Abstract: In order to obtain performance of marine natural gas/diesel dual fuel engine on natural gas timings (main timings) and pilot diesel timings (pilot timings)，according to propulsion characteristic，the experiment measured original engine operating data and emission data at 25%，50%，75% and 100% load，respectively，on pure fuel model. The finite volume method coupling semi-implicit method had been adopted to numerically analyze effects of different main/pilot timings on combustive process，turbulence intensity in cylinder，and emission of the engine. The results show that numerical simulation results are consistent with the tested pressure and emission data，the main timings makes greater impact than pilot timings on the combustion and emission，main/pilot timings decreases the peak cylinder turbulence kinetic energy，but increases the peak cylinder pressure and the peak temperature. With advancing main/pilot timings every 2° CA，NO emission respectively increases by 15.4% and 3.5%，while CH4 emissions reduces by 7.6% with advancing main timings every 2° CA，and increases by 4.6% with advancing pilot timings every 2° CA.

Key words: Main fuel timings；Pilot fuel timings；Marine dual fuel engine；Combustion and emission

摘要： 为进一步掌握主燃料天然气的喷射定时(主定时)以及引燃柴油的喷射定时(引定时)对缸内直喷船用双燃料发动机燃烧排放特性的影响规律，按推进特性在25%，50%，75%，100%负荷下进行了纯燃油模式试验，获得了发动机运行及排放数据，并通过有限容积法耦合半隐式法分别就不同主/引定时对发动机燃烧过程、缸内湍流强度以及排放产物的影响进行了数值模拟。结果显示，试验测量的压力及排放数据与对应的数值模拟结果较为一致。主定时比引定时对船用双燃料发动机燃烧排放影响程度更大。主/引定时提前都会引起缸内湍流动能峰值降低，缸内最高爆发压力和最大温度增加。NO排放量随主/引定时每提前2°CA分别上升15.4%和3.5%，而CH4排放量随主定时每提前2°CA降低7.6%，随引定时每提前2°CA升高4.6%。

关键词: 主燃料定时；引燃燃料定时；船用双燃料发动机；燃烧排放