• 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.

• 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.

• 폴리머
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• 제39권3호
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• pp.453-460
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• 2015

초임계 유체 기술을 이용한 폴리락티드 스테레오 콤플렉스 제조는 폴리락티드의 열적 및 기계적 물성을 향상시키는 좋은 방법이다. 이 연구에서는 초임계 유체인 디메틸에테르를 이용하여 고분자량 폴리락티드를 높은 수율로 100% 스테레오 콤플렉스화를 시켰다. 폴리락티드에 대한 디메틸에테르의 높은 용해성은 이 공정의 핵심요소로 250 bar, $70^{\circ}C$, 1.5시간에 반응이 종료되었다. 폴리락티드의 스테레오 콤플렉스 연구는 압력, 온도, 시간, 농도 및 분자량을 변화시키며 진행하였다. 스테레오 콤플렉스화는 온도와 압력이 증가할 때 높아졌다. 분자량 20만 이상인 PLLA와 PDLA는 6%의 디메틸에테르에서 100% 스테레오 콤플렉스화가 이루어졌다. 스테레오 콤플렉스화 정도는 DSC 및 XRD를 통해 이루어졌다. 또한 DSC 및 TGA 분석을 통해 융점이 $50^{\circ}C$ 이상 높아진 폴리락티드가 얻어졌음을 확인하였다.

• 공업화학
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• 제25권1호
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• pp.34-40
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• 2014

메조 세공을 갖는 SAPO-34 촉매를 2차 주형 물질로서 탄소 나노튜브(CNT)를 이용한 수열 합성 방법에 의해 성공적으로 합성했으며, CNT 첨가량(0.5, 1.5, 2.5 및 4.5 mol%)이 촉매 성능에 미치는 영향을 조사하였다. 합성된 촉매들은 X-선 회절 분석(XRD), 주사 전자 현미경(SEM), 질소 흡탈착 등온선 및 암모니아 승온 탈착($NH_3$-TPD)을 통해 특성분석을 수행하였다. 합성된 촉매 중에서 1.5 mol% CNT를 첨가하여 제조된 SAPO-34 (1.5C-SAPO-34)가 가장 큰 메조 세공부피를 나타냈을 뿐만 아니라 총 산점의 양도 가장 높은 것으로 관찰되었다. 그러나 CNT의 함량을 그 이상 첨가하여 제조한 촉매들의 경우 결정의 크기가 너무 작아 오히려 메조 세공의 부피가 감소하는 것으로 나타났다. 제조된 촉매들의 dimethyl ether to olefins 반응에서 CNT 함량에 따른 촉매 수명과 경질 올레핀($C_2{\sim}C_4$)의 선택성을 연구하였다. 그 결과 1.5C-SAPO-34 촉매는 기존의 SAPO-34 촉매와 비교하여 더 우수한 경질 올레핀 선택도와 약 36%의 향상된 촉매수명을 나타났다.

• 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.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.925-933
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• 2011

The traditional feedstock for dimethyl ether (DME) has been natural gas obtained by pipeline from a nearby natural gas or oil field. This report focuses on other feedstock: Coal bed methane (CBM). The resource availability and suitability of CBM for DME manufacturing have been investigated. CBM in a short time has become an important industry, providing an abundant clean-burning fuel and also suggesting as a feedstock for gas industry. The use of CBM will have very little impact on the KOGAS' DME process design and economics up to 50 vol% of $CO_2$ in the CBM source. Many of the CBM sources in Asia are high in $CO_2$, but pose no difficulties for the KOGAS' DME plant. Since tri-reformer requires substantial $CO_2$ in its feed, no $CO_2$ removal from the CBM feed is needed. The $CO_2$ in the CBM means that less $CO_2$ needs to be recycled from the downstream in the process.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1299-1304
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• 2014

The electrochemical performance of Li-S cells was investigated in various ternary electrolyte solutions composed of 1,2-dimethoxyethane (DME), tetra(ethylene glycol) dimethyl ether (TGM), and 1,3-dioxolane (DOX). The discharge capacity values and cycle data obtained at each composition were statistically treated with the Minitab program to obtain mixture contour plots, from which the optimal composition of the ternary solvent systems was predicted. The discharge capacities and capacity retention were quite dependent on the electrolyte composition. It was estimated from the contour plots of the capacity at 1.0 C that the discharge capacity sharply increased with a decrease in the TGM content. High capacities greater than 900 mAh/g at 1.0 C were expected for the electrolyte composition with a volume ratio of DME/TGM/DOX = 1/0/1. In contrast, it was predicted from the mixture contour plot of the capacity retention that the cycle performance would significantly increase with an increase in the DME content.

• 한국분무공학회지
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• 제14권3호
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• pp.109-116
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• 2009

The purpose of this study is the experimental and numerical investigation on the DME spray characteristics in the combustion chamber according to the injection timing in a common-rail injection system. The visualization system consisted of the high speed camera with metal halide lamp was used for analyzing the spray characteristics such as spray development processes and the spray tip penetration in the free and in-cylinder spray under various ambient pressure. In order to observe the spray characteristics as a function of injection timing, the piston head shape of re-entrant type was created and the fuel injected into the chamber according to various distance between nozzle tip and piston wall in consideration of injection timing. Also, the spray and evaporation characteristics in the cylinder was calculated by using KlVA-3V code for simulating spray development process and spray tip penetration under real engine conditions. It was revealed that the high ambient pressure of 3 MPa was led to delay the spray development and evaporation of DME spray. In addition, injected sprays after BTDC 20 degrees entered the bowl region and the spray at the BTDC 30 degrees was divided into two regions. In the calculated results, the liquefied spray tip penetration and fuel evaporation were shorter and more increased as the injection timing was retarded, respectively.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.171-178
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• 2008

The combustion and exhaust emission characteristics were investigated in an DME fueled HCCI engine. Carbon dioxide, nitrogen and mixed gas, which was composed of carbon dioxide and nitrogen, were used as control parameters of combustion and exhaust emission. As the oxygen concentration in induction air, which was occurred by carbon dioxide, nitrogen and mixed gas, was reduced, the start of auto-ignition was retarded and the burn duration was extended due to obstruction of combustion and reduction of combustion temperature. Due to these fact, indicated mean effective pressure was increased and indicated combustion efficiency was decreased by carbon dioxide, nitrogen and mixed gas. In case of exhaust emission, hydrocarbon and carbon monoxide was increased by reduction of oxygen concentration in induction air. Especially, partial burning was appeared at lower than about 18% of oxygen concentration by supplying carbon dioxide. However it was overcome by intake air heating.

• International Journal of Automotive Technology
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• 제4권3호
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• pp.119-124
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• 2003

Dimethyl Ether (DME) is an excellent alternative fuel that provides lower particulate matter (PM) than diesel fuel under the same engine operating conditions. Spray characteristical of DME in common rail injection system were investigated within a constant volume chamber by using the particle motion analysis system. The injector used in this study has a single hole with the different orifice diameter of 0.2, 0.3 and 0.4 mm. The injection pressure was fixed at 35MPa and the ambient pressure was varied from 0.6 to 1.5 MPa. Spray characteristics such as spray angle, spray tip penetration and SMD (Sauter mean diameter) were measured. Spray angle was measured at 30d$_{0}$, downstream of the nozzle tip. The measured spray angie increased with increase in the ambient pressure. Increase of the ambient pressure results in a decrease of spray penetration. The experimental result, of spray penetration were compared with the predicted one by theoretical and empirical models. Increase in the ambient pressure and nozzle diameter results in an increase of SMD at a distance 30, 45 and 60d$_{0}$, downstream of the nozzle, respectively.ely.