• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.105-110
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• 2006

Many previous works have been performed to provide correlations of flame length, theoretically and experimentally. Most of these results studied were conducted in vertical turbulent flame with no coaxial air condition. The present study analyzes the flame length scaling with coaxial air. In turbulent hydrogen non-premixed jet flames with coaxial air, flame length scaling theoretically proposed so far has been related with the concept of a far-field equivalent source. At high coaxial air to fuel velocity ratio, $U_A/U_F$, however, this scaling theory has some difference with experimental flame length data. This difference is understood to be due to the fact that the theory is based on far-field notion, while the effect of coaxial air on jet flame occurs in the region near the nozzle exit. Therefore, we define effective jet density $P_{eff}$ involving the concept of near-field so that effective jet diameter can be extended to the near-field region. In this condition, we modify the correlation and compare with experimental data.

• 한국환경과학회지
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• 제32권8호
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• pp.555-561
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• 2023

A study is to predict the effective pulsing distance following to the pulsing pressure, nozzle diameter, filtration velocity using numercial analysis techniques and use it as an efficient operation condition and economic data for on-line type pulse air jet bag filter. Filtration area 6 m² condition, calculate filter resistance coefficient for simulation through the primary experiments using coke dust. For CFD simulation, analysis pulsing characteristics about nozzle diameter, filtration velocity and pulsing pressure. The maximum pulsing length of on-line type pulse air jet bag filter, in 10mm nozzle, filtration velocity 1.5m/min and pulsing pressure 5 bar conditions, is 2,285 mm, maximum length is 76.2% of the total filter bag, which is sufficient to pulsing. In 12mm nozzle, pulsing pressure 5 bar and filtration area 1.22 m² conditions, the maximum pulsing length of on-line type pulse air jet bag filter is 1,744~2,952 mm, and the maximum length is 2,952 mm indicates pulsing air can be reached to the bottom of filter bag. When the nozzle diameter is increased 8mm to 10mm, maximum pulsing length is extended 40~47%, and increased 10mm to 12 mm, maximum pulsing length is extended 10~17%. For effective pulsing, over the 5bar of pulsing pressure and larger than 10 mm of nozzle diameter are required.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.242-245
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• 2009

희석된 동축공기 수소 난류확산화염에서 연료의 구성이 화염 길이에 미치는 영향에 대한 연구를 수행하였다. 화염의 길이는 동축공기와 연료 제트의 속도비의 함수로 표현하였고, 이론적 예측과 비교하였다. 네 조건의 연료 구성에 대해 연구를 수행하였다. 동축공기 제트 화염의 길이 예측을 위해 near-field concept에서의 유효 직경을 이용한 스케일링 관계식을 유도하였다. 실험 결과 가시 화염의 길이는 이론적 예측과 크게 일치하였다. 여러 연료 조건에서의 희석된 수소 제트의 화염에서도 스케일링 분석은 유효하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3150-3155
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• 2007

This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.

• 한국분무공학회지
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• 제11권4호
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• pp.220-227
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• 2006

Experimental studies has been conducted to investigate the effect of orifice diameter ratio on the mixing characteristics of the split element of doublet and triplet elements. The spray characteristics of non-reacting immiscible liquids have been investigated using a patternator. The local volume fraction is measured by use of mean value of each component. This volume measurement represents the mixing characteristics of the liquid, which affect the overall combustion efficiency. The ratio of the orifice diameter, ranging from 1 to 1.5, and that of the jet-momentum, ranging from 0.5 to 6.0, we used. The jet impinging behavior with use of various ratios exhibits substantially different mixing characteristics. Mixing efficiency is maximized when the jet-momentum ratio is increased; this behavior is particularly prominent when the orifice diameter ratio is greater than unity. The split of the triplet element yields better mixing characteristics and is more effective than that of the doublet element in regard to achieving high combustion efficiency. The optimum mixing factor for the triplet element is found to be 0.75, according to our measurement.

