Gas Turbine Shroud Assembly Adjustable Spacers
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Solution Overview
Problem
Existing shroud liner segment mounting systems in gas turbines face challenges in accurately maintaining the clearance between the shroud and rotor blade tips, leading to uncertainty in leakage reduction and potential increased gas leakage due to movement or erosion of abradable materials.
Innovation Solution
A shroud assembly comprising arcuate segments with radially extending channels and spacers that allow precise positioning and adjustment of the shroud segments relative to the casing, using connectors and fasteners with screw threads for secure and adjustable mounting, along with optional cooling channels and seals to maintain optimal clearance and monitor air gap parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If shroud segments are mounted using hooks with limited radial translation during insertion, then assembly is simplified and segments can be individually replaced, but it becomes difficult to monitor the clearance between shroud and rotor blade tips
Solution Approach 1:
A probe is introduced as an intermediary element that extends through the shroud segment and rotor blade to directly measure the clearance gap. This probe serves as a mediator between the measurement system and the difficult-to-access clearance zone, enabling precise monitoring without interfering with the hook-based mounting mechanism
Solution Approach 2:
The shroud is divided into multiple removable segments that can be individually accessed and measured. This segmentation allows the probe to be inserted through specific segments to measure clearance at different locations around the rotor, maintaining both assembly simplicity and measurement capability
2Loss of energy
If abradable material is used to reduce gas leakage, then turbine efficiency is improved, but the material erodes over time requiring replacement
Solution Approach 1:
The abradable material is designed as a consumable component that is intentionally allowed to erode and be discarded over time. When the material wears down, the entire shroud segment containing the abradable material is removed and replaced as a unit, recovering the sealing function without needing to replace the expensive rotor blades
Solution Approach 2:
The abradable material serves as a cushioning layer that is pre-installed on the shroud segments. This material cushion protects the harder shroud and rotor blade surfaces from direct contact and wear, allowing controlled erosion that maintains clearance while protecting critical components
Data Source
AI summary
An assembly for mounting a circumferential shroud to a casing, including a plurality of arcuate shroud segments collectively forming the circumferential shroud. Each segment includes a circumferentially extending wall and a channel extending from the wall. The channel is receivable in a hole passing through a circumferential casing and has a first connector. A fastener has a head and a shank, which is receivable in the channel and has a second connector that engages with the first connector. A first spacer receives the channel and a second spacer receives the shank and sit adjacent the head of the fastener on either side of the casing. The spacers can be selected to adjust for optimal radial positioning of the shroud and of probes received within a space defined between the casing and the shroud for monitoring rotor speed and the tip air gap of a turbine rotor contained in the casing.