Note: Descriptions are shown in the official language in which they were submitted.
,
The present invention is concerned with a
thermal power machine and a method for converting
thermal energy to mechanical energy, wherein
a member of metal alloy contained in it is heated to
a certain temperature, whereat its physical properties,
in particular its elastic constant, are changed and
this physical change is used as the drive power of the
thermal power machine. The invention is also concerned
with equipment for converting thermal energy to
mechanical ener~y, the said equipment comprising a
thermal power machine which includes one or several
lS metal alloy members, which change their physical pro-
perties, in particular their elastic constant, at a
certain temperature, whereat this physical change pro-
vides the thermal power machine with drive power.
Several metal alloys are known in which the
so-called memory phenomenon occurs. The patent claims
refer to all of these so-called "memory alloys". One
of such "me~ory alloys" is an alloy of titanium and
nickel, known by the name Nitinol*. After an object
of such a material has been brought to a certain shape
by means of an appropriate heat treatment, it always
tends to return to this shape when it is heated to its
transition temperature. On the contrary, below its
transition temperature, the material is readily
deformable. Thereat, the material can be deformed by
means of a substantially lower force as compared with
the force that is generated by it at a higher temper-
ature when it retuns to its heat-treated shape. The
; transition temperature can be adjusted by varying the
composition of the alloy, and it may vary within the
35 range of about -90C to 150C, most commonly about
40 to 90C.
.
~ * (Trade mark)
~,
.
126~63~
.
-- 2 --
Different applications of thermal power
machines are known that are based on the ability
of Nitinol to convert thermal energy to mechanical en-
ergy. One thermal power machine of this sort is described
in the U.S. patent 4,275,561 ~Finnish patent application
no. 79-2398). The apparatus described therein is based
on the tendency of a Nitinol loop t~ becorne straight
at a temperature of, e.g., about 50C. When such a loop
has been fitted around two wheels placed side by side
and when one of the wheels is heated, e.g., by keeping
it in warm water, the Nitinol loop tends to be
straightened and to move at this wheel, making the wheel
revolve by means of friction. The power can be taken
out of the apparatus from the shaft of the unheated wheel.
Such an apparatus has proved highly reliable and durable
in operation.
Thermal power machines have also been developed
that are based on easy extensibility of a Nitinol wire
below the transition temperature and on the force gen-
erated by its shrinkage at the said temperature. Sucha reversible elongation in the case of Nitinol is about
6 per cent. The power re~uired for extending is consid-
' erably lower than the force generated by the shrinkage.
Applications in which the shrinkage force is used for
rotating a crankshaft, which again extends Nitinol el-
ements, have been described in the U.S. patents 3,937,019
and 4,086,769.
The object of the present invention is to pro-
vide further applications for the conversion of thermal
energy to mechanical energy by means of a memory alloy.
According to the present invention, there is
provided a thermal power machine for converting thermal
energy provided from a heat source to mechanical energy
comprising at least one oblong metal alloy member being
Trademark
~;26~636
-- 3
provided in a predetermined length which expands below
a predetermined temperature and contrac-ts to the prede-
termined lengt~ at-a certain transition temperature set by a
composition of said alloy member, said member being stretchable below
the predetermined temperature, wherein the machine is provided
with a heat exchange cooling face ! the metal alloy member
being alterna-tely brought into and out of contact with
the cooling ~ace while the metal alloy member moves.
Thusj the internal energy of the metal alloy
can be converted to mechanical energy with maximum effi-
ciency by using the heat energy supply of an external
medium as the primary source of anergy. In appropriate
circumstances, the machine may operate so that it does
no-t require an external electric mo-tor or combustion en-
gine at all. In such a case, the machine can be applied,e.g., as a motor for a boat or for a ground vehicle, which
is independent Erom distribution and supply of energy.
The machine is completely free from pollution, because
no combustion waste is produced in the form of solid par-
ticles or gases, nor does it produce noise.
