• Proceedings of the KSME Conference
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• 2001.06e
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• pp.499-505
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• 2001

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of $2{\times}10^4$. The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (${\theta}$) against the wall, the interval(L) between orifices, the relative angle of rotation(${\alpha}$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hole affected the pressure drop and the flow field a lot, But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.459-464
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• 2000

In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the Pressure drop, computations using the mass-averaged implicit Wavier-Stokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.5 to 20.0. The standard k-e turbulence model was employed to close the governing equations. Numerical calculations were carried out for some combinations of the multiple orifice configurations. The present CFD data showed that the orifice systems, which have been applied to incompressible flow regime to date, can not be used for the hint operating Pressure ratio flows. The orifice interval did not strongly affect the total pressure drop but the orifice area ratio more than 2.5 led to high pressure drops. The total pressure drop rapidly increased in the range of the operating pressure ratio from 1.5 to 4.0, but it did not depend on the operating pressure ratio over 4.0.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.295-300
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• 1996

To investigate the effects of the side-orifice on the pressure drop for single-phase flow, a series of experiments have been carried out with 16 different downstream test sections with various combinations of side-orifice shapes, different numbers of side-orifices, and different arrangements of the side-orifice using water as a working fluid. From the measurements of the pressure drop and the flow rate, the pressure loss coefficient of the side-orifice(s) has been evaluated. Based on the total number of 529 present data, an empirical correlation for the pressure loss coefficient has been developed in terms of Reynolds number and geometric parameters, such as area ratio, equivalent diameter, leading edge, and average width of side-orifice.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2747-2752
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• 2007

A numerical study has been performed on the flow past a two-staged orifice in a rectangular duct. The flow field including the recirculation region behind the orifice was investigated and the pressure drop was calculated. Water was used as a working fluid and the flow was treated as the turbulent flow, of which the Raynolds number was 6000. The main parameters for the pressure drop and the recirculation region were the orifice's inclined angle against the duct, the interval between two orifices, the shape of the orifice's hole having the same area, and the change of the hole position at the same interval. The variation of the flow field was investigated with each parameter. Consequently, it was found that the most dominant parameter influencing the drop of the pressure was the change of the hole position at the same interval between orifices. Especially when the interval between orifices was narrow and the relative position the holes was changed, its effect to the flow field was shown most drastically as a result of this study. The SIMPLER algorithm with FLUENT code was employed to analyze the flow field.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.398-403
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• 2001

Pressure drop at a helical square duct orifice is numerically evaluated. The orifice is installed at the entrance of a once-through steam generator tube to suppress flow instabilities. The calculated results are compared with the available experimental correlations, and showed good agreement. Effects of curvature ratio and characteristics of the secondary flow with Reynolds number are reported. Through the numerical simulations, pressure drop mechanisms were well understood inside the compact and complicated orifice geometry.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.278-287
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• 2002

The objective of the paper was to calculate the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of 2$\times$10$^4$. The effective parameters fur the pressure drop and the recirculation region were the conical orifice\`s inclined angle ($\theta$) against the wall, the interval(S) between orifices, the relative angle of rotation($\alpha$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area, the number(N) of the orifice's holes having the same mass flow rate, and the thickness(t) of the orifices. It was fecund that the shape of the orifice's hole, the number of the orifice's holes and the thickness of the orifice affected the total pressure drop a lot and that the conical orifice's inclined angle against the wall, the relative angle of rotation of the orifices, the number of the orifice's holes and the thickness of the orifices affected the center location of the recirculation region. The PISO algorithm with FLUENT code was employed to analyze the flow field.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.18-23
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• 2014

This thesis is simulated a aircraft nose landing gear drop-test. flow rate-to-pressure difference characteristics of damping orifices for a nose landing gear is investigated by CFD analyses. Orifice is kind of poppet valve type. it is simulated pressure drop with variable orifice area. it is simulated landing gear model by using ADAMS with CFD result. It's performance evaluated landing gear drop-test and analyzed the results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1371-1379
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• 1997

The high pressure drop is frequently required in the by-pass line of the pump or of the heat exchanger in power plants. However, cavitation produced by a high pressure drop could damage the pipe and pump blades. Conical orifices are adopted to reduce cavitation due to high pressure drop. The discharge coefficients of conical orifice plates were measured by weighing method in the standard water flow system. The discharge coefficients were larger when the ratios of thickness of orifice edge to throat diameter were larger. The noise generated from a conical orifice due to cavitation was measured with a sound level meter and a hydrophone. With increasing the bore diameter of the orifice, the sound pressure level or the noise level due to cavitation became higher. The noise level was suddenly increased at the inception of cavitation.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.31-37
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• 2004

This paper presents spray and combustion characteristics of hydrocarbon fuel injected from pressure-swirl nozzles. Three commercial nozzles with orifice diameters of 0.256, 0.308 and 0.333mm and injection pressures ranging from 0.7 to 1.3 MPa were selected f9r the experiments. Spray characteristics such as breakup length. spray angle and drop size (SMD) were analyzed using photo image analyses and Malvern Panicle Size Analyzer. The drop size was measured with and without a blower at the same measuring locations. The flame length and width were measured using photo image analyses. The temperature distribution along the axial distance and the gas emission such as CO, $CO_2\;and\;NO_x$ were studied. The breakup length decreased with an increase in injection pressure for each nozzle but increased with an increase in nozzle orifice diameter. The spray angle increased and SMD decreased with an increase in injection pressure. The flame with an increased linearly with an increase in injection pressure and in nozzle orifice diameter. The flame temperature increased with an increase in injection pressure but decreased along the axial distance. The maximum temperatures occurred closer to the burner exit and flame at axial distance of 242mm from the diffuser tip. The experimental results showed that the level of CO decreased while that of $CO_2\;and\;NO_x$ increased with an increase in injection pressure and nozzle orifice diameter.