• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.431-438
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• 2023

Recently, study on hydrogen is being conducted due to environmental pollution and fossil fuel depletion. High-pressure gas hydrogen commonly used is applied to vehicle and tube trailers. In particular, high-pressure hydrogen storage tank for vehicles must comply with the guidelines stipulated in SAE J2601. There is a charging temperature limitation condition for the safety of the storage tank material. In this study, numerical analysis method were verified based on previous studies and the nozzle angle was changed for thermal management to analyze the increase in forced convection effect and energy uniformity due to the promotion of circulation flow. The previously applied high-pressure hydrogen storage tank has a length/diameter ratio of about 2.4 and was analyzed by comparing the length/diameter ratio with 8. As a result, the circulation flow of hydrogen flowing into the high-pressure hydrogen storage tank is promoted at a nozzle angle of 30° than the straight nozzle and accordingly, the effect of suppressing temperature rise by energy uniformity and forced convection was confirmed.

• Journal of the Korean Society of Visualization
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• v.8 no.2
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• pp.31-39
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• 2010

Hysteresis is an effect by which the order of previous events influences the order of subsequent events. Hysteresis phenomenon of supersonic internal flows with shock waves has not yet been clarified satisfactorily. In the present study, experiments are carried out on internal flow in a supersonic nozzle to clarify the hysteresis phenomena for the shock waves. Flow visualization is carried out separately on the straight and divergent channels downstream of the nozzle throat section. Results obtained were compared with numerically simulated data. The results confirmed hysteresis phenomenon for shock wave in the Laval nozzle at a certain specific condition. The relationship between hysteresis phenomenon and the range of the rate of change of pressure ratio with time was shown experimentally. The existence of hysteretic behavior in the formation, both the location and strength, of shock wave in the straight part of the supersonic nozzle with a range of pressure ratio has also been confirmed numerically.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.12-18
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• 2008

In the present study, the numerical simulation has been performed to investigate K-factor for temperature variation of working fluid in spray nozzle with orifice. The commercial CFD software, Fluent with the proper modeling was applied for analyzing the internal of the spray nozzle. Numerical result for K-factor at $20^{\circ}C$ agrees with the experimental result that it applied n=0.5 within about 7% error. The pressure drop inside nozzle is showed 20% passing swirler, 70% in the region between the outlet of swirler and the orifice and 10% at the outlet of orifice. As the operating pressure is increased, K-factor is decreased by effect of flow resistance at it's inlet before pass swirler. The temperature increase of working fluid reduced the flow rate according to reducing of density, and average 1.23% decrease is showed in the present research.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.50-59
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• 1999

The effect of a variant drain orifice damping on the characteristics of a servovalve flapper-nozzle stage is analyzed. Steady-state characteristics of flapper-nozzle stage and the linearized dynamics of flapper-nozzle assembly with a spool valve show that the variant drain orifice damping could improve such null performance characteristics as null pressure sensitivity and linearity of gain function. Generalized design criterion and a sufficient condition for servovalve stability are also established.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.9
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• pp.395-399
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• 2003

In this paper, physical phenomena which are related to the high temperature and high pressure arc plasma generated during the fault current interruption by SF6 gas circuit breakers are reviewed. In particular, in order to analyze nozzle ablation induced by the heats transferred to the surface of the poly-tetrafluoroethylene(PTFE) nozzle through arc radiation, a governing equation for the calculation of PTFE concentration is added to the governing equations for SF6 arc Plasma analysis. The proposed method is applied to the steady state analysis of $SF_6$ arc plasma generated by direct current taking account of the nozzle ablation and the results are presented.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.717-722
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• 2003

The aspect ratio is the main parameter which governs the outer flow pattern and nozzle performance. And in this study, some flow characteristics with the variation of nozzle aspect ratios such as mean pressure distributions along the center line of the outer flow, flow coefficients and the diffusion angles have been experimentally investigated. Through the experimental analysis, the higher aspect ratio was known to decrease the jet kinetic energy because of the friction losses at the outer of nozzle. As the result, it is found that the nozzle performance depends mainly on the aspect ratio of nozzle.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.1-7
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• 2004

This paper describes the characteristics of injection rate and macroscopic behavior of fuel spray injected from common-rail type diesel injectors with different nozzle geometries. The injection rates according to the nozzle geometries were measured at different energizing duration of the injector solenoid and injection pressure by using the Bosch's injection rate meter based on the pressure variation in the tube. The spray behaviors injected from the different nozzles were visualized using the spray visualization system composed of an Ar-ion laser, an ICCD camera, and a synchronization system at various injection and ambient pressures. It is revealed that VCO nozzle has higher spray tip velocity at the early stage of injection duration and wider spray cone angle than the mini-sac nozzles. Also the spray cone angle is increased with the increase of nozzle diameter.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.98-109
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• 1994

This paper is studied on the junction stress of the large tank and the cylindrical outlet such as a pressure vessel attached to a pope or nozzle theoretically. It is assumed that the diameter of tank is much larger than that of the nozzle cylinder, so it can be approximated that nozzle cylinder is attached to plate. As the current nozzle shape is manufactured as "Through Type" to reduce the stress concentration around the nozzle junction part of pressure vessel, a theoretical analysis on the cylinder with finite length should be performed to accomodate this fact. Each theoretical optimal values were obtained through the analysis of stress concentration caused by the variation of cylinder length and thickness, and these results were estimated by performing FEM Analysis. Analysis.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.2
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• pp.34-41
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• 2010

This work is concerned with the analysis of stress corrosion cracking(SCC) behavior of Alloy 600 nozzle penetration mock-up according to a residual stress induced by a dissimilar metal welding(DMW) in a nuclear reactor pressure vessel. The effects of the dimension and materials of the nozzle penetration on the deformation and the residual stress induced by DMW were investigated using a finite element analysis(FEA). The inner diameter(ID) change of the nozzle by DMW and its dependance on the design variables, calculated by FEA, were well consistent with those measured from the mock-up. Accelerated SCC tests were performed for three mock-ups with different wall thicknesses in a highly acidic solution to investigate mainly the effect of the residual stress on the SCC behavior of Alloy 600 nozzle. From a destructive examination of the mock-up after the tests, the SCC behavior of the nozzle was fairly related with the residual stress induced by DMW : axial cracks were found in the ID surface of the nozzle within the J-weld region where the highest tensile hoop stress was predicted by FEA, while circumferential cracks were observed beyond both J-weld root and toe where the highest tensile axial stress was expected.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.