Preferably, in accordance with the invention,there is provided a thermal power machine for converting
thermal energy to mechanical energy, the said thermal
power machine comprising two or more oblong metal alloy
members placed side by side, which members change their
length at a certain temperature to a certain length that
was given to them earlier and which members are, at lower
temperatures, relatively easily extensible, whereat the
said metal alloy members are, at one end, attached pivot-
ably and eccentrically to a rotary member revolving arounda shaft perpendicular to the said metal alloy members,
and the shrinkage of the metal alloy members causes a
movement of rotation of the rotary member while the rotary
member, at the same time, extends a second metal alloy
,
~Z6~L~i36
- 3a -
member, characterized in that the other end of the metal
alloy members is also attached pivotably and eccentrically
to a second rotary member revolvlng around a shaf-t per-
pendicular to the said metal alloy members.
According to the present invention, there is
also provided a combination of a thermal power machine
; and a heat pump, the thermal power machine including a
metal member having physical properties which change de-
pendent on temperature of said metal member, the ¢hange
of the physical properties providing a driving power out-
put from the thermal power machine, the heat pump con-
nected to the thermal power machine so that said metal
member is heated by a heat containing medium external
of said heat pump and transferred by said heat pump to
sai.d metal member, the thermal power machine driving -the
heat pump by means of mechanical energy ~enerated by the
thermal power machine, comprising a pair of metallic heat
exchange faces provided in the thermal power machine,
one of said faces heated by the heat transferred from
the heat pump, the other of said faces having a lower
temperature than said one face, said metal member posi-
tioned between said pair of faces so as to alternatingly
contact said pair of faces, the metal member being pro-
vided in a predetermined length which e~pands below a
predetermined temperature and contracts to the predeter-
mined length upon an increase in the temperature.
The invention and its specific features will
be described in more detail in the following with refer-
ence to the attached drawings, wherein
Figure 1 shows an operational diagram of a ther-
mal power machine based on -the deformation of a memory
alloy,
Figure 2 shows the use of a thermal power ma-
chine in itself known in the equipment in accordance with
L636
- 3b -
the invention,
Figure 3 is a schematical presenta-tion of the
use of an equipment in accordance with the invention as
a power machine for a vessel,
Figure 4 is an axonometric view of a particular
embodiment in accordance wi-th the invention of a memory-
alloy thermal power machine,
Figure 5 is a cross-sectional view of the equip-
~ ment shown in figure 4, ~
,: /
'~ /
~ /
.63~
Figure 6 is an axonometric view of a second
particular embodiment of a memory-alloy thermal power
machine,
Figure 6a is a sectional v:iew of the Nitinol*
wire used in the apparatus shown in Fig. 6,
Figure 7 is a sectional view of the apparatus
shown in Fig. 6,
Figure 7a shows a detail of Fig. 7,
, Figure 8 is a schematical presentation of the
connecting of the apparatus shown in Fig. 6 with a heat
pump,
Figure 9 shows an alternative wiring diagram
for the connecting of the apparatus shown in Fig. 6
with a heat pump,
Figure 10 shows a detail of an additional
improvement of the apparatus shown in Fig. 6, and
Figure 11 shows the heat exchanger faces of
the apparatus shown in Fig. 9, as viewed i.n the
direction of the Nitinol*strip.
Like for all thermal power machines, an
operational diagram can also be derived for a machine
based on the deformation of a memory alloy. Now, it
is, however, purposeful to replace the pressure-volume
system of coordinates by a stress-elongation system
of coordinates. Such an operational diagram is shown
in Fig. 1, wherein the x-axis illustrates the elon-
gation (or compression) of the material and the y-axis
illustrates its stress. The principle of operation
shown in Fig. 1 will be described in the following.
Step 1: The material is deformed at a tem-
perature lower than the transition
temperature.