• 설비공학논문집
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• 제10권5호
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• pp.509-522
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• 1998

An experimental investigation is reported on the heat transfer coefficient from a rotating flat plate in a round turbulent normally impinging water jet. Tests were conducted over a range of jet flow rates, rotational speeds, jet radial posetions with various combinations of three jet nozzle diameter. Dimensionless correlation of average Nusselt number for laminar and turbulent flow is given in terms of jet and rotational Reynolds numbers, dimensionless jet radial position. We suggested various effective promotion methods according to heat transfer characteristics and aspects. The data presented herein will serve as a first step toward providing the information necessary to optimize in rational manner the cooling requirement of impingement cooled rotating machine components.

• 한국항공우주학회지
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• 제30권5호
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• pp.71-78
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• 2002

동축공기 수소확산 화염에서 세 가지 동축공기 조건과 화염의 유무에 따라 실험조건을 분류하고, 이에 대해 PIV를 이용하여 실험을 수행하였다. PIV를 통해 얻은 속도장을 이용하여 평균속도, 난류강도, Reynolds stress 등을 구하여 유동장을 분석하였다. 우선 단순제트에 대해 상사성을 살펴본 결과 이전의 다른 연구자의 실험결과와 일치하였다. 동축공기가 있는 경우 중심축 속도 감쇠는 $x^{-1}$에 비례하여 감소하는 것을 확인하였다. 축방향 길이를 유효밀도에 의해 정의된 유효 제트 지름으로 무차원화한 값으로 중심축 속도를 도시한 결과 하나의 선분에 떨어지는 것을 확인하였다. 평균속도 분포를 살펴보면 일정한 연료유량에 동축공기 유량을 증가시킨 경우 동축공기가 증가함에 따라 속도 분포의 형태가 바뀌게 되어 자기상사성이 유지되지 않는 것으로 보인다. 난류강도는 평균속도 분포의 경우보다 후류에서 자기상사성이 나타난다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.259-261
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• 2012

The effect of fuel composition and coaxial air on the nitrogen oxide emission index was studied in a non-premixed turbulent jet flame. Validity of experimental setup and methodology is checked. The NOx emission trend is similar with previous works in hydrogen flame, but it's not well in $H_2/CO$ flame. Normalized EINOx scaling with modified $S_G$ applying near-field concept was conducted. Experimental data don't collapse single correlation curve, but partially same trend is observed in all cases.

• 한국환경과학회지
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• 제32권11호
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• pp.801-809
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• 2023

The purpose of this study is to predict the reflection distance following to the pulsing pressure, total air supplying, filter bag size using numercial analysis techniques and use it as an efficient operation condition and economic data for off-line type pulse air jet bag filter. In this research, filtration area 6 m² condition, calculate filter resistance coefficient for simulation through the main experiments using coke dust. Ansys fluent V19.0 apply to CFD simulation, and analysis pulsing characteristics about pulsing pressure, filtration velocity and nozzle diameter. The maximum reflecting distance of off-line type pulse air jet bag filter is 1,000 mm regardless of total air supplying at over the 42 L/m² conditions, that indicates off-line type can extend filter bag length 1,000 mm than on-line type. In order to effective primary and secondary pulsing of off-line type pulse air jet bag filter, over the 5 bar of pulsing pressure and over the 42 L/m² of total air supplying are needed.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1156-1162
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• 2005

In this study, a noble method is proposed to prevent the edge overcoating (EOC) that may develop near the edge of the steel strip in the gas wiping process of continuous hot-dip galvanizing. In our past study (Trans. of the KSME (B), Vol. 27, No. 8, pp. $1105\~1113$), it was found that EOC is caused by the alternating vortices which are generated by the collision of two opposed jets in the region outside the steel strip. When the two opposed jets collide at an angle much less than $180^{o}$, non-alternating stable vortices are established symmetrically outside the steel strip, which lead to nearly uniform pressure on the strip surface. In order to deflect both jets downward by a certain angle, a cylinder with small diameter is installed tangentially to the exit of the lower lip of the two-dimensional jet. In order to find an optimum cylinder diameter, the three dimensional flow field is analysed numerically by using the commercial code, STAR-CD. And the coating thickness is calculated by using an integral analysis method to solve the boundary layer momentum equation. In order to compare the present noble method with the conventional baffle plate method to prevent the EOC, the flow field with a baffle plate is also calculated. The calculation results show that the tangentially installed cylinder at the bottom lip of the jet exit is more effective than the baffle plate to prevent EOC.