• Journal of ILASS-Korea
• /
• v.15 no.1
• /
• pp.31-37
• /
• 2010

The aim of this work is to investigate the spray and combustion characteristics of dimethyl-ether (DME) at various injection conditions. The spray characteristics such as spray tip penetration and spray cone angle were experimentally studied from the spray images which obtained from the spray visualization system. Combustion and emissions characteristics were numerically investigated by using KIVA-3V code coupled with Chemkin chemistry solver. From these results, it revealed that DME spray had a shorter spray tip penetration and wider spray cone angle than that of diesel spray due to the low density, low surface tension, and fast evaporation characteristics. At the constant heating value condition, DME fuel showed higher peak combustion pressure and earlier ignition timing, because of high cetane number and superior evaporation characteristics. In addition, the combustion of DME exhausted more $NO_x$ emission and lower HC emission due to the active combustion reaction in the combustion chamber. The result shows that DME had a little soot emission due to its molecular structure characteristics with no direct connection between carbons.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.6
• /
• pp.16-22
• /
• 2004

Dimethyl Ether (DME) has been considered as one of the most attractive alternative fuels for a compression ignition engine. The major advantage of DME-fuelled engine is a great potential for soot-free combustion without sacrificing an inherent high thermal efficiency of diesel engine, despite a necessity for modification of the conventional fuel injection system. An experimental study on DME and conventional diesel sprays was conducted by employing a common-rail type fuel injection system with a 5-holes sac type nozzle, including a constant volume vessel pressurized with nitrogen gas. The injection rates of DME and diesel fuel were recorded with the Bosch type injection rate meter. The injection delay of DME was shorter than that of diesel fuel. The measured injection rates of DME and diesel fuel were correlated with spray penetrations. The prediction method of spray penetration was established using the injection rates, which was verified with the Dent's penetration model and found to agree well for DME case.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.6
• /
• pp.30-37
• /
• 2004

The combustion and emission characteristics of a direct injection CI engine fuelled with DME(Dimethyl Ether) and diesel fuel were compared at idle engine speed(800 rpm) with various injection parameters. An optical single cylinder diesel engine equipped with a common-rail fuel injection system was constructed to investigate combustion processes of DME and diesel fuel. The combustion images were recorded with a high-speed video camera system. The results demonstrated that the DME-fuelled engine was superior to the conventional diesel engine in terms of engine performance and emissions. The optimal injection timing of DME was located around IDC(Top Dead Center), which was roughly same as that of diesel fuel. As the injection timing was advanced much earlier than TDC, NOx (Nitric Oxides) level increased considerably. NOx emission of DME was equal or a little higher than that for diesel fuel at the same injection pressure and timing because of higher evaporation characteristics of DME. Throughout all experimental conditions, DME did not produce any measurable smoke level.

• Natural Product Sciences
• /
• v.3 no.2
• /
• pp.127-134
• /
• 1997

Two new dimeric phenolic conjugates, 2,3-di-O-dehydrodigallicmonocarboxyl-$({\alpha},{\beta})$-$^4C_1$-glucopyranose and ellagic acid 3,3'-dimethylether-4-0-$SO_3K$ were isolated from the debarked heart wood of Tamarix tetragyna (Tamaricaceae) along with the known phenolic compounds, isoferulic acid, ferulic acid, gallic acid, gallic acid 4-methyl ether, syringic acid, ellagic acid 3,3'-dimethyl ether and ellagic acid. All structures were determined mostly by ESI-MS, ID and 2D-NMR spectroscopy.

• Korean Chemical Engineering Research
• /
• v.47 no.4
• /
• pp.446-452
• /
• 2009

The behavior of a one-step fixed bed reactor which directly synthesizes dimethyl ether(DME) from Natural Gas was simulated. In the reactor, the prevention of the occurrence of hot spots which can cause deactivation of catalysts is pivotal, since methanol synthesis and dehydration reaction involved in the synthesis of DME are highly exothermic. Therefore, we simulated and compared performance of the reactor with counter-current cooling and pool boiling system that can be applied to a commercial plant. As a result, we found that counter-current cooling system is more effective in terms of CO conversion and DME productivity. However, pool boiling system can operate in a small temperature gradient that can decrease problems caused by hot spot. And, the system can operate in a safer range.

