LNG Fuel Supply System with Return Flow for Boil-Off Gas Prevention
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Solution Overview
Problem
Existing fuel supply systems for ship engines using LNG face challenges in preventing system failure due to boil-off gas entering high-pressure pumps, which can disrupt smooth fuel delivery.
Innovation Solution
A fuel supply system that delivers LNG from a storage tank to a high-pressure pump via a submerged pump, pressurizes it, and then re-gasifies it using a vaporizer, while returning LNG upstream to maintain a minimum flow rate and regulating its flow to control temperature, preventing boil-off gas from entering the high-pressure pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LNG is delivered to high-pressure pump without flow rate control, then fuel supply efficiency is improved, but submerged pump cannot maintain minimum flow rate and system reliability deteriorates
Solution Approach 1:
The fuel supply system is divided into multiple independent channels: a main fuel supply channel for efficient LNG delivery and a return channel for maintaining minimum flow rate. This segmentation allows each channel to perform its specific function optimally without interfering with the other, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The return channel acts as an intermediary mechanism that recycles a portion of the LNG flow back to the submerged pump inlet. This intermediary flow ensures the pump always receives sufficient liquid to maintain its minimum flow rate requirement, preventing cavitation and ensuring reliable operation while allowing the main supply channel to operate at high efficiency.
2Temperature
If LNG flow rate is increased to prevent boil-off gas, then temperature control is improved, but pump flow rate requirement and system complexity increase
Solution Approach 1:
The system incorporates a flow rate regulator that monitors and adjusts the LNG flow rate through the return channel based on temperature conditions. This feedback mechanism automatically maintains the optimal flow rate to prevent boil-off gas formation without requiring complex manual intervention or overly complicated control systems.
Solution Approach 2:
The system changes the flow rate parameter of LNG dynamically - increasing it through the return channel when temperature rises to prevent boil-off, and adjusting it based on operational conditions. This parameter adjustment allows temperature control without permanently increasing system complexity, as the changes are made adaptively rather than through fixed complex infrastructure.
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
This solution ensures smooth fuel supply by preventing boil-off gas from entering the high-pressure pump, maintaining the LNG in a supercooled state, and reducing the risk of system failure, thus ensuring continuous operation.
Implementation Method 1
LNG is delivered from an LNG storage tank of a ship to a high-pressure pump by a submerged pump
Implementation Method 2
pressurized to a high pressure by high-pressure pump
Implementation Method 3
re-gasifying the LNG pressurized by the high-pressure pump
Implementation Method 4
Since LNG in front of the high-pressure pump can remain supercooled through control of the flow rate of LNG returned to the LNG storage tank
Data Source
Figure 1~2
Figure 3
AI summary
Disclosed are a fuel supply system and method for a ship engine. The fuel supply system for a ship engine of the present invention comprises: a submersible pump which is provided to an LNG storage tank of a ship for supplying LNG to the engine of the ship; a high-pressure pump which has the LNG supplied thereto from the submersible pump and pressurizes the same under high pressure; and a return flow channel which, at the upstream of the high-pressure pump, returns the LNG to the LNG storage tank, wherein the flow of the LNG returning through the return flow channel is controlled, and the temperature of the LNG is controlled at the front end of the high-pressure pump.