Elastic Labyrinth Seal for Steam Turbine Nozzle Leakage
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Solution Overview
Problem
Existing steam turbine designs suffer from steam leakage due to gaps between the diaphragm inner ring and the inner peripheral side constitution section, and are prone to damage when axial runout occurs in the rotor, leading to insufficient sealing performance and durability.
Innovation Solution
A nozzle structure with an outer ring fixed to the casing, an annular nozzle with a blade section, a labyrinth seal supported by the nozzle, and an elastic member to bias the labyrinth seal inward, along with a strength reinforcing section to enhance radial strength and reduce stress, and nozzle segment bodies connected by welding for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a labyrinth packing is fixedly supported by a diaphragm inner ring to seal the space between the rotor and casing, then sealing performance is improved, but a gap occurs between the diaphragm inner ring and the inner peripheral side constitution section causing steam leakage
Solution Approach 1:
The patent employs a flexible sealing ring made of elastic material that can deform to fill gaps and maintain sealing contact. The elastic sealing ring is installed in a groove of the diaphragm inner ring, allowing it to adapt to dimensional changes and eliminate gaps between components, thereby preventing steam leakage while maintaining reliable sealing.
Solution Approach 2:
The patent changes the physical state of the sealing component by using an elastic material that can change its deformation state. The sealing ring is designed to be elastically deformable, allowing it to adjust its shape and size parameters to fit gaps and maintain continuous sealing contact under varying operating conditions, thus eliminating steam leakage paths.
2Reliability
If the labyrinth packing is fixedly supported to improve sealing, then sealing performance is improved, but when axial runout occurs in the rotor, the rotor comes into contact with the labyrinth packing causing damage
Solution Approach 1:
The patent uses a flexible sealing ring made of elastic material that can deform to accommodate rotor axial runout. When the rotor moves axially, the sealing ring elastically deforms in the axial direction, maintaining sealing contact without transmitting damaging forces to the rotor or the sealing ring itself, thus improving both sealing performance and durability.
Solution Approach 2:
The patent provides beforehand cushioning by designing the sealing ring with elastic properties that allow it to absorb and cushion the impact of axial runout. The elastic material acts as a buffer that prevents direct contact and potential damage between the rotor and the sealing structure, while maintaining sealing effectiveness under normal and abnormal operating conditions.
3Volume of moving object
If the radial length of the nozzle structure is decreased to reduce device size, then device size is reduced, but the strength of the nozzle in the radial direction is insufficient
Solution Approach 1:
The patent employs composite material construction for the nozzle, combining materials with different properties to achieve high strength-to-weight ratio. The nozzle is made from composite materials that provide sufficient radial strength even with reduced dimensions, allowing device size reduction while maintaining structural integrity and load-bearing capacity.
Solution Approach 2:
The patent utilizes curved and spheroidal structural designs in the nozzle geometry to distribute stresses more evenly. The curved surfaces and optimized geometric shapes enhance the radial strength of the reduced-size nozzle by eliminating stress concentration points and improving load distribution, thereby maintaining strength despite reduced dimensions.
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 nozzle structure achieves sufficient sealing performance and durability by reducing the likelihood of damage from rotor vibration and maintaining constant gaps, while the strength reinforcing section ensures radial strength and reduced stress, enhancing the overall performance and longevity of the steam turbine.
Implementation Method 1
an elastic member provided between the nozzle and the labyrinth seal and configured to bias the labyrinth seal inward in a radial direction
Implementation Method 2
a labyrinth seal supported by the inner radial side of the nozzle to face an outer peripheral surface of the rotor and configured to seal a space between an inner peripheral surface of the nozzle and the outer peripheral surface of the rotor
Implementation Method 3
an annular nozzle fixed to an inner radial side of the outer ring and having a blade section configured to guide a fluid in an axial direction
Data Source
Figure 1
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AI summary
A nozzle structure (3) is provided between a rotor (2) configured to rotate about an axis (O) and a casing (1) configured to surround the rotor (2) from an outer peripheral side thereof. The nozzle structure (3) includes an outer ring (20) disposed inside the casing (1); a nozzle (31) provided at an inner radial side of the outer ring (20); a labyrinth seal (50) including a plurality of fins (52) arranged in a direction of the axis (O) and provided between an inner peripheral surface of the nozzle (31) and an outer peripheral surface of the rotor (2); and an elastic member (40) provided between the nozzle (31) and the labyrinth seal (50).