Hollow Blocking Rotor Flow Meter Design
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Solution Overview
Problem
Existing positive displacement flow meters, particularly those used for liquefied petroleum gas (LPG), face issues with rotor breakage and high moments of inertia, leading to energy inefficiencies and inaccurate measurements due to the use of heavy and structurally weak blocking rotors.
Innovation Solution
A blocking rotor design featuring a pair of convex and concave walls with a shaft coupled to the concave walls, where the concave walls provide clearance for rotation and are cast with gates and overflows on the concave walls to reduce material stress and weight, resulting in a lighter, stronger rotor with reduced moment of inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional solid blocking rotors are used, then structural strength is improved, but weight increases leading to high moment of inertia and slower response
Solution Approach 1:
The blocking rotor is segmented into a hollow structure with internal ribs rather than a solid structure. This divides the rotor into multiple functional parts: the outer shell provides structural strength, while the internal ribs provide reinforcement without adding excessive weight. The segmentation allows optimization of each part's contribution to strength versus weight.
Solution Approach 2:
The blocking rotor uses a thin-walled hollow structure that provides sufficient structural strength through its geometry and internal rib reinforcement rather than relying on thick solid material. This thin-film approach significantly reduces weight and moment of inertia while maintaining the necessary strength to withstand operating conditions.
2Strength
If reinforcing ribs are added to blocking rotor, then structural strength is improved, but manufacturing complexity increases
Solution Approach 1:
The reinforcing ribs are merged with the rotor body in a single integrated casting operation. The gating system is designed to fill the hollow interior and form the ribs simultaneously with the outer shell, eliminating the need for separate manufacturing steps for the ribs. This integration maintains structural strength while simplifying manufacturing.
Solution Approach 2:
The gating system is pre-designed to deliver molten material to specific locations within the hollow rotor structure, ensuring proper formation of reinforcing ribs and avoiding air traps or defects. This preliminary planning of the casting process allows complex internal structures to be formed in a single operation without excessive manufacturing complexity.
3Reliability
If heavy blocking rotors are used, then structural integrity is improved, but energy consumption increases and stopping time increases
Solution Approach 1:
The hollow structure with strategic rib placement provides structural integrity at lower weight. By segmenting the rotor into a shell-and-rib configuration rather than using solid material, the design achieves necessary strength with reduced mass, thereby lowering the moment of inertia and reducing energy requirements for acceleration and deceleration.
Solution Approach 2:
The rotor design changes the physical parameters of the structure by transitioning from solid to hollow configuration. This parameter change reduces density and moment of inertia while maintaining structural integrity through geometric optimization and rib reinforcement, directly impacting energy consumption and response characteristics.
4Ease of manufacture
If gates and overflows are placed on convex walls, then casting is simplified, but rotor strength is reduced due to material stress
Solution Approach 1:
Instead of placing gates and overflows on the outer convex walls as in traditional designs, the gating system is inverted to be located on the inner concave walls. This reversal allows the gating functions to be performed in a location that does not compromise the external structural integrity or surface quality of the rotor, maintaining strength while enabling effective casting.
Solution Approach 2:
The gating system is moved from the external surface (one dimension) to the internal cavity (another dimension). This dimensional relocation of the gates and overflows to the inner concave walls allows casting operations to proceed without creating weak points or surface defects on the load-bearing external surfaces, thereby maintaining rotor strength.
Data Source
AI summary
A flow meter is disclosed with a hollow blocking rotor. The flow meter includes a housing that has a cavity with an inlet and an outlet. The flow meter also includes a pair of displacement rotors with a blocking rotor disposed between the displacement rotors. The blocking rotor includes a pair of convex walls and a pair of concave walls. The blocking rotor further includes a shaft coupled to the pair of concave walls. Each concave wall is disposed between and coupled to a pair of opposing convex walls. The concave walls provide clearance for rotation of the displacement rotors when the displacement rotors sweep along the concave walls. The hollow configuration of the blocking rotor reduces the impedance of the flow meter.