Research On The Potential Of Multiform Waste Heat Recovery And Utilization Of Marine Dual-fuel Engine

With the development of science and technology and the deepening of global trade,shipping,as a clean and cheap mode of transportation,is favored by all countries.However,under the background of the serious depletion of energy reserves,continuous deterioration of ecological environment and prevailing concept of energy conservation and emission reduction,the problems of high energy consumption and pollution faced by shipping bring unprecedented challenges to scientists and manufacturing enterprises.The marine consumes a great number of fuel in operation,but only a small part of the heat is converted into useful energy to drive the marine to work,and the remaining energy is discharged into the environment in the form of exhaust,cylinder cooling water and lubricating oil.This part of waste heat energy provides great opportunities for scientists and manufacturing enterprises:efficient recovery and utilization of waste heat can significantly improve the overall thermal efficiency of marine system,reduce fuel consumption and pollution emissions.Firstly,aiming at the considerable waste heat from marine,based on the thermodynamics principle,the mathematical model of basic power cycle is established,including Brayton cycle,organic Rankine cycle,organic flash cycle and organic trilateral cycle.Then,the accuracy of simulation is verified by comparing the existing experimental data.After that,the influence of working fluid type,mixing ratio and matching mode on the performance of the dual-loop Rankine cycle is analyzed and compared,so as to determine the optimal operating working fluid and configuration scheme,providing reference information for further research in the following chapters.Subsequently,due to the excellent exergy performance of multistage heat exchange,a cascade waste heat recovery system is designed to recover considerable exhaust waste heat.Then,the relationship between the sensitivity parameters and each subsystem performance as well as the collaborative effect of subsystems on the cascade system are analyzed.As the fluctuation of heat source has a negative effect on the refrigeration cycle,a control strategy is proposed to dynamically control the latent heat entering the accumulator and the waste heat released into the refrigeration cycle.The liquefied natural gas pipeline is opened under medium-low load conditions,a large amount of cold energy is generated in the gasification process.Therefore,a multi-functional cascade cold energy recovery system is proposed.Among them,the cold energy storage system uses liquid air as the medium,stores most of the cold energy in the low-period of cold energy demand,and releases it to meet the dynamic cold energy demand after reaching the peak-period.Considering the daily sewage generated by marine,based on the principle of freezing method,the sewage can be purified with the help of cold energy.The remaining cold energy enter the cold room to play the role of food preservation.Then,the demand factor is introduced to allocate the cold energy to meet the daily needs of marine dynamic changes.After obtaining the design scheme of the integrated system,the multi-objective optimization is carried out with the exergy efficiency and investment cost as the objectives,and the most outstanding operating parameters under various working conditions are obtained.Then,the performance of the integrated system is comprehensively evaluated in terms of thermodynamic performance,economic benefit and environmental benefit.The numerical results demonstrate that compared with the original engine system,integrated system can significantly improve the overall thermodynamic performance.The system can recover the investment cost within the specified time,and has excellent energy saving and emission reduction characteristics.It provides a feasible idea for researchers and manufacturers who are committed to improving the performance of marine engine integrated system.