Supercritical Liquid Fuel Combustion Mechanism

超临界液体燃料燃烧机理

基本信息

批准号：
01550163
负责人：
UMEMURA Akira
金额：
$ 1.22万
依托单位：
Yamagata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

A numerical simulation scheme was developed to disclose the unsteady evaporation and combustion processes of a single fuel droplet immersed in an otherwise quiescent gas at a various ambient gas state beyond the critical point of the fuel, which is necessary for the design of rocket motors and high speed Diesel engines. This study was carried out, based on the author's previous theoretical work on supercritical droplet combustion wherein it was found that the transition from sub- to supercritical evaporation regime can take place only if the binary diffusion coefficient relevant vanishes at the liquid gas interface in a mixture critical condition, an expression for the diffusion coefficient which satisfies this condition was proposed and the asymptotic transition feature was revealed on an analytical basis.The condition under which the droplet experiences the transition during its lifetime was identified in terms of ambient gas temperature and pressure. Other important knowledge obtained is as follows. Consistent with experimental results no singular behavior is observed in the droplet surface temperature at the transition. The core characterized by high fuel concentration preserves the liquid-like property even after the droplet has lost its liquid-gas interface. Since continuous phase change takes place in a thin layer, usual optical observation will give images as if there still exists the droplet with surface. Once the core is about to disappear, the concentration as well as the central temperature changes abruptly to assume the gaseous state. The transition is achieved far more quickly in the presence of flame which is located closer to the droplet at higher pressure. The transition epochs the change from vaporization- to diffusion-controlled combustion, accompanying an increase in flame temperature.

开发了一种数值模拟方案，以披露单个燃料液滴的不稳定蒸发和燃烧过程，该燃料液滴浸入了燃料的临界点以外的各种环境气体状态下，浸入了原本静止的气体中，这对于火箭电动机和高速柴油发动机设计是必要的。这项研究是根据作者先前对超批量液滴燃烧的理论工作进行的，其中发现只有在液体气体界面上的液体气体界面上的二元扩散系数消失在混合条件下，该条件的表达，并且可以满足该条件的表达，从而使二进制扩散系数在液体气体界面上消失了，并且可以满足该条件的表达，从而使二进制扩散系数消失了，并且可以满足该条件的表达。液滴在其生命周期内经历了过渡，这是根据环境气体温度和压力来确定的。获得的其他重要知识如下。与实验结果一致，在过渡时的液滴表面温度中未观察到奇异行为。以高燃料浓度为特征的核心即使液滴失去了液体气体界面，也可以保留液体样特性。由于连续的相变是在薄层中进行的，因此通常的光学观察将给出图像，好像仍然存在表面的液滴一样。一旦核心即将消失，浓度以及中央温度突然变化以假定气态状态。在较高压力下靠近液滴的火焰的存在下，过渡的速度更快。过渡时期从蒸发变为扩散控制的燃烧，伴随着火焰温度的升高。