• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.161-170
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• 2013

The flow and combustion characteristics in a premixed swirl combustor with a double cone burner are numerically analyzed to adopt a swirler model. The internal recirculation zone formed at the burner exit can be realized by a swirler with inner and outer diameters of 56 and 152 mm, respectively, and accordingly, the flow rate and radial velocity were determined. To select the tangential velocity, swirl and recirculation angles are introduced. A tangential velocity of 40 m/s produces an internal recirculation zone similar to that in a combustor. At the liner exit, the errors in temperature and velocity are 2.8% and 0%, respectively, and they are negligibly small. However, NOx emissions are underestimated by 67% in the numerical results obtained using the swirler model. Although considerable quantitative errors are induced by the swirler model, it can be useful numerical model for the EV burner because it can approximately simulate the essential flow and combustion characteristics in a premixed swirl combustor with a double cone burner and it is expected to make combustion analysis efficient in a gas turbine combustor with complex geometries.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.338-345
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• 2011

The swirl flow applied for high efficiency and reduction of emission such as NOx, CO in a gas turbine engine makes recirculation zone by shear layer in the combustion chamber. This recirculation zone influences a decreasing flame temperature and flame length by burned gas recirculation. Also it is able to suppress from instability in lean-premixed flame. In this study, it was found that the swirl flow field was characterized as function of swirl number using PIV measurement in dump combustor. As increasing swirl number, a change of flow field was presented and recirculation zone was shifted in the nozzle exit direction. Also turbulent intensity and turbulent length scale in combustor were decreased in combustion. It has shown reduction of eddies scale with swirl number increasing.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.70-75
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• 2016

A swirler is a flame holding device generating recirculation regions in a gas turbine combustor, and the flow pattern due to a swirler has major effects on the flame distributions, combustion efficiency, and characteristics of exhaust gas. An experimental study for a counter-rotating swirler has been conducted to find out effects of the mass flow rate ratio of the inner/outer swirler flow area, the pressure difference between the swirler inlet and outlet, and the flare exit length ratio on the flow patterns in a model combustion chamber by using PIV(Particle Image Velocimetry) technique.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.29-36
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• 2002

Experiments have been performed to investigate the effect of secondary venturi tip angle on flow and spray characteristics in gas turbine combustor with a swirl cup assembly. Three variations of secondary venturi tip angle are made: converging, straight and diverging angles. It is found that the variation of venturi tip angle results in the significant changes of flow and spray characteristics in gas turbine combustors, such as the size and location of recirculation zones. drop size and mass distribution affecting combustion efficiency and NOx emissions. In diverge case, central toroidal recirculation zone(CTRZ) exists near the exit, which is known to be beneficial for flame stability. But in converge case, the finest SMD distribution and uniform mass distribution are found and CTRZ is longer than other cases. Consequently, high combustion efficiency and low pollutant emission are expected in converge case.

• Journal of Korean Society of Transportation
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• v.19 no.1
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• pp.149-157
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• 2001

내부순환로 교통관리시스템은 기존의 국내 교통 시스템들과는 달리 충분한 수집체계와 정보제공 체계를 갖추고 있으며, 전략의 구체화와 현실적 실현, 즉 전략의 시스템화를 위해 많은 노력을 기울였다. 그런 노력의 일환으로 이 시스템에서는 다양하고 복잡한 돌발상황을 단순화하고 일반화하기 위해 Uniform Event Reaction Formula라 하는 개념을 사용하였다. 이 개념은 어떤 돌발상황이 발생하면 이로 인해 영향을 받는 반응 영역과 영향을 받지 않는 비반응 영역으로 분리한 후, 반응 영역은 예측을 통한 제어 관리를 수행하고, 비반응 영역은 통상적인 제어 관리만을 수행함을 의미한다. 그러나, 돌발상황에 따른 반응 영역과 비반응 영역의 결정에 필요한 돌발상황 처리시간 예측과 대기행렬 예측 모형은 내부순환로의 도로 및 교통환경에 적합한지 검증되지 않아 많은 시행착오가 예상된다. 특히, 돌발상황의 처리시간 예측은 동질대응 구간 결정의 가장 중요한 요소로서, 현재는 처리시간에 상당한 여유를 두어 운영할 계획이지만 궁극적으로는 내부순환로에 적합한 처리시간 예측 모형의 개발이 필요할 것으로 판단된다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.85-93
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• 2017

