冷却通道预氧化处理抑制碳氢燃料热裂解结焦的研究

Inhibiting Pyrolytic Deposition of Hydrocarbon Fuels on the Cooling Channels Through Pre-Oxidized Treatment

关键词:  碳氢燃料  超临界  热裂解  表面处理  结焦 

Key words:  Hydrocarbon fuel  Supercritical  Thermal cracking  Surface treatment  Coke deposition

摘要:

主动冷却超燃冲压发动机用吸热碳氢燃料应用过程中不可避免产生裂解结焦,这是制约燃料热沉能力和过程可靠性的重要因素。冷却通道表面进行预处理,是减少裂解结焦的重要途径之一。系统研究了预氧化321不锈钢管(Φ3mm×0.5mm)的元素迁移和微观结构。利用超临界航空煤油RP-3的热裂解反应为探针,研究预氧化处理对结焦的影响。实验发现,高温氧化后(900℃),管表面形成一层致密的Cr₂O₃膜,能减少碳沉积,几乎不生成纤维碳；较低温(600~800℃)氧化时,虽然Cr 元素不断向金属表面迁移, Fe,Ni 元素向金属内部迁移,但同时产生了大量空缺位提供渗碳通道,最终导致结焦量高于空管。 

Abstract:

Pyrolytic deposit is inevitably formed during thermal cracking of the hydrocarbon fuel in active cooled scramjet engine. And it is a crucial issue for heat capacity and system reliability.Surface treatment is an efficient way to mitigate coke deposition in the regenerative cooling channel. Elements migration and micro-structures of pre-oxidized stainless steel 321tubes (Φ3mm× 0.5mm) are systemically studied at different temperature. Thermal cracking of Chinese RP-3jet fuel is used as model reaction to examine the anti-coking performances of pre-oxidized tubes. It is found that a stable Cr₂O_3layer which is capable of inhibitting coke formation (particularly, filamentous coke) forms on the tube pre-oxidized at high temperature (up to 900℃), but pre-oxidization at relatively lower temperature(600~800℃) makes Cr migrate to the metal surface and Fe, Ni to internal structure, meanwhile, provides lots of drawbacks and diffusion pathways on the tube surface which accelerates the formation of deposition. 