• Journal of ILASS-Korea
• /
• v.15 no.1
• /
• pp.8-16
• /
• 2010

This paper present the diesel spray characteristics at different injection system parameters in a HSDI diesel engine. The spray characteristics was calculated by the coupled simulation of fuel injection system model and three-dimensional KIVA-3V code with TAB spray model. The relevant injection parameters are accumulator volume, control chamber initial volume, control orifice diameter, needle valve diameter and nozzle chamber initial volume, etc. Parametric investigation with respect to twelve relevant injection parameters showed that there was a significant advantage in varying control chamber initial volume, control chamber orifice diameter, and nozzle chamber orifice diameter with respect to effect the SMD and fuel injection speed. Consequently, in order to design the fuel injection system for spray characteristics, it seems reasonable to suppose to be optimized the fuel injection system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.171-174
• /
• 2008

This paper presents disintegration process of the small rotational fuel injector. In order to understand disintegration precess, we measured droplet diameter, velocity and spray distribution by the PDPA(Phasse Doppler Particle Analyzer) system. Also spray was visualized by using Nd-Yag flash photography. From the test results, the liquid column emerging from the injection orifice is mainly controlled by the rotational speeds. Furthermore, droplet diameter(SMD) and spray distribution were strongly influenced by the diameter of the injection orifice.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.7 no.3
• /
• pp.7-12
• /
• 2010

In the case of hydraulic piston motor, hydrostatic bearing is designed to be adapted the hydrostatic bearing for the relative lubrication in the structural design. It's available to make it highly efficient and that's why it's widely used. The thing which largely influence the high pressure, the high efficiency, and the life is the hydrostatic bearing between a shoe and a swash plate. In this study, with the most general "hydrostatic bearing shoe" that has one recess as the subject of this research, I designed and made the 4 kind of piston shoe that have different orifice diameter each other, and studied the features of the hydrostatic bearing by observing the change of the leakage flow rate, the torque and the volumetric efficiency through experiments on the changes of the pressure & the speed of the revolution. As a result, the bigger diameter of the orifice, the less torque. And with an increase of the orifice diameter under the high pressure, the leakage flow rate decreased remarkably. Also it was observed the leakage flow rate increased linearly according to the increase of the supply pressure.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.10
• /
• pp.1387-1393
• /
• 2002

The measurement of velocity and stain rate field has been conducted in opposed impinging jet combustion. When a smaller diameter (5mm) orifice of pre-chamber was used, previous studies had reported that the combustion phase showed a shift from weak turbulent combustion to moderate turbulent combustion in the modified Borghi Diagram. In the case with smaller orifice diameter (5mm), NOx emission was substantially reduced by a factor 1/2 while the combustion pressure remains at the same as that in the conventional combustion. Hence, in this study, the experiment setup using PIV technique was designed to identify the relation of the strain rate distribution and NOx reduction associated with moderate turbulent combustion. As a result, it was found that the highly strained pockets are widely distributed during the combustion in the middle of chamber when the orifice diameter is 5mm. And the corresponding PDF distribution of strain rates she was the smoothly distributed strain .ate within the range of ｜$\pm$1000｜ (1/sec) rather than a spike shape about zero point. This is the unique feature observed in the combustion with 5mm orifice diameter. Therefore, it can be concluded that the substantial NOx reduction in opposed impinging combustor is mainly attributed to the strain rate distribution within the range of ｜$\pm$1000｜resulting in the combustion phase shift to moderate turbulent combustion.

• 유체기계공업학회:학술대회논문집
• /
• 2000.12a
• /
• pp.265-271
• /
• 2000

Orifice meters and turbine meters are frequently used for measuring gas flow in gas industry. However, to insure the accuracy of the measurement, a certain length of the meter run at the upstream of the flow meter is required. The objective of this study is to analyze flow measurement errors of the orifice meter quantitatively for shorter lengths of the meter runs than those suggested in the standard manuals with variation of diameter ratio( $\beta$ ratio) and flow rate and also to analyze flow measurement errors of the turbine meter with and without straightener. The test results showed that the flow measurement errors of the orifice meter were inversely proportional to the diameter ratio. In other words, when the diameter ratio is 0.3 and 0.7, the measurement error is $-7.3\%$ and $-3.5\%$, respectively. the main reason of the measurement error is due to the swirl effect from the configuration of the meter run at the upstream of the flow meter. In case the length of the meter run is shorter than that suggested In the standard, the swirl effect is not removed completely and it affects the flow meter's performance. As mentioned above, the less the pipe diameter ratio, the mon the flow measurement error. It means that the swirl effect on the orifice meter increases as the $\beta$ ratio decreases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.12
• /
• pp.1039-1046
• /
• 2002

