• 제목, 요약, 키워드: Supersonic Flow

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Transitional Behavior of a Supersonic Flow in a Two-dimensional Diffuser

  • Kim, Sehoon;Kim, Hyungjun;Sejin Kwon
    • Journal of Mechanical Science and Technology
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    • v.15 no.12
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    • pp.1816-1821
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    • 2001
  • Two-dimensional blow-down type supersonic wind tunnel was designed and built to investigate the transient behavior of the startup of a supersonic flow from rest. The contour of the divergent part of the nozzle was determined by the MOC calculation. The converging part of the nozzle, upstream of fille throat was contoured to make the flow uniform at the throat. The flow characteristics of the steady supersonic condition were visualized using the high-speed schlieren photography. The Mach number was evaluated from the oblique shock wave angle on a sharp wedge with halt angle of 5 degree. The measured Mach number was 2.4 and was slightly less than the value predicted by the design calculation. The initial transient behavior of the nozzle was recorded by a high-speed digital video camera with schlieren technique. The measured transition time from standstill to a steady supersonic flow was estimated by analyzing the serial images. Typical transition time was approximately 0.1sec.

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Numerical study on the effects of nozzle geometry and substrate location in the supersonic flow (노즐 형상과 기판의 위치 변화가 초음속 유동에 미치는 영향에 관한 수치해석 연구)

  • Park, Jung Jae;Yoon, Suk Goo;Kim, Ho Young
    • 한국신재생에너지학회:학술대회논문집
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    • pp.58.2-58.2
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    • 2010
  • This paper deals with the simulation of solid particle coating technology via supersonic nozzle in vacuum environment to devote as an aerosol-deposition device. In order to improve efficiencies of nozzle and coating process, effects of shockwave, nozzle geometry, and substrate location were studied computationally under a fixed chamber pressure of 0.01316 bar which is nearly vacuous. Shockwave is the important factor affect to entire flow because shockwave in the jet flow dissipates the kinetic energy of the flow in the supersonic condition. Results show that various nozzle geometries have significant effect on the supersonic flow and we know that the supersonic nozzle should be optimized to minimize the loss of the flow. Another parameter, the distance between substrate and nozzle tip, shows little effect in this study.

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Study of Starting Pressure of a Supersonic Ejector with a Second-Throat (이차목을 갖는 초음속 이젝터 작동압력에 대한 연구)

  • Jin, Jung-Kun;Kwon, Se-Jin;Kim, Se-Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.8
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    • pp.934-939
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    • 2005
  • Starting pressure of a supersonic ejector with a second-throat was investigated. In case of mixing chamber length longer than a critical length, starting pressure is in proportion to length of the mixing chamber. In this study, we assumed that the ejector starts when the primary supersonic flow reaches inlet of the second-throat and the distance of the supersonic flow traveling can be expressed by multiplying an empirical factor to the first diamond shock length of overexpanded flow. To calculate the overexpanded supersonic flow, a mixing model was employed to compute secondary flow pressure and the result was applied to back pressure condition of overexpanded flow calculation. In the result, for three cases of primary nozzle area ratio, we could get accurate model of predicting the starting pressure by selecting a suitable empirical factors around 3.

EXPERIMENTAL AND COMPUTATIONAL STUDIES ON HYSTERISYS PHENOMENON OF SUPERSONIC COANDA WALL JETS

  • Kim, Heuy-Dong;Kweon, Oh-Sik;Setoguchi, Toshiaki
    • Proceedings of the KSME Conference
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    • pp.514-519
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    • 2000
  • Recently a considerable interest is being concentrated on industrial applications of supersonic Coanda wall jets, but the flow physics are not still understood well. It is of practical importance to evaluate the effectiveness of supersonic Coanda wall jet devices fer such industrial purposes. In the present work, experiments and computations were performed to Set a better understanding of the supersonic Coanda jet physics. The experiments were made using a small blow-down wind tunnel. The operating pressure ratio and the Coanda surface configuration were changed to investigate their influences on the wall jet flows. Two-dimensional Navier-Stokes computations were performed using a TVD finite volume scheme to effectively capture the important wave structures of supersonic Coanda jet flows. Both experimental and computational results showed several important hysterical features of the supersonic Coanda wall jets; the attachment and detachment of supersonic Coanda jet were strongly dependent on the change processes of the operating pressure ratio and the detailed flow configuration.

