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Патент USA US3099152

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July 30, 1963
H. GARTEN ETAL
3,099,141
SHAFT FOR USE IN NUCLEAR RADIATION ENVIRONMENT
Filed Nov. so, 1961
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United States Patent O ”
1
3,099,141
SHAFT FOR USE IN NUCLEAR ‘RADIATHÜN
ENVIBGNMENT
Herbert Garten and Robert Herman Schaffer, Cincinnati,
Ohio, assignors to General Electric Company, a corpo
ration of New York
Filed Nov. 30, 1961, Ser. No. 156,189
S Claims. (Cl. 64-1)
ßßgìldl
Patented July 30, i963
2
fins) integral therewith, the tin being in the form of a
helix having a predetermined angle and direction, the ratio
of the total fin mass to the total mass of the member,
excluding the iin, »also having a predetermined value,
wherein the fin acts as a load-transmitting member itself,
thus pr-oviding maximum load carrying capability with
minimum total shaft weight and heat generation in the
nuclear radiation environment.
>FIGURE l is a longitudinal view of the shaft, partially
in cross section, in combination with a nuclear radiation
This invention relates to a torque-transmitting member, 10
source;
and, more particularly, to a shaft for use in a nuclear
FlGURE 2 is a yview taken along line 2--2 of FIG
radiation environment wherein heat induced in the mem
URE
`l;
ber by radiation is substantially proportional to the mass
FEGURE 3 is a segment o-f a helical lin in cross section
of the member.
taken along line 3--3 in FIGURE 1 showing the relation
Recent studies have proven that nuclear flight at sub 15 ship of the depth and pitch of the tin; and
sonic, and possible supersonic speeds is feasible. These
FIGURES 4, 5, 6, 7, and 8 are 4graphical representations
studies have primarily been concerned with two different
of -certain parameters governing the design of the inven
avenues of approach for a nuclear powered aircraft jet
tion.
engine, namely, an “indirect” cycle and “direct” cycle con
Referring now more specifically to FIGURES l and 2,
20
figuration. In an. “indirect” cycle nuclear .turbojet air
indicated generally by -numeral il@ is a tubular member, or
craft engine the nuclear radiation source, or reactor is
shaft. The tubular member, or shaft is preferably of one
placed off to one side «of the engine and the conventional
piece construction and is adapted to transmit rotational
chemical combustion chamber heat source is replaced by a
force, or torque between a driving component and a driven
large radiator. The radiator is kept hot by a closed-loop
component (not shown). For example, in >aircraft ap
25
heat transfer system in which a flu-id is circulated through
plications the shaft may find use in a nuclear turbojet
the reactor and into the radiator and back to the reactor.
engine wherein in the usual manner one or more com
On the other hand, in the “direct” cycle configuration the
pressors are driven by one or more turbines downstream
reactor replaces the normal chemical `fuel combustion
of the compressor. As seen in the drawing, the shaft ex
chamber of the turbojet engine and the engine airiiow and
tends through a nuclear radiation field, in this instance, a
the compressor power shaft pass through the reactor. 30 reactor. The shaft is a hollow, preferably cylindrical,
Thus, a direct cycle nuclear turbojet engine may be de
seamless member, and includes a shell portion Ztl and a
scribed as an “in-line” engine, with the coupling shaft be
plurality of iin portions 5b. The shaft wall, or shell thick
tween the compressor section and the turbine section of
ness tS is preferably relatively small so that the shaft, for
the engine passing through the center of the reactor, or
a given diameter and length, can be more easily cooled.
35
nuclear radiation source.
