Centrifugal Compressor Impeller Cooling via Annular Air Passage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The downstream cavity of a centrifugal compressor impeller in turbomachines experiences high temperatures due to ventilation air being taken from the compressor outlet, leading to potential material deterioration, and existing solutions like thermal shields increase mass and reduce performance.
Innovation Solution
A cooling system that uses an annular sheet around the diffuser flange to create an annular passage for air circulation from an upstream stage or heat exchanger, providing cooler air to ventilate and cool the impeller, eliminating the need for a heat shield and reducing the impeller's temperature by 50-60°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ventilation air is taken from the compressor outlet, then the annular cavity is ventilated, but the air temperature becomes too high causing impeller material deterioration
Solution Approach 1:
The invention extracts the ventilation air source from the hot compressor outlet and relocates it to a cooler source upstream of the impeller. This is achieved by introducing a separate cooling air intake that draws air from a lower-temperature region, thereby removing the harmful thermal effect while preserving the ventilation function.
Solution Approach 2:
The patent introduces an intermediary cooling air flow that acts as a mediator between the impeller and the hot compressor outlet air. This intermediate cooler air stream mixes with or replaces the hot ventilation air, reducing the temperature acting on the impeller while maintaining cavity ventilation.
2Reliability
If an annular thermal protection shield is mounted on the impeller, then the impeller is protected from high temperatures, but the mass and rotational inertia increase reducing turbomachine performance
Solution Approach 1:
The invention replaces the mechanical thermal protection shield with a thermal management system using cool air flow. Instead of adding a physical barrier structure, the solution uses a fluid-based cooling mechanism where cooler air is directed through passages to absorb heat from the impeller, achieving protection without additional mass.
Solution Approach 2:
The patent employs pneumatic cooling by introducing a controlled flow of cool air through specially designed passages within or around the impeller. This pneumatic system uses pressure-driven air flow to remove heat, replacing the need for a solid thermal shield and maintaining the impeller's original mass and rotational characteristics.
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
Effectively cools the impeller without additional mass, improving turbomachine performance by reducing the temperature of the impeller and allowing increased airflow to the diffuser and combustion chamber.
Implementation Method 1
air at a temperature lower than that of the air leaving the compressor stage centrifugal circulates in the annular passage from upstream to downstream to provide cooling and ventilation of the annular flange of the diffuser
Implementation Method 2
Evacuate the thermal energy provided by the impeller
Implementation Method 3
a compressor stage comprising an impeller... centrifugal compressor
Implementation Method 4
its temperature is further increased by viscous friction on the downstream face of the impeller
Data Source
AI summary
The system has an annular plate (70) mounted coaxially around an annular flange (26) of a diffuser (12), where the plate is made of a material with low thermal conductivity. The plate and the flange delimit an annular passage (72) so that air with a temperature lower than that of the air exiting a centrifugal compressor (10) circulates in the passage from upstream to downstream, where the passage is connected in upstream to an air-bleeding unit on an upstream stage of an axial compressor or in an outlet of a cooling heat exchanger.