液体燃料雾化和蒸发的直接数值模拟

Confronting the practical industrial requirement and the science frontier, this project is proposed to figure out some key basic problems about atomization and evaporation of liquid fuel. A high-fidelity direct numerical simulation (DNS) method, coupled with interface capturing technique will be developed to deeply investigate the simultaneously occurring atomization and evaporation of liquid jet flow, as well as the interactions between the two processes. A coupled Level Set Method and Ghost Fluid Method will be introduced to capture the interface between liquid phase and gas phase. During this program, theoretical and numerical methods to analyze the atomization and evaporation of liquid jet will be developed first. Then evaporation of single and groups of spherical and non-spherical droplets will be analyzed by the developed numerical methods. Factors affecting the atomizing process, as well as the evaporation on the film surface of liquid jet, will be studied in detail. Based on all the work above, the inherent multi-field and multi-scale coupling mechanism of the atomization and evaporation of gas-liquid two-phase flow is expected to be illustrated clearly, through the established reliable mathematical and physical models. Theoretical understandings of the atomization and evaporation process could be very helpful to the improvement of related control technology of liquid fuel atomization and evaporation in practical industrial applications. Thus, this project will be a great promotion to development of the subject of multiphase flow at home and abroad, as well as its applications in energy conversion, power propulsion and so on.

本项目面向实际的工业需求和学术前沿，提出对液体燃料雾化和蒸发的若干关键基础问题进行研究。在技术上将发展高精度的直接数值模拟，采用Level Set Method和Ghost Fluid Method相结合的界面捕捉技术，对液体射流的雾化和蒸发及其相互作用进行深入研究。主要涉及到液体射流雾化的理论和数值方法的研究,液体射流雾化影响因素的数值模拟研究,单个球形和非球形液滴蒸发的数值模拟研究,球形和非球形液滴群蒸发的数值模拟研究,液膜表面蒸发的数值模拟研究等。力图揭示气液两相雾化和蒸发内在的多场、多尺度耦合作用机理，并构建可靠的数学物理模型，为工业应用中液体燃料的雾化、蒸发及其控制技术提供理论依据，从而推动国内外多相流学科的发展及其在能源转化、动力推进等领域内的应用。

本项目围绕液体燃料雾化和蒸发过程中的若干关键基础问题，从技术发展和机理探究两个方面展开工作。针对传统的Level Set (LS)方法存在质量不守恒的性质，本项目创新性的提出了基于界面局部曲率修正质量损失的守恒型 LS 方法。基于该方法和Ghost Fluid Method (GFM)相结合的界面捕捉技术，本项目搭建了LS/GFM-DNS数值模拟软件平台，该平台能有效地保证研究射流雾化时的精确度。在后续的研究中，本项目通过调整界面处的阶跃条件，并考虑热效应和混合效应对物体物性参数的影响，创新性地发展了液体雾化和蒸发的一体化直接数值模拟方法。机理方面，该项目首次针对旋流液膜的一次雾化进行了大规模的直接数值模拟，为探索一次雾化的机理提供了可靠的数据，为后面提出一次雾化模型提供了数据库。此外，本项目对湍流对雾化的影响作用、液滴在变形和破碎条件下的非稳态曳力、液滴撞击液膜的颈部射流及单液滴的蒸发过程进行了详细的研究。本项目已发表或录用文章11篇，资助会议若干次，主要培养研究生6人。本项目的研究内容为揭示气液两相雾化和蒸发内在的多场、多尺度耦合作用的详细机理奠定了基础，为工业应用中液体燃料的雾化、蒸发及其控制技术提供理论依据。