• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.248-253
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• 2009

This paper presents a numerical study for unsteady flows in a high-pressure steam turbine with a partial admission stage. Compressible Navier-Stokes equations are solved by the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. The SST-model is also solved for evaluating the eddy-viscosity. The unsteady two-dimensional flows through whole nozzle-rotor cascade channels considering a partial admission are numerically investigated. 108 nozzle passages with two blockages and 60 rotor passages are simultaneously calculated. The influence of the flange in the nozzle box to the lift of rotors is predicted. Also the efficiency of the partial admission stage changing the number of blockages and the number of nozzles is parametrically predicted.

• Current Optics and Photonics
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• v.8 no.2
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• pp.170-182
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• 2024

The dimensional accuracy and consistency of a dual oil circuit centrifugal fuel nozzle are important for fuel distribution and combustion efficiency in an engine combustion chamber. A point cloud measurement method was proposed to solve the geometric accuracy detection problem for the fuel nozzle. An improved variance focus measure operator was used to extract the depth point cloud. Compared with other traditional sharpness evaluation functions, the improved operator can generate the best evaluation curve, and has the least noise and the shortest calculation time. The experimental results of point cloud slicing measurement show that the best window size is 24 × 24 pixels. In the height measurement experiment of the standard sample block, the relative error is 2.32%, and in the fuel nozzle cone angle measurement experiment, the relative error is 2.46%, which can meet the high precision requirements of a dual oil circuit centrifugal fuel nozzle.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.1
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• pp.51-59
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• 1994

The gas jet pumps serve to preduce a vacuum or can be used as gas jet compressors. These are operated on the same principle as a steam jet vacuum pump : in the driving nozzle the pressure energy of the motive medium is converted into the kinetic energy. In the diffuser the driving jet mixes with the suction medium and the kinetic energy is reconverted into the pressure enegy. The application fields of gas jet ejectors are the evacuation of siphoning installations, the elevation of liquids, the production of vacuum filters, the vacuum supporting airlift system, the evacuation of the suction line of centrifugal pumps and the ventilation of the dangerous gases to the atmosphere. The performance of gas jet ejector is influenced strongly to velocity coefficient of motive nozzle, the distance between the motive outlet to the diffuser inlet and the dimensions of diffuser. This study is performed for the computer aided design of gas jet ejectors in future. Through the present experiments, it is known that the velocity coefficient of the motive air nozzle ranges from 0.91 to 0.95 and the maximum efficiency of gas jet ejector is 24.6%.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.52-58
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• 2005

To establish low-cost and high efficiency water treatment process, feasibility of applying ultrasonic spray nozzle for chemical injection was evaluated. Ultrasonic spray nozzle was manufactured using piezoelectric ceramics. Treatment efficiencies of contaminants by ultrasonic spray nozzle were compared with conventional chemical mixing such as back-mixing. It was found out that the rate of chemical diffusion rate by ultrasonic spray nozzle was faster than by back-mixing method. Removal efficiencies of various contaminants, such as turbidity, organics and microorganism by ultrasonic spray nozzle were also higher than by back-mixing method. By adapting ultrasonic spray nozzle in coagulant injection process, it can be prevented that the decline of treatment efficiency by coagulant overdose. The amount of coagulant can be reduced by applying ultrasonic spray nozzle in water treatment. Along with these advantages chemical mixing chamber is not required if ultrasonic spray nozzle is adapted. From these results, it can be concluded that chemical injection by ultrasonic spray nozzle is an economical and highly efficient device for coagulant mixing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.29-35
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• 2020

Transition Nozzles are used in industrial air-cooled heat exchangers and widely used in industrial sites as an important component in the heat energy transfer between a heat source and an actuating fluid. There is a worldwide demand for transition nozzles with various materials and shapes, depending on the use environment. This paper aims to improve the transition nozzle forging process suitable for the production of many varieties using Steps 1 to 6 of the TRIZ Methodology for Problem Solving. By utilizing the TRIZ Methodology, this study derives a method to design a variable mold, which is more efficient and can reduce costs compared with having to use several molds. To verify the suitability of the methods derived using the TRIZ technique, a forging analysis is performed on a transition nozzle using DEFORMⓇ, a commercial program for plasticity analysis, and the nozzle material is evaluated for damage as a result of deformation of the transition nozzle thickness. The derived methods can be applied to transition nozzle formation equipment to improve the efficiency of the formation process.

