Research On Load Interference Characteristics Of Marine Dual Fuel Engine

Internal combustion engine is the most widely used prime mover in transport ships,but the emission regulations in the field of ships are becoming more and more stringent,and the exhaust of traditional diesel engines is difficult to meet the current emission standards without post-processing.Natural gas has become the most likely fuel to replace diesel at present because of its advantages such as low price,clean combustion and abundant reserves.And it.The engine which uses natural gas instead of diesel as the main fuel is more and more widely used.However,the dynamic characteristic of natural gas engine is poor.When the load of the engine increases suddenly,because of its inertia,the turbocharger needs some time to adjust the air flow of the engine,so that the instantaneous air-fuel ratio decreases,NO_x emissions increases,and even knock may occur.;when the engine load decreases suddenly,the instantaneous air-fuel ratio increases,which makes the mixture into the cylinder too thin,the fuel can not be completely burned,which increases HC emissions,and even cause the engine to flameout.Many scholars have studied the dynamic behavior of the engine using natural gas as the main fuel in order to avoid knock or misfire,and reduce NO_x and HC emissions.In this paper,the crankshaft angle model of YC6K marine dual-fuel engine was built based on MATLAB/Simulink simulation platform,including cylinder working process model,intake and exhaust system model,turbocharger model and intercooler model.The cylinder pressure test was carried out on the YC6K dual-fuel engine test-bed,and the steady-state models of three operating conditions of dual-fuel engine under propulsion characteristics are calibrated according to the test data.On the basis of several steady-state models,the dynamic model of dual-fuel engine was established.In addition,the torque model of the propeller,the rotation balance model of the shafting and the governor model are added to form the dynamic simulation model of dual-fuel ship power plant.The above model was used to simulate the dynamic behavior under the propulsion characteristics,and the simulation results in the stable stage under variable working conditions were compared with the experimental results.A knock prediction model was established to calculate the loading limit of non-knock in the four loading processes among the five steady-state operating points of 42%,53%,74%,85%and 100%under propulsion characteristics.Interference was applied to the dynamic working conditions such as the stable operation of the ship,the loading stage and the load reduction stage,and the engine speed,torque and load torque in the interference state are calculated and compared with those in the non-interference state.At the same time,knock prediction is carried out for all kinds of dynamic processes,in order to provide some guidance for the control of the ship during navigation.