Safety Study On LNG High Pressure Gas Supply System Of Dual Fuel Engine

With the increasingly stringent requirements of the International Maritime Organization on ship emissions,and in the trend of requiring low carbon,low sulfur and low nitrogen emissions,ship shipping industry must take corresponding measures to meet the emission requirements.At present,ships powered by clean energy LNG can meet emission requirements while ensuring economy,so the number of LNG ships in the world is growing rapidly.The LNG carrier shall be equipped with a fuel supply system for pressurization,gasification and heating of cryogenic liquid fuel.The fuel supply system can be divided into high pressure and low pressure modes according to the use of the main engine.Among them,the fuel in the high pressure gas supply system needs gasification and heating under high pressure,and the probability of leakage accident will be higher.Therefore,the safety study of the high pressure gas supply system is of great significance.In this paper,25,000 DWT dual-fuel ice-grade bulk carrier is taken as the research object.The main engine of this vessel adopts the dual-fuel machine of Mann Company model 5G45ME-C9.5-GI and is equipped with high-pressure fuel supply system.There are many modules in the high-pressure fuel supply system,which can be roughly divided into process module and safety module.The process module includes LNG storage,transportation process,pressurization process and gasification heating process.This study will carry out parameter calculation and type selection analysis for key equipment of the process module.The safety module of high-pressure LNG gas supply system will be the focus of this paper,and the research contents are as follows:(1)The accident tree method is adopted to analyze the risk of the fuel filling process,and the risk reduction strategy is proposed.(2)Optimize the design principle of valve unit and inert gas purge to ensure the safe use of gas.(3)Calculate,analyze and optimize the design principles of ventilation system,gas detection system and fire protection system according to safety requirements,so as to minimize the harm caused by gas leakage.(4)the system classified according to the working condition of working medium inside the pipeline first of pipe diameter,wall thickness calculation and selection of pipe material,and then based on the ANSYS Workbench simulation platform using the method of fluid-structure coupling dynamic analysis was carried out on the bad working condition of special section of the pipeline,the calculation of the section stress distribution and the modal analysis,discuss the different fluid,different constraints,spacing and thickness of high pressure pipeline inherent frequency,the influence of the study can provide reference for designers to avoid pipeline resonance and vibration equipment damage.(5)the application of professional pipe stress analysis software CAESAR II of system operating mode is relatively mild,but long span double-wall pipe inside and outside the static analysis,according to a calculation result of stress and secondary stress,adjust the way of long span pipeline location and constraints,and provides reference for high pressure gas supply system of the pipe layout scheme.