• 한국자동차공학회논문집
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• 제14권2호
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• pp.100-106
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• 2006

The behavior of spray impinging on the inclined constant temperature flat plate was experimentally investigated. To clarify the wall effect of a high pressure DISI injector, a relative angle of the inclined wall to a spray axis was varied. Spray penetration along the wall was observed optically and it was compared with that of a Fan spray type and Swirl type spray. To evaluate various spray motion quantitatively, a spray path penetration which describe the development of a spray tip along the wall was newly introduced. To observe the structure of an impinging spray, it was visualized by a controlled stroboscope light and its visualized image was captured on an CCD camera. Using the digital image of impinging spray $H_x$ and $R_x$ was extracted to clarify the structure of impinging spray. The main parameter of the relative position of the wall was the inclined angle which was defined as the angle was varied from $0^{\circ}$ (vertical impingement) to $60^{\circ}$ at the same condition.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.30-37
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• 2007

Dimethyl Ether(DME) is an alternative fuel for diesel engine, it is renewable and offers potential reductions in emissions. This work was conducted to figure out the macroscopic behavior and the atomization characteristics of DME using a common-rail injection system. The macroscopic behavior was visualized with the spray visualization system composed of a Nd;YAG laser and an ICCD camera. The atomization characteristics were investigated in terms of axial mean velocity, Sauter mean diameter(SMD) and droplet distributions obtained from a phase Doppler particle analyzer(PDPA) system. In this study, it was revealed that the macroscopic behavior and the atomization characteristics of DME are similar compared with commercial diesel fuel. However, DME fuel has a shorter spray tip penetration and a small SMD due to the effect of evaporation characteristics.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1194-1205
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• 2005

The common-rail injection systems, as a new diesel injection system for passenger car, have more degrees of freedom in controlling both the injection timing and injection rate with the high pressure. In this study, a piezo-driven injector was applied to a high pressure common-rail type fuel injection system for the control capability of the high pressure injector's needle and firstly examined the piezo-electric characteristics of a piezo-driven injector. Also in order to analyze the effect of injector's needle response driven by different driving method on the injection, we investigated the diesel spray characteristics in a constant volume chamber pressurized by nitrogen gas for two injectors, a solenoid-driven injector and a piezo-driven injector, both equipped with the same injection nozzle with sac type and 5-injection hole. The experimental method for spray visualization was based on back-light photography technique by utilizing a high speed framing camera. The macroscopic spray propagation was geometrically measured and characterized in term of the spray tip penetration, spray cone angle and spray tip speed. For the evaluation of the needle response of the above two injectors, we indirectly estimated the needle's behavior with an accelerometer and injection rate measurement employing Bosch's method was conducted. The experimental results show that the spray tip penetrations of piezo­driven injector were longer, on the whole, than that of the solenoid-driven injector. Besides we found that the piezo-driven injector have a higher injection flow rate by a fast needle response and it was possible to control the injection rate slope in piezo-driven injector by altering the induced current.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1744-1749
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• 2003

The purpose of this study is to obtain the information about the development process of GDI spray. To acquire the characteristics of GDI spray, the computational study of hollow cone spray for high-pressure swirl injectors was performed. Several hybrid models using the modified KIVA code have been introduced and compared. WB model and LISA model were used for the primary breakup, and DDB and APTAB models were used for secondary breakup. To compare with the calculated results, the experimental results such as cross-sectional images and SMD distribution were acquired by laser Mie scattering technique and Phase Doppler Analyzer respectively. The results show that LISA+APTAB hybrid model has the best prediction for spray formation process.

• 동력기계공학회지
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• 제9권2호
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• pp.14-18
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• 2005

In this study, the spray characteristics of blended fuels with biodiesel were investigated. The experiments were performed for the effect of mixing ratio and injection pressures on the spray behavior. Conventional diesel fuel and biodiesel fuel and blended fuels were used as test fuels. Through the spray visualization system, composed of a Halogen lamp and High speed camera. The process of spray injection was visualized. Fuel containing biodiesel has different spray pattern on account of the high viscosity and large surface tension. Through this experimental result, we found that, after solenoid driving pulse generates, the increase of injection pressure enables delay time to get shorter, but the increase of mixing ratio makes delay time lengthen.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.617-625
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• 2003

Effects of Injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure. and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details Inside model nozzle and real nozzle were alto investigated both experimentally and numerically. for the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2239-2244
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• 2003

A new stratified charge combustion system has been introduced and developed for GDI engines. Before this new GDI system, the stratified mixture was formed by a high pressure swirl injector. But, the special feature of new system is employed of a thin fan-shaped fuel spray formed by a slit type nozzle. Also, this system has been adopted a shell-shaped piston cavity. We made high pressure gasoline injection system and investigated the fan-shaped spray characteristics such as spray tip penetration, spray angle, SMD and velocities of droplets using PDPA(Phase Doppler Particle Analyzer) system and spray visualization system to obtain the concept of the new design and the fundamental data for the next generation GDI system. The experiment was performed at the injection pressures of 5 and 9MPa under the atmospheric condition.

• 한국분무공학회지
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• 제14권3호
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• pp.117-121
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• 2009

Biodiesel fuel has different spray patterns, because viscosity and surface tension of biodiesel fuel are higher than that of diesel fuel. The diesel combustion is strongly controlled by the fuel spray behavior in combustion chamber. So, it was needed to understand the spay characteristics of non-esterification biodiesel fuel. In this study, the spray characteristics of non-esterification biodiesel fuel was investigated to confirm of an effect of WDP. The characteristics of fuel atomization was analyzed with SMD and span factor through laser diffraction particle analyzer (LDPA), and the process of spray injection was visualized through the visualization system composed of a halogen lamp and high speed camera. It was found that injection delay time and SMD of blended fuel with WDP get shoter and smaller than that of non-esterification biodiesel fuel.

• 한국분무공학회지
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• 제7권3호
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• pp.1-6
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• 2002

In this study numerical and experimental study on the spray atomization characteristics of a GDI injector is performed. To carry out numerical analysis, four hybrid models that are composed of conical sheet disintegration model, LISA model, DDB model, and RT model are used. The experimental results to evaluate the prediction accuracy of hybrid models are obtained by using phase Doppler particle analyzer and spray visualization system. It is shown that the prediction accuracy of hybrid model concerning spray developing process and spray tip penetration is good for all hybrid models, but the hybrid breakup models show different prediction of accuracy in the case of local radial SMD distribution.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1177-1186
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• 2004

In this paper, the spray atomization characteristics of a gasoline direct-injection injector were investigated experimentally and numerically. To visualize the developing spray process, a laser sheet method with a Nd :YAG laser was utilized. The microscopic atomization characteristics such as the droplet size and velocity distribution were also obtained by using a phase Doppler particle analyzer system at the 5 ㎫ of injection pressure. With the experiments, the calculations of spray atomization were conducted by using the KIVA code with the LISA-DDB breakup model. Based on the agreement with the experimental results, the prediction accuracy of LISA-DDB breakup model was investigated in terms of the spray shapes, spray tip penetration, SMD distribution, and axial mean velocity. The results of this study provides the macroscopic and microscopic characteristics of the spray atomization, and prediction accuracy of the LISA-DDB model.