The Mathematical Modeling And Simulation Reasearch Of Marine Low-Speed Diesel Engine And Waste Heat Recovery System

Commercial vessels consume large amount of fuel oil in the world.At the same time,for reducing CO₂emission and mitigating greenhouse effect,International Maritime Organization（IMO）proposed the EEDI act.The owner should pay a certain amount of fines to compensate for the damage to the environment if energy utilization efficiency of the vessel is lower than the required limitation.Facing with the increasingly stringent emission regulations,the waste heat recovery technology of marine diesel engine has become a hot spot in the field of Ship Research at home and abroad.In this paper,the 6S50ME-C8.2 low speed two stroke marine diesel engine and its waste heat utilization system are taken as the whole research object,taking the waste heat recovery method of combined heat recovery of power turbine and waste heat boiler to recover the energy of exhaust.The mathematical models of the diesel engine and the waste heat boiler were established according to the thought of modular modeling,the simulation model was built based on the MATLAB/Simulink simulation platform,and the accuracy of the simulation model was verified according to the experimental data.According to results,the steady-state simulation model of a diesel engine and boiler model is very close to the value and the test value,consistent with the simulation results and the actual dynamic characteristics,real time simulation model has good ability,can meet the engineering requirements of the simulation time and accuracy.In this paper,the simulation models of the power turbine and the dual pressure steam turbine were established,and the simulation model of whole system consisting of the marine diesel engine and the waste heat recovery equipments was built by connecting the simulation model of each device according to the parameter transfer relationship.The steady state simulations were carried out under the different host load and the different ambient temperature,at the same time the research of the dynamic responses of main parameters of unit were studied under three conditions including the load decreasing,the load increasing and the load continuous changing.The results show that with the mutation of unit load,the variation trends of the turbine power,the steam turbine power and the total power of the waste heat utilization system are the same with that of engine load.Based on the simulation model,the heat recovery potential of waste heat utilization system under different working conditions was calculated.The result shows that,compared to the power turbine,waste heat recovery potential of waste heat boiler and steam turbine is larger,the optimization of waste heat boiler and steam turbine as waste heat the key to optimize the performance of the system,to achieve a multiplier effect.At the same time,even if the host computer can reduce the thermal efficiency of the host,but after the installation of waste heat utilization system,the total thermal efficiency can be improved,and the purpose of energy saving and emission reduction can be achieved.The research results of this paper can provide reference for the design of the marine diesel engine waste heat recovery system,and lay the foundation for the strategic research of the control system.