Diffuser Nozzle Vane Sealing via Elastic Metal Sheet
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Solution Overview
Problem
The existing diffuser-nozzle assemblies in turbomachines face issues with air flow disturbance and vibration due to varying clearance between the nozzle vanes and the casing during different flight stages, leading to inefficient air feeding to the combustion chamber.
Innovation Solution
An elastically deformable annular metal sheet is interposed between the radially outer ends of the nozzle vanes and the outer casing, ensuring continuous contact and sealing, thereby absorbing vibration and maintaining air flow integrity across all flight stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If clearance is provided between the radially outer ends of the vanes and the outer casing when cold, then the casing is protected from excessive stress, but air can flow between the vanes and casing during certain flight stages, disturbing the air flow to the combustion chamber
Solution Approach 1:
An elastically deformable annular metal sheet is introduced as an intermediary element between the radially outer ends of the nozzle vanes and the outer casing. This metal sheet maintains sealing contact to prevent parasitic air flow while distributing the contact forces to protect the casing from excessive stress during thermal expansion.
Solution Approach 2:
The metal sheet utilizes elastic deformation as a parameter change mechanism. When the nozzle expands thermally, the metal sheet deforms elastically to maintain contact between the vanes and casing, ensuring continuous sealing while accommodating the expansion movements without transmitting excessive forces to the casing.
2Manufacturing precision
If the cold clearance at the tops of the vanes is defined for cruising stage, then the vanes contact the casing during cruising, but during other flight stages the vanes either do not contact the casing allowing air leakage or exert excess pressure on the casing
Solution Approach 1:
The system transitions from a static clearance design to a dynamic one where the metal sheet can deform elastically. This allows the sealing interface to adapt continuously to different thermal expansion states corresponding to various flight stages, maintaining both sealing and controlled contact forces across all operating conditions.
Solution Approach 2:
The metal sheet's elastic deformation capability allows the system to accommodate parameter changes in thermal expansion across different flight stages. The sheet deforms to maintain optimal contact between vanes and casing regardless of the expansion state, ensuring consistent sealing and vibration damping throughout all flight conditions.
3Stability of the object's composition
If the radially outer ends of the vanes are not pressed against the casing, then the nozzle is subjected to vibration, but if pressed against, air can leak between the vanes and casing
Solution Approach 1:
The metal sheet serves as a mediator that simultaneously addresses both vibration and sealing requirements. It provides a compliant contact surface that dampens vibrations through elastic deformation while maintaining continuous sealing contact to prevent air leakage, resolving the contradiction between vibration control and sealing integrity.
Solution Approach 2:
The thin annular metal sheet acts as a flexible element that can deform to absorb vibration energy while maintaining contact sealing. Its flexibility allows it to conform to the varying expansion gaps between vanes and casing, providing both vibration damping and reliable sealing across all flight stages.
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
The solution ensures undisturbed air flow to the combustion chamber, reduces vibration, and maintains performance consistency across various flight stages by accommodating differential expansions and preventing parasitic air flow.
Implementation Method 1
elastically deformable means are interposed between the radially outer ends of the vanes of the nozzle and the outer casing
Implementation Method 2
said means preventing air from passing between the outer casing and the radially outer ends of the vanes
Implementation Method 3
In operation, the nozzle expands radially to a greater extent than the casing
Data Source
AI summary
A diffuser-nozzle assembly mounted at the outlet from a centrifugal compressor is disclosed. The assembly includes a plurality of vanes carried by a radially inner wall forming a surface of revolution and surrounded by an outer casing, elastically deformable devices interposed between the radially outer ends of the vanes of the nozzle and the outer casing. The elastically deformable devices prevent air from passing between the outer casing and the radially outer ends of the vanes.