Effect of the Wall Temperature on Shock Wave Detachment Criterion

Kexin Wu(우커신),Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

Fluidic Thrust Vector Control Using Shock Wave Concept

Kexin Wu,Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회지 Vol.23 No.4

Recently, fluidic thrust vector control has become a core technique to control multifarious air vehicles, such as supersonic aircraft and modern rockets. Fluidic thrust vector control using the shock vector concept has many advantages for achieving great vectoring performance, such as fast vectoring response, simple structure, and low weight. In this paper, computational fluid dynamics methods are used to study a three-dimensional rectangular supersonic nozzle with a slot injector. To evaluate the reliability and stability of computational methodology, the numerical results were validated with experimental data. The pressure distributions along the upper and lower nozzle walls in the symmetry plane showed an excellent match with the test results. Several numerical simulations were performed based on the shear stress transport(SST) k-ω turbulence model. The effect of the momentum flux ratio was investigated thoroughly, and the performance variations have been clearly illustrated.

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

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

Numerical simulations were carried out in a supersonic nozzle to investigate the possibility of using dual-throat nozzle concept in fluidic thrust vector control. Validation of the methodology showed an excellent agreement between the computational fluid dynamics results and the experimental data available, which were based on the well-assessed SST k-ω turbulence mode. The deflection angle, system resultant thrust ratio, and thrust efficiency were investigated in a wide range of nozzle pressure ratios and injection pressure ratios. The performance variations of the dual-throat nozzle thrust vector control system were clearly illustrated with this two-dimensional computational domain. Some constructive conclusions were obtained that may be used as a reference for further studies in the fluidic thrust vector control field.

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.

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.

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.

Assessment of the Counter-Flow Thrust Vector Control in a Three-Dimensional Rectangular Nozzle

Kexin Wu,Tae Ho Kim(김태호),James Jintu Kochupulickal,Heuy Dong Kim(김희동) 한국추진공학회 2020 한국추진공학회지 Vol.24 No.1

Computational assessment of gas-dynamic characteristics is explored for a three-dimensional counter-flow thrust vector control system in a rectangular supersonic nozzle. This convergent-divergent nozzle is designed by Method of Characteristics and its design Mach number is specially set as 2.5. Performance variations of the counter-flow vector system are illustrated by varying the gap height of the secondary flow duct. Key parameters are quantitatively analyzed, such as static pressure distribution along the centerline of the upper suction collar, deflection angle, secondary mass flow ratio, and resultant thrust coefficient. Additionally, the streamline on the symmetry plane, three-dimensional iso-Mach number surface contour, and three-dimensional turbulent kinetic energy contour are presented to reveal overall flow-field characteristics in detail.

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

The dual-throat nozzle is an extremely effective method in the thrust vectoring control field, utilizing another convergent section to connect with the divergent part of the conventional convergent-divergent nozzle. In the present research, the numerical simulation is conducted to investigate the effects of the injection angle on thrust vectoring performance in a 3D supersonic nozzle. Five injection angles are discussed and core performance variations are analyzed, including the deflection angle, injected mass flow ratio, system resultant thrust ratio, efficiency, Mach number contour and streamline on the symmetry plane, and Mach number contours at different slices. Meaningful conclusions are offered for fighter jet designers.