This paper presents mechanical properties and carbonation behavior of the recycled aggregate concretes(RAC) in which natural aggregate was replaced by recycled coarse aggregate and fine aggregate by specified concrete strength levels(21, 35, 50MPa). A total of 18 RAC were produced and classified into six series, each of which included three mixes designed with three specified concrete strength levels of 21MPa, 35MPa and 50MPa and three recycled aggregate replacement ratios of 0, 50 and 100%. Physical and mechanical properties of RAC were tested for slump test, compressive strength, and carbonation depth. The test results indicated that the slump of RAC could be improved or same by recycled coarse aggregate replacement ratios, when compared with natural aggregate. But slump of RAC was decreased as the recycled fine aggregate replacement ratios increase. Also, the test results showed that the compressive strength was decreased as the recycled aggregate replacement ratios increased and it had a conspicuous tendency to decrease when the content of the recycled aggregate exceeded 50%. Furthermore, the result indicated that the measured carbonation depth increases by 40% with the increase of the recycled aggregate replacement. In the case of the concrete having low level compressive strength, the increase of carbonation depth tends to be higher when using the RCA. However, the trend of carbonation resistivity in high level compressive strength concrete is similar to that obtained in natural aggregate concrete. Therefore, an advance on the admixture application and mix ratio control are required to improve the carbonation resistivity when using the recycled aggregate in large scale.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.417-422
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• 2010

Low temperature diesel combustion was achieved via a combination of late injection timing ($8.5^{\circ}$ CA BTDC to $0.5^{\circ}$ CA BTDC) and heavy exhaust gas recirculation (37% to 48%) with ultra low sulfur Swedish diesel fuel in a 1.7L common rail direct injection diesel engine. When injection timing is retarded at a certain exhaust gas recirculation rate, the particulate matter and nitrogen oxides decease simultaneously, while the hydrocarbon and carbon monoxide increase. Hydrocarbon speciation by gas chromatography using a flame ionization detector reveals that the ratio of partially burned hydrocarbon, i.e., mainly alkenes increase as the injection timing is retarded and exhaust gas recirculation is increased. The two most abundant hydrocarbon species are ethene which is a representative species of partially burned hydrocarbons, and n-undecane, which is a representative species of unburned hydrocarbons. They may be used as surrogate hydrocarbon species for performing a bench flow reactor test for catalyst development.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.465-465
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• 2014

