Thermal Balance Analysis Of Dual Fuel Engine

In the face of the dual pressure of the exhaustion of fuel resources and the strict requirements of maritime regulations,the development of energy-saving and emission-reducing ship engines is particularly important for the well-development of the shipping economy and the natural environmental protection.Dual-fuel engines using low-carbon alternative fuels combined with traditional fossil fuels to run different modes in different operating scenarios are one of the effective ways to achieve energy saving,emission reduction and safety of ships.However,the internal energy consumption of the engine is not sufficiently refined,which is not conducive to guiding operation and comprehensive energy efficiency assessment.Analyzing the energy loss and combustion characteristics of each module of the dual-fuel engine from the perspective of heat balance can dig out feasible measures for more energy saving from operation and management,and it is also an important part of revealing the combustion theory of the natural gas/diesel dual-fuel engine.The heat balance analysis and simulation system can be used as a subsystem of the Marine Engine Room Simulator(MERS),the thermal balance analysis simulation system is also an embodiment of intelligent energy efficiency and digital ships;therefore,it is of great significance to conduct dual fuel engine thermal balance analysis and to develop a thermal balance analysis simulation platform.This thesis takes "CNOOC's 301" ship engine-Wartsila 9L34DF dual-fuel engine as a model,uses Matlab/Simulink as the simulation tool to establish a modular dual-fuel engine model,and verifies the accuracy and real-time performance of the model through static and dynamic simulations.In this way,the engine operation data set is obtained,and the default value is filled to solve the problem that the engine cannot be accurately analyzed for heat balance due to the lack of parameters.The engine thermal balance model uses the engine system as the control body,and establishes a thermal balance analysis module suitable for natural gas/diesel engines based on the first law and the second law of thermodynamics,and proposes specific calculation methods and implementation processes for each energy and exergy.Through the thermal balance calculation analysis of the operation process of the dual fuel engine under different working conditions and different working modes,it can be found that the energy balance and the balance of the two fuel combustion modes vary significantly with the load:the thermal efficiency is highest at 75%load in the diesel mode,It can reach about 41%;while in the natural gas mode,the thermal efficiency increases in proportion to the load increase,up to 47%.The experimental calculation results also show that the cooling effect of the two-stage air cooler is different under different loads The low load is mainly Charge Air Cooler of Low Temperature circuit(CAC-LT)cooling,and the high load is Charge Air Cooler of High Temperature circuit(CAC-HT)cooling.From the perspective of energy,the theoretical replacement ratio of natural gas to diesel is 0.854,and from the perspective of exergy,the theoretical replacement ratio of natural gas to diesel is 0.933.The irreversible loss in the two fuel modes increases with the load,and the heat transfer loss in the diesel mode is higher than that in the gas mode under the same working conditions;the efficiency of the gas mode is higher than that in the fuel mode at each load.In-depth analysis of in-cylinder combustion shows that switching from diesel mode to natural gas mode will delay the initiation of ignition and accelerate the combustion rate in the cylinder.These two changes in natural gas mode are that the thermal efficiency and efficiency of natural gas mode are higher than that of diesel mode.It is also the main factor that changes the energy balance and exergy balance of the two modes.Based on the C#language under the.NET FRAMEWORK,the secondary development of the dual fuel engine thermal balance analysis simulation system can be effectively implemented,which can effectively realize the engine thermal balance analysis simulation,dual fuel engine logic control,energy flow,real-time flow distribution and other functions,thus providing reliable data support for fuel engine energy consumption dynamic monitoring,energy efficiency optimization and other technologies.