Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
  • F03G7/064—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by its use
  • F03G7/0641—Motors; Energy harvesting or waste energy recovery
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
  • F02G5/00—Profiting from waste heat of combustion engines, not otherwise provided for
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
  • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
  • F03G7/0614—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element using shape memory elements
  • F03G7/06143—Wires
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2251/00—Material properties
  • F05C2251/08—Shape memory

Definitions

• the present application relates to the field of energy recovery and in particular to the use of Shape-memory Alloys (SMA) or Negative Thermal Expansion materials (NTE) for same.
• SMA Shape-memory Alloys
• NTE Negative Thermal Expansion materials
• SMA Shape-memory Alloy
• Shape-memory Alloys are the copper-zinc-aluminium- nickel, copper-aluminium-nickel, and nickel-titanium (NiTi) alloys but SMAs can also be created, for example, by alloying zinc, copper, gold and iron.
• an energy recovery device comprising a plurality of Shape-Memory Alloy (SMAs) or Negative Thermal Expansion (NTE) elements arranged as a plurality of wires positioned substantially parallel with each other to define a core wherein the wires are selected to have different dimensions such that the plurality of wires are activated at substantially the same time in response to a temperature change.
• SMAs Shape-Memory Alloy
• NTE Negative Thermal Expansion
• wires positioned towards the centre of the core have a smaller diameter than wires positioned near the outside of the core.
• the wire diameters are selected to match the characteristics of a fluid flow at any point in the core and take account of the impact of the flow with other wires and the loss in energy of the flow as it penetrates the bundle, such that an even activation time can be achieved for the plurality of wires.
• At least one of the wires is tapered at one end.
• a core for use in an energy recovery device comprising a plurality of wires positioned substantially parallel with each other and wherein the wires are selected to have different dimensions such that the plurality of wires are activated at substantially the same time in response to a temperature change.
• activation of at least one wire comprises a transformation from a martensite to an austenite state.
• a method of making an energy recovery device comprising a plurality of Shape-Memory Alloy (SMAs) or Negative Thermal Expansion (NTE) elements arranged as a plurality of wires positioned substantially parallel with each other to define a core comprising the step of selecting a plurality of wires with different dimensions and positioning the plurality of wires so that they are activated at substantially the same time in response to a temperature change.
• SMAs Shape-Memory Alloy
• NTE Negative Thermal Expansion
• Figure 1 illustrates a known energy recovery system
• Figure 2 illustrates a plurality of wires making up a core and uneven wire activation as a result of fluid input dynamics at different temperatures
• Figure 3 illustrates a first embodiment of the invention showing core SMA wires decreasing in diameter size towards the centre of a bundle of wires
• Figure 4 illustrates a second embodiment of the invention illustrating a plurality of tapered core SMA wires decreasing in diameter width from a fluid inlet to an outlet;
• FIG. 5 illustrates a combined tapering and wire diameter reduction in a core described in Figures 3 and 4.
• the invention relates to a heat recovery system under development which can use either Shape Memory Alloys (SMA) or Negative Thermal Expansion materials (NTE) to generate power from low grade heat.
• SMA Shape Memory Alloys
• NTE Negative Thermal Expansion materials
• An exemplary known embodiment of an energy recovery device will now be described with reference to Figure 1 which provides an energy recovery device employing a SMA engine indicated by reference numeral 1 .
• the SMA engine 1 comprises a SMA actuation core.
• the SMA actuation core is comprised of SMA material clamped or otherwise secured at a first point which is fixed. At the opposing end, the SMA material is clamped or otherwise secured to a drive mechanism 2.
• the first point is anchored the second point is free to move albeit pulling the drive mechanism 3.
• An immersion chamber 4 is adapted for housing the SMA engine and is also adapted to be sequentially filled with fluid to allow heating and/or cooling of the SMA engine. Accordingly, as heat is applied to the SMA core it is free to contract.
• the SMA core comprises a plurality of parallel wires, ribbons or sheets of SMA material. It will be appreciated that in the context of the present invention the term 'wire' is used and should be given a broad interpretation to mean any suitable length of SMA or NTE material that can act as a core.
• NiTi Nickel- Titanium alloy
• SMA or NTE material can be used in the context of the present invention.
• a plurality of elongated SMA or NTE wires may be employed together, spaced substanitally parralell to each other, to form a single core.
• a plurality of Shape Memory Alloy (SMAs) or Negative Thermal Expansion (NTE) elements are arranged as a plurality of elongated wires positioned substantially parallel with each other to define a core or core engine. This is equivalent to the SMA engine 1 described with respect to Figure 1 .
• a problem with the core having a plurality of wires is the uneven heating of the wires in the core as shown in Figure 2.
• the invention addresses an unbalance in stress distribution across the SMA bundle that occurs as a result of the fluid dynamics at the entrance to the SMA core, and as the fluid travels up through the core.
• SMA wires of proportionally decreasing diameter towards the centre of a bundle of wires making up the core are used.
• Figure 3 illustrates a first embodiment of the invention showing core SMA wires decreasing in diameter size towards the centre of a bundle of wires 10a, 10b, 10c, 10d, making up the core.
• SMA wires are heated above temperature Austenite start (As)
• Austenite start the wires begin their transformation from martensite to austenite.
• the rate at which the wire heats up is a function of the surface area of the wire to the volume of the wire amongst other factors such as the material characteristics and the transient flow characteristics throughout the bundle.
• the surface area to volume ratio decreases with increasing diameter, resulting in a longer heating time to bring the wire to its austenitic state, and hence activate.
• the energy recovery system will operate well in SMA cores that have multiple fluid inlet points along the length of the bundle, or have a large gap on the outside of the densely packed SMA bundle for fluid to flow - thereby increasing the heat transfer rate at the exterior of the bundle relative to the centre over the entire length of the SMA bundle.
• the SMA wires making up a core are dimensioned with a decreasing taper from a fluid inlet to an outlet.
• Figure 4 illustrates a second embodiment of the invention illustrating a plurality of tapered core SMA wires decreasing in size from a fluid inlet to an outlet. This configuration seeks to balance the effect of a varying rate of heat transfer into the wires as a function of the flow characteristics.
• the flow is more turbulent when the fluid enters the chamber, interacts substantially perpendicularly with the wires and is directed up through the core in comparison with the more laminar flow as the fluid travels up the core.
• the turbulent region will have a larger convection heat transfer coefficient, and thus heating of the wires will occur at a faster rate than it will further up the core in the laminar flow region.
• FIG. 5 illustrates a combined tapering and wire diameter reduction in a core described in Figures 3 and 4. This configuration combines the factors in configuration shown in Figures 3 and 4.
• the exterior SMA wires display a larger diameter to compensate for the inlet flow characteristics, and the tapered angle decreases towards the centre of the wire bundle or core to balance against the reduction in heat transfer as the fluid interacts with the wires within.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Micromachines (AREA)

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• 2015
  • 2015-06-30 GB GBGB1511466.3A patent/GB201511466D0/en not_active Ceased
• 2016
  • 2016-06-30 JP JP2017568064A patent/JP2018520296A/ja not_active Ceased
  • 2016-06-30 WO PCT/EP2016/065310 patent/WO2017001562A1/en not_active Ceased
  • 2016-06-30 EP EP16741543.9A patent/EP3317536B1/en active Active
  • 2016-06-30 US US15/741,049 patent/US10294928B2/en active Active

Patent Citations (5)

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