• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.495-501
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• 2012

Spray characteristics of liquid jets in crossflow, which can be observed in the liquid jet injection system of a gas turbine or ramjet engine, were experimentally investigated. By measuring liquid jet penetration in the case of single orifice and double orifice injectors, the experimental formula for jet penetration was modified to consider penetration distances greater than that considered in a previous study. The changes in spray characteristics resulting from changes in the liquid jet and crossflow pressure, including SMD and jet disintegration, were carefully studied. Specifically, the jet penetration was measured for different injector shapes, and in the case of a double orifice injector, the penetration of the rear orifice jet was found to be greater by approximately 20% ($L_h$ = 4 mm) compared to that in the case of a single orifice injector because of the influence of the front orifice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.905-910
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• 2010

Exhaust manifolds are the first structures to be developed by hydroforming; mass production of exhaust manifolds by this method will be possible soon. This is obviously related with tight emission regulation induced by environmental problems commonly for both domestic and worldwide and standards, thus evoking its solution for domestic automakers. Compared to conventional cast products, thin-gauge tubular hydroformed exhaust manifold have superior features; for example, in the hydroformed exhaust manifold, gas decomposition during the cold-start period of the engine is reduced by lowering the heat sink, and manufacturing process is simplified since less welding is involved. The aim of this study is to develop a hydroformed exhaust manifold; the study deals with the components, the hydroforming process, and tool design of the manifolds. The performance of the exhaust system is evaluated by performing flow analysis, heat-transfer analysis, heat-stress analysis, and fatigue analysis by using a computer.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.117-122
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• 2005

Electron Beam Physical Vapor Deposition (EB-PVD) is a typical technology for thermal barrier coating with Yttria Stabilized Zirconia (YSZ) on aero gas turbine engine. In this study EB-PVD method was used to fabricate dense YSZ film on NiO-YSZ as a electrolyte of Solid Oxide Fuel Cell (SOFC). Dense YSZ films of -10 $\mu$m thickness showed nano surface structure depending on deposition temperature. Electrical conductivities of YSZ film and electric power density of the single cell were evaluated after screen- printing $LaSrCoO_3$ as a cathode.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.108-117
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• 2013

The oxidizer shutoff valve of a gas generator controls the mass flow rate of the propellant of a rocket engine using pilot pressure and spring the force of the valve. The developing oxidizer shutoff valve can be shut off if the pilot pressure is removed from the actuator. Therefore, force balancing is necessary to analyze the characteristics of the forces with respect to the opening and closing of the valve in order to evaluate its performance. In light of this, the valve has been designed to adjust the control pressure required to open the poppet and to determine the working fluid pressure at which the valve starts to close. Under cryogenic flow test as a tests level of C.R.T(Control Random Test), the chattering phenomena occurred due to much leakage of a metal seat section. The pressure for chattering of the oxidizer valve is predicted at about 11 bar using force balancing analysis.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.1
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• pp.68-76
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• 2012

SULEV (Super Ultra Low Emission Vehicle) which is one of the emission standards in Fleet Average System introduced to Korea from 2009 is known as the most severe standard to achieve with internal combustion engine. Considering low sales volume of hybrid vehicles in Korea, vehicle manufacturers are required to develop SULEV technologies for conventional gasoline and LPG vehicles to meet the future Fleet Average standard. In this study, the comparison of emissions has been made between SULEV developed and ULEV LPG vehicles mainly produced in this time. To estimate the emission reduction of SULEV vehicles, CVS-75 and NIER test modes have been used. CVS-75 has been used for emission certification of gasoline and LPG vehicles. NIER modes cover various average vehicle speed and reflect Korean real driving patterns better than CVS-75. The test results show that SULEV LPG vehicles have very high potential to reduce $NO_x$ in regulated emissions, $N_2O$ in green house gases and toluene in VOCs. However, SULEV LPG vehicles don't affect much on the reduction of CO and total green house gases.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.300-305
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• 2017

