• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.35-41
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• 2003

Propagation speeds of turbulent premixed flames have been measured in a pulsed-flame flow reactor which generates flames propagating in nearly isotropic turbulent flow field with U'/$S_L$ ranging from 1.2 to 5.3. The measurement involved a high-speed digital imaging at 1000 frames/second to capture the flame propagation motion. In addition to the flame speed measurements, flame perimeter ratio was measured for comparison. The observed flame propagation speed is high ranging from 5 to 20 times the laminar flame speed for the range of U'/$S_L$. The flames observed at extreme equivalence ratios exhibit intermittent propagation in that only a small fraction of ignited flame kernel resulted in full propagation of the flame. Also, at low equivalence ratios the flame speed decreased substantially even at high turbulence intensities.

• 한국소음진동공학회논문집
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• 제21권10호
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• pp.883-889
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• 2011

The brand sound of vehicle diesel engine is recently one of the important advantage strategies in the automotive company. Because various noise components masked under high frequency level can be audible in quieter driving situation. Many researches have been carried out for subjective and objective assessments on vehicle sounds and noises. In particular, the interior sound quality has been one of research fields that can give high quality feature to vehicle products. Vehicle interior noise above 500 Hz is usually controlled by sound package parts. The materials and geometries of sound package parts directly affect on this high frequency noise. This paper describes the sound quality evaluation method for the vehicle diesel engine noise to establish objective criteria for sound quality assessment. Considering the sensitivity of human hearing to impulsive sounds such as diesel noise, the human auditory mechanism was simulated by introducing temporal masking in the time domain. Furthermore, each of the human auditory organs was simulated by computer codes, providing reasonable analytical explanations of typical human hearing responses to diesel noise. This method finally provides the sound quality index of vehicle diesel engine noise that includes high frequency intermittent offensive sounds caused by impacting excitations of combustion and piston slap.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2866-2877
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• 2021

The complex coupling relationship between liquid sodium and concrete materials affects both the sodium fire characteristics and concrete properties through heat and chemical erosion. In this study, experiments on direct and indirect (separated by a steel plate) contact of the columnar sodium fire with the concrete surface were performed. It was found that the combustion efficiency of liquid sodium in direct contact with concrete was significantly enhanced and accompanied by intermittent explosions and splashing of small concrete fragments. The sodium fire on the surface of the concrete considerably increased the internal temperature, pore size, and distribution density of the concrete. In addition, the depth of influence on the loosening of the concrete structure was also greatly extended. The contact of liquid sodium with the concrete substantially affected its permeability resistance. The water absorption of the concrete surface was increased by more than 70% when liquid sodium directly impacted the bare concrete surface. However, the change in water absorption in the centre of the concrete was primarily affected by the duration of the external heat.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.73-80
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• 2002

Dimethyl ether (DM) is one of the most attractive alternative fuel far compression ignition engine. Its main advantage in diesel engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the intrinsic properties of DME. Experimental study of DME and conventional diesel spray employing a common-rail type fuel injection system with a 5-holes sac type injector (hole diameter 0.168 ㎜/hole) was performed in a high pressure chamber pressurized with nitrogen gas. A CCD camera was employed to capture time series of spray images followed by spray cone angles and penetrations of DME were characterized and compared with those of diesel. Under atmospheric pressure condition, regardless of injection pressure, spray cone angles of the DME were wider than those of diesel and penetrations were shorter due to flash boiling effect. Tip of the DME spray was farmed in mushroom like shape at atmospheric chamber pressure but it was disappeared in higher chamber pressure. On the contrary, spray characteristics of the DME became similar to that of diesel under 3MPa of chamber pressure. Hole-to-hole variation of the DME spray was lower than that of diesel in both atmospheric and 3MPa chamber pressures. At 25MPa and 40MPa of DME injection pressures, regardless of chamber pressure, intermittent DME spray was observed. It was thought that vapor lock inside the injector was generated under the two injection pressures.

