• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.281-287
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• 2005

Nonlinear behaviors such as steep-fronted wave motions and a finite amplitude limit cycle often accompanying combustion instabilities have been numerically investigated using a characteristic-based approximate Riemann solver and the well-known ${\eta}-{\tau}$ model. A resonant pipe initially subjected to a harmonic pressure disturbance described the natural steepening process that leads to a shocked N-wave. For a linearly unstable regime, pressure oscillations reach a limit cycle which is independent of the characteristics of the initial disturbances and depends only on combustion parameters and operating conditions. For the 1.5 MW gas generator under development in KARI, the numerical results show good agreement with experimental data from hot-firing tests.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.39-44
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• 2016

Automated voltage regulators (AVRs) are used on ships and offshore to automatically adjust the voltage based on real-time output voltage readings of the generator engine. Analog-type AVR was previously more commonly used, but is slowly being replaced with digital-type AVR because of increased demands of response time. This study presents a new digital AVR system that contains appropriate features of the AVR with respect to offshore unstable load conditions and poor operating conditions. Furthermore, experiments of load and voltage change prove the excellence of stability and response of the proposed system compared to previous AVR systems. Additionally, an integrated control system for a monitoring the output voltage and field current was developed to easily set the gain value.

• Journal of Korea Multimedia Society
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• v.13 no.4
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• pp.609-617
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• 2010

Since Korean mobile communication companies each use different mobile platforms, developers must configure and translate their game contents to run under each of the platforms so that they can be serviced correctly. Nevertheless, such translation tasks require lengthy times and costs. This is one of the reasons why a variety of contents could not be provided. In order to mitigate such difficulty, this paper implemented an automatic mobile contents translating system that automatically translates mobile C game contents of the GNEX platform to mobile java contents of the WIPI platform. The GNEX C-to-WIPI Java automatic contents translation system helps minimize the amount of time and cost required in servicing contents to different mobile communication companies by promptly translating a platform-specific-content to run under other platforms. Also, the automatic translation and servicing of existing contents increases the reusability of these contents and also the productivity of new contents thereby offering users with a more variety of games.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.175-181
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• 2018

Electric pump system is new technology for next generation propulsion unit. The system has simple structure which dose not need gas generator, injector and turbine and might better pump for low cost and low payload rocket. Therefore, this paper suggests conceptual design of electric-pump Permanent-Magnet Synchronous Motor (PMSM) which has 50 kW & 50,000 RPM for rocket. To satisfy the system's requirement, electromagnetic analysis is conducted for suitable inner and outer diameter of stator and rotor which uses 4000 Gauss cylinder magnet and Inconel 718 can to fix whole rotor. Futhermore, to confirm rotational vibration, rotordynamics analysis is conducted. By this analysis, Campbell diagram is printed. From the diagram, natural frequency could be determined for the only motor and dynamo meter test bench.

• Journal of computational fluids engineering
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• v.9 no.3
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• pp.49-56
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• 2004

A heated and expanded helium is used to pressurize liquid propellants in propellant tanks of propulsion system of liquid propellant launch vehicles. To produce a heated and expanded helium, an hot-gas heat exchanger is used by utilizing heat source from an exhausted gas, which was generated in a gas generator to operate turbine of turbo-pump and dumped out through an exhaust duct of engine. Both experimental and numerical approaches of hot-gas heat exchanger design were conducted in the present study. Experimentally, siliconites - electrical resistance types - were used to simulate the full heat condition instead of an exhausted gas. Cryogenic heat exchangers, which were immersed in a liquid nitrogen pool, were used to feed cryogenic gaseous helium in a hot-gas heat exchanger. Numerical simulation was made using commercially utilized solver - Fluent V.6.0 - to validate experimental results. Helically coiled stainless steel pipe and stainless steel exhausted duct were consisted of tetrahedron unstructured mesh. Helium was a working fluid Inside helical heat coil and regarded as an ideal gas. Realizable k-』 turbulent modeling was adopted to take turbulent mixing effects in consideration. Comparisons between experimental results and numerical solutions are Presented. It is observed that a resulted hot-gas heat exchanger design is reliable based on the comparison of both results.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.56-62
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• 2008