• Tribology and Lubricants
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• v.34 no.5
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• pp.175-182
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• 2018

Accumulation of coal ash at the boiler wall reduces combustion and fuel efficiency. The design of a wall blower is important to effectively remove coal ash. We present numerical results for the removal of coal ash from boiler walls of domestic coal-fired power plants, associated with the computational fluid dynamics for the flow from spray nozzle to boiler wall. The numerical model simulates an erosion process in which the multiphase fluid comprising saturated vapor and fluid water is sprayed from the nozzle, and the water particles impact the boiler wall. We adopt the Finnie erosion model for water particles. We obtain the erosion rate density as a function of nozzle angle and its injection angle. As excessive coal ash removal usually induces damage to the boiler wall, the removal operation typically focuses on a large area with uniform depth rather than the maximum removal of coal ash at a specific location. In order to estimate the removal performance of the wall blower nozzle considering several functionality and reliability factors, we evaluate the optimal injection and nozzle angles with respect to the biggest cumulative and highest erosion rates, as well as the widest range and lowest standard deviation of the erosion rate distribution.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.9-15
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• 2003

The liquid phase LPG injection (LPLI) system is considered as one of the next generation fuel supply systems for LPG, vehicles, since it can accomplish the higher power, higher efficiency, and lower emission characteristics than the existing mixer type fuel supply system. However, during the injection of liquid LPG fuel into the inlet duct of an engine, a large quantity of heat is extracted due to evaporation of fuel. A problem is that the moisture in the air freezes around the outlet of a nozzle, which is called icing Phenomenon. It may cause damage to the outlet nozzle of an injector. The frozen ice deposit detached from the nozzle also may cause a considerable damage to the inlet valve or valve seat. In this work, the experimental investigation of the icing phenomenon was carried out. The results showed that the icing phenomenon and process were mainly affected by humidity of inlet air instead of the air temperature in the inlet duct. Also, it was observed that the icing occurs first in the inlet of a nozzle, and grows considerably at the upper part of the nozzle inlet and the opposite side of the nozzle entrance. An LPG fuel, mainly consisting of butane, has lower latent heat of vaporization than that of propane, which is an advantage in controlling the icing phenomenon.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.1-7
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• 2010

Dual throat nozzle(DTN) is recently attracting much attention as a new concept of the thrust vectoring technique. This DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze a fundamental performance of a dual throat nozzle(DTN) at various nozzle pressure ratios(NPR) and throat area ratios. Two-dimensional, axisymmetric, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. NPR was varied in the range of NPR from 2.0 to 10.0, at different throat area ratios. The present computational results were validated with some experimental data available. Based upon the present results, the performance of DTN is discussed in terms of the discharge coefficient and thrust efficiency.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.4
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• pp.395-406
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• 2020

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.162-167
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• 2015

Recently, there has been rising interest in applying urea-SCR systems to large marine diesel engines because the International Maritime Organization (IMO) has decided to enforce NOx reduction regulations. Generally, in the case of urea-SCR of the marine diesel engine, a type of twin fluid atomizer has been using for injection of the urea solution. This study conducted to investigate an effect of the atomization of external-mixing twin fluid nozzle on the conversion efficiency of reductant. The lab-scaled experiment device was installed to mimic the urea-SCR system of the marine diesel engine for this study. In a low temperature inflow gas condition which is similar with the exhaust temperature of large marine diesel engine, this study found that the conversion efficiency of reductant of when relative big size urea solution droplets are injected into exhaust gas stream can be larger than that of when small size urea solution droplets are injected. According to results of this study, the reason was associated with decrease of reaction rate constant caused from temperature drop of inflow gas by assist air of twin fluid atomizer.