• Title/Summary/Keyword: Orifice Diameter Ratio

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Spray Characteristics of Impinging Injectors in Crossflows (횡방향 유동에서 충돌형 분사기의 액체제트 분무 특성)

  • Song, Yoonho;Lee, Woongu;Ahn, Kyubok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.949-952
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    • 2017
  • Spray characteristics of the impinging injectors in subsonic crossflows were experimentally studied and compared with the plain-orifice injectors. By changing the impingement angle (60, 90, 120) which is the same orifice length to diameter ratio (L/d = 5), spray characteristics were investigated. In the view of the top view from the impinging injectors, as the impingement angle increases, the liquid column breakup length in the y-direction was decreased. On the other hand, when the impinging injector is viewed from the side view, the breakup length in the x direction is smaller than the previous plain-orifice injectors, which mean that the atomizing performance of the impingement-type injector is better than that of the single-hole orifice.

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A Study on NOx Reduction Mechanism in a Closed Vessel with Opposed Dual Pre-chambers (대향 부연소실이 있는 밀폐연소실 내의 $NO_x$ 저감기구에 대한 연구)

  • Kim, Jae-Heon;Lee, Soo-Gab;Jeung, In-Seuck
    • Journal of the Korean Society of Combustion
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    • v.2 no.1
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    • pp.17-27
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    • 1997
  • It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

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Combustion Characteristics of Landfill Gas in Constant Volume Combustion Chamber for Large Displacement Volume Engine (IV) -Torch Ignition (2) - (대형기관 모사 정적연소실에서 매립지 가스의 연소특성에 대한 연구 (IV) -토치 점화 (2)-)

  • Ko, Ansu;Ohm, Inyong;Kwon, Soon Tae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.2
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    • pp.135-146
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    • 2015
  • This paper is the fourth on the combustion characteristics of the landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine and the second dealing with torch ignition. It discusses the combustion characteristics of torch ignition on the basis of the heat release and visualization. The results show that the jet and/or spout from the torch promote combustion by accelerating the flame front in the main combustion chamber. In addition, a hot gas jet exists when the orifice diameter is 4 mm, whereas the flame passes directly through the orifice if the diameter is 6 mm or greater. In addition, the effect of torch ignition differs according to the combination of the methane fraction, torch volume, and orifice size because various combustion processes occur as a result of the interaction of these parameters. Finally, it was found that the most suitable torch should have an orifice diameter of not less than 6 mm and an area ratio of not more than 0.15 to secure a consistent combustion process in a real engine.

Evaluation of the Induction and Ionized Field Charging Methods for Electrostatic Nozzles of Orchard Sprayer

  • Laryea, G.N.;No, S.Y.;Lee, D.H.
    • Agricultural and Biosystems Engineering
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    • v.3 no.1
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    • pp.29-34
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    • 2002
  • Two charging methods of electrostatic nozzle, i.e. induction and ionized field corona charging, were designed and evaluated for orchard sprayer application. An artificial (metallic) target was constructed and used in this experiment. The charge-to-mass ratio for the induction electrode was measured by using the Faraday cage. Two conventional pressure-swirl nozzles have been employed with different orifice diameters under the same experimental operating conditions. A commercial pressure-swirl nozzle with orifice diameter of 1.0 was used for the conventional spray. The diameter of the electrostatic was 0.59 mm. The experiment was carried out for individual nozzle sprays at $0^{\circ}$, $20^{\circ}$ and $50^{\circ}$ oriented angles and three nozzles, sprayed simultaneously at a distance of 1.0 and 2.0 m from the nozzle tip to the target. The nozzles were mounted on a carriage with constant speed of 1.26 km/h with a blower attached. The weighing method was employed to evaluate for the spray deposition, ground loss and estimated drift. The results show more promising for the induction charging method, especially at $20^{\circ}$oriented angle at a distance of 1.0 m from the target for a single nozzle and when all three nozzles were operated simultaneously for spray deposition. The results of the induction charging method show promising with the developed electrostatic technique.

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A Study on the Disintegration and Spreading Behavior of Fuel-spray Emanating from a Liquid-thruster Injector by Pseudo-3D Spatial Distribution Measurement (준3차원적 공간분포 계측에 의한 액체추력기 인젝터 연료분무의 분열 및 확산 거동에 관한 연구)

  • Kim, Jin-Seok;Kim, Jeong-Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.5
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    • pp.9-17
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    • 2008
  • Pseudo-3D spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-propellant thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio ($L/d_o$) of 1.67 and under the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray. Although the distribution of spray characteristic parameters is symmetric against the geometric axis of nozzle orifice, their absolute values are asymmetric.

