• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.345-348
• /
• 2009

Maintaining proper membrane humidity is crucial to ensure optimal operation of a PEMFC system. A gas-to-gas membrane humidifier is popular technology for external humidification of PEMFC reactant gases. Characteristics of heat and water transfer in shell-and-tube Nafion membrane humidifiers has been experimentally investigated for various dry side inlet temperature of membrane humidifier. The results show that heat flux decreases linearly with dry side inlet temperature of membrane humidifier. The water flux through the membrane varies nonlinearly with the temperature elevation.

• 설비공학논문집
• /
• 제15권8호
• /
• pp.690-696
• /
• 2003

This paper presents the heat recovery performance of water fluidized-bed heat exchanger. Temperature and humidity ratio of waste gas are considered as important parameters in this study. Therefore, the heat recovery rate through water fluidized-bed heat exchanger for exhaust gases with various temperatures and humidity ratios can be estimated from the results of this study. Mass flow ratio (the ratio of mass flow rate of water to that of gas) and temperature of inlet water are also considered as important operating variables. Increase of heat recovery rate can be obtained through either high mass flow ratio or low temperature of inlet water with resultant low recovered temperature. The heat recovery performance with the mass flow ratio of about up to 10 has been investigated. The effect of number of stages of water fluidized-bed on the heat recovery performance has been also examined in this study.

• 한국연소학회지
• /
• 제20권3호
• /
• pp.8-12
• /
• 2015

The CO reduction characteristics of hot air stream diluted with exhaust gas in a perfectly stirred reactor (PSR) were investigated numerically. The dilution ratio ($\Omega$), inlet temperature ($T_{in}$), and residence time ($\tau$) were considered as parameters to investigate the effects of those on the emission indices for CO and $CO_2$ (EICO and $EICO_2$). The roles of dominant reactions and the production rates of major species were analyzed. It was found from the EICO trend that the supplied CO in the air stream was consumed. The EICO increased negatively with $T_{in}$ at fixed $\tau$ regardless of $\Omega$. However, the magnitude of EICO and minimum inlet temperature for CO reduction showed complicated trend according to the variation of $\tau$. It was identified that the OH radical, generated from the reactions, $O_2+H{\leftrightarrow}O+OH$ and $2OH{\leftrightarrow}H+H_2O$, affected the CO reduction by the reaction, $CO+OH{\leftrightarrow}H+CO_2$. However, the CO emission ratio increased at sufficiently high inlet temperature range due to the thermal dissociation of $CO_2$.

• 오토저널
• /
• 제8권1호
• /
• pp.62-74
• /
• 1986

The simulation of power cycle and unsteady gas exchange processes in the inlet and exhaust systems of the single-cylinder 2-stroke cycle compression ignition engine was studied in this paper. In power cycle process, the single-zone model proposed by Whitehouse and Way was used, and the convective and radiative heat transfer from cylinder contents to surroundings was considered. To solve the equations for gas exchange process, the generalized method of characteristics including area change, friction, heat transfer and entropy gradients was used. Also with the path line calculation, the entropy change along the path line and the variation of specific heat due to the change of temperature and the composition of cylinder gas were considered. As a result of the simulation, the change of pressure and temperature in the cylinder against the crank angle, the rate of net heat release, and the change of properties at each point in the inlet and exhaust pipe against the crank angle were obtained. The engine performances under various operating conditions were also calculated.

• 대한기계학회논문집B
• /
• 제31권6호
• /
• pp.514-521
• /
• 2007

This study focused on the effects of the $CO_2$ gas concentration in fresh charge and induction air temperature on the combustion characteristics of homogeneous charge compression ignition with dimethyl ether (DME) fuel, which was injected at the intake port. Because of adding $CO_2$ in fresh charge, start of auto-ignition was retarded and bum duration became longer. Indicated combustion efficiency and exhaust gas emission were found to be worse due to the incomplete combustion. Partial burn was observed at the high concentration of $CO_2$ in fresh charge with low temperature of induction air. However, indicated thermal efficiency was improved due to increased expansion work by late ignition and prolonged bum duration. Start of auto-ignition timing was advanced with negligible change of burn duration, as induction air temperature increased. Burn duration was mainly affected by oxygen mole concentration in induction mixture. Bum duration was increased, as oxygen mole concentration was decreased.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.587-590
• /
• 2017

마이크로 가스터빈엔진의 성능 실험연구를 수행하였다. 성능측정을 위하여 마이크로엔진에 적합한 시험장치를 구축하였으며, Olympus HP Engine을 이용하여 성능측정을 수행하였다. 엔진흡입 공기유량, 추력, 연료소모율, 각 구성품 입구에서의 공기 및 가스온도를 측정하였다. 측정된 결과부터 마이크로 가스터빈 엔진의 성능특성을 보다 잘 이해할 수 있었다.

