Variable-Pitch Compressor Vanes With Dynamic Air Bleed
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Solution Overview
Problem
Existing turbomachine compressors with fixed air intake geometry suffer from reduced efficiency and surge margin due to air separations at low speeds and increased fuel consumption, as the fixed geometry is not adaptable to varying operating conditions.
Innovation Solution
The compressor features variable-pitch vanes with air intake orifices that communicate with casing holes only when the blades are in closed or intermediate positions, allowing air bleed to reduce separations at low speeds without affecting high-speed performance by closing off at full speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed geometry air taps are used to limit separations at low speed, then separation reduction is achieved, but compressor efficiency and surge margin are degraded at high speed
Solution Approach 1:
The patent applies the dynamics principle by making the air tap geometry variable rather than fixed. The air tap cross-sectional area changes dynamically with the blade pitch angle, allowing the system to adapt to different operating conditions. At low speeds with closed blades, the air tap area is larger to reduce separations, while at high speeds with open blades, the air tap area decreases to maintain compressor efficiency and surge margin.
2Reliability
If fixed air bleed geometry is used, then separation reduction is achieved at given operating speed, but surge margin optimization capabilities are limited
Solution Approach 1:
The patent implements dynamics by coupling the air tap geometry to the variable-pitch mechanism. As the blades rotate to different pitch angles, the air tap cross-sectional area automatically adjusts, enabling the system to optimize surge margin across the entire operating range rather than being constrained to a single operating point.
Solution Approach 2:
The patent applies parameter changes by varying the air tap cross-sectional area as a function of blade pitch angle. This dynamic parameter adjustment allows the air bleed system to adapt to changing flow conditions, maintaining optimal separation control and surge margin across different compressor operating regimes.
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 dynamically modulates air flow to minimize air separations and improve compressor performance at low speeds while maintaining efficiency at high speeds, optimizing fuel consumption and surge margin.
Implementation Method 1
the plates of at least some of the blades each comprise an orifice for taking air from the stream of the compressor, these orifices being intended to communicate with air passage holes formed in the casing when the blades are in the first position
Implementation Method 2
the angle of incidence between the direction of air flow in the compressor channel and the airfoil can reach high values which give rise to friction separations
Data Source
Figure 1
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AI summary
Turbomachine compressor comprising variable-pitch vanes comprising an aerofoil section connected by a mounting plate (17) of circular outline to a pivot (18) guided in rotation in an orifice in a casing (14), the mounting plate of the vane comprising at least one notch (60) for bleeding air from the compressor stream, this notch being intended to communicate with a hole (62) in the casing in order to remove the air bled off when the vanes are in a first position, and to be closed off by this casing when the vanes are in a second position, so that the flow rate of bled air depends on the pitch angle of the vanes.