Study on the Fluidic Thrust Vector Control Based on Dual-Throat Concept

Kexin Wu,Heuy Dong Kim(김희동) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5

Numerical simulations are carried out on a supersonic nozzle to study the possibility of using dual-throat technique in fluidic thrust vector control. In the present work, the high efficiency and system resultant thrust ratio of the asymmetric dual-throat nozzle is illustrated. For the validation of methodology, CFD data are compared with experiment which is referred from the NASA Langley Research Center. 2D computational results are based on well-assessed SST k-ω turbulence model that it is recognized as the best in the compressible fluid dynamics. Second order accuracy is selected to reveal the details of the flow field as much as possible. The deflection angle, system resultant thrust ratio and thrust efficiency are investigated in a wide range of nozzle pressure ratios (NPRs) and injection pressure ratios (IPRs). Over-expanded and under-expanded flow conditions should be considered for corresponding to the different flight situations. Hence, it is decided to illustrate the performance variation with the changing of NPR values when the IPR is fixed at 7.6. The results report that deflection angle is decreasing with the increasing of NPR values. Meanwhile, the system resultant thrust ratio is found to be increased with the increasing of NPR as well as the thrust efficiency. As the NPR is set to 4, the deflection angle increases rapidly when IPR is less than 7. Then it follows by a smooth and slow increasing with the increase of IPRs. The system resultant thrust ratio is remained decreasing trend with the increasing of IPR value. The highest thrust efficiency is obtained at IPR=3.

Hysteretic Behaviors in the Counter-flow Thrust Vector Control

Kexin Wu,Yingzi Jin,Heuy Dong Kim 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.11

Study on Fluidic Thrust Vector Control Based on Dual-Throat Concept

Kexin Wu,Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회지 Vol.23 No.1

Performance Assessment of the Dual-Throat Nozzle Thrust Vector Control in a 3D Rectangular Nozzle

Kexin Wu,Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.11

Recently, fluidic thrust vectoring control is popular for a micro space launcher propulsion system due to its several advantages such as better control effectiveness, few or no moving mechanical equipment, and fast dynamic responsiveness. The dual-throat nozzle is an especially effective method in the fluidic thrust vectoring control field, utilizing another convergent section to connect with the divergent portion of the conventional convergent-divergent nozzle. By injecting secondary flow asymmetrically at the upstream nozzle throat, a new aerodynamic minimum area appears at the downstream of the geometric throat minimum area and the sonic-plane skews, therefore vectoring the primary flow. In the current work, numerical analysis is conducted to investigate the effects of the injection angle on dual-throat nozzle vectoring performance in a three-dimensional supersonic rectangular nozzle. To establish the reliability and accuracy of the current research methodology and turbulence model, the numerical results were validated against experimental results from the open literature. Numerical results calculated with the shear stress transport k-ω turbulence model shows an excellent agreement with experimentally measured static pressure along the upper dual-throat nozzle surface in the symmetry plane. Five injection angles are discussed and critical performance variations are quantitatively and qualitatively analyzed, including the pitching angle, injected mass flow ratio, system resultant thrust ratio, resultant pitching thrust efficiency, Mach number contour and streamline in the symmetry plane, and Mach number contours at different slices. Some useful conclusions are offered for fighter jet designers.

Computational study on the detachment and attachment phenomena of shock waves

Kexin Wu,Heuy Dong Kim 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

The detachment of attached shock waves and the attachment of detached shock waves frequently occur for various supersonic air vehicles. The transitional boundary plays a crucial role in clarifying the detachment and attachment processes of shock waves, which are always accompanied by remarkable aerodynamic characteristic differentials. In this work, a computational study is performed to investigate the detachment and attachment conditions of shock waves for profound understanding of the shock wave dynamics. The result of computational fluid dynamics is validated against existing experimental data in the open literature. An excellent match is obtained using the shear stress transport k-omega turbulence model. From the theoretical analysis, attached shock waves can transform into detached shock waves abruptly and vice versa. Realistic transitional regions with a certain range are numerically established. The differences in the detachment and attachment phenomena of shock waves are produced as a hysteresis process.

