would adjust their budgets accordingly. But since preventing airplane crashes is
deadly boring, un-sexy work, and “environmental toxins” sounds like a horrible
boogey-monster that must be stopped at ALL costs, the politicians follow the
glamor and the press coverage, and we peons all get run over by giant
earth-hauling machines that are hauling “contaminated” soil from here to there,
that has two molecules of cooties per each 100 tons. I am wondering… If we have to dig up and use up 2 pounds of
asbestos in the effort to stop the next giant asteroid for creaming all human
life on the planet, will the lawyers, and the health and safety NAZIs, allow us
to do it?!!? Oh, well, back to
engineering…
OK, so,
then, I think we have thoroughly enough beat up the question of, HOW do we
sense (quickly and fairly simply) how far out of balance are we, and, in what
particular direction are we out of balance?
As we are spinning our turbine assembly around, of course. Electronic wizardry can fill in the details
(I volunteer if the budget and job security is superb!). Have EE, will travel!
Moving
on, then, the next question is, how do we efficiently, effectively, cheaply,
and without torqueing off the Health, Safety, and Environmental NAZIs, go and
CORRECT the spin imbalances that we have detected? Well, OK, we COULD have masses out there on
the outside of the spinning turbine assembly, on the lee (downwind) side of
externally-mounted “turbo-prop” blades, helical-screw-propelled, travel up and
down. Further out means more angular
spin momentum (more pull-out force).
That’s kinda slow-reacting, boring, un-sexy, methinks, on second
thought. It HAS yea verily now been
mentioned, so as to fend off the patent trolls, though! On to more ideas…
The
pushed-up and/or pulled-down (“up” is away from spin axis, “down” is towards
spin axis) masses could be water-filled, or other-liquid-filled, with tiny
little solenoids to open and close under electrical control, so as to as to
shed mass (in a controlled manner) to assist with the spin-balancing act. A one-time deal… When you have “shot your load”, you are
done… Hereby mentioned; patent trolls
begone, deal be done…
Along
similar lines, let’s mention the following:
Holes in the sides of the turbine could selectively be opened, to eject hot
gasses. Whichever side is bulging out
too far, that is the side where we want to eject hot gasses, to counter-act
against the imbalance. We could even put
micro-turbines in these side / outwards micro-jets, and use them as a source of
power for the control and activation electronics for this entire scheme. Speaking of power sources, how DO we power
this whole sense and control scheme? OK,
that particular list: Batteries,
micro-turbines, micro-waved or electro-magnetically coupled energies, fuels cells,
electricity-conducting contact carbon brushes from stationary onto rotating
surfaces, or even vibrations, or even temperature differences across surfaces
(see http://www.sciencedaily.com/releases/2013/02/130214075629.htm
for example). Patent trolls are hereby
further exorcised… Oh, PS, one could
simply put a fairly simple electromechanical generator on the spinning part of
the turbine, where it contacts the “stationary” body of the travelling jet /
rocket. That’s probably your simplest and most reliable source of electrical
power for the circuitry that is going to be needed, distributed around the
spinning part of the turbine, for most any practical active re-balancing scheme
(as here envisioned).
The
masses of the components of the control circuitry, measurement tube(s),
activators for the balance-restoring mass movements, etc., are all going to
have to be evenly distributed through the turbine body, so that they themselves
will not cause spin imbalances (with the obvious exception of the conductive
fluid itself, which we have to deal with as the price of fetching our
measurements). Pre-flight, before each
flight, after the refurbished pyrometric-ceramics-containing turbine blades are
installed, the spinning assembly would need to be pre-balanced with small
counter-weights, for fine-tuning, just like they do with your wheel and tire at
the tire shop. Then the aircraft /
spacecraft would be properly engine-spin-balanced for low-altitude flight, all
the way up till right before engine geometry starts to change.
And now
just a few words about high-temperature-tolerant circuitry, as will be needed
for any such scheme. See http://www.sciencedaily.com/releases/2012/06/120601103816.htm
; silicon carbide circuits can operate in temperatures up to 600 degrees Celsius. This type of circuitry should certainly help
to solve at least some of the problems here. For those hopefully-small remaining parts of
the circuitry that can NOT be met with silicon carbide, temperature-sensitive
circuitry could be encased inside compartments that are actively cooled, via
“heat pump” of some sort or another. Alternately, one active component at a time
can simply be mated, heatsink-style, to a thermoelectric component (cooler). One simple choice here would be to use the
“Peltier effect”; see http://en.wikipedia.org/wiki/Thermoelectric_effect
... These devices are reasonable
affordable and practical. The extracted
heat, extracted from the cooled chamber(s) or individual components, would be
dumped onto the turbine wall, and / or the ambient environment. A drawback to these kinds of devices is that
they are energy (power) hogs, but that should not be a significant drawback in
a power-rich environment such as an aerospace craft.
