Dimethyl ether as alternative fuel for CI engine and vehicle

As a developing and the most populous country in the world, China faces major challenges in energy supply and environmental protection. It is of great importance to develop clean and alternative fuels for internal combustion engines. On the basis of researches on DME engine and vehicle at Shanghai Jiaotong University in the last twelve years, fuel injection, combustion, performance and exhaust emissions of DME engine and DME vehicle are introduced in this paper. The results indicate that DME engines can achieve high thermal efficiency and ultra low emissions, and will play a significant role in meeting the energy demand while minimizing environmental impact in China.     

Dimethyl ether as alternative fuel for CI engine and vehicle

As a developing and the most populous country in the world, China faces major challenges in energy supply and environmental protection. It is of great importance to develop clean and alternative fuels for internal combustion engines. On the basis of researches on DME engine and vehicle at Shanghai Jiaotong University in the last twelve years, fuel injection, combustion, performance and exhaust emissions of DME engine and DME vehicle are introduced in this paper. The results indicate that DME engines can achieve high thermal efficiency and ultra low emissions, and will play a significant role in meeting the energy demand while minimizing environmental impact in China.     

Methoxy methane (dimethyl ether) as an alternative fuel for direct fuel cells

The electrooxidation of methoxy methane (dimethyl ether) was studied at different Pt-based electrocatalysts in a standard three-electrode electrochemical cell. It was shown that alloying platinum with ruthenium or tin leads to shift the onset of the oxidation wave towards lower potentials. On the other hand, the maximum current density achieved was lower with a bimetallic catalyst compared to that obtained with a Pt catalyst. The direct oxidation of dimethoxy methane in a fuel cell was carried out with Pt/C, PtRu/C and PtSn/C catalysts. When Pt/C catalyst is used in the anode, it was shown that the pressure of the fuel and the temperature of the cell played important roles to enhance the fuel cell electrical performance. An increase of the pressure from 1 to 3 bar leads to multiply by two times the maximum achieved power density. An increase of the temperature from 90 to 110 °C has the same effect. When PtRu/C catalyst is used in the anode, it was shown that the electrical performance of the cell was only a little bit enhanced. The maximum power density only increased from 50 to 60 mW cm⁻² at 110 °C using a Pt/C anode and a Pt_0.8Ru_0.2/C anode, respectively. But, the maximum power density is achieved at lower current densities, i.e. higher cell voltages. The addition of ruthenium to platinum has other effect: it introduces a large potential drop at relatively low current densities. With the Pt_0.5Ru_0.5/C anode, it has not been possible to applied current densities higher than 20 mA cm⁻² under fuel cell operating conditions, whereas 250 and almost 400 mA cm⁻² were achieved with Pt_0.8Ru_0.2/C and Pt/C anodes. The Pt_0.9Sn_0.1/C anode leads to higher power densities at low current densities and to the same maximum power density as the Pt/C anode.     

Sulfonated poly(ether ether ketone)/poly(ether sulfone) composite membranes as an alternative proton exchange membrane in microbial fuel cells

Custom-made proton exchange membranes (PEM) are synthesized by incorporating sulfonated poly(ether ether ketone) (SPEEK) in poly(ether sulfone) (PES) for electricity generation in microbial fuel cells (MFCs). The composite PES/SPEEK membranes at various composition of SPEEK are prepared by the phase inversion method. The membranes are characterized by measuring roughness, proton conductivity, oxygen diffusion, water crossover and electrochemical impedance. The conductivity of hydrophobic PES membrane increases when a small amount (3–5%) of hydrophilic SPEEK is added. The electrochemical impedance spectra shows that the conductivity and capacitance of PES/SPEEK composite membranes during MFC operation are reduced from 6.15 × 10⁻⁷ to 6.93 × 10⁻⁵ (3197 Ω–162 Ω) and from 3.00 × 10⁻⁷ to 1.56 × 10⁻³ F, respectively when 5% of SPEEK added into PES membrane. The PES/SPEEK 5% membrane has the highest performance compared to other membranes with a maximum power density of 170 mW m⁻² at the maximum current density of 340 mA m⁻². However, the interfacial reaction between the membrane and the cathode with Pt catalyst indicates moderate reaction efficiency compared to other membranes. The COD removal efficiency of MFCs with composite membrane PES/SPEEK 5% is nearly 26-fold and 2-fold higher than that of MFCs with Nafion 112 and Nafion 117 membranes respectively. The results suggest that the PES/SPEEK composite membrane is a promising alternative to the costly perfluorosulfonate membranes presently used as separators in MFC systems.     

