Turbine Casing Sleeve Cooling for Ferritic Alloy Reliability
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Solution Overview
Problem
High-temperature and high-pressure working fluids in power generation systems, such as CO2, pose challenges to turbine casing reliability due to mechanical strength reduction and high manufacturing costs, particularly with Ni-based alloys, which are expensive and prone to defects.
Innovation Solution
A power generation system design incorporating a sleeve within the turbine casing with a cooling fluid passage between the inlet pipe and the sleeve, where the cooling fluid has a lower temperature than the working fluid, to mitigate temperature increases and enhance mechanical strength, allowing for the use of less expensive ferritic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature and high-pressure working fluid is used to improve power generation efficiency, then power generation efficiency is improved, but mechanical strength of turbine casing is lowered
Solution Approach 1:
The turbine casing is divided into an inner casing and an outer casing, with a cooling fluid passage formed between them. This segmentation allows the cooling fluid to flow through the passage and cool the inner casing that is exposed to high-temperature working fluid, thereby maintaining the mechanical strength of the turbine casing while enabling the use of high-temperature working fluid for improved power generation efficiency.
Solution Approach 2:
A cooling fluid is introduced as an intermediary substance to transfer heat away from the turbine casing. The cooling fluid flows through the cooling fluid passage between the inner and outer casings, absorbing heat from the inner casing and preventing excessive temperature rise, thus preserving the mechanical strength of the casing materials.
2Reliability
If Ni-based alloy is used to increase safety and reliability, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The cooling fluid passage is selectively formed in regions where high temperature exposure would otherwise require expensive Ni-based alloys. By providing targeted cooling in these critical areas, the patent enables the use of less expensive ferritic materials or stainless steels in those regions, thereby reducing manufacturing cost while maintaining reliability through active thermal management.
Solution Approach 2:
The patent changes the thermal parameter (temperature) of the turbine casing by introducing a cooling fluid passage. This parameter change allows the casing to operate at lower temperatures than it would without cooling, enabling the use of materials with lower temperature resistance requirements (and thus lower cost) while maintaining the same reliability level.
3Strength
If Ni-based alloy is used to manufacture large-sized structure, then strength is improved, but defects such as shrinkage cavity occur frequently
Solution Approach 1:
The introduction of the cooling fluid passage changes the operating temperature parameter of the turbine casing, allowing the use of ferritic materials or stainless steels instead of Ni-based alloys. These alternative materials have better castability and lower defect rates when manufacturing large-sized structures, thereby reducing shrinkage cavities and other manufacturing defects while maintaining sufficient strength through active cooling.
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 design improves the reliability and reduces manufacturing costs by maintaining the turbine casing within a tolerable temperature range, preventing mechanical strength degradation and enabling efficient cooling without the need for expensive Ni-based alloys.
Implementation Method 1
a cooling fluid whose temperature is lower than the working fluid flows between the inlet part and the sleeve
Data Source
AI summary
A turbine and so on capable of enabling high reliability are provided. In the turbine of an embodiment, a turbine rotor is accommodated in a turbine casing, and is rotated by a working medium which is introduced after flowing in an inlet pipe of a combustor. A sleeve is provided at the turbine casing, and accommodates the inlet pipe therein. Here, the sleeve is thicker than the inlet pipe, and a cooling fluid whose temperature is lower than the working fluid flows between the inlet pipe and the sleeve.