Pyrolysis and Coke Deposition of JP-10 with Decalin in Regenerative Cooling Channels

Abstract

The application of JP-10 (exo-tetrahydrodicyclopentadiene) in regenerative cooling channels is restrained by the severe coke deposition during its supercritical pyrolysis, while using hydrogen donors is one of the coke deposition suppression methods. To get new insights into the possible coke inhibition effect of the hydrogen donor under supercritical conditions, the pyrolysis and coke deposition of JP-10 in the presence of decalin at different concentrations (10−30 wt %) were experimentally examined in an electrically heated tube reactor at 4.0 MPa and 550−730 °C. The addition of decalin promotes the pyrolysis of JP-10, and the heat sink is maximumly improved from 2.87 to 3.21 MJ/kg (11.6%) at 730 °C, attributed to the higher conversion and mole yield of light alkenes. Meanwhile, the coke on the surface and in the bulk flow was maximumly reduced 43.0 and 31.8% with the addition of decalin, respectively. The coke deposition suppression is in agreement with the increased selectivity of stable precursors and the reduced content of polycyclic aromatic hydrocarbons (PAHs). On the basis of product distributions, decalin provides more free radicals to enhance the bimolecular reaction, then promotes the conversion of JP-10, and also provides active hydrogen radicals to restrain the formation of PAHs in the bulk flow and the radical growth of surface coke.

Application of Carbon Fiber‐Reinforced Ceramic Composites in Active Thermal Protection of Advanced Propulsion Systems: A Review

“…Both thermal oxidation coking and thermal pyrolytic coking are non‐catalytic coking reactions, which are the results of the polymeric dehydrogenation of free radicals and the coke is generally a granular material with a particle size of 1 to 2 μm. The morphology of these two kinds of surface coke is shown in Figure 15 and Figure 16 [31–32] . Compared to the pyrolytic reactions, the thermal oxidative coking process is much slower.…”

“…Thus, this problem has attracted much more research attention as the working conditions of thermal protection systems become harsher and harsher. Various methods, such as mental surface coating and hydrogen donor addition, etc., have been proposed and investigated to reduce or eliminate surface deposition [31,93] …”

“…The morphology of these two kinds of surface coke is shown in Figure 15 and Figure 16. [31][32] Compared to the pyrolytic reactions, the thermal oxidative coking process is much slower. But the coke deposition cannot be ignored when the heat time is long enough, especially in the reusable flight vehicles where the fuel oxidative coking could easily occur in the cooling channels due to its low activation temperature.…”

“…Various methods, such as mental surface coating and hydrogen donor addition, etc., have been proposed and investigated to reduce or eliminate surface deposition. [31,93] For the thermal oxidation coking phenomenon, Katta et al [94] proposed a 9-step chemical mechanism, which was later extended by Zabarnick and Ervin et al [95] - [96] , who established a 17-step pseudo-detailed mechanism and incorporated it into CFD. The thermal oxidation process of the fuel Jet-A is numerically simulated.…”

“…[11][12][13][14][15][16][17][18][19][20][21][22][23] However, increasing the proportion of carbon-reinforced composites with lower density, higher specific strength and higher temperature resistance in active thermal protection structures has become the trend. The complex physicochemical processes, such as the heat transfer deterioration and enhancement, [24][25][26] heat transfer instability, [27][28] flow maldistribution, [29][30] thermal oxidative coking [31][32] and, pyrolytic coking problems, [33][34][35][36] etc., are still not clear in the composite regenerative cooling channel. With the development of computational mechanics and high-performance computing cluster (HPCC), the numerical methods become more and more meaningful, which have been adopted to evaluate the mechanical properties, thermal properties, and manufacturing process of composites.…”