• Journal of Power System Engineering
• /
• v.5 no.1
• /
• pp.21-26
• /
• 2001

This paper represents the turbulent intensity, the turbulent kinetic energy and Reynolds shear stress in the X-Y plane of cone type swirl gas burner measured by using X-probe from the hot-wire anemometer system. The experiment is carried out at flowrate 350 and $450{\ell}/min$ respectively in the test section of subsonic wind tunnel. The turbulent intensity and the turbulent kinetic energy show that the maximum value is formed in the narrow slits distributed radially on the edge of a cone type swirl burner, hence, the combustion reaction is anticipated to occur actively near this region. And the turbulent intensities ${\upsilon}\;and\;{\omega}$ are disappeared faster than the turbulent intensity u due to the inclined flow velocity ejecting from the swirl vanes of a cone type baffle plate of burner. Moreover, the Reynolds shear stress $u{\upsilon}$ is distributed about three times as large as the Reynolds shear stress $u{\omega}$ in the outer region of the cone type gas burner.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.3 s.258
• /
• pp.306-312
• /
• 2007

This paper describes the flow characteristics of circular multiple jet investigated by hot-wire anemometry. The nozzle arrays were classified into two cases; 6- or 7-nozzle located circumferentially in equal interval without or with a central jet. The flow field was measured according to the number of nozzles when the Reynolds number based on the nozzle exit is about $10^4$. Mean velocity, Reynolds shear stress and turbulent kinetic energy were investigated in the downstream of jets. The Tollmien's theory holds for downstream only when a nozzle locates at the center. Jet interaction is influenced due to with or without a center nozzle. In addition, the two-dimensional numerical computation was conducted for 3-nozzle case to obtain the general flow structure near the nozzle exit, which verifies the formation of the recirculation region with captive vortices, that is, the evidence of the interaction between jets.

• Journal of Power System Engineering
• /
• v.4 no.4
• /
• pp.25-31
• /
• 2000

This paper represents the vector fields and three dimensional mean velocities in the X-Y plane of cone type swirl gas burner measured by using X-probe from the hot-wire anemometer system. This experiment is carried out at flowrate 350 and $450{\ell}/min$ respectively in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component is focused in the narrow slits distributed radially on the edge of a cone type swirl burner, for that reason, there is some entrainment of ambient air in the outer region of the burner and the rotational flow can be shown in the inner region of the burner because mean velocity W is distributed about twice as large as mean velocity V due to inclined flow velocity ejecting from the swirl vanes of a cone type baffle plate of burner. Moreover, the mean velocities are largely distributed near the outer region of burner within $X/R{\fallingdotseq}1.5$, hence, the turbulent characteristics are anticipated to be distributed largely in the center of this region due to the large inclination of mean velocity and swirl effect.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.3
• /
• pp.716-724
• /
• 1990

Oblique impinging plane jets were investigated experimentally and numerically at Reynolds number 21000. The inclination angle was varied from 90.deg.(normal to the impinging plate) to 60.deg.. The distance H between the nozzle exit and the stagnation point on the impinging plate was fixed at H/D=8. The working fluid was air. The mean velocity components and turbulent quantities were measured by a hot-wire anemometer. And the static pressure distributions on the impinging plate were measured by a Pitot tube. In numerical computation, the governing partial differential equations of elliptic type were solved with conventional k-.epsilon. turbulence model. The measurements show that, after impingement, the jet half width alone the wall increases in both directions, and that similarity for each turbulent quantity such as Reynolds shear stress or turbulent kinetic energy is revealed in the wall jet region. The computed results show some deviation from experimental data in the impingement region, where streamline curvature is significant. However, the computed results agree qualitatively well with measurements.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.12
• /
• pp.2368-2375
• /
• 1992

The transition of turbulent kinetic energy(TKE) balance along the centerline of the flow unit, which is composed of straight-duct, contraction and free-jet, has been investigated by the hot-wire anemometry. It is found that the mean turbulent kinetic energy is balanced by the dissipation in the internal flow region ; by the production and the dissipation, through contraction ; and by the dissipation, in initial region(X〈8D) of free-jet. But in the developing region (8D〈X〈20D) it is balanced by all of the three(ie, diffusion, production and dissipation). Finally, in the downstream of free-jet, the mean TKE is balanced again by dissipation like as the beginning. The decay-laws along the centerline are checked in the region of free jet as well as in the straightduct. After the developing region of free-jet also exist the decay-laws, the exponent of the axial turbulence being bigger than of the radial.

