• Journal of ILASS-Korea
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• v.12 no.1
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• pp.38-44
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• 2007

Since the Liquid Phase LPG injection (LPLI) system has Advantages in power generation and emission characteristics compared to the mixer-type fuel-supply system, a variety of studies regarding LPLi system has been conducted and its applications are made in automobile industry. However, the heat extraction due to the evaporation of liquid fuel, causes not only a post-accumulation of fuel but also an icing phenomenon which is a frost of moisture in the air around the nozzle tip. Since there exists a difficulty in the accurate control of air fuel ratio in both fuel supply systems, it can result in poor engine performance and a large amount of harmful emissions. This research examines the characteristics of icing phenomenon and develops anti-icing bushing to prevent an icing on the surface of the injection tip. It was found that n-butane, which has a relatively high boiling point ($-0.5^{\circ}C$), was a main species of post-accumulation. Also the results show that the post-accumulation problem was allevaited the utilization of a large inner to outer bore ratio and smooth surface roughness. In addition, an icing phenomenon and its formation process were found to be mainly affected by the humidity and the temperature of inlet air in an inlet duct. Also, it was observed that an icing phenomenon is lessened using aluminum bushing whose end coincides with the end of fuel injection tip in length.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.313-323
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• 2003

The sliding wear behaviors of Zircaloy-4 nuclear fuel rod were investigated using two support springs with convex and concave shapes in room temperature air and water. The main focus is to compare the wear behavior of various test variables such as slip amplitude, environment, contact contours with different spring shape and a number of cycles. The results indicated that wear volume and maximum wear depth increased with slip amplitude in both air and water, but their trends tended to change according to the spring shapes and test environments. In air condition, the wear volume was controlled by wear debris behavior generated on worn surface. As a result, final wear volume and maximum wear depth decreased if a ratio of protruded wear volume to worn area $(D_p)$ would be saturated to specific value. This is because wear particle layer could accommodate large strain by accumulating and transforming wear particle layer. However, in water condition, metal-to metal contact was more dominant and wear volume was greatly affected by changed mechanical behavior between contact surfaces since wear debris should be generated after repeated plastic deformation and fracture. After wear test, worn surfaces were examined using optical microscope and SEM and details of wear mechanism were discussed using a ratio of wear volume to worn area $(D_e)$ at each test condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.386-395
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• 2005

With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

• Journal of Korean Society of Transportation
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• v.33 no.2
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• pp.145-158
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• 2015

A network connectivity has been regarded as a key element to strengthen a business competitive power in the aviation industry, so many airport authorities try to attract the new airlines and scheme out new air routes. With this trend, a study for an induced travel demand estimation methodology is needed. This study introduces a demand estimation method, especially for a new air route to a promising destination. With the results of previous studies, the derived demand is classified into four types - Local, Beyond, Behind and Bridge. The explanatory variables are established for each type of demand and the main independent variables are composed of distance, ratio of detour, and relative capacity compared with other airports. The equations using such variables and statistically significant coefficients are suggested as the model to make an estimation of derived demand for a new route. Therefore this study will be expected to take an initial step for all related parties to be involved more deeply into developing new air routes to enhance network connectivity.

• Journal of ILASS-Korea
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• v.21 no.3
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• pp.130-136
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• 2016

NOx and PM are important air pollutants as vehicle management policy aspect. Medium-duty truck is the main source of the pollutants although the vehicle market share is only 3.5%. National emission portion of NOx and PM form the mobile sourece are 14% and 16% respectively. In this study it was investigated that characteristics of air pollutants emission on medium duty truck equipped with EGR and SCR system. Vehicle's test reflected driving cycle on the chassis dynamometer, and applied test cycle was WHVC(World Harmonized Vehicle Cycle) mode. The test cycle include three segments, represent urban, rural and motorway driving. Based on the test results NOx, PM, HC were less emitted form SCR vehicle than EGR vehicle. And CO was less emitted form EGR vehicle than SCR vehicle due to CO oxidation reaction on DPF surface. And most air pollutants reduced as average vehicle speed increased. Pollutants were less emitted on motorway section than urban and rural sections. But highly NOx emission on motorway section was verified according to increased EGR ratio on fast vehicle speed. HC and CO additional emission was identified as 68%, 58% respectively during SCR vehicle's cold engine start emission test. NOx additional emission was detected by 24% on SCR vehicle's condition of engine cold start while not detected on vehicle equipped with EGR. SCR vehicle's additional NOx emission was derived from low reaction temperature during engine cold start condition. medium-duty truck emission characteristics were investigated in this study and expected to used to improve air pollutants management policy of medium-duty truck equipped with SCR & EGR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.818-825
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• 2004

