Abstract:

Monopropellant energy belongs to gas energy. Unlike conventional energy that relies on oxygen combustion to release energy, it generates high-temperature and high-pressure gas by catalytic decomposition of energetic liquid chemicals without air, which flows through the Laval nozzle to generate thrust or blow the turbine output shaft power. The characteristics are high reliability, fast response, low cost, and unrestricted flight altitude. It is often used to maintain the satellite orbit and provide the emergency power unit for aerospace equipment. With start-up of this power system, the liquid monopropellant enters the packed bed and contacts with the catalyst particles, and then immerses into the micro/nano pores of the catalyst carrier under the action of capillary force. The high-temperature and high-pressure small molecule gas phase is generated with being activated and decomposed by precious metal nanoparticles. With the influence of catalyst pore structure, size, and surface activity, when the gas production rate of catalytic decomposition inside the pore is greater than the outward movement speed of the fluid, the internal pressure in the pore will sharply increase, and even damage the carrier to deactivate. In this paper, the Poiseuille flow is used to describe the flow of gas-phase products in catalyst pores, the Newton’s second law is employed to analyze the movement of gas-liquid interface driven by capillary force, and the gas production rate is predicted through reactant diffusion reaction model. The phenomena of flow, catalytic reaction and gas-phase pressure formation process in the catalyst micro/nano pores is investigated during the initiation of hydrazine propellant catalytic decomposition reaction. The physical phenomenon of catalyst destruction and deactivation caused by the excessive pressure in the pores is analyzed during the initiation process, a theoretical basis for designing and optimizing the catalyst pore structures is provided for decomposing monopropellant.

Key words: Poiseuille flow, capillary, hydrazine decomposition, diffusion, reaction, catalyst pores, mass transfer

摘要：

单组元能源属于燃气能源，不同于依赖氧气燃烧释能的常规能源，它是无须空气条件下通过催化分解含能液体化学品生成高温高压气体，流经拉瓦尔喷管产生推力或吹动涡轮输出轴功率。特点是高可靠，快响应，低成本，飞行高度不受限，常被用于为航空航天装备提供轨道维持和应急保障的动力。该类能源动力系统启动时，液体推进剂进入到反应催化床内与催化剂接触，并在毛细管力作用下，浸入载体微-纳孔道内被贵金属纳米粒子活化，发生催化分解反应生成高温高压小分子气相。受催化剂孔道结构、尺寸及表面活性影响，孔道内催化分解产气速率大于流体向外运动速度时，内部气相压力会急剧升高，甚至破坏载体毛细孔道结构导致失活。本文采用Poiseuille流描述催化剂孔道内的气相产物流动、毛细管力驱动牛顿第二定律解析气-液界面移动、反应物扩散-反应模型预测产气速率，揭示肼推进剂催化分解反应启动时在催化剂微纳孔道内的流动，催化反应以及气相压力形成过程，解析了启动过程中孔道内压过大导致催化剂破坏失活的物理现象，为单组元推进剂分解用催化剂孔道结构设计开发提供理论基础。

关键词: Poiseuille流, 毛细管, 肼分解, 扩散, 反应, 催化剂孔道, 传质