• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.24-31
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• 2010

Combustion-stability rating of impinging-jet injector is conducted numerically using hot-fire simulation in a subscale chamber with the five-element injector head. A sample F(fuel)-O(dxidizer)-O-F impinging-jet injector is adopted. In this work, instantaneous chemical reaction is adopted for hot-fire simulation based on the assumption that mixing process of fuel and oxidizer streams is controlling. The model chamber was designed based on the methodologies proposed in the previous work regarding geometrical dimensions and operating conditions. The present stability boundaries are in a good agreement with air-injection and hot-fire experimental data. The proposed numerical method can be applied cost-effectively to stability rating of jet injectors when mixing of fuel and oxidizer jets is the dominant process in instability triggering.

• Journal of the Korean Institute of Gas
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• v.15 no.1
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• pp.60-67
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• 2011

The interest about new and renewable energy is increasing to reduce the burden of problems by depletion of fossil fuels and air pollutions. For example, LNG/CNG and LPG are expected to be replaced, especially in transportation use, by HCNG mixture and DME-LPG mixture, respectively. Because these new energies are still flammable gases, it is not inherently safe from the explosion. In this research, the quantitative risk analysis for using alternative mixtures in existing recharging facilities has been studied by using three types of explosion models (TNT equivalency model, PHAST and CFD-based FLACS) to manage the risk effectively. The differences of results by models were compared against, and the practical ways of when and how to use these models were suggested. It was also predicted that conventional gas filling stations would be converted as new energy stations without additional explosion risk.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.432-445
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• 1994

From a theoretical analysis point of view, the 2-stage precipitator is decomposed into two units: charging cell and collecting cell. Collection efficiency predictions of the two-stage parallel-plate electrostatic precipitator have been performed theoretically incorporating with the charging and the collecting cells. Particle trajectorise passing the charging cell have been modeled as a simple one. Particle charge distribution at the outlet of the charging cell is calculated through integration of the present unipolar combined charging rate along the entire particle trajectory, and average charge of particles at the outlet of the charging cell is obtained from the particle charge distribution. As for the collecting cell, the diminution of particle concentration along the longitudinal direction of the collecting cell is investigated considering the conventional Deutsch's theory and the laminar theory. One should note that the collection efficiency formula derived is based on monodisperse aerosols. It has been confirmed through the analysis that predictions of particle charge by applying White's unipolar diffusion charging theory overpredict actual cases in the continuum regime, while predictions by Fuch's unipolar diffusion charging theory indicate the reasonable result in the same regime. Theoretical predictions of collection efficiency are also compared with the available experimental results. Comparisons show that the experimental results are consistently located in the collection efficiency region bounded by the two limits, the Deutsch and the laminar collection efficiencies. Finally design parameters of the 2-stage electrostatic precipitator have been investigated systematically through the one-variable-at-a-time method in terms of collection efficiency. Applied voltages on the corona wire of the charging cell and the plate of the collecting cell, and the average air velocity have been selected as the design parameters.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.554-558
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• 2006

Construction Industry has become bigger, sophistication and specialization. At the same time, the concerns of Construction Management for achieving the goal of quality, cost & air are getting higher. Therefore it is demanded technology to conduct the CM works continuously in the Industrial world and be in process of education to train specialists. Studies are also been doing for it. But infrastructure circumstances are insufficiency comparing with the interests of construction industry. It is needed the scheme of education system to improve the above mentioned problem and to raise education quality standards. Consequently, the study is for E-learning education system. Because this system can help to save cost and to overcome the limits of time and spaces for existing off-line education. The study will present e-learning system architecture model to activate Construction Management education considering the distinctive features of CM.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.731-746
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• 2008

