• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1726-1746
• /
• 2022

This paper presents fracture mechanics analysis results for various cracks located at pressurized water reactor pressure vessel nozzle crotch corners taking into consideration constraint effect. Technical documents such as the ASME B&PV Code, Sec.XI were reviewed and then a fracture mechanics analysis procedure was proposed for structural integrity assessment of various nozzle crotch corner cracks under normal operation conditions considering the constraint effect. Linear elastic fracture mechanics analysis was performed by conducting finite element analysis with the proposed analysis procedure. Based on the evaluation results, elastic-plastic fracture mechanics analysis taking into account the constraint effect was performed only for the axial surface crack of the reactor pressure vessel outlet nozzle with cladding. The fracture mechanics analysis result shows that only the axial surface crack in the reactor pressure vessel outlet nozzle has the stress intensity factor exceeding the low bound of upper-shelf fracture toughness irrespectively of considering the constraint effect. It is confirmed that the J-integral for the axial crack of the outlet nozzle does not exceed the ductile crack initiation toughness. Hence, it can be ensured that the structural integrity of all the cracks is maintained during the normal operation.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.3
• /
• pp.28-39
• /
• 2018

In this study, numerical simulations were performed for steady and unsteady state characteristics of length effects on linear pintle nozzles using the overset grid method. Nozzles and pintles are created separately by an auto grid generation program to use the overset grid method. Appropriate turbulent models and numerical methods are selected for the validation of simulations. Pintle shapes are chosen from five types, with differences in the ratio of length and diameter. The longer the pintle length, the greater the thrust and thrust coefficient. The chamber pressure tendency of steady-state and unsteady-state are different for various pintle velocities. The thrust of the nozzle exit responds to changes in the nozzle throat in the unsteady-state, and the speed of pressure propagation wave generated by movement of the pintle is considered to predict the major factor of performance.

• Journal of ILASS-Korea
• /
• v.1 no.2
• /
• pp.42-49
• /
• 1996

The structure of sprays from a simplex type pilot nozzle atomizer is studied experimentally by measuring velocities, Sauter mean diameter, and number density. Interaction of the spray with gas-phase flow field generated from a 1 MW range industrial gas turbine combustor adopt ing a counter-swirler is investigated. Various spray behaviors are reported. Especially interest ing characteristics are the tangential motion of the spray and of the spray with swirl interaction. It shows a Rankine combined vortex type of velocity characteristics, having linear velocity profile inside the inner core whole small particles exist and rapidly decreasing velocity profiles outside. Interacting spray has relatively uniform number density profiles compared to the nozzle spray itself.

• Journal of Mechanical Science and Technology
• /
• v.17 no.5
• /
• pp.726-739
• /
• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.839-847
• /
• 2004

In this study, the flow characteristics within supersonic cascades are numerically investigated by using Fine Turbo, a commercial CFD code. Cascade flows are computed for three different inlet conditions. : a uniform supersonic inlet condition, a linear nozzle and a converging-diverging nozzle located in front of cascades. The effect of inlet conditions is compared and flow characteristics including shock patterns and shock-boundary layer interaction are analyzed. Also the effect of design parameters such as pitch-chord ratio, blade angle and blade surface curvature on the flow within supersonic cascades are studied.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.727-728
• /
• 2009

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2763-2768
• /
• 2007

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed using similitude model and simulations. Similitude models are designed so that the flow pattern is same as that of 1/10 scale flow by using high viscous fluid as working fluid. The results are compared to the simulations. It is shown that the flow characteristics of 2D simulation are different from 3D simulations at high Re region, and the measured pump efficiency is highly dependent on the pressure difference as well as the channel geometry. From these results, the desirable conditions for the efficient pump is discussed.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.15 no.3
• /
• pp.3053-3058
• /
• 1973

1. This study was conducted to examine the effects of change of the short range nozzle hole on the travelling distance. The results of this study are summarized as follows; a) Effect of change of the cap hole diameter on the travelling distance of sprayed particles was generally a linear, the increasing rate was about 0.27. b) When the difference between the sectional area of cap hole and that of grooves of swirl plate, was small the travelling distance was decreased by the decreasing of spraying speed at cap hole. 2. This study was conducted to examine the effects of change of the short range nozzle hole on the size of spraying particles. The results of this study are summarized as follows; a) The diameter of sprayed particles on travelling distances in the short range nozzle did not coincide with the kinetic energy principle derived from the momentum and the resistance. b) The average diameter of sprayed particle between 1m and 3m in which amount of sprayed particle was particularly a great deal, was big, because that some of sprayed particles were absorbed each other on the way to fall c) Effect of increase of cap hole diameter was generally enlarged the average diameter of sprayed particle with small rate.

• Journal of ILASS-Korea
• /
• v.26 no.4
• /
• pp.189-196
• /
• 2021

Spray drift of agricultural nozzles has become a big issue because it causes low precision targeting and environmental pollution. In order to reduce the spray drift, study spray characteristics of agricultural nozzles is virtually important. In this study, shadowgraph and Mie-scattering visualization techniques were used to study the macroscopic spray and atomization characteristics of an agricultural nozzle. PDPA was used to measure the atomization characteristics of spray. The injection pressure is set to 1 bar, 3 bar and 5 bar, which covers the working range of the nozzle. For the PDPA experiment, 75 points were measured in an area of 160 mm × 120 mm at 10 mm intervals directly below the nozzle to grasp the overall atomization characteristics of the spray. It was found that the spray width and sheet width showed a linear correlation. As the injection pressure increased, the sheet expansion in the 0-degree direction and the sheet swing in the 90-degree direction jointly promoted the breakup of the sheet. In addition, the area close to the central axis had a large droplet velocity, and since a large droplet velocity promoted atomization of spray, the area close to the central axis had a smaller spray droplet diameter than the left and right regions.

• Journal of Environmental Science International
• /
• v.27 no.3
• /
• pp.219-225
• /
• 2018

This study was conducted to investigate the possibility of utilizing various types of nozzles and gas-liquid mixers to increase the dissolution rate of plasma gas containing ozone generated in a dielectric barrier plasma reactor. After selecting the air atomizing nozzle with the highest gas dissolution rate among the 13 types of test equipment, we investigated the influence of the operating factors on the air atomizing nozzle to determine the optimal plasma gas dissolution method. The gas dissolution rate was measured by a simple and indirect method, specifically, the measurement of KLa instead of direct measurement of ozone concentration, which requires a longer analysis time. The results showed that the KLa value of the simple mix of air and water was $0.372min^{-1}$, Which is 1.44 times higher than that ($0.258min^{-1}$) of gas emitted from a normal diffuser. Among the nozzles of the same type, the KLa value was highest for the nozzle having the smallest orifice diameter. Among the 13 types of devices tested, the nozzle with highest KLa value was the M22M nozzle, which is a gas-liquid spray nozzle. The relationship between water circulation flow rate and KLa value in the experimental range was linear. The air supply flow rate and KLa value showed a parabolic-type correlation, while the optimum air supply flow rate for the water circulation flow rate of 1.8 L / min is 1.38 times.