Centrifugal Compressor Diffuser Platform Vanes
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Solution Overview
Problem
Centrifugal compressor diffusers experience unacceptable levels of material stress at vane-to-casing joints due to the high stress concentrations at the vane tip, making it difficult to reliably add stress-reducing features like fillets after assembly.
Innovation Solution
The design moves the vane-to-casing joint away from the vane tip by incorporating a platform head with a larger lateral dimension than the vane body, allowing for a joint offset and the inclusion of a fillet between the platform head and vane body before assembly, which reduces stress and facilitates a stronger, more reliable joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the vane-to-casing joint is positioned at the vane tip to simplify assembly, then the assembly process is easier, but high stress concentrations occur at the joint leading to unacceptable material stress levels
Solution Approach 1:
The platform head extends the vane structure in a new dimension (laterally perpendicular to the vane body length), moving the joint location away from the high-stress vane tip region to a lower-stress area on the platform head, thereby reducing stress concentrations while maintaining assembly simplicity
Solution Approach 2:
A fillet is预先 added to the vane body at the joint location before assembly, preparing the geometry in advance to reduce stress concentrations. This preliminary geometric modification ensures stress reduction is built into the design before the components are assembled together
2Stress or pressure
If a fillet is added to reduce stress at the joint, then material stress is reduced, but it becomes difficult to reliably add the fillet after assembly
Solution Approach 1:
The fillet is added to the vane body geometry before assembly with the casing, rather than attempting to add it after assembly. This preliminary geometric modification is built into the manufacturing process of the vane itself, making stress reduction reliable and manufacturable
Solution Approach 2:
The vane is segmented into distinct functional portions: the vane body that receives the fillet for stress reduction, and the platform head that provides the joint surface. This segmentation allows the fillet to be applied to the vane body independently before assembly, avoiding the difficulty of adding it after the joint is formed
3Reliability
If the joint is moved away from the vane tip using a platform head, then stress is reduced and reliability is enhanced, but the device complexity increases
Solution Approach 1:
The platform head is merged with the vane body to form a single integrated vane component. This combines the stress-reducing platform head geometry with the functional vane body into one piece, achieving joint reliability improvement without the complexity of separate components or additional assembly steps
Data Source
AI summary
According to some aspects of the present disclosure, a diffuser for a centrifugal compressor is provided. The diffuser may comprise an outerband casing and an innerband casing. The outerband casing may comprise an annular flowpath boundary member that has a flowpath boundary surface. The flowpath boundary member may define a plurality of vane-receiving pockets spaced about a circumference of the member. The innerband casing may comprise an annular flowpath boundary member that has a flowpath boundary surface. The flowpath boundary member may comprise a plurality of vanes spaced about a circumference of the member. Each of said plurality of vanes may comprise a vane body that extends from the flowpath boundary surface, a platform head that has a lateral dimension normal to the length of the vane body greater than the lateral dimension of the vane body, and a fillet between the platform head and the vane body. The innerband casing may be positioned so that the platform head of each of the plurality of vanes is received in a respective vane-receiving pocket defined by the flowpath boundary member of the outerband casing. When received, the fillet of each of the plurality of vanes may be adjacent the flowpath boundary surface of the flowpath boundary member of said outerband casing. The flowpath boundary surfaces of each of said casings and said vanes define a fluid flowpath in said diffuser.