A synthetic gas reformed from hydrocarbon-based fuels consists of $H_2$, CO and $N_2$. Hydrogen contained in the synthetic gas is a very useful species in chemical processes, due to its wide flammability range and fast burning speed. The ESGI (Exhaust Synthetic Gas Injection) technology is developed to shorten the light-off time of three way catalysts through combustion of the synthetic gas in the exhaust manifold during the cold start period of SI engines. Before the ESGI technology is applied to the test engine, the authors set a test rig that consists of gas temperature and composition controllers, an exhaust pulse generator and an exhaust manifold with a visualization window, in order to optimize the point and conditions of injection of the synthetic gas. Through measuring burned gas temperatures and taking photographs of synthetic gas combustion at the outlet of the exhaust manifold, the authors tried to find the optimal injection point and conditions. Analysis of burned gas composition has been performed for various $O_2$ concentrations. As a result, when the synthetic gas is injected at the port outlet of the cylinder No. 4 and $O_2$ concentration exceeds 4%, combustion of the synthetic gas is strong and effective in the exhaust manifold.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2001.05b
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• pp.85-91
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• 2001

This paper provides a case study of landfill gas (LFG) utilization fer direct use as process fuel, and for electrical power generation at restored landfills in the Hong Kong Special Administrative Region of China (HKSAR). The paper specifically covers the LFG utilization schemes, which are required under landfill restoration contracts at the Shuen Wan and Urban Landfills. These contracts provide for the restoration and aftercare of six landfills, and are administered by the Environmental Protection Department (EPD) of the Hong Kong Government. The LFG utilization scheme at the Shuen Wan Landfill incorporates the direct use of LFG by compressing and dehumidifying the LFG prior to conveyance through a 1.6-kilometer (1-mile) pipeline. The pipeline provides an alternate fuel source to naphtha during process heating for gas production at the Tai Po Gas Production Plant of the Hong Kong and China Gas Limited (HKCC). The LFG utilization scheme at the Jordan Valley Landfill (one of the Urban Landfills) beneficially uses the LFG as fuel for electrical power generation with reciprocating internal combustion engines. The LFG is compressed, cooled, and filtered prior to delivery to two engine/generator sets. This system provides power to operate the leachate pre-treatment plant, which processes leachate from all of the Urban Landfill sites. The case study will examine the technical and non-technical considerations, including harriers, for developing, designing and implementing the LFG utilization projects in Hong Kong. Specific regulatory considerations and external governmental agency approvals are discussed, including the requirement to register as a gas-producing utility. While the paper focuses on LFG utilization applications in Hong Kong, many of the considerations discussed are also applicable to development of LFG utilization in other regions of Asia.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.2
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• pp.33-44
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• 2010

This paper propose the structure of real-time face detection hardware architecture for robot vision processing applications. The proposed architecture is robust against illumination changes and operates at no less than 60 frames per second. It uses Modified Census Transform to obtain face characteristics robust against illumination changes. And the AdaBoost algorithm is adopted to learn and generate the characteristics of the face data, and finally detected the face using this data. This paper describes the face detection hardware structure composed of Memory Interface, Image Scaler, MCT Generator, Candidate Detector, Confidence Comparator, Position Resizer, Data Grouper, and Detected Result Display, and verification Result of Hardware Implementation with using Virtex5 LX330 FPGA of Xilinx. Verification result with using the images from a camera showed that maximum 32 faces per one frame can be detected at the speed of maximum 149 frame per second.

• 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 the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.79-88
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• 2017

Ignition test of the fuel-rich propellant coated with ignition support material in the ramjet combustor condition was conducted. Ignition delay and flame holding was measured. Fuel grain consist of HTPB mixed with AP particle 15 wt.%, Al particle 5 wt.%. To cause the short ignition delay, ignition support consist of $NC/BKNO_3$ and composite propellant was coated to the fuel grain. Ethanol blended $H_2O_2$ gas generator control the temperature, pressure, $O_2$ concentration in the oxidizer gas in the air. Gas is supplied with mass flux of $200kg/m^2s$. Through the test ignition support operated well and ignition delay of 0.6 second and the Flame was sustained.