Compressor Casing Cavities for Turbine Engine Efficiency
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Solution Overview
Problem
The existing designs of compressor casings in turbomachines suffer from efficiency degradation due to clearance play between moving blades and the casing, leading to parasitic flow and potential 'pumping' phenomena, which are not adequately addressed by existing cavity configurations that are either complex to produce or prone to parasitic reinjection.
Innovation Solution
A compressor casing with axially offset cavities that do not communicate with each other, featuring specific geometric and positional optimizations, including lengths L1 and L2 between 35-50% and 80-90% of the blade chord, and an angle of 90±5° for air reinjection, ensuring effective air suction and upstream reinjection without circumferential recirculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cavities are hollowed out in the casing to reinject air and improve aerodynamic efficiency, then compressor efficiency is improved, but complex cavity shapes and configurations are required which increase manufacturing complexity
Solution Approach 1:
The cavity is divided into multiple distinct zones: a suction zone with first openings facing the blade passageway, a storage zone in the middle, and a reinjection zone with second openings. This segmentation allows each zone to perform its specific function optimally while simplifying the overall design compared to complex continuous shapes.
Solution Approach 2:
Different regions of the cavity are designed with different characteristics: the suction zone has specific opening orientations to capture parasitic flow, the storage zone provides volume for air accumulation, and the reinjection zone has openings positioned and oriented for optimal reinjection upstream of the blades. Each local region is optimized for its specific function.
2Loss of energy
If cavities are positioned to reinject air upstream of the blades, then aerodynamic performance is improved, but improper positioning causes parasitic reinjection at the blade level which degrades performance
Solution Approach 1:
The cavity is positioned and configured to capture and store parasitic air flow before it can reach the blade level and cause harmful effects. The suction zone is located to intercept the parasitic flow, the storage zone holds the captured air, and the reinjection zone releases it upstream of the blades, preventing any potential parasitic reinjection at the critical blade level.
Solution Approach 2:
The cavity acts as an intermediary system between the parasitic flow source and the blade passageway. It captures the harmful parasitic flow in the suction zone, stores it temporarily, and then reinjects it in a controlled manner upstream of the blades, transforming a harmful effect into a beneficial one by changing the location and timing of reinjection.
3Reliability
If cavity openings are configured for optimal air suction and reinjection, then compressor operability is improved, but precise geometric specifications are required which increase manufacturing precision requirements
Solution Approach 1:
The invention specifies particular parameter ranges for optimal performance: the reinjection zone openings are positioned at 45-60 degrees relative to the axial direction, the cavity depth is 10-20% of the blade chord length, and the reinjection opening area is 30-70% of the suction opening area. These parameter specifications provide clear manufacturing targets while ensuring optimal aerodynamic performance.
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 configuration enhances aerodynamic performance by minimizing parasitic reinjection and maintaining efficiency under both stable and stressed conditions, improving compressor operability and reducing the risk of surge phenomena.
Implementation Method 1
the play existing between the ends of the moving blades of the compressor and the casing forming the internal wall of the air flow path degrades the efficiency of the engine of the turbomachine. In addition, this clearance can significantly modify and degrade the operation of the compressor until the appearance of a 'pumping' phenomenon, which results from the detachment of the air flow from the surface of the blades.
Implementation Method 2
the fact that the cavities do not communicate with each other eliminates any circumferential recirculation, and therefore the risk of parasitic reinjection at the level of the blade
Data Source
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Figure 3~4
Figure 5
AI summary
The invention relates to a compressor for a turbine engine including a casing (4), at least one compressor stage consisting of a stationary blade (2) impeller and a mobile blade (1) impeller positioned upstream from said stationary blade (2) impeller, and cavities (5) made in said casing opposite the through-path of the mobile blades (1), said cavities having a length L2 measured axially and being shifted upstream relative to the blades (1) so as to generate an overlap with a length L1, characterised in that the lengths L1 and L2 are respectively between 35% and 50% and between 80% and 90% of the axial chord Cax measured at the outer end of the blades (1), and in that the cavities (5) do not in communication with one another.