• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.129-135
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• 2010

Homogeneous charge compression ignition (HCCI) engines have the potential to provide both diesel-like efficiency and very low emissions of nitrogen oxide (NOx) and particulate matter(PM). However, several technical issues still must be resolved before HCCI can see application. Among these, steep pressure-rise rate which leads to narrow operating range of HCCI engine continues to be a major issue. This work investigates the combination of two methods to mitigate the excessive pressure-rise rates at high power output, namely fuel stratification and Cooled exhaust-gas recirculation (Cooled EGR), after identifying the each effects to pressure-rise rate. When applying the fuel stratification to simulation, total fuelling width of 0.15 at BDC is set as a equivalent ratio difference based on the previous research. In order to simulate the effects of cooled EGR, $CO_2$ mole fraction in pre-mixture is changed ranging from 0 to 30%. DME which has a characteristic of two-stage ignition is used as a fuel.

• 한국가스학회지
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• 제13권6호
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• pp.21-28
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• 2009

본 연구의 목적은 온도 성층화와 농도 성층화의 효과가 HCCI 연소에서 압력상승률 저감과 배기가스에 어떤 영향을 미치는지 알아보는 것이다. 2단계 열발생이 생기는 디메틸에테르(Di-Methyl Ether, DME) 연료를 사용하였다. 수치계산은 멀티 존 모델과 상세 화학 반응 스킴을 이용하였다. 수치계산 결과, 온도 성층화와 농도 성층화는 연소기간을 길게 하여 압력상승률을 저감시키는 것을 확인하였다. 그러나 농도 성층화의 폭이 너무 커지면 오히려 일산화탄소와 질소산화물이 증가하였으며, 연소 효율은 감소하였다.

• Elastomers and Composites
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• 제40권4호
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• pp.284-289
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• 2005

레졸로 가교된 NR 복합체의 열노화에 의한 가교밀도변화를 연구하였다. 노화 온도는 $50-90^{\circ}C$였다. 가교밀도 변화는 노화 온도가 올라감에 따라 증가하다 감소하였다. 가교밀도 변화 정도는 레졸 함량이 증가함에 따라 감소하였다. 열노화에 의한 가교밀도의 증가는 레졸로 마감된 매달린 작용기들의 결합 반응과 메틸올이나 메틸렌 퀴논 중간체를 갖는 매달린 작용기의 가교 반응으로 설명하였다. 그리고 열노화에 의한 가교밀도의 감소는 디메틸렌 에테르 연결을 갖는 기존 레졸 가교의 분해로 설명하였다.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.636-641
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• 2021

Using numerical analysis, various factors influencing the performance development of high-pressure pumps for Dimethyl Ether (DME) engines were identified and the impact of each factor was evaluated using Taguchi method. DME fuels are more compressive than diesel fuels and have the lower heat generation, so it is necessary to increase the size of the plunger and speed (RPM) of the pump as well. In addition, it is necessary to change the shape and design of control valve to control the discharge flow and pressure. In this study, various variables affecting the performance and flow rate increase of high-pressure pumps for DME engines are planned using Taguchi method, and the best design method is proposed using correlation of the most important variables. As a result, we were able to provide the design value needed for a six-liter engine and provide optimal conditions. The best combination factors to optimize the flow rate at RPM 2,000 and diameter plunger with 20 mm. The regression equation can also be used to optimize the flow rate; -8, 13+0, 2552 RPM +54, 17 diam. Plunger.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.660-669
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• 2012

Gas resources captured in the form of gas hydrates are an order of magnitude larger than the resources available from conventional resources. Focus of this research is to investigate the effect of DME on phase equilibria of methane hydrate, as well as the possibility of the use of the PRO/II computer simulation to estimate the phase equilibria. In systems containing water and a gaseous component like, for instance, methane, ethane, and propane, gas hydrates may occur, if conditions in terms of pressure and temperature are satisfied. Mixtures of gases, e.g. LPG or natural gas, are also able to form gas hydrates in the presence of water. The experiments presented here were performed at temperatures varying between 268.15K and 288.15K and at pressures varying between 1.88 MPa and 10.56 MPa. It was found that the phase equilibria of methane hydrate is influenced by the addition of DME to the system. The pressure for the equilibrium hydrate-liquid water-vapor (H - $L_w$ - V) in the system water + methane is reduced upon addition of DME. The phase equilibria of methane hydrate can be estimated by the PRO/II computer simulation, whereas those of methane hydrate containing DME or LPG can't be estimated properly.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.99-106
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• 2013

DME (Di-Methyl Ether) is synthetic product that is produced through dehydration of methanol or a direct synthesis from syngas. And it is able to save fossil fuel and reduce pollutants of emission such as PM and $CO_2$. In spite of its advantages it is difficult to design DME fuelled engine system because DME fuel may cause to severely generate cavitation and corrosion in fuel delivery system due to physical properties of DME. Therefore, in this study three-dimensional internal flow characteristics with consideration of cavitation were predicted in the DME injector using diesel and DME fuel. Moving grid technique was employed to describe needle motion and 1-D hydraulic simulation of injector was also simulated to obtain transient needle motion profiles. The results of simulation show that cavitations was generated at the inlet of nozzle near high velocity region both diesel and DME. And mass flow rate of DME is reduced by 4.73% compared to that of diesel at maximum valve lift because cavitation region of DME is much more larger. To increase flow rate of DME injector, internal flow simulation has been conducted to investigate the nozzle hole inner R-cut effect. The flow rates of diesel and DME increase as R-cut increases, and flow coefficient of DME fuel injector was increased by 6.3% on average compared with diesel fuelled injector. Finally, optimum shape of DME injector nozzle is suggested through the comparison of flow coefficient with variation of nozzle hole inner R-cut.

