Compressor Extraction Nozzle Asymmetric Gap Design
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Solution Overview
Problem
The flow rate of air becomes uneven near the extraction nozzle in compressors with extraction structures, leading to stall and surge, which decreases the operating efficiency and increases the likelihood of surge when the number of pipes is reduced.
Innovation Solution
A compressor design where the radial gap between the extraction-chamber casing and the rotor casing is larger at the rearward rotation direction side of the extraction nozzle than at the forward rotation direction side, adjusting the flow passage area to match the varying flow rates, and a smooth curved connection between the nozzle surfaces to prevent fluid flaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the number of extraction pipes is reduced for weight reduction, then the weight decreases, but the flow rate unevenness increases and surge margin is reduced
Solution Approach 1:
The gap between the extraction chamber casing and rotor casing is made non-uniform, with a larger gap at the rearward rotation direction side and a smaller gap at the forward rotation direction side. This local variation in gap size compensates for the asymmetric flow distribution caused by rotor rotation, balancing the flow rate at both sides of the extraction nozzle and preventing surge while using fewer pipes.
Solution Approach 2:
The invention intentionally introduces asymmetric gap design to counteract the asymmetric flow distribution. By making the gap larger on one side and smaller on the other, the design creates a symmetric flow rate distribution at the extraction nozzle, thereby improving surge margin while reducing the number of pipes needed.
2Ease of manufacture
If a uniform gap is maintained between extraction-chamber casing and rotor casing, then manufacturing is simpler, but flow rate unevenness occurs near the extraction nozzle
Solution Approach 1:
Instead of maintaining a uniform gap for manufacturing simplicity, the invention applies local quality variation by creating a non-uniform gap pattern. The gap is deliberately made larger at the rearward side and smaller at the forward side to compensate for flow rate differences, thereby improving overall air flow efficiency while accepting increased manufacturing complexity.
3Area of stationary object
If the gap is made larger at the forward rotation direction side, then the flow passage area increases, but the flow rate becomes excessively high causing unevenness and potential stall
Solution Approach 1:
The invention applies local quality control by varying the gap size at different circumferential positions. Rather than uniformly increasing the gap area, the gap is made larger only at the rearward rotation direction side and smaller at the forward side, achieving balanced flow rate distribution and preventing both stall and excessive flow rate unevenness.
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 design reduces flow rate unevenness, prevents stall and surge, and allows for a reduction in the number of extraction nozzles, thereby reducing weight and production costs while maintaining compressor efficiency.
Implementation Method 1
an extraction nozzle connected to the extraction-chamber casing from an outer circumferential side of the extraction-chamber casing and guiding the fluid inside the extraction chamber to an outside of the compressor
Implementation Method 2
a rotor that rotates about an axis thereof and compresses a gas such as air
Implementation Method 3
the air, which is extracted to the interior of the extraction chamber from the main flow passage, flows so as to swirl in a circumferential direction with a rotation of the rotor
Data Source
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AI summary
This compressor is provided with: a rotor (2) that rotates around an axis line; a rotor casing (3) that forms a primary duct in the space with respect to the rotor (2) by encircling the rotor (2) from the outer peripheral side; an air bleed chamber casing (6) that is provided to the outer peripheral side of the rotor casing (3) and forms an air bleed chamber (12) interconnecting with a primary duct (4) in the space with respect to the rotor casing (3); and an air bleed nozzle (14) that is connected to the air bleed chamber casing (6) from the outer peripheral side and that therewithin leads a fluid in the air bleed chamber to the outside. The spacing in the radial direction between the air bleed chamber casing (6) and the rotor casing (3) is larger at the rearward side (R2) in the direction of rotation of the rotor (2) with respect to the air bleed nozzle (14) than at the frontward side (R1) in the direction of rotation of the rotor (2).