Thermal Cracking of Endothermic Hydrocarbon Fuel in Regenerative Cooling Channels with Different Geometric Structures

Abstract

The chemical heat sink of endothermic hydrocarbon fuels (EHFs) is generally dependent on its thermal cracking in the cooling channel, which is accompanied and limited by the formation of carbon deposit. In this work, HF-1 (a kerosene-based EHF) was electrically heated in the rectangular, square, and circular channels with the same cross-sectional area under 3.5 MPa to study the effect of cooling channel geometric structures on the thermal cracking and carbon deposition behaviors. It was found that under similar conditions (inlet flow rate of fuel, pressure, outlet temperature), conversions of HF-1 in both rectangular and square channels were slightly higher than that in the circular one with high selectivity to methane but lower selectivities to the primary cracking products (such as 1-hexene and 1-heptene, etc.). In addition, more carbon deposits were formed in the rectangular and square channels, especially around the corners of channels. Based on the CFD simulation, the possible reasons should be ascribed to the difference in the gradient uniformity near the wall of different channels. The higher temperature and lower velocity in the boundary layer of the quadratic channels might cause the thermal cracking to be slightly severer and the rapid secondary reactions to form carbon deposit.

Endothermic catalytic cracking of liquid hydrocarbons for thermal management of high-speed flight vehicles

“…Thermal cracking at low conversions (up to 20-25%) has shown to provide additional heat sink through endothermic reactions leading to smaller hydrocarbons. 23,24 However, the heat sink obtained from catalytic and thermal cracking do not follow the same behaviour. The heat sink of catalytic cracking is a direct function of the fuel conversion.…”

“…24 Moreover, higher pressures have also shown to be more benecial for bimolecular reactions to occur, leading to higher heat transfer deterioration through the recombination of small hydrocarbons through exothermic reactions. 23,24 Longer residence time of the hydrocarbons exposed to thermal cracking also lead to the formation of equilibrium products, i.e. methane and solid carbon deposits.…”

Heat Management in Supersonic/Hypersonic Vehicles Using Endothermic Fuel: Perspective and Challenges

“…The bulk fluid and wall temperatures decreased with the increase in fuel flow for a constant heat flux value. Li et al 80 have investigated the feasibility of power generation for hypersonic vehicles driven by hydrocarbon fuels. An analytical model was developed to predict the expansion characteristics of the cracked hydrocarbon.…”

Effects of geometric parameters of rectangular cooling channel on pyrolysis carbon deposition in fuel‐cooled plates

“…The maximum carbon deposition thickness is only 5.54 μm, which also indicates that the carbon deposition amount in this paper has not reached the magnitude that can affect heat transfer. [21,34] The decoupling algorithm is also further proven to be effective.…”

“…[19,20] However, some researchers have found that the 3D structure of the channel itself might also affect carbon deposition. [21] Therefore, it is a feasible method to avoid or at least mitigate the formation of carbon deposition at high temperature to the greatest possible extent by modifying the structural parameters in fuel-cooled plate design.…”