Damping Characteristics of a Helmholtz Resonator Under the Flow Area (튜브(모사 챔버)내의 유동특성이 음향공 감쇠 능력에 미치는 영향)

  • Song, Jae-Gang;Kim, Young-Mun;Ko, Young-Sung;Kim, Sun-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.82-85
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    • 2008
  • A Helmholtz resonator is applied to control high frequency combustion instability in liquid rocket engine. Damping characteristics of the Helmholtz resonator are investigated by the flow characteristic and its design. To simulate combustion instability, resonance in a test section(with fixed volume) is made by a pressure pulsator, and then damping characteristics are investigated. Its orifice length and diameter are selected as the design parameters and flow rates are varied to reveal the effect on damping characteristics. The experimental results show that a Helmholtz resonator is also working with flows. When length and diameter of an orifice are small, the tuning frequency increases as the flow velocity increases.

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Damping Characteristic of Resonator according to Geometry Variation (음향공 형상 변화에 따른 감쇠 특성 변화)

  • Kim, Jai-Ho;Park, Jin-Ho;Yu, I-Sang;Jang, Ji-Hun;Ko, Young-Sung
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.35-38
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    • 2011
  • Damping characteristic according to acoustic cavity's geometries was investigated to control the high frequency combustion instability occurring in the Liquid Rocket Combustion Chamber by experimental test and linear analysis. Its diameter was determined as a design parameter and its orifice length and diameter were appointed as fixed parameter in this study. Result shows that the damping capacity has been almost constant through all the experiments despite using the same orifice and helmholtz resonators which have different volume.

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Characteristics of the Internal Flow in the Scaled-Up Fuel Nozzle (연료 노즐을 확대한 모형노즐에서의 내부유동 특성)

  • 박장혁;홍성태;구자예
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.3
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    • pp.199-210
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    • 1996
  • The measurements of velocities of internal flow in a scaled-up nozzle were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. The investigated length to diameter ratio(L/d) of the orifice were 1, 3, 4, 5 and 8, and inlet radius to diameter ratio(r0/d) were 0 and 0.5. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds number ranging between 15,000 and 28,000, and L/d ranging between 1 and 8 in sharp and round inlet nozzle. The turbulent intensity and turbulent kinetic energy at exit in a sharp inlet nozzle were higher than that in a round inlet nozzle. For sharp inlet nozzle, fluctuating velocities near exit were decreased with increasing L/d.

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Spray characteristics on mixing region scale of twin fluid atomizer (이류체 분사노즐의 혼합영역 형상에 따른 분무특성)

  • 김병문;김혁주;이충원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.2147-2159
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    • 1991
  • The effects of principal dimensions of internal mixing twin-fluid atomized and operating conditions on the atomizing characteristics are experimentally investigated. The tests are conducted over the wide range of air/liquid ratio to predict influences of the diameter and length of nozzle, contacting angle between air and liquid in the mixing chamber, and air orifice diameter on the mean drop size(SMD), spray angle, distribution of drop size, and spray dispersion, And also, initial distribution of liquid column by air stream within the mixing chamber are observed through the transparent nozzles. A He-Ne laser particle sizer(MALVERN Model 2604) was used to measure the Sauter.s mean diameter( $D_{321}$) and droplet sizes distribution. In this experiment the air/liquid ratio, mixing length and nozzle diameter have a great influence on SMD, spray angle, droplet sizes distribution and spray dispersion.

An Experimental Study of the Spray Characteristics for an Oxidizer-rich Preburner Injector (산화제 과잉 예연소기 인젝터의 분무 특성에 관한 연구)

  • So, Y.S.;Yang, J.H.;Han, Y.M.;Choi, S.M.
    • Journal of ILASS-Korea
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    • v.12 no.1
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    • pp.58-64
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    • 2007
  • The spray characteristics of the oxidizer-rich preburner are investigated. This system is generally operated at an oxidizerfuel mixture ratio of 50. The spray quality and mixing performance are very important for safe combustion. To know the spray characteristics of the oxidizer-rich preburner, we have designed various swirl injectors and measured droplet velocity and size by the PDPA system. The flow discharge coefficient of the fuel orifice is $0.12{\sim}0.21$, oxidizer orifice discharge coefficient is $0.16{\sim}0.28$. From the spray visualization, fuel nozzle spray angle is $15^{\circ}{\sim}25^{\circ}$, oxidizer nozzle spray angle is $65^{\circ}{\sim}85^{\circ}$ and combined spray angle is reduced $2^{\circ}{\sim}5^{\circ}$ compared to the oxidizer nozzle only case. From the PDPA measurement, droplet SMD is $175\;{\mu}m$ at 50 mm and $190\;{\mu}m$ at 100 mm of variant 1 combined case. The number concentration measurement revealed the reason of the droplet diameter increasement with distance. That is due to drop coalescence results from collision of drops which is occurred in dense sprays at a long distance from nozzle orifice exit.

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