超临界压力下正癸烷在多孔介质中结焦实验研究 *

Experiment on Coke Deposition of Supercritical n-Decane in Porous Media

关键词:  结焦  正癸烷  超临界压力  多孔介质

Key words:  Coke deposition  n-decane  Supercritical pressure  Porous media

摘要:

发散冷却是高超声速飞行器热部件防护的关键技术之一。为了研究碳氢燃料结焦性对其作为冷却流体在发散冷却技术中安全性的影响，对超临界压力下正癸烷在烧结青铜球形颗粒多孔介质中的结焦特性进行实验研究，获得了正癸烷在压力3MPa，温度350～638℃和质量流量2～4kg/h下的焦碳表面沉积规律。研究表明:温度是正癸烷在多孔介质中结焦产物生成的主导因素，并发现正癸烷存在热氧化结焦与热裂解结焦两种结焦行为，导致其焦碳表面沉积速率呈现双峰结构。一定温度下，质量流量决定正癸烷在流道中驻留时间，热氧化结焦受驻留时间与溶解氧浓度两个因素制约，焦碳表面沉积速率随质量流量增加先增大后减小；热裂解结焦则只受到驻留时间的影响，焦碳表面沉积速率随质量流量增大而单调减小。

Abstract:

The transpiration-cooling technology is one of major thermal protection methods used on hypersonic vehicles. To ensure the safety of transpiration-cooling structures， the coke deposition rule of hydrocarbon fuels in porous media is a key problem that has to be considered. This work presented the experimental studies on coke deposition of n-decane in sintered brozen porous media at 3MPa supercritical pressure with the temperature ranged from 350℃ to 638℃， and the mass flow rate of 2～4kg/h. Results showed that the temperature was a dominant factor of coke generated from n-decane. Two types of coking behaviors including thermal-oxidative coking and pyrolysis coking were observed， which leading to the coke surface deposition rate with a double-peak curve. At a certain temperature， the mass flow rate determined the residence time of n-decane in porous channels. Thermal-oxidative coking was limited by the residence time and the dissolved oxygen concentration， so the coke surface deposition rate increased at first and then decreased with the mass flow rate increased. However， pyrolysis coking was only affected by the residence time， so the coke surface deposition rate decreased monotonously with the mass flow rate increased.