• 한국기후변화학회지
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• 제6권3호
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• pp.175-184
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• 2015

In this study GC and PAS were used to calculate $N_2O$ concentration of exhaust gas from Wood Chip combustion system. Fuel supplied to the incinerator was collected and analyzed and then the analysis result was used to calculate $N_2O$ emissions. Tier 3 and Tier 4 Method were used to calculate the $N_2O$ emissions. Plant's Specific emission factor of $N_2O$ by Tier 3 Method was 0.35 kg/TJ, while default emission factor of Wood?Wood Waste proposed by 2006 IPCC G/L was 4 kg/TJ. So the $N_2O$ emission factor of this study was 3.65 kg/TJ lower compared to the IPCC G/L. The total emissions calculated by Plant's specific emission factor was 4.22 kg during the measuring period, but by Tier 4 Method it was 7.88 kg. This difference in emissions was caused by the difference of continuous measuring and intermittent sampling. It would be necessary to apply continuous measuring to calculate emissions of $Non-CO_2$ gas whose the density distribution is relatively high. However currently, according to the target management guideline of greenhouse gas and energy, the continuous measuring method to calculate greenhouse gas emission is applied only to $CO_2$. Therefore for reliable greenhouse gas emission calculation it would be necessary to apply continuous measuring to calculate $Non-CO_2$ gas emission.

• 문화기술의 융합
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• 제8권3호
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• pp.493-499
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• 2022

본 논문은 제주도의 화산이 폭발 시에 얼마만한 속도로 폭발했으며, 폭발 후에 생기는 튜물러스와 한라산 중턱에서 폭발된 현무암이 바다까지 밀려온 결과를 보고한다. 현무암 지하 마그마가 약 절대온도 1000K로 지상의 중성대를 뚫고 1950m 상공에서 절대온도 1200K로 폭발하면서 나올 때의 속도에 대해 분석했다. 부력(浮力)에 의한 화염 기둥의 열기류인 Plume 화산 폭발로 인한 주변의 공기보다 연소가스의 밀도가 작아져 부력이 발생하고 상승 기류가 형성된다. 화염 기둥은 연속, 간헐, 부력 화염 영역으로 분류된다. 한라산(1950m) 화염 기둥의 속도는 상승한 최고점에서 낙하함으로 위치에너지가 운동에너지로 변환되어 유체흐름에 의해 이 두 식을 같게 놓아 풀면 화산 폭발 속도87.5m/s를 얻었다. 이때 마그마의 밀도는 온도에 반비례한다. 거문오름(456m)은 폭발 속도는 42.6m/s로 계산했다.

• 에너지공학
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• 제25권4호
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• pp.13-29
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• 2016

본 연구에서는 실제 난지 하수처리장에서 바이오가스를 연료로 사용하여 발전할 때, 가스엔진에서 발생하는 고장 사례에 대한 조사와 분석을 통해 바이오가스 플랜트의 주요 고장원인을 분석하고, 그 대책을 제시하였다. 바이오 가스엔진에 유입되는 바이오 가스 속의 황화수소와 수분 제거설비의 간헐적인 오작동으로 인한 수분이 바이오 가스엔진의 인터쿨러 부식을 초래하였다. 또한 바이오가스 속의 실록산이 이산화규소와 규산염 화합물을 형성하여 피스톤 표면 및 실린더라이너 내벽의 긁힘과 마모 등의 손상을 유발하였다. 연소실과 배기가스 설비에 부착된 물질들은 황화수소와 다른 불순물질이 결합한 것으로 분석되었다. 이러한 원인으로는 바이오 가스 속의 고함량(50ppm이상)의 황화수소가 탈황설비에 장기간 공급되었고, 탈황설비내 활성탄의 파과점 도달에 따른 제거효율 저하 때문에 황화수소가 엔진으로 유입됨으로써 발생한 것으로 사료된다. 또한, 황화수소는 흡착탑의 실록산 제거용 활성탄 기능을 저하시킴으로써 제거되지 않은 실록산 화합물이 엔진으로 유입되어 다양한 형태의 엔진고장을 유발한 것으로 판단된다. 따라서, 황화수소와 실록산, 수분은 바이오 가스엔진 고장의 주요 원인으로 볼 수 있으며, 이 중 황화수소는 고장을 일으키는 다른 물질과 반응하며, 전처리 공정에 중대한 영향을 미치는 물질로 볼 수 있다. 결과적으로, $H_2S$ 제거방법의 최적화가 안정적인 바이오 가스엔진 운영을 위한 필수적인 대책으로 사료된다.