超临界环境下煤油替代物液滴燃烧特性数值研究

Numerical Investigation on Combustion Characteristics of Kerosene Surrogate Droplet in Supercritical Environment

关键词:  煤油替代物  液滴  超临界环境  燃烧特性  数值仿真

Key words:  Kerosene surrogate  Droplet  Supercritical environment  Combustion characteristic  Numerical simulation

摘要:

为研究液氧/煤油火箭发动机燃烧室内经喷注形成的煤油液滴的燃烧过程，基于实际气体状态方程、高压热物性修正、高压气液平衡和详细化学反应动力学，建立一维的全瞬态液滴燃烧模型，对超临界环境下两组分煤油替代物液滴的燃烧特性及液滴初始直径的影响进行仿真研究。结果表明，在超临界环境下，相比于煤油液滴纯蒸发过程，煤油液滴燃烧过程的迁移时刻大大提前；煤油液滴着火之后很快进入超临界燃烧阶段，此时液滴燃烧过程可以看成中心附近的燃料高浓度区与外侧氧气高浓度区之间的扩散燃烧过程；煤油液滴的火焰半径先增大，达到最大值之后开始减小，并减小为零，火焰温度在着火之后快速上升至最大值，并基本保持不变，在火焰半径减小为零之后开始降低；随着液滴初始直径的增大，火焰特性以及液滴中心参数变化曲线趋势不变、整体延迟，着火时间、迁移时间和液滴寿命增大。

Abstract:

To study the combustion process of kerosene droplet which was injected into the combustion chamber of LOX/kerosene rocket engine, based on the equation of state for actual gases, the correction of thermal physical properties under high pressure, vapor-liquid equilibrium under high pressure and detailed chemical-kinetic mechanisms, a one-dimensional transient droplet combustion model was established. The model was used to simulate the combustion characteristics and the influence of the initial droplet diameter of the bicomponent kerosene surrogate droplet in supercritical environment. The results show that, in supercritical environment, the migration time of combustion for kerosene droplet is much earlier than that of pure evaporation. The kerosene droplet enters the supercritical combustion stage soon after ignition and the droplet combustion process can be regarded as the diffusion combustion process between the high concentration of fuel near the center and the high concentration of oxygen outside. The flame radius of kerosene droplet first increases, and then decreases to zero after reaching the maximum. The flame temperature rises rapidly to the maximum after ignition, then almost keeps steady, and finally reduced after the flame radius decreases to zero. With the increase of initial droplet diameter, the variation tendency of flame characteristic and droplet center parameter is almost unchanged, only overall delay. The ignition time, migration time and droplet life increase as the initial diameter of the droplet increases.