Air Turbine Starter Nozzle Retention for Wear-Resistant Assembly
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Solution Overview
Problem
Existing air turbine starters face premature wear and limited material and geometry constraints due to casting the nozzle and shroud as a single piece, which restricts material selection and increases complexity and cost.
Innovation Solution
The nozzle and shroud are designed as separate pieces with protrusions and slots or complementary elements to create physical interference, allowing for different material selection and assembly, reducing axial and rotational movement, and eliminating the need for casting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the nozzle and shroud are cast as a single piece, then structural integrity is ensured, but material selection is restricted and manufacturing complexity increases
Solution Approach 1:
The nozzle and shroud are divided into separate components rather than being cast as a single piece. The nozzle is made from materials optimized for high-temperature and high-pressure conditions, while the shroud can be made from different materials suited for structural support and cooling. This segmentation allows each component to be manufactured from the most appropriate material for its specific functional requirements.
Solution Approach 2:
The design enables the use of different materials for the nozzle and shroud, potentially including composite materials or metal-ceramic combinations in the nozzle to withstand extreme conditions, while the shroud uses conventional metals for structural integrity. This multi-material approach optimizes performance for each component's specific operational demands.
2Ease of manufacture
If the nozzle and shroud are cast as a single piece, then assembly is simplified, but manufacturing cost and complexity increase
Solution Approach 1:
By segmenting the nozzle and shroud into separate manufacturable components, each can be produced using optimized manufacturing processes (such as precision casting or machining for the nozzle, and stamping or forging for the shroud), reducing overall manufacturing complexity and cost while maintaining assembly simplicity through standardized connection interfaces.
Solution Approach 2:
The connection interface between the nozzle and shroud acts as an intermediary element that simplifies assembly. Standardized features such as flanges, bolts, or interference-fit protrusions and slots create a reliable connection without requiring complex integrated casting processes, thereby reducing manufacturing complexity while maintaining ease of assembly.
3Power
If high-pressure air flows through the nozzle, then turbine rotation is achieved, but axial load causes nozzle wear
Solution Approach 1:
Separating the nozzle from the shroud allows the nozzle to be designed as a replaceable component that can withstand high-pressure air flow and axial loads. When wear occurs, only the nozzle needs to be replaced rather than the entire assembly, thereby maintaining reliability and extending the overall system life while preserving the power generation capability.
Solution Approach 2:
The nozzle is designed as a consumable component that can be worn and replaced. The high-pressure air flow and resulting axial wear are accepted as trade-offs for maintaining the turbine rotation capability, with the nozzle being periodically replaced or recovered through refurbishment rather than replacing the entire nozzle-shroud assembly.
4Reliability
If the nozzle is constrained axially, then premature wear is prevented, but material and geometry flexibility is reduced
Solution Approach 1:
The axial constraint mechanism is implemented through the connection interface between the separately manufactured nozzle and shroud. This allows the nozzle to be constrained axially to prevent premature wear while maintaining flexibility in material and geometry selection for both components, as the constraint is achieved through the assembly configuration rather than integrated design.
Solution Approach 2:
The connection interface features (protrusions and slots, flanges, or other coupling elements) act as intermediaries that provide axial constraint to the nozzle while allowing independent material and geometry optimization for both the nozzle and shroud. These intermediary features enable wear prevention without compromising the flexibility needed for material and geometry selection.
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 design reduces wear, lowers production costs, and allows for a wider range of materials and geometries, enhancing performance and reliability while maintaining structural integrity under high-pressure conditions.
Implementation Method 1
protrusions and slots or complementary elements to create physical interference, allowing for different material selection and assembly, reducing axial and rotational movement
Implementation Method 2
A source of high-pressure air flows air through the turbine to affect a rotation of the turbine
Implementation Method 3
The air-driven turbine includes an air-driven turbine that rotationally drives the gearbox
Implementation Method 4
The air starter turbine includes a nozzle upstream of a rotatable turbine, with the nozzle guiding the flow of the incoming air to the rotatable turbine
Data Source
Figure 1
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AI summary
An air turbine starter (10) having a housing (78) defining an interior (28) with a primary inlet (32) and a primary outlet (34) to define a primary air flow path (36) from the primary inlet (32) to the primary outlet (34). A nozzle (42) is located within the interior (28) and has circumferentially spaced vanes (50). A shroud (44) is also located within the interior (28) and circumscribes at least a portion of the vanes (50). A retention mechanism (44) constrains the axial movement of nozzle (42).