Performance Simulation Of Marine Natural Gas/Diesel Dual-Fuel Engine Based On RCCI

In order to cope with the increasing energy crisis and the increasingly strict emission regulations of the International Maritime Organization(IMO),research on searching for efficient and clean new marine engine alternative fuels has received widespread attention.Marine natural gas/diesel dual-fuel engines have emerged.Natural gas has become one of the most popular research directions for marine engines due to its environmental friendliness and other aspects.Due to the differences in the physical and chemical characteristics between natural gas and traditional fuels,the combustion characteristics of dual-fuel engines are different from traditional engines.In order to achieve its excellent high-efficiency and low-emission performance,this paper adopts simulation technology and targets at the Multi-dimensional numerical simulation on combustion and emission characteristics in RCCI combustion mode.Taking marine 6190 natural gas/diesel dual-fuel engine as the research object,this paper adopts CONVERGE for simulation modeling.At first,meshing is conducted on the basis of establishing a geometric model,and the results of initial conditions,boundary conditions and verification data of the simulation model are obtained through experiments.Then the simulations model is performed through calculation parameter configuration to achieve result calibration under high-load conditions,and its validity will be proved.On this basis,the effects of intake characteristics,combustion chamber shape and injection strategy on natural gas/diesel dual-fuel engine in RCCI combustion mode are discussed.It is shown that the intake characteristics have a greater impact on the ignition timing,pressure,temperature and emissions of fuel in the cylinder.Adopting the control variable method,this paper explores the effects of different supercharging pressure(1.7-2.0bar)and different intake temperature(308-323K)on the combustion process and emission index of dual-fuel engine under other conditions unchanged.It is of theoretical significance to understand the effects of intake characteristic parameters on engine performance.On the basis of the above and ensuring the unchanged compression ratio,four types of combustion chambers with different shapes are designed.CONVERGE is adopted to establish in-cylinder combustion models for simulation calculations.By analyzing the flow field distribution and emission products in the cylinder,the combustion process and the changes in emission characteristics caused by the different shapes of the combustion chamber are discussed.Finally,the effects of the single injection timing of pilot diesel on the economy and emissions of engine are further analyzed.On this basis,the quantitative analysis is performed to analyze the effects of timing and amount of pre-injection on the engine combustion and emission characteristics under the secondary injection strategy.Considering the research results comprehensively,a set of better injection parameters under the secondary injection strategy are proposed,which provides a theoretical basis for the controlling strategy of marine dual-fuel engine.