• 한국항공우주학회지
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• 제33권1호
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• pp.48-53
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• 2005

본 연구의 목적은 기계적인 전단층 자극방법을 이용 스월제트 혼합향상의 가능성을 고찰함에 있다. 이를 위해 기계적 자극장치가 설계, 제작되었다. 주요 구성품으로는 두개의 아음속 노즐, 스월 발생기, 그리고 유동 자극기 등이다. 실험은 다음과 같은 다양한 헬리컬 모드들에서 수행되었다; m=+0, m=$\pm$1, m=$\pm$2, m=$\pm$3, m=$\pm$4. 열선유속계를 이용한 plane 파동과 헬리컬 파동 자극에 따른 제트속도 측정이 이루어 졌다. 다양한 헬리컬 모드에서의 결과 값들이 기준 값(plane-wave)과 비교되었다. 획득된 결과는 3-D mesh plot 과 2-D contour plot으로 표현되었다. 이로써 새로 고안된 장치는 헬리컬 불안정파 자극에 대한 효과를 입증하였고 또한 결과적으로 스월제트의 혼합을 증진시켰다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.36.2-36.2
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• 2005

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.99.1-99.1
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• 2005

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.341-346
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• 2001

The gun-type gas burner adopted in this study is generally composed of some slits and swirl vanes. Therefore, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate $450\;{\ell}/min$, which is equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. When the burner has only swirl vanes, the axial mean velocity component shows the characteristic that spreads more remarkably toward radial direction than axial one, but when it has only slits, that is developed spreading more toward axial direction than radial one. Therefore, because the biggest speed is spurted in slits and it derive main flow toward axial direction encircling rotational flow that comes out from swirl vane that is situated on the inside of slits, both slits and swirl vanes composing of cone type gas burner act role that decreases the speed near slits and increases the flow speed in the central part of a burner. Moreover, because rotational flow by swirl vanes and fast jet flow by slits increase turbulent intensities effectively coexisting, the turbulent kinetic energy is distributed with a bigger size fairly near slits than burner models which have only slit or swirl vanes within X/R<0.6410.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.26-33
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• 2007

The intake swirl motion, as one of dominant effects for an engine combustion. is very effective for turbulence enhancement during the compression process in the cylinder of 2-valve engine. Because the combustion flame speed is determined by the turbulence that is mainly generated from the mean flow of the charge air motion in intake port system. This paper describes the experimental results of swirl flow and combustion characteristics by using the oil spot method and back-scattering Laser Doppler velocimeter (LDV) in 2-valve single cylinder transparent LPG engine using the liquid phase LPG injection. For this. various intake port configurations were developed by using the flow box system and swirl ratios for different intake port configurations were determined by impulse swirl meter in a steady flow rig test. And the effects of intake swirl ratio on combustion characteristics in an LPG engine were analyzed with some analysis parameters that is swirl ratio. mean flow coefficient, swirl mean velocity fuel conversion efficiency. combustion duration and cyclic variations of indicated mean effective pressure(IMEP). As these research results, we found that the intake port configuration with swirl ratio of 2.0 that has a reasonable lean combustion stability is very suitable to an $11{\ell}$ heavy-duty LPG engine with liquid phase fuel injection system. It also has a better mean flow coefficient of 0.34 to develope a stable flame kernel and to produce high performance. This research expects to clarify major factor that effects on the design of intake port efficiently with the optimized swirl ratio for the heavy duty LPG engine.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• 한국추진공학회지
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• 제6권2호
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• pp.29-36
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• 2002

두 번째 벤츄리 끝단 각도가 가스터빈 연소기의 유동 및 분무 특성에 미치는 영향을 이해하기 위해 스월 vane 형태의 2중 스월컵을 장착한 산업용 가스터빈 엔진에 대해 두 번째 벤츄리 끝단 각이 수렴형, 직선형, 발산형의 세 경우에 대해 실험을 수행하였다. 두 번째 벤츄리 끝단 각도의 변화가 가스터빈 연소기의 재순환 영역의 위치, 크기 및 형상 등의 유동 특성과 연료 액적 분무 형태를 크게 변화시킴을 확인 할 수 있었다. 발산형 벤츄리에서는 내부 재순환 영역이 점화가 일어나는 지점에서 가까운 곳에서 형성되므로 화염의 안정화에는 탁월할 것으로 판단되지만, 수렴형 벤츄리에서 가장 작고 균일한 크기의 액적들이 측정되었고, 내부 재순환 영역이 연소기 내에 길게 형성된 점으로 고효율, 저공해 연소기로는 수렴형 벤츄리의 경우가 적합하리라 판단된다.

• 대한기계학회논문집B
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• 제25권2호
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• pp.225-234
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• 2001

This paper represents the vector fields, three dimensional mean velocities, the turbulent intensities, the turbulent kinetic energy, and the Reynolds shear stresses in the X-Y plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rates 350 and 450ℓ/min respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component exists in the narrow slits situated radially on the edge of gas swirl burner, for that reason, there is some entrainment phenomena of ambient air in the outer region of burner. Moreover, mean velocities in the initial region are largely distributed near the outer region of burner at Y/R≒0.97, but they diffuse and develop into the center flow region of burner according to the increase of axial distance. The turbulent intensities and the turbulent kinetic energy due to large inclination of mean velocity and swirl effect show that the maximum value in the initial region of burner is formed in the narrow slits situated radially on the edge of gas swirl burner and large values are mainly formed in the entire region of burner after X/R=2.4358, hence, the combustion reaction is anticipated to occur actively near this region. And the Reynolds shear stresses are also largely distributed from slite to vanes of gas swirl burner in the intial region, but their values largely disappear after X/R=3.2052.

• 대한기계학회논문집B
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• 제27권1호
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• pp.95-104
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• 2003

The objective of this work is to investigate the turbulent reacting flow in a three dimensional combustor with emphasis on thermal NO emission through a numerical simulation. Flow field is analyzed using the SIMPLE method which is known as stable as well as accurate in the combustion modeling, and the finite volume method is adopted in solving the radiative transfer equation. In this work, the thermal characteristics and NO emission in a three dimensional combustor by changing parameters such as equivalence ratio and inlet swirl angle have investigated. As the equivalence ratio increases, which means that more fuel is supplied due to a larger inlet fuel velocity, the flame temperature increases and the location of maximum temperature and thermal NO has moved towards downstream. In the mean while, the existence of inlet swirl velocity makes the fuel and combustion air more completely mixed and burnt in short distance. Therefore, the locations of the maximum reaction rate, temperature and thermal NO were shifted to forward direction compared with the case of no swirl.

• 대한기계학회논문집B
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• 제33권9호
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• pp.666-673
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• 2009

The turbulent swirling flow field characteristics of a gun-type gas burner with a combustion chamber were investigated under the cold flow condition. The velocities and turbulent quantities were measured by hot-wire anemometer system with an X-type probe. The turbulent swirling flow field in the edge of a jet seems to cause a recirculation flow from downstream to upstream due to the unbalance of static pressure between a main jet flow and a chamber wall. Moreover, because the recirculation flow seems to expand the main jet flow to the radial and to shorten it to the axial, the turbulent swirling flow field with a chamber increases a radial momentum but decreases an axial as compared with the case without a chamber from the range of about X/R=1.5. As a result, these phenomena can be seen through all mean velocities, turbulent kinetic energy and turbulent shear stresses. All physical quantities obtained around the slits, however, show the similar magnitude and profiles as the case without a chamber within the range of about X/R=1.0.