• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.23-32
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• 2002

Combustion and flame propagation characteristics of the liquid phase LPG injection (LPLI) engine were investigated in a single cylinder optical engine. Lean bum operation is needed to reduce thermal stress of exhaust manifold and engine knock in a heavy duty LPG engine. An LPLI system has advantages on lean operation. Optimized engine design parameters such as swirl, injection timing and piston geometry can improve lean bum performance with LPLI system. In this study, the effects of piston geometry along with injection timing and swirl ratio on flame propagation characteristics were investigated. A series of bottom-view flame images were taken from direct visualization using an W intensified high-speed CCD camera. Concepts of flame area speed, In addition to flame propagation patterns and thermodynamic heat release analysis, was introduced to analyze the flame propagation characteristics. The results show the correlation between the flame propagation characteristics, which is related to engine performance of lean region, and engine design parameters such as swirl ratio, piston geometry and injection timing. Stronger swirl resulted in foster flame propagation under open valve injection. The flame speed was significantly affected by injection timing under open valve injection conditions; supposedly due to the charge stratification. Piston geometry affected flame propagation through squish effects.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.49-54
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• 2003

The purpose of this work is to investigate the effect of premixed fuel on the reduction of exhaust emissions in premixed charge compression ignition engine. The premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber. The pre-mixture is ignited by a small amount of diesel fuel directly injected into the cylinder. In the case of gasoline as a premixed fuel of the engine, $NO_x$ and smoke concentration of exhaust emissions were reduced compared with the conventional diesel engine. But in the event of diesel fuel for premixed fuel, the rate of smoke reduction was small compared with the case of gasoline as a premixed fuel. HC and CO emissions were increased at high premixed ratio in the case of two premixed fuels. The combustion characteristics of the engine such as the combustion pressure, the rate of heat release, and other characteristics are compared.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.82-90
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• 2017

The aim of this work is to develop a new computational program to determine the effect of using the gas of propulsion of combustion chamber at high temperature on the shape of the two-dimensional Minimum Length Nozzle giving a uniform and parallel flow at the exit section using the method of characteristics. The selected gases are $H_2$, $O_2$, $N_2$, CO, $CO_2$, $H_2O$, $NH_3$, $CH_4$ and air. All design parameters depend on the stagnation temperature, the exit Mach number and the used gas. The specific heat at constant pressure varies with the temperature and the selected gas. The gas is still considered as perfect. It is calorically imperfect and thermally perfect below the threshold of dissociation of molecules. A error calculation between the parameters of different gases with air is done in this case for purposes of comparison. Endless forms of nozzles may be found based on the choise of $T_0$, $M_E$ and the selected gas. For nozzles delivering same exit Mach number with the same stagnation temperature, we can choose the right gas for aerospace manufacturing rockets, missiles and supersonic aircraft and for supersonic blowers as needed in settings conception.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.636-640
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• 2011

Film cooling technique has been applied to effectively reduce thermal load on liquid rocket combustion chambers by direct injection of a portion of propellant, which flows through the regeneratively cooling channels, into the chamber wall. This study developed a comprehensive model to quantitatively predict the effects of kerosene film cooling on propulsive performance and wall cooling at supercritical pressure conditions, and assessed the predictive capability against hot-firing tests of an actual combustor. The present model is expected to be utilized as a design and analysis tool to meet the conflicting requirements in terms of performance, cooling, pressure loss and weight.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.149-157
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• 2004

In the present paper we studied experimentally fundamental optimization of oxygen enriched pyrolysis melting incinerator, Characteristics of this system was confirmed dealing with the gas flow and combustion properties for the inside secondary air injection. The experiment setup has a disposal rate of 30kg/hr which was measured by the inside temperature and gas. Along with above experiments, the three-dimensional computation was employed to analyse the combustion fluid dynamics and gas residence time. Equations for turbulence and heat - transmission as well as chemical reactions were solved by using common codes. The experimental combustion chamber was composed of staged combustion types structure for reducing NOx. Finally, it was verified that the control of the secondary air and air ratio of thermo stack were important. In the computational analysis, it showed reasonable agreement with the experimental results regarding the temperature and discharged gas concentration.

