• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.441-449
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• 2002

Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.233-240
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• 2012

An experimental study to improve the impingement characteristics of the assist gas in laser cutting was carried out. For various assist-gas pressures, and locations and installation angles of the nozzle, the characteristics of the impingement of the jet from a supersonic rectangular nozzle were compared to those previously observed for typical circular nozzles. Schlieren flow visualizations and Pitot pressure measurements downstream of the kerf surface were utilized for this purpose. The present rectangular supersonic nozzle decreased the strength of the Mach disc occurring at the corner of the kerf surface, and thus, could weaken the separation of the assist gas on the kerf surface and increase the Pitot pressures downstream compared to conventional circular nozzles.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.47-53
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• 2007

Convective heat transfer coefficient was measured around a circular secondary jet ejected into the supersonic flow field. The wall temperature measurement around a injection nozzle was conducted using infra-red camera. The constant heat flux is applied to the wall around a secondary nozzle. According to jet to freestream momentum ratio, the injection flow penetrates into the supersonic flow field. The measured temperature is used to calculate the convective heat transfer coefficient.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3529-3533
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• 2007

The advantages of the SITVC(secondary injection thrust vector control) technique over mechanical thrust vector systems include a reduction in both the nozzle weight and complexity due to the elimination of the mechanical actuators that are used in conventional vectoring. Computational study is performed to understand the fluidic thrust vectoring control of an axisymmetric nozzle, in which secondary gas injection is made in the divergent section of the nozzle. The nozzle has a design mach number 3. The effect of injection hole number and shape of secondary jet on the mach number distribution of SITVC were investigated. The standard ${\kappa}$ - ${\epsilon}$ turbulence model solved the complex three-dimensional nozzle flows perturbed by the secondary gas jet. The numerical code was validated by experiment. The results showed that the mach number distribution of circular and square nozzle are similar each other. As number of second injection hole increasing, a effect of deflection was decreased.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.2
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• pp.34-41
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• 1997

The objective of this study is to investigate experimentally the frequency characteristics of the hole tones generated by a circular jet of low speed impinging on a plate with a round hole. The experimental results about the sound spectrum and the time wave of the hole tone are presented and discussed in relation with the hole type, the jet velocity and the distance of the nozzle-to-plate with a round hole. From the sound spectrum and time wave measurements, it is found that the hole tone is generated not only by an interaction of convected vortices with a round hole but also by a series of vortex shedding from jets passing through a hole. The hole tones generated by a feedback mechanism consist of many frequency stages and also have a hysteresis phenomenon like an edge tone. But the hole tones generated by a series of vortex shedding have nothing with the stage characteristics. The frequencies of hole tones are influenced by the jet velocity, the distance of the nozzle-to-plate with a round hole and the hole type.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.717-722
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• 2001

A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozzle inlet velocity. An circular sharp edged nozzle type$(45^{\circ})$ was used to achieve uniform mean velocity at the nozzle inlet, and its diameter is 10mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow. In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers(Re=1500, 3000, 4500, 6000 and 7500).

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.770-778
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• 1986

This paper is studied on the Junctiion of the large tank and the cylinderical outlet such as a pressure vessel attached a pipe or nozzle theoretically. It is assumed that the diameter of tank is much larger than that of the nozzle, so it can be approximated that nozzle is attached to plate. The analysis procedure can be viewed as the solution of interdependent subproblems: (a) the stress analysis of the cylinderical shell(nozzle), (b) the plane-stress analysis of the plate membrane problem, and (c) the analysis of the transverse bending deformation in the plate. On the procedure of (a), the Flugge formula are used, and the variables are the length and the ratio of the thickness to the radius of cylinderical shell. The solutions of thess problems are interrelated in the total solution through continuity and equilibrium conditions at the interface of middle planes of the plate and cylinderical shell.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.34-39
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• 2001

A present study is the flow characteristics of impinging jet by PIV measurement and numerical analysis. The flow characteristics of impinging jet flow are affected greatly by nozzle inlet velocity. An circular sharp edged nozzle type($45^{\circ}$) was used to achieve uniform mean velocity at the nozzle inlet, and its diameter is 10mm(d). Therefore, the flow characteristics on the impinging jet can be changed largely by the control of main flow. In this parent study, we investigate the effects of inlet velocity, its variable is nozzle inlet Reynolds numbers(Re=1500m 3000, 4500, 6000 and 7500)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.34-39
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• 2005

In this study, 3-D nozzle shape and the shape of nozzle at exit plane were adopted as design parameter of 3-D supersonic nozzle and numerical analyses for these parameters have been performed to investigate the flow and performance characteristics for design parameters of the turbine. Firstly, comparing results for nozzle shape, rectangular nozzle had less total pressure loss occurred in axial gap and more power by 1.5% than circular nozzle did. Next, comparing the results for the shape of nozzle at exit plane, it is found that the performance of partial admission turbine was largely depended upon the gap between nozzle wall at exit plane and the hub / tip of rotor blade and the length between nozzles.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.23-29
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• 2010

A supersonic nozzle specially is one of the important part in a supersonic turbine usually adapted the impulse type, because the flow acceleration in the turbine theoretically is done only in the nozzle. The present study deals with numerical flow analysis to investigate the effect of nozzle shapes on the performance characteristics of a partial admission supersonic turbine. The flow analysis was performed for four different nozzle shapes. The shapes of the nozzles are circular, square, straight rectangular and bent rectangular nozzles. The results of the flow analysis showed that the aerodynamic loss of turbine is highly affected by the nozzle shapes, and the partial admission loss is also highly depended on nozzle shapes. Specially, bent rectangular nozzle had the best performance among the nozzle shapes