Step 2: The temperature of the material rises
and reaches the transition temperature.
Step 3: The deformation of the material is
returned to the original form.
Step 4: The temperature of the material is
* ( Trade mark)
~iL26~36
lowered to a level below the transi-
tion temperature. Hereupon/ s-tep 1
takes place again.
In view of the efficiency of the operation of
the machine, the important steps are step 3, wherein the
machine performs the mechanical work, as well as step 2,
wherein the machine receives the quan-tity of heat re-
quired by the change in phase.
The following is known about the opera~ion
of the machine:
1. For a machine operating by means of the
loop principle, an efficiency of 7 ~ 2 per
cent has been obtained within the range of
25 to 60 experimentally.
2. The machine is not a Carnot machine. By
means of calculations, it can be established
that the efficiency of the machine is better
than the efficiency of the Carnot process
of circulation.
3. The quantity of heat required for the change
in phase is 4150 joules per mole.
;~ 4. The other necessary physical properties are
known sufficiently accurately so that it
has been possible to perform the calcu-
lations of the order of magnitude.
Figure 2 shows an equipment in accordance with
the present invention, in which a thermal power machine
1 operating by means of the loop principle, in accord-
ance with the U.S. Patent 4,275,561, is utilized. The
thermal power machine is provided with two wheels 2 and
3 fitted side by side, around which one or several
parallel Nitinol* loops 4 are fitted. The smaller wheel
3 is placed in a medium tank 5 covered by a layer of
-~ thermal insulation, the medium, e.g. water, in the said
tank 5 being heated by means of a heat pump 6. The
heat pump is coupled by means of an appropriate trans-
mission (not shown in the drawing) with the shaEt 7
* (Trade mark)
~26~63~
of the larger wheel 2 in the thermal power machine 1.
Moreover, an auxiliary motor is connected with the heat
pump, which motor may be either a combustion engine or
an electric motor (not shown in the drawlng).
When the heat pump 6 is started by means of
an auxiliary motor, the pump transfers heat from the
medium surrounding the pump into the medium in the
tank 5. Heat is conducted from the medium in the tank
5 to the wheel 3 of the thermal power machine 1 and to
the part of the Nitinol loop 4 surrounding the wheel 3.
When the temperature of the Nitinol* loop reaches its
transition temperature, e.g. 50C, it tends to become
straight, whereat the wheel 3 starts revolving. The
movement is transmitted further to the wheel 2, from
whose shaft 7 the power is taken off. Part oE the
power obtained from the shaft 7 is used for driving the
heat pump 6, but all of the output power is not needed
for this purpose. The excess of the power may be used
for any desired purpose.
In stead of an auxiliary motor, the starting
may also be performed by means of an auxiliary heater,
operating, e.g., by means of electricity or fuel. In
such a case, the medium in the tank 5 is first heated
to the transition temperature by means of the auxiliary
heater, which can be turned off thereinafter.
Fig. 3 shows an embodiment for the utilization
of the mechanical energy in this way produced. The
thermal power machine 1 and the heat pump 6 are fitted
on a boat 8. The heat pump transfers heat from the
surrounding water 9 through a pipe system 10 into the
water tank associated with the thermal power machine,
keeping the temperature of the water contained therein,
e.g., at about 50C. Some of the energy generated by
the thermal power machine is distributed for the drive
` 35 of the heat pump and some of it for driving the
propeller 11 of the boat.
* (Trade mark)
636
Figures 4 and 5 show an alternative embodi-
ment for the thermal power machine 1 operating by means
of the loop principle shown in Fig. 2. This embodiment
comprises a medium tank 5 between whose side walls
several spring-like Nitinol* strips bent to an arc form
are attached by means of compression springs 15. Every
other strip is bent downwards and every other upwards.
To the middle of each strip, a connecting rod 13 is
; attached whose opposite end is attached rotably to a
crankshaft 14, alternatingly to its opposite crank parts.
