微生物选育技术在生物燃料乙醇生产中的应用

随着全球性能源危机、粮食危机和环境危机的到来,燃料乙醇作为汽油的替代品日益受到关注.应用微生物发酵技术将甘蔗、玉米、木薯和纤维类废弃物等转化为燃料乙醇,已成为解决世界能源危机的一条理想途径.通过对环境中各种微生物进行筛选分离和育种,可以得到转化能力较强的高效菌株,将这些高效菌株应用于燃料乙醇生产中,能够有效提高燃料乙醇的生产效率.文章对微生物选育技术在燃料乙醇生产中的应用进行了总结与展望.     

乙醇燃料的发展应用现状和前景

能源结构调整和降低环境污染推动了乙醇燃料的发展.本文介绍了国内外乙醇燃料的发展现状,对乙醇燃料和传统车用燃料的理化性质进行了比较,同时,就乙醇燃料应用于汽油机和柴油机上所带来的使用特点和问题进行了总结,并展望了未来乙醇燃料的发展前景.     

柴油-乙醇-四氢呋喃混合燃料的燃烧与排放特性

在一台6缸增压柴油机上开展了无水乙醇、四氢呋喃(THF)与柴油混合燃料对柴油机燃烧和排放影响的研究,所用燃料为纯柴油、体积分数为15％THF和85％柴油的柴油-THF混合燃料及10％乙醇、5％THF和85％柴油的柴油-乙醇-THF混合燃料.结果表明:添加5％THF可以明显改善柴油-乙醇混合燃料的互溶性,添加THF使发动...     

中国甘蔗燃料乙醇生产的技术、经济和环境可行性分析

我国甘蔗燃料乙醇产业的发展是以2001年国家基于石油替代战略而启动“变性燃料乙醇”和“车用燃料乙醇”计划为背景发展起来的。目前燃料乙醇发展的突出障碍是生产成本较高，因此，需要国家的大量补贴。文中借鉴巴西利用甘蔗发展低成本燃料乙醇的经验，对中国甘蔗燃料乙醇生产的技术成熟度、市场竞争力和环境影响进行了分析，并得出：中国用甘蔗生产燃料乙醇在工艺和设备上不存在根本性、长期性的障碍；在目前的燃料乙醇和食糖价格下，甘蔗燃料乙醇的生产具有相对优势；甘蔗燃料乙醇生产中对环境的负面影响在现有的环保技术条件下可以得到克服，并且还将促进温室气体减排。     

乙醇/柴油/甲酯混合燃料的燃烧与排放特性

对燃料甲酯作为乙醇／柴油混合燃料助溶剂的可行性进行了研究,并对比了柴油机分别使用柴油、乙醇／柴油／甲酯混合燃料、乙醇／甲酯混合燃料和纯甲酯燃料时的燃烧与排放特性。结果表明,燃料甲酯可用作乙醇／柴油的助溶剂。与原机相比,含氧燃料可以大幅度降低柴油机在中高负荷时的烟度,其中E30M70燃料的烟度最小。但当使用含有乙醇的混合燃料时,着火延迟,THC排放增加,且在中高负荷时的压力升高率大,NOx排放较高。     

乙醇燃料的研究发展与应用

乙醇是一种极具潜力的替代燃料,使用乙醇不但可以改善能源结构、减少对石油进口的依赖,同时可以降低汽车的有害排放。本文论述乙醇用作燃料的发展过程,并且分析其特性及应用前景。     

巴西“乙醇燃料”车大行其道

正梅洛先生平常在城里开车时,会给他的爱车加乙醇燃料;等到周末开车去老父亲的庄园探视时,才会加满汽油。"我这辆标致车是特殊的‘灵活燃料’车,既可以加汽油,也可以加乙醇燃料。"他对记者说。巴西是世界上发展燃料乙醇技术最早国家之一,距今已有40多年历史,车用乙醇燃料的使用深入人心。根据法律规定,目前巴西汽油中添加的     

基于有效能分析的玉米燃料乙醇可再生性研究

玉米燃料乙醇是一种化石燃料替代品,其可再生能力是评价其性能优劣的一个重要指标.从热力学的角度建立了基于有效能的玉米燃料乙醇可再生性分析模型,并提出一个考虑自然环境自修复能力及允许扰动程度用于修正可再牛性理论值的因子.研究结果表明,目前我国玉米燃料乙醇可再生因子的理论值为-2.14,具有不可再生性.文章最后指出了提高我国玉米燃料乙醇可再生能力的重要途径.     

