Adjustable Overflow System for Hopper Dredger
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Solution Overview
Problem
Trailing suction hopper dredgers face issues with overflow mixtures containing air, which reduce the specific weight, causing plumes that stick to the ship's hull, affect local environments, and decrease transport capacity due to resistance.
Innovation Solution
An adjustable overflow system with a collector having a horizontal top portion for radial flow and a sleeve forming an annular flow channel within the overflow tube, along with pressure sensors and actuators, controls the flow to minimize air introduction and optimize settling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the overflow flows vertically from the hopper, then the overflow volume is released efficiently, but air mixes with the overflow causing plume formation and reducing transport capacity
Solution Approach 1:
The overflow flow is redirected from a vertical path to a horizontal path using the collector and overflow tube assembly. The collector receives vertical overflow from the hopper and redirects it horizontally through the overflow tube, changing the flow dimension to prevent air mixing and plume formation while maintaining transport capacity
Solution Approach 2:
The collector acts as an intermediary device between the hopper and the overflow tube. It receives the vertical overflow flow from the hopper, redirects it horizontally, and delivers it to the overflow tube, serving as a mediator that transforms the flow direction and prevents harmful air mixing
2Productivity
If the overflow velocity is increased to improve transport capacity, then more water is discharged, but air resistance increases reducing effective capacity
Solution Approach 1:
The collector and overflow tube assembly serve as an intermediary system that enables high-velocity horizontal flow without air mixing. The enclosed horizontal flow path protects the high-velocity overflow from air resistance, allowing increased discharge rates without the energy losses that would occur in vertical open flow
3Ease of operation
If the overflow tube is made adjustable, then flow control is improved, but device complexity increases
Solution Approach 1:
The overflow tube is made adjustable in position, allowing the system to adapt to different operational conditions. The tube can be moved to optimize flow control and discharge location, providing dynamic adaptability that improves ease of operation while maintaining relatively simple device structure
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 system reduces or eliminates air in the overflow, minimizing plume formation, enhancing environmental impact reduction and transport capacity by ensuring controlled and efficient flow through the overflow system.
Implementation Method 1
a collector to collect the flow of head water entering the inlet and guide the flow to the overflow tube. The collector comprises a substantially horizontal top portion which delineates a top of the flowpath for head water into the collector to ensure substantially radial flow into the collector
Implementation Method 2
At least one of the overflow tube and the inlet is adjustable for controlling flow into the overflow system
Implementation Method 3
The sleeve, an inner side of the overflow tube and/or the collector form a flow channel through the overflow tube. The flow channel helps to further guide flow through the system, reducing the flow area and thereby reducing or eliminate the introduction of air into the flow
Implementation Method 4
The mixture is reduced in speed when in the dredger hopper, and this speed reduction allows for the settling of components suspended in the mixture
Implementation Method 5
Due to the generally vertical flow orientation of the overflow, the cross-sectional area of the overflow and the velocity, the overflow volume typically mixes with air. This mixture can reduce the specific weight of the mixture
Implementation Method 6
This mixture, which may also contain lighter particles which have not settled, and the interactions between the overflow volume released, the hull, propellers, speed of the vessel and currents; can form a plume in the wake of the dredging process
Data Source
AI summary
An overflow system for a hopper dredger comprises an overflow tube; an inlet for taking in head water from the hopper; and a collector to collect the flow of head water entering the inlet and guide the flow to the overflow tube. The collector comprises a substantially horizontal top portion which delineates a top of a flowpath for head water into the collector to ensure substantially radial flow into the collector. At least one of the overflow tube and the inlet is adjustable for controlling flow into the overflow system.