북핵 이후 북한과 중국간의 경제협력 전망

金哲(Jin Zhe),禹穎子(Yu Yingzi) 경기연구원 2006 경기논단 Vol.8 No.4

The nuclear explosion experiment in DPRK has made the country’s crisis more serious. Two aspects must be clarified in analyzing the nuclear issue in DPRK. First, developing nuclear weapon is to meet the requirement of protecting DPRK’s own survival due to the lack of national safty security, and the low economic development level; Second, developing nuclear weapon in DPRK has destroyed the safty situation in North-east Asian area, and violated the common understanding of most other countries. Therefore, the cut-in point to resovle the nuclear issue in DPRK should be put on settling the issues that are deeply concerned by the country. Trade between China and DPRK started from 1950’s. The development of the two countries’bilateral trade relationship is not only due to their economic complementarity, more importantly, is the strategic requirement of the two countries. The nuclear explosion experiment will surely affect the trade relation between China and DPRK, but it will not influence their strategic economic cooperation in the long run. China will implement the 1718 resolution by the UN and carry out the normal business cooperation with DPRK. The economic cooperation between China and DPRK will develop in a healthy and sustainable state in the future. The development of economic cooperation between China and DPRK is not only beneficial to DPRK’s economic development, so as to help the country break away from its economic difficulty in a short-term, but also beneficial to strengthen the country’s self-confidence, so as to help the country open itself and carry out reform, and will finally be propitious to the peaceful settlement of the nuclear-weapon issue in DPRK.

Thrust vector control of supersonic nozzle flow using a moving plate

Fanshi Kong,Yingzi Jin,Heuy Dong Kim 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

A numerical study on the asymmetric nozzle with a moving plate was conducted. The thrust vector control of the nozzle was investigated based on the transient phenomenon of a supersonic jet. The primary stream was exhausted from a convergent-divergent nozzle and deflected by the upper nozzle wall, which slid forward and backward according to certain motions. The transient flow behavior was numerically accessed by the unsteady Reynolds averaged Navier-Stokes equations coupled with a Reynolds stress turbulence model using a fully implicit finite volume scheme. Results of the primary numerical analysis were in good agreement with existing experimental data. The time-dependent system characteristics were specified in terms of vector angle, system thrust ratio and thrust loss.

Study on drug powder acceleration in a micro shock tube

Guang Zhang,Yingzi Jin,Toshiaki Setoguchi,Heuy Dong Kim 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

Recently, micro shock tubes have been widely used in the medical engineering. The needle-free drug delivery device which mainly consists of a micro shock tube and an expanded nozzle has been produced to inject drug powders into human and animal bodies without any sharp metal needles. The drug powders were delivered by obtaining high momentum, which can be done by accelerating drug powders in the micro shock tube and supersonic nozzle. The particle-gas flows are induced by the incident shock wave developing by rupturing the diaphragm in the micro shock tube and again accelerated in the supersonic nozzle. The momentum of injected drug particles should be strictly controlled otherwise patients will suffer from skin injury or hurt. Even though micro shock tubes have been investigated in the past several decades, the detailed studies on particle-gas flows in the micro shock tube were rare to date due to the micro size and difficult experimental operation on micro shock tubes. In this paper, the experimental and numerical studies were carried out on investigating particle-gas flows in a designed micro shock tube. Particle tracking velocimetry (PTV) was performed to calculated particle average velocity at the exit of the supersonic nozzle. The nozzle flows were analyzed by obtaining instantaneous particle fields. The particle number density ratio was also investigated in the test section. The numerical simulations were performed by calculating unsteady Naver-Stokes equations on compressible flows and using fully implicit finite volume schemes. Discrete phase model (DPM) was used for simulating particle-gas flows in the micro shock tube. Particle diameter and density were varied to investigate their effects on the particle-gas flows. Unsteady particle-gas flows and shock wave propagation were obtained in details in the micro shock tube for present experimental and numerical studies.

