• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.5
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• pp.365-372
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• 2009

The influence of combustor pressure on the local reaction characteristics of $CH_4$/air flames was investigated by measurements of local chemiluminescence intensity. Induced flow flames are often applied to the industrial boiler systems and incinerator in order to improve heat transfer and prevent exhaust gas leakage. In order to investigate combustion characteristics in the induced flow pattern, the combustor pressure index($P^*$) was controlled in the range of $0.7{\sim}1.3$ for each equivalence ratio in the present combustion system, where $P^*$ is defined as the ratio of absolute pressure to atmospheric one. Relationship between local reaction intensity and pressure index have been investigated by simultaneous $CH^*$, $C^*_2$ and $OH^*$ intensity measurements. It could be observed that flame length became longer with decreasing $P^*$ from $CH^*$ chemiluminescence intensity of axial direction. The mean value of $C^*_2$ and $CH^*$ chemiluminescence intensities, which indicates reaction intensity in the $CH_4$/air flames, decreased with decreasing pressure index for ${\Phi}{\leq}1$, but increased with decreasing pressure index for ${\Phi}$>1. $C^*_2/CH^*$ intensity ratio, which can be a good marker to demonstrate local equivalence ratio, was almost same for ${\Phi}{\leq}1$ regardless of pressure index change, while they showed high level for lower pressure index for ${\Phi}$>1 conditions.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.2
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• pp.28-38
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• 2001

Traffic information can be broadly categorized into point information and spatial information. Point information can be obtained by chocking only the presence of vehicles at prespecified points(small area), whereas spatial information can be obtained by monitoring large area of traffic scene. To obtain spatial information by image processing, we need to track vehicles in the whole area of traffic scene. Image detector system based on global tracking consists of video input, vehicle detection, vehicle tracking, and traffic information measurement. For video input, conventional approaches used auto iris which is very poor in adaptation for sudden brightness change. Conventional methods for background generation do not yield good results in intersections with heave traffic and most of the early studies measure only point information. In this paper, we propose user-controlled iris method to remedy the deficiency of auto iris and design flame difference-based background generation method which performs far better in complicated intersections. We also propose measurement method for spatial traffic information such as interval volume/lime/velocity, queue length, and turning/forward traffic flow. We obtain measurement accuracy of 95%∼100% when applying above mentioned new methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.72-82
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• 2005

The objective of this paper is to describe the optimization of design parameters in a large-sized commercial bus heater system by using CFD(computational fluid dynamics) analysis and Taguchi method. In order to obtain the best combination of each control factor which results in a desired performance of heater system, the parameter design of the Taguchi method is adopted for the robust design considering the dynamic characteristic. The research activity may be divided into four phases. The first one is analyzing the problem, i.e., ascertaining the influential factors. In the second phase the levels were set in such a way that their variation would significantly influence the response. In the third phase the experimental runs were designed. In the final phase the planned runs were carried out numerically to evaluate the optimal combination of factors which is able to provide the best response. In this study, eight factors were considered for the analysis: one with two level and seven with three level combinations comprising the $L_{18}(2^1{\times}3^7)$ orthogonal array. The results of this study can be summarized as follows ; (i)The optimum condition of control factor is a set of <$A_2\;B_1\;C_3\;D_3\;E_1\;F_2\;G_3\;H_2$> where A is shape of the outer fin, B is pitch of the outer fin, C is height of the outer fin, D is the inner fin number, E is the inner fin height, F is length of the flame guide, G is diameter of the heating element and H is clearance between air guide and heating element. (ii)The heat capacity of heated discharge air under the optimum condition satisfies the equation y=0.6M w here M is a signal factor. (iii)The warm-up rate improves about three times, more largely as com pared with the current condition, which results in about 9.2minutes reduction.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.7-13
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• 2017

As environmental problems become a problem of survival, interest in eco-friendly energy is increasing to improve the environment. So, demand for eco-friendly fuels such as hydrogen, LPG and CNG is increasing. In particular, Korea, which relies on imports of most fuels, is investing in the development of hydrogen energy, which is favorable in terms of high production volume and energy independence. However, As demand grows every year, a variety of accidents occur in various ways, ranging from small leak incidents to massive fires and explosion, thus research needs to be done. So, in this study, compared and analyzed cases of hydrogen, LPG, CNG accidents occurring at domestic and overseas refueling stations. and various programs were used for assessing risk, estimated the flame length due to gas leakage and evaluated the dangerous distance.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.72-86
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• 2006

A technical review of current ramjet propulsion is presented. In addition to summarize the current status of ramjet technology, new key techniques like Boosting technique easily adapting total impulse of booster, flame stabilization technique with minimized ramjet combuster length, variable nozzle-inner-surface technique realizing wide flight-envelop, and thermal protection technique for long operating time are identified. Actually various Ramjet propulsion technology has been matured and expanding to both military and combined cycle application. Yet many opportunities remain to be challenged by future generations of explorers to utilize s typical ramjet propulsion system for multi-purpose(multi-platform and multi-target) missiles, for example, American JSSCM and Russian Yakhont missiles, improving both reliability of techniques and downsizing development cost of new propulsion system.

• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.49-55
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• 2020

Experimental investigations were conducted to understand the multi-staged combustion characteristics of a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. Multi-staged combustion is implemented by injecting the fuel through the existing manifold of the side slots as well as through the apex of the cone with two fuel injection angles which are slanted or axial. NOx and CO emissions, and wall temperature distributions were measured for various fuel distributions and operating conditions. Results show that NOx emissions are decreased when the fuel distribution to the apex is 3% of the total amount of fuel, which is due to more uniform fuel distribution inside the nozzle, hence less hot spots at the flame. NOx emissions are rather increased when the fuel distribution to the apex is 8% of the total amount of fuel for axial fuel injection by occurrence of flash back in premixing zone of burner.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.36-42
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• 2019

In this study, the pre-treatment of lyocell fabrics was performed using phosphoric acid (PA) as a phosphorus flame retardant and melamine resin (MR) as a cross-linking agent to fabricate carbon fabrics using lyocell fibers. The physical and chemical changes were investigated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and weight analysis. We confirmed that the weight yield of the carbon fabrics compared to the untreated fabrics increased by 14.7%, and width and length yield of the fabrics increased by 15% and 15.5%, respectively. This may be due to the effect of promoting the dehydration reaction of cellulose, forming char on the fiber surface, which induces a crosslinking reaction in the cellulose molecule and stabilizes the structure upon pyrolysis.

• Journal of ILASS-Korea
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• v.23 no.4
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• pp.192-204
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• 2018

In this study, a 3D CFD analysis method for the combustion process was established for a low calorific value syngas-diesel dual-fuel engine operating under very lean fuel-air mixture condition. Also, the accuracy of computational analysis was evaluated by comparing the experimental results with the computed ones. To simulate the combustion for the dual-fuel engine, a new dual-fuel chemical kinetics set was used that was constituted by merging two verified chemical kinetic sets: n-heptane (173 species) for diesel and Gri-mech 3.0 (53 species) for syngas. For dual-fuel mode operations, the early stage of combustion was dominated by the fuel burning inside or near the spray plume. After which, the flame propagated into the syngas in the piston bowl and then proceeded toward the syngas in the squish zone. With the baseline injection system and piston shape, a significant amount of unburned syngas was discharged. To solve this problem, effects of the injection parameters and piston shape on combustion characteristics were analyzed by calculation. The change in injection variables toward increasing the spray plume volume or the penetration length were effective to cause fast burning in the vicinity of TDC by widening the spatial distribution of diesel acting as a seed of auto-ignition. As a result, the unburned syngas fraction was reduced. Changing the piston shape with the shallow depth of the piston bowl and 20% squish area ratio had a significant effect on the combustion pattern and lessened the unburned syngas fraction by half.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.141-149
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• 2021

The A60 class deck penetration piece is a fire-resistance apparatus installed on the deck compartment to protect lives and to prevent flame diffusion in the case of a fire accident in a ship or offshore plant. In this study, the sensitivity of the fire-resistance performance and approximation characteristics for the A60 class penetration piece was evaluated by conducting a transient heat-transfer analysis and fire test. The transient heat-transfer analysis was conducted to evaluate the fire-resistance design of the A60 class deck penetration piece, and the analysis results were verified via the fire test. The penetration-piece length, diameter, material type, and insulation density were used as the design factors (DFs), and the output responses were the weight, temperature, cost, and productivity. The quantitative effects of each DF on the output responses were evaluated using the design-of-experiments method. Additionally, an optimum design case was identified to minimize the weight of the A60 class deck penetration piece while satisfying the allowable limits of the output responses. According to the design-of-experiments results, various approximate models, e.g., a Kriging model, the response surface method, and a radial basis function-based neural network (RBFN), were generated. The design-of-experiments results were verified by the approximation results. It was concluded that among the approximate models, the RBFN was able to explore the design space of the A60 class deck penetration piece with the highest accuracy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.33-43
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• 2021

A60 class bulkhead penetration piece is a fire resistance system installed on a bulkhead compartment to protect lives and to prevent flame diffusion in a fire accident on a ship and offshore plant. This study focuses on the approximate optimization of the fire resistance design of the A60 class bulkhead penetration piece using a multi-island genetic algorithm. Transient heat transfer analysis was performed to evaluate the fire resistance design of the A60 class bulkhead penetration piece. For approximate optimization, the bulkhead penetration piece length, diameter, material type, and insulation density were considered discrete design variables; moreover, temperature, cost, and productivity were considered constraint functions. The approximate optimum design problem based on the meta-model was formulated by determining the discrete design variables by minimizing the weight of the A60 class bulkhead penetration piece subject to the constraint functions. The meta-models used for the approximate optimization were the Kriging model, response surface method, and radial basis function-based neural network. The results from the approximate optimization were compared to the actual results of the analysis to determine approximate accuracy. We conclude that the radial basis function-based neural network among the meta-models used in the approximate optimization generates the most accurate optimum design results for the fire resistance design of the A60 class bulkhead penetration piece.