• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2529-2534
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• 2000

Torsional vibration analysis in a large two -stroke low speed diesel engine and generator system for stationary power plants is performed to verify that the vibration characteristics of shafting system meet design requirements. Our own developed S/W is employed for the analysis, whose results are evaluated comparing with measurements. Vibration analysis results of the system are presented according to the change of loading(unload, 100%load, 110% load) and operating(mis-firing, uneven firing) conditions of the stationary power plants.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.80-89
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• 1998

The residual gas in an spark-ignition engine is one of important factors on emissions and performance such as combustion stability. With high residual gas fractions, 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. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. In the present study, the quantitative measurement technique of residual gas fraction was studied by using Fast Response Flame Ionization Detector(FRFID). The measuring technique and model for estimation of residual gas fraction were reported in this paper. By the assuming that the raw signal from FRFID saturates with the same slope for firing and misfiring cycle, in-cylinder hydrocarbon(HC) concentration can be estimated. Residual gas fraction can be obtained from the in-cylinder HC concentration measured at firing and motoring condition. The developed measurement and calibration procedure were applied to the limited engine operating and design condition such as intake manifold pressure and valve overlap. The results show relevant trends by comparing those from previous studies.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.68-75
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• 2011

This study simulated the effect of steam injection on the performance and operation of a gas turbine combined heat and power (CHP) system. A commercial simple cycle gas turbine was analyzed. A full off-design analysis was carried out to investigate the variations in not only engine performance but also the operating characteristics of the compressor caused by steam injection. Variation in engine performance and operation characteristics according to various operation modes were examined. First, the impact of full steam injection was investigated. Then, operations aiming to guarantee a minimum compressor surge margin, such as under-firing and partial steam injection, were investigated. The former and latter were turned out to be relatively superior to each other in terms of power and efficiency, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.790-798
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• 2007

An experimental study was performed to investigate the effects of mixing quality, inlet pressure, nozzle diameter on CO, NO emission and radiation characteristics in porous ceramic fiber radiant burners. Observations of combustion characteristics occurring inside the burner system which was insulated fiber mat, were investigated by measuring emission and radiation characteristics. Combustion was achieved at the firing rate of $88{\sim}99\;kcal/hr$, inlet pressure of $100{\sim}250mmH_2O$. The fiber burner exhibit significant both spectral intensity peaks in the bands at $2.5{\mu}m\;and\;4.0{\mu}m$ relatively. There is a small difference in the variable mixing tube. However spectral intensity increased with the firing rate. CO emissions were found to be strongly dependent on the operating conditions. There was a tendency that CO concentration increased as the firing rate increases. the reason for rise of CO concentration is that is becomes it the relatively rich condition. Relatively low NO emission was observed for the whole operating range. The NO concentration is maximal at the firing rate of approximately 2850 kcal/hr and an air ratio of about 1.

• Journal of the Korean Society of Combustion
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• v.21 no.4
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• pp.30-38
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• 2016

Flame structure of co-firing coal and palm kernel shell (PKS) was investigated in a pulverized coal swirl burner by particle image velocimetry (PIV). The pulverized coal swirl flame is operated with a PKS blending ratio of 10%, 20%, and 30%. For all operating conditions, flame structures such as internal recirculation zone (IRZ), outer recirculation zone (ORZ), and exhaust tube vortex (ETV) were observed. In the center of flame, the strong velocity gradient is occurred at the stagnation point where the volatile gas combustion actively takes place and the acceleration is increased with higher PKS blending ratio. OH radical shows the burned gas region at the stagnation point and shear layer between IRZ and ORZ. In addition, OH radical intensity increases for a co-firing condition because of high volatile matter from PKS. Because the volatile gas combustion takes place at lower temperature, co-firing condition (more than 20%) leads to oxygen deficiency and reduces the combustibility of coal particle near the burner. Therefore, increasing PKS blending ratio leads to higher OH radical intensity and lower temperature.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.319-328
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• 2006

This paper presents a method for analysis of the mechanical behavior of a crankshaft in a four-cylinder internal combustion engine. The purpose of the analysis was to study the characteristics of the shaft in which the pin and arm parts were assumed to have a uniform section in order to simplify the modal analysis. The results of natural frequency transfer function and mode shape were compared with those obtained by experimental work. The results obtained from the comparison showed a good agreement with each other and consequently verified the analysis model. Furthermore, a prediction of crankshaft characteristics under the firing condition, by using the model, was performed. This study describes a new method for analyzing the dynamic behavior of crankshaft vibrations in the frequency domain based on the initial firing stages. The new method used RMS values to calculate the energy at each bearing journal and counter weight shape modification under the operating conditions.

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.1-7
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• 2001

FGR is one of the most widely used methods of NOx reduction in the combustion process. It was investigated the effect of FGR, excess air ratio, peak temperature and firing rate on NOx emission in this study. 100kW burner and LNG were adopted in this experiment. NOx emission was notably decreased with the increase of FGR, however CO emission was also drastically increased in the 25% FGR. And excess air ratio, peak temperature and firing rate did not affect the NOx emission appreciably in the normal operating condition.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.176-183
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• 2007

An experimental study was performed to investigate the effects of mixing quality, inlet pressure, nozzle diameter on CO emission and radiation characteristics in porous ceramic fiber radiant burners. Observations of combustion characteristics occurring inside the burner system which was insulated fiber mat, were investigated by measuring temperature, CO emission and radiation characteristics. Combustion was achieved at the firing rate of $88{\sim}99$ kcal/hr, inlet pressure of $100{\sim}250$mm$H_2O$. CO emissions were found to be strongly dependent on the operating conditions. There was a tendency that CO concentration increased as the firing rate increases. The reason for rise of CO concentration is that it becomes the relatively rich condition. The fiber burner exhibit significant both spectral intensity peaks in the bands at 2.5${\mu}m$ and 4.0${\mu}m$ relatively, There is a small difference in the variable mixing tube. However spectral intensity increased with the firing rate.

• Tribology and Lubricants
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• v.35 no.4
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• pp.244-266
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• 2019

The purpose of this study is to estimate the wear volumes of engine journal bearings operating at variable angular velocity of a shaft in the beginning of firing start-up cycle. To do this, first we find the potential region of wear scar on engine journal bearings where the applied bearing load and crank shaft velocity are variable. The potential wear regions are discovered by finding minimum oil film thickness at every crank angle existing below most oil film thickness scaring wear (MOFTSW) obtained based on the concept of the centerline average surface roughness. Then we calculate the wear volume from the wear depth and two wear angles decided by the magnitude of each film thickness lower than MOFTSW at every crank angle. The results show that the expected wear region is located at a few bearing angles after and/or behind the upper center of a big-end bearing and the lower center of a main bearing. And the real wear region is similar to the estimated wear region. Further we find that the wear scar on an engine journal bearing may occur at re-starting time after switch-off of a start motor especially under the condition of high oil temperature.

• Tribology and Lubricants
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• v.34 no.4
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.