• 한국안전학회지
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• 제8권3호
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• pp.19-25
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• 1993

This paper deals with the experimental study of the turbulent characteristics in the swirling coaxial Jets. In this research, the experimental study has been carried out to investigate the effects of swirl number and equivalence ratio on the flow characteristics in nonreacting flow field of the model combustor which symplifys the continuous type combustor for the practical use. Author particularly Intends to find out the fuel-air mixing In the recirculation zone In order to make sure the effects of swirl number and equivalence ratio on the stabilization of flame.

• 대한기계학회논문집
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• 제7권3호
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• pp.278-285
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• 1983

The momentum transfer in axisymmetric turbulent boundary layer over a rotating cone submerged in a free stream was studied by experiments and numerical analysis. In numerical analysis the velocity profiles were calculated by finite difference method using Prandtl mixing length concept, and the results were compared with experimental results. The agreement was good. By the numerical analysis the wall fircition coefficient was increased as the Reynolds number increased when the rotational speed is large, but the wall friction coefficient was decreased as the rotational speed increased.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.134-139
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• 2002

This study is focused on investigating the characteristics of internal flow of the polymer reactor and its effect on the polymer quality. Four types of polymer reactor which have different kind of impeller, baffle and operation condition were calculated by CFD. Fluent 6 have been used to simulate mixing phenomena of reactor. According to the comparison of computational results and SEM photographs of polymer particle, distribution of turbulent dissipation rate greatly influences on the quality of polymer. So, distribution of turbulent dissipation rate to be important criterion to predict polymer quality.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.120-127
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• 2000

This study is concerned with evaluating the effects of acoustic excitation on the development of two stream mixing layer generated by split plate. The ratios of two velocities U1 and U2 either side of the splitter plate were such that $U_1/U_2$=1.0 (uniform flow) or $U_1/U_2$<1.0(shear flow). The mixing layers were disturbed acoustically through the edge of split plate. Quantitative data were obtained with hot-wire anemometry. Flow visualization with smoke-wire was also employed for qualitative study. the results show that the large scale structures of mixing layers are strongly affected by excitation frequency and amplitude in both uniform and shear flows. The maximum streamwise and vertical turbulent intensities of the excited flow fields are apt to be decreased as compared with those of without excitation. The flow characteristics of uniform flow are more influenced by acoustic excitation than those of shear flow.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.111-116
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• 2004

An experiment was carried out to confirm the validity of time series evaluation of supersonic mixing condition by using catalytic reaction on a platinum wire. Geseous hydrogen was injected parallel to supersonic freestream (M$\infty$ $\approx$ 1.81) from a slit injector, which was located at backward facing step. Time series condition of supersonic mixing was evaluated by using W-type probe which has a platinum wire and reference wire (nickel wire). The evaluation was by simultaneously measuring each electric circuit which kept the temperature of wire constant. Investigations were also conducted for helium, air and no secondary injectant cases to compare with the hydrogen injectant case. The results indicated that it was possible to measure the time series behavior of air and hydrogen supersonic mixing layer or coherent motion of turbulence by using this evaluation.

• 대한기계학회논문집
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• 제8권5호
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• pp.442-449
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• 1984

본 연구에서는 두 분류가 교우되어 배합이 이루어지는 유동역에서 3차원 방향 에 대하여 평균속도분포, 난류강도분포, 난류전단응력분포, 상관계수의 분포 및 난류 운동에너지와 운동량의 변화 등을 측정 분석하였다.

• Journal of the Korean Wood Science and Technology
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• 제26권1호
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• pp.76-86
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• 1998

Effects of processing variables and MAPP (maleic anhydride polypropylene) coupling agent on the properties of composite were discussed for turbulent-air-mixed woodfiber-polypropylenefiber composites. In this research, density, composition ratio, and mat moisture content were established as processing variables, and emulsified MAPP prepared by direct pressure method was incorporated as the coupling agent. And the turbulent air mixer, which was improved in function through alteration of our previous fiber mixer, was used to mix wood fibers and polypropylene fibers. At the addition level of 1% MAPP, based on oven-dried wood fiber weight, woodfiber-polypropylenefiber composites generally showed enhanced the physical and mechanical properties. And composites with low to medium densities of 0.6 to 0.8g/$cm^3$ greatly increased in these property values than with high densities of 1.0g/$cm^3$ or more by adding 1 % MAPP. Thus, MAPP addition was thought to be an effective way of enhancing properties for nonwoven web composites. At the mat moisture contents of 5 to 20%, however, the physical and mechanical properties were not enhanced by adding 1% MAPP. In the composites containing 15% polypropylene fibers, the lowest thickness swelling and water absorption values were observed at the 1% MAPP level. The addition of more than 1% MAPP had the adverse effect on the physical and mechanical properties of composites.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.76-84
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• 2000

A numerical study was conducted for the investigation of thermal choking process in a model scramjet engine based on the experimental results at the Australian National University. The results of numerical simulation showed that thermal choking process could be related to the interaction between hypersonic flow and fuel-air mixing process. Especially, we could make sure that turbulent mixing was most important parameter to the thermal choking process.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.268-269
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• 2003

The Boltzmann kinetic equation is solved directly by means of the conservative splitting method. Underexpanded supersonic free jet flows with small Knudsen numbers are studied. In this numerical simulation features intrinsic to appropriate experiments are observed. Streamwise vortices in a mixing layer and chaotic downstream temporal-spatial fluctuations of microscopic quantities with large amplitude are obtained.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1135-1143
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• 2002

The intermittent spray characteristics of the single-hole diesel nozzle (d$\sub$n/=0.32 mm) used in the fuel injection system of heavy-duty diesel engines were experimentally investigated. The mean velocity and turbulent characteristics of the diesel spray injected intermittently into the still ambient were measured by using a 2-D PDPA (phase Doppler particle analyzer) . The gradient of spray half-width linearly increased with time from the start of injection, and it approximated to 0.04 at the end of the injection. The axial mean velocity of the fuel spray measured along the radial direction was similar to that of the free air jet within R/b= 1.0-1.5 regardless of elapsing time, and its non-dimensional distribution corresponds to the theoretical velocity distributions suggested by Hinze in the downstream of the spray flow fields. The turbulent intensity of the axial velocity components measured along the radial direction represented the 20-30% of the U$\sub$cι/ and tended to decrease in the outer region. The turbulent intensity in the trailing edge was higher than that in the leading edge.