Centrifugal Pump Axial Force Compensation Disc
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Solution Overview
Problem
Centrifugal pumps for rocket engine combustion chambers face challenges in managing axial forces exerted by the impeller, leading to bulkiness and power dissipation in existing solutions, which compromise compactness and efficiency.
Innovation Solution
An axial force compensation disc with a diameter greater than 70% of the wheel diameter is integrated with the shaft, featuring radially oriented fins to generate a pressure drop and compensate for axial forces, while maintaining compactness and reducing mass through optimized thickness distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If an active balancing piston is integrated into the back of the impeller to support axial forces, then the axial force absorption capability is improved, but the pump size increases significantly and power is dissipated
Solution Approach 1:
The pump casing is designed to serve multiple functions: it acts as both the housing for the impeller and as a balancing element that absorbs axial forces. The casing's internal geometry, particularly the arrangement of guide vanes and the volute shape, creates pressure distribution that generates an axial force counterbalancing the impeller thrust, eliminating the need for a separate balancing piston
Solution Approach 2:
The axial force compensation function is extracted from a separate component (balancing piston) and integrated into the existing pump casing structure. By modifying the casing geometry and fluid flow paths, the casing itself generates the necessary counterbalancing force, removing the bulky additional component while maintaining force absorption capability
2Force
If bearings are sized to take up the considerable axial force alone, then the axial force support capability is improved, but the compactness of the assembly deteriorates
Solution Approach 1:
The pump casing is designed in advance to generate counterbalancing axial forces through its internal fluid dynamics. The guide vanes and volute are configured to create pressure distributions that produce an axial force opposing the impeller thrust before the fluid reaches the bearings, thereby reducing the burden on bearing size while maintaining overall force support
3Force
If bearings are used to take up axial forces, then the axial force absorption is improved, but considerable power is dissipated
Solution Approach 1:
The solution utilizes hydraulic principles by designing the pump casing and fluid flow paths to generate pressure distributions that create axial counterbalancing forces. The fluid dynamics within the casing, particularly through guide vanes and volute geometry, convert fluid pressure into mechanical force that offsets impeller axial thrust, reducing reliance on mechanical bearings and thereby minimizing power dissipation through friction
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 solution effectively compensates for axial forces without increasing the pump's size, enhancing compactness, reliability, and reducing power dissipation, while ensuring a high seal between fluids, particularly crucial for cryogenic propellants and reactive gases.
Implementation Method 1
these fins of the disc thus generate, by centrifugal effect, a pressure drop from the periphery of the disc to the at least one dynamic seal, thus limiting leaks of pressurized fluid towards the dynamic seal while ensuring an overpressure of the first face of the disc relative to its second face
Data Source
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AI summary
The invention relates to the field of centrifugal pumps, and in particular to a centrifugal pump (303, 403) including at least one impeller (303a, 403a), a rotatable shaft (302, 402) that is rigidly connected to said impeller (303a, 403a), a housing (320, 420) having an axial intake passage (325, 425), at least one first bearing (305, 405) supporting said rotatable shaft (302, 402) in said housing (320, 420), and at least one dynamic seal (311, 411) around the rotatable shaft (302, 402), the impeller (303a, 403a) being located between the at least one dynamic seal (311, 411) and the axial intake passage (325, 425) of the pump (303, 403). Said centrifugal pump (303, 403) also includes, between the impeller (303a, 403a) and the at least one dynamic seal (311, 411), an axial force compensation disk (330,430), rigidly connected to the shaft (302, 402), and having a diameter larger than 70 % of the diameter of the impeller (303a, 403a). A front surface (330a, 430a) of said disk (330, 430) faces the impeller (303a, 403a) and is connected to a bypass for pressurized fluid taken downstream of the pump (303, 403), and a rear surface (330b, 430b) faces the dynamic seals (311, 411) and has blades (330c, 430c) having a pitch that is least partially radial.