As pointed out, when a metallic member, in particular,
As in the conventional chemically fueled turbojet air
is used in la nuclear environment Iit will be subject to
craft engine, the shaft must transmit both a torque load
nuclear radiation such that heat is lgenerated in the mem
and an axial -load. However, contrary to the situation in
ber, in this case the shaft lili. The heat so generated
the conventional engine where a nuclear heat or radiation
will be substantially proportional to the mass of the metal
40
source is not present, heat is lgenerated in -the shaft as it
in the member. While the mass MS of the shaft 10 has
passes through the reactor, the amount of which is sub
been significantly reduced by the descri‘oedV thin-walled
stantially proportional to the mass of the shaft. While
configuration, it will be apparent that with a given power
cooling air may be directed against the shaft in any one
transmission requirement a certain degree of structural
of a number of known ways, this may not be enough to
strength in the shaft will still be required. Thus, the
ofi-set the increased heating effect of the nuclear radia 45 problem, as stated, is to provide sufficient power, or load
tion. Thus, contrary to the normal application where
transmission capability (in the case of a turbojet engine,
there is no limitation against strengthening of the shaft by
torque load and axial load) with minimum weight in the
simply increasing its mass, or weight, in a direct cycle
nuclear radiation environment. Since a heavier shaft will
nuclear engine a heavier shaft will run hotter. This is
run hotter and since metallic materials, especially, lose
unacceptable because of fthe fact that the metallic mate
their `strength with increasing temperature, the wall thick
rials of which such shafts are usually constructed normal
ness fs cannot merely be increased.
ly lose their strength with increasing temperature. While
As is well known, while a smooth shaft generally is
it would -appear that the shaft could be strengthened mere
most efficient in carrying a load, a finned shaftv of an
ly by increasing its diameter, for a nuclear turbojet ap
equivalent tot-al mass will run cooler, thus raising the al
plica-tion this will be undesirable since any increase in shaft 55 lowable stress in the shaft. However, the actual stress in
diameter will be `accompanied by a significant increase in
commonly used finned shafts will be increased because the
reactor overall diameter. This, in turn, affects reactor
fins carry only an insignificant part of the load. This then
shielding requirements adversely, so that the net result is
raises the stress in the shell portion of the shaft as a result
an intolerable overall weight increase. The problem,
of the reduced masspthereof, since part of the original, or
therefore, becomes one of providing, in a nuclear environ 60 equivalent mass has been converted to tins. However, if
ment, a shaft capable of maximum torque, or power trans
the increase in the ‘allowable stress exceeds this increase
mission, the shaft being of `minimum diameter and weight,
in actual stress, the use of such lins may be justified. But
since increasing weight becomes self-limiting in the shaft,
fins can only be justified in an airborne application if they
it being clear that in any successful airborne application
do useful work, i.e., if they aid in power transmission.
65
the total system weight is of critical importance.
In other words, if lthe fins can be made to function as la
Therefore, an object of this invention is to provide a
shaft of minimum diameter and weight «for use with a
nuclear radiation source, which shaft has a configuration
`structural portion of the shaft and not merely as a means
for cooling the shaft, they will justify their use. Thus,
while it was known to provide a shaft with fins for the
minimizing nuclear heat generation and temperature in the
purpose of cooling, it was not, prior to the present inven
shaft, the shaft providing maximum power transmission. 70 tion, readily apparent that the addition of fins to a shaft,
'In one embodiment, the shaft of the present invention
which would seem at best a grossly inefficient way of in
comprises a hollow, cylindrical member having a iin (or
3
3,099,141
creasing shaft strength, could solve the problem of increas
ing the torque or load transmitting ability of a shaft in a
nuclear enviroment, without unduly increasing shaft di
ameter or weight.
