Axial Turbine Blade Tip Cooling via Real-Time Feedback Control
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Solution Overview
Problem
Low-pressure steam turbines face inefficiencies due to sub-optimal control of windage heating in last stage blades, leading to reduced blade life and excessive cooling fluid consumption, as existing methods rely on predictive assessments rather than direct measurement of blade conditions.
Innovation Solution
A monitoring control system with embedded sensors in the last stage blades measures physical properties like temperature, strain, and moisture, and adjusts a control element for water or steam injection and mass flow to optimize cooling, ensuring neither excessive nor inadequate cooling, thereby extending blade life and enhancing turbine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling medium is injected to reduce windage heating, then blade temperature is reduced, but excessive cooling fluid consumption leads to increased erosion and reduced turbine efficiency
Solution Approach 1:
The patent implements a feedback control system where temperature sensors embedded in the last stage blade tips continuously monitor actual blade temperature. The controller compares measured temperature against threshold values and dynamically adjusts cooling medium injection rates accordingly. This closed-loop feedback mechanism replaces predictive assessment with real-time measurement, ensuring cooling fluid is injected only when and to the extent actually needed, thereby minimizing erosion and efficiency loss while maintaining adequate temperature control.
Solution Approach 2:
The system dynamically changes the parameter of cooling medium injection rate based on real-time blade temperature measurements. By adjusting the flow rate of cooling fluid according to actual thermal conditions rather than using fixed predictive values, the system optimizes the balance between temperature control and fluid consumption, reducing unnecessary injection that causes erosion.
2Reliability
If predictive assessment methods are used to control cooling, then blade life is protected, but sub-optimal control results in excessive or inadequate cooling
Solution Approach 1:
The patent employs feedback control through embedded temperature sensors that provide real-time measurement of actual blade tip temperatures. This measured information feeds back to the controller, which adjusts cooling medium injection to match actual thermal conditions. This eliminates the sub-optimal nature of predictive assessment methods, ensuring neither excessive cooling (which reduces efficiency) nor inadequate cooling (which threatens blade life).
Solution Approach 2:
The blade itself provides the information needed for its own cooling control through embedded temperature sensors. The blade autonomously communicates its thermal state to the control system, enabling self-regulated cooling that optimizes both blade life protection and turbine efficiency without relying on external predictive models.
3Temperature
If more cooling medium is injected to ensure adequate cooling, then blade temperature control is improved, but excessive injection causes increased erosion on blade edges
Solution Approach 1:
The feedback control system uses real-time temperature measurements from embedded sensors to determine the precise cooling needs of the blade tips. The controller adjusts cooling medium injection rates to match actual thermal conditions, injecting only the minimum necessary amount to maintain safe temperatures. This prevents excessive injection that would cause harmful erosion on blade leading and trailing edges.
Solution Approach 2:
The system applies partial action by injecting cooling medium only to the extent actually needed rather than using excessive injection. The feedback-controlled injection rate ensures adequate cooling is provided without over-cooling, thereby preventing the erosion that results from excessive cooling fluid impact on blade edges.
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
The system optimizes blade life and turbine efficiency by providing precise control based on real-time measurements, minimizing cooling fluid usage and reducing erosion and overheating risks.
Implementation Method 1
at least one sensor configured and arranged in the distal region of at least one last stage blade, for measuring at least one physical property of the airfoil in the distal region
Implementation Method 2
last stage blades are susceptible to windage heating of the blade tip area
Implementation Method 3
The solution comprises injecting a cooling medium in the vicinity of the last stage tip region
Implementation Method 4
a control element, configured and arranged to influence at least one of the physical properties of the distal region of the last stage blades
Data Source
AI summary
The invention relates to an axial flow turbine and method of operating thereof. The turbine comprises a last stage of rotating blades located towards a downstream end of the turbine having a distal region at an end of the airfoil of the blades. A monitoring control system has at least one sensor in the distal region of at least one last stage blade for measuring at least one physical property of the airfoil and a control element that is capable of influencing at least one physical property of the distal region. The control system further includes a controller that adjusts the control element based on at least measured physical property so by controlling the at least one physical property.