In this paper, the study of effects of flow parameters on flame structure and NOx emission concentration was performed in co-axial. laminar partially premixed methane/air flames. Such (low parameters as equivalence ratio(${\Phi}$), fuel split percentage($\sigma$), and mixing distance(x/D$\_$i/) were defined as a premixing degree and varied within ${\Phi}$=1.36∼9.52, $\sigma$=50∼100, and x/D$\_$i/=5∼20. The image of OH$\^$*/ and NOx concentration were obtained with an ICCD camera and a NOx analyzer. The flame structure observations show a categorization of partially premixed flames into three distinct flame regimes corresponding to ${\Phi}$<1.7(premixed flame structure), 1.7<${\Phi}$<3.3(hybrid structure), and ${\Phi}$>3.3(diffusion flame structure existing a luminous sooting region) at $\sigma$=75%, and x/D$\_$i/=10. As o decreases from 100% to 50%, and x/D$\_$i/ decreases, nonpremixed flame structure appear at low equivalence ratio relatively. In addition, the measured emissions for NOx rise steeply from ${\Phi}$=1.7, to ${\Phi}$=3.3, then constants ${\Phi}$>4.76. NOx emissions decrease with increase the level of premixing level. In conclusion, the main effect on flame structure and NOx production was at first equivalence ratio(${\Phi}$), and next fuel split percentage($\sigma$), and finally mixing distance(x/D$\_$i/).

• Advances in Energy Research
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• v.4 no.1
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• pp.29-45
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• 2016

There has been a growing interest in the recent time for the development of solar power tower plants, which are mainly used for utility scale power generation. Combined heat and power (CHP) is an efficient and clean approach to generate electric power and useful thermal energy from a single heat source. The waste heat from the topping Brayton cycle is utilized in the bottoming HRSG cycle for driving steam turbine and also to produce process steam so that efficiency of the cycle is increased. A thermal storage system is likely to add greater reliability to such plants, providing power even during non-peak sunshine hours. This paper presents a conceptual configuration of a solar power tower combined heat and power plant with a topping air Brayton cycle. A simple downstream Rankine cycle with a heat recovery steam generator (HRSG) and a process heater have been considered for integration with the solar Brayton cycle. The conventional GT combustion chamber is replaced with a solar receiver. The combined cycle has been analyzed using energy as well as exergy methods for a range of pressure ratio across the GT block. From the thermodynamic analysis, it is found that such an integrated system would give a maximum total power (2.37 MW) at a much lower pressure ratio (5) with an overall efficiency exceeding 27%. The solar receiver and heliostats are the main components responsible for exergy destruction. However, exergetic performance of the components is found to improve at higher pressure ratio of the GT block.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.781-789
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• 2008

The fluorescence ratio method for processing planar laser induced fluorescence(PLIF) data was generalized for quantitative imaging of the injectant mole-fraction in supersonic mixing flowfields. The original fluorescence ratio approach was introduced by Hartfield et al. for tests in a special closed-loop wind tunnel to eliminate the effects of thermodynamic property variations in compressible flowfields and to provide a quantitative means of mole-fraction measurement. However, they implicitly assumed that the tracer molecules were seeded at the same fraction in both main and secondary flows. In the present study, we proposed generalizing the Hartfield method by considering differences in the tracer seeding rates. We examined the generalized method in a mixing flowfield formed by sonic transverse injection into a Mach 1.8 supersonic air stream. The injectant molefraction distribution obtained from PLIF data processed by our new approach showed better agreement with the gas chromatograph than one based on the Hartfield method.

• Journal of Environmental Science International
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• v.21 no.10
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• pp.1235-1244
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• 2012

The objective of this study is to evaluate Flow-Pollutant load delivery ratio equations developed from rural watershed on main subwatersheds within Juam Lake. Two regression equations for BOD and three equations for T-P were evaluated on Bosung cheon, Dongbok cheon, Songgwang cheon, Naenam cheon, and Sinpyeon cheon. The results show that estimation of BOD delivery ratio using flow-delivery equation is reliable when relative composition of discharge load of pollutant sources of a watershed is similar to those of watershed where the equation developed. On the other hand, application of regression equation for T-P was feasible when the landuse pattern and relative composition of discharge load of pollutant sources of a watershed is similar to those of watershed where the equation developed.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.339-345
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• 2013

This study is to derive from the required performances and the optimum mix proportion of the roof concrete placed in the in-ground LNG storage tank with a capacity of 200000 $m^3$, and propose the actual data for site concrete work. The concrete placing work without sliding and segregation in the fresh concrete condition is very important because the slope of domed roof is varied in the large range by its curvature. Also the control of hydration heat and the strength development at test ages are classified with massive section about 1.4 m thick and considered to the pre-stressing work and removal of air support after concrete placing work. Considering above condition, slump range is selected $100{\pm}25$ mm under the slope $20^{\circ}$ and $150{\pm}25$ mm over the slope $20^{\circ}$ s until 60 minutes of elapsed time. Also, the roof concrete is satisfied with compressive strength range including design strength at 91 days (30 MPa), pre-stressing work at 7 days (10 MPa), air support removal work at 21 days (14 MPa). Replacement ratio of limestone powder is determined by confined water ratio test and main design factors include water-cement ratio (W/C), sand-aggregate ratio and dosage of admixture. As test results, the optimum mix proportion of the roof concrete used low heat cement is as followings. 1) Replacement ratio of limestone powder 25% by confined water ratio test 2) Water-cement ratio 57.8% 3) Sand-aggregate ratio 42.0%. Also, test results for the adiabatic temperature rising test is satisfied with its criteria and shown the lower value compared to preceding storage tank (TK-13, 14). These required performances and the optimum mix proportion is to apply the actual construction work.