Most multiphase flow simulators following fractional flow approach assume incompressibility of fluid and matrix or consider only two phase flow (water and air, water and NAPL). However, in this study, mathematical governing equations were developed for fully compressible three-phase flow using fractional flow based approach. Also, fully compressible multiphase flow simulator (CMPS) considering compressibilities of matrix and fluid was developed using the mathematical governing equations. In order to verify CMPS, the CMPS were compared with analytical solution and the existing multiphase flow simulator, MPS, which had been developed for simulating incompressible multiphase flow (Suk and Yeh 2007; Suk and Yeh 2008). According to the results, solutions of CMPS and MPS and analytical solutions are well matched each other. Thus, it is found that CMPS has the capability of simulating compressible three phase flow phenomena assuming compressibilities of fluids and matrix.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.83-90
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• 2016

Ramjet mode combustion test was performed for a dual-mode ramjet engine model. The engine model consists of an air intake, a combustor and a nozzle. The combustor in the model has a large backward-facing step, designed to be used as a part of a rocket-based combined cycle engine. The test was performed at the flight speed of Mach 5 and the altitude of 24 km. Strong combustion was established only when the fuel was injected from both of the bottom-side and cowl-side wall. When the total fuel stoichiometric ratio was 1.0, distributed as 0.5 on the cowl side and 0.5 on the bottom side, the flow became subsonic at some portion in the combustor by thermal choking, i.e., ramjet mode was established for this condition.

• Fire Science and Engineering
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• v.23 no.5
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• pp.143-152
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• 2009

The numerical analyses for each single simplified shaft with three type openings were carried out by using computational fluid dynamics model for the calculation of the pressure difference and the location of the neutral plane and the visualization of stack effect. As the height of shaft heighten, the pressure difference of stack effect is much deviated against the theoretical value. For the Type A models shorter than 30 m height of shaft and the Type B models longer than 30m, the simulation results for the location of the neutral plane are well agreed to the theoretical values with 5% less deviations just after the beginning of simulation (t = 10s). For the Type B models longer than 30m with multiple openings, therefore, it is possible to calculate the location of the neutral plane by using a CFD model. The phenomenon of the air flow of stack effect can be easily understood with the visualization of stack effect.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.717-722
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• 2010

Supersonic/Hypersonic wind tunnel is a facility which is intended to test and to observe the physical phenomena around a model by creating supersonic flow in the test section. In designing an airplane, the wind tunnel test is demanded to analyzing aerodynamic characteristics of the model without making a prototype. In this research, the model aerodynamic facility(MAF) is modified for the purpose of increasing running time and its functionality. New pneumatic valves for remote control was installed for safety requirement, and new air tanks was installed on MAF as well. A pipe system is also modified to use those new valves and tanks, and the ceiling and side glasses of the test section are switched to ones with the larger surface area. After the MAF modification, a test is performed at Mach 2, 3 and 4. In this test, shadow graph technique, one of the flow visualization methods, is used to visualize supersonic flow field. The pressure in the settling chamber and working section at Mach 2, 3 and 4 was measured in each case. As a result, the possible model size and running time are obtained.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.18-24
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• 2017

Appropriate selection of the starter is essential for successful starting of the gas-turbine engine. Thus, aerodynamic drag during starting phase should be analyzed to assess the feasibility of the starter. In this paper, aerodynamic drag is modeled based on the speed profile from the engine coast down test, and it is scaled with respect to the target engine by comparing the compressor load. Afterward, the govern equation of the starting phase is developed with the torque model of the starter, and the design scheme to select the feasible starter will be finally suggested. The proposed model of starting phase will be useful to perform a preliminary design of the starting system of the gas-turbine engine.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.368-373
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• 2015

As a preliminary study for the development of the gas fueled marine engine, prediction of indicated performances was carried out for a spark-ignition engine using commercial software, GT-POWER. The optimized models through a previous study were applied for the simulation of the intake and exhaust systems in a SI engine. The Spark-Ignition Wiebe model was used to calculate the burn rate in the cylinders and the modified Woschni model was used to calculate the heat transfer to the walls. The predicted performances, such as air delivery, cylinder pressures and indicated mean effective pressures under a range of operating conditions showed good agreement with the experiments.