Biased Passages for Turbomachinery Diffuser Flow Uniformity
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Solution Overview
Problem
Turbomachinery diffusers face inefficiencies due to assumptions of axisymmetric flow at the diffuser inlet, leading to non-uniform pressure distributions and increased likelihood of early stall and losses, as existing designs fail to account for low-frequency circumferential pressure variations and asymmetric flow fields.
Innovation Solution
The implementation of biased passages in turbomachines, featuring vanes with varying characteristics such as height, chord length, and stagger angle, to bias the circumferential pressure distribution toward uniformity and improve flow field controllability, incorporating flowwise recesses and channels in hub and shroud surfaces to manage asymmetric flow fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If axisymmetric flow assumption is used for diffuser design, then design simplicity is maintained, but flow uniformity deteriorates leading to non-uniform pressure distribution
Solution Approach 1:
The patent applies asymmetry by introducing a biased passage with different geometry characteristics (different angle of divergence, cross-sectional area, or shape) compared to other passages. This asymmetric design compensates for the non-uniform pressure distribution caused by asymmetric impeller exit flow, thereby improving flow uniformity at the diffuser inlet while maintaining reasonable design complexity
Solution Approach 2:
The biased passage is strategically located at specific circumferential positions where pressure uniformity needs improvement. By modifying only the local geometry of specific passages rather than redesigning the entire diffuser, the patent achieves improved flow uniformity with minimal increase in overall design complexity
2Ease of manufacture
If conventional diffuser passages are used, then manufacturing is simplified, but stall resistance deteriorates due to non-uniform pressure distribution
Solution Approach 1:
The biased passage introduces geometric asymmetry to counteract the asymmetric pressure distribution that leads to stall. This allows the diffuser to maintain better flow attachment and delay stall onset, improving reliability while the biased passage itself can be manufactured using standard techniques with minimal complexity increase
3Device complexity
If uniform diffuser passages are used, then design consistency is maintained, but flow field controllability deteriorates under asymmetric operating conditions
Solution Approach 1:
The patent introduces local variation through the biased passage while maintaining uniform design for all other passages. This selective modification enhances flow field controllability under asymmetric conditions without significantly complicating the overall design, as the biased passage serves as a targeted correction rather than a complete redesign
Data Source
AI summary
Turbomachines having one or more flow guiding features designed to increase the performance of the turbomachine. In some examples, flow guiding features are designed and configured to bias a circumferential pressure distribution at a diffuser inlet toward circumferential uniformity, otherwise account for such low-frequency spatial pressure variations, increase the controllability of spatial flow field variations, or modifying flow field variations, etc. In some examples, a diffuser having a row of vanes that include a plurality of first vanes and at least one second vane having a different characteristic than the first vanes are disclosed. In some examples, diffusers having an aperiodic section including one or more biased passages for biasing a flow field are disclosed. And in some examples, turbomachines having flowwise elongate recesses in one or both of a hub and shroud surface are disclosed.