Aircraft Turbomachine Labyrinth Seal Preformed Slots
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Solution Overview
Problem
Aircraft turbomachines experience premature maintenance due to the 'wandering' phenomenon, where rotor blades self-engage with abradable coatings, leading to increased radius and tangential force, causing damage and rotor-stator contact, resulting in costly repairs.
Innovation Solution
A labyrinth-type sealing device with preformed annular slots upstream of the rotor lips in the stator coating, which receive the lips during axial displacement, interrupting contact and preventing further axial travel, thus limiting the wandering phenomenon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor blades self-engage with the abradable coating during operation, then the sealing effect is improved by forming grooves in the coating, but the tangential force increases causing blade bending and wandering phenomenon that leads to damage
Solution Approach 1:
The patent applies preliminary action by pre-forming grooves in the abradable coating before the rotor operates. These grooves are created during the coating application process rather than during operation. When the rotor starts, the lips immediately engage with the pre-formed grooves instead of having to cut new grooves, which eliminates the self-engagement phenomenon and the associated tangential forces that cause blade bending and wandering.
Solution Approach 2:
The pre-formed grooves act as an intermediary structure between the rotor lips and the abradable coating. Instead of the lips directly cutting into the coating material (which generates harmful tangential forces), the pre-formed grooves provide a prepared pathway that guides the lips through the coating with minimal resistance and force generation.
2Reliability
If the lips continuously contact the coating to maintain sealing, then the seal effectiveness is improved, but the axial displacement of the rotor causes increased tangential force and wandering
Solution Approach 1:
The pre-formed grooves extend axially through the coating to create a continuous engagement path for the rotor lips. This preliminary structure ensures that even when the rotor experiences axial displacement, the lips remain engaged with the grooves rather than losing contact and then violently re-engaging, which stabilizes the rotor's axial position and prevents wandering while maintaining sealing effectiveness.
3Duration of action of stationary object
If the coating is made harder to resist wear, then the coating durability is improved, but the tangential force during self-engagement increases causing more blade bending
Solution Approach 1:
The pre-formed grooves eliminate the need for the rotor lips to cut into the coating during operation, regardless of the coating's hardness. This preliminary preparation of the engagement path means that even very hard, durable coatings can be used without increasing tangential forces, because the grooves are already created and the lips simply follow the pre-established path rather than forcing their way through the material.
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 preformed slots effectively stop the axial movement of the rotor, preventing damage and rotor-stator contact, thereby reducing maintenance costs and extending the lifespan of turbomachine components.
Implementation Method 1
The friction of the lip on the coating creates an annular groove in the coating
Implementation Method 2
the coating comprising an internal cylindrical surface extending around the lips and which is able to contact the lips to form annular grooves extending around the axis by friction
Data Source
AI summary
A labyrinth-type sealing device for an aircraft turbomachine includes a rotor with at least one external annular lip. The device further includes a stator with an annular coating made of abradable material with extends around the lip and which is configured to cooperate in operation with the lip in order to form a labyrinth-type seal with respect to a flow of gas flowing through the rotor axially from upstream to downstream. The coating has an internal cylindrical surface that extends around the lip and is configured to contact the lip in order to form, by friction, an annular groove, and, upstream of the lip, a preformed annular slot.