Self-Priming Pump Toroidal Reservoir Cavitation Control
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Solution Overview
Problem
Pumps used in Rankine type circuits, particularly in vehicles, face challenges with cavitation due to high-speed operation and pressure conditions, leading to noise, erosion, and hydraulic instabilities, and existing solutions are either bulky or disrupt fluid flow.
Innovation Solution
A compact pump design with a toric liquid tank coaxial with the pump wheel and a siphon-like connection to the input, reducing fluid speed and increasing pressure, which limits cavitation risks, and includes a turbogenerator for energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pump operates at high rotation speed to produce necessary pressure gain, then the pressure gain is improved, but the risk of cavitation increases
Solution Approach 1:
The pump impeller is nested within the toroidal liquid reservoir, with the reservoir surrounding the impeller on all sides. This nesting arrangement allows the liquid reservoir to directly supply liquid to the impeller inlet without external piping, ensuring the liquid level remains above the impeller inlet to prevent cavitation while maintaining high rotation speeds for adequate pressure gain.
Solution Approach 2:
The toroidal liquid reservoir is positioned to create a gravitational equipotential condition where the liquid level in the reservoir is maintained above the impeller inlet plane. This ensures that the hydrostatic pressure from the liquid column is sufficient to prevent cavitation at the impeller inlet, allowing the pump to operate at high speeds without cavitation damage.
2Shape
If the pump is positioned above the liquid reservoir to meet vehicle architecture requirements, then the spatial arrangement is improved, but the pump loses its prime and cannot self-start
Solution Approach 1:
The pump impeller is nested within the toroidal liquid reservoir, with the reservoir positioned vertically above the impeller. This nested vertical arrangement allows the pump to be positioned above the liquid source while maintaining the liquid level above the impeller inlet, enabling self-priming capability despite the elevated position required by vehicle architecture.
3Reliability
If a recirculation loop is added to prevent cavitation, then the cavitation risk is reduced, but the device becomes bulky and complex
Solution Approach 1:
The liquid reservoir is merged with the pump housing to form an integrated unit, eliminating the need for separate recirculation loops and external piping. The reservoir directly surrounds the impeller and supplies liquid through integrated passages, preventing cavitation while maintaining a compact, simple design suitable for vehicle applications.
Solution Approach 2:
The toroidal liquid reservoir serves multiple functions simultaneously: it acts as the liquid source, provides structural housing for the impeller, enables self-priming through its vertical arrangement, and prevents cavitation by maintaining adequate liquid level. This multi-functionality eliminates the need for separate cavitation prevention systems.
4Shape
If the pump is positioned above the liquid reservoir, then the vehicle architecture constraint is satisfied, but the available NPSH is insufficient for reliable operation
Solution Approach 1:
The pump impeller is nested within the toroidal liquid reservoir, with the reservoir positioned vertically above the impeller. This nested vertical arrangement ensures that the liquid level in the reservoir is maintained above the impeller inlet plane, providing sufficient Net Positive Suction Head (NPSH) to prevent cavitation even when the pump is positioned above the external liquid source, thereby satisfying both vehicle architecture constraints and reliable operation requirements.
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 design enhances self-priming capabilities, reduces cavitation, and allows for compact integration in vehicles, contributing to reduced CO2 emissions and efficient energy recovery.
Implementation Method 1
the connection means between the liquid reservoir and the impeller inlet forms a siphon, thus improving the self-priming capabilities of the pump
Implementation Method 2
the combination of the triplet of values (flow rate, rotation speed, pressure gain), combined with a strong space constraint, can generate local overspeeds near the leading edge of the pump blades, leading to a drop in fluid pressure that can reach the vaporization pressure. This then produces the phenomenon of cavitation (vaporization of the liquid)
Implementation Method 3
the sizing of this pump leads to objects of relatively very small size (typically diameters between 5 and 100 millimeters, preferably 5 to 50 mm) taking into account the high rotation speed (generally greater than 10,000 revolutions per minute) to produce the pressure gain necessary for the system
Data Source
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AI summary
The invention relates to a pump comprising a pump impeller (5) configured so that, during operation, the axis of the pump impeller (5) is vertical with an impeller inlet (10) disposed above an impeller outlet (11), the pump comprising a toroidal liquid reservoir (1) around the pump impeller (5) and a connection means (8) for connecting the liquid reservoir (1) to the pump impeller (5), at a connection point (9). The connection point (9) is positioned below the impeller inlet (10) so as to form a siphon, and the fluid passage cross-section (15) in the connection means (8) increases in the direction of circulation of the liquid in the pump. The invention also relates to a turbogenerator and a closed circuit comprising such a pump, as well as to the use of the closed circuit in a vehicle.