乙醇重整燃料对内燃机充气效率的影响

提出乙醇重整燃料对发动机充气效率的影响的计算公式,可以预测完全燃用或者部分掺烧乙醇重整燃料对SI发动机充气效率和柴油机充气效率的影响。计算分析结果表明：乙醇重整燃料影响充气效率的主要因素是乙醇浓度和重整率,随着重整率的增加,乙醇重整发动机的充气效率有较大幅度下降,必将导致发动机的动力性能急剧下降,柴油机部分掺烧乙醇重整燃料对充气效率的影响较小。     

乙醇-柴油混合燃料的应用研究进展

为了有助于开展乙醇-柴油混合燃料在柴油机上的应用研究,本文首先介绍了乙醇的生产原料及其理化特性,分析了乙醇-柴油混合燃料的排放机理,讨论了乙醇-柴油混合燃料的研究进展,指出目前乙醇在柴油机上的混合燃烧主要分为两大类机内混合与机外混合燃料燃烧.最后重点以清华大学、吉林大学、上海交通大学为例,就各自对乙醇-柴油机外混合燃料燃烧研究的不同"亮点"分别进行论述,指出进一步选择合适的助溶剂以及恰当的着火改进剂等,可使乙醇-柴油混合燃料在柴油机上的应用早日实现.     

CFD investigating the effects of different operating conditions on the performance and the characteristics of a high-temperature PEMFC

The effects of different operating conditions on the performance and the characteristics of a high-temperature proton exchange membrane fuel cell (PEMFC) are investigated using a three-dimensional (3-D) computational fluid dynamics (CFD) fuel-cell model. This model consists of the thermal-hydraulic equations and the electrochemical equations. Different operating conditions studied in this paper include the inlet gas temperature, system pressure, and inlet gas flow rate, respectively. Corresponding experiments are also carried out to assess the accuracy of this CFD model. Under the different operating conditions, the PEMFC performance curves predicted by the model correspond well with the experimentally measured ones. The performance of PEMFC is improved as the increase in the inlet temperature, system pressure or flow rate, which is precisely captured by the CFD fuel cell model. In addition, the concentration polarization caused by the insufficient supply of fuel gas can be also simulated as the high-temperature PEMFC is operated at the higher current density. Based on the calculation results, the localized thermal-hydraulic characteristics within a PEMFC can be reasonably captured. These characteristics include the fuel gas distribution, temperature variation, liquid water saturation distribution, and membrane conductivity, etc.     

Performance and emission studies on port injection of hydrogen with varied flow rates with Diesel as an ignition source