Therefore, with a fixed shaft `diameter and length, fixed
flow rates and properties of the cooling ñuid utilized, if
any, and a fixed internal heat generation rate for the
nuclear radiation source through which the shaft must
4
design of the heat generation rise lbeing proportional to
mass increase will be examined. FIGURE 5, as Well as
IFIGURE 4, indicates that the iins can increase the «tern
perature margin (a corollary «of load-carrying capacity
in a nuclear radiation environment) significantly with
predetermined increases in the MF/MS ratio within a
certain range of values. Thus, by selecting an optimum
value for the shaft weight, a maximum temperature mar
pass, the inventors have devised preferred embodiments
-gin may be obtained. In the example given for a shaft
of the shaft determined by such parameters as the shape
of the iin, or fins, 3€), the angle of the helix formed by 10 weight of 3 units, chosen as an optimum Ifor a smooth
(unfinned) shaft, the best value of MF/MS is .5 since it‘ï
each iin as it spirals internally of the shaft along the
provides the greatest temperature margin (140°). It will
shaft length, the direction of the helix, the :total shaft
be noted that increasing the fin mass beyond a certain
mass Ms, and the total iin mass MF. The relationships
point will not raise the load-carrying capacity significant
yof these parameters are utilized to attain maximum shaft
ly, even when the shaft Weight is increased, since with
power transmission capability and minimum weight in a
too large a fin the resultant increase in shaft shell stress
nuclear environment. Briefly, the inventors have `opti
necessitates “beeiing-up” the shaft to the point where, in
mized the iin helix angle 0 and the ydirection of the helix
'in order that the iin carries as much of the loads as pos
sible, thus minimizing the effective stress on the shell.
a nuclear radiation Íiel'd, the resultant temperature rise
so weakens the material strength as to overcome the effect
Also optimized is the thickness of the shell so that too 20 of the added weight. This, as pointed out, is not a prob
lem in a non-nuclear environment. Also, as seen in the
small a thickness is avoided, since stresses would be too
graph in FIGURE 5, the increase in MF/MS from .5 to
high, and to‘o great a thickness is avoided, since with the
high temperatures of a nuclear heating environment, an
undue increase in the thickness would cause such a de
1.0 accomplishes something less than the increase from
0 to .5. This indicates that for very large values of the
eline in the material properties as would over-balance the 25 ratio MF/MS, the full cooling effectiveness will not be
attained, and, further, stress concentrations may become
reduction in stress and, although “beefed-up,” the shaft
a limiting factor. Therefore, optimization of the finned
would actually «be less safe. Moreover, the shape and
shaft load-carrying capability for a desired minimum
vangle of the ñns is chosen so as to minimize or eliminate
may be accomplished by use of the graphs in FIG
the effects of manufacturing tolerance variations in the 30 »weight
URES 4 and 5. By choosing a desired torque load-carry
nuclear environment, i.e., uneven heating which may cause
ing capacity (or temperature margin) and representing
shaft bowing, or arcing.
_,
it
as the ordinate of the graph, the abscissa may then
In describing how the shaft is designed to achieve lthe
represent
the desired range of values -for shaft weight.
desired load-carrying capability with any given shaft di
ameter in an application requiring minimum weight, par* 35 Curves for various ratios of t-he total fin mass to the total
shell mass -MF/MS-can then be plotted. The first
ticular reference is made to FIGURES 4 through 8. FIG
URE 4 illustrates a parameter affecting the l-oad-carrying
capability of the member 1G. In the graph, the torque
curve intersected by a horizontal line drawn at the de~
(MF/M520). In this instance the torque load-carrying
is a mechanical rather than a thermal parameter, i.e.,
since the ratio is the total amount of fin material to the
total amount of shell material, it deals only with the load
sired torque load (or temperature margin) specifies the
lightest shaft for the `given conditions. The inventors have
load~carrying capacity is plotted as a function of the
shaft weight Áfor several values of the ratio of the total 40 determined that the preferred value for the ratio MF/MS
-will lbe greater than .2 but :less than 1.5 for aircraft nuclear
of ñn mass MF to the total shaft mass Ms. To
turbojet engine applications.
understand the significance of the curves, first consider
It should -be understood that the iin ratio just discussed
the curve Where the shaft is smooth, =i.e., there are no ñns
capacity is low in the nuclear environment for either a
light or heavy shaft, altho-ugh somewhat greater for some
intermediate Weight.
