Radial Turbine Cooling via Bleed Flow Integration
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Solution Overview
Problem
High-temperature radial gas turbines face challenges in extending operational lifetime and maintaining efficiency due to the complexity and cost of hollow blade cooling methods, which require pressurized cooling air and reduce energy efficiency.
Innovation Solution
A method involving a bleed flow of fluid from the compressor outlet directed to the rotor blade roots, cooling the blades and mixing with main air to maintain high temperatures and efficiency, with a bleed fraction of at least 3% improving thermal efficiency and operational lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If hollow blade cooling passages are used to cool rotor blades, then rotor blade temperature is reduced and lifetime is extended, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The cooling function is segmented from the blade structure itself and relocated to an external cooling system with separate components (cooling channels in stator, cooling air supply system), allowing the blade to remain simple while still achieving cooling
Solution Approach 2:
The cooling passages are extracted from the rotor blade hollow structure and implemented externally through stator cooling channels and bleed air systems, eliminating the need for complex internal blade cooling geometry
2Temperature
If hollow blade cooling passages are used, then rotor blade temperature is reduced, but manufacturing cost increases due to thick blade requirements and complex fluid flow design
Solution Approach 1:
The cooling function is extracted from the blade manufacturing process and implemented through separate cooling system components that can be manufactured independently using standard techniques
Solution Approach 2:
The stator structure serves multiple functions: it provides structural support and simultaneously houses the cooling channels, eliminating the need for separate cooling components and simplifying manufacturing
3Temperature
If pressurized cooling air is used in hollow blades, then cooling effectiveness is improved, but energy efficiency of the turbine decreases
Solution Approach 1:
The bleed air that would be wasted is converted into a useful cooling resource, and the heated cooling air is recovered and mixed back into the main flow, turning what would be energy loss into an efficient cooling process
Solution Approach 2:
Instead of discarding the bleed air after cooling, the system recovers the heated air and mixes it back into the main turbine flow, recovering its remaining energy value and eliminating waste
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 method increases rotor blade lifetime and thermal efficiency of the turbine, while improving the effectiveness of recuperator heat exchangers, without energy loss, as the bleed air is heated and reintegrated into the main airflow.
Implementation Method 1
This cools the blade roots by an amount which increases in proportion to the mass flow rate of the bleed flow
Implementation Method 2
the bled air is heated and then mixed with the main air flowing into the turbine
Implementation Method 3
the bled air taken from the compressor outlet improves the thermal effectiveness of a recuperator heat exchanger
Data Source
AI summary
A method for cooling a high-temperature radial gas turbine engine increases turbine thermal efficiency and/or extends turbine operational lifetime. A bleed flow path enables cooling air to flow from a compressor outlet and along surfaces of the gas turbine rotors. The amount of cooling increases in proportion to a bleed fraction, which is defined as the ratio of mass flow in the bleed flow path to total mass flow in the compressor outlet. The heated air in the bleed flow path is mixed with the main mass flow into the turbine engine, so as to restore mass flow into the turbine, while maintaining a high turbine operating temperature and thermal efficiency. The thermal efficiency of a recuperator also increases in proportion to the bleed fraction.