• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.63-71
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• 2007

The conversion efficiency, durability and pressure drop of the automotive exhaust catalysts are dependent on the flow distribution within the substrate. Conventional porous medium approaches assuming monolith resistance based on the one-dimensional laminar flow for simulating the flow through the automotive exhaust catalysts over-predict the flow uniformity in the monolith. In this study, additional pressure loss is also considered by accounting for entrance effects due to the oblique flow incident on the front face of monolith as a consequence of flow separation and recirculation within the diffuser. The incorporation of an additional pressure loss improves the predictions for the maximum flow velocity within the substrate. An numerical study has also been conducted for the three-dimensional unsteady incompressible non-reacting flow inside various dual-monolith catalytic converters for the rapid acceleration/deceleration driving.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.196-200
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• 2005

A theoretical model for the calculation of chemical equilibrium composition of propellant combustion product is briefly presented for the performance analysis of monopropellant hydrazine rocket engine. Analysis result is compared to that of test and evaluation of 1-lbf class thruster and is scrutinized primarily from the view point of ammonia dissociation fraction. Chemical equilibrium composition and average molecular weight is additionally depicted according to the variation of propellant inlet pressures and the varying nozzle area ratio. The theoretical analysis is tried as a way of derivation of design parameters for mid- and large-thrust class of monopropellant rocket engines.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.73-80
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• 2002

운영 자료의 조사$\cdot$분석을 위해 수도권 광역상수도의 취수장, 가압장 및 정수장들을 발문하여 각 펌프장에서 관리하고 있는 운전일보, 기기이력카드 등과 한국수자원공사에서 발간하는 월보 및 년보와 각 단계별 실시설계 보고서 및 준공도소를 수집하여 통계 처리한 결과를 요약하여 보면 다음과 같다. 각 단계별 수도권 광역상수도의 취수량 및 송수량은 운영을 시작한 초기부터 1990년까지 증가하다가 점점 수량이 감소하는 추세이다. 팔당 1 취수펌프장은 계획 취수량의 $95.5\%$, 2 취수펌프장은 $89.8\%$를 공급한 후 계속 감소되었고 설계 시 $100\%$의 용수량을 만족시키지 못하고 있다. 이러한 현상은 최근 IMF로 인하여 건설경기 둔화와 용수 수요량이 감소하였을뿐만 아니라 지방자치단체별로 취수펌프장을 독자적으로 건설하여 수요량 감소가 심화되었기 때문인 것으로 판단된다. 각 단계별 광역상수도 중 펌프의 운전토출압력과 운전흡입압력으로 부터 전양정을 계산하여 보면 설계된정격양정보다 낮은 수치인 저양정$\cdot$대유량으로 운전되고 있음을 알 수 있다. 이러한 운전은 캐비테이션을 발생시키고 이로 인하여 임펠러에 침식이나 균열이 발생하여 10년에 한번씩은 임페러를 교체한 것으로 나타났다. 그리고 펌프의 교체 주기는 $15\~20$년인 것으로 조사되었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.399-404
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• 2010

Test results including the variation of propellant-inlet pressure, pulsed thrust, and environment vacuum with the accompanying thermal responses are presented for the pulse-mode operation of a set of monopropellant hydrazine thrusters producing $0.95lb_f$ of nominal steady-state thrust at an inlet pressure of 350 psia. The test data are reduced into the impulse bit, specific impulse, and force centroid that are the factors typically characterizing pulse-mode performance of small rocket engines. With a scrutiny to the performance parameters, their comparison to the reference criteria of 1 lbf standard monopropellant rocket engine are successfully made.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.84-90
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• 2004

A performance evaluation is made in terms of thrust, impulse bit. and specific impulses for a set of mono-propellant hydrazine thrusters producing 0.95 lbf of nominal thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test configuration and procedures. a typical data obtained from steady-state firing mode is given directly showing the variational behavior of propellant supply pressure, mass flow rate, vacuum condition, and thrust. The performance features are successfully compared to the reference criteria of 1-lbf standard mono-propellant rocket engine. Additionally. a statistical inter-thruster treatment is concisely depicted for the justification of selected thrusters as a grouped member of flight model for spacecraft propulsion system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1149-1155
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• 2001

