Ship comprising engine
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Solution Overview
Problem
Existing BOG reliquefaction systems face inefficiencies and maintenance challenges, particularly in low-pressure engine configurations, due to the need for large capacity compressors and complex compressor arrangements, which increase manufacturing costs and maintenance complexity.
Innovation Solution
A ship engine system utilizing BOG as a refrigerant in a self-heat exchanger, with multistage compression and decompression processes, allowing BOG to be used for both reliquefaction and as fuel, and optimizing compressor capacity to simplify maintenance by using a single multistage compressor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a partial reliquefaction system uses a multistage compressor with multiple compression cylinders for high-pressure engine fuel supply, then the engine can operate with high-pressure natural gas, but the device complexity and maintenance difficulty increase
Solution Approach 1:
The multistage compressor is divided into multiple compression cylinders (first through fifth compression cylinders) that can operate independently. Each cylinder handles a specific stage of compression, allowing the system to maintain high-pressure output for the engine while enabling individual cylinder maintenance without shutting down the entire compressor system.
Solution Approach 2:
The system dynamically adjusts the operating parameters of different compression cylinders based on demand. When BOG needs to be supplied to the high-pressure engine, the compression cylinders operate at high pressure settings. When BOG is supplied to the generator or for reliquefaction, the pressure parameters are adjusted accordingly, optimizing performance for different operational modes.
2Power
If multiple compression cylinders are used in the multistage compressor, then high-pressure BOG can be supplied to the engine, but the maintenance complexity and time increase
Solution Approach 1:
The compressor is segmented into multiple independent cylinders with separate access points and mounting structures. This segmentation allows individual cylinders to be removed and serviced independently, reducing maintenance time and complexity compared to a monolithic compressor design.
Solution Approach 2:
The compressor system is designed with dynamic operational flexibility, where different cylinders can be activated or deactivated based on operational requirements. This dynamic configuration allows the system to maintain high-pressure capability when needed while simplifying maintenance by isolating specific cylinders for service without affecting the entire system.
3Productivity
If BOG is used as refrigerant in the self-heat exchanger, then reliquefaction efficiency improves, but the system requires precise temperature and pressure control
Solution Approach 1:
The system uses BOG (boil-off gas) itself as the refrigerant in the self-heat exchanger, creating a self-service cooling system. The cold BOG from the storage tank directly cools incoming warm BOG, eliminating the need for external refrigerants or complex refrigeration cycles. This self-service approach improves reliquefaction efficiency while minimizing control system complexity.
Solution Approach 2:
The system exploits the natural temperature and pressure parameters of BOG at different stages. By controlling the mixing ratio and flow rates, the system achieves efficient heat exchange and reliquefaction without requiring active temperature control systems, as the process leverages the inherent parameter differences between cold stored BOG and warm incoming BOG.
4Ease of manufacture
If a single multistage compressor is used instead of multiple separate compressors, then manufacturing cost and maintenance simplicity improve, but the compressor capacity must be precisely optimized
Solution Approach 1:
Multiple compression functions are merged into a single multistage compressor unit with multiple cylinders integrated into one housing. This consolidation reduces manufacturing costs by eliminating the need for multiple separate compressor units, multiple drive systems, and multiple sets of seals and gaskets, while maintaining the functional capabilities of staged compression.
Solution Approach 2:
The single multistage compressor is designed with universal functionality to handle multiple BOG supply scenarios: high-pressure engine fuel supply, generator fuel supply, and reliquefaction. The compressor can operate in different configurations and pressure ranges, making it a multi-functional device that replaces what would traditionally require multiple specialized compressors.
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 approach enhances reliquefaction efficiency, simplifies maintenance, and reduces costs by using BOG as a refrigerant in the self-heat exchanger, improving the overall efficiency and ease of maintenance of the BOG reliquefaction process.
Implementation Method 1
a self-heat exchanger performing heat exchange with respect to boil-off gas (BOG) discharged from a storage tank
Implementation Method 2
The BOG discharged from the storage tank and subjected to heat exchange with a refrigerant in the self-heat exchanger
Implementation Method 3
a multistage compressor compressing the BOG discharged from the storage tank and having passed through the self-heat exchanger in multiple stages
Implementation Method 4
a first decompressor expanding some of the BOG compressed by the multistage compressor and having passed through the self-heat exchanger
Implementation Method 5
the remaining BOG is sent to the self-heat exchanger to be cooled through heat exchange with BOG discharged from the storage tank
Implementation Method 6
BOG remaining after being used as fuel in the engine is reliquefied into liquefied natural gas
Data Source
AI summary
A ship comprising an engine is disclosed. The ship comprising an engine comprises: a self-heat exchanger which heat-exchanges boil-off gas discharged from a storage tank; a multi-stage compressor which compresses, in multi-stages, boil-off gas that passed through the self-heat exchanger after being discharged from the storage tank; a first decompressing device which expands one portion of boil-off gas that passed through the self-heat exchanger after being compressed by the multi-stage compressor; and a second decompressing device which expands the other portion of the boil-off gas that passed through the self-heat exchanger after being compressed by the multi-stage compressor, wherein the self-heat exchanger uses boil-off gas discharged from the storage tank and boil-off gas expanded by the first decompressing device as refrigerants for cooling boil-off gas compressed by the multi-stage compressor.