증식블랑켓모듈(TBM, Test Blanket Module)을 개발하여 왔다. 이 두 증식블랑켓모듈은 모두 헬륨냉각을 기반으로 개발 되어왔으며 이에 따라, 헬륨순환기, 헬륨히터 및 헬륨열교환기 등에 대한 기본적인 연구가 수행되었다. 이후 2012년 고체형 증식블랑켓모듈을 ITER TBM 개념으로 주도하기로 결정함에 따라, HCCR (Helium Cooled Ceramic Reflector) TBM의 보조계통인 하나인 헬륨냉각계통(HCS, Helium Cooling System)에 대한 개발이 본격적으로 이루어졌다. 한국원자력연구원에서는 HCCR TBM의 냉각성능을 만족하기 위하여 8 MPa, 1.5 kg/s 및 $300/500^{\circ}C$ (입구/출구 온도)의 운전조건을 갖는 헬륨냉각계통의 설계를 완료하였다. 설계된 헬륨냉각계통은 HCCR TBM에서 회수된 약 $450^{\circ}C$의 헬륨을 열회수기(recuperator)기와 냉각기를 통해 상온으로 냉각시킨 후, 필터를 통해 헬륨을 여과시킨다. 여과된 헬륨은 헬륨순환기에 의해 가압되어 열회수기를 다시 지나 $300^{\circ}C$ 이상으로 가열된다. 가열된 헬륨은 열회수기를 지나지 않는 상온의 헬륨과 혼합되어 최종적으로 HCCR TBM의 입구온도 조건인 $300^{\circ}C$로 맞추어 HCCR TBM에 공급된다. 이러한 열회수기 중심으로 '${\infty}$' 모양의 자가 교차로 설계된 헬륨냉각계통은 고온영역과 저온영역으로 냉각회로를 구분하여 순환기, 필터 및 각종 계측기의 운전온도 환경을 상온으로 유지시킬 수 있어 운전 및 유지보수 관점에서 이점이 있다. HCCR TBM의 헬륨냉각계통 설계 및 핵심 기기를 실증하고, 운전 경험을 쌓기 위하여 헬륨공급장치(HeSS, Helium Supply System)를 헬륨유량기준 1/3 규모(0.5 kg/s)로 구축하였으며, '14년까지 HeSS를 실증규모로 업그레이드 하기 위하여 80기압 환경에서 압축비 1.1, 유량 1.5 kg/s의 성능을 내는 헬륨순환기를 설치할 예정이다. 현재 구축된 1/3 규모 HeSS는 국내 구축된 전자빔 고열부하 시험 장비인 KoHLT-EB (Electron Beam)와 연계되어 HCCR TBM의 일차벽(플라즈마 대향부품)을 검증할 예정이며, 이를 통해 얻어진 열수력 DB는 현재 개발중인 핵융합로 안전해석코드인 GAMMA-FR 검증에 활용될 계획이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.696-701
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• 2018

The nitrogen oxides generated during combustion reactions have a great influence on the generation of acid rain and fine dust. As an NOx reduction method, exhaust gas recirculation combustion using Coanda nozzles capable of recirculating a large amount of exhaust gas with a small amount of air has recently been utilized. In this study, for the burner outlet with dual end opening, the use of a recirculation burner was investigated for the distribution of the pressure, streamline, temperature, combustion reaction rate and nitrogen oxides using computational fluid analysis. The gas mixed with the combustion air and the recirculated exhaust gas flow in the tangential direction of the circular cylinder burner, so that there is a region with low pressure in the vicinity of the fuel nozzle exit. As a result, a reverse flow is formed in the central portion of the burner near the center of the circular cylinder burner and the exhaust gas is discharged to the outside region of the circular cylinder burner. The combustion reaction occurs on the right side of the burner and the temperature and NOx distribution are relatively higher than those on the left side of the burner. It was found that the average NOx production decreased from an air flow ratio of 1.0 to 1.5. When the air flow ratio is 1.8, the NOx production increases abruptly. It is considered that the NOx production reaction increases exponentially with temperature when the air ratio is more than 1.5 and the NOx production reaction rate increases rapidly on the right-hand side of the burner.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.26-34
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• 2011

The present work addresses structural characteristics of natural gas flames in a lean premixed swirl-stabilized combustor with an attention focused on the effect of the formation of recirculation zones on the combustion instability. It is known that the recirculation zone plays an important role in stabilizing a turbulent, premixed natural gas flames by providing a source of heat or radicals to the incoming premixed fuel and air. To improve our understanding of the role of recirculation zones, the flame structure was investigated for various mixture velocities, equivalence ratios and swirl numbers. The optically accessible combustor allowed for the application of laser diagnostics, and Particle Image Velocimetry(PIV) measurements was used to characterize the flame structure under both cold flow conditions and hot flow conditions. Dynamic pressures were also measured to investigate characteristics of combustion at the same time. The results indicates that the formation of recirculation zone is strongly related to the occurrence of thermo-acoustic instabilities.