• Title, Summary, Keyword: Nozzle Pressure

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Numerical Study on the Effect of Nozzle Geometry on the Small CRDI Engine Performance (노즐 형상 변경이 소형 CRDI 엔진의 성능에 미치는 영향에 대한 수치 해석적 연구)

  • Min, Se Hun;Suh, Hyun Kyu
    • Journal of ILASS-Korea
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    • v.20 no.4
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    • pp.254-260
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    • 2015
  • The objective of this study is to investigate the effect of multi-hole nozzle on the performance of small CRDI engine. Combustion and exhaust emission characteristics of engine were studied by using CFD simulation with ECFM-3Z combustion model. The conditions of simulation were varied with nozzle geometry, injection timing and injection quantity. In addition, the results were compared in terms of combustion pressure, rate of heat release, $NO_x$ and soot emissions. It was found that combustion pressure was increased when injection timing was advanced. The rate of heat release of 6 hole nozzle was higher than that of 12 hole nozzle since the quantity of fuel impinged at the bottom of piston rim was different under different injection timing conditions. In the case of $NO_x$ emission, 6 hole nozzle generated more $NO_x$ emission than 12 hole nozzle. On the other hand, in the case of soot emission, 12 hole nozzle showed higher value than 6 hole nozzle because injected fuel droplets from multi-hole nozzle were coalesced.

Computational Analysis of the Flowfield of a Mixer-Ejector Nozzle (Mixer-Ejector 노즐 유동장에 관한 수치해석)

  • Park, Yun-Ho
    • Journal of the Korean Society of Propulsion Engineers
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    • v.6 no.1
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    • pp.71-82
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    • 2002
  • A time-iterative compressible Navier-Stokes code is developed to analyze the flowfield of a two-dimensional ejector nozzle system. A parametric study has been made for two controlling parameters, duct to nozzle area ratio and nozzle pressure ratio. Results show that there is an optimum area ratio for an efficient pumping of secondary flow. At high area ratios, a freestream flow directly passes through the mixing duct without giving adequate pumping. While at low area ratios, jet boundary is acting as a blockage to incoming flow. The nozzle pressure ratio variation shows that the pumping rate increases as the pressure ratio increases provided there is no interaction between the shroud wall and the shock cell structure.

Characteristics of Supersonic Nozzle and Jet Impingement (초음속 노즐과 벽면 충돌제트의 유동특성)

  • Hong, Seung-Kyu;Lee, Kwang-Seop;Sung, Woong-Je
    • Journal of the Korea Institute of Military Science and Technology
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    • v.4 no.2
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    • pp.256-262
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    • 2001
  • Viscous solutions of supersonic side jet nozzle and supersonic jet impinging on a flat plate are simulated using three-dimensional Navier-Stokes solver. For rapid and abrupt control of a missile in supersonic flight, side jet on a missile body is found to be a useful devise as evidenced by recent missile development at several nations. The magnitude of the side jet and the duration of it decide the level of control of such a missile system. The aerodynamic characteristics of the side jet devise itself are examined in terms of key parameters such as the side jet nozzle geometry, the chamber pressure and temperature. On the other hand, the jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. As the plate is placed close to the nozzle, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. The amplitude of wall pressure fluctuations subsides as the plate/nozzle distance increases, and the frequency of the wall pressure is estimated on the order of 10.0 KHz. Objectives of this paper are to show accurate simulation of nozzle flow itself and to demonstrate the jet flow structure when the jet interacts with a wall at a close range.

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SPRAY AND COMBUSTION CHARACTERISTICS OF HYDROCARBON FUEL INJECTED FROM PRESSURE-SWIRL NOZZLES

  • Laryea Gabriel Nii;No Soo-Young
    • Journal of ILASS-Korea
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    • v.9 no.4
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    • pp.31-37
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    • 2004
  • This paper presents spray and combustion characteristics of hydrocarbon fuel injected from pressure-swirl nozzles. Three commercial nozzles with orifice diameters of 0.256, 0.308 and 0.333mm and injection pressures ranging from 0.7 to 1.3 MPa were selected f9r the experiments. Spray characteristics such as breakup length. spray angle and drop size (SMD) were analyzed using photo image analyses and Malvern Panicle Size Analyzer. The drop size was measured with and without a blower at the same measuring locations. The flame length and width were measured using photo image analyses. The temperature distribution along the axial distance and the gas emission such as CO, $CO_2\;and\;NO_x$ were studied. The breakup length decreased with an increase in injection pressure for each nozzle but increased with an increase in nozzle orifice diameter. The spray angle increased and SMD decreased with an increase in injection pressure. The flame with an increased linearly with an increase in injection pressure and in nozzle orifice diameter. The flame temperature increased with an increase in injection pressure but decreased along the axial distance. The maximum temperatures occurred closer to the burner exit and flame at axial distance of 242mm from the diffuser tip. The experimental results showed that the level of CO decreased while that of $CO_2\;and\;NO_x$ increased with an increase in injection pressure and nozzle orifice diameter.

