船用柴油机喷雾减速过程的现象学模型构建与试验验证

Phenomenological combustion model is the most practical approach for parametric study on combustion control of diesel engines, and has been applied for developing marine diesel engines as an important tool. As a prerequisite of the phenomenological combustion model development, phenomenological spray models can not describe the spray behavior during the decelerating process after the end-of-injection (EOI), which reduces the prediction accuracy of phenomenological combustion model on combustion process of diesel engines with new concept combustion modes. Thus, the aim of this study is to develop a phenomenological spray model based on theoretical research and experimental validation, which is able to describe the spray decelerating process. This work will be the basis of phenomenological diesel combustion model development, furthermore supply the theoretical and technical support for our independent research and development of high-efficient and clean marine diesel engines. In this study, according to the analysis of the diesel spray propagation process using the momentum theory and turbulent jet theory, especially for the spray decelerating process after the EOI, then the phenomenological calculation method of spray penetration and air entrainment rate will be proposed in for constant and variable injection rate cases. Meanwhile, the investigations on high resolution imaging technology of schlieren will be performed. Based on that, the spray penetration including spray during decelerating process under non-combustion conditions will be measured, and then the validation and optimization of the developed spray model will be carried out. The phenomenological spray model developed in this study can not only be used for diesel sprays, but also has the potential to be popularized for fluid jets in other power plants.

现象学燃烧模型是开展柴油机燃烧控制参数化研究最为实用的手段，已经成为船用柴油机开发的重要工具。但是，作为构建现象学燃烧模型的基础，现象学喷雾模型还无法描述燃油喷射结束后喷雾的减速过程，严重降低了现象学燃烧模型对新概念燃烧模式下柴油机燃烧过程预测的准确性。因此，本课题旨在通过理论研究和试验验证建立能够描述喷雾减速过程的现象学喷雾模型，为现代先进柴油机的现象学燃烧模型开发提供建模基础，为我国自主研发高效清洁的船用柴油机提供理论与技术支持。研究主要利用动量理论和湍流射流理论对柴油喷雾的发展过程进行分析，重点针对燃油喷射结束后喷雾的减速过程，在恒定和非恒定喷射率情况下，提出能够准确计算喷雾贯穿长度和空气卷吸率的现象学计算方法。研究高清晰度的纹影成像技术，在非燃烧条件下测量喷雾减速过程中的贯穿长度，从而验证和优化喷雾模型。该现象学喷雾模型不仅适用于柴油喷雾，也可以向其它动力装置内流体射流推广。

本项目通过理论研究和试验验证建立能够描述喷雾减速过程的现象学柴油喷雾模型。项目首先面向船用柴油机喷雾可视化试验，开发了具有170mm可视直径的大视场喷雾测量试验系统，提出了多喷孔喷雾反射式阴影成像技术，获得非恒定喷油率条件下喷雾图像。首次利用可调谐激光光谱技术测量水蒸气浓度，从而实现可蒸发柴油喷雾贯穿距离的准确测量。基于试验分析与验证，开发了恒定喷射率的现象学喷雾模型，推导了喷射结束后喷雾贯穿距离的解析式。进一步定义了非恒定喷射率条件下喷雾结束时刻和有效喷射速率，开发了非恒定喷射率情况下现象学喷雾模型，为新燃烧模式下喷雾混合和火焰的分析奠定了理论基础。在此基础上，将所开发的现象学喷雾模型应用到多次喷射条件下的燃烧过程分析与仿真。同时，针对重油喷雾，考虑了粘性对喷雾前端速度和浓度分布的影响，将模型推广至重油喷雾贯穿距离的评估。本项目的研究为新技术条件下柴油机现象学燃烧模型的开发提供建模基础，支撑我国现代先进船用柴油机的自主创新与研发。