PIC-DSMC Simulation of a Hall Thruster Plume with Charge Exchange Effects Using pdFOAM
Sang Hun Kang
IF 2.2
Aerospace
To develop technologies for the stable operation of electric propulsion systems, the effects of charge exchange (CEX) on the exhaust plume of a Hall thruster were studied using the particle-in-cell direct simulation Monte Carlo (PIC-DSMC) method. For the numerical analysis, an OpenFOAM-based code, pdFOAM, with a simple electron fluid model was employed. In an example problem using the D55 Hall thruster exhaust plume, the results showed good agreement with experimental measurements of the plasma potential. In the results, CEX effects enhanced Xe+ particle scattering near the thruster exit. However, due to the increase in the plasma potential with CEX effects, fewer Xe2+ particles were near the thruster exit with CEX effects than without CEX effects.
Numerical Study on the Non-Oscillatory Unstarted Flow in a Scramjet Inlet-Isolator Model
Jaewon Lee, Sang Gon Lee, Sang Hun Kang, Hyuck-Joon Namkoung
IF 2.2
Aerospace
For successful scramjet engine operations, it is important to understand the mechanism of the inlet unstart phenomenon. Among various unstarted flow patterns in hypersonic inlets, the mechanism of low-amplitude oscillatory unstarted flow is still unclear. Therefore, in the present study, the flow characteristics of non-oscillatory unstarted flow in a scramjet inlet-isolator model are studied by using numerical analysis with the RANS-based OpenFOAM solver. In the numerical results, the amplitude of pressure oscillation and the average pressure near the model outlet are in good agreement with experimental results. In the detailed analysis of the results, it is found that the incoming flow within the boundary layers repeatedly changes direction due to the flow blockage at the end of the model. In these direction-changing processes, recirculation zones near the walls irregularly influence the choked flow zones at the rear part of the model. These irregular behaviors result in non-oscillatory unstarted flow. Additionally, the main differences between the high-amplitude oscillatory unstarted flow and non-oscillatory unstarted flow are addressed.
PIC-DSMC Simulation of a Hall Thruster Plume with Charge Exchange Effects Using pdFOAM
Sang Hun Kang
IF 2.2
Aerospace
To develop technologies for the stable operation of electric propulsion systems, the effects of charge exchange (CEX) on the exhaust plume of a Hall thruster were studied using the particle-in-cell direct simulation Monte Carlo (PIC-DSMC) method. For the numerical analysis, an OpenFOAM-based code, pdFOAM, with a simple electron fluid model was employed. In an example problem using the D55 Hall thruster exhaust plume, the results showed good agreement with experimental measurements of the plasma potential. In the results, CEX effects enhanced Xe+ particle scattering near the thruster exit. However, due to the increase in the plasma potential with CEX effects, fewer Xe2+ particles were near the thruster exit with CEX effects than without CEX effects.
Numerical Study on the Non-Oscillatory Unstarted Flow in a Scramjet Inlet-Isolator Model
Jaewon Lee, Sang Gon Lee, Sang Hun Kang, Hyuck-Joon Namkoung
IF 2.2
Aerospace
For successful scramjet engine operations, it is important to understand the mechanism of the inlet unstart phenomenon. Among various unstarted flow patterns in hypersonic inlets, the mechanism of low-amplitude oscillatory unstarted flow is still unclear. Therefore, in the present study, the flow characteristics of non-oscillatory unstarted flow in a scramjet inlet-isolator model are studied by using numerical analysis with the RANS-based OpenFOAM solver. In the numerical results, the amplitude of pressure oscillation and the average pressure near the model outlet are in good agreement with experimental results. In the detailed analysis of the results, it is found that the incoming flow within the boundary layers repeatedly changes direction due to the flow blockage at the end of the model. In these direction-changing processes, recirculation zones near the walls irregularly influence the choked flow zones at the rear part of the model. These irregular behaviors result in non-oscillatory unstarted flow. Additionally, the main differences between the high-amplitude oscillatory unstarted flow and non-oscillatory unstarted flow are addressed.