The experimental investigation on energy separation in a vortex tube has been carried out to sow the effect of inlet and outlet pressures with various working fluids(air,$O_2,\;and\; CO_2$). Those outlet pressure means cold outlet and hot outlet pressure which were set equally. The results showed that the total enthalpy variation became a maximum when the mass flow rate at the cold outlet was a half of the total mass flow rate in the vortex tube (y=0.5). The total enthalpy variation was quite affected by the pressure difference between the inlet and outlet of vortex tube when the ratio of the inlet pressure to the cold outlet pressure remained constant. Although specific enthalpy differences between the inlet and the outlet (both cold and hot outlet) did not noticeably vary with the pressure difference, the specific enthalpy difference between the inlet and cold outlet was dominantly affected by physical properties of working gases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.591-595
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• 2017

Numerical simulations were carried out to analyze thermo-fluid dynamic and missile-motion performance by using two-phase flow model and dynamic grid system. To analyze the interaction among the hot gas, coolant, and mixture flow, Realizable $k-{\varepsilon}$ turbulence and VOF(Volume Of Fluid) model were chosen and a parametric study was performed with the change of coolant flow rate. As a result of the analysis, pressure of the canister showed a large difference depending on the presence or absence of the coolant, and also showed a dependancy on the amount of coolant. Velocity and acceleration were dependent on the canister pressure.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.223-224
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• 2009

본 연구에서는 $Cl_2$/Ar 기반의 플라즈마 식각에 $N_2$가스를 첨가하여 ZnO 박막을 식각 하였을 때 관찰된 ZnO 박막의 식각 특성에 관하여 연구 하였다. ZnO 박막 식각 실험은 RF 800 W, bias power 400 W, 공정 압력 15 mTorr를 기준으로 하였으며 가스 혼합 비율로는 최적의 식각률을 보여주는 $Cl_2$/Ar=8:2 비율에서 실행하였다. 연구의 목적인 첨가 가스 $N_2$를 $Cl_2$ (80%)/Ar (20)%에 5 sccm 씩 첨가하여 20 sccm 까지 증가 시켜 실험 하였다. $N_2$ 가스가 15 sccm 첨가되었을 때 식각률 95.9 nm/min로 기존 $Cl_2$/Ar 기반의 플라즈마 식각보다 높은 식각률을 보여 주었으며 $N_2$ 가스 흐름 조절 외에도 공정 압력, RF power, bias power를 변경하며 실험하였다. 식각된 ZnO 박막의 표면은 최대 식각률을 보이는 공정 조건을 찾기 위해 surface profiler ($\alpha$-step)을 이용하여 식각률을 측정하였으며 ZnO 박막 표면의 화학적인 변화를 조사하기 위해 x-ray photoelectron spectroscopy (XPS)를 사용하였다. XPS 분석 결과 Zn $2p_{3/2}$ peak 가낮은 binding energy 쪽으로 이동한 것을 관찰 할 수 있었다. 또한 O 1s 의 스펙트럼을 분석한 결과 N-O bond와 O-H bond가 존재함이 밝혀졌다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.143-148
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• 2012

This study is an investigation on macroscopic spray behavior of nonimpinging-type injector equipped on the hydrazine thruster under development. An electron microscope is employed for the acceptance examination of injector orifice. Initial performance characteristics and spray behavior of injector are observed through the instantaneous spray images which are captured by high speed camera and Schlieren method with varying injection pressures. The injector performance is scrutinized by the velocity along with penetration length of spray and categorized by dimensionless parameters. It is confirmed that there exist varying characteristics related to the spray breakup caused by fabrication errors of injector-orifices. Unexpected spray behavior, which needs to be reexamined, is grasped at specific pressure level, as well.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.165-172
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• 2022

Pintle injector is the most suitable injector for thrust control because it can control the area of propellant injection. Accordingly, the combustion test of multiple hole pintle injector and continuous type pintle injector was carried out in this paper using liquid oxygen and gas methane. The combustion performance of the two pintles was verified with the characteristic speed efficiency, and the experimental results were compared according to the O/F and combustion chamber pressure and under similar conditions. The efficiency of the multi hole pintle was generally somewhat higher than continuous pintle when pintle opening distance(the area of dispensing oxidizer) was in a 100% thrust condition.