LNG气化温度对船用天然气/柴油双燃料发动机燃烧排放的影响

Effects of LNG Gasification Temperature on Combustion and Emission Characteristics of Marine Dual Fuel Engines

关键词:  LNG气化温度  船用双燃料发动机  近壁温度  燃烧排放

Key words:  LNG gasification temperature  Marine dual fuel engines  Near-wall temperature  Combustion and emission

摘要:

为了获得液化天然气(LNG)气化温度对船用天然气/柴油双燃料发动机性能的影响规律，简述了船用天然气/柴油双燃料发动机CH4排放过高的原因与措施，对双燃料发动机按推进特性在25%，50%，75%，100%负荷下燃用20oC气化温度下的LNG进行了试验，获得了数值模拟的初始条件及排放数据，并通过数值模拟的方法就不同LNG气化温度对发动机缸内湍流强度，近壁温度，燃烧过程，以及排放产物的影响进行了研究。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。LNG气化温度降低，引起缸内平均湍流动能峰值上升，近壁区域的对流换热系数增大，近壁温度升高，改善了燃烧效果，有利于降低CH4和CO₂的排放，同时NO降低22%，碳烟排放量降低67%。

Abstract:

In order to obtain the performance of marine natural gas/diesel dual fuel engine on different liquefied natural gas(LNG) gasification temperature，the reasons and measures of the high CH4 emission of marine dual fuel engines had been presented. According propulsion characteristic，the experiment measured original engine operating data and emission data at 25%，50%，75% and 100% load under 20oC of LNG gasification temperature. Numerical simulation method had been adopted to analyze the effects of different LNG gasification temperature on the cylinder turbulence intensity，near-wall temperature，combustive process and emission of the engine. The results show that numerical simulation results are consistent with the tested pressure and emission data，the decreased LNG gasification temperature reduces the CH4 and CO₂ emissions，increases the peak of mean cylinder turbulence kinetic energy，heat transfer coefficient and temperature of the near-wall，improves combustion，also NO emission reduces 22%，Soot emission reduces 67%.