Turbine Bucket Cooling Control via Shape Memory Alloy

The patent applies a variable geometry nozzle that can dynamically adjust its opening area in response to changing operating conditions. The nozzle geometry is modified based on whether the turbine is operating at full load or part load, allowing the cooling air flow to be optimized for each operating regime. This dynamic adjustment prevents excessive cooling air bleed during part load operations while maintaining adequate cooling when needed.

The patent changes the geometric parameters of the cooling air nozzle to match different operating conditions. By varying the nozzle opening area as a function of operating parameters (such as power output or temperature differential), the system adapts the cooling air flow rate to match actual cooling demands. This parameter change allows the system to transition from excessive cooling at full load to appropriate cooling at part load.

The system uses the temperature differential between the compressed cooling air and the turbine inlet air to automatically drive the cooling air flow through the variable geometry nozzle. The thermal energy of the hot compressed air itself provides the driving force for the cooling air flow, eliminating the need for additional mechanical work or external power sources. This self-service mechanism reduces the parasitic loss associated with mechanical drive systems.

The patent replaces traditional mechanical flow control mechanisms (such as adjustable valves or variable pitch nozzles requiring mechanical actuation) with a thermally-driven flow control system. The variable geometry nozzle is actuated by thermal expansion or contraction of a responsive material, or by pressure differential driven by the temperature difference between cooling air and inlet air. This substitution eliminates mechanical complexity and reduces energy losses associated with mechanical drive systems.

The patent transitions from a static, fixed-geometry nozzle to a dynamic nozzle that can change its configuration during operation. The variable geometry nozzle incorporates movable components or shape-memory materials that allow it to adapt its opening area in response to operating conditions. This dynamic capability enables the same nozzle structure to serve both full load and part load operations effectively, eliminating the need for multiple fixed nozzles or complex manual adjustment mechanisms.

The nozzle geometry parameters are made variable rather than fixed. The opening area, angle, or shape of the nozzle can change as a function of operating parameters such as power output, temperature differential, or pressure ratio. This parameter change capability allows the nozzle to be optimized for different operating regimes without requiring separate nozzles for each condition, maintaining manufacturing simplicity while achieving adaptability.