天然气替代率对混燃式气体机放热率的影响

Influence of natural gas substitution rate on heat release rate of marine dual fuel engine

为了研究船用混燃式气体机的燃烧放热特性,本文提出采用三条Vibe曲线模拟混燃式气体机的燃烧放热率方式,在Matlab/Simulink平台上建立相应的缸内过程模型,并根据该模型提出一种新的混燃式气体机放热率的计算方法。通过该方法计算出不同替代率下的放热率,分析天然气替代率对混燃式气体机燃烧特性的影响。研究结果表明:本文建立的混燃式气体机的放热率计算模型,能够较精确地预测混燃式气体机在全工况范围内的放热率。同时,随着天然气替代率的提高,燃烧开始角延后,燃烧结束角提前,柴油的预混合燃烧阶段占整个柴油的燃烧过程中的比例相对增大。尽管混燃式气体机的排放相较于柴油机得到较好的改善,但其输出动力性降低。

To study the combustion characteristics of a marine dual fuel engine,three Vibe functions are used to calculate the heat release rate of the dual fuel engine,and a corresponding in-cylinder process model is built in Matlab/Simulink. A new method is then proposed to calculate the heat release rate of the dual fuel engine,and the influence of the natural gas substitution rate on the combustion characteristics is analyzed. Results show that the model built in this paper can predict the heat release rate of the dual fuel engine with a high accuracy in all working conditions. Furthermore,it is also found,that with an increase in the natural gas substitution rate,the combustion start angle delays while the combustion end angle advances. In addition,the diesel pre-mixed combustion stage accounts for a larger proportion of the whole diesel combustion process. In conclusion,the dual fuel engine provides an enhanced emission performance,but the output power is reduced.