• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.378-386
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• 2019

In the present paper we report the calculation results of operation energy consumption for dissolved ions concentration technologies using vacuum evaporation (VE) and hydrate formation. Calculations were conducted assuming the tenfold concentration of saline water (0.35 wt% NaCl solution) of 1 mol/s at room temperature and atmospheric pressure employing vacuum evaporation at $69^{\circ}C$ and 30 kPa and hydrate-based concentration using $CH_4$, $CO_2$ and $SF_6$ as guest molecules. Operation energy consumption of VE-based concentration resulted in 47 kJ/mol, whereas those of hydrate-based concentration were 43, 32, and 28 kJ/mol for $CH_4$, $CO_2$ and $SF_6$ hydrates, respectively. We observe that hydrate-based concentration can a competitive option for dissolved ions recovery from energy consumption standpoint. However, the selection of guest gas is very critical, since it accordingly determines the hydration number, the hydrate formation energy, gas compression energy, etc. The selection of guest gas, separation of concentrated brine and water phases, and the enhancement of hydrate formation rate are the key factors for the commercialization of hydrated-based technology for concentrating dissolved ions.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.55-63
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• 2021

In this study, a numerical methodology is proposed for evaluating valve flow noise in a pipe conveying high pressure gas, and the effects of perforated plates on reduction of such valve flow noise are quantitatively analyzed. First, high-accurate unsteady compressible Large Eddy Simulation techniques are utilized to predict flow and flow noise by a valve in a high-pressure pipe. The validity of the numerical result is confirmed by comparing the predicted wall pressure spectrum with the measured one. Next, the acoustic power of downstream-propagating acoustic waves due to the valve flow is analyzed using an acoustic power formula for acoustic waves propagating on mean flow in a pipe. Based on the analysis results, perforated plates are designed and installed downstream of the valve to suppress the valve flow noise and the acoustic power of downstream-going acoustic waves is predicted by using the same numerical procedure. The reduction by 9.5 dB is confirmed by comparing the predicted result with that of the existing system. Based on these results, the current numerical methodology is expected to be used to reduce valve flow noise in an existing system as well as in a design stage.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.60-67
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• 2021

This study presented techno-economic analysis of a 500 MWe oxy-coal power plant with CO2 capture. The power plant included a circulating fluidized-bed (CFB), ultra-supercritical steam turbine, flue gas conditioning (FGC), air separation unit (ASU), and CO2 processing unit (CPU). The dry flue gas recirculation (FGR) was used to control the combustion temperature of CFB. One FGR heat exchanger, one heat exchanger for N2 stream exiting ASU, and a heat recovery from CPU compressor were considered to enhance heat efficiency. The decrease in the temperature difference (ΔT) of the FGR heat exchanger that means the increase in heat recovery from flue gas enhanced the electricity and exergy efficiencies. The annual cost including the FGR heat exchanger and FGC cooling water was minimized at ΔT = 10 ℃, where the electricity efficiency, total capital cost, total production cost, and return on investment were 39%, 1371 M$, 90 M$, and 7%/y, respectively.

• Journal of Convergence for Information Technology
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• v.11 no.7
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• pp.111-117
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• 2021

This research work is to suggest the experimental results capable of solving an initial unsuitability of combustion and environment in a constant volume combustion chamber by using LFG(Land Fill Gas) which consists of 40% CO₂ and 60% CH₄. The experimental condition is set as 0.9~1.6 of air-fuel ratio, 3bar of combustion pressure, 25℃ of room temperature, methane for using gas, and 2.5~4.5 of Pre-chamber hole sizes. As a result, it can be seen that diffusion of initial flame is significantly increased by M3.0 model comparing with other one. The reason for the characteristics is that orifice effect is extremely improved by 0.9, 1.0, and 1.2 of air-fuel ratio comparing with other one. Consequently, this experiment is shown that M3.0 model is partially capable of improving combustion performance than a conventional ignition plug in case of applying to LFG with Pre-chamber design.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.2
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• pp.130-135
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• 2013

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the working speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a oil cooler to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the oil cooler system. In this paper, the compressor's speed are controlled to keep reference value of temperature at oil outlet. The precision processing of a machine tool is required for an oil cooler guaranteeing ${\pm}0.1^{\circ}C$ temperature control. But the oil cooler with precision temperature control is expensive. Therefore in this paper, instead of a on/off(relay) control method, a PID and phase angle electric power control method is proposed for the precision control of an oil cooler. The proposed controller is implemented and tested at the temperature of $23^{\circ}C$, $24^{\circ}C$ and $25^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.179-188
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• 1990