The reason for this is that an ex
tremely lightweight shaft is is easily cooled because the
shaft wall is relatively thin. However, depending on the
»carrying capacity of the fin member. On the other hand,
the best thermal iin ratio, which is defined here as the
ratio of the total surface area of the ñn and shell portion
combined, to that of the surface area of a comparable
extent of the thinness there may not be enough shell ma 50
smooth surfaced cylinder of equal diameter, obviously
terial to carry the torque load for a particular applica
will 4depend somewhat upon the amount and properties
tion so that the shaft thickness, and the Weight, may nec
of the cooling fluid utilized, if any, in the particular ap~
plication. In a nuclear radiation environment, larger
cline comparatively slowly. Thus, additional material in 55 thermal fin ratio values will reduce shaft iinv temperature
very effectively. However, the shell temperature will be
creases the load~carrying capacity and the curve in FIG
essarily have to be increased. At ñrst, `cooling will still
be reasonably effective and the material strength will `de
reduced yonly slightly, so »that the reduction in shell tem
URE 4 will rise. As the shaft thickness is increased still
perature
is more than offset by an attendant increase in
further in a nuclear radiation environment, however, «the
shell stress. The increase in thermal fin ratio virtually
cooling becomes less effective and the shaft operating tem
necessitates a simultaneous increase in MF/MS which
perature rises rapidly. This ydrastically reduces the ma
terial strength the result being that the shaft is weakened 60 causes the attendant increase in shell stress. Thus, with
the present invention, where »the ñns are provided with
Ifaster than the additional material can make up the
a load or torque carrying capability, it has been found
strength, causing the load-carrying capacity to fall again.
that the optimum thermal ratio, as defined, which results
'Dh-us, for a given application (or temperature margin, in
is preferably on the order of approximately two to one.
a nuclear radiation environment) one particular shaft
Refenring now to FIGURE 6 shown therein is one
thickness will produce the strongest shaft. The curves 65
effect of differences in the value of the fin helix angle 0
in FIGURE 4 are therefore characterized by a downward
on the shaft load-carrying capacity. It will be noted that
concavity. If the shaft is then provided with fins, for the
for pure torque loads Ian tangle of appnoximlately 45° is
reasons'given above, the curves for different values at
MF/MS will still be characterized by a `downward con 70 best, although it is not critical. For a shaft which carries
la «combination of axial and torque loads, suc-h as in an
cavity.
aircraft tumbojet, the `curves in [the FIGURE 6 indicate
Considering next the relationship between the curves,
that the .angle is optimum ‘between 30° and 55°. How
since, as stated above, the problem is one of obtaining
ever, it was ldetermined that to avoid the effects of un
the greatest load-carrying capacity in the peculiar en
balance due to thermal bow of the shaft in the nuclear
-vironment of a nuclear radiation source, the effect on shaft 75
radiation environment, which causes one surface of the
3,099,141
shaft to experience a greater temperature rise than the
other, thus causing the shalt centerline to arc longitudi
nally, each lin should spiral at least one complete revolu
tio-n. Thus, the angle of the helix is also dependent on
the relationship of the diameter to the length of the shaft.
The optimum value of the angle 0 was therefore deter
6
the member is substantially proportional to its mass, said
member comprising:
a hollow, cylindrical shell portion, said shell portion
mined to depend primarily on two parameters. One of
these is the ratio of the diameter D times the axial load F
to the torque load T, Ior D ><F/ T. For values of D XF/ T
less than 3, the optimum value «of 6 is between 30° and 10
transmitting a part of ysaid load and having a total
mass MS;
a lin integral with said s‘hell portion, said iin comprising
.a helix extending the length of the shell portion and
having a total mass MF,
wherein the ratio of `the iin mass to the shell mass
M F/MS-is greater than .2 but less than 1.5,
so as to enable said lin to transmit the remaining part
of said load at la minimum total weight lof said mem
55°; tor values of DXF / T greater than 3, the optimum
value of 0 is from 0° to 30°. This is shown graphically in
ber in said nuclear radiation environment. `
FIGURE 7. However, the value of 0 must also be such
2. A load transmitting member tor use in a nuclear
as to insure that the relationship of the shaft diameter D
radiation environment wherein the »temperature rise in
to its length s permits each iin, `or helix to make approxi 15 the member is substantially proportional to its mass, said
mately ione complete revolution. Thus, changes in D, in
member comprising:
DXF / T, will «also aiîect the relationship of D to s.