Then finally there is the electrical wiring
itself to be considered; how do we insulate it?
How about (if there’s nothing else that really does the job right)
asbestos? Maybe we can bribe all of the
lawyers and “health and safety NAZIs”…
Or maybe we can get Congress to pass special laws (like they did for the
small-aircraft industry) protecting this new industry here from the ravages of
the lawyers. If we have to gear up to go
up there & get ready to steer the next giant asteroid away from us, as I
think we should… Then, an engineer’s got
to do what an engineer’s got to do!
Then the next topic becomes, how do we move
masses around to control spin balance (correct spin imbalances)? As previously mentioned, we can put masses on
the lee (downwind) side of external “turbo-prop blades”. How?
Via linear actuator; http://en.wikipedia.org/wiki/Linear_actuator
has a good write-up as usual. Response
rates here might be a bit slow. Here is
another idea which could offer MUCH better response times, if experience in the
computer industry is any guide. Use a
much-larger version of the “voice coil” actuator and swing arm that positions
the read / write head in a hard drive, see http://en.wikipedia.org/wiki/Hard_disk_drive
.. Except in this case, we would keep
the powered actuator part of it embedded in the turbine wall, and the read /
write head would be replaced by a moderate-mass “hammer head” out at the end of
a fairly long swing arm. Position the
actuated “head” close to the turbine wall if you already have too much mass
(push-out force) there, and further out if you want more “pull out force” to
correct a lack of mass at that spot.
This would offer extremely good response rates, but would be a power
hog.
Here is what I consider to be a much better
idea (the best idea): Have multiple sets
of these(*) arranged around the turbine, at different orientations (different
“phases” or positions on the face of a clock, if you will). (*)“These” here means that at 180 degrees out
from each other, a hinged mass can swing out. Each mass is coupled, via cables,
to it’s one and only partner, which sits 180 degrees out from it, on the
opposite wall. For low-altitude flight
(dense air and no need for spin balancing), the coupled masses are held
embedded into the turbine wall (slack cable is retained, not allowing the
masses to fly out, which is what they “want to do”, due to centrifugal
forces). This prevents un-needed air
friction. At high altitude, right before
engine geometry changes begin, the slack cables are (slowly, to prevent sudden
changes or shocks to the system) released.
Probably also staggered release; one set of masses released at a
time. The weights, masses,
counter-balances, whatever you want to call them, now fly outwards, on hinges
that allow them to swing freely, but not fly loose.
Now the beauties of this approach start to
clarify: The two opposing weights
roughly balance each other, and the cables that run between them direct the
pull force of the one, against the other, providing a fairly neutral cable to
pull on, one way or the other, to enable an electric (or other) motor to
control one cable, which controls two masses.
The two masses do the exact opposite from one another, in terms of, are
they adding or subtracting from “pull-out-force”, which is exactly what we
want, since they are on opposite “faces of the clock”. And no, silly person, absolutely NOT, we do
NOT run the cables through the middle of the turbine, obstructing the flow of
hot gasses, we detour the “pull cables” around hollow “cable guides” contoured
around the outer periphery of the turbine wall.
If the aerospace plane is going to come back for a conventional landing
(descend back into dense air), it might be desired to add a feature enabling
“slack cable” to be created again (to pull both weights back into their
recessed cavities on the outside of the turbine wall).
A motor to pull the cable in on one side,
pulling that weight in, now allows the opposite weight simply to keep pulling,
as it always does, going further out.
But a motor requires more moving parts
http://en.wikipedia.org/wiki/Linear_motor
Which
then brings us to what I believe are the REAL optimal choices for the re-balance
activators: (cliff-hanger happens here; C Plus Ranger must return to my day
job). Meanwhile, back at the C Plus
Ranch…
Stay
tuned… RocketSlinger@SBCGlobal.net
Back to
main site at www.rocketslinger.com