• 한국자동차공학회논문집
• /
• 제10권4호
• /
• pp.51-59
• /
• 2002

In this study, cycle simulation was performed to investigate the effect of EGR on combustion characteristics and emissions including NO and soot using a two-zone model in a DI diesel engine. The NO formation was well predicted for different EGR rate and temperature using a two-zone model. The oxygen in the inlet charge was replaced by CO$_2$ and H$_2$O with EGR. The reduction in the inlet charge oxygen resulted in very large reduction in NO level at the same inlet charge temperature. The effect of EGR was to reduce the burned gas temperature. When EGR was increased from 0% to 15%, the peak flame temperature was decreased by 50$\^{C}$ and it caused about 57% NO reduction. EGR caused increase of the overall inlet charge temperature which offset some of benefit of lower flame temperature resulting from O$_2$ displacement. Cooling the EGR was confirmed to provide additional benefits by lowering NO emission. It also reduced soot emission.

• Advances in materials Research
• /
• 제8권1호
• /
• pp.11-24
• /
• 2019

This paper presents a review study for energy-efficient gas turbines (GTs) with cycles which contributes significantly towards sustainable usage. Nonetheless, these progressive engines, operative at turbine inlet temperatures as high as $1600^{\circ}C$, require the employment of highly creep resistant materials for use in hotter section components of gas turbines like combustion chamber and blades. However, the gas turbine obtain its driving power by utilizing the energy of treated gases and air which is at piercing temperature and pushing by expanding through the several rings of steady and vibratory blades. Since the turbine blades works at very high temperature and pressure, high stress concentration are observed on the blades. With the increasing demand of service, to provide adequate efficiency and power within the optimized level, turbine blades are to be made of those materials which can withstand high thermal and working load condition for longer cycle time. This paper depicts the recent developments in the field of implementing the best suited materials for the GTs, selection of proper Thermal Barrier Coating (TBC), fracture analysis and experiments on failed or used turbine blades and several other designing and operating factors which are effecting the blade life and efficiency. It is revealed that Nickel based Superalloys were promising, Cast Iron with Zirconium and Pt-Al coatings are used as best TBC material, material defects are the foremost and prominent reason for blade failure.

• 한국가스학회지
• /
• 제2권4호
• /
• pp.47-52
• /
• 1998

수냉식 흡수식 냉동기에 주로 사용되고 있는 LiBr/water 흡수용액을 대체할 수 있는 신흡수 용액으로 제안된 흡수용액중 4성분계 흡수용액($LiBr+LiNO_3+LiC1+H_2O$)의 수증기 흡수성능을 수직관 흡수기를 사용하여 시험하였다. 시험변수로는 입구농도, 입구온도, 냉각수 입구온도, 용액유량을 변경하였다. 수증기 흡수특성 시험 결과 4성분계 용액이 LiBr/water용액보다 $2\%$ 높은 농도에서 대둥한 흡수력을 가짐을 알 수 있었다. 그러나 4성분계 흡수용액이 LiBr/water용액보다 $3\%$정도 용해도가 높으므로 실제 흡수식 냉동기에 적용시 LiBr용액보다 우수한 흡수능력을 가질 수 있어 소형, 공냉형 흡수식 냉동기에 적용이 가능하다.

• 플랜트 저널
• /
• 제18권2호
• /
• pp.32-40
• /
• 2022

본 연구에서는 부분부하 운전 시 가스터빈의 공기량 조절에 따른 열병합 발전의 운전데이터 변화를 알아보았다. 가스터빈 부분부하 80%시 시뮬레이션 한 결과 입구가이드베인을 최대 24% 추가로 닫을 수 있었고, 압축기 공기량은 66.11 kg/s 감소, 배기가스 온도는 52℃ 상승시킬 수 있었다. 부분부하 90%는 입구가이드베인을 최대 12% 추가로 닫을 수 있었고, 압축기 공기량은 33.33 kg/s 감소, 배기가스 온도는 23℃ 상승 시킬 수 있었다. 열부하 추종운전 시 부분 부하 80%에서 출력을 최대 5.68 MW 상승, 복합발전 효율을 0.73% 상승, 열병합발전 효율을 1.81% 상승 시킬 수 있었고, 부분부하 90%에서 출력을 최대 2.55 MW 상승, 복합발전 효율을 0.32% 상승, 열병합발전 효율을 0.72% 상승 시킬 수 있었다.