Study on the Atomization Gasification, Mixing and Combustuin Processes of Liquid fuel Jets in Supercritical Enironments

超临界环境液体燃料射流雾化气化、混合及燃烧过程研究

基本信息

批准号：
11650219
负责人：
UMEMURA Akira
金额：
$ 1.66万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Analyzes were made of characteristic processes involved in the combustion of sprays which are formed when liquid fuel is injected into the air whose thermodynamic state exceeds the critical point of the fuel. The following were found. ( 1) Despite the convectional belief that droplet auto-ignition delay time shortens monotonically with increasing pressure, it was found that the droplet auto-ignition delay time takes a peak at the ambient states near to the fuel critical point. This secular behavior is due to the influence of the phase equilibrium condition at droplet surface. Considering that current diesel engines operate at such condition, this knowledge addresses an interesting problem of finding an optimum spray condition for fast combustion. (2) Atomization is a keytechnology to spray combustion. However, the understanding of atomization mechanism involved in high-pressure sprays used in liquid rocket engines and diesel engines are very poor because optical observation is very difficult at high pressures. The current concept is based on the knowledge obtained from the experiments of water jet atomization at standard pressure. We examined the instability of jets with near-critical mixing surface and found a new instability mode with growth rate proportional to jet speed, which can make the liquid jetbroken into droplets with short spacing with the aids of hydrodynamic action. This finding theoretically bases the formation of dense sprays constituting of fine droplets at high pressures, if we regard a low-speed liquid jet as one of the liquid ligaments formed in the turbulent atomization process of an injected liquid. Furthermore, we studies (3) the mechanism of rapid flame propagation through combustible vortices formed in the process of turbulent mixing and (4) the modes of flame spreading between droplets for a various kind of sprays.

对液体燃料喷射到热力学状态超过燃料临界点的空气中时形成的喷雾燃烧的特征过程进行了分析。发现了以下内容。 (1)尽管对流认为液滴自燃延迟时间随着压力的增加而单调缩短，但发现液滴自燃延迟时间在燃料临界点附近的环境状态下出现峰值。这种长期行为是由于液滴表面相平衡条件的影响。考虑到当前的柴油发动机在这种条件下运行，这一知识解决了一个有趣的问题，即寻找快速燃烧的最佳喷雾条件。 (2)雾化是喷雾燃烧的关键技术。然而，由于光学观察在高压下非常困难，对液体火箭发动机和柴油发动机中使用的高压喷雾的雾化机制的了解非常少。当前的概念基于从标准压力下水射流雾化实验获得的知识。我们研究了近临界混合表面射流的不稳定性，发现了一种新的不稳定模式，其增长率与射流速度成正比，可以使液体借助流体动力作用射流破碎成短间距的液滴。如果我们将低速液体射流视为喷射液体的湍流雾化过程中形成的液体韧带之一，则这一发现在理论上基于在高压下形成由细小液滴组成的致密喷雾。此外，我们研究了（3）通过湍流混合过程中形成的可燃涡流快速火焰传播的机制，以及（4）各种喷雾的液滴之间的火焰传播模式。