It is necessary to establish a system suitable for the driving vehicle so that it can effectively search for and modify various data anywhere and anytime by effectively linking communication with the computer system in the running vehicle and to control the equipment properly for smooth operation on a limited platform do. Also, vehicle CAN communication is used to extract system engine information, and data is transmitted using ZigBee for this information transmission. Therefore, OBD-II protocol, which is provided by the vehicle itself, is used for vehicle CAN to obtain vehicle status information and exhaust gas using various sensor information of the vehicle and O2 sensor value, and transmits it to the ZigBee main control system. In this study, we implemented a system that can reduce the battery load damage to the maximum by reducing the power consumption to the maximum, and to monitor the internal state of the vehicle through ZigBee communication with the embedded system for low power vehicles.

• Journal of Navigation and Port Research
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• v.28 no.5
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• pp.365-372
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• 2004

LNGC suffers a great heat inflow during navigation and this heat inflow inevitably boils off the LNG. The boiled off gas(BOG) is normally consumed as a fuel for ship's engine. The boiled off LNG means a loss of cargo during transportation in the viewpoint of shipper. Therefore, a contract between shipper and ship operator is made for the limitation of BOR under 0.15 ％/day based on laden voyage. This contract on BOR limit requires that ship's officer has a correct knowledge on BOR for his ship. nut, in most cases ship IS operated based on only officer's experiences. In this study, author presented a simple model to predict the BOG during navigation based on the existing precision heat exchange design technology about the heat distribution on the hull and heat inflow from outside through the hull. The BOG is calculated for ballast and laden voyage based on the actual weather conditions and verified by comparing with the measured BOG for the study ship. The study ship is a membrane type LNGC which is now servicing in Middle east route. Thus, the BOG prediction method which is presented in this study is expected to be used for an useful tool to manage the BOG in now servicing LNGC.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.553-559
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• 2006

Most diesel injector, which is currently used in high-pressure common rail fuel injection system of diesel engine, is driven by the solenoid coil energy for its needle movement. The main disadvantage of this solenoid-driven injector is a high power consumption, high power loss through solenoid coil and relatively fixed needle response's problem. In this study, a prototype piezo-driven injector, as a new injector mechanism driven by piezoelectric energy based on the concept of inverse piezo-electric effect, has been designed and fabricated to know the effect of piezo-driven injection processes on the diesel spray structure and internal nozzle flow. Firstly we investigated the spray characteristics in a constant volume chamber pressurized by nitrogen gas using the back diffusion light illumination method for high-speed temporal photography and also analyzed the inside nozzle flow by a fully transient simulation with cavitation model using VOF(volume of fraction) method. The numerical calculation has been performed to simulate the cavitating flow of 3-dimensional real size single hole nozzle along the injection duration. Results were compared between a conventional solenoid-driven injector and piezo-driven injector, both equipped with the same micro-sac multi-hole injection nozzle. The experimental results show that the piezo-driven injector has short injection delay and a faster spray development and produces higher injection velocity than the solenoid-driven injector. And the predicted simulation results with the degree of cavitation's generation inside nozzle for faster needle response In a piezo-driven injector were reflected to spray development in agreement with the experimental spray images.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4302-4307
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• 2011

Recently, various technologies for the fuel efficiency improvement are being developed. The purpose of this study is to evaluate the heat exchanging performance of a exhaust heat recirculation device and to propose a model with optimized performance. The device has been designed to warm up engine coolant as quickly as possible using wasted exhaust heat. To achieve these goals, heat transfer characteristics has been analyzed using CFD for the flow direction effect and in/out location effect of coolant. A method improving the effectiveness of heat exchange has been proposed. As a result, the highest efficiency in heat exchange was observed on condition that exhaust heat affects the coolant directly with a separate flow path between exhaust gas and coolant and that coolant flow rate is relatively low.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.