• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.132-140
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• 2009

Recently, the interest in the development of high efficiency Diesel engine technology using alternative fuel has been on the rise and related studies are being performed. Therefore, the DME(Dimethyl Ether), an oxygen containing fuel as an alternative fuel for light oil that can be used for diesel engines since it generates very little smoke. But it is unavoidable that the modification of a fuel supply system in an engine to application of the DME fuel because of DME fuel properties. So, in this study, a DME high pressure pump for a common-rail fuel supply system has been composed and the test results of the pump have been presented. As the results of the tests, it is confirmed that DME pump inlet pressure, pump speed and common-rail pressure effects on the volumetric efficiencies of the pump. Finally, it is defined that the optimum plunger volume of a DME pump has to be extended to the minimum 150% compared to a Diesel pump plunger volume considering DME fuel properties and volumetric efficiencies characteristics at same specifications of the high pressure pump.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.217-222
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• 2006

Internal combustion engine is the main source of environmental pollutants and therefore advanced technology is required to reduce harmful elements from the exhaust gases all over the world. Especially, when the exhaust gas is released front the automotive muffler, exhaust noise has many bad influence on the surrounding environment. In order to reduce the exhaust noise, it is necessary that automotive muffler must be designed for best exhaust efficiency. The sound insulation room was installed for the analysis of an acoustics characteristics of the noise from automotive muffler, in this study. Exhaust gas noise, noise distribution characteristics, pressure and temperature of exhaust gas were investigated with the change of annulus temperature of air cooled annulus automotive muffler and cooled annulus automotive muffler. The following results were obtained with this study. From the frequency analysis of automotive muffler, high noise distribution was observed in the range $100{\sim}2000Hz$. It means that the noise in this range has an dominate influence for the overall noise. Noise reduction of automotive muffler was affected by the temperature of annulus. It is caused the result that the high temperature and pressure of exhaust gas are changed lower by the drop of annulus temperature. The tendencies of noise, the temperature and pressure of exhaust gas are similar to the performance curve of engine. Exhaust gas pressure is determined by the r.p.m. of engine and affected by the cooling performance of automotive muffler.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.111-114
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• 2003

Drop size is one of the most important parameters which are control the performance of the engine using liquid fuel/oxidizer and drop formation is mainly controlled by aerodynamic force caused by ambient gas. Because of this, empirical data and correlation acquired under standard ambient condition are not valid. So experiments under high ambient pressure condition to measure the drop size using image processing method And find the empirical correlation between SMD and chamber pressure(density), injection velocity.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.1-14
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• 2015

In case of a gas turbine engine for supersonic operation, the engine have a wide range of operating inlet mass flow rate and required high performance such as thrust and fuel consumption. Therefore, variable system and its optimal control logic are essentially needed. In this work, a method for performance prediction of a gas turbine engine with variable system compressor and its control scheme were developed. Conceptual design of compact acuation system for the operation of the variable system was also conducted. The performance of a low-bypass ratio mixed flow turbofan engine was analyzed, and it was observed that the surge margin of the engine is improved at off-design condition by applying the control scheme.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.5
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• pp.343-350
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• 2017

Underwater glider with a single buoyancy engine could generally obtain propulsive forces by moving the center of buoyancy and gravity. Futhermore, The hull and internal structure of underwater glider are designed according to the purpose of long-time operation, high speed and a wide variety of payloads (sensors, communications and etc.). In this paper, Ray-type underwater glider featuring flatfish is considered in view of hydrodynamics. The hull design is especially performed by the analysis of fluid resistance and dynamic performance. The resistance performance is analyzed using the Computational Fluid Dynamics (CFD). In addition, a simulation program is implemented in order to verify the validity of dynamics modeling and dynamic performances.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.146-156
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• 2003

A numerical algorithm is developed to analyze the performance of a Unit-injector (UI) System for a diesel engine. The fundamental theory of the algorithm is based on the continuity equation of fluid dynamics. The loss factors that should be seriously regarded on the continuity equation are the compressibility effect of liquid fuel, the wall friction loss in high-pressure fuel lines of the system, the kinetic energy loss of fuel in the system, and the leakage of fuel out of the control volume. For an evaluation of the developed simulation algorithm, the calculation results are compared with the experimental outputs provided by the Technical Research Center of Doowon Precision Industry Co. (DPICO) ； the maximum pressure in the plunger chamber (P$\_$p/) and total amount of fuel injected into a cylinder per cycle (Q$\_$f/) at each operational condition. The result shows that the average error rate (%) of P$\_$p/ and Q$\_$f/ are 2.90% and 4.87%, respectively, in the specified operational conditions. Hence, it can be concluded that the analytical simulation algorithm developed in this study can be reasonably applied to the performance prediction of newly designed UI system.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.167-173
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• 1999

An Euler-based CFD tool has been developed for the performance evaluation of a thrust reverser mounted on a high bypass ratio turbofan engine. The computational domain surrounded by the ground and non-reflection boundary includes the whole nacelle configuration with a deployed thrust reverser. The numerical algorithm is based on the modified Godunovs scheme to allow the second order accuracy in both space and time. The grid system is generated by using eleven multi-blocks, of which the total cell number is 148,400. The thrust reverser is modeled as if it locates at the nacelle simply in all circumferential direction. The existence of a fan and an OGV(Outlet Guide Vane) is simulated by adopting the actuator disk concept, in which predetermined radial distributions of stagnation pressure ratio and adiabatic efficiency coefficient are used for the rotor type disk, and stagnation pressure losses and flow outlet angles for the stator type disk. All boundary conditions including the fan and OGV simulation are treated by Riemann solver. The developed solver is applied to a turbofan engine with a bypass ratio of about 5.7 and the diameter of the fan cowl of 83 inch. The computational results show that the Euler-based inviscid method is very useful and economical to evaluate the performance of thrust reversers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.966-978
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• 2011

Transpiration cooling is the most effective cooling technique for the high-performance liquid rockets and air-breathing engines operating in aggressive environments with higher pressures and temperatures. When applying transpiration cooling, combustor liners and turbine blades/vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. Practical implementation of the cooling technique has been hampered by the limitations of available porous materials. But advances in metal-joining techniques have led to the development of multi-laminate porous structures such as Lamilloy$^{(R)}$ fabricated from several diffusion-bonded, etched metal thin sheets. And also with the availability of lightweight, ceramic matrix composites(CMC), transpiration cooling now seems to be a promising technique for high-performance engine cooling. This paper reviews recent research activities of transpiration cooling and its applications to gas turbines, liquid rockets, and the engines for hypersonic vehicles.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.39-45
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• 2006

In liquid rocket engine turbopump, it is difficult to evaluate turbine performance for high pressure, high temperature circumstance. Turbine test is often done by using air at similarity condition so that the turbine can be tested at lower risk. This paper describes an air similarity test program of liquid rocket engine turbopump turbine. A test facility has been built to evaluate aerodynamic performance of turbines. The test facility consists of high pressure air supply system, mass flow rate measuring nozzle, test section, hydraulic break, exit orifice for pressure control, instrumentation and control system. This paper also presents how to decide the similarity conditions of the turbine test and describes how to control test conditions. Relative standard deviation of measurement parameter was less than 1% and measured turbine efficiency corresponded with analysis result within 2%.