Centrifugal Compressor Impeller Ventilation via Radial Air Deflection
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Solution Overview
Problem
The existing ventilation systems in turbomachines, such as turbojet engines and turboprops, face challenges in efficiently cooling the downstream cavity of centrifugal compressor impellers due to hot air circulation, which can lead to material creep and performance degradation, and traditional thermal protection solutions increase mass and rotational inertia.
Innovation Solution
A ventilation system that uses deflection means to direct ventilation air radially from the inside out along the downstream face of the impeller, circulating cooler air through the mechanically stressed radially internal part and hotter air through the less stressed outer part, eliminating the need for a thermal protection shield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular thermal protection shield is mounted on the downstream face of the impeller, then the impeller is protected from hot air, but the mass and rotational inertia of the impeller increase, reducing turbomachine performance
Solution Approach 1:
The harmful hot air flow is extracted and redirected away from the impeller surface. The deflection means extract the ventilation air from the downstream cavity and redirect it to flow in a direction that prevents contact with the impeller, eliminating the need for a physical shield while maintaining protection.
Solution Approach 2:
The deflection means act as an intermediary element between the hot ventilation air and the impeller. Instead of directly protecting the impeller with a shield, the deflection means mediate by redirecting the air flow path, allowing cool air to replace hot air in the downstream cavity without adding mass to the rotating assembly.
2Quantity of substance
If ventilation air flows from outside to inside in the downstream cavity, then the cavity is ventilated, but the air heats up by viscous friction on the impeller surface, raising impeller temperature and risking material creep
Solution Approach 1:
The flow direction is inverted compared to conventional designs. Instead of air flowing from outside to inside (radially inward), the deflection means redirect the air to flow from inside to outside (radially outward) along the impeller surface. This reversal prevents the air from heating up on the high-stress internal regions and eliminates the temperature gradient that causes thermal stress.
3Reliability
If a thermal protection shield is fixed on the impeller, then hot air is blocked from the impeller, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The deflection means are merged with the existing diffuser structure. The deflection means are fixed to the diffuser housing rather than being separate components mounted on the impeller, integrating the protective function into the existing geometry and reducing the number of parts and assembly steps.
Solution Approach 2:
The ventilation system serves its own protective function through the deflection means. The system uses the existing ventilation air flow to protect the impeller, turning the ventilation function into a dual-purpose system that both cools the cavity and protects the impeller from hot air, eliminating the need for dedicated protective 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 effectively increases the service life of the impeller by distributing heat more evenly and reducing mechanical stress, while also simplifying the design and maintaining turbomachine performance.
Implementation Method 1
This ventilation air is relatively cool at the level of the radially internal part of the impeller and heats up by flowing from the inside to the outside along the downstream face of the impeller
Implementation Method 2
deflection means fixedly mounted in the downstream cavity of the impeller to deflect ventilation air from the part downstream of the downstream cavity and cause it to circulate radially from the inside outwards along the downstream face of the impeller
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The system has a flux deflection unit fixedly mounted in a lower cavity (38) for circulating ventilation air along a lower face (34) of a wheel (36) of a centrifugal compressor stage (10) in a centrifugal manner with respect to an axis of the wheel. The unit has annular sheets (70, 84) fixedly mounted in the cavity of the wheel for guiding the ventilation air, obtained from an outlet of a centrifugal compressor, radially from an interior towards an exterior along the lower face of the wheel. The sheet (70) has an L shaped or a U shaped cross-section and extends along the lower face.