• 한국자동차공학회논문집
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• 제19권2호
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• pp.35-41
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• 2011

This work investigates the potential of in-cylinder thermal stratification and fuel stratification for extending the operating ranges in HCCI engines, and the coupling between thermal stratification and fuel stratification. Computational results areemployed. The computations were conducted using both a custom multi-zone version and the standard single-zone version of the Senkin application of the CHEMKINII kinetics rate code, and kinetic mechanism for di-methyl ether (DME). This study shows that the potential of thermal stratification and fuels stratification for extending the high-load operating limit by a staged combustion event with reduced pressure-rise rates is very large. It was also found that those stratification offers good potential to extend low-load limit by a same mechanism in high-load. However, a combination of thermal stratification and fuel stratification is not more effective than above stratification techniques for extending the operating ranges showing similar results of fuel stratification. Sufficient condition for combustion (enough temperature for) turns misfire in low-load limit to operate engines, which also leads to knock in high-load limit abruptly due to the too high temperature with high. DME shows a potential for maximizing effect of stratification to lower pressure-rise rate due to the characteristics of low-temperature heat release.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.232-239
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• 2011

DME has received much attention because of its possible use as a fuel and a chemical feedstock. Chemical conversion of DME to olefin (DTO) over various SAPO-34 catalysts was carried out using a fixed bed reactor. Main products of the reaction were light olefins such as ethylene, propylene and butenes. The best reaction conditions for high life time of the catalyst and high selectivity of light olefins were a reaction temperature of $400^{\circ}C$ and a WHSV of $3.54h^{-1}$. In addition, it was found that the deactivation of a SAPO-34 catalyst can be significantly suppressed by the addition of $ZrO_2$ as a supporter.

• 대한기계학회논문집B
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• 제36권12호
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• pp.1151-1159
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• 2012

본 논문에서는 노즐홀 직경을 확대하여 유량을 증가시킨 DME 인젝터의 가시화 실험과 분무 해석을 수행하였다. 해석의 신뢰성을 확보하기 위하여 가시화 실험과 분무해석을 비교하였고, 실엔진 모사 조건에서 분무 해석을 수행하여 DME의 거동을 예측하였다. 분사 압력과 분위기 압력이 각각 35MPa 및 5MPa인 경우 가시화 실험과 분무 해석의 도달거리는 3.57%의 차이를 나타내었다. 실엔진 모사 해석의 경우, 완전하게 발달된 DME의 분무 도달거리는 분위기 온도와 압력의 비가 300K/MPa에서 42mm로 최대를 나타내었고, 300K/MPa미만의 영역에서 DME의 분무는 분위기 압력, 300K/MPa초과의 영역에서는 분위기 온도의 영향이 지배적임을 확인하였다.

• 대한기계학회논문집B
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• 제31권11호
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• pp.926-935
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• 2007

The NOx emission characteristics of DME in laminar coaxial jet and counterflow nonpremixed flames were investigated using experimental and numerical approaches, respectively. The flame structure and NOx emission of DME were compared with those of $C_2H_6$ and $C_3H_8$. The DME flame was calculated using the Kaiser's mechanism, while the $C_2H_6$ and $C_3H_8$ flames were calculated using the $C_3$ mechanism. These mechanisms were combined with the modified Miller-Bowman mechanism for the analysis of NOx. Experimental results show in coaxial jet flame that DME flame has the characteristics of partial premixed flame and the flame length decreases up to 1/3 than that of $C_3H_8$ in the same condition of fuel mass flowrate. Then, the NOx emission of DME decreases to 40% approximately, comparing with that of $C_3H_8$. In the calculated results of counterflow nonpremixed flame, DME flame shows the $EI_{NO}$ decreases up to 50% approximately than those of$ C_2H_6$ and $C_3H_8$ flames when the equivalent fuels are consumed per unit mass and time. Although the overall NOx reaction path of DME is similar with other hydrocarbon fuels, it can be identified that DME flame has a distinct NO reduction mechanism due to the reburning NO chemistry in fuel rich region. From these results, we can conclude that the different NOx emission characteristics of DME flame with other hydrocarbon fuels are attributed to not the temperature increase and the activation of NO reactions due to O atom in DME fuel but the rapid processes of pyrolysis/oxidation.

• 공업화학
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• 제20권2호
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• pp.186-190
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• 2009

본 연구는 수소제조를 위한 디메틸에테르 수증기 개질반응에 대한 열역학적 특성 분석을 목적으로 한다. 이를 위하여 온도(300~1500 K), 반응물 조성비(Steam/Carbon ratio = 1~7), 압력(1, 5, 10 기압) 등의 다양한 반응조건을 변화시키면서 열역학적 평형조성 및 효율 등을 조사하였다. 주어진 조건하에서 흡열반응인 개질반응과 발열반응인 수성가스 전환반응 및 메탄화반응간 경쟁특성을 확인하였으며, 반응온도 400 K를 지나면서 수소발생이 관찰되어 550 K를 지나면서 급격한 발생량의 증가를 확인하였다. 반응물 가운데 수증기의 비율을 증가시킬 경우 수성가스 전환반응이 촉진되어 일산화탄소 저감 및 수소발생 증가 거동을 나타내었다. 결과적으로 열역학적 효율감소를 최소화 하면서 수소발생량을 극대화 할 수 있는 조건은 반응온도 900 K 및 수증기 대 탄소간 비율이 3.0 이내의 범위에 해당하는 것으로 판단된다.

