Centrifugal Compressor Return Channel Movable Blades
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Solution Overview
Problem
Conventional built-in centrifugal compressor units with variable-pitch impellers require significant torque and costly movable blades to adjust blade orientation, increasing costs, especially for multi-stage compressors, due to high deflection stresses and the need for robust drive systems.
Innovation Solution
A compressor unit design featuring a return channel with fixed and movable blade portions, where the movable blades are extensions of fixed blades, allowing for adjustable geometry without the need for large, costly movable elements, with the movable blades being smaller and cheaper to produce, and controlled by a single motor, reducing material costs and stress on the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable-pitch impellers are used to modify compression work as a function of gas flow rate, then the operating range is widened, but the cost increases significantly due to large movable blades and robust drive systems required to withstand high deflection stresses
Solution Approach 1:
The blade is divided into two distinct parts: a fixed blade portion and a movable blade portion. The movable blade portion is only an extension of the fixed blade and does not require the same structural robustness. This segmentation allows the movable part to be smaller and cheaper while still achieving the variable pitch function needed to widen the operating range.
Solution Approach 2:
The invention extracts only the essential functional portion of the blade (the extension part) and makes it movable, while leaving the main blade structure fixed. This allows the movable portion to be minimized in size and complexity, reducing manufacturing cost while maintaining the ability to adjust the compression work across different gas flow rates.
2Ease of operation
If each blade is fitted with direct drive means, then precise blade orientation control is achieved, but the device complexity and cost increase significantly
Solution Approach 1:
Multiple movable blade portions are merged with a single common drive mechanism. Instead of having separate drive means for each blade, all movable blade portions are actuated by one drive mechanism, significantly reducing device complexity while maintaining precise control over the blade orientation and the resulting gas flow characteristics.
3Power
If the compressor has several stages, then the compression capability is increased, but the cost of the movable-blade system increases even greater
Solution Approach 1:
In multi-stage compressors, the segmentation principle is applied to each stage's return channel. Only the blade extensions (movable portions) are made adjustable in each stage, while the main blade structures remain fixed. This allows the compression capability to be increased across multiple stages while keeping the movable-blade system cost manageable by minimizing the movable portions in each stage.
4Strength
If larger movable blades are used to withstand deflection stresses, then the structural integrity is maintained, but the material costs and manufacturing complexity increase
Solution Approach 1:
The blade is segmented into a fixed portion that bears the main structural load and a movable extension portion that is optimized for aerodynamic function. The fixed blade portion is designed to withstand deflection stresses and maintain structural integrity, while the movable extension can be smaller and less costly since it does not need to bear the same structural loads independently.
Solution Approach 2:
Instead of making the entire blade movable and thus requiring it to be oversized for structural integrity, the invention inverts the approach: the main blade structure is fixed and provides the structural strength, while only the extension portion is movable. This allows the movable portion to be smaller and cheaper while the fixed portion ensures structural integrity.
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 design achieves a wider operating range for centrifugal compressor units at a lower cost by using smaller, more affordable movable blades that can adjust to maintain efficient gas flow and pressure ratios, while eliminating sealing issues between motor and compressor housings by immersing both in the same gas volume.
Implementation Method 1
a movable blade portion extending from each fixed blade in the return channel, each movable blade portion being movable in rotation about an axis substantially parallel to the geometric axis of the impeller, each movable blade portion being deflectable by rotation about its axis of rotation, so as to be able to adjust a tangential speed component of the gases coming from the return channel
Implementation Method 2
a centrifugal compressor with one or more compression stages, Each compression stage includes an impeller mounted on a driven shaft
Implementation Method 3
a diffuser portion downstream of the impeller and upstream of the return channel
Data Source
Figure 1~2
Figure 3a~4
AI summary
A compressor unit (25) is disclosed comprising at least a first motor driving in rotation at least one impeller (4) of a compression stage, having at the outlet of the impeller (4) a diffuser (23) designed to centrifugally channel the gases coming from the impeller (4), and having a centripetal return channel (24) downstream of the diffuser (23).The return channel (24) includes at least one movable blade portion (21) that, when moved, can vary a tangential component of the speed of the gases coming from the return channel (24).