• 폴리머
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• 제30권2호
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• pp.162-167
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• 2006

1,2,3,4-시클로부탄 테트라카복시산 이무수물과 4,4'-디아미노디페닐에테르(DDE)를 용액 중합 반응하여 폴리암산(PAA) 용액을 제조한 후, 1,2-에폭시-3-페녹시프로판과 반응시켜 폴리암산에스테르(PAE)를 합성하였다. 여기에 용해억제재로서 30 wt%의 디아조나프토퀴논 유도체(DI)를 첨가하였다. $365{\sim}400nm$의 파장에서 $200mJ/cm^2$의 자외광을 조사한 후, 0.95 wt%의 테트라메틸암모니움히드록사이드 수용액으로 현상한 결과 $25{\mu}m$ 해상도의 양성형 미세 화상을 얻었다. 비노광부에 잔존하는 폴리이미드 박막은 400nm에서 92% 이상의 우수한 광투과도를 나타내었다.

• 한국수소및신에너지학회논문집
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• 제34권1호
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• pp.59-68
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• 2023

In this study, the performance of high-pressure fuel pumps was compared to find a high-pressure pump suitable for dimethyl ether (DME) fuel, and to establish a database of basic data on flow rates. The use of DME in compression ignition engines can reduce pollutant emissions. The cetane value of DME is higher than that of diesel fuel. The physical properties of DME are similar to liquefied gasoline gas (LPG), and when pressurized at a pressure of 6 bar or more, it changes from gas to liquid. Two types of high pressure pumps used in this study were independent injection type pump and a wobble plate type pump. Two high-pressure pumps with different injection types were compared. By measuring and comparing the performance changes of the two high-pressure pumps, a pump suitable for DME was selected and performance improvement measures were proposed. The changed experimental conditions to measure the performance change of the high pressure pump were increased in the units of 100 to 1,000 rpm and 100 rpm, and the experiment was performed at common rail pressures 300 and 400 bar. it was confirmed that the DME inside the fuel supply system remained in a liquid state through temperature sensors, pressure sensors, and pressure gauges. As a result of the experiment, it was confirmed that the flow rate discharged from the high-pressure fuel pump increased as the motor rotational speed increased, and the flow rate of the high-pressure fuel pump

• 멤브레인
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• 제18권4호
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• pp.282-293
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• 2008

친전자성 치환반응으로 제조된 술폰화 단량체, 비(非)술폰화 단량체 및 탄산칼륨을 이용하는 직접 중합법을 통하여 높은 점도의 술폰화 폴리아릴에테르술폰 공중합체를 합성하고, 이들을 원료로 N-메틸-2-피롤리돈(NMP)과 디메틸아세트아미드(DMAc)의 혼합 용매 상에서 직접 메탄을 연료전지용 고분자 전해질 막을 제조하였다. 막 제조 시의 용매 효과에 주목하여 혼합 용매의 부피 비는 $0{\sim}100%$로 변화시키고 공중합체의 술폰화도는 50%로 고정하였다. 이온 전도도 및 메탄올 투과도 측정을 통하여 최종 전해질 막의 기본 특성을 파악하고, 주사전자현미경 및 원자간력현미경분석을 통한 표면 분석 결과와 비교함으로써 이들의 상관관계를 고찰하였다. 막 제조 시의 용매 혼합 비율을 적절히 조절함에 따라 최종 전해질 막의 이온 전도도를 크게 향상시킬 수 있음이 확인되었는데, $25^{\circ}C$의 100% 가습 환경에서 측정된 수소 이온 전도도는 NMP : DMAc 50:50 부피/부피-%에서 최대 $1.38{\times}10^{-1}\;S/cm$이었다.

• 공업화학
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• 제26권2호
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• pp.234-238
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• 2015

모델 콜타르 유분 중에 함유된 질소고리화합물(NHC)의 분리를 메탄올과 포름아마이드 추출에 의해 비교했다. 원료로서는 4종류의 NHC (NHCs : 퀴놀린, 이소퀴놀린, 인돌, 퀴날딘), 3종류의 2환 방향족 화합물(BACs : 1-메틸나프탈렌, 2-메틸나프탈렌, 디메틸나프탈렌), 비페닐과 페닐에테르로 제조한 모델 콜타르 유분을 사용했다. 용매로서는 메탄올과 포름아마이드 수용액을 사용했다. 원료와 용매의 접촉 장치로서는 회분 교반기를 사용했다. 사용한 용매와 무관하게, 초기 용매 함수율의 감소와 평형조작 온도의 상승은 NHCs의 분배계수를 급격히 증가시켰으나, 역으로 BACs를 기준한 NHCs의 선택도를 감소시켰다. 초기 용매/원료의 체적비가 감소함에 따라 NHCs의 분배계수는 감소했으나, BACs를 기준한 NHCs의 선택도는 거의 일정했다. 동일한 실험조건에서, NHCs의 분배계수는 메탄올 추출이 포름아마이드 추출에 비해 약 3~5배 높았으나, BACs를 기준한 NHCs의 선택도는 역으로 포름아마이드 추출이 메탄올 추출에 비해 3~7배 높았다. 또한, NHCs의 용해력과 선택도의 밸런스에 NHCs의 추출처리속도를 부가하여 두 용매 추출법을 비교했다.