Counter-Rotating Impeller Reverse Thrust System
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Solution Overview
Problem
Current high mass/low-pressure liquid propulsion systems face inefficiencies and damage issues when reversing thrust, including reduced thrust efficiency, upward and downward forces causing instability, damage to sensitive environments, and cavitation problems due to the design of impellers and nozzle configurations.
Innovation Solution
A system with two counter-rotating impellers and an anti-ventilation hood, where the flow direction is reversed, allowing liquid to enter through the outlet and exit through the inlet, and a bypass mechanism to improve efficiency and prevent air ingestion, enabling effective reverse propulsion without damaging the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a deflecting bucket is used to redirect flow backwards for reverse thrust, then reverse thrust is generated, but the maximum reversing thrust is only about 40% of forward thrust
Solution Approach 1:
The patent applies inversion by redirecting the water jet flow 180 degrees backwards through the deflecting bucket to generate reverse thrust. The bucket is positioned to intercept the forward jet and redirect it completely backwards, maximizing the reverse thrust component while minimizing forward thrust loss.
2Power
If the flow is redirected through a bucket at an angle greater than 120 degrees, then reverse thrust is generated, but an upward force is generated that lifts the craft at the transom and applies a downwards force at the bow
Solution Approach 1:
The patent uses the deflecting bucket to generate an upward force component that counteracts the downward force at the bow. By positioning the bucket to redirect flow at greater than 120 degrees, the system creates a lifting moment at the transom that balances the downward moment at the bow, stabilizing the craft during reverse operation.
3Strength
If the redirected water flow is directed at a downwards angle to avoid impacting the transom, then the transom is protected, but much of the reverse thrust is negated by the current associated with the flow
Solution Approach 1:
The patent redirects the water jet in a three-dimensional trajectory that first directs flow away from the transom area, then uses the deflecting bucket to redirect a portion of the flow backwards. This multi-dimensional flow management protects the transom while maintaining reverse thrust generation through the bucket's angular redirection capability.
4Power
If the redirected water from the reverse bucket has high kinetic energy and a downwards component, then reverse thrust is generated, but the bottom is stirred up causing damage to coral reefs, underwater weed, and shell fish
Solution Approach 1:
The patent modifies the flow parameters by using the deflecting bucket to change the direction and distribution of the water jet. The bucket disperses the concentrated high-velocity stream into a wider area with reduced velocity, changing the kinetic energy parameters to minimize environmental impact while maintaining sufficient reverse thrust.
5Ease of operation
If the reverse flow is used to back-flush the grill bars, then blocked grill bars are cleared, but the high pressure head required for pressure jet systems causes cavitation on the impeller blades when higher rpm is applied
Solution Approach 1:
The patent implements periodic reverse flow operation where the deflecting bucket is activated intermittently to back-flush the grill bars rather than continuously. This periodic action clears blockages while limiting the duration of high reverse pressure conditions, reducing cumulative cavitation damage to the impeller blades.
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 achieves more efficient reverse thrust with reduced environmental impact and minimizes damage to the propulsion system, maintaining performance and preventing cavitation, even in shallow waters.
Implementation Method 1
two counter-rotating impellers mounted inside a housing... liquid enters the device through said outlet, passes through said impellers, and leaves the device through said inlet
Implementation Method 2
preventing cavitation... bypass mechanism to improve efficiency and prevent air ingestion
Data Source
AI summary
A high mass/low pressure liquid propulsion device which includes:—two counter-rotating impellers mounted inside a housing;—an inlet which in use allows inflow of liquid into the housing on a first side of said impellers; an outlet which in use allows outflow of liquid from the housing on a second side of said impellers opposite to said first side;—means for driving said impellers;—wherein the improvement comprises the provision of means for reversing the drive to said impellers, such that the direction of flow of liquid through the device is reversed and liquid enters the device through said outlet, passes through said impellers, and leaves the device through said inlet.