Centrifugal Impeller Heating Passage for Thermal Stress Reduction
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Solution Overview
Problem
High compressor delivery temperatures in gas turbine engines induce significant thermal gradients and thermal stresses in centrifugal impellers, reducing their low-cycle fatigue life.
Innovation Solution
An impeller assembly with a heating passage that directs bleed air from the back face of the impeller forwardly through its bore to reduce temperature gradients, using a bleed apparatus to deliver compressed air and mitigate thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high compressor delivery temperature is used to improve fuel economy, then fuel efficiency is improved, but thermal gradients and thermal stresses in the impeller increase, reducing low-cycle fatigue life
Solution Approach 1:
The patent applies local quality by directing heated bleed air specifically to the radially inner portion of the impeller through a heating passage in the bore, creating a localized temperature increase in the critical high-stress region. This targeted thermal treatment reduces the thermal gradient between inner and outer portions without requiring a uniform temperature change throughout the entire impeller, thereby maintaining fuel economy benefits while protecting the specific vulnerable area from thermal stress damage
2Use of energy by moving object
If high compressor delivery temperature is used to improve fuel economy, then fuel efficiency is improved, but thermal gradients between inner and outer portions of the impeller increase, causing greater thermal stresses
Solution Approach 1:
The patent changes the temperature parameter locally by introducing heated bleed air into the radially inner portion of the impeller. This creates a controlled temperature modification in the specific region where thermal gradients are most problematic, reducing the overall temperature differential between the inner and outer portions of the impeller while maintaining the high compressor delivery temperature needed for fuel economy
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 solution effectively reduces thermal stresses and extends the low-cycle fatigue life of centrifugal impellers by minimizing temperature gradients between the inner and outer portions, thereby improving the durability and fuel efficiency of gas turbine engines.
Implementation Method 1
a heating passage extending through at least a portion of the impeller rotor bore, the heating passage having an inlet in fluid communication with bleed air provided to the impeller back face
Data Source
AI summary
An internal heating arrangement for a centrifugal impeller for a gas turbine engine is provided having at least one heating passage extending through into the rotor for directing air bled from the rotor exit along the backface and forwardly through the impeller.