Copper Phthalocyanine Functionalized Polystyrene Superfine Fibers for the Photodegradation of Methyl Orange

Kexin Peng,Jiankui Guo,Haifeng Chen,Mali Xie,Xi Zhang,Xudong Huang,Guiying Xing,Linjun Shao,Chenze Qi 한국섬유공학회 2023 Fibers and polymers Vol.24 No.11

In this paper, copper phthalocyanine and polystyrene composite superfine fibers were readily prepared by electrospinning technology. After treating these composite fibers with paraformaldehyde in concentrated H2SO4 solution, the copper phthalocyanine molecules were covalently bonded to the polystyrene molecules. Meanwhile, the polystyrene molecules in the fibers were cross-linked to endow these fibers with excellent solvent resistance. The photocatalytic performance of this novel fibrous catalyst was evaluated by photodegradation of methyl orange in the presence of H2O2. The effects of light source, H2O2 dosage, catalyst loading, and temperature on the fiber catalyzed photodegradation of methyl orange were carefully studied. The photodegradation percentage of methyl orange in aqueous solution was up to ~ 97% under optimized reaction conditions. At last, this fibrous catalyst was readily recovered by simple filtration and reused for three times with satisfied photodegradation activities. In all, we have developed a facile way to prepare copper phthalocyanine functionalized polystyrene superfine fibers with excellent photocatalytic performance.

Preparation and Investigation of Ulex Europaeus Agglutinin IConjugated Liposomes as Potential Oral Vaccine Carriers

KeXin Li,DaWei Chen,XiuLi Zhao,HaiYang Hu,ChunRong Yang,DaHai Pang 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.11

We prepared and optimized Ulex europaeus agglutinin I (UEAI)-modified Bovine serum albumin (BSA)-encapsulating liposomes (UEAI-LIP) as oral vaccine carriers and examined the feasibility of inducing systemic and mucosal immune responses by oral administration of UEAILIP. The prepared systems were characterized in vitro for their average size, zeta potential,encapsulation efficiency (EE%) and conjugation efficiency (CE%). In vitro release studies indicated that the presence of UEAI around the optimized liposomes was able to prevent a burst release of loaded BSA and provide sustained release of the encapsulated protein. In vivo immune-stimulating results in KM mice showed that BSA given intramuscularly generated systemic response only but both systemic and mucosal immune responses could be induced simultaneously in the groups in which BSA-loaded liposomes (LIP) and UEAI-LIP were administered intragastrically. Furthermore, the modification of UEAI on the surface of liposomes could further enhance the IgA and IgG levels obviously. In conclusion, this study demonstrated the high potential of lectin-modified liposomes containing the antigen as carriers for oral vaccine.

Assessment of the Counter-Flow Thrust Vector Control in a 3D Rectangular Nozzle

Kexin Wu,Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5

Recently, fluidic thrust vector control is gradually replacing mechanical thrust vector control to redirect numerous aerospace vehicles due to lots of benefits, such as better control effect, no moving mechanical equipment, and fast dynamic response. In present works, computational assessments of gas dynamic characteristics have been explored in a three-dimensional counter-flow thrust vector control system, which is based on a rectangular supersonic nozzle. The supersonic nozzle is created by Method of Characteristics and the design Mach number is specially set as 2.5. To confirm the reliability and accuracy of present methodology, numerical simulations are validated against experimental test referred to open literature. Static pressure along the upper suction collar is found to be fairly comparable with experimental data, which is calculated by utilizing standard k-ε turbulence model. Performance variations are illustrated by varying the gap height of secondary flow duct. Key parameters have been quantitatively illustrated, such as static pressure distributions along the upper suction collar, deflection angle, secondary mass flow ratio, and resultant thrust coefficient. In addition, streamlines in the symmetry plane, turbulent kinetic energy, and three-dimensional flow-field with iso-Mach number surface are qualitatively presented to reveal flow-field natures. Some constructive conclusions are provided for further studies in counter-flow thrust vector control field.

Performance Assessment of the Dual-Throat Nozzle Thrust Vector Control in a 3D Rectangular Nozzle

Kexin Wu,Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 한국추진공학회 2020 한국추진공학회지 Vol.24 No.4

Study on the Shock Vector Control Based on the Slot Injector

Kexin Wu,Heuy Dong Kim 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.12

Nowadays, the fluidic thrust vector control (FTVC) technique is becoming one of the key strategies to redirect various aerospace vehicles, such as supersonic aircraft, rockets, and guided missiles. It was evident that the shock vector control (SVC) is a very simple, low cost, low weight, and quick vector response technique to achieve the high thrust vector performance. In this paper, computational fluid dynamics (CFD) methods were performed in a three-dimensional (3D) rectangular supersonic nozzle with the slot injector. In order to validate the numerical methodology, CFD results were compared with experimental data referred to the NASA Langley Research Center. The pressure distributions along the upper and lower nozzle surfaces in the symmetry planes were excellently matched with the test data. Computational results were based on well-assessed SST k-ω turbulence model. Second order accuracy was selected to reveal more details of the SVC flow-field as much as possible. The effect of the momentum flux ratio (J) was investigated emphatically. Performance variations for varying the momentum flux ratio were illustrated and some constructive conclusions were gained to provide the reference for the further investigations in FTVC field.