低速二冲程双燃料船用主机气缸油自燃引发爆燃机理研究

Low-speed 2-stroke dual-fuel marine engine is a new generation green ship power which reaches IMO TIER III compliance without aftertreatment. One of the kernel tasks of the engine development is to increase power density and ensure highly efficient and stable combustion. But the problem of knock caused by cylinder oil auto-ignition severely impedes the increase of mean effective pressure of the engine. The cylinder oil feeding method, gas exchange and premixed combustion process of low-speed 2-stroke engine determine the severity and particularity of this kind of knock. The cylinder oil auto-ignition inducing knock has high uncertainty and destructivity. But since the mechanism of cylinder oil breakup, evaporation and auto-ignition is still unknown, and the knock stimulating process and knock control regularity are not clear, this kind of knock is a world wide difficult theme. In order to solve this problem, the project concerning the working characteristics of low-speed 2-stroke dual-fuel engine, based on the fundamental experiment on cylinder oil physical and chemical properties, develops cylinder oil breakup, evaporation and ignition numerical simulation models which fit multiple composition, large molecular weight, and high viscosity characteristics; combining the charge motion and cylinder oil blowing tests, applies 3-D CFD to analyze the knock being stimulated by cylinder oil auto-ignition. Combining main engine performance test, the project applies measures of delaying the exhaust valve closing time, improving pre-mixture homogeneity, optimizing cylinder oil injection system, increasing cylinder oil auto-ignition temperature, etc., to control the knock caused by cylinder oil auto-ignition and investigates the knock control regularity. The fundamental research on the mechanism of knock caused by cylinder oil auto-ignition will be the theory and technology foundation of the low-speed 2-stroke dual-fuel marine engine development.

低速二冲程双燃料船用主机是新一代绿色船舶动力，提高pme并保证高效稳定燃烧是主机研发的核心任务，但"气缸油自燃引发爆燃"问题给pme的提高造成了巨大障碍。这种主机的气缸油注入、换气和预混合燃烧特性决定了该问题的严重性和特殊性。气缸油自燃引发爆燃的不确定性高，破坏力大。但气缸油破碎、蒸发、自燃机理仍不明确，其引发爆燃的机理和控制规律还不明晰，因此该问题是全新的世界性难题。为解决该问题，项目从这种主机工作特性出发，以气缸油特性实验为基础，开发高温高压环境下，符合气缸油多组分、大分子量、高粘特征的气缸油破碎、蒸发、自燃数值模型；结合缸内充量运动特性实验、气缸油吹拂实验，应用三维CFD分析气缸油引发爆燃机理；结合主机性能实验，应用延迟排气门关闭、改善预混合气均匀度、改进注油系统、提高气缸油自燃点等措施探索气缸油自燃引发爆燃的控制规律，为高水平低速二冲程双燃料船用主机的研究与开发奠定理论和技术基础。

低速二冲程双燃料船用主机是气体燃料船用主机大型化、远洋化的终极版本，掌握并发展该技术是实现海洋强国梦想的重要基石。提高功率密度并保证高效稳定燃烧是主机研发的核心任务，但“气缸油自燃引发爆燃”问题给pme的提高造成了巨大障碍。低速二冲程机的气缸油注入方式、换气特性和预混合燃烧方式决定了该问题的严重性和特殊性。二冲程双燃料主机气缸油自燃影响因素庞杂，造成爆燃的作用过程复杂，因而不确定性极高，破坏力极大。但气缸油破碎、蒸发、自燃机理仍不明确，气缸油自燃引发爆燃的作用过程和控制规律还不明晰，因此该问题成为全新的世界性难题。为解决该问题，项目从6E340低速二冲程双燃料船用主机工作特性出发，以气缸油特性实验为基础，通过气缸油破碎、蒸发、自燃实验得到了气缸油的扫气吹拂破碎特性、蒸发特性和自燃特性，并已实验结果为标定基础，开发了气缸油蒸发和自燃数值模型；应用激波管研究了天然气混合气的自燃特性；结合缸内充量运动特性实验、气缸油吹拂实验，应用三维CFD准确分析气缸油在缸内的运动特性、自燃特性和引发爆燃的作用过程；采用气-固-液流固耦合瞬态分析方法研究了燃烧室受热部件的传热特性以及高温热点对预混合气的加热作用和自由基生成过程。以上述研究为基础，研究了燃烧系统优化提高火焰传播速率、天然气喷射优化提高预混合均匀度、改善受热部件传热降低燃烧室部件表面温度、气缸油注入系统改善控制气缸油吹拂进入气缸等措施对解决技术途径，探索了主机结构及性能参数对气缸油自燃引发爆燃的影响规律，掌握了气缸油自燃引发异常燃烧的控制规律。项目为高水平低速二冲程双燃料船用主机的研究与开发奠定理论和技术基础。