Jet Pump Vibration Suppression via Extension Sleeve
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Solution Overview
Problem
Self-excited vibrations in jet pumps of boiling water reactors caused by leak flows in slip joints are challenging to suppress, especially when the leak flow is backward, as existing solutions either require component replacement or are ineffective against increased core flow rates or pressure losses.
Innovation Solution
A vibration suppressing device is installed on the jet pump, featuring an extension sleeve that forms a constant-width extension flow channel between the diffuser and inlet mixer pipe, effectively stabilizing both forward and backward leak flows without modifying the inlet mixer pipe or diffuser, thereby maintaining hydrodynamic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the core flow rate is increased to increase power, then productivity increases, but the leak flow rate through the slip joint increases causing self-excited vibration
Solution Approach 1:
A vibration suppression device is introduced as an intermediary component between the inlet mixer pipe and diffuser. This device includes a vibration suppression plate that intercepts and stabilizes the leak flow, preventing it from causing self-excited vibrations while allowing the main flow to continue uninterrupted for maintaining productivity
Solution Approach 2:
The harmful vibrational effects are extracted and isolated from the main flow system. The vibration suppression device separates the leak flow's destabilizing influence from the main hydrodynamic path, allowing high core flow rates to be maintained without transmitting vibration throughout the system
2Reliability
If the slip clearance is reduced to prevent vibration, then vibration stability improves, but the ability to accommodate thermal expansion and installation adjustment is reduced
Solution Approach 1:
The vibration suppression device divides the slip clearance into functional zones: an upstream region that maintains adequate clearance for thermal expansion and installation adjustment, and a downstream region where the vibration suppression plate stabilizes the flow. This segmentation allows the clearance to serve multiple functions simultaneously
Solution Approach 2:
The vibration suppression plate acts as an intermediary element within the slip clearance, enabling the clearance to maintain its mechanical function (accommodating expansion) while adding flow stabilization capability without reducing the clearance dimensions
3Strength
If the number of support portions of the inlet pipe is increased to enhance rigidity, then structural strength improves, but device complexity increases
Solution Approach 1:
The vibration suppression device serves as a single intermediary component that addresses vibration issues without requiring multiple additional support portions. By stabilizing the leak flow at the source, it prevents vibration-induced loosening of existing supports, maintaining structural integrity with minimal added complexity
Solution Approach 2:
The vibration suppression device enables the existing support structure to continue functioning as designed. By preventing vibration that would cause support degradation, the system maintains its original rigidity without requiring enhanced support mechanisms
4Reliability
If component replacement is performed to suppress vibration, then vibration stability improves, but ease of operation and maintenance cost worsen
Solution Approach 1:
The vibration suppression device is designed as a simple intermediary component that can be installed without replacing major jet pump components. The device includes a vibration suppression plate and support structure that attach to existing components, maintaining ease of operation while suppressing vibration
Solution Approach 2:
The invention changes the flow parameters within the slip clearance by introducing the vibration suppression plate, which modifies the leak flow characteristics to prevent vibration. This parameter change approach avoids physical replacement of components while achieving vibration suppression
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 suppresses self-excited vibrations by maintaining stable flow conditions for both forward and backward leak flows, increasing the limit flow rate for vibration occurrence and reducing pressure loss, without the need for component replacement, thus ensuring reliable operation across varying operational conditions.
Implementation Method 1
the extension flow channel has a region in which a flow channel width thereof is constant over a length
Data Source
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AI summary
There is provided a vibration suppressing device (50) for a jet pump which is located in a reactor pressure vessel of a boiling water reactor and provided with an inlet mixer pipe (33) coupled to a riser pipe (31) and a diffuser (34) coupled to the inlet mixer pipe (33) by means of a slip joint (40). The vibration suppressing device (50) is provided with an extension sleeve (53) disposed on an upper portion of the diffuser (34) of the jet pump and constitutes an extension flow channel (51) on a downstream side of a forward leak flow in a slip clearance (41) formed between an inner peripheral surface of the diffuser (34) and an outer peripheral surface of the inlet mixer pipe (33), and the extension sleeve (53) has a shape such that the extension flow channel (51) has a region in which a flow channel width (Hex) thereof is constant over a predetermined or longer length.