Tapered Partial Nozzle Inlet Prevents Propeller Ventilation
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Solution Overview
Problem
In shallow water conditions, propellers on inland vessels experience ventilation, leading to inefficient propulsion and maneuverability due to air intake, which is exacerbated by low water levels and the need for smaller cargo operations, and existing solutions like tunnels increase flow resistance and power requirements.
Innovation Solution
A jet propeller design featuring a tunnel nozzle with a partially coaxial nozzle inlet that tapers away from the propeller, preventing air suction and formed in a peripheral section around the axis of rotation, combined with a Kort nozzle for improved flow efficiency, reduces ventilation and maintains constant drive output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tunnel nozzle completely encloses the propeller circumferentially, then ventilation is prevented, but flow resistance increases and power requirements increase
Solution Approach 1:
The tunnel nozzle is segmented into different functional sections: a first tunnel section with complete circumferential enclosure for ventilation prevention, and a second tunnel section with partial enclosure to reduce flow resistance. This segmentation allows the nozzle to prevent ventilation where critical while minimizing energy loss in other areas.
Solution Approach 2:
Different sections of the tunnel nozzle have different enclosure qualities tailored to their specific functions. The first tunnel section has full circumferential enclosure to prevent air intake at the propeller suction side, while the second tunnel section has reduced enclosure to allow better water flow and reduce drag, optimizing the balance between ventilation prevention and energy efficiency.
2Reliability
If a tunnel nozzle is used to prevent ventilation, then propeller efficiency is maintained, but the cross-sectional area in the underwater hull area increases
Solution Approach 1:
The tunnel nozzle is divided into two sections with different cross-sectional characteristics. The first section has a larger cross-section necessary for ventilation prevention, while the second section has a reduced cross-section that decreases the overall underwater profile and flow resistance, thus reducing drag without compromising the ventilation prevention function.
Solution Approach 2:
The tunnel nozzle transitions from a fully enclosed three-dimensional structure to a partially open structure in the second section. This dimensional change reduces the cross-sectional area presented to the water flow, decreasing drag while maintaining the essential ventilation prevention capability in the critical first section.
3Power
If conventional nozzles are used on rudder propellers, then thrust is increased, but ventilation occurs at shallow submersion depths
Solution Approach 1:
The tunnel nozzle for rudder propellers is segmented with the first section providing complete circumferential enclosure to prevent ventilation at shallow depths, while maintaining the thrust-enhancing properties of a nozzle structure. This allows rudder propellers to operate effectively in shallow water without the ventilation problems that plague conventional nozzle designs.
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 prevents ventilation, maintaining thrust and torque consistency, ensuring safe and efficient operation at low diving depths without conventional tunneling, and can be retrofitted onto existing systems.
Implementation Method 1
the tunnel nozzle has a nozzle inlet on the suction side of the propeller which is designed to be at least partially coaxial with the rotational axis, that the nozzle inlet tapers in the direction facing away from the propeller, and that the nozzle inlet, starting from a twelve o'clock position, is designed only in a circumferential partial section around the rotational axis
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a jet propeller (1) for a watercraft, comprising a propeller (2) which is designed to be rotatable with respect to a rotational axis (A); and a tunnel nozzle (3) which completely encloses the propeller (2) at least along its longitudinal extent with respect to the rotational axis (A) on the circumferential side, wherein the tunnel nozzle (3) has a nozzle inlet (6) on the suction side of the propeller (2) which is designed to be at least partially coaxial with the rotational axis (A), wherein the nozzle inlet (6) tapers in the direction facing away from the propeller (2), and wherein the nozzle inlet (6), starting from a twelve o'clock position, is designed only in a circumferential partial section around the rotational axis (A).