Study On Fuel Supply System Of Marine High Pressure Direct Injection Natural Gas Engine

In order to realize the energy diversification and reduce emissions,natural gas has become the main choice of Marine engine alternative fuel,the reliability of the marine natural gas engine fuel supply system,gas common rail pipe and the high pressure gas pipe is the safeguard to guarantee the safety of high pressure direct injection nature gas in cylinder.Based on the M26 Marine high pressure direct injection natural gas engine as the research object,design of gas fuel supply system and optimize design common rail tube,analysis the static strength of nature gas common rail pipe and the nature gas high pressure common rail pipe,to provide theoretical and engineering application for the promotion of LNG ships.The thesis first designed high pressure direct injection in cylinder natural gas fuel supply system for Marine,Selection of Marine fuel tanks,high pressure gas vaporizing supply device,shipping line,natural gas common rail pipe,natural gas high-pressure pipes etc.And then set up the natural gas high pressure common rail pipe and gas injection process calculation model of the pipes,to simulate the steady and transient injection process,simulation results show that:common rail pipe pressure fluctuations are lower than the original WP12 engine when this four kinds of short common rail pipe work stability,the greater of the volume cause smaller common rail pressure fluctuation,four volume all acceptable;during the rail pressure increased from 120 bar to 298 bar,due to the total volume increased,short common rail pipe response slowly than WP12,four solutions of short common rail transient pressure fluctuations is small in the front of the first injector;according to the statistical results of 15 cycles,the variable coefficient of first cylinder shows that,in the four kinds of short common rail pipe,the cyclic variations of gas injection amount bellows original WP12 common rail pipe.Finite element calculation model of natural gas common rail pipe,natural gas high pressure single-wall pipe and natural gas high pressure double-wall pipe is established,which is used to analyze the stress and strain of the components.The simulation results of the natural gas common rail pipe show that the maximum stress of natural gas common rail pipe appears in the round of the small holes of gas inlet manifold and outlet manifold,increasing the thickness of the common rail pipe and the fillet angle of the manifold holes can reduce the stress amplitude.The effect is more obvious when the thickness increases 1.5mm.According to the results of the calculation and specification requirements,the material F38MnVs is selected for natural gas common rail pipe.The calculation results of single-wall pipe and double-wall pipe show that the larger stress of inner pipe and outer pipe appears in the bending parts.For inner pipe,the inner diameter is smaller,the wall thickness is larger and the calculation stress is smaller.The material 0Cr18Ni9 can meet the strength requirement.For outer pipe,the inner diameter is larger.Then the total force of high pressure natural gas affecting on the wall is larger,and the wall thickness is thinner,so the high strength material F38MnVs is selected.At last,on the basis of the principle of real-valued genetic algorithm,the elite retention strategy and the crossover probability and mutation probability of adaptive change with the number of iterations are introduced which improves the convergence rate and can effectively avoiding the genetic algorithm into local optimum.The algorithm is applied to the energy management parameter optimization problem.Simulink bridge genetic algorithm and GT model information communication while vehicle simulation model as the fitness function solver and the equivalent fuel economy as the optimization target to optimize the control parameters.The optimization results show that,the optimized parameter economy is improved by 6.5%compared with the control parameters derived from engineering experience.What's more,the optimized solution set provides multiple solutions.