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Abstract

The invention is a method for increasing the buoyancy forces by suppressing / decelerating the stall of ship rudders.

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Background

International shipping is a major and growing emitter of greenhouse gas emissions. In 2018, it emitted around 1,076 million tonnes of greenhouse gases, equivalent to around 2.9% of global greenhouse gas emissions and an increase of 9.6% compared to 2012. Within the EU, shipping accounted for around 13% of greenhouse gas emissions from the transport sector in 2017. Emissions from maritime shipping are expected to increase substantially. According to the International Maritime Organisation (IMO), emissions from shipping could increase by up to 50% between 2018 and 2050 if conditions remain unchanged.

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Problem

How can a reduction in energy demand in shipping and thus a reduction in greenhouse gas emissions be achieved? In addition to switching to regenerative drive systems, there is also the possibility of optimizing existing drive systems with the aim of reducing the energy requirements of these drive systems.

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Solution

With its innovative approach, the present invention aims to reduce the energy requirement in shipping. By increasing the buoyancy, for example, the ship's rudder can be made smaller with the same rudder forces. This reduces the resistance when driving straight ahead and at small rudder angles. The increase of the lift forces is again carried out at the rudder by a delay in the stall, whereby larger angles of attack can be achieved without a detachment of the flow and a resulting drop in the lift forces.

The inventors use the principle of active flow control (AFC). In this case, the boundary layer is accelerated by "blowing out" a fluid along the surface, thus preventing it from detaching.

Another effect of this pulsed approach is the fact that the required activation energy decreases because the fluid is not constantly blown out. According to the invention, the pulsation is generated by a so-called fluidic oscillator. This is a component that generates an oscillating flow solely due to the volume flow and pressure applied.

One advantage of using fluidic oscillators is that they do not require any electrical or mechanical components such as valves. Thus, special pulse-jet oscillators are used for the present invention, as they are also able to switch the flow back and forth between two outlets.

The corresponding outlets are connected to two chambers on each rudder side, which are installed inside the rudder. This type of connection additionally guarantees that the frequency remains constant throughout the rudder. Furthermore, this ensures that all outlet pairs oscillate in the same phase.

 

The appropriate position of the "blow-out" at the rudder was chosen in such a way that it is actuated as shortly as possible before the expected detachment in order to work as energy-efficiently as possible. Due to the potential savings in fuel and greenhouse gas emissions, the present invention not only offers advantages for larger ships, but could also be of great interest for the field of recreational craft, since the approach according to the invention contributes to an increase in maneuverability, especially at low inflow velocities, e.g. when maneuvering in ports or in the river loop.

 

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Advantages

·  Reduction of flow resistance

·  Increase in maximum rowing forces

 

·  Reduction of greenhouse gas emissions

 

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Scope of application

Mechanical engineering

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Fluid mechanics