Automobiles are one of the major sources of air pollution in the environment. In addition CO₂ emission, a product of complete combustion also has become a serious issue due to global warming effect. Hence the search for cleaner alternative fuels has become mandatory. Hydrogen is expected to be one of the most important fuels in the near future for solving the problems of air pollution and greenhouse gas problems (carbon dioxide), thereby protecting the environment. Hence in the present work, an experimental investigation has been carried out using hydrogen in the dual fuel mode in a Diesel engine system. In the study, a Diesel engine was converted into a dual fuel engine and hydrogen fuel was injected into the intake port while Diesel was injected directly inside the combustion chamber during the compression stroke. Diesel injected inside the combustion chamber will undergo combustion first which in-turn would ignite the hydrogen that will also assist the Diesel combustion. Using electronic control unit (ECU), the injection timings and injection durations were varied for hydrogen injection while for Diesel the injection timing was 23° crank angle (CA) before injection top dead centre (BITDC). Based on the performance, combustion and emission characteristics, the optimized injection timing was found to be 5° CA before gas exchange top dead centre (BGTDC) with injection duration of 30° CA for hydrogen Diesel dual fuel operation. The optimum hydrogen flow rate was found to be 7.5 lpm. Results indicate that the brake thermal efficiency in hydrogen Diesel dual fuel operation increases by 15% compared to Diesel fuel at 75% load. The NO_X emissions were higher by 1–2% in dual fuel operation at full load compared to Diesel. Smoke emissions are lower in the entire load spectra due to the absence of carbon in hydrogen fuel. The carbon monoxide (CO), carbon dioxide (CO₂) emissions were lesser in hydrogen Diesel dual fuel operation compared to Diesel. The use of hydrogen in the dual fuel mode in a Diesel engine improves the performance and reduces the exhaust emissions from the engine except for HC and NO_X emissions.     

Progress in the production and application of n-butanol as a biofuel

Butanol is a very competitive renewable biofuel for use in internal combustion engines given its many advantages. In this review, the properties of butanol are compared with the conventional gasoline, diesel fuel, and some widely used biofuels, i.e. methanol, ethanol, biodiesel. The comparison of fuel properties indicates that n-butanol has the potential to overcome the drawbacks brought by low-carbon alcohols or biodiesel. Then, the development of butanol production is reviewed and various methods for increasing fermentative butanol production are introduced in detailed, i.e. metabolic engineering of the Clostridia, advanced fermentation technique. The most costive part of the fermentation is the substrate, so methods involved in renewed substrates are also mentioned. Next, the applications of butanol as a biofuel are summarized from three aspects: (1) fundamental combustion experiments in some well-defined burning reactors; (2) a substitute for gasoline in spark ignition engine; (3) a substitute for diesel fuel in compression ignition engine. These studies demonstrate that butanol, as a potential second generation biofuel, is a better alternative for the gasoline or diesel fuel, from the viewpoints of combustion characteristics, engine performance, and exhaust emissions. However, butanol has not been intensively studied when compared to ethanol or biodiesel, for which considerable numbers of reports are available. Finally, some challenges and future research directions are outlined in the last section of this review.     

喷油器喷嘴结构参数对空化效应的影响

喷油器喷嘴内部的燃油的流动和空化直接影响燃油的喷射,又可造成喷嘴空蚀。基于不可压缩流体体积函数(VOF)多相流模型,模拟喷油器完整喷射周期内的燃油流动和空化特性,获得喷嘴空化形成及发展的关键区域和影响空化效应的关键结构参数,并分析其对流场及空化特性的影响规律。结果表明：较小针阀升程时,在针阀锥形表面台阶和喷孔下边缘位置处发生明显空化现象,当升程增加,空化集中分布在喷孔位置处,从倒圆处开始诱发,逐渐向下游延伸;针阀台阶夹角增大使得针阀表面台阶处和喷孔下缘的前部的局部空化增强,穴蚀更严重,且燃油流量减小,通过增大针阀座倒圆半径和喷孔直径锥度系数可有效地改善喷孔局部空化程度。     

Power management and design optimization of fuel cell/battery hybrid vehicles

Power management strategy is as significant as component sizing in achieving optimal fuel economy of a fuel cell hybrid vehicle (FCHV). We have formulated a combined power management/design optimization problem for the performance optimization of FCHVs. This includes subsystem-scaling models to predict the characteristics of components of different sizes. In addition, we designed a parameterizable and near-optimal controller for power management optimization. This controller, which is inspired by our stochastic dynamic programming results, can be included as design variables in system optimization problems. Simulation results demonstrate that combined optimization can efficiently provide excellent fuel economy.     