Dynamic analysis of a PEM fuel cell hybrid system with an on-board dimethyl ether (DME) steam reformer (SR)

Low-temperature polymer electrolyte membrane fuel cell (PEMFC) acts as a promising energy source due to the non-pollution and high-energy density. However, as hydrogen supply is a major constraint limiting the wide spread of fuel cell vehicles, a dimethyl ether (DME)-steam on-board reformer (SR) based on catalytic reforming via a catalytic membrane reactor with a channel structure is a possible solution to a direct hydrogen supply. The DME-SR reaction scheme and kinetics in the presence of a catalyst of CuO/ZnO/Al₂O₃+ZSM-5 are functions of the temperature and hydrocarbon ratio in the hydrogen-reforming reaction. An electric heater is provided to keep the temperature at a demanded value to produce hydrogen. As there is no available analysis tool for the fuel cell battery hybrid vehicle with on-board DME reformer, it is necessary to develop the tool to study the dynamic characteristics of the whole system. Matlab/Simulink is utilized as a dynamic simulation tool for obtaining the hydrogen production and the power distribution to the fuel cell. The model includes the effects of the fuel flow rate, the catalyst porosity, and the thermal conductivity of different subsystems. A fuel cell model with a battery as a secondary energy storage is built to validate the possible utilization of on-board reformer/fuel cell hybrid vehicle. In consideration of time-delay characteristic of the chemical reactions, the time constant obtained from the experiment is utilized for obtaining dynamic characteristics. The hydrogen supplied by the reformer and the hydrogen consumed in the PEMFC prove that DME reformer can supply the adequate hydrogen to the fuel cell hybrid vehicle to cope with the required power demands.     

Sulfonated poly(ether ether ketone) as an ionomer for direct methanol fuel cell electrodes

Sulfonated poly(ether ether ketone) has been investigated as an ionomer in the catalyst layer for direct methanol fuel cells (DMFC). The performance in DMFC, electrochemical active area (by cyclic voltammetry), and limiting capacitance (by impedance spectroscopy) have been evaluated as a function of the ion exchange capacity (IEC) and content (wt.%) of the SPEEK ionomer in the catalyst layer. The optimum IEC value and SPEEK ionomer content in the electrodes are found to be, respectively, 1.33 meq. g⁻¹ and 20 wt.%. The membrane-electrode assemblies (MEA) fabricated with SPEEK membrane and SPEEK ionomer in the electrodes are found to exhibit superior performance in DMFC compared to that fabricated with Nafion ionomer due to lower interfacial resistance in the MEA as well as larger electrochemical active area. The MEAs with SPEEK membrane and SPEEK ionomer also exhibit better performance than that with Nafion 115 membrane and Nafion ionomer due to lower methanol crossover and better electrode kinetics.     

Dimethyl ether (DME) synthesis from CO2 and H2 through ethanol-assisted methanol synthesis and methanol dehydration

Two steps of dimethyl ether (DME) synthesis from CO₂ and H₂ in a batch reactor were studied, including CO₂ hydrogenation to methanol through ethanol-assisted method and methanol dehydration to DME. Additions of 10 wt% ZrO₂, Al₂O₃ and ZrO₂–Al₂O₃ into Cu/ZnO were investigated in low-temperature methanol synthesis using ethanol as catalytic solvent. Suitable zeolite (ZSM-5 and ferrierite) for methanol dehydration was also determined. Ethanol-assisted method offered high methanol yield and Cu/ZnO/ZrO₂ catalyst provided the highest CO₂ conversion (82.1%) and methanol yield (60.8%) at 150 °C and 50 bar since ZrO₂ decreased CuO crystallite sizes and increased surface areas of the catalyst. For methanol dehydration to DME, zeolite's strong acidity related to DME formation. The Cu/ZnO/ZrO₂ - Ferrierite provided the highest DME productivity at 0.44 mmol_DME/g_cat. In addition, DME synthesis from CO₂ and H₂ through ethanol-assisted methanol synthesis and methanol dehydration can be a potential method to simultaneously produce DME and ethylene. Under the operating conditions, ethylene was produced as a valued by-product of 5.65 mmol_Ethylene/g_cat from dehydration of ethanol. In this study, rather high methanol yield was obtained from ethanol-assisted method. However, DME yield can be further improved by increasing synthesis temperature.     

