Study On Ship Energy Efficiency Based On Trim Optimization

Energy conservation and emissions reduction is the primary strategic measure to solve the problem of environmental pollution and rising operating cost for the shipping industry. As early as in the 59th MEPC meeting, IMO proposed that EEOI could be used as the new standard to measure the efficiency level of operating vessel.This article selects a handy-size tanker as the target ship, adopts the method of Fluent numerical modeling and Simulink simulation, analyses the revolution of main engine, ship draft and trim change impact on the target vessel operating efficiency, and compute the best trim raising the operating efficiency level of target vessel. For energy conservation and emissions reduction of trading ships, explore a more convenient new way.First, establish a numerical towing tank of ship model. Then, conduct the calculation by the commercial software Fluent. In this paper, the VOF multiphase model based on the open channel model, RNG k-ε turbulence model and RANS are used. Through the three-dimensional extrapolation of ship resistance, obtain the hydrostatic running resistance of the target ship under different float state. Second, establish the quasi steady state simulation of ship energy efficiency which contains ship motion module, resistance module, EEOI module and marine propulsion plant system module, and analysis the n-Vs-EEDI relationship. By comparing the simulation results with those of real ship trial data, analysis and optimize the target vessel operating efficiency. Finally, it comes to a conclusion that slowdown and full navigation are important measures to reduce EEOI in the sailing schedule; between the 86%-90% of the target ship revolution, there is an insensitive area of speed-energy efficiency; under the condition of the ship loading capacity to reduce, slowdown has better energy saving effect; target ship sailing on the stern trimming 0-4.5 m range, can reduce EEOI values, and shorten the operating time; on the basis of relevant IMO convention, the safety stern trimming range of target ship is 0-2.61m; at the stern trimming 2.61m, the target ship energy conservation and emissions reduction effect is best, hydrostatic running resistance decreased by 1.9%, EEOI reduced by 0.8%.In this paper, the optimization method of target vessel operating efficiency is applicable to most of trading ship, and relatively quick and convenient. The proposed method to reduce EEOI, has strong maneuverability and important reference value for energy conservation and emissions reduction.