• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.19-28
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• 2014

Firing test of solid rocket motor with pintle-technology carried out and the measured pressure-time curve was compared with the values predicted by the internal ballistic and performance analysis. Without baffle, the measured combustion chamber pressure was similar with the predicted pressure at the beginning of combustion, but gradual increase in pressure, which was unexpected with the end-burning grain of which burning area is constant, was observed. A baffle was inserted to make uniform flow over the pintle. Unlike the thruster without baffle, the measured combustion chamber pressure was 1.4 times higher than the predicted value. Through the CFD simulation, 10% of total pressure loss of the flow was observed from combustion chamber to nozzle throat when the baffle was inserted. The measured pressure with baffle was predicted well by considering the total pressure loss in the internal ballistic modelling and performance analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.215-218
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• 2005

An optimal fuel manifold is suggested to improve the cooling performance of injector face plate. The cooling performance at the center area of the injector face plate is to be augmented while the spatial injection uniformity is maintained. The comparison of the cooling performance of 7 candidates gives the conclusion that the dividing plate from 2-3 injector row to 9-10 injector row is an optimal. The maximum face plate temperature decreases by $27\%$ while the injection uniformity is close to that of the original design. The pressure drop in the fuel manifold of the optimal design is also same as the original design.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.3
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• pp.92-100
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• 2005

An optimal fuel manifold is suggested to improve the cooling performance of an injector face plate. The cooling performance at the center area of the injector face plate is to be augmented while the spatial injection uniformity is maintained. The comparison of the cooling performance of f candidates gives the conclusion that the dividing plate from 2-3 injector .ow to 9-10 injector. row is an optimal. The maximum face plate temperature decreases by 27$\%$ while the injection uniformity is close to that of the original design. The pressure drop in the fuel manifold of the optimal design is also same as the original design.

• Journal of the Korean Institute of Gas
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• v.15 no.1
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• pp.40-45
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• 2011

During process operations, overpressure can be caused by operator's error or malfunction of the device. To prevent this overpressure, gas was released through blowdown system. Because most of released gases are the hydrocarbon mixture and have flammable and toxic properties, the gas is released after burning in flare stack. The increase of scale and complexity of plant requires higher or additional flare stacks. This study tried to solve this problem through flare gas recovery system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.120-125
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• 2002

In the preceding tests using the KSR-III Sub.(I) engines, it was observed that the heat resistant capability of the engines was not enough for the mission. So Sub.(I) Mod. engines were designed and tested. The Sub.(I) Mod. engines have three major design parameters - the arrangement of main injectors, the impinging angle of main injectors and thermal barrier coating. More than twenty experiments were carried on to evaluate engine performance and heat resistance capability with respect to design parameters. In this study, the test results are introduced. Analysing the result of Sub.(I) engine tests, it is found that decreasing the impinging angle, adopting the H-type arrangement(rather than radial type arrangement) and adopting the thermal barrier coating can increase heat resistance capacity substantially. Also, engine performance evaluation is conducted using specific impulse and characteristic velocity parameter. The results show that the performance variation is small(about 5%) and the performance is better in the case of radial arrangement. It is suspected that these phenomena are caused by the change of flame structure atomization mixing characteristic of sprays and the distortion of recirculation zone. Also from the low frequency instability point of view, it is observed that reducing the impinging angle and adopting the H type arrangement can increase the instability characteristics.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.439-449
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• 2021

The recent reduction in greenhouse gases, interest in environmental pollution such as low-carbon emission policies is increasing. Accordingly, the penetration rate of eco-friendly vehicles, including hydrogen battery vehicles capable of reducing carbon emission, is increasing, and thus it is required for disaster prevention and safety-related measures. In this study, the degree of risk for the concentration distribution of hydrogen when leaking hydrogen fuel vehicles according to ventilation conditions was analyzed through numerical analysis, limited to places in parking lots. As a result, when only one hydrogen tank was released, the combustible volume ratio of hydrogen in the underground parking lot was up to 8.6%, and as ventilation continued, the volume ratio of combustible hydrogen decreased to less than 1% after 150 seconds, indicating that mechanical ventilation is essential. In the case of simultaneous release or stage release of three hydrogen tanks, the final combustible volume ratio of hydrogen is similar, but the increase in the combustible volume ratio of hydrogen in the early stage of release is low, and further research is expected.

