• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.54-60
• /
• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.9
• /
• pp.1276-1283
• /
• 2002

Recently, HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a 4-valve small diesel cylinder head with a tangential and helical intake port. The flow characteristics such as coefficient of flow rate(Cf), swirl ratio (Rs), and mass flow rate (ms) were measured in the steady flow test rig using the impulse swirl meter and the analysis of in-cylinder flow field was conducted by experiment using the PIV and calculation using the commercial CFD code. As the results from steady flow test indicate, the mass flow rate of the cylinder head with a short distance between the two intake ports is increased over 13% than that of the other head. However, the non-dimensional swirl ratio is decreased approximately 15%. From in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the velocity distribution became uniform near the TDC. In addition, the results of the calculation are good agreement with the experimental results.

• Journal of the Korean Society of Visualization
• /
• v.7 no.1
• /
• pp.14-20
• /
• 2009

In comparison with previous researches fur swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• 한국가시화정보학회:학술대회논문집
• /
• 2007.11a
• /
• pp.143-148
• /
• 2007

In comparison with previous researches for swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• 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 the Korean Society of Visualization
• /
• v.1 no.2
• /
• pp.38-46
• /
• 2003

An experimental investigation was performed to study the turbulent characteristics of swirling flow a 90$^{\circ}C$ circular tube for Re = 10,000, 15,000 and 20,000. 2D-PIV(Particle Image Velocimetry)technique was employed to measure the fluctuation velocity field. The results include spatial distributions of mean velocity vectors, turbulence intensity and turbulence kinetic energy. The axial and radial turbulence intensities, and kinetic energy profiles show double-peak structures in the inlet region of the 90 degree bend and the profiles are disappeared along the test tube with decaying the swirl intensity.

• Journal of ILASS-Korea
• /
• v.3 no.2
• /
• pp.1-13
• /
• 1998

A theoretical and experimental study was carried out to predict the drop size distribution of the pressure swirl atomizer. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed that the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. Drop size distribution was obtained by using maximum entropy formalism. Seven constraints in the form of the definition of mean diameter were used in this formulation in order to avoid the difficulties of estimating source terms. In this study $D_{10}$ only was introduced into the formulation as a constraint. The predicted drop size and drop size distribution agreed well with the measured data.

• Journal of the Korean Society of Visualization
• /
• v.7 no.1
• /
• pp.21-28
• /
• 2009

The study of swirling flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of streamline. The fluid flow for tubes and elbow of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirling flow have been insufficient. Using the particle image velocimetry(PTV) method, this study found the time averaged velocity distribution with swirl and without swirl along longitude sections and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compares with that of other. Furthermore, other experimental investigation was performed to study the characteristics of turbulent water flow in a horizontal circular tube by using liquid crystal. 2D PIV technique is employed for velocity measurement and liquid crystal is used for heat transfer experiments in water. Temperature visualization was made quantitatively by calibrating the colour of the liquid crystal versus temperature using various approaches.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.401-405
• /
• 2011

Although the APU combustors were developed successfully, it could face many unexpected hardships in a engine or a system operated under the severe environment. This study is to be verified and settled by experimently and analytically of the problems and issues occurred in a variety of engine and system operation tests.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1482-1487
• /
• 2004

In general the swirl jet is generated by the injected flow that is forced to the tangential direction. A spiral nozzle which is composed of an annular slit and a convergent nozzle, is released the spiral jet that is generated by the radial flow injection through an annular slit. The objective of the present study is to investigate the additional study that is studied a changed the convergent nozzle angle and nozzle length. In the present computation, a finite volume scheme is used to solve three dimensional Navier-Stokes equations with RNG $k-{\varepsilon}$ turbulent model. The convergent nozzle angle and the nozzle length of the spiral nozzle are varied to obtain different spiral flows inside the conical convergent nozzle. The present computational results are compared with the previous experimental data. The results obtained show that the convergent nozzle angle and the nozzle length of the spiral jet strongly influence the characteristics of the spiral jets, such as a tangential and a jet width.