• Title/Summary/Keyword: Jet Velocity Distribution

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A Study on the Characteristic of Impinging Pressure Distribution in the Three Dimensional Impinging Water Jet (삼차원(三次元) 수분류(水噴流)의 충돌(衝突) 압력(壓力) 분포(分布) 특성(特性)에 관(關)한 연구(硏究))

  • Lee, J.S.;Choi, K.K.
    • Solar Energy
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    • v.18 no.3
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    • pp.217-228
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    • 1998
  • The purpose of this research is to investigate the characteristics of static and total pressure distribution in the upward free water jet system impinged on a downward flat plate. The rectangular nozzle was used and its contraction and aspect ratio was five and about seven respectively. Experimental conditions considered were jet velocity, distance between nozzle and flat plate, height of supplementary water. It was founded that pressure distribution on the flat plate had the Gaussian curve when the pressure at stagnation point and impinging half width were chosen as the scaling parameters. The maximum pressure was shown at the stagnation point. The central impingement velocity decreased with the increment of distance between nozzle and flat plate, and its slop of decay was similar to that of chracteristics decay region in the three-dimensional free jet.

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Experimental Study on the Spray Characteristics for Sludge Removal Nozzle with High Pressure (슬러지 제거용 고압분사 노즐특성에 관한 실험적 연구)

  • Lee, Sam-Goo
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.40 no.2
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    • pp.155-160
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    • 2004
  • Water jet trajectories and velocity deficits from a high pressurize nozzles were experimentally observed. In this article, several parameters affecting plugging and erosion onto the steam generator tube were quantitatively analyzed. Visualization, velocity distribution, and spray growth rate with different nozzle configurations have been mainly focused using a 2-D PDPA (Phase Doppler Particle Analyzer) system. The results indicated that trajectories along the centerline regardless of their momentum has its potential core region. However, the phenomena from the peripheral part need to be meticulosly considered. Accordingly, it is evident that quantitative velocity deficits at the outer region are outstanding due to the aerodynamical drag and entrainment.

분배계통에 따른 지하주차장 환기설비 성능의 예측

  • 김경환;이재헌;오명도;김종필
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.10
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    • pp.982-992
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    • 2001
  • In this paper, the performance of ventilation equipments in enclosed parking garages were investigated for several air distribution systems by numerical method. Air change effectiveness of the non-mixing system was 0.42. It meant that more supply air as much as the design supply air was needed to maintain good indoor air quality. In the high speed nozzle ventilating system which is most expensive one, air change effectiveness was 0.54. Therefore this system satisfied to ventilation design. In the jet fan ventilating systems, air change effectiveness for jet fan ventilating system-A with 18 jet fans and jet fan ventilating system-B with 6 jet fans in circulation mixing arrangement were 0.565 and 0.42 respectively. Jet fan ventilating system-C with 6 jet fans in transport mixing arrangement was 0.535. Jet fan ventilating system-A and jet fan ventilating system-C met the ventilation design. But velocity in jet fan ventilating system-A was over 2.0m/s which is inappropriate in human comfort. Therefore this system is not proper to ventilation. Jet fan ventilating system-C was the optimum one for enclosed parking garages among 5 systems examined in this paper.

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Flame Structure of Moderate Turbulent Combustion in Opposed Impinging Jet Combustor (대항분출 연소기의 난류화염 구조)

  • Cho, Yong-Jin;Yoon, Young-Bin;Lee, Chang-Jin
    • 한국연소학회:학술대회논문집
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    • 2002.06a
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    • pp.46-51
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    • 2002
  • The measurement of velocity and stain rate field has been conducted in opposed impinging jet combustion. When a smaller diameter (5mm) orifice of pre-chamber was used, previous studies had reported that the combustion phase showed a shift from weak turbulent combustion to moderate turbulent combustion in the modified Borghi Diagram. In the case with smaller orifice diameter (5mm), NOx emission was substantially reduced by a factor 1/2 while the combustion pressure remains at the same as that in the conventional combustion. Hence, in this study, the experiment setup using PIV technique was designed to identify the relation of the strain rate distribution and NOx reduction associated with moderate turbulent combustion.

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Characteristics of Turbulent Impinging and Wall Jet Flow for a Circular Nozzle with Various Exit Wall Thickness (다양한 벽면 두께를 갖는 원형 노즐에서 분사되는 난류 충돌 및 벽면 제트 유동장 특성)

  • Yang, Geun-Yeong;Yun, Sang-Heon;Son, Dong-Gi;Choe, Man-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.6
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    • pp.751-757
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    • 2001
  • An experimental study of impinging jet-flow structure has been carried out for a fully developed single circular jet impingement cooling on a flat plate, and the effect of the wall thickness at nozzle exit edge is investigated. Impinging jet flow structures have been measured by Laser-Doppler Velocimeter to interpret the heat transfer results presented previously by Yoon et al.(sup)(10) The peaks of heat transfer rate are observed near the nozzle edge owing to the radial acceleration of jet flow when the nozzle locates close to the impingement plate. The growth of the velocity fluctuations in the wall jet flow is induced by the vortices which originate in the jet shear layer, and consequently the radial distribution of local Nusselt numbers has a secondary peak at the certain radial position. As a wall of circular pipe nozzle becomes thicker for small nozzle-to-target distance, the entrainment can be inhibited, consequently, the acceleration of wall jet flow is reduced and the heat transfer rate decreases.