• Clean Technology
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• v.27 no.3
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• pp.269-274
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• 2021

Bioenergy is generally considered to be one of the options for pursuing carbon neutrality. However, for a period of time, combustion of harvested plant biomass inevitably causes more carbon dioxide in the atmosphere than combustion of fossil fuels. This paper proposes a method that predicts and minimizes the total amount and payback period of this carbon debt. As a case study, a carbon cycle impact assessment was performed for immediate switching of the currently used fossil fuels to biomass. This work points out a fundamental vulnerability in the concept of carbon neutrality. As an action plan for the sustainability of bioenergy, formulas for afforestation proportional to the decrease in the forest area and surplus harvest proportional to the increase in the forest mass are proposed. The results of optimization indicate that the carbon debt payback period is about 70 years, and the carbon dioxide in the atmosphere increases by more than 50% at a maximum and 3% at a steady state. These are theoretically predicted best results, which are expected to be worse in reality. Therefore, biomass is not truly carbon neutral, and it is inappropriate as an energy source alternative to fossil fuels. The method proposed in this work is expected to be able to contribute to the approach to carbon neutrality by minimizing present and future carbon debt of the bioenergy that is already in use.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2682-2688
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• 2012

In this paper, we design and implement a electric current controller for ignition coil to measure the amount of current and to supply the additional current under vehicle driving conditions in spark ignition engines. The proposed controller can provide the stable current and prevent the overcurrent by measuring the amperage of primary ignition in real time. Also it enhances the performance of vehicle engine by controling the amount of ignition energy that make power increase and fuel burn more completely. The power and torque of the normal vehicle is evaluated as performance index for the experimental validation of the control module. The experimental results using dynamometer equipment show that after control module-mounted elevates the average of 10% more in both power and torque compared with before module-mounted.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.642-650
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• 2020

In general, the circulation path of the fluidized particles in a CFB (Circulating Fluidized Bed) boiler is such that the particles entrained from a combustor are collected by a cyclone and recirculated to the combustor via a sealpot which is one of non-mechanical valves. However, when a fluidized bed heat exchanger (FBHE) is installed to additionally absorb heat from the fluidized particles, some particles in the sealpot pass through the FBHE and then flow into the combustor. At this time, in the FBHE operated in the bubbling fluidization regime, if the heat flow is not evenly distributed by poor mixing of the hot particles (800~950 ℃) flowing in from the sealpot, the heat exchanger tubes would be locally heated and then damaged, and the agglomeration of particles could also occur by formation of hot spot. This may affect the stable operation of the circulating fluidized bed. In this study, the unevenness of heat flow arising from structural problems of the FBHE of the domestic D-CFB boiler was found through the operating data analysis and the CPFD (Computational Particle Fluid Dynamics) simulation using Barracuda VR. Actually, the temperature of the heat exchanger tubes in the FBHE showed the closest correlation with the change in particle temperature of the sealpot. It was also found that the non-uniformity of the heat flow was caused by channeling of hot particles flowing in from the sealpot. However, it was difficult to eliminate the non-uniformity even though the fluidizing velocity of the FBHE was increased enough to fluidize hot particles vigorously. When the premixing zone for hot particles flowing in from the sealpot is installed and when the structure is changed through the symmetrization of the FBHE discharge line for particles reflowing into the combustor, the particle mixing and the uniformity of heat flow were found to be increased considerably. Therefore, it could be suggested that the structural modification of the FBHE, related to premixing and symmetric flow of hot particles, is an alternative to reduce the non-uniformity of the heat flow and to minimize the poor particle mixing.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.1
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• pp.11-19
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• 2014

A study on combustion characteristic and evaluation of cost benefit were carried out using dried sewage sludge to evaluate co-combustion with coal in a coal-fired power plant. In the result of proximate analysis, sewage sludge has 78.09%, 79.65% of moisture content in A STP(Sewage Treatment Plant) and B STP, respectively. The dried sewage sludges show 0.12, 0.14 of fuel ratio value, respectively and over 30,000kcal/kg of combustible index. It means that the dried sewage sludges needs to reform from the results of fuel ratio and combustible index. As a results of the economical benefit evaluation of dried sewage sludge, about 73.4 million won through using the dried sewage sludges instead of coal and 56.4 million won through REC(Renewable Energy Certificate) cost were saved, respectively. On the other hand, it occurs 4.2 million won of additional cost related to ash disposal and 2.6 million won of investment/operation cost for co-combustion facility. In conclusion, co-combustion of dried sewage sludges with coal in a coal-fired power plant saves about 123 million won. However, it needs to consider for power supply to produce dried sewage sludges and opportunity cost for environmental pollution and so on to evaluate more reasonable benefit of co-combustion.