• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.915-920
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• 2001

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston bowl shapes(F, B, and R-type) in a optically accessible engine. The images of liquid and vapor phases were captured in the motoring engine using exciplex fluorescence method. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure is 5.1MPa. Two dimensional spray fluorescence image of vapor phases was acquired to analyze spray behaviors and fuel distribution inside of cylinder. Four injection timings were set at BTDC $90^{\circ},\;80^{\circ},\;70^{\circ},\;and\;60^{\circ}$. With a fuel injection timing of BTDC $90^{\circ}$, fuel-rich mixture level in the center region was highest in a B-type piston. With a fuel injection timing of BTDC $60^{\circ}$, R-type piston was best. R-type piston shape was suitable under enhanced swirl ratio and late injection condition and B-type piston shape was right in a weak swirl ratio. It was found that the piston bowl shape affected the mixture stratification inside of cylinder.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.166-173
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• 2006

This study investigates a heavy duty diesel engine with swept vol. 12.6L, 4cycle-OHC type to verify the effects of the performance and exhaust gas emission according to the variable specifications of both swirl ratio and flow coefficient in inlet port, combustion bowl and fuel injection system. To meet the high BMEP and stringent exhaust emission standard, a turbocharger with wastegate and an intercooler were installed in the engine. Helical port, major design parameters for combustion chamber and electronic fuel injection pump with 1,000bar were reviewed and applied. Confirmation tests were also performed to meet the target value, $NO_x$ 5.0g/kWh and PM 0.1g/kWh of Euro3 exhaust emission legislation. The results of this study show that not only is it effective to use a relatively bigger bowl size for controlling rapid burning condition due to the decreased in-bowl swirl, but also to use a concave cam with double injection rates to decrease $NO_x$.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1132-1140
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• 1998

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.37-43
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• 2003

The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I. diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure. Soot distribution in diffusion flame according to swirl ratio, injection pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.395-406
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• 2005

Important characteristics of swirl sprays intersected by a strongly convective gaseous cross flows were experimentally investigated. The breakup processes due to different Weber and Reynolds numbers of liquid and gas streams were visually examined with quantitative measurements of breakup lengths, penetration heights, and droplet sizes. Snapshot images and spray data evidenced that, at lower jet Reynolds number the breakup processes portrays the atomization profiles similar to typical column breakup of single orifice jet. At higher jet Reynolds numbers, disintegration of jet stream is significantly expedited by strong momentum transported from strongly convective gaseous stream. The breakup length and penetration height decreased as the convective flow increase. From the bottom the wall up, the SMD measured the centerline first increases and then decreases before again increasing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.686-691
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• 2000

The flat flame made by swirling air has lots of the different characteristics according to the swirl numbers in the burner throat. Its combustion characteristics are also affected by them. In this study, the flow patterns in the flat flame burner which is no firing condition were investigated experimentally with using smoke in terms of each swirl number. Also the blow off, flame structure, temperature distribution and NO emission in the firing condition were measured at the atmosphere and combustion furnace.

• 설비공학논문집
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• 제12권7호
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• pp.667-673
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• 2000

In order to understand the laminar flow heat transfer enhancement by the swirl flow, the effects of heat transfer in a circular pipe with a twisted tape insert were investigated experimentally. In the present study, the uniform heat flux condition was considered. The laminar heat transfer correlations were developed using the least-square-fit from the surface temperature distribution of an electrically-heated pipe and flow property data. Average Nusselt number correlations with the twisted tape insert were expressed as a function of swirl parameter, Reynolds number and Prandtl number. In the case of the twisted ratio y = 6.05, the mean Nusselt number increased approximately 500% and the friction factor increased approximately 300%, compared to the case of the empty pipe, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권2호
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• pp.36-43
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• 2001

In order to understand the laminar heat transfer enhancement by swirl flow, the effects of heat transfer in a circular pipe with twisted inserts are investigated experimentally. In the present study, a uniform heat flux condition is considered. Laminar heat transfer correlations are developed using least square fit method from surface temperature distributions of an electrically-heated pipe and flow properties. Average Nusselt number correlations with twisted inserts are expressed as a function of swirl parameter, Reynolds number and prand시 number. When the twisted ratio is 6.50, mean Nusselt number and friction factor increase by approximately 500% and 300%, respectively, compared with the values for a pipe without inserts.

• 한국가시화정보학회지
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• 제19권1호
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• pp.43-49
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• 2021

In this experimental study, measurement techniques such as backlight imaging, optical patternator, and laser sheet drop sizing were applied to characterize open-type swirl injector used in Russian liquid rocket engine, RD 107. The typical development of swirl spray was observed in backlight images. The breakup length was measured by using the ratio between Mie scattering and fluorescence signal. Relative Sauter Mean Diameter was measured by using laser sheet drop sizing and the possible source of errors were discussed.

• 한국분무공학회지
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• 제23권4호
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• pp.159-168
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• 2018

Thrust throttling in a liquid rocket engine can be implemented via several ways such as high pressure drop injector, dual manifold, multiple chamber, pintle injector, and gas injection. Thrust throttling using gas injection controls thrust by usually injecting inert gas into propellant through an aerator to reduce the propellant's bulk density. In this study, the outside-in aerator was used in the propellant line to create two phase flow. Closed-type, open-type, and screw-type bi-swirl coaxial injectors were utilized for investigating throttling characteristics such as pressure drop, mixture density, and discharge coefficient according to gas-liquid mass ratio.