Experimental Study on Combustion Noise Characteristics in Turbulent Jet Diffusion Flames (난류 제트확산화염의 연소소음 특성에 관한 실험연구)

  • 김호석;오상헌
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1253-1263
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    • 1994
  • The experimental study is carried out to identify the combustion generated noise mechanism in free turbulent jet diffusion flames. Axial mean fluctuating velocities in cold and reacting flow fields were measured using hot-wire anemometer and LDv.The overall sound pressure level and their spectral distribution in far field with and without combustion were also measured in an anechoic chamber. The axial mean velocity is 10-25% faster and turbulent intensities are about 10 to 15% smaller near active reacting zone than those in nonreacting flow fields. And sound pressure level is about 10-20% higher in reacting flow fields. It is also shown that the spectra of the combustion noise has lower frequency characteristics over a broadband spectrum. These results indicate that the combustion noise characteristics in jet diffusion flames are dominated by energy containing large scale eddies and the combusting flow field itself. Scaling laws correlating the gas velocity and heat of combustion show that the acoustic power of the combustion noise is linearly proportional to the 3.8th power of the mean axial velocity rather than 8th power in nonreacting flow fields, and the SPL increases linearly with logarithmic 1/2th power of the heat of combustion.

Design of Unlike Split Triplet Impinging Element for Jet Mixing (혼합성능 개선을 위한 분리 삼중충돌 요소의 설계)

  • 조용호;김경호;윤웅섭
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.225-232
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    • 2003
  • With an aim placed on its exploitation on practical injector design, liquid phase mixing due to unlike split triplet impinging element is experimentally investigated by a series of cold tests. Non-reacting kerosene/water spray simulates the kerosene/LOX propellant combination. Measurements of local mixture ratio distribution were made for different injection configurations and different momentum ratios. Mixing and mixing controlled characteristic velocity efficiencies are measured in terms of oxidizer/fuel jet momentum ratio from 0.5 to 8. Extent of mixing and its influence on hot performance are estimated in terms of mixing efficiency and mixing controlled characteristic velocity. Envelope of design locus for optimum mixing quality and corresponding maximum hot performance are proposed. Effects of momentum ratio, orifice diameter ratio and jet velocity ratios are also presented and discussed.

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A Study of the Thickness Characteristics of the Liquid Sheet Formed by an Impinging Jet onto a Plate (평판 충돌 제트로 생성되는 액막의 두께 분포 특성 연구)

  • Kim, M.S.;Oh, J.H.;Jeong, H.M.;Kang, B.S.
    • Journal of ILASS-Korea
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    • v.27 no.2
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    • pp.77-83
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    • 2022
  • In this study, the thickness of the liquid sheet formed by a low speed impinging jet onto a flat plate was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The measurement results were compared with the theoretical predictions. The wavy surface was observed in the case of low viscosity water, but not in the high viscosity aqueous glycerol solutions. The sheet thickness increased as the circumferential angle increased or the distance from the impinging point increased, but the thickness decreased as the circumferential angle increased around the impinging point. As the jet speed increased, the sheet thickness decreased, and the sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions showed that the measurement results agreed well in the case of low viscosity water or high viscosity liquids around the impinging point. The distribution characteristics of the sheet thickness can provide useful means for prediction of spray characteristics in splash plate injectors.

Flame Structure of Moderately Turbulent Combustion in the Opposed Impinging Jet Combustor (대향분출화염의 분산화학반응 화염구조와 NOx 저감기구)

  • 손민호;조용진;윤영빈;이창진
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.10
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    • pp.1387-1393
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    • 2002
  • The measurement of velocity and stain rate field has been conducted in opposed impinging jet combustion. When a smaller diameter (5mm) orifice of pre-chamber was used, previous studies had reported that the combustion phase showed a shift from weak turbulent combustion to moderate turbulent combustion in the modified Borghi Diagram. In the case with smaller orifice diameter (5mm), NOx emission was substantially reduced by a factor 1/2 while the combustion pressure remains at the same as that in the conventional combustion. Hence, in this study, the experiment setup using PIV technique was designed to identify the relation of the strain rate distribution and NOx reduction associated with moderate turbulent combustion. As a result, it was found that the highly strained pockets are widely distributed during the combustion in the middle of chamber when the orifice diameter is 5mm. And the corresponding PDF distribution of strain rates she was the smoothly distributed strain .ate within the range of |$\pm$1000| (1/sec) rather than a spike shape about zero point. This is the unique feature observed in the combustion with 5mm orifice diameter. Therefore, it can be concluded that the substantial NOx reduction in opposed impinging combustor is mainly attributed to the strain rate distribution within the range of |$\pm$1000|resulting in the combustion phase shift to moderate turbulent combustion.

Optimization of Blade Profile of a Plenum Fan

  • Wu, Lin;Dou, Hua-Shu;Wei, Yikun;Chen, Yongning;Cao, Wenbin;Ying, Cunlie
    • International Journal of Fluid Machinery and Systems
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    • v.9 no.1
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    • pp.95-106
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    • 2016
  • A method of optimization design for the blade profile of a centrifugal impeller by controlling velocity distribution is presented, and a plenum fan is successfully designed. This method is based on the inner flow calculation inside the centrifugal impeller, and is related to the distribution of relative velocity. The results show that after optimization, the boundary layer separation on the suction surface has been inhibited and the stability of plenum fan is improved. The flow at the impeller outlet is also studied, and the jet-wake pattern at the impeller outlet is improved obviously by optimization. The calculation result shows that the static pressure and static pressure efficiency can be increased by 15.4% and 21.4% respectively.