• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.45-53
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• 2022

In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).

• Journal of the KSME
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• v.33 no.12
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• pp.1031-1042
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• 1993

연소현상에 대한 이해를 증가시키기 위하여 화염을 이용한 많은 실험적 연구가 이루어져 왔다. 특히 연소 모델의 개선과 증명을 위하여는 화염에서의 성분 농도 측정이 필수적이며, 최근에 들어 측정 가능해진 래디컬성분의 측정은 연소해석분야에 많은 진전을 가져왔다. OH, H 및 O는 연료의 분해 (decomposition) 및 연소 산화물생성 이외에도 CO와 NO 같은 공해물질의 형성등 연소과정에서 매우 중요한 래디컬들이며, 특히 화염영역에서의 OH의 전파(transport)는 화염의 점화 및 안정성 (stability)에도 큰 영향을 미친다. OH래디컬은 연소과정에서 가장 중요한 성분 중 하나이며, 또한 스펙트럼이 비교적 잘 알려져 있어 레이저 유도 형광의 적용이 용이하므로 화염에서의 OH농도 측정에 LIF(laser induced fluorescence) 또는 PLIF(planar laser induced fluorescence)가 널리 사용되고 있다. 따라서 LIF 및 PLIF의 원리 및 연소분야에서의 응용을 OH농도 측정을 중심으로 소개하고자 한다.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.250-258
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• 2010

A numerical analysis of reactive flow in a liftoff flame is accomplished to elucidate the characteristics of flame propagation velocity and volume integral of reaction rate with the variation of nozzle diameter and fuel injection flow rate in a liftoff flame consisted with fuel rich region, fuel lean region and diffusion flame region. The increase of fuel injection velocity enhances flame propagation velocity for the selected three nozzle diameter(d=0.25, 0.30, 0.35mm), but its effect on the flame propagation velocity is not much greater than 4.3%. The increase of fuel flow rate is directly and linearly related with the volume reaction rate and so the volume reaction rate, not the flame propagation velocity, might be considered to accommodate the variation of fuel flow rate in a liftoff flame.

• 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.17 no.5
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• pp.37-46
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• 2013

The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

• 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 Power System Engineering
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• v.15 no.3
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• pp.5-11
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• 2011

디젤기관의 경우는 종래부터 직분식이 주류를 이루었고, 근래에는 분사압력의 고압화가 진행중이다. 분사압력의 고압화에 의해 연소효율의 향상 및 배출가스중의 입자상물질(PM:Particulate Matter)의 저감을 유도하고 있으나, 연소가스의 고온화로 인해 질소산화물(NOx:Nitrogen Oxides)은 증가한다. 따라서, 분사기간의 지연(Retard)이나 파일럿분사(Pilot injection)등의 혼합기제어에 의해 질소산화물의 저감을 꾀하고 있다. 이와 같이 디젤기관에 있어서도 혼합기 형성의 최적화에 의한 연소제어를 시도하는 수법이 중시되고 있고, 이를 위해서는 디젤분무 구조에 기초한 혼합기의 형성기구에 대한 규명이 매우 중요하다. 그러므로 본 연구에서는 보다 고도의 혼합기형성 제어를 위한 기초연구로서 고온 고압장에서의 증발디젤자유분무구조를 해석하였으며, 계측영역은 연료와 주위기체와의 혼합이 활발히 진행되는 분무의 하류영역으로 설정하고, 입자화상속도측정법(particle Image Velocimetry:PIV)을 이용한 분무의 유동해석을 기초로 증발 디젤분무의 구조 해석을 행하였다. 실험조건으로서 분사압력을 72MPa, 112MPa로 각각 변화시켰다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.277-280
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• 2009

Mechanism of combustion frequencies occurring during combustion is experimentally investigated in model combustor with V-gutter flameholder. this combustor has a long duct shape with a cross section area of $40{\times}40\;mm$. The v-gutter type flameholder with 14mm width is mounted at the bottom of combustor. Kerosene and methane were used as fuel, and these fuel were injected transversely into air crossflow. It is found that combustion frequencies were considered as 1L longitudinal mode caused by combustor geometry and vortex shedding mode of flameholder. And fuel phase effect and nozzle effect were also observed in the low frequency range.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.1
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• pp.51-56
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• 2007

Flow characteristics in a liquid fuel ramjet combustor were investigated using the PIV method. The combustor has two rectangular inlets that form a $90^{\circ}$ angle each other. Three cases of test combustors are made in which those inlet angles are $30^{\circ},\;45^{\circ}\;and\;60^{\circ}$. The experiments were performed in a water tunnel test with the same Reynolds number as Mach 0.3 at the inlet. PIV software was developed to measure the characteristics of the flow field in the combustor. A large and complex recirculating flow was measured in the dome area with 4 different dome size. Experimental results shows that 1/3 dome size of combustor diameter is suitable and smaller inlet angle provide large recirculation flow at the dome of combustor as a frame holder in this experimental ranges but need to consider secondary recirculation flow in a junction region to optimize the configuration of ramjet combustor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.330-335
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• 2017

Recently many studies have been made for the development of propulsion system with wide range flight from supersonic to hypersonic. Dual Mode scramjet engine as a hybrid cycle with advantage of ramjet and scramjet has one combustor. It works under the ramjet mode (subsonic combustion) and scramjet mode (supersonic combustion) respectively. In this study, Experimental results of hot firing tests of dual scramjet engine designed on the condition of Mach 3.5~6 as a flight Mach number are discussed. The tests were carried out on a ground test bench under free stream condition of Mach 6 at 27.6km altitude. In the tests, the adopted design and technological solutions were verified and efficient operation of the dual mode ramjet engine with Kerosene combustion during 5 seconds was demonstrated.