• Korean Journal of Human Ecology
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• v.12 no.5
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• pp.747-754
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• 2003

The actual clothing conditions were surveyed to diagnose clothing condition of Korean female in the view point of the adaptation to the thermal environment according to seasonal changes. Then, clothing microclimate, physiological responses, and subjective sensation were investigated through wearing trials on human body in climatic chamber based on the results from the survey. Factors to evaluate validity of clothing condition were clothing weight, clothing microclimate, physiological response of human body, and subjective sensation. The results were as follows: 1. Clothing weight per body surface area of the season was $856g/m^{2}$, $439g/m^{2}$ in summer, $630g/m^{2}$ in fall, and $1184g/m^{2}$ in winter. Cold - resistance of Korean female in office was superior to Japanese, inferior to residents of rural areas of Korea, and similar to male in office. However, in heat - resistance, female in office was inferior to residents of rural areas of Korea. 2. In spring, fall, winter, clothing microclimate temperature was a little higher than that in summer. Therefore, it was not a desirable wearing condition even though the clothing microclimate was comfortable zone. 3. Mean skin temperature of female in office was including within the range of Winslow's comfortable zone, but the range of comfortable zone in mean skin temperature of female was more narrow than Winslow's. Thus, it has problem for female to adaptation to thermal environment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.886-889
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• 2001

Silicone rubber is being used for the housing material of outdoor high voltage insulators such as composite insulator, bushing, surge arrestor and cable terminator because of good tracking and erosion resistance, good hydrophobicity and recovery of hydrophobicity and chemical stability. But, the leakge current occurs on surface of the composite polymeric insulation materials when the insulator is used for a long time with severe contaminative condition and it can lead the contamination flashover. So the leakage current is important to estimate the condition of the silicone rubber surface. In this paper, aging characteristics of silicone rubber used for outdoor insulation have been hydrophobicity of silicone rubber in salt fog chamber with average leakage current monitoring for observing the transformation of surface degradation properties of silicone rubber with different ATH(alumina trihydrate, A1$_2$O$_3$$.$3H$_2$O) filler contents. The experimental results show that a higher peak leakage current and to raise a long time for tracking with increasing amount of ATH by the salt fog and heat recycle ageing.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.457-463
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• 1999

The Joule-Thomson cryocooler with $H_2$gas has been developed. Cool-down characteristics and the cooling performance of a JT cryocooler have been investigated in detail. The JT cryocooler consists of JT expansion valve, heat exchanger, expansion chamber, compressed $H_2$gas storage tank, $LN_2$precooler, heater and a cryostat. The precooling process using both $GN_2$and $LN_2$was peformed to cool down the inside components of cryocooler under the maximum inversion temperature of $H_2$. The $H_2$expansion experiments have been peformed for 2-5MPa of H$_2$pressure to evaluate steady state temperatures of the cryocooler. It is found that the steady state temperatures are decreased as the H$_2$pressures are increased. The effects of cooling temperatures on the performance have been evaluated for various $H_2$and $N_2$pressures. It is seen that the cooling loads are increased, as the cooling temperature and operating pressure are increased.

• Solar Energy
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• v.2 no.2
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• pp.11-20
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• 1982

This paper presents the experimental investigations of a system as a second treatment means to increase boiler efficiency and heat transfer from combustion gas to heating surfaces in the case of spray combustion. In order to reburn residual combustible components accelerate the burning rate of sprayed fuel droplets, improve the diffusion flame and delay the residence time of the flame, advice with slit type nozzles for spouting preheated supplementary air is used in this study. In the experiment, boiler efficiency and smoke concentration in the exhaust gas at given conditions are measured in both case of installing and not-installing device in the model of combustion chamber which was designed to be equipped with five surfaces. The results obtained in this experiment are as follows ; 1. The optimum values of air rate ${\lambda}$ are about 1.3 in both case. 2. The exhaust gas temperature in the case with device increases about $30{\sim}70^{\circ}C$ above that of the case without the device. 3. Boiler efficiency and reduction effect of smoke emissions are improved considerably.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.559-568
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• 2013

Increased worldwide concerns about fossil fuel costs and effects on the environment lead many governments and scientific societies to consider the hydrogen as the fuel of the future. Many researches have been made to assess the suitability of using the hydrogen gas as fuel for internal combustion engines and gas turbines; this suitability was assessed from several viewpoints including the combustion characteristics, the fuel production and storage and also the thermodynamic cycle changes with the application of hydrogen instead of ordinary fossil fuels. This paper introduces the basic environmental differences happening when changing the fuel of a marine gas turbine from marine diesel fuel to gaseous hydrogen for the same power output. Environmentally, the hydrogen is the best when the $CO_2$ emissions are considered, zero carbon dioxide emissions can be theoretically attained. But when the $NO_x$ emissions are considered, the hydrogen is not the best based on the unit heat input. The hydrogen produces 270% more $NO_x$ than the diesel case without any control measures. This is primarily due to the increased air flow rate bringing more nitrogen into the combustion chamber and the increased combustion temperature (10% more than the diesel case). Efficient and of course expensive $NO_x$ control measures are a must to control these emissions levels.