• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.8
• /
• pp.645-651
• /
• 2015

The objective of this study is to experimentally investigate the effect of design parameter on the mass ratio of a central-driven ejector. The design parameters are the primary nozzle area and distance ratios, diffuser exit-area ratio and mixing-tube length ratio. The experimental setup was an open-loop continuous circulation system which has a movable nozzle ejector, an electric motor-pump, a water tank, a control panel and high-speed camera unit. We calculated the mass ratio using the measured primary and suction-flow rates with the experimental parameter of primary water-flow rate or pressure. The results showed that the mass ratio increased with the primary nozzle distance ratio and mixing tube length ratio, while the mass ratio decreased with the primary nozzle-area ratio and diffuser exit-area ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.9
• /
• pp.906-915
• /
• 2009

To study the plume effects in the vacuum area, the Direct Simulation Monte Carlo(DSMC) method is usually adopted because the plume field usually contains the entire range of flow regime from the near-continuum in the vicinity of nozzle exit through transitional state to free molecular at far field region from the nozzle. The objective of this study is to investigate the behaviors of a small monopropellant thruster plume in the vacuum area numerically using DSMC method. To deduce accurate results efficiently, the preconditioned scheme is introduced to calculate continuum flow fields inside thruster to predict nozzle exit properties used for inlet conditions of DSMC method. By combining these two methods, the vacuum flow characteristics of plume such as strong nonequilibrium near nozzle exit, large back flow area, etc, can be investigated.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.4
• /
• pp.42-52
• /
• 1997

The basic principle of underwater ram-jet as a unique marine propulsion concept showing vary high cruise speed range(e. g. 80-100 knots) is the thrust production by the transfer of the potential energy of compressed gas to the operating liquid through kinetic mixing process. This paper is aimed to investigate the propulsive efficiency of the nozzle flow in underwater ram-jet at the speed of 80 knots for the buried type vessel. The basic assumption of the theoretical analysis is that mixture of water and air can be treated as incompressible gas. For an optimized nozzle configuration obtained from the performance analysis, preliminary data for performance evaluation are obtained and effects of nozzle inner wall friction, ambient temperature, ambient pressure, water density, gas velocity, bubble radius, flow velocity, diffuser area ratio, mass flow ratio and water velocity gradient are investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.383-387
• /
• 2017

A three dimensional numerical analysis has been conducted to analyze the effects of a pipe angle, connecting a combustion chamber and a pintle nozzle, and pintle position on pintle nozzle performance. The compressibility correction of $k-{\omega}$ SST turbulent model was implemented to precisely predict the characteristics of complex flow structures inside a supersonic pintle nozzle. Due to an 3-D asymmetric pintle nozzle configuration, complex helical flow streamlines and large flow separations were observed, which resulting in significant nozzle performance losses. As the angle of connection-tube decreases, the coefficient of performance increases and Since the flow structures are evidently changed to the pintle stroke position, the performance characteristics was analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.05a
• /
• pp.395-399
• /
• 2009

Advanced afterburner used in the most modernized gas turbine has new designing paradigm to cope with reinforced power density. The most distinct change is the designing trend to integrate fuel injectors and flame holder in order to manage higher temperature of inlet air. F414 and F110-GE-132 engine adopted this methodology and installed a variable nozzle utilizing CMC(Ceramic Matric Composite) material and active cooling of nozzle flap with ejector nozzle in order to enhance the life cycle of engine components and an economical aspect. These technological trends can be utilized for an advanced ramjet engine and combined cycle engine like TBCC.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.7 s.94
• /
• pp.1841-1850
• /
• 1993

A simplified one-dimensional analysis has been performed to predict the local pressure distributions in Y-Jet twin-fluid atomizers. Fluid compressibility was considered both in the gas(air) and two-phase(mixing) ports. The annular-mist flow model was adopted to analyze the flow in the mixing port. A series of experiments also has been performed; the results show that the air flow rate increases and the liquid flow rate decreases with the increase of the air injection pressure and/or with the decrease of the liquid injection pressure. From the measured injection pressures and flow rates, the appropriate constants for the correlations of the pressure loss coefficients and the rate of drop entrainment were decided. The local pressures inside the nozzle by prediction reasonably agree with those by the experiments.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.11
• /
• pp.3021-3031
• /
• 1994

Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1998.10a
• /
• pp.11-11
• /
• 1998

최적의 액체 램제트 연소기 설계를 위하여 흡입공기와 분무, 혼합 그리고 이에 따른 연소의 일련의 과정이 일어나는 램제트 연소기의 유동해석을 2차원 및 3차원으로 수행하였다. 격자구성은 연소기에 공기를 공급하고 연료를 분무하는 공기 유입관 영역과 연소실 및 노즐 영역, 그리고 출구 대기 영역으로 나누어 독자적으로 격자를 생성시켰다. 연소실 내의 유동 특성에 있어서 2차원과 3차원의 유동해석 결과는 선회영역 유동특성이 크게 차이가 남을 알 수 있었다. 따라서 실제 액체 램제트 연소기의 설계를 위해서는 3차원 유동해석과 실험이 반드시 필요하다.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.2
• /
• pp.175-181
• /
• 2011

The purpose of this study is to secure the design data for the optimization of the radial turbine and heat cycle system, by using the CFD analysis technique and the design of 100kW class radial turbine applicable to waste heat recovery generation system for ship. Radial turbine was comprised of scroll casing, vane nozzle with 18 blades and rotor with 13 blades, and analysis grid was used to about 2.3 million. Mass flow rate and rotational speed was 0.5kg/s, 75,0000rpm, respectively. Eight kinds of inlet pressure was set between 195 and 620kPa. As the flow accelerated through the nozzle passage to the throat, the pressure level at the pressure and suction sides becomed similar to about Mach number of 0.35. When the inlet temperature and pressure was $250^{\circ}C$, 352kPa respectively, the isentropic efficiency and mechanical power showed the analysis results of 74% and 108kW.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.12
• /
• pp.1643-1651
• /
• 2012

Recently, with increasing standards of living and income, environmental pollution has attracted increased interest. On account of a revision to water pollution regulations, the improvement of sewage disposal efficiency was studied. One of the ways to improve the sewage disposal efficiency is to increase the dissolved oxygen content of water in the water treatment tank. In this study, we suggest a nozzle design using a spiral and a crash mode for generating micro bubbles and thus increasing the dissolved oxygen content of water. The micro bubbles through the spiral and crash flows are generated in the nozzle. In the design of the crash mode, the development goal with regard to the bubble size was not achieved. On the other hand, a bubble size of $0-50{\mu}m$ accounted for 79.3% of all bubbles in the spiral mode. This study should contribute toward increasing the sewage disposal efficiency.