To investigate the characteristics of orifice as an expansion devices, the experimental apparatus was made and experiments are being peformed using R22 and R290. The main idea of this control method of refrigerant flow rate with coupled orifices is to control the ON/OFF state of T and Ball type orifice corresponding to the subdivided region of thermal load. When system requires minimum thermal load, both T and Ball type orifices are closed, but refrigerant can flow through small hole of T type orifice. In regular thermal load, when ball type orifice is closed, T type orifice is opened and mass flow rate increase more than OFF state of T type orifice, due to large diameter. In maximum thermal load, both T and Ball type orifices are open and the much refrigerant can flow. The flow characteristics on T type orifice and parallel-combined orifice are obtained in the subdivided region of thermal load.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.14 no.5
• /
• pp.51-56
• /
• 2010

An experimental study was performed to understand spray characteristics of the V type rotating fuel nozzle with orifice diameters by using high speed rotational system. The experimental apparatus consist of a high speed rotational system, fuel injection system and acrylic case. The droplet size and velocity were measured by PDPA(Phase Doppler Particle Analyzer) and spray was visualized by using Nd-Yag laser-based flash photography. From the test results, droplet size is reduced with increasing orifice diameter up to the critical value. When increasing orifice diameter over than this critical value, droplet size is not decreased with increasing the orifice diameter. This is due to the irregular distribution of the liquid sheet around the inner surface of injection orifice.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.282-286
• /
• 2004

Discharge current oscillation in a 20KHz range is a serious problem for Hall thruster performance, In our previous work, a possibility of controlling the oscillation amplitude by increasing the speed of neutral particles incoming to the ionization zone was predicted in our previous work. In this paper, the effects of diameter of anode orifice on the oscillation phenomena and the thrust performance were evaluated experimentally. The experimental results show that the measured amplitude of oscillation becomes smaller as the diameter of anode orifice. However, the larger orifice makes thrust performance lower. The results of numerical analysis of neutral particles show that these tendencies have much to do with neutral properties.

• Journal of Bio-Environment Control
• /
• v.5 no.2
• /
• pp.194-201
• /
• 1996

A series of experiments to analyse and to compare performance of various types of mini-sprinkler was carried out. Twelve kinds of the sprinkler, which have various sizes of nozzle orifice diameter and structures of spreader, were selected to be tested. Flow (water sprinkling) rate and sprinkling intensity pattern from a sprinkler were measured as a first part of this study, and the results are as follows. Sprinkler flow rate of various sizes of nozzle orifice and applied water pressures could be predicted by Torricelli's theorem. Discharge coefficients of the Torricelli's theorem for the sprinkler nozzle of various sizes were determined by the experiment as 0.90- 0.95, 0.80-0.82 and 0.76-0.79 for 0.8, 1.2 and 1.6 mm of nozzle orifice diameter, respectively. Experiments on sprinkling intensity pattern resulted that nozzle orifice diameter and applied water pressure are major variables for uniformity of the sprinkling intensity. More uniform sprinklering patterns were noted with smaller nozzle orifice diameter of a sprinkler and at lower sprinkling pressure. Besides the variables, structure of spreader of a sprinkler is also an important variable for the uniformity of sprinkling intensity.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.532-537
• /
• 2003

Gas flow through orifice is encountered in many diverse fields of engineering applications. In order to investigate the critical gas flow through an orifice system, a computational analysis is performed using axisymmetric, compressible, Navier-Stokes equations which are numerically solved by a fully implicit finite volume method. In the present study, the discharge coefficients of two different types of orifices which are a straight-bore orifice and a sharp-edged orifice, are predicted to obtain the critical flow conditions. The present CFD data are compared with the previous experimental results. The present computational results show that the critical mass flow rate through orifice is well predicted and it is a strong function of Reynolds number. The discharge coefficient increases with the orifice diameter.