• Journal of the KSME
• /
• v.23 no.5
• /
• pp.344-348
• /
• 1983

유속의 최초 측정방법은 Torricelli (1608-1647)가 Bernoulli 방정식을 오리피스에 적용하여 유속 계산식 v =k.root.2gh를 유도하였고, 그 이후 역시 Bernoulli 방정식을 이용하여 Henri Pitot (1695-1771)는 정체점에 대한 이론을 고려하여 정체압을 측정하는 방법으로 가는관을 이용하여 Seine 강의 유속을 측정하는데 성공하므로서 이론적인 유속계산식 v =k.root.2gh는 가장 원시적인 피토우관(Pito-tube) 이나 오리피스에 의한 유속계산식이지만, 현재에 아무리 전기적인 정밀측정 방법과 레이저에 의한 측정방법이 개발되어도 결국 피토우관에 의한 측정값이나 압력측정치와의 교정(Calibration)이 선행되지 않으면 안되기 때문에, 피토우관에 의한 측정방법은 가장 원시적 이면서 가장 정확한 측정방법의 하나이다. 다만 피토우관에 의한 측정은 속도장내의 평균속도를 측정하게 되고 난류성분의 해석이 불가능하며, 그 측정이 일차원 유동에 국한된다는 것이 단점 으로 되어 있다. 이러한 점들을 보완할 수 있는 측정장치 들이 많이 개발되고 있으나 본 해설 에서는 공기유동의 경우 우리가 가장 많이 사용하고 있는 열선풍속계에 대하여 그 용법을 논하기 로 한다.

• Journal of Power System Engineering
• /
• v.4 no.2
• /
• pp.17-24
• /
• 2000

직경비가 0.26, 0.39, 그리고 0.56인 경우 거칠기를 내벽면에, 외벽면에, 그리고 양벽면에 각각 설치한 동심환형관에서 완전히 발달된 난류유동에 대한 거칠기 효과를 실험과 이론으로 해석하였다. 그리고 거칠기 효과를 정량적으로 파악하기 위해 양벽면 모두 매끈한 환형관의 경우도 포함하였다. 실험에서 마찰계수를 구하는데 필요한 속도분포와 전단응력들은 피토튜브와 X-형 열선풍속계를 사용하였다. 이론 해석은 수정대수 난류모델을 사용하였고 그 결과를 이론값과 비교하여 아래의 결론을 얻었다. 1) 무디다이어그램 (Moody diagram)은 거칠기가 설치된 이중관에는 적용할 수 없음을 보였다. 2) 경우(c) 와 (d)에서는 반경비가 클수록 반드시 마찰계수가 증가하지 않았다. 3) 4개의 경우중 거칠기로 인해 마찰계수가 증가하는 크기의 순서는 경우(d)가 가장 컸고 경우(a)가 가장 작았다.

• Journal of Power System Engineering
• /
• v.1 no.1
• /
• pp.61-69
• /
• 1997

본 연구는 동심환형관에서 거칠기가 없이 매끈한 경우, 내측벽에 만, 외측벽에 만, 그리고 양측 모두에 거칠기가 있는 4경우에 대해 직경비가 0.26, 0.39, 그리고 0.56일 때 벽면에 설치된 거칠기 위치들이 난류유동장에 미치는 효과를 실험적으로 조사하고자 한다. 최대속도와 전단응력이 0인 지점들, 시간평균속도의 구배들, 그리고 와확산계수들을 X형 열선풍속계와 이중 피토튜브를 사용하여 측정하였다. 본 연구를 통하여 동심환형관에 설치된 거칠기들이 난류유동에 미치는 효과에 대한 정량적자료를 제시할 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.3 no.3
• /
• pp.161-167
• /
• 1991

This paper presents the results of some measurement of the fluctuating velocity field in the turbulent boundary layer disturbed by a triangular prism and discusses the discovery of the disturbed boundary layer. A prism of height 8mm was used for experiments. The streamwise location of the prism was fixed at 1200mm downstream from the leading edge and the space between the prism center and the wall was set at three different values, 6, 15 and 33.5mm. The results show that the near-wall region of the disturbed boundary layer recovers original state much more quickly than the outer region. In the case h=6mm the recovery is faster than the other cases. Moreover, it was found that peak of fluctuating velocities moves outwards somewhat rapidly with increasing ${\times}$ mainly due to the turbulent diffusion of the fluctuating velocity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.9
• /
• pp.1299-1308
• /
• 2003

This paper is studied to investigate the effect of slits and swirl vanes on the development of turbulent flow fields in gun-type gas burner with a cone type baffle plate because this gas burner is generally composed of eight slits and swirl vanes. All of turbulent characteristics including mean velocities were measured in the horizontal plane and cross section by using X-type hot-wire probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 l/min in the test section of subsonic wind tunnel. Slits cause the fast jets, and then they have the characteristic that the flow is not adequately spread to radial direction and has long flow length and very small flow velocity distribution in the central part. On the contrary, swirl vanes does not have long enough for adequate flow length to downstream because the rotational flow diffuses remarkably to radial direction. However, the suitable arrangement between slits and swirl vanes causes effective flow width and flow length, and then it promotes fast flow mixing over the entire region including central part to increase turbulence more largely and effectively. Therefore, it is thought as a very desirable design method in gun-type gas burner to locate slits on the outside of swirl vanes.