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Transient Shock Waves in Supersonic Internal Flow

  • Suryan, Abhilash;Shin, Choon-Sik;Setoguchi, Toshiaki;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.357-361
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    • 2010
  • When high-pressure gas is exhausted through nozzle exit to the atmosphere, expanded supersonic jet is formed with the Mach disk at a specific condition. In two-dimensional supersonic jets, the hysteresis phenomenon of the reflected shock waves is found to occur under quasi-steady flow conditions. Transitional pressure ratio between the regular reflection and Mach reflection in the jet is affected by this phenomenon. In the present study, experiments are carried out on internal flow in a supersonic nozzle to clarify the hysteresis phenomena for the shock waves and to discuss its interdependence on the rate of the change of pressure ratio with time. Flow visualization is carried out separately on the straight and divergent channels downstream of the nozzle throat section. The influence that the hysteresis phenomena have on the location of shock wave in a supersonic nozzle is also investigated experimentally.

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An Experimental Study of the Variable Sonic/supersonic Ejector Systems (가변형 음속/초음속 이젝터 시스템에 관한 실험적 연구)

  • Lee Jun Hee;Kim Heuy Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.5
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    • pp.554-560
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    • 2005
  • A new method to improve the efficiency of a hydrogen fuel cell system was introduced by using variable sonic/supersonic ejectors. To obtain the variable area ratio of the nozzle throat to ejector throat which controls the mass flow rate of the suction flow, the ejectors used a movable cylinder inserted into a conventional ejector-diffuser system. Experiments were carried out to understand the flow characteristics inside the variable ejector system. The secondary mass flow rates of subsonic and supersonic ejectors were examined by varying the operating pressure ratio and area ratio. The results showed that the variable sonic/supersonic ejectors could control the recirculation ratio by changing the throat area ratio, and also showed that the recirculation ratio increased fur the variable sonic ejector and decreased for the variable supersonic ejector, as the throat area ratio increases.

An Experimental Study on the Flow Characteristics ofa Supersonic Turbine Cascade as Pressure Ratio

  • Cho, Jong-Jae;Jeong, Soo-In;Kim, Kui-Soon;Lee, Eun-Seok
    • International Journal of Aeronautical and Space Sciences
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    • v.5 no.2
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    • pp.9-17
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    • 2004
  • In this paper, a small supersonic wind tunnel was designed and built to studythe flow characteristics of a supersonic impulse turbine cascade by experiment. Theflow was visualized by means of a single pass Schlieren system. The supersoniccascade with 3-dimensional supersonic nozzle was tested over a wide range ofpressure ratio. Highly complicated flow patterns including shocks, nozzle-cascadeinteraction and shock boundary layer interactions were observed.

An experimental study on the flow characteristics of a supersonic turbine cascade with the leading edge chamfer angle (초음속 터빈의 익렬 앞전 모서리각에 따른 유동 특성에 대한 실험적 연구)

  • Cho Jong-Jae;Kim Kui-Soon;Jeong Eun-Hwan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.361-366
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    • 2006
  • A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The supersonic cascade with a 2-dimensional supersonic nozzle was tested for the leading edge chamfer angle $(\gamma)$ of the supersonic turbine that is the one of the turbine design parameter. Firstly, the flow was visualized by a single pass Schlieren system. Next, total and static pressure of the cascade were measured by a pressure scanning system. Finally, highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

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An experimental study on the expansion loss of a supersonic turbine with the cascade position (익렬 위치에 따른 초음속 터빈의 확산 손실에 대한 실험적 연구)

  • Cho, Jong-Jae;Kim, Kui-Soon;Jeong, Eun-Hwan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.387-392
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    • 2006
  • A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. Experiments are performed to find flow characteristics of supersonic turbine with the cascade positions and to find factor of expansion loss. The supersonic cascade with a 2-dimensional supersonic nozzle was tested with the cascade positions. Firstly, the flow was visualized by Z-type Schlieren system. Finally, highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

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Experimental Study on the Flow Characteristics of Supersonic Turbine with the Axial Gap Ratios (초음속 터빈의 축방향 간격비에 따른 유동 특성에 대한 실험적 연구)

  • Cho, Jong-Jae;Kim, Kui-Soon;Jeong, Eun-Hwan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.2
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    • pp.136-142
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    • 2007
  • A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The supersonic cascade with a 2-dimensional supersonic nozzle was tested for the axial gap ratio (${\delta}$) of the supersonic turbine that is the one of the turbine design parameter. Firstly, the flow was visualized by a single pass Schlieren system. Next, total and static pressure of the cascade were measured by a pressure scanning system. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.