Hydrodynamic Retarder Flow Path for Low Drag and Bearing Cooling
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Solution Overview
Problem
Existing hydrodynamic retarders face challenges in reducing drag power and ensuring uniform lubrication and cooling, especially during non-braking operations, as residual working fluid generates heat and braking torque, and existing solutions do not effectively manage fluid levels.
Innovation Solution
A hydrodynamic retarder design featuring a rotor and stator in a two-part housing with tap holes on the rotor to divert a partial volume flow into an annular gap between the rotor and stator, reducing drag losses by disrupting the meridional flow and ensuring efficient lubrication and cooling through a controlled fluid circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the rotor and stator are spaced apart in non-braking operation, then the internal resistance is reduced, but residual working fluid still generates heat and braking torque
Solution Approach 1:
The patent extracts the residual working fluid from the working chamber using a skimming device with a skimming bore. This removes the source of harmful meridional flow and heat generation while maintaining the spaced-apart rotor-stator configuration for low internal resistance.
Solution Approach 2:
A lubrication channel is introduced as an intermediary pathway between the pressure side of the suction pump and the bearing. This channel ensures continuous lubrication and cooling of the rotor shaft bearing without requiring the pump to run continuously, thus reducing power loss while preventing overheating.
2Loss of energy
If the suction pump is activated only intermittently, then power loss is minimized, but uniform lubrication and cooling of the bearing is not ensured
Solution Approach 1:
The lubrication channel is pre-configured to direct working fluid from the pressure side of the suction pump directly to the bearing. This preliminary arrangement ensures that lubrication and cooling are automatically provided whenever the pump operates, eliminating the need for continuous pump operation while guaranteeing reliable bearing protection.
3Quantity of substance
If excess working fluid is drained using a skimming device, then the fluid level is controlled, but drag power is not sufficiently reduced
Solution Approach 1:
The patent segments the working fluid removal process into two distinct pathways: a skimming bore for draining excess fluid near the outer diameter, and tap holes for removing residual fluid near the inner diameter. This segmentation allows comprehensive fluid level control and complete elimination of meridional flow, achieving minimal drag power.
Solution Approach 2:
The patent extends the fluid removal approach from a single radial dimension to multiple dimensions by positioning skimming bore and tap holes at different radial locations. The skimming bore operates at the outer radius while tap holes operate at the inner radius, creating a multi-dimensional fluid control strategy that maximizes drag reduction.
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 effectively reduces drag power and maintains uniform lubrication and cooling by diverting working fluid flows, minimizing heat generation and power loss, even during non-braking operations.
Implementation Method 1
This meridional flow transmits a torque – also known as the retarder's braking torque – from the rotor to the stator
Implementation Method 2
Various measures are used to achieve this, such as rotor displacement or the use of baffles positioned between the stator and rotor when inactive. All these measures have in common that they disrupt the meridian flow that develops during idling, thus reducing drag torque.
Implementation Method 3
This is the only way to ensure the lubrication and cooling of the rotor shaft bearings on the retarder side, which rotate continuously at the gearbox speed even when the brakes are not engaged
Implementation Method 4
Excess working fluid must therefore be drained even when the brakes are not in operation. This is ensured by a skimming device.
Data Source
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AI summary
A hydrodynamic retarder is proposed comprising a rotor and a stator arranged in a two-part housing, a rotor housing part and a stator housing part, wherein the rotor and stator form a torus-shaped working chamber which can be filled with a working medium via an inlet channel and/or a pump and emptied via an outlet channel and/or a return channel, wherein the return channel connects a skimming bore in the rotor housing to a tank so that working medium can be discharged from the working chamber, wherein the rotor is slidably positioned on a retarder shaft and can be moved from a non-braking operating position to a braking operating position.According to the invention, it is proposed that means are provided by which a volume flow can be discharged from the torus-shaped working space, wherein a partial volume flow can be directed through a running gap between rotor and rotor housing part into an annular gap, through which the partial volume flow returns to the working space.