Hysteretic Behaviors in the Counter-flow Thrust Vector Control

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

Optimization study on the isolator length of dual-mode scramjet

Ruoyu Deng,Yingzi Jin,김희동 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

The dual-mode scramjet is a prime candidate for air-breathing propulsion engines given its broad speed range and high efficiency. The detailed structure of the pseudo-shock wave in the isolator is worth investigating. Therefore, the present study investigates the effect of isolator length on the pseudo-shock wave. We replicate the experimental work of the reference paper with a two-dimensional numerical model. Pressure distribution on the body surface is applied in the numerical validation. The numerical result is in good agreement with that of the existing experimental work. We simulate the thermal choking condition with a throttling device. As the throat area of throttling device decreases, the back pressure continues increasing and the pseudo-shock wave moves upstream. Avoiding unstart phenomenon is a key objective in the operation of dual-mode scramjet. Therefore, we investigate the critical condition shortly before unstart phenomenon occurs. The pseudo-shock wave structure is described by pressure distribution. Our main objective is to explore the effect of isolator length on the dual-mode scramjet. The optimal isolator length depends on the maximum back pressure and total pressure loss in the critical condition shortly before the unstart phenomenon occurs. The maximum back pressure in the critical condition is higher when the isolator length ranges from 8.7 to 20.7. The total pressure loss in the critical condition decreases at the beginning and then increases when the isolator length ranges from 8.7 to 20.7.

CFD Study on the Isolator Performance of a Dual-Mode Scramjet

Ruoyu Deng,Yingzi Jin,Heuy Dong Kim 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11

As one of the most promising propulsive systems in the future, the dual-mode scramjet has drawn the attention of many researchers. Detailed flow features concerned with the isolator play the important role in the dual-mode scramjet. The two-dimensional numerical model has been established to replicate the generic features of the dual-mode scramjet. Numerical results have been compared with the experimental results for validation. Overall pressure distribution shows quite good agreement with the experimental result. The constant-area variable-length isolator followed by a diffuser section has been researched in this study. The cases of isolator lengths from 8.7 to 20.7 show higher maximum back pressure than other cases. The option of optimal isolator length not only depends on maximum back pressure but also on total pressure loss in the isolator. In conclusion, the optimal isolator length (L/Hth) is 12.7 in this study.

Study on the Fluidic Thrust Vector Control Using Co-Flow Concept

Kexin Wu,Yingzi Jin,Heuy Dong Kim 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5

In the present, various methods have been employed to obtain the lesser thrust loss. Numerical simulations have been carried out for optimizing the thrust vector control system. Thrust vector control based on coflowing shear layer is an effective method to control the primary jet direction in the absence of moving parts. Thrust vector in symmetric nozzles is acquired by secondary flow injections that result to boundary layer separation. The pressure in secondary flow inlet was varied to check the deflection angle of jet flow.

Numerical Study on Propagation of Shock Wave in a Micro Shock Tube

Guang Zhang,Yingzi Jin,Toshiaki Setoguchi,Heuy Dong Kim 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5-2

Two-Phase Choked Flows of Gas and Particle in a Convergent-Divergent Nozzle

Guang Zhang,Yingzi Jin,Heuy Dong Kim 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.12

Particle-gas two-phase flows show significantly different behaviors compared to single gas flow through convergent-divergent nozzles. Non-equilibrium effects, thermal and velocity lags lead to the inefficiency of nozzle performance. In the present studies, theoretical analysis and numerical simulations were carried out to study particle-gas flows through a C-D nozzle. Homogeneous equilibrium model that no lag in velocity and temperature happen between particles and gas phase was considered to derive choked mass flow rate and sound speed of multiphase flows. Two-phase flows are regarded as isentropic flows that isentropic relations can be used for homogeneous equilibrium model. Discrete phase model (DPM) where interaction with continuous phase and two-way turbulence coupling model were considered was used to simulate particle-gas flows. Particle mass loading (PML) was varied to investigate its effect on choking phenomena for particle-gas flows. Particle volume fraction, specific heat ratio, velocity slip ratio and sound speed of mixture flows were theoretically calculated by homogeneous equilibrium model and compared with numerical results.

Study on the Gas-Particle Two-Phase Flows in a Shock Tube

Guang Zhang,Yingzi Jin,Toshiaki Setoguchi,Heuy Dong Kim 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11