• Journal of ILASS-Korea
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• v.12 no.1
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• pp.1-10
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• 2007

The low frequency combustion instability phenomena generated by pressure drop oscillation such as propellant shake in feed line are studied. To generate the flowrate oscillation by the pressure pulsation up to 400Hz without flow discontinuities and cavitations, a hydrodynamic mechanical pulsator of rotating disk type was produced. Injection pressure conditions are 5, 7 and 9 bar and pressure fluctuation frequency conditions are 0, 4, 6 and 8 Hz. When the injection pressure was oscillated by a mechanical pulsator, the spray shape was pulsated regularly. During the pulsated state of the spray with a mechanical pulsator, the spray characteristics, such as spray angle and liquid film thickness in orifice exit, were measured and compared with those in steady state without a mechanical pulsator. Though the mean injection pressure was fixed in the steady and fluctuating state, there were some differences in all measured values, i.e. liquid film thickness and spray cone angle, between both states.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.152-160
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• 2004

Studies to investigate the influence on hydraulic acoustic wave were conducted using pressure swirl atomizer under making frequency range from 0 to 60Hz using water as a propellant. Pressure oscillation from hydraulic sources gives a strong influences on atomization and mixing processes. The ability to drive these low frequency pressure oscillations makes spray characteristics changeable. The effect of pressure perturbation and its spray characteristics showed that low injector pressure with pressure pulsation gives more significantly than high injector pressure with pressure perturbation in SMD, spray cone angle, breakup length. Moreover, this data could be used for prediction of low combustion instability getting G factor.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.1
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• pp.33-39
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• 2010

The film boiling heat transfer was experimentally investigated for the water sprays impacting on an inclined hot surface. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made for different inclination angles of $\theta=0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$. The experimental results show that, in the downstream region of the inclined hot surface, increasing the inclination angle increases the local heat flux slowly because of increasing the number of rebound droplets. However, the inclination angle of heat transfer surface had no remarkable effect on the local heat flux of spray cooling under the present test conditions.

• Journal of ILASS-Korea
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• v.2 no.1
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• pp.46-51
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• 1997

In this study, spray characteristics of the pressure swirl atomizer have teen investigated. Four atomizers with the different orifice diameter and five tangential ports with the different inlet number were fabricated. For the purpose of the measurement of the mean drop sine, Malvern particle sizer was used. And also discharge coefficient was measured and spray cone angle was measured by using shadow graphy method. As a result when the injection pressure was increased, mean drop size was decreased. And the dominant factor which influence on the spray characteristics of pressure swirl atomizer was orifice diameter.

• Journal of ILASS-Korea
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• v.14 no.2
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• pp.71-76
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• 2009

The aim of this investigation is to study the effect of the high injection pressure on the dimethyl ether (DME) spray characteristics injected through a common-rail diesel injector under various ambient pressures. In order to investigate the effect of the injection pressure and ambient condition, the common-rail injection system with two high pressure pumps and high pressure chamber pressurized up to 40 bar were used, respectively. Spray images of DME fuel obtained from a visualization system composed of high speed camera and two metal halide lamps as the light source. From the obtained images, the spray behaviors such as a spray development process, spray tip penetration, spray width, and spray cone angle were measured for analyzing the DME spray characteristics under various experimental conditions. It was found that the spray development slowed as the ambient pressure increased and spray tip penetration at injection pressure of 90 MPa is longer than that at 50 MPa. In addition, the spray width at the end stage of injection decreased under the atmospheric conditions due to the evaporation property of DME fuel, and DME spray shows narrow spray cone angle according to the injection pressure increased.

• Journal of the Korean Society of Visualization
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• v.3 no.2
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• pp.3-13
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• 2005

The optical patterantor provides the high resolution and quantitative information of the spray. Fuel distribution and Sauter Mean Diameter (SMD) can be measured from fluorescence and Mie-scat-tering images. To correct the attenuation of the laser beam and signal in dense spray region, the method to find the geometric mean of the signal intensities obtained from two cameras was evaluated and verified in a solid-cone spray. In high pressure environment, the increased number density of the droplets cause multiple scattering. The optical patternation technique using a laser beam instead of a laser sheet was applied to minimize the multiple scattering problem. The pattern of a coaxial spray was changed from hollow-cone to solid-cone shape, and the spray angle was reduced as the ambient pressure increased from 0.1 to 4.0 MPa.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.31-37
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• 2010

The aim of this work is to investigate the spray and combustion characteristics of dimethyl-ether (DME) at various injection conditions. The spray characteristics such as spray tip penetration and spray cone angle were experimentally studied from the spray images which obtained from the spray visualization system. Combustion and emissions characteristics were numerically investigated by using KIVA-3V code coupled with Chemkin chemistry solver. From these results, it revealed that DME spray had a shorter spray tip penetration and wider spray cone angle than that of diesel spray due to the low density, low surface tension, and fast evaporation characteristics. At the constant heating value condition, DME fuel showed higher peak combustion pressure and earlier ignition timing, because of high cetane number and superior evaporation characteristics. In addition, the combustion of DME exhausted more $NO_x$ emission and lower HC emission due to the active combustion reaction in the combustion chamber. The result shows that DME had a little soot emission due to its molecular structure characteristics with no direct connection between carbons.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.251-255
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• 2005

By using liquid film thickness measurement the spray characteristics of swirl injector according to the geometric parameters were investigated in this paper. A specially designed injector having a variable backhole length, swirl chamber length, orifice length was used to measure the liquid film thickness. The spray characteristics of the injector were represented by mass flow rate according to the injection pressure, liquid film thickness in the lower orifice, spray cone angle.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.17-24
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• 2010

The objective of this work is to analyze the macroscopic behavior of spray and injection characteristics on the DME blended biodiesel at different mixing ratios by using spray visualization and injection rate measurement system. The spray images were analyzed to a spray tip penetration, a spray cone angle and a spray area distribution at various mixing ratio of DME by weight. The influence of different injection pressure and ambient pressure on the fuel spray characteristics are investigated for the various injection parameters. In order to analyze the injection characteristics of test fuels, the fuel injection rate is measured at various blending ratio. The variation of viscosity of the blended fuel by the mixing of DME fuel shows the improved effect of spray developments. Also, it was found that the injection quantities of high blended ratio were larger than that of lower blended fuel. Also, higher blending fuel showed a faster evaporation than that of mixing ratio of test fuel because kinetic viscosity was changed by blending ratio.

• Journal of ILASS-Korea
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• v.7 no.4
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• pp.1-8
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• 2002

This paper investigates the spray angle and the outline shape of the liquid sheet discharged from a simplex swirl nozzle. A theoretical model was proposed and the corresponding experimental data were presented for comparison. Axial and tangential velocities and thickness of the liquid sheet at the nozzle exit were also predicted. The liquid sheet thickness at nozzle exit, as well as the discharge coefficient, turned out to be a sole function of the swirl Reynolds number. However, the axial and tangential velocities at nozzle exit and the spray angle could not be expressed only with the swirl Reynolds number. The predicted outline shape and spray angle of the liquid sheet agreed reasonably with the measured data.