Study On Combination Optimization Of Multiple Thermodynamic Cycles For Marine Main Engine Waste Heat Power Generation

Under the background of energy shortage,energy conservation and emission reduction has become an important research goal of all enterprises and researchers in the shipping industry.For large low-speed and two-stroke marine diesel engines,it is an effective way to recover the waste heat and generate electricity from the exhaust gas of diesel engines by adopting some thermal–cycle methods,such as Steam Rankine Cycle（SRC）,Organic Rankine Cycle（ORC）,Karina Cycle（KC）and combined thermal cycle,which are good for the diesel engine field and have been preliminarily applied.These cycles use special working medium to exchange heat with the exhaust of the main engine,and the heat energy is converted into mechanical energy by the steam turbine and then be generated by the generator.The waste heat recovery system based on them has showed high efficiency and low cost properties.According to different grades of heat sources,they have their own advantages,and have a broad prospects for achieving cascade recovery power generation of marine main engine.This thesis intends to take CMD MAN B＆W-8S90ME-C10.2 low-speed two-stroke marine diesel engine as the target engine,in order to explore the combined thermal cycle system which can be used for exhaust waste heat recovery power generation,in this case the energy efficient utilization of the target engine could be achieved.The main work and achievements of this paper are as follows:（1）Aiming at the SRC,ORC and KC,the simulation models of different heat source types and different heat source temperatures were established by using ebsilon software,in which provided the model basis for the subsequent simulation analysis.（2）This thesis used the Principal Component Analysis（PCA）to analyze the simulation data.A comprehensive evaluation index system was established to evaluate the SRC of flue gas at 330～500℃,ORC of hot water at 70～190℃,KC of flue gas at180～315℃and KC of hot water at 172～250℃,which provided an evaluation standard for the characteristic parameters analysis and the optimal combination of the combined thermal cycle system.（3）Used Orthogonal Test（OT）,we selected five characteristic parameters affecting cycle efficiency,and for three cycles,we horizontally compared the influence weight of each characteristic parameter on the cycle efficiency under the fixed heat source temperature,longitudinally analyzed the weight change of single characteristic parameter with different heat source temperature,which provides a reference for parameter adjustment of each cycle and the combined cycle.（4）Used self-built model,we maked cycle selection with the cascade utilization of waste heat as the guide,the power generation as the target.Compared the comprehensive evaluation indexes for the same cycle,as well as compared power generation efficiency for different cycles,we have optimized and analyzed the combined thermal cycle system for the target main engine,and realized the optimal combination of the exhaust waste heat cascade recovery for the target main engine.The research results of this thesis explored the optimal combination of the combined thermal cycle system for the low-speed two-stroke marine diesel engine waste heat power generation,which is conducive to the exhaust waste heat cascade recovery generation of the marine main engine,and serve for the energy saving and efficient operation of the ship.