• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.113-126
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• 2021

In order to develop active cooling systems for a hypersonic cruise vehicle, a series of studies need to be preceded on regenerative cooling technologies by using endothermic reaction of liquid hydrocarbon aviation fuels. Among them, it is essential to scrutinize fluid flow/heat transfer/endothermic pyrolysis characteristics of supercritical hydrocarbons in a micro-channel, as well as to acquire thermophysical properties of hydrocarbon fuels in a wide range of temperature and pressure conditions. This study, therefore, reviewed those technologies and analyzed major findings in related research areas which have been carried out worldwide for the development of efficient operational regenerative cooling systems of a hypersonic flight vehicle.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.26-33
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• 2016

In order to analyze supercritical transition of liquid hydrocarbon fuel which used propulsion engine, visualization of phase changing using Methylcyclohexane (MCH) was performed. Also, measurements of temperature and pressure were conducted to obtain saturation lines of MCH and Decane. delayed increase of the pressure existed near the critical point due to dramatical increase of specific heats and the critical opalescence was only observed from the end point of delaying to the critical point. Beyond the critical point, the boundary between phases disappeared and the strong density gradient was observed. As the comparison between experimental and numerical saturation lines, the numerical estimation for mixture had relatively little difference while the results of pure components had almost coincidence.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.711-716
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• 2020

Injection visualization of heated mixed simulant droplets based on hydrocarbon fuel was performed under supercritical state environment. Mixed simulant consisted of Decane and Methylcyclohexane with different critical pressure and critical temperature. Flows injected into the supercritical state environment created droplet by Rayleigh breakup mechanism, and the Oh number and Re number were determined to confirm the breakup area. The temperature of the mixed simulant varied from Tr=0.49 to Tr=1.34. The flow rate was maintained at 0.7 to 0.8 g/s. Droplet became shorter in breakup length as heated and into a lumped form. Second droplet was formed and when Tr=1.34, the phase was not visible in the supercritical state with local unsteady flow.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.32-39
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• 2018

Supercritical injection behavior of liquid hydrocarbon compounds, which are used as main components of propellant fuel, was analyzed. Decane and Methylcyclohexane (MCH) with different critical points were selected as experimental fluid and Shadowgraphy technique was used. Decane and MCH behave differently in the initial state under the subcritical condition. However, near the critical point, the enthalpy of evaporation became close to 0, so that phase change into supercritical fluid occurred, not vaporization process, and no breakup of both fluids occurred.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.281-286
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• 2009

Bitumen extraction and sulfur removal from Athabasca oil sand were conducted using water in sub- and supercritical condition. Bitumen yield in micro reactor was investigated in the pressure range of 15~30 MPa, the temperature of 360 and $380^{\circ}C$ and water density $0.074{\sim}0.61g/cm^3$ for 0~120 min. Bitumen yield increased with reaction pressure irrespective of temperature and dramatically increased in especially supercritical region due to hydrogen formed from water gas shift reaction. Total amount of gas product decreased with reaction pressure but the portion of sulfur and hydrogen increased a little with increasing pressure to 25 and 30 MPa. It is seen that supercritical condition was favourable to the hydrogen formation and sulfur removal. Bitumen yield and sulfur removal from original oil sand reached a maximum 22% and 40% respectively in supercritical condition(the reaction time of 60 min at $380^{\circ}C$ and 25 or 30 MPa).

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.53-58
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• 2021

Based on surrogate model, a hydrocarbon mixture was analyzed by visualizing the impinging break up mechanism in subcritical and supercritical conditions. Decane and methylcyclohexane with different critical pressures and temperatures were selected as experimental fluids. The impinging injector was installed inside the chamber, and the spray was visualized through a speed camera in subcritical and supercritical conditions. The injection condition of the mixture and chamber was kept constant at Pr(P/P_c) = 1, and Tr(T/T_c) was increased from 0.48 to 1.02. As Tr increased, the spray angle increased, and the sheet length decreased as the properties of the mixture reached each critical point. In addition, when the mixture approached the near critical point, it was shown that the change in density gradient was largely observed out of the impinging break up mechanism.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.24-34
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• 2022

In order to predict the cooling performance of a regenerative cooling channel using hydrocarbon fuel operating in the supercritical region, it is essential to predict the thermodynamic properties. In this study, a comparative analysis was performed on two-parameter equations of state (SRK(Soave-Redlich-Kwong), PR(Peng-Robinson) equations of state) and three-parameter equations of state (RK-PR equations of state) to appropriately predict density and specific heat according to the critical compressibility factor of polymer hydrocarbons. Representatively, n-dodecane fuel with low critical compressibility factor and JP-10 fuel with high critical compressibility factor were selected, and an appropriate equation of state was presented when predicting the thermodynamic properties of the two fuels. Finally, the prediction results of density and specific heat were compared and verified with NIST REFPROP data.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.21-29
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• 2013

Turbulent flow and thermal fields of gaseous hydrogen/liquid oxygen flames at supercritical pressure are investigated by turbulence models. The modified Soave-Redlich-Kwong (SRK) EOS is implemented into the flamelet model to realize real-fluid combustions. For supercritical fluid flows, the modified pressure-velocity-density coupling are introduced. Based on the algorithm, the relative performance of six convection schemes and the predictions of four turbulence models are compared. The selected turbulence models are needed to be modified to consider various characteristics of real-fluid combustions.

• Journal of ILASS-Korea
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• v.15 no.4
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• pp.182-188
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• 2010

Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.4
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• pp.297-302
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• 2019

In this paper, the power generation efficiency increase has been studied for a Rankine cycle using both supercritical carbon dioxide as a working fluid and LNG as a coolant with PRO/II with PROVISION release 10.0 from Aveva company. Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle using LNG cold heat. Power generation efficiency was increased from 24.82% to 57.76% when using LNG as a coolant for supercritical carbon dioxide power generation cycle.