Study Of Exergy Distribution Of Marine Main Engine System

With the coming of the marine times, the fuel consumption of modern shipping industries surges a lot. Chinese shipping industry is facing a severe test. Not only the amount of fuel consumption but also the whole ship designed emissions of CO2 needs to be reduced, to meet the needs of the laws and regulations promulgated by the International Maritime Organization has became an inevitable trend. It is far more important nowadays in the field of energy saving to increase the energy efficiency of marine main engine system and reduce the greenhouse gas emissions from the shipping industry.The large-scale low-speed two stroke diesel engine was chosen as research object in this article, both gas phase diagram and seiliger circulation as well as average method was integrated, the marine main engine system was divided by several subsystems in order to build the thermal performance mathematical model each other. Afterwards based on the second law of thermodynamics, gray box analysis method was utilized to build exergy distribution formula model of main energy consumpsion equipment unit (including compressor, intercooler, fuel preheater, cylinder, turbine, freshwater generator). For the depth research of distribution of the fuel consumption, the white box analysis model of main engine cylinder unit was taken into consideration.The thermal performance parameters such as temperature, pressure and mass flow was calculated by the former established formula model. The diesel type with different conditions was selected to calculate the result of thermal parameters and verify the accuracy between calculating and designing. The calculated parameters result of 6S50MC-C8 type diesel from 40% to 100% totally in 7 working conditions was utilized to calculate main engine system and equipment subsystems exergy distribution. Find out the distinguish with 50%, 70% and 100% conditions between exergy and energy flow distribution, finally the cylinder unit was calculated with different conditions to dig out the construction of cylinder unit exergy loss and the reason of its irreversible degree. The cylinder unit exergy efficiency under 100% load was 45%, irreversible exergy loss conclude mainly about combustion exergy loss, throttle exergy loss and other machine exergy loss totally was 35.7%. The figures showed that exergy efficiency raised first and then decreased from low condition to high, the highest exergy efficiency is on 90% load, recorded as 46.04%. The emphasis of energy saving was confirmed in exhaust exergy section, the exhaust exergy should be exploited above 80% load especially the best point 90% condition due to its high quality.The cylinder water cooling exergy loss also can be recycled, but its quality is quite low relatively. At last, 6S42MC7.1, 5S60MC-C8, 6S60MC-C7.1, 7S60MC6.1, 6S70MC6,12K98ME-C totally 6 type marine main engine system thermodynamic parameter was calculated in order to get 100% load cylinder exergy distribution of each type. According to the results of exergy flow analysis, the energy saving recyclable degrees and its potential could be investigated.