When the temperature in the tank 5 rises to
the transition temperature of the Nitinol* strips, the
downwardly bent strips 12, at their transition temper-
ature, tend to be straightened to the position that was
given them in the heat treatment. Thereby, the con-
necting rods 13 start rotating the crankshaft 14. When
the strips become straight, they rise out of the medium.
At that time, no more thermal energy is transferred to
them. When they cool down, they again become flexible,
and the connecting rod 14 causes them to be bent upwards
this time. At the same time, the strips that were
originally bent upwards, have been forced to be bent
downwards, and they come into contact with the warm
medium. Thereinafter they again convert some of the
thermal energy contained in the medium to kinetic energy.
The transfer of heat to the Nitino~ springs
in the apparatus shown in Figures 4 and 5 can take
place either out of a liquid of low surface tension or
out of a heating contact face or as any other energy
impulse, e.g. by means of electricity, heat radiation,
or laser. In the springs, it is possible to make use
of the resonance phenomenon.
In apparatuses in accordance with the inven-
tion, constructions of low weight are obtained, and
possible materials are, e.g., nylon, fibreglass, etc.
The temperature of operation of the apparatus may be,
e.g., 40C. Machines can be built in view of ma~.ing
* (Trade mark)
~Z6i~.3~
them best suitable for certain temperature circum-
stances to be determined separately.
The medium from which, according to the
invention, energy is transferred by means of a heat
pump may be, e.g., soil, water or air.
In the embodiment shown in Figures 6 to 8,
Nitino~ wires 21 of flat cross-section have been fixed
by means of articulated joints between two crankshafts
24 placed side by side symmetrically to each other. At
temperatures below their transition temperature, the
Nitinol wires are readily extensible, but when the
temperature rises to a certain value, they shrink back
to their original length.
In the apparatus, there are two chambers 22
and 27 between the crankshafts, placed one above the
other. The chambers 22 and 27 are provided with
rnetallic heat exchange faces 23 and 26 facing each
other, the distance between the said faces being equal
to, or smaller than, the diameter of the path of move-
ment of the crankshafts 24. Fig. 7a is a more detailedview of the construction of the lower heat exchanger
face, as a section in the longitudinal vertical plane.
It is provided with channels 32 placed side by side
for the pipe system of the heat pump. Between the
channels 32, in the top face, there are grooves 33 for
the Nitino~ wires 21~ The construction of the upper
heat exchanger face 26 is similar, except that the
wire grooves 33 are placed at the bottom face. ~lost
appropriately, the heat exchanger faces 23 and 26 are
convex towards each other in such a way tha-t, in the
middle portion, the distance between them is shorter
than the diameter of the crankshafts.
Between the heat exchanger faces 23 and 26,
there is an insulation layer 28 in which there are
vertical grooves parallel to the grooves 33. Most
appropriately, the insulation layer 28 extends to all
sides of the chamber 27. The apparatus is enclosed
* (Trade mark)
~ ~;26~E;3~i
in a steel box 30, out of which the medium has been
removed as completely as possible close to the vacuum.
The heat pump 6 is connected between the
pipe systems 32 in the heat exchanger faces 23 and 26
so that it transfers heat from the upper heat exchanger
face 26 either to the environment or to the lower heat
exchanger face 23. The medium present in the lower
chamber 22 may be additionally heated by means o~ an
; external source of heat 34, or, e.g., waste heat from
1~ a nuclear power plant ~water of about ~50C) may be
passed into ito An external source of heat is, however,
not necessary if the heat pump 6 trans~ers heat from
an outside medium, e.g. from t4C water surrounding it,
to the lower heat exchanger face 23.