关于发展二甲醚(DME)燃料的探讨

开发替代燃料是解决我国油气短缺的重要手段。二甲醚(DME)以其优异的特性被普遍视为多用途、多原料来源的清洁替代燃料。本文回顾了国内外二甲醚燃料的研究和发展状况,探讨了我国发展二甲醚燃料的基础优势和需要注意的问题。     

二甲基醚（DME）燃烧特性研究

作者在定容燃烧弹上用火焰直接成像法研究二甲基醚 (DME)燃烧过程 ,研究了 DME的滞燃期和火焰传播特性以及不同环境温度和压力对燃烧过程的影响。研究结果表明 ,DME的滞燃期比柴油短 ,燃烧室内的温度和压力升高时 ,滞燃期缩短 ;DME的着火位置靠近喷嘴一侧 ,柴油与 DME的体积相同时 ,DME的燃烧持续期比柴油短 ;DME的燃烧火焰亮度比柴油小 ,表明 DME的燃烧温度比柴油低。燃烧后期 ,燃用 DME时 ,喷嘴有明显的泄漏现象。此外 ,作者在单缸直喷式柴油机上进行了燃用 DME的燃烧特性试验研究 ,研究结果表明 ,DME的预混合燃烧放热率比柴油低 ,缸内最大爆发压力和最大压力升高率比柴油低。由于喷油持续期延长 ,DME的燃烧持续期比柴油长 ,在上止点后 80° CA出现一个较大的放热峰值。     

车用二甲醚（DME）燃料润滑剂的研究与开发

二甲醚能替代柴油实现发动机高效低污染燃烧,但它的润滑性能差、有强的溶解性和清洗作用,从而使燃油系统的精密副的摩擦表面和气门、气门座磨损加快.从气体燃料基础润滑特性的研究着手,通过选择基础液、筛选各类添加剂,对润滑剂进行四球PB值评定和冷态磨损台架试验,先后进行了三代不同添加剂、不同添加量、不同运行持续期试验及长期行车试验,并首次在高频加压往复试验机(MPT-HFRR)测试,获得了二甲醚润滑剂的最佳配方.这种润滑剂的润滑性能好,挥发性能与二甲醚相近,不在摩擦表面形成漆膜;其加入量少,润滑剂使用成本低,可有效控制润滑添加剂参与燃烧时的不完全燃烧产物.研究结果表明,所开发的HIRI 1123润滑剂是一种综合性能优良的二甲醚润滑改进剂.     

二甲基醚（ＤＭＥ）喷雾一般牧场生的试验研究

介绍了在高压环境下对二甲基醚（ＤＭＥ）喷雾一般特性的试验研究结果,并与柴油的喷雾特性进行了比较。试验研究是在定容燃烧弹上进行的,用阴影法通过高速数字摄影机拍摄了二甲基醚和柴油的喷雾发展过程,应用计算机图像处理进行喷雾过程图像再现。研究结果表明：ＤＭＥ的喷雾贯穿蹁距离比柴油小,喷雾锥角比柴油大;在喷雾自由发展过程中,ＤＭＥ的蒸发速度比柴油快;环境密度对ＤＭＥ喷雾特性的影响与柴油相似,即密度增大,锥角增大,贯穿距离减小。在燃烧室壁面附近,柴油的喷雾锥角迅速增大,而ＤＭＥ喷雾锥角几乎没有明显的变化。     

二甲醚(DME)发动机燃油系统的试验研究

为了解DME燃油系统的一些基本特性,解决燃油系统与发动机匹配的问题,对原有的EFEP 657型喷油泵试验台进行了改造,使之满足DME喷油泵试验的要求;为使发动机燃用DME时产生与燃用柴油同等大小的功率,对DEM所需的油量进行了估算,在此基础上,对影响发动机的主要因素,如出油阀参数,凸轮型线,柱塞直径,喷油嘴喷孔等进行了分析选择,并对音速问题进行了讨论,最后提出了一套能够满足原机动力性和欧Ⅲ排放标准的燃油系统参数.     

