Turbojet Nozzle Ring Pads to Prevent Foot Wear and Corrosion
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Solution Overview
Problem
The issue of contact corrosion and wear at the lower part of the distributor elements in low-pressure turbines of aircraft turbojets, particularly due to friction and sulfur-induced corrosion, leads to significant maintenance costs and performance degradation.
Innovation Solution
A turbomachine subassembly with a single-piece foot and interposed pads between the foot and a clamp, which protects the foot from friction and corrosion by allowing easy replacement of worn pads, reducing maintenance costs and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the foot of the distributor element is directly contacted by the clamp to secure it, then the fixing reliability is improved, but the foot is subjected to friction and contact corrosion leading to rapid wear
Solution Approach 1:
A pad is introduced as an intermediary component between the clamp and the foot of the distributor element. The pad serves as a mediator that transfers the clamping force while protecting the foot from direct contact with the clamp, thereby preventing friction and contact corrosion. The pad can be replaced when worn, preserving the expensive foot component.
Solution Approach 2:
The clamping system is segmented into distinct components: the clamp, the pad, and the foot. This segmentation allows the pad to be a separate, replaceable component that can be optimized for wear resistance while the foot maintains its structural function. The pad absorbs the wear and corrosion effects, allowing independent replacement without replacing the entire distributor element.
2Object-affected harmful factors
If anti-corrosion coating is applied to the foot, then corrosion resistance is improved, but the coating wears off quickly due to friction from clamp contact
Solution Approach 1:
The pad acts as an intermediary that eliminates direct friction between the clamp and the coated surface of the foot. This protects the anti-corrosion coating on the foot from wearing off, allowing the coating to maintain its protective function for the intended service life of the foot component.
3Manufacturing precision
If the entire turbine module is disassembled to replace the worn foot, then complete inspection is improved, but maintenance time and cost increase significantly
Solution Approach 1:
The distributor element is segmented such that the foot can be independently replaced by replacing only the pad. This segmentation allows maintenance personnel to access and replace the worn pad without disassembling the entire turbine module, significantly reducing maintenance time while still enabling complete inspection of the foot condition.
Solution Approach 2:
The pad is designed as a consumable, replaceable component that absorbs wear and corrosion. When the pad becomes worn, it is replaced with a new pad rather than replacing the expensive foot or entire distributor element. This follows the principle of using cheaper, replaceable components to protect more valuable parts.
4Device complexity
If the clamp directly contacts the foot for secure fixation, then the structural simplicity is improved, but contact corrosion occurs leading to part degradation
Solution Approach 1:
The pad is introduced as a simple intermediary component between the clamp and the foot. This adds minimal complexity to the overall structure while effectively preventing contact corrosion. The pad can be made from materials resistant to sulfur corrosion and can be easily replaced when worn, protecting the foot from degradation.
Data Source
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AI summary
The turbomachine subassembly comprises: - at least one low-pressure nozzle ring, the nozzle ring comprising a root (38) integral with the nozzle ring; - a clamp (40) configured so as to fasten the root to a casing of the turbomachine; and - at least two pads (150) interposed between the root and the clamp, each pad being assembled in a form-fitting manner with one of either the root or the clamp.