The characteristic of volumetric efficiency considering gas exchange process in a reciprocating engine is presented in this paper. The characteristic method is used for solving gas exchange problems of engine system in theoretical studies. The validity of the simulation is investigated by a comparison with the results obtained by the experiment which have been performed on the practical 4-cycle, 4-cylinder gasoline engine. The relationship between the volumetric efficiency and the intake pressure variation according to configuration of intake pipe, position of branch point, valve timing, compression ratio is clarified through simulation and experiment. The results predicted by the simulation are found to be in approximate agreement with those obtained by the experiment.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.118-127
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• 2004

The purpose of this study is experimentally to analyze that intake port swirl, injection system and turbocharger have an effect on the engine performance and the emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement 16.7ι, and to suggest the improvement of engine performance. Generally to enhance engine power, TCI diesel engine is put to practically use turbo-charged intercoler in order to increase boost efficiency which is cooled boost air. As results of considering the factors of the intake port of swirl ratio 2.25, compression ratio 17.5, re-entrant 8.5$^{\circ}$ combustion bowl, nozzle hole diameter ${\Phi}$0.33*3+${\Phi}$0.35*2, nozzle protrusion 3.18mm, injection timing BTDC 12$^{\circ}$CA and turbo charger (compressor 0.6A/R+46Trim, turbine 1.0A/R+57Trim) is the best in the full range of operating in the engine performance and the exhaust characteristics of NO$\_$x/ concentration. Therefore their factors are appropriated as intake system, injection and turbocharger system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.552-560
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• 2014

Pulse Detonation Engine(PDE) has been investigated as a next generation propulsion system with the advantages of the higher thermal efficiency by the compression effect and the wide operation ranges from zero speed at ground. In the present study, an efficient theoretical PDE performance prediction program was developed for realistic propellants based on the Endo's theory combining the Chapman-Jouguet detonation theory and expansion process of burnt gas in a constant area tube. The program was validated through the comparison with the experimental data obtained by a ballistic pendulum measurement. PDE performance analyses were carried out for various hydrocarbon fuels and oxidizer compositions by changing the mixture equivalence ratio and initial conditions. Theoretical PDE performance database could be established as a result of the analyses.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.105-113
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• 2010

In this study, a feasibility test of liquid petroleum gas (LPG) compression ignition (CI) engine has been carried out to study the effectiveness of cetane enhancing additive: Di-tertiary-butyl peroxide (DTBP). Performance and emissions characteristics of a CI engine fuelled with DTBP blended LPG fuel were examined. Also, the effect of EGR (exhaust gas recirculation) on the combustion and emissions characteristics has been investigated. Results showed that stable engine operation over a wide range of the engine loads was possible. Exhaust emissions measurements showed that hydrocarbon were decreased with the blended fuel at enhancing cetane number. Furthermore, the combustion stability of LPG with a cetane number improver was equivalent to that of commercial Diesel fuel. Increasing the EGR rate leads to deteriorate the IMEP (indicated mean effective pressure) and increase the ignition delay. It was found that the exhaust emissions with the EGR resulted in a very large reduction in nitrogen oxides at the expense of higher THC and CO emissions. Considering the results of engine performance and exhaust emissions, LPG blended fuel of enhancing cetane number could be used as an alternative fuel for diesel in a CI engine.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.625-630
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• 2010

This study aims to examine the possible use of heavy oil fly ash as raw material for deodorization panels by adding additives such as activated carbon and diatomite during deodorization panel manufacturing process and improving the performance of formaldehyde and toluene elimination.The recycled heavy oil flyash deodorization panel to be used either of them as additives removed more than 93% of formaldehyde and more than 97% of toluen but the compressive strength was decreased 27 to 63%. In an experiment to be used both additives, Whereas, the panel to include activated carbon 5% and diatomite 5% removed 84% against formaldehyde and 96% against toluen, and the compressive strength was increased 32% better than standard panel. Therefore it could be confirmed that the recycled heavy oil flyash deodorization panel is increased the compressive strength and the removal efficiency against harmful chemical substances by using the additives mixture.