la hollow, cylindrical shell portion, said shell portion
Further, «the direction ot a fin, or helix in a shaft will
transmitting «a part of said load;
be found to coincide gene-rally with :the direction of the
a -tin integral with said shell portion, said iin compris
20
maximum torque load. Tor maximum torque load-car
ing ‘a helix extending the length of the shell portion
rying capacity in the nuclear environment it has been
rand having a height d »and a pitch p,
found that, additionally, the ‘direction of the helix should
wherein the ratio of the liin height to the tin pitch
be such that the torque load tends to tighten the spiral, thus
d/ p-is greater than .1 but less than 2.0,
putting the tins in tension, and increasing the load-carry
25
ing capacity of the shaft.
Finally, the :graph in FIGURE 8 illustrates the rfact that
the tin shape must also be taken into consideration when
optimizing the sha-ft and Íin torque load-carrying capacity.
so 4as to enable said lin to transmit the remaining part
of lsaid load at a minimum total weight ot said mem
ber in said nuclear radiation environment.
3. A load transmitting member for use in a nuclear
radiation environment wherein the temperature rise in
In >FIGURE". 3 the conñguration of the llin is depicted in
the member is substantially proportional to its mass, said
terms of the relationship of the height, or depth of the 30
member
comp-rising:
1in d to the pitch of the helix p. With a lin «ilank angle
la hollow cylindrical shell portion, said shell portion
«of approximately 15°, or in the range `from 5° to 30°,
transmitting a part of said loading and having a total
and a substantial ñllet approximately equal to the shell
mass MS,
thickness at the base of the lin, to reduce stresses, the
la fin integral with said shell portion, sai-d fin comprising
iin shape which combines the best heat transfer 0r cool 35
a helix extending the length of the shell portion and
ing properties with mechanical strength tor load-carrying
having `a height d and a pitch p,
capabilities will have a configuration substantially as »that
wherein the ratio lof the lin height to the iin pitch
show-n in FIGURE 3. In the embodiment shown the lin
d/p-is greater than .l Ibutless than 2.0,
slenderness ratio
land wherein »the ratio «off the lin mass to the shell mass
40
MF/MS--is greater than .2. but less than 1.5,
for maximum load-carrying capacity is approm'rnately .3;
so ‘as to enable said lin to transmit the remaining part
«of said load at a minimum total weight of said mem
ber in said nuclear radiation environment.
4. A torque load transmitting member tor use in a
but, in any event, in the range from .1 to '2.0. This ran-ge 45
nuclear radiation environment wherein `the temperature
will also give the greatest íin cooling effectiveness with a
rise in the member is substantially proportional to its
maximum strength and minimum weight in the nuclear
mass, said member comprising:
environ-ment.
a hollow, cylindrical shell portion, said shell portion
Thus, the inventors have provided a new land useful
torque and axial load-transmitting member `ior use in a 50
transmitting a part of said load;
nuclear radiation iield wherein the heat Vgenerated in the
member, as a result of nuclear heating, will be substan
tially proportional to the mass thereof. The member has
a hollow shell yand helical ñns integral with either the outer
surface of the shell, or lthe inner surface of fthe shell, or 55
both. Further, the helix direction is to be determined
by vthe direction ‘of the torque load, ‘and the preferred
value of .the ratio MF/MS is greater than .2. but less than
1.5, the preferred angle of the helix is greater than 30°
60
but less than 55°, the value of the ratio
d
P
a fin integral with said shell portion, said lin comprising
«a helix extending the length of the shell portion -and
having a height d and a pitch p land an angle 0;
wherein lthe natio of the tin height to the iin pitch
d/p--is greater than .l but less than 2.0,
and wherein the direction fof the helix is such that
twisting in said member due to the torque load will
tend to tighten said -an-gle 0 of the helix,
so las to enable said tin to transmit the remaining part
of said load lat a minimum total weight of said mem
ber in said nuclear radiation environment.
