In-situ cooling capacity of a hydrocarbon fuel under supercritical conditions: Heat sink, coke deposition, and impact of initiator

Abstract

The work investigates the suitability of a multi-component hydrocarbon fuel, namely HCF-1, as a potential fuel-cum-coolant for space vehicles under supercritical environments. The effects of reactor temperature, space-time, and initiator loading on fuel conversion, coke deposition, heat sink capacity, and gas selectivity are examined. The obtained value of fuel conversion, coke deposition rate, and chemical heat sink at 680 °C and 55 bar pressure are 10.3 wt.%, 7 mg/min, and 805 kJ/kg, respectively. The increase of fuel space-time from 2.8 s to 8.5 s increased the endothermicity by about 1.8-times. A decreasing trend in the olefin-to-alkane ratio with temperature and space-time is observed. The microscopic analysis confirmed the presence of both spherical-shaped (amorphous) and ribbon-like (filamentous) structures in the coke deposits. The estimated value of the apparent activation energy of the HCF-1 cracking reaction is 125 kJ/mole. Tributylamine (TBA) is recognized as a potential initiator to improve the cracking characteristics of the HCF-1. The fuel conversion and endothermicity increased by 58% and 18%, respectively, in the presence of 10,000 ppm of TBA at 650 °C. From the investigation, it can be said that the HCF-1 has a good potential to act as an endothermic fuel.