Trajectory Optimization and Performances of RBCC for Long-Range Return Missions of Reusable Vehicle
Dong Uk Kim, Sang Hun Kang
Journal of the Korean Society of Propulsion Engineers
This study analyzes the performance of a Rocket-Based Combined Cycle (RBCC) engine for a reentry vehicle's long-range return mission using trajectory optimization.Using OpenGoddard, maximum-range trajectories were derived and compared for an X-37B based vehicle equipped with either an RBCC engine or a conventional liquid rocket engine.The analysis revealed that the RBCC engine's performance varied significantly with maximum thrust.Under a low-thrust condition (1 kN), the flight range increased by only 1.13% compared to the rocket, whereas a high-thrust condition (29.4 kN) resulted in a significant 42.91% increase.This is because sufficient thrust enabled an optimal maneuver that first utilized the high-efficiency ramjet mode and subsequently climbed to a high-altitude, low-drag regime.Therefore, securing sufficient thrust is a key design condition for the effective application of an RBCC engine to the long-range missions of reentry vehicles. (RBCC) .OpenGoddard X-37B RBCC . , RBCC .(1 kN) 1.13% , (29.4kN) 42.
A Numerical Study on the Combustion Characteristics of RBCC Engines Based on Embedded Rocket Configurations
Seonghyeon Jeong, Sang Hun Kang
Journal of the Korean Society of Propulsion Engineers
The RBCC engine can be classified into three types(Axisymmetric, Wall-attached rocket, Strutjet) based on the internal embedded rocket configuration.In this study, five test conditions were established by varying the rocket chamber pressure and combustor length for each engine type, and the performance characteristics of each type were compared and analyzed through computational analysis.The results of the computational analysis showed that the Strutjet type exhibited the highest combustion efficiency.In contrast, for the other types, the combustion efficiency was low if sufficient length was not secured.It was confirmed that while a certain combustor length is necessary for high combustion efficiency, exceeding this length does not significantly impact the combustion efficiency. RBCC 3 (Axisymmetric, Wall-attached rocket, Strutjet) . , 5 , . , Strutjet , , .
Analysis on the Impact of Background Pressure on the Exhaust Plume of Electric Thruster
Woosin Park, Sang Hun Kang
Journal of the Korean Society of Propulsion Engineers
Hall thrusters, a type of electric propulsion, are increasingly being used as propulsion systems for spacecraft. When evaluating the performance of a Hall thruster through ground tests, it is essential to recognize the influence of the higher background pressure inside the vacuum chamber compared to space conditions and to correct the performance values to reflect those in actual space environments. In this study, the effects of background pressure levels ranging from 3 to 60 μTorr on the exhaust plume of a Hall thruster were analyzed using PIC-DSMC(Particle-in-Cell Direct Simulation Monte Carlo) method. It was observed that as the background pressure increased, collisions and charge exchanges between neutral atoms and ions in the thruster plume increased. With the increase in charge exchange, the scattering of Xe+ ions and the plasma potential also increased, leading to an increase in ion backflow. Therefore, correcting the results considering background pressure is essential for accurate performance prediction of electric thrusters.
Influence of social network on loneliness among the elderly living alone: Focusing on moderating effect of housing type
Sang Hun Kang, Seok-Joo Kim
The Korea Academy of Case Management
Focusing on the moderating effect of housing type, this study aimed to identify the influences of social network and housing type on loneliness among the elderly living alone. For the survey, this study recruited the elderly living alone (n=460) in Gyeongsangbuk-do providence, South Korea. Hierarchical multiple regression analyses found that the emotional and informational networks negatively influenced on the elderly’s loneliness regardless of housing type. As well, the analyses identified the moderating effect of housing type on the relationship between the social network and loneliness. Specifically, the instrumental network was strongly related to decreasing loneliness among non-homeowners; however, the social activity network was strongly associated with decreasing loneliness among homeowners. Following these findings, this study discussed the implications on social work practice for the elderly living alone.