• Korean Chemical Engineering Research
• /
• v.55 no.2
• /
• pp.230-236
• /
• 2017

Solubility data of carbon dioxide ($CO_2$) in poly(ethylene glycol) dimethyl ether (PEGDME) are presented at pressures up to about 50 bar and at temperatures between 303 K and 343 K. The solubilities of $CO_2$ were determined by measuring the bubble point pressures of the $CO_2+PEGDME$ mixtures with various compositions using a high-pressure equilibrium apparatus equipped with a variable-volume view cell. To observe the effect of the PEGDME molecular weight on the $CO_2$ solubility, the $CO_2$ solubilities in PEGDME with two kinds of molecular weight were compared. As the equilibrium pressure increased, the $CO_2$ solubility in PEGDME increased. On the other hand, the $CO_2$ solubility decreased with increasing temperature. When compared at the same temperature and pressure, the PEGDME with a higher molecular weight gave smaller $CO_2$ solubility on a mass fraction and molality basis, but gave greater $CO_2$ solubilities on a mole fraction basis.

• Membrane Journal
• /
• v.15 no.4
• /
• pp.330-337
• /
• 2005

Water selective silica membranes were prepared fur use as membrane reactor for synthesis of dimethyl ether (DME) by methanol dehydration. Silica membranes formed on a Porous SUS tube by ultrasonic spray Pyrolysis (USP) and chemical vapor deposition (CVD) using tetraethoxysilane (TEOS) as precursor. The CVD-derived membranes formed higher level of trade-off line between water permeance and water/methanol selectivity than that of the USP-derived membranes. The membrane reactor possessing water permeance of $1.2\times10^{-7}\;mol\;{\cdot}\;m^{-2}\;{\cdot}\;S^{-1}\;{\cdot}\;Pa^{-1}$ and water/methanol selectivity of 10 exhibited increase in methanol conversion of about $20\%$ comparing to conventional reactor system. These findings led us to conclude that the dehydration membrane reactor simultaneously separating the water vapour produced in the reaction zone was effective in increasing the reaction conversion.

• Clean Technology
• /
• v.21 no.2
• /
• pp.124-129
• /
• 2015

The constant-volume method was used to determine the solubility of CO₂ in various physical absorbents such as DMPEG (dimethyl ether of polyethylene glycol), DEC (diethyl carbonate), DMC (dimethyl carbonate), and TAT (triacetin) in the total pressure range from 5 to 30 bar. The Peng-Robinson equation of state has been used to describe the equilibrium behavior of these mixtures. It was found that the solubility of absorbents was in the of DMPEG250 > TAT > DEC > DMC at the same temperature. Futhermore, the solubiity of blended absorbent of DMPEG250 and DEC is higher than that of DMPEG 250 alone. Therefore, blended absorbent of DMPEG250 and DEC is expected to be an effective and low cost absorbent for physical absorption in precombustion CO₂ capture.

• Journal of the Korean Society of Combustion
• /
• v.12 no.3
• /
• pp.33-39
• /
• 2007

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in high-pressure engine conditions. In order to realistically simulate the dimethyl ether (DME) spray dynamics and vaporization characteristics in high-pressure and high-temperature environment, the high-pressure vaporization model is utilized. The interaction between chemistry and turbulence is treated by employing the Representative Interaction Flamelet (RIF) model. The detailed chemistry of 336 elementary steps and 78 chemical species is used for the DME/air reaction. Numerical results indicate that the RIF approach, together with the high-pressure vaporization model, successfully predicts the essential feature of ignition and spray combustion processes.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.5
• /
• pp.589-595
• /
• 2003

DME(Dimethyl ether) is an oxygenated fuel with a octane number higher than that of diesel oil. It meets the ULEV emission regulation and reduces the smoke to almost zero when used in a diesel engine. In the present study, engine performance and exhaust emissions were investigated with a conventional DI diesel engine which has a jerk type injection pump. Test results showed that the power with DME were almost same as that of pure diesel oil, and the brake thermal efficiency increased a little. Also, smoke index from DME engine showed nearly zero level, but NO$_{x}$ was increased compare to diesel oil.