5. A torque and axial load transmitting member for
use in a nuclear radiation environment wherein tempera
ture rise in the member is substantially proportional to
(as lmeasured perpendicul-uar to the lin helix angle) is 65 its mass, said `member comprising:
a hollow, cylindrical shell portion, said shell portion
preferably greater .than .1, but less than 2.0, with the lin
proportioned in la manner so that its flank angle is greater
than 5° but lless than 30°, and the thermal iin ratio is
approximately 2 to l, in order that the shaft will provide
maximum power transmission with minimum ‘overall 70
weight in the nuclear radiation lield.
What we claim and desire to secure by Letters Patent
1s:
1. A load transmitting member -for use in a nuclear
radiation environment wherein the temperature rise in 75
transmitting a part of the axial load F and the torque
load T, said shell portion having a ldiameter D;
a tin integral with said shell portion, said iin compris
ing a helix extending the length of the shell portion;
wherein the angle of said helix is such that when the
value of the ratio DXF/T is less than 3, the op
timum helix angle will be -greater than 30°, but less
than 55°, and 'when the yvalue of the ratio is greater
than 3, the optimum helix angle will be less than 30°,
3,099,141
so as to enable said iin to transmit the remainder of
said loads F and T at a total minimum weight of said
wherein the angle 9 of said helix is such that said iin
makes at least one complete revolution of said cylin
member in said nuclear radiation environment.
6. A torque and axial load transmitting member for
drical shell portion along said length s,
use in a nuclear radiation environment wherein tempera
ture rise in the member is substantially proportional to 5
its mass, said member comprising:
a hollow, cylindrical shell portion, said shell portion
transmitting a part of the axial load »F and the torque
so as to enable said ñn to transmit the remainder of
load T, said shell portion having a diameter D and
a mass MS;
and wherein the angle 0 of said helix is such that when
the value of the ratio DXF/ T is less than 3, the op
timum helix angle will be greater than 30°, but less
than 55°, and when the value of the ratio is greater
than 3, the optimum helix will be less than 30°,
10
said loads F and T at a minimum total weight of said
.
.
.
.
member I1n said nuclear radiaiton environment.
a iin integral with said shell portion, said iin comprising
a helix extending the length of the shell portion and
8. A torque and axial load transmitting member 'for'
use in a nuclear radiation environment wherein tempera
having a -mass MF;
'
ture
rise in the member is substantially proportional to
wherein the angle of said helix is such that when the 15 its mass,
said member comprising:
value of the ratio D XF/ T is less than 3, the optimum
a hollow, cyl-indrical shell portion, said shell portion
helix angle will be greater than 30", but less than 55 °,
and when the value of the ratio is greater than 3,
the optimum helix angle will be less than 30°,
transmitting a part of the axial load F and the torque
load T, said shell portion having a diameter D;
a iin integral with said shell portion, said fin compris-
and wherein the ratio of the `iin mass to the shell
mass-MF/MS--is greater than .2 but less than 1.5,
so as to enable said lin to transmit the remainder of
said loads F and T to a total minimum weight of
said member in said nuclear radiation environment.
7. A torque and axial load transmitting member ‘for
use in a nuclear radiation environment wherein tempera
25.
area of an unfinned load transmitting member of
ture rise in the member is substantially proportional to
its mass, said member comprising:
equal diameter D, is approximately 2,
e
so as to enable said 1in to transmit the remaining part
of said loads F and T at a minimum total weightv
a hollow, cylindrical shell portion, said shell portion
transmitting a part of the axial load F .and the torque
load T, said shell portion having a diameter D;
a iin integral with said shell portion, said iin compris
ing a helix extendingr the length s of the shell por
tion and having an angle 0;
ing a helix extending the length s of the shell portion
and having a height d and a pitch p;
wherein the ratio of the iin height to the tin pitch
d/p-is greater than .1 and less than 2.0,
and wherein the ratio of the total surface area of the
iin and shell portion combined to that of the surface
30
of said member in said nuclear radiation environ
ment.
No references cited.
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