• 한국분무공학회지
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• 제16권2호
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• pp.90-96
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• 2011

Atomized liquid jets from the washing nozzle which configured with recirculation chamber for cleaning hot-zone area are accelerated and impinged on the head lamp surface. Cleaning efficiency of head lamp can be increased with injecting washing fluids into the hot-zone area. Experimental and numerical studies with various design parameters were executed to reveal the relations between internal geometry and internal flow in the washing nozzle. Spray structures were fitted with each of the head lamp surfaces and spray nozzles were optimized to the spray pattern. The recirculation chamber induces a recirculation flow and can be decreased the pressures perturbation inside the chamber. Orifice determines the mass flow rate. When the diameter of orifice is excessively large, it showed an unstable spray pattern. As a nozzle exit angle increases, density distributions are separated with two section. Also, as a protrusion length of nozzle exit increases, spray patterns are spread into a large area and density distributions showed unstable trend.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.586-591
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• 2003

The present study addresses experimental results to investigate the effect of the jet supply chamber configuration on the sonic/supersonic swirling jets, as the case study. The experiment is carried out using the convergent nozzle with a various different chamber configurations upstream the nozzle throat, which is composed of four tangential inlet holes for the swirling flows. The jet pressure ratio is varied between 3.0 and 7.0. The sonic/supersonic swirling jet flows are specified by the pitot impact and static pressure measurements and visualized using the Shadowgraph method. The results show that the major structures of the sonic/supersonic swirling jet are strongly influenced by the jet supply chamber.

• 한국가시화정보학회지
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• 제10권1호
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• pp.47-54
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• 2012

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

• 한국항공우주학회지
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• 제38권10호
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• pp.985-991
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• 2010

노즐 목 근처에 설치된 핀틀 형상이 노즐 내부 유동과 추력에 미치는 영향을 공압 실험으로 고찰하여 제시하였다. 핀틀 이동으로 노즐 목 면적이 감소하면 연소실 압력은 부드럽게 상승하나 추력은 핀틀 형상에 따라 증가 패턴이 다르게 나타났다. 동일한 노즐 목과 연소실 압력 조건에서 추력은 전체적으로 핀틀 형상이 오목한 것 보다는 볼록한 것이 컸다. 노즐 벽면 압력과 핀틀에 작용하는 하중은 핀틀 형상은 물론 핀틀 위치 및 노즐 목면적에 따라 큰 차이를 보였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.256-259
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• 2008

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some ejectors with a various of nozzle throat and mixing chamber diameter were manufactured precisely and tested for the comparison with the calculation results.

• 한국추진공학회지
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• 제24권6호
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• pp.1-9
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• 2020

케로신/액체산소를 추진제로 하는 직사각형 2열 오리피스를 갖는 1.5톤급 액체-액체 핀틀 분사기를 설계 및 제작하여 액체로켓엔진의 실운용 조건인 초임계 상태에서 핀틀 분사기의 연소성능 및 연소 안정성 검증 연소시험을 수행하였다. 연소시험결과 연소실 내부의 고혼합비 재순환 영역에서 생성되는 고온의 연소가스에 핀틀 팁이 손상되었다. 핀틀 팁으로 전달되는 열유속 또는 하중에 대한 냉각 성능을 증가시키기 위해 핀틀 분사기 내부에 인서트 노즐을 설치하였다. 연소시험 결과 인서트 노즐의 설치, AR 및 BF가 핀틀 팁 냉각 성능에 큰 영향을 주는 인자로 확인되었다.

• 대한기계학회논문집B
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• 제34권3호
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• pp.237-243
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• 2010

본 논문에서는 수치해석과 공압실험으로 핀틀 로켓에 적용된 핀틀 형상이 추력과 항력에 미치는 영향을 분석 하여 제시하였다. 핀틀 움직임으로 노즐목 면적이 감소할 때 연소실 압력은 부드럽게 증가한다. 그리고 핀틀 몸체의 압력에 의한 추력은 연소실 압력에 비례하여 증가하였으며 노즐 벽면 압력에 의한 추력 보다 큰 값을 가졌다. 그리고 노즐 내부의 충격파가 핀틀 형상과 압력비에 따라 변하기 때문에 노즐 벽면 압력에 의한 추력은 연소실 압력에 무관하였다. 핀틀에 의한 항력은 연소실 압력과 무관하게 완전히 선형적인 핀틀 형상에 서 최소 크기를 가졌다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.156-160
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• 2007

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.299-302
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• 2009

The objective of the present study is to analyze the transient flow through theejector system with the help of a computational fluid dynamics (CFD) method. An attempt is made to investigate the interesting and conflicting phenomenon of the infinite entrainment into the primary stream without an infinite mass supply from the secondary chamber. The results obtained show that the one and only condition in which an infinite mass entrainment can be possible in such types of ejectors is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium of pressures at the onset of the recirculation zone. A steady flow in the ejector system is valid only after this point.

• Journal of Advanced Marine Engineering and Technology
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• 제28권7호
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• pp.1123-1130
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• 2004

Numerical simulations have been carried out to investigate the effect of nozzle hole geometry on the combustion characteristics of the large diesel engine. 6S90MC-C. Spray and combustion phenomena were examined numerically using FIRE code. Wane breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Predictions on the cylinder peak pressure and NOx emission were first verified with the experimental data to confirm the reliability of numerical calculations. The comparison results showed good agreements within the range of 0.64% and 4.6% respectively. Finally, the effects of fuel spray angle and diameter on the engine performance were investigated numerically to find the optimum nozzle hole geometry considering fuel consumption, NOx emission and heat flux of the combustion chamber wall. It was concluded that the combustion gas recirculation in cylinder by changing fuel injection direction is an effective method to reduce NOx emission by about 10% with increasing fuel oil consumption, 1.4% in a large diesel engine.