直喷式柴油机燃用二甲基醚(DME)试验研究

介绍了在1100单缸直喷式柴油机上燃用DME的发动机试验研究结果。研究表明：通过增加循环供油量可使柴油机燃用DME后恢复到原机略低，同时缸内最大爆发压力降低，发动机碳烟排放为零，HC和CO排放比原机略高，NOx排放比原柴油机降低约50%以上，供油提前角减少，缺内最大爆发压力降低，NOx排放可进一步大幅度降低，但HC排放略有升高；加大喷孔直径，缸内爆发压力升高，NOx排放升高，HC和CO排放在中低负荷相差不大，但在大负荷工况有所升高。     

Water hyacinth (Eichhornia crassipes) biochar as an alternative cathode electrocatalyst in an air-cathode single chamber microbial fuel cell

In the present work, Water Hyacinth Biochar (WHB) was produced by pyrolysis at 900 °C and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), EDX-SEM, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) surface area and particle size analyses. The results indicate that WHB has Oxygen Reduction Reaction (ORR) catalytic activity, with an average of 2.58 electrons per oxygen molecule transferred from WHB for ORR. The ORR catalytic activity of WHB is attributed to its physical and chemical surface properties. The maximum power density produced from an air cathode single chamber microbial fuel cell (ACSC-MFC) with WHB as the ORR catalyst versus the Pt/C catalyst were 24.7 and 12.3 mWm⁻², respectively. This study demonstrates that Water Hyacinth Biochar can be used as an inexpensive catalyst for the ORR in microbial fuel cells.     

Direct dimethyl ether (DME) synthesis through a thermally coupled heat exchanger reactor

Compared to some of the alternative fuel candidates such as methane, methanol and Fischer–Tropsch fuels, dimethyl ether (DME) seems to be a superior candidate for high-quality diesel fuel in near future. The direct synthesis of DME from syngas would be more economical and beneficial in comparison with the indirect process via methanol synthesis. Multifunctional auto-thermal reactors are novel concepts in process intensification. A promising field of applications for these concepts could be the coupling of endothermic and exothermic reactions in heat exchanger reactors. Consequently, in this study, a double integrated reactor for DME synthesis (by direct synthesis from syngas) and hydrogen production (by the cyclohexane dehydrogenation) is modelled based on the heat exchanger reactors concept and a steady-state heterogeneous one-dimensional mathematical model is developed. The corresponding results are compared with the available data for a pipe-shell fixed bed reactor for direct DME synthesis which is operating at the same feed conditions. In this novel configuration, DME production increases about 600 Ton/year. Also, the effects of some operational parameters such as feed flow rates and the inlet temperatures of exothermic and endothermic sections on reactor behaviour are investigated. The performance of the reactor needs to be proven experimentally and tested over a range of parameters under practical operating conditions.     

Energy system aspects of hydrogen as an alternative fuel in transport

Considering the enormous ecological and economic importance of the transport sector the introduction of alternative fuels—together with drastic energy efficiency gains—will be a key to sustainable mobility, nationally as well as globally. However, the future role of alternative fuels cannot be examined from the isolated perspective of the transport sector. Interactions with the energy system as a whole have to be taken into account. This holds both for the issue of availability of energy sources as well as for allocation effects, resulting from the shift of renewable energy from the stationary sector to mobile applications. With emphasis on hydrogen as a transport fuel for private passenger cars, this paper discusses the energy systems impacts of various scenarios introducing hydrogen fueled vehicles in Germany. It identifies clear restrictions to an enhanced growth of clean hydrogen production from renewable energy sources (RES). Furthermore, it points at systems interdependencies that call for a priority use of RES electricity in stationary applications. Whereas hydrogen can play an increasing role in transport after 2030 the most important challenge is to exploit short–mid-term potentials of boosting car efficiency.     

