Inducer Partial Shroud and Short Blades for Cavitation Control
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Solution Overview
Problem
Current inducers in liquid rocket engines face challenges in achieving high suction capability while minimizing cavitation and vibrations, particularly at low blade angles, which leads to fluid flow blockage and radial load imbalances, especially in configurations with fewer blades.
Innovation Solution
The design incorporates a partial shroud enclosing only a portion of the full-size blades' outer edges and includes short, symmetrically offset partial blades to stabilize cavitation patterns, reducing blockage and radial loads, and allowing for a wider operating range by maintaining a low number of full-size blades and minimizing shroud length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of blades is reduced to minimize blockage and improve suction capability, then fluid flow capacity is improved, but cavitation stability deteriorates
Solution Approach 1:
The blade assembly is segmented into full-size blades and partial blades, where full-size blades provide the necessary fluid flow capacity while partial blades (attached to the shroud) provide cavitation stability. This segmentation allows the system to achieve both high productivity and stable cavitation patterns simultaneously.
Solution Approach 2:
Different portions of the blade assembly have different functions: the full-size blades are optimized for fluid flow capacity with larger chord lengths, while the partial blades are optimized for cavitation control with smaller chord lengths. This local differentiation of blade properties resolves the contradiction between flow capacity and cavitation stability.
2Productivity
If blade angles are reduced to achieve ultra high suction capability, then suction performance is improved, but fluid flow blockage increases
Solution Approach 1:
Instead of using full-size blades throughout, the design uses partial blades (with reduced chord lengths) attached to the shroud to provide just enough flow guidance without excessive blockage. This partial action approach maintains suction capability while minimizing fluid flow blockage.
3Object-affected harmful factors
If a full shroud is used to eliminate vortex cavitation, then cavitation damage is reduced, but weight and manufacturing complexity increase
Solution Approach 1:
The design extracts only the necessary portion of the shroud (the partial shroud) rather than using a full shroud. The partial shroud provides sufficient cavitation control while eliminating the excessive weight and manufacturing complexity of a complete shroud structure.
Solution Approach 2:
Instead of applying a full shroud, the design applies a partial shroud that provides just enough cavitation protection. This partial action approach reduces the harmful effects of vortex cavitation while minimizing the associated weight and manufacturing complexity.
4Reliability
If alternate blade cavitation is stabilized to reduce radial loads, then bearing life is improved, but the number of blades must be at least four
Solution Approach 1:
The blade assembly is segmented into full-size blades and partial blades, creating an effective four-blade configuration. The partial blades attached to the shroud complete the symmetric pattern needed for stable alternate blade cavitation, achieving bearing life improvement without requiring four full-size blades.
Solution Approach 2:
The design merges full-size blades and partial blades into a unified blade assembly that functions as a four-bladed configuration. This merging allows the system to achieve stable cavitation patterns and reduced radial loads while using fewer full-size blades.
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 suction performance, reduces cavitation-related vibrations, and achieves balanced alternate blade cavitation, similar to a four-bladed inducer, while maintaining low blade blockage and operational efficiency across varying conditions.
Implementation Method 1
The inducer includes a number of rapidly spinning blades to draw the liquid propellant through the inducer
Implementation Method 2
Vortices tend to form on the tips of the blades causing cavitation damage to the blades
Implementation Method 3
Alternate blade cavitation manifests as long and short vapor cavities on alternate blades
Data Source
AI summary
An inducer includes a hub having an inlet end and an outlet end. At least one full size blade has an inner edge is affixed to the hub and an outer edge. This full size blade extends rearwardly from the inlet end in a helical configuration. A partial shroud encloses a first length of the full size blade outer edge adjacent the inlet end. A second length of the full size blade outer edge that is adjacent to the outlet end is free of the partial shroud. It is within the scope of the disclosure to include short blades symmetrically offset from the two full size blades. These short blades have a short blade inner end affixed to the partial shroud and a short blade outer end extending from the partial shroud towards the hub, but terminating prior to reaching the hub.