When the lower heat exchanger face 23 is
heated, the Nitinol* wires in contact with it are heaked
to their transition temperature. On reaching their
transition temperature, the Nitinol wires shrink and
make the crankshaft 24 cranks at the lowest position,
to which the wires 21 are attached, pull themselves
~ towards each other, whereat the wires 21 rise apart
- from the face 23 and start cooling down. At the same
time, the Nitinol*wires that are attached to the
; crankshaft 24 cranks in the upper position and in con-
tact with the upper cooling face 26 are extended as
the crankshafts revolve in opposite directions. The
movement goes on further so that the wires that were,
at the initial positio~, in contact with the heating
face 23 come into contact with the cooling face 26 and
are at that stage cooled efficiently. Thereinafter,
the same movement is repeated after the wires have
exchanged their positions. After the apparatus has
been started, the crankshafts revolve constantly sym-
metrically in opposite directions and the Nitino~ wires
are alternatingly shrunk when reaching contact with the
face 23 and extended as being extended by the crank-
shafts 24.
* (Trade mark~
.~.~i.~
~69L~3~;
1 0
The output powers W1 and W2 of the shafts 24
can be combined by means of a common loading shaft (no-t
shown in the figures) Part (W3) of this power can be
used for driving the heat pump, whereat the net power W4
is obtained for any other, desired purpose.
If necessary, the position o the crankshafts
24 may be adjusted by shifting the shafts in the
directions x and y denoted in Fig. 7. The apparatus,
of course, also operates so that the lower face is the
cooling face and the upper face the heating face. In
such a case, the crankshafts revolve in the opposite
direction. Of course, it is also possible to place the
entire apparatus so that the wires 21 are not in the
horizontal direction.
According to the invention, it is preferable
to use a minimal difference in temperature between the
faces 23 and 26. In such a case, the loss of heat is
at the minimum and, correspondingly, the efficiency of
the Carnot pump used for heating the face 23 and for
cooling the face 26 is at the maximum.
It is also possible to use several thermal
power machines as connected in series so that each
machine operates at a slightly lower transition temper-
ature relative the preceding machine. In such a case
it is possible to make use of very little differences
in temperature between adjoining temperature ranges.
Depending on the circumstances, it is also possible to
utilize just some smaller portion out of such a series.
The output P of the thermal power machine
described in Figures 6 to 8 can be calculated theore-
tically. When the following values are used:
o ~rest length of Nitinol* wire) 5,000 mm
r (radius of Nitinol* wire) 1 mm
R (radius of crankshaft) 25 mm
n (speed of rotation of crankshaft) 300 rpm
z (number of Nitinol*wires) 100
; ~K (internal diff. in temp. of machine) 1 to 3K,
* (Trade mark)
J ~
:~IL261~3~
1 1
as the output is obtained P 150 kW (without heat pump).Max. torque per wire is then 150 Nm.
Fig. 9 shows schematically how the liquid
cooled in the evaporator of the heat pump 6 is circulated
first via the heat exchanger 27 prov:ided with a cooling
face, whereat the temperature of the cooling face is
lowered efficiently. It is only thereinafter that the
liquid is passed through the medium 9 used as the source
of heat, where its temperature rises to the same level
with the temperature of the medium 9. Thereupon the
liquid circulates back to the evaporator of the heat
pump, where it delivers heat.
The liquid passing through the heat exchanger
22 provided with a heating face is circulated through
the condenser of the heat pump 6, where it is heated
and thereby lceeps the temperature of the heating face
sufficiently high.
Figures 10 and 11 show an additional improve-
ment for the apparatus shown in Figures 6 to 8. In the
2Q apparatus, flat, band-shaped Nitinol*strips 21 are used,
whose width is, e.g., about 10 mm and thickness, e.g.,
about 0.25 mm. The length of a strip may be, e.g.,
100 cm. Rods provided with articulated joints are
attached to the ends of the strips. The strips are
fitted so that the long side of their cross section is
placed vertically. Fig.10 shows one end of a Nitinol*
band as well as the articulated rod related to it and
the crankshaft 24. The articulated rod consists of two
parts 35 and 36 connected to each other by means of an
articulated joint 34. One end of the rod 35 is
attached pivotably to the crankshaft 24 and the other
end of the rod 36 is attached permanently to the Nitinol*
strip 21. Above and underneath the rod 36, there are
stops 37 whose distance from each other is shorter
3S than the diameter of the path of movement of the crank-
~ shaft 24.
