• 한국항해항만학회지
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• 제48권2호
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• pp.125-136
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• 2024

This research presents an innovative integrated ethanol solid oxide fuel cell (SOFC) system designed for applications in marine vessels. The system incorporates an exhaust gas heat recovery mechanism. The high-temperature exhaust gas produced by the SOFC is efficiently recovered through a sequential process involving a gas turbine (GT), a regenerative system, steam Rankine cycles, and a waste heat boiler (WHB). A comprehensive thermodynamic analysis of this integrated SOFC-GT-SRC-WHB system was performed. A simulation of this proposed system was conducted using Aspen Hysys V12.1, and a genetic algorithm was employed to optimize the system parameters. Thermodynamic equations based on the first and second laws of thermodynamics were utilized to assess the system's performance. Additionally, the exergy destruction within the crucial system components was examined. The system is projected to achieve an energy efficiency of 58.44% and an exergy efficiency of 29.43%. Notably, the integrated high-temperature exhaust gas recovery systems contribute significantly, generating 1129.1 kW, which accounts for 22.9% of the total power generated. Furthermore, the waste heat boiler was designed to produce 900.8 kg/h of superheated vapor at 170 ℃ and 405 kP a, serving various onboard ship purposes, such as heating fuel oil and accommodations for seafarers and equipment.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.505-513
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• 2023

Hydrogen infrastructure is expanding. High-capacity hydrogen refueling stations offer advantages because they can refuel a variety of light and heavy-duty vehicles, and multi-port refueling technology is developing to reduce charging time for heavy-duty vehicles. In this study, we suggest directions to lower the risk by analyzing the risk factors for each process involved in the installation of a high-capacity multi-port hydrogen refueling station in Changwon city. We conducted both qualitative and quantitative risk assessments of the equipment to evaluate the station. A hazard and operability study was performed for qualitative risk assessment, and PHAST/SAFETI were used for quantitative risk assessment. Quantitative risk assessment was used to calculate the consequence analysis of the facility to ensure secure design prior to station development and to predict individual and societal risks in various scenarios. As a result, the station's risk level was determined to be as low as reasonably practicable.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.11-18
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• 2002

Residual gas fraction in an engine cylinder affects engine performance, efficiency and emission characteristics. With high residual gas fractions, a flame speed and maximum combustion temperature are decreased and these are deeply related with combustion stability especially at idle and NOx emission at relatively high engine load. In this work, the residual gas fraction was calculated by an engine simulation code, which was validated by the experimental data (cylinder pressure and emissions) obtained from 4-cyliner spark ignition engine. A comparison between experimental and computational calculation results was made. The residual gas is generated mostly at low engine speed by the larger pressure difference between the intake and exhaust port. As the valve overlap duration was increased, the amount of residual gas in the cylinder, the amount of HC emission in the exhaust gas and the variation of power output increased.

• 수산해양기술연구
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• 제56권3호
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• pp.230-237
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• 2020

In order to design a diesel engine system and predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. A gas flow analysis in three-dimensional (3D) format needs a high-resolution workstation and enormous time for analysis. Therefore, the method of characteristics (MOC) was used for a gas flow analysis with a fast calculation time and a low-resolution workstation. An experiment was conducted on a single cylinder diesel engine to measure pressure in cylinder, intake pipe and exhaust pipe. The one-dimensional (1D) gas flow was analyzed under the same conditions as the experiment. The engine speed, valve timing and compression ratio were the same conditions and the intake pressure was inputted as the experimental results. Bent pipe such as an exhaust port that cannot be realized in 1D was omitted. As results of validation, the cylinder pressure showed accuracy, but the exhaust pipe pressure exhibited inaccuracy. This is considered as an error caused by the failure to implement a bent pipe such as an exhaust port. When analyzed in 3D, calculation time required 61 hours more based on a model of this study. In the future, we intend to implement a bent pipe that cannot be realized in 1D using 3D and prepare a method to supplement reliability by using 1D-3D coupling.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1635-1646
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• 1998

The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.86-100
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• 1998

The impingement of the fuel spray on the wall within the combustion chamber in compact high-pressure injection engines and on the intake port wall in port-fuel-inje- ction type engines is unavoidable. It is important to understand the characteristics of impinging spray because it influences on the rate of fuel evaporation and droplet distrib- ution etc. In this study, the numerical study for the characteristics of spray/wall interaction is performed to test the applicability and reliability of spray/wall impingement models. The impingement models used are stick model, reflect model, jet model and Watkins and Park's model. The head of wall-jet eminating radilly outward from the spray impingement site contains a vortex. Small droplets are deflected away from the wall by the stagnation flow field and the gas wall-jet flow. While the larger droplets with correspondingly higher momentum are impinged on the wall surface and them are moved along the wall and are rolled up by wall-jet vortex. Using the Watkins and Park's model the predicted results show the most reasonable trend. The rate of increase of spread and the height of the developing wall-spray is predicted to decrease with increased ambient pressure(gas density).

• 설비공학논문집
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• 제14권8호
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• pp.648-655
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• 2002

For a discharge system of rotary compressor, analytical investigation on the discharge gas pulsation has been carried out. With the aid of four pole theory, acoustic impedance of the discharge system composed of muffler and cavities on both sides of motor with gas passages between them can be calculated using discrete acoustic elements described by transfer matrices, yielding the relationship between discharge mass flow rate and gas pulsation at the discharge port. This method of predicting the gas pulsation was validated by measurement data. Effects of change in discharge muffler geometries on the gas pulsation also were investigated, demonstrating that this method can be used for muffler design.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2006년도 추계학술발표논문집
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• pp.99-101
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• 2006

As the industry of 21C has been developed, the gas industry has grown and it has not only the convenience but also the riskiness for using. Therefore, we designed the outlet to prevent from collapse of booth by the explosion pressure in installing the explosion booth for test in order to train safety supervisors the riskiness of gas explosion. The outlet was designed based on the exhaust model of NFPA 68.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1457-1469
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• 2002

This paper is the first of several companion papers, which investigate axial stratification process and its effects in an Sl engine. The axial stratification is very sophisticate phenomenon, which results from combination of fuel injection, port and in-cylinder flow and mixing. Because of the inherent unsteady condition in the reciprocating engine, it Is impossible to understand the mechanism through the analytical method. In this paper, the ports were characterized by swir and tumble number in steady flow bench test. After this, lean misfire limit of the engines, which had different port characteristic, were investigated as a function of swirl ratio and injection timing for confirming the existence of stratification. In addition, gas fuel was used for verifying whether this phenomenon depends on bulk air motion of cylinder or on evaporation of fuel. High-speed gas sampling and analysis was also performed to estimate stratification charging effect. The results show that the AFR at the spark plug and LML are very closely related and the AFR is the results of bulk air motion.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.113-118
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• 2008

For a R134a rotary vane compressor used for car air conditioners, characteristics of gas compression and oil supply have been studied. The compressor model under investigation has the low volume ratio of suction to discharge volumes so that there occur flow reversal from discharge port to compression chamber as the leading vane passes over the discharge port. As a result, the volumetric and adiabatic efficiencies turn out to be relatively low compared to other types of displacement compressors. Oil supply mechanism has been comprehended for mathematical modeling and oil flow rate has been calculated for the individual oil passages. This study on the gas compression and oil supply of a rotary vane compressor can be applied to a future design practice on a similar type of compressor.