Bluetooth wireless monitoring,diagnosis and calibration interface for control system of fuel cell bus in Olympic demonstration

With the worldwide deterioration of the natural environment and the fossil fuel crisis, the possible commercialization of fuel cell vehicles has become a hot topic. In July 2008, Beijing started a clean public transportation plan for the 29th Olympic games. Three fuel cell city buses and 497 other low-emission vehicles are now serving the Olympic core area and Beijing urban areas. The fuel cell buses will operate along a fixed bus line for 1 year as a public demonstration of green energy vehicles. Due to the specialized nature of fuel cell engines and electrified power-train systems, measurement, monitoring and calibration devices are indispensable. Based on the latest Bluetooth wireless technology, a novel Bluetooth universal data interface was developed for the control system of the fuel cell city bus. On this platform, a series of wireless portable control auxiliary systems have been implemented, including wireless calibration, a monitoring system and an in-system programming platform, all of which are ensuring normal operation of the fuel cell buses used in the demonstration.     

Cycle analysis of an integrated solid oxide fuel cell and recuperative gas turbine with an air reheating system

Cycle simulation and analysis for two kinds of SOFC/GT hybrid systems were conducted with the help of the simulation tool: Aspen Custom Modeler. Two cycle schemes of recuperative heat exchanger (RHE) and exhaust gas recirculated (EGR) were described according to the air reheating method. The system performance with operating pressure, turbine inlet temperature and fuel cell load were studied based on the simulation results. Then the effects of oxygen utilization, fuel utilization, operating temperature and efficiencies of the gas turbine components on the system performance of the RHE cycle and the EGR cycle were discussed in detail. Simulation results indicated that the system optimum efficiency for the EGR air reheating cycle scheme was higher than that of the RHE cycle system. A higher pressure ratio would be available for the EGR cycle system in comparison with the RHE cycle. It was found that increasing fuel utilization or oxygen utilization would decrease fuel cell efficiency but improve the system efficiency for both of the RHE and EGR cycles. The efficiency of the RHE cycle hybrid system decreased as the fuel cell air inlet temperature increased. However, the system efficiency of EGR cycle increased with fuel cell air inlet temperature. The effect of turbine efficiency on the system efficiency was more obvious than the effect of the compressor and recuperator efficiencies among the gas turbine components. It was also indicated that improving the gas turbine component efficiencies for the RHE cycle increased system efficiency higher than that for the EGR cycle.     

Fuel cell system modeling for solid oxide fuel cell/gas turbine hybrid power plants, Part I: Modeling and simulation framework

A sustainable future power supply requires high fuel-to-electricity conversion efficiencies even in small-scale power plants. A promising technology to reach this goal is a hybrid power plant in which a gas turbine (GT) is coupled with a solid oxide fuel cell (SOFC). This paper presents a dynamic model of a pressurized SOFC system consisting of the fuel cell stack with combustion zone and balance-of-plant components such as desulphurization, humidification, reformer, ejector and heat exchangers. The model includes thermal coupling between the different components. A number of control loops for fuel and air flows as well as power management are integrated in order to keep the system within the desired operation window. Models and controls are implemented in a MATLAB/SIMULINK environment. Different hybrid cycles proposed earlier are discussed and a preferred cycle is developed. Simulation results show the prospects of the developed modeling and control system.     

High-efficiency power production from natural gas with carbon capture

A unique electricity generation process uses natural gas and solid oxide fuel cells at high electrical efficiency (74%HHV) and zero atmospheric emissions. The process contains a steam reformer heat-integrated with the fuel cells to provide the heat necessary for reforming. The fuel cells are powered with H₂ and avoid carbon deposition issues. 100% CO₂ capture is achieved downstream of the fuel cells with very little energy penalty using a multi-stage flash cascade process, where high-purity water is produced as a side product. Alternative reforming techniques such as CO₂ reforming, autothermal reforming, and partial oxidation are considered. The capital and energy costs of the proposed process are considered to determine the levelized cost of electricity, which is low when compared to other similar carbon capture-enabled processes.