* (Trade mark)
, ~,,
. . " . .
~2~ 3~
12
Fig. 11 shows the heat exchangers 22 and 27
used in the embodiment of Fig. 10. Each heat exchanger
consists of two parts, ~hich are attached to the frame
of the heat exchanger by means of hinges 38. In the
closed position of the heat exchanger, a slot remains
between the opposite heat exchanger faces of the parts
; the width of which slot corresponds to the thickness
of the Nitinol*strip 21. The heat exchangers 22 and 27
extend over the entire length of the Nitinol* strip. The
pipe systems of the heat pump run inside the jaws of the
heat exchangers. The jaws of the heat exchangers are
normally kept in the opened position, e.g., by means of
springs (not shown in the drawing).
When the Nitinol*strip 21 comes from the top
downwards a]ong with the crankshaft 24, the rods 36 at
its ends contact the lower stop members 37. ~his has
the effect that the relay (not shown in the drawing)
connected to the stop member makes the jaws of the heat
exchanger 22 pull themselves against the spring force
towards each other, into tight contact against the
Nitinol*strip 21 at both sides of the strip. Thereby
the strip is rapidly heated to its transi~ion temper-
ature and is shortened intensively. The cranks of the
crankshafts 2~ revolve in opposite directions beyond
their lowermost points until the rod 36 starts rising
apart from the stop member 37. The articulated joint
34 makes it possible that, during this period of time,
the position of the Nitino~ strip has not been changed
in the vertical direction. At the same time as the
rod 36 moves apart from the stop member 37, the relay
releases the jaws of the heat exchanger apart from
each other, and -the strip 21 can rise.
When the rod 36 rises further, it reaches
contact with the upper stop 37, which correspondingly
3~ makes the jaws of the upper heat exchanger 27 close
themselves around the strip 21. Thereby the cooling
faces 26 reach tight contact with the strip 21 and cool
* (Trade mark)
., .
6gL63~
13
it efficiently and rapidly. After that, the strip is
again extended as pulled by the crankshaft 24. There-
inafter the sequence of movements is repeated again.
Like in the embodiment of F~iyures 6 to 8, in
the embodiment of Figures 10 and 11 several parallel
strips 21 are also used. In such a case, there are
heat exchangers 22 and 27 of its own for each strip.
The stop members 37 may be, e.g., fork-shaped,
whereby the rod 36 ends up between the two vertical pins
of the fork and remains reliably in its position.
Alternatively, the stop members 37 and the
articulated joints 34 may also be omitted. In such a
case, in stead of stop members 37, limit switches are
used which activate the relays closing the jaws of the
heat exchangers. In such a case, the heat exchangers
are attached resiliently, e.g., by means of compression
springs fltted at the hinge side, so that the heat ex-
changers move along with the strips 21 in their closed
position.
In stead of hinged jaws of heat exchangers, it
is also possible to use parts that move towards each
other and away from each other so that their heat ex-
changer faces remain constantly parallel to each other.
Either one of the jaws or both of the jaws may be mobile.
The length of the movement may be very short; it is
enough that the strip 21 can be detached from between
the jaws.
In stead of a flat Nitino~ strip, a wire of
circular section may also be used, whereat the jaws of
the heat exchangers have recesses corresponding to the
section of the wire. However, in view of efficient
transfer of heat, a flat band is preferable. In view
of efficient operation of the apparatus, it is also
important that the contact faces of the jaws are as
~` 35 smooth as possible and uniformly heated.
* (Trade mark)
.. ..
