SMA Wire Hydraulic Accumulator for Deepwater Efficiency
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Solution Overview
Problem
Deepwater hydraulic accumulators experience efficiency loss due to increasing hydrostatic pressure, requiring higher pre-charge pressures and leading to increased size, weight, and complexity, as well as potential failure points, especially at depths beyond 5,000 feet.
Innovation Solution
The use of shape memory alloy (SMA) wires acting in tension on a piston to provide power, balanced by hydrostatic pressure through a sea chest, eliminating the need to overcome hydrostatic pressure loads and allowing adjustable power output without pumps or valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pre-charge pressure is increased to overcome hydrostatic pressure at greater depths, then the accumulator can maintain power output, but the size, weight, and complexity of the equipment increase
Solution Approach 1:
The patent replaces the conventional mechanical spring-based pre-charge system with a shape memory alloy (SMA) wire system. The SMA wires undergo phase transformation (austenite-martensite) when heated, generating mechanical force to drive the piston and displace hydraulic fluid. This substitution eliminates the need for high pre-charge pressures and associated heavy-duty pressure vessels, thereby reducing equipment size, weight, and complexity while maintaining power output capability.
Solution Approach 2:
The invention utilizes the phase transition properties of shape memory alloy wires. When electrical current heats the SMA wires, they transform from the martensite phase to the austenite phase, causing significant dimensional change and generating mechanical force. This phase transition mechanism provides a compact, controllable force generation system that replaces conventional high-pressure mechanical systems, resolving the contradiction between power output and device complexity.
2Productivity
If pre-charge pressure is increased to maintain efficiency at greater depths, then power output is maintained, but the size and weight of the accumulator increase
Solution Approach 1:
The patent substitutes the heavy mechanical spring system required for high pre-charge pressures with a lightweight shape memory alloy wire system. The SMA wires generate the necessary force through phase transformation, eliminating the need for massive pressure vessels and heavy pre-charge mechanisms. This maintains operational efficiency at depth while significantly reducing the stationary weight of the accumulator system.
Solution Approach 2:
The invention changes the fundamental operating parameter from high static pre-charge pressure to dynamic thermal actuation. Instead of maintaining constant high pressure through heavy mechanical means, the system uses controlled thermal input to activate SMA wires that generate force on demand. This parameter change enables efficiency maintenance at depth without the weight penalty of high-pressure containment systems.
3Power
If more components are added to maintain power at greater depths, then power output is maintained, but the number of failure points increases
Solution Approach 1:
The patent extracts and eliminates unnecessary components from the conventional accumulator system. By removing the pre-charge gas system, high-pressure valves, and complex pressure regulation mechanisms, the design reduces the number of potential failure points. The simplified SMA wire actuation system requires fewer moving parts and sealing interfaces, thereby improving reliability while maintaining power output capability.
Solution Approach 2:
The shape memory alloy wires provide self-contained force generation through their inherent phase transformation properties. The system does not require external pre-charge systems, pressure regulators, or complex control valves to maintain power output. The SMA wires directly convert thermal energy to mechanical work, creating a self-sufficient actuation system with fewer components and consequently fewer failure points.
4Power
If conventional accumulators are used to overcome hydrostatic pressure, then power can be delivered, but the equipment requires pumps and valves for pressure regulation
Solution Approach 1:
The patent substitutes conventional hydraulic pressure regulation components (pumps and valves) with a direct-acting shape memory alloy wire system. The SMA wires, when heated, directly drive the piston to displace hydraulic fluid at the required flow rates and pressures. This eliminates the need for separate pressure regulation subsystems, reducing device complexity while maintaining the ability to deliver power to sub-sea equipment.
Solution Approach 2:
The invention transitions from static high-pressure systems requiring dynamic regulation to a dynamically actuated system. The SMA wires can be electrically controlled to provide variable force output, enabling direct dynamic control of hydraulic fluid displacement without mechanical pumps or valves. This dynamic actuation approach maintains power delivery capability while eliminating complex pressure regulation components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution maintains efficiency across varying water depths, reduces the number of failure points, and increases the flexibility of sub-sea equipment by eliminating the need for constant pressure output, thus reducing the size, weight, and complexity of the equipment.
Implementation Method 1
Below its transition temperature, the SMA material may be deformed into a different shape and may remain in that deformed shape
Implementation Method 2
When the SMA material is heated above its transition temperature, the SMA material may return to its original shape with a force sufficient to overcome an applied load
Data Source
AI summary
A system, in certain embodiments, includes an accumulator. The accumulator includes a first cylinder configured to receive a fluid within an internal volume of the first cylinder. The accumulator also includes a piston configured to move axially within the first cylinder. Axial movement of the piston within the first cylinder adjusts the internal volume of the first cylinder. The accumulator further includes a plurality of shape memory alloy wires configured to cause the axial movement of the piston within the first cylinder.