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Numerical investigation of detonation combustion wave propagation in pulse detonation combustor with nozzle

  • Debnath, Pinku;Pandey, K.M.
    • Advances in aircraft and spacecraft science
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    • v.7 no.3
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    • pp.187-202
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    • 2020
  • The exhaust nozzle serves back pressure of Pulse detonation combustor, so combustion chamber gets sufficient pressure for propulsion. In this context recent researches are focused on influence of nozzle effect on single cycle detonation wave propagation and propulsion performance of PDE. The effects of various nozzles like convergent-divergent nozzle, convergent nozzle, divergent nozzle and without nozzle at exit section of detonation tubes were computationally investigated to seek the desired propulsion performance. Further the effect of divergent nozzle length and half angle on detonation wave structure was analyzed. The simulations have been done using Ansys 14 Fluent platform. The LES turbulence model was used to simulate the combustion wave reacting flows in combustor with standard wall function. From these numerical simulations among four acquaint nozzles the highest thrust augmentation could be attained in divergent nozzle geometry and detonation wave propagation velocity eventually reaches to 1830 m/s, which is near about C-J velocity. Smaller the divergent nozzle half angle has a significant effect on faster detonation wave propagation.

Characteristics of Supersonic Jet Impingement on a Flat Plate

  • 홍승규;이광섭;박승오
    • 한국전산유체공학회:학술대회논문집
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    • pp.134-143
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    • 2001
  • Viscous solutions of supersonic jet impinging on a flat plate normal to the flow are simulated using three-dimensional Navier-Stokes solver. The jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. In the present study, the nozzle contour and the pressure ratio are held fixed, while the jet impinging distance is varied to illuminate the characteristics of the jet plume with the distance. As the plate is placed close to the nozzle at 3D high, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. Here D is the nozzle exit diameter. The amplitude of wall pressure fluctuations subsides as the distance increases, but the maximum pressure level at the plate is achieved when the distance is about 4D high. The frequency of the wall pressure is estimated at 6.0 kHz, 9.3 kHz, and 10.0 kHz as the impinging distance varies from 3D, 4D, to 6D, respectively.

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A Study on Design of High Pressure Injection Nozzle for Avoiding Chip Curling (칩 말림 방지를 위한 고압 분사 노즐 설계에 관한 연구)

  • Yi, Chung-Seob;Yun, Ji-Hun;Jeong, In-Guk;Song, Chul-Ki;Suh, Jeong-Se
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.6
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    • pp.793-798
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    • 2011
  • In this study, it was grasped to the flow characteristics of cutting fluid injected by nozzle installed in high pressure holder for avoiding chip curling occurred during machining process. And for avoiding chip curling, the possibility of elimination under various chip conditions was checked. Consequently, the highest discharging pressure and velocity was shown in 150 of nozzle inflow angle. Also as nozzle outlet diameter is small, the pressure and velocity of injected flow are high. Moreover, It could be confirmed that width and thickness of chip have no direct effect on chip elimination and it is achieved by torque generated by injected cutting fluid.

A Study on the Characteristics of Fuel Spray (燃料噴霧特性 에 관한 硏究)

  • 진호근;이창식;서정일
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.3
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    • pp.256-260
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    • 1982
  • This paper presents the characteristics of fuel spray in a diesel engine. In this paper, in order to obtain spray droplet size in a diesel engine, water was injected into the cylinder at room temperature and pressure by injection system. Spray droplet size was measured by liquid immersion technique with a lubricant used as an immersion liquid for spray water from injection nozzle. In this experiment, single hole type throttle nozzle are used at same operating conditions, which included opening pressure of nozzle, fuel delivery, and injection speed. Sauter mean diameter decrease with the increase of injection pressure and decrease in injection nozzle diameter. The rate of spray penetration increased with increasing injection pressure and diameter of injection nozzle at the constant spray conditions.

An Experimental Study of Underexpanded Moist Air Jet Impinging on a Flat Plate

  • Lee, D.W.;S.C. Baek;S.B. Kwon;Kim, H.D.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.768-773
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    • 2004
  • When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is underexpanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with nonequilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics can not even know. In the present study, the effect of the nonequilibrium condensation on the underexpanded moist air jet impinging on a vertical flat plate is investigated experimentally. Flow visualization and impact pressure measurement are performed for various relative humidities and flat plate positions. The obtained results show the plate shock and Mach disk are dependent on the nozzle pressure ratio and the relative humidity, but for a given nozzle pressure ratio, the diameters of the plate shock and Mach disk depend on the stagnation relative humidity. The impact pressure deviation from the flow of without condensation is large, as the relative stagnation humidity increases.

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Study on the Lateral Force Fluctuations in a Rocket Nozzle (로켓노즐에서 발생하는 횡력변동에 관한 연구)

  • Nagdewe, Suryakant;Lee, Jong-Sung;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.315-319
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    • 2009
  • Investigation of the lateral force fluctuations in an axisymmetric overexpanded compressed truncated perfect (CTP) nozzle for the shutdown transient is presented. These nozzles experience side-loads during start-up and shut-down operations, because of the flow separation at nozzle walls. Two types of flow separations such as free shock separation (FSS) and restricted shock separation (RSS) shock structure occur. A two-dimensional unsteady numerical simulation has been carried out over an axisymmetric CTP nozzle to simulate the lateral force fluctuations in nozzle during shutdown process. Reynolds Averaged Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Governing equations are solved by coupled implicit scheme. Two equation k-$\omega$ SST turbulence model is selected. Unsteady pressure is measured at four locations along the nozzle wall. Present pressure variation compared well with the experimental data. During shutdown transient, separation pattern varies from FSS to RSS and finally returns to FSS. Several pressure peaks are observed during the RSS separation pattern. These pressure peaks generate lateral force or side loads in rocket nozzle.

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