高温环境下二甲基醚(DME)喷雾特性的实验研究

对二甲基醚（DME）在高温条件下的喷雾特性进行了实验研究。结果结果表明：与常温条件相比，DME喷雾体喷雾核心面积变小，喷雾体呈薄雾状发展，DME蒸发极为迅速；高温条件下喷油前期DME的嘴端压力比常温下小；在所实验的温度范围内，环境温度对喷雾体的贯穿距离没有影响；环境密度对喷雾体贯穿距离的影响也较小，环境密度增大时，贯穿距离略有减小。     

甲醇和二甲醚燃料在发动机中的应用现状

论述了我国发展甲醇和二甲醚燃料的必要性,并分析了甲醇和二甲醚(DME)作为发动机燃料的优势和不利因素,详细阐述了目前汽油机、柴油机和HCCI发动机燃用甲醇和二甲醚燃料的现状,指出了今后发动机代用燃料的发展方向。     

Auto-ignition during instationary jet evolution of dimethyl ether (DME) in a high-pressure atmosphere

The auto-ignition process during transient injection of gaseous dimethyl ether (DME) in a constant high-pressure atmosphere is studied experimentally by laser-optical methods and compared with numerical calculations. With different non-intrusive measurement techniques jet properties and auto-ignition are investigated at high temporal and spatial resolution. The open jet penetrates a constant pressure oxidative atmosphere of up to 4 MPa. During the transient evolution, the fuel jet entrains air at up to 720 K. The subsequent auto-ignition of the ignitable part of the jet occurs simultaneously over a wide spatial extension. The ignition delay times are not affected by variation of the nozzle exit velocity. Thus, the low-temperature oxidation is slow compared with the shorter time scales of mixing, so that chemical kinetics is dominating the process. The typical two-stage ignition is resolved optically with high-speed shadowgraphy at a sampling rate of 10 kHz. The 2D fields of jet velocity and transient mixture fraction are measured phase-coupled with Particle Image Velocimetry (PIV) and Tracer Laser Induced Fluorescence (LIF) during the time-frame of ignition. The instationary Probability Density Functions (PDF) of mixture fraction are described very well by Beta functions within the complete area of the open jet. Additional 1D flamelet simulations of the auto-ignition process are computed with a detailed reaction mechanism for DME [S. Fischer, F. Dryer, H. Curran, Int. J. Chem. Kinet. 32 (12) (2000) 713-740; H. Curran, S. Fischer, F. Dryer, Int. J. Chem. Kinet. 32 (12) (2000) 741-759]. Calculated ignition delay times are in very good agreement with the measured mean ignition delay times of 3 ms. Supplemental flamelet simulations address the influence of DME and air temperature, pressure and strain. Underneath a critical strain rate the air temperature is identified to be the most sensitive factor on ignition delay time.     

Multi-objective optimization of cassava-based fuel ethanol used as an alternative automotive fuel in Guangxi,China

Multi-objective optimization of net energy, external costs of environment pollutant-emissions, and cost of using cassava-based fuel ethanol as an alternative automotive fuel in Guangxi has been conducted based on its holistic life cycle, from feedstock production to fuel combustion. A new indicator, cost of net energy (CNE), linking net energy-yield, external cost of environment pollutant-emissions, and production cost (the lower the CNE reading, the better the total performance) of ethanol–gasoline blends, is proposed for carrying out multi-objective optimization. On the life-cycle basis, CNE of ethanol–gasoline blends is found to obtain its lowest value, i.e. 0.119  RMB/MJ, when processing fuel during the ethanol conversion stage was natural gas and the ratio of ethanol blended with gasoline was 5%. From the standpoint of the CNE indicator, the most viable implement form of cassava-based fuel ethanol should be used as one of oxygenate additives. The recommended processing fuel during ethanol conversion stage should be natural gas.