Gas Turbine Static Component Alignment via Thermal Expansion
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Solution Overview
Problem
Existing methods for aligning structural static components in gas turbine engines, such as pilots and radially instanced geometric features, are inadequate for materials with significantly different coefficients of thermal expansion, leading to precision issues and potential engine failure due to temperature-dependent gaps and manufacturing limitations.
Innovation Solution
A dual alignment method using a pilot alignment with a large difference in diameters to mate at maximum operating temperatures and tabs and slots for alignment during assembly and cold startup, allowing for the use of materials with dissimilar thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pilot alignment is used with materials of dissimilar thermal expansion coefficients, then alignment precision is improved at operating temperature, but alignment is lost at cold startup due to large gap between ID and OD
Solution Approach 1:
The alignment system is divided into two functional segments: a pilot for precision alignment at operating temperature and tabs/slots for maintaining alignment at cold startup. This segmentation allows each component to address specific temperature conditions without compromising overall alignment reliability.
Solution Approach 2:
The invention changes the physical parameters of the alignment system by introducing a large radial gap between the pilot's OD and the mating ID, specifically designed to accommodate thermal expansion differences. This parameter change enables the pilot to function effectively only at elevated temperatures while tabs provide cold-start alignment.
2Reliability
If tabs and slots are used for alignment, then alignment is maintained under wide temperature range, but alignment precision deteriorates due to manufacturing limitations and wear
Solution Approach 1:
The alignment system is divided into two functional segments: a pilot for precision alignment at operating temperature and tabs/slots for maintaining alignment at cold startup. This segmentation allows each component to address specific temperature conditions without compromising overall alignment reliability.
Solution Approach 2:
The alignment system transitions from a static tab/slot arrangement to a dynamic system where the pilot becomes the active alignment feature at operating temperature. The tabs are dynamically deactivated (retracted from alignment function) when thermal expansion closes the radial gap, allowing the precision pilot to take over.
3Ease of manufacture
If conventional alignment methods are used, then manufacturing is simplified, but engine performance deteriorates due to inability to use dissimilar materials
Solution Approach 1:
The invention enables the use of composite material construction with dissimilar thermal expansion coefficients (e.g., titanium diffuser with nickel alloy seal plate) by providing a thermal-expansion-compensating alignment mechanism. The large radial gap in the pilot accommodates the differential expansion, allowing high-performance material combinations without compromising alignment.
Solution Approach 2:
The invention changes the physical parameters of the alignment system by introducing a large radial gap between the pilot's OD and the mating ID, specifically designed to accommodate thermal expansion differences. This parameter change enables the pilot to function effectively only at elevated temperatures while tabs provide cold-start alignment.
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
Enables effective alignment of components like titanium diffusers and nickel alloy seal plates, improving engine performance, reducing weight and cost, and maintaining alignment across varying temperatures.
Implementation Method 1
The advantage of the pilots is that they can center a part very precisely. The disadvantage is that the accuracy is dependent on the temperature and coefficient of thermal expansion for each material at build and all running conditions of the engine.
Data Source
AI summary
A first structural static component having an outer diameter is aligned with a second structural static component having an inner diameter to the centerline of a gas turbine engine rotating assembly. The first static component is centered inside the second static component leaving a gap between the outer diameter of the first component and the inner diameter of the second component to permit them to mate at operating temperatures. Tabs and slots are placed on the periphery of the static components to align the static components with the centerline at build temperature.