• 한국자동차공학회논문집
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• 제20권2호
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• pp.90-97
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• 2012

It is investigated of the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system is used since DME has compressibility and vaporization in atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed of spray shape, penetration length, and spray angle at the six nozzle holes. The 2 types injector were used, the one was 0.166 mm diameter the other one was 0.250 mm diameter. The ambient pressure which is based on gage pressure was 0 MPa, 2.5 MPa, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 MPa to 70 MPa. When using the converted injector, compared to using the common injector, the DME injection quantity was increased 127 % but it didn't have the same heat release. Both of the common and converted injector had symmetric spray shapes. In case of converted injector, there were asymmetrical spray shapes until 1.2 ms, but after 1.2 ms the spray shape was symmetrical. Compared with the common and converted injector, the converted injector had shorter penetration length and wider spray angle than the common injector.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.81-89
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• 2009

In this experimental study, the effects of clean alternative fuels compatible with diesel combustion on nano-sized particle emission characteristics were investigated in a 0.5L auto-ignited single-cylinder engine with a compression ratio of 15. Because the number concentration of nano-sized particles emitted by automotive engine, that are suspected of being hazardous to human health and environment, might increase with engine fuel considerably and recently attracted attention. So a ultra-low sulfur diesel(ULSD), BD100(100% bio-diesel) and Di-Methyl Ether(DME) fuels used for this study. And, as a particle measuring instrument, a fast-response particle spectrometer (DMS 500) with heated sample line was used for continuous measurement of the particle size and number distribution in the size range of 5 to 1000nm (aerodynamic diameter). As this research results, we found that this measurements involving the large proportion of particles under size order of 300nm and number concentration of $4{\times}10^9$ allowed a single or bi-modal distribution to be found at different engine load conditions. Also the influence of oxygen content in fuel and the catalyst could be a dominant factor in controlling the nano-sized particle emissions in auto-ignited engine.

• 에너지공학
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• 제24권4호
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• pp.33-41
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• 2015

DME는 높은 세탄가와 낮은 배출가스로 인하여 청정 디젤엔진 대체연료로 사용될 수 있고, LPG와 물리적 특성이 유사하기 때문에 혼합사용이 가능하다. 본 연구에서는 DME-LPG 혼합연료를 LPG 차량 연료에 적용한 실증평가를 수행하였다. 평가 차량으로는 LPG 연료 공급방식별로 액상연료공급방식(LPLi), 기상연료공급방식(LPGi), 분배식펌프 방식(Mixer type)의 LPG 자동차를 선택하였다. 배출가스(CO, THC, $NO_X$)와 연료소비효율에 대한 영향을 비교하기 위하여 LPG와 DME-LPG 혼합연료에 대한 성능평가를 수행하였다. 차량의 주행거리가 증가함에 따라 DME-LPG 혼합연료를 사용한 차량의 배출가스와 연료소비효율은 LPG 연료를 사용한 경우와 비교해서 동등한 수준으로 평가되었다.

• 설비공학논문집
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• 제19권7호
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• pp.545-554
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• 2007

Flow condensation heat transfer coefficients(HTCs) of R22, propylene, propane, DME and isobutane are measured on a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed refrigerant saturation temperature of $40{\pm}0.2^{\circ}C$ with mass fluxes of 100, 200, $300kg/m^2s$ and heat flux of $7.3\sim7.7kW/m^2$. The data are obtained in the vapor Quality range of $10\sim90%$. Test results show that at same mass flux the flow condensation HTCs of propylene, propane, DME and isobutane are higher than those of R22 by up to 46.8%, 53.3%, 93.5% and 61.6% respectively. Also well-known correlations developed based upon conventional fluorocarbon refrigerants predict the present data within a mean deviation of 30%. Finally, the pressure drop increase as the mass flux and Quality increase and isobutane shows the highest pressure drop due to its lowest vapor pressure among the fluids tested.

• 멤브레인
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• 제28권5호
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• pp.326-331
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• 2018

축전식 탈염(capacitive deionization)에 이용할 수 있는 폴리페닐렌 옥사이드(PPO) 음이온 교환막의 가교결합에 대해 조사하였다. 브롬화와 아민화 반응단계를 거쳐 PPO 음이온 교환 고분자를 제조하고 비스페놀 A 디글리시딜에테르(BADGE), m-페닐렌디아민(m-PDA), 헥사메틸렌디아민(HMDA) 등으로 가교하였다. 가교에 따른 겔화되는 시간은 HMDA > m-PDA > BADGE 순으로 짧았으며, 일정한 함량 이상으로 실온에서 가교하면 1-메틸피롤리돈(NMP)과 같은 비양성자성 용매(aprotic solvent)에 녹지 않아 내화학성이 증대되었다. 가교제(BADGE) 함량에 따른 음이온 교환막의 이온 교환 용량과 함수율을 측정하고 비교하였다. HMDA 용액에 침적하여 표면 가교한 PPO 음이온 교환막을 축전식 탈염에 적용한 결과 그 탈염 성능은 가교하지 않은 막과 비교하여 흡착단계의 초기 부분을 제외하고 거의 차이가 없었다.