Marine Propulsion Closed Coolant Loop for Debris Protection
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Solution Overview
Problem
Existing outboard marine propulsion systems with open loop cooling systems are prone to performance issues and early engine failure due to debris clogging and corrosion in harsh marine environments, limiting operation to clear water conditions.
Innovation Solution
A marine propulsion system with a closed coolant loop featuring two discrete lower unit heat exchangers and a surface drive extension, which includes a starboard and port side heat exchanger mounted on the submerged drive unit, a coolant reservoir, and a water pump to circulate coolant within a closed loop, preventing debris entry and enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an open loop cooling system is used, then the system is simple and cost effective, but debris clogs cooling passages and causes engine failure
Solution Approach 1:
The cooling system is segmented into two separate loops: an outer loop that draws water from the environment for heat dissipation, and an inner closed loop that circulates coolant through the engine. This segmentation prevents debris in the outer loop from entering the engine's internal passages while maintaining effective cooling.
Solution Approach 2:
Heat exchangers serve as intermediaries between the outer cooling water and the inner coolant loop. The heat exchangers transfer thermal energy from the coolant to the external water without allowing direct contact between the two fluid streams, thus blocking debris while enabling heat transfer.
2Productivity
If an open loop cooling system is used, then the system is efficient, but corrosion of aluminum channels causes plugging and engine failure
Solution Approach 1:
The cooling system separates the corrosive external water from the engine's aluminum coolant channels by implementing a closed inner loop. This segmentation protects the aluminum passages from direct exposure to salt water and environmental contaminants that cause corrosion and oxidation.
Solution Approach 2:
Heat exchangers act as intermediaries that transfer heat from the coolant to external water without allowing the corrosive external water to contact the aluminum coolant channels, thereby preventing oxidation and corrosion while maintaining cooling efficiency.
3Object-affected harmful factors
If a plastic intake screen is used, then large solids are prevented from entering, but the screen clogs with debris and causes overheating
Solution Approach 1:
Heat exchangers serve as intermediaries that filter and protect the cooling system from debris. The outer loop water absorbs debris and contaminants while the closed inner loop maintains clean coolant, eliminating the need for vulnerable plastic screens that clog easily.
Solution Approach 2:
The harmful function of debris filtration is extracted from the intake screen and relocated to the heat exchanger system. The outer cooling water loop acts as a sacrificial filter that captures debris away from the engine, allowing continuous operation without screen clogging issues.
4Adaptability or versatility
If operation in muddy or overgrown waterways is attempted, then the system must handle obstructed water, but open loop systems clog and fail
Solution Approach 1:
The cooling system is divided into an outer loop that interfaces with the harsh external water environment and an inner closed loop that remains protected. This segmentation allows the system to operate in muddy or overgrown waterways as the outer loop absorbs all debris and contaminants while the inner loop maintains reliable cooling function.
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 closed loop system prevents debris from entering coolant passageways, reduces corrosion, and maintains engine performance in harsh environments, allowing operation in shallow and obstructed waterways while extending engine life and reducing maintenance costs.
Implementation Method 1
both the starboard heat exchanger and the port side heat exchanger are each discretely mounted on the submerged drive unit of the outboard motor and in closed fluid communication with the coolant passageways within the power head of the outboard motor
Implementation Method 2
a water pump configured to circulate coolant between the coolant reservoir, the starboard heat exchanger and the port side heat exchanger, and the coolant passageways within the power head of the outboard motor
Data Source
AI summary
A marine propulsion system with a closed coolant loop is described. The marine propulsion system has a starboard heat exchanger and a port side heat exchanger that provides improved cooling and increases engine life compared with traditional open loop cooling systems, particularly in harsh environments such as salt water, brackish water, swamp, shallow or sediment and debris rich water. The two discrete heat exchangers are mounted to the lower unit of the marine propulsion system and also serve to improve hydrodynamic performance of the marine propulsion system.