Turbine Flowmeter Bearingless Design for Low-Flow Accuracy
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Solution Overview
Problem
Turbine flowmeters face challenges in maintaining measurement accuracy at low volume flow rates due to mechanical support issues, fluid deposition, and high friction in gear transmission, which affect sensitivity and reliability.
Innovation Solution
The design incorporates a turbine with a nozzle ring and vanes positioned close to the nozzle head, a two-part holding insert with flow-diverting vanes, and a crown wheel and pinion gear system to enhance sensitivity and positional accuracy, while reducing friction and fluid deposition risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the turbine rotates freely suspended behind the nozzle head without mechanical support, then mechanical support is completely eliminated, but trouble-free electromagnetic transmission of rotational speed is often not possible, especially when the housing is made of steel or cast steel
Solution Approach 1:
A magnetic coupling mechanism is introduced as an intermediary between the turbine and the counter. The magnetic field acts as a non-contact mediator that transmits rotational motion from the turbine to the counter, eliminating the need for mechanical shafts and gears while ensuring reliable signal transmission through the steel housing.
2Device complexity
If the turbine is freely suspended without mechanical support, then mechanical support is eliminated, but at flow velocity of zero or close to zero, the position of the turbine is completely undefined
Solution Approach 1:
A balancing mechanism with counterweights is introduced to compensate for the turbine's weight and maintain its position in the fluid flow. This counterbalancing system ensures that the turbine remains in a defined, stable position even at zero or near-zero flow velocities, preventing it from floating or sinking in the fluid.
Solution Approach 2:
The turbine is pre-positioned using a positioning mechanism that establishes its correct location before flow begins. This preliminary positioning ensures that when flow starts, the turbine is already in the optimal position to be carried along by the flow, maintaining stability throughout operation.
3Device complexity
If the turbine has a central bore for the shaft, then mechanical support is provided, but a portion of the fluid is drawn through this central bore, resulting in deposition of suspended substances and minerals dissolved in the fluid
Solution Approach 1:
The central shaft bore is completely removed from the turbine design. Instead of having a central opening for mechanical support, the turbine uses a bearingless suspension system where the turbine is supported by magnetic fields or fluid dynamic forces, eliminating the source of fluid intake that causes mineral deposition.
4Ease of operation
If worm gears are used to deflect the direction of rotation by 90° and reduce revolutions, then the desired deflection and speed reduction are achieved, but worm gears have high friction, reducing measuring sensitivity at low volume flow rates
Solution Approach 1:
The mechanical worm gear transmission is replaced with a magnetic coupling system that transmits rotational motion without mechanical contact. This substitution eliminates sliding friction between gear surfaces while maintaining the ability to deflect rotation direction and reduce speed, thereby improving sensitivity at low flow rates.
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 configuration improves measurement sensitivity at low flow velocities, maintains turbine position, and reduces friction, ensuring accurate and reliable flow measurements across varying flow rates.
Implementation Method 1
the fluid flow accelerated in the gap between the nozzle head and the front of the turbine has an injector effect on the fluid present in the nozzle gap between the nozzle head and the nozzle ring
Implementation Method 2
the fluid flow acceleration that takes place in the nozzle head and the associated reduction of the pressure in the fluid
Data Source
AI summary
The invention relates to a turbine flowmeter for measuring the consumption of fluids, particularly water. The turbine flowmeter comprises a housing (1) with an inflow (2), and outflow (3) and a flow channel (4). The turbine flowmeter also comprises a measuring unit (5) for measuring and indicating the consumption. A turbine (10) with a hub (11) and a number of radial vanes (12.1, 12.2) is located inside the channel (4). A holding insert (20) is also located inside the channel (4) and is comprised of a water guide cross (20.1) and of an insert base body (20.2). The water guide cross (20.1) comprises a hub (21), radial struts (22) extending from the hub (21) to the wall of the channel (4), a nozzle body (23), which surrounds the front (14) of the turbine (10), however, a gap (17) remains through which the fluid flows, and comprises a central opening (24) in the nozzle body (23). The vanes (12.1. 12.2) of the turbine (10) are positioned near the nozzle body (23). A nozzle ring (16) connects the vanes (12.1, 12.2) and extends over the outer contour of the nozzle body (23) so that a nozzle gap (18) remains between the nozzle ring (16) and the nozzle body (23). This nozzle gap (18) communicates with the gap (17) between the nozzle body (23) and the front (14) of the turbine (10). The gap (17) and the nozzle gap (18) guide the fluid so that the turbine starts running even with the smallest flow of fluid and, even during a maximum rate of flow, keeps its position behind the water guide cross (20.1) without requiring any bearing.