废弃油脂生物柴油掺水微乳化燃料燃烧和排放性能研究

利用废弃油脂制备生物柴油不仅具有可观的经济效益,而且具有良好的社会效益和环境效益．为研究生物柴油掺水微乳化的燃烧和排放性能,在同一台双缸四冲程直喷式柴油机上进行了对比试验,测量燃料的燃烧压力和排放浓度．研究结果表明：与生物柴油相比,生物柴油掺水微乳化燃料的峰值燃烧压力的相对高低随发动机负荷变化．在排放特性中,生物柴油掺水微乳化燃料的烟度和NOx排放量显著降低,这证明掺水微乳化燃料能够改善燃烧状况,控制柴油机主要污染物排放．     

微转子发动机的三区准维模型燃烧计算研究

分析了微转子发动机的燃烧特点,在双区准维模型的基础上引入壁面熄火区,提出了三区准维模型.编制了适用于微转子发动机燃烧的计算程序,计算了三区准维模型和双区准维模型下的微转子发动机燃烧过程.通过对计算结果与U. C.Berkeley试验数据比较分析,说明了三区准维模型的合理性.     

微转子发动机燃烧计算中壁面熄火效应的研究

分析微转子发动机的微小燃烧室内燃烧特点后,讨论了发动机燃烧室微燃烧中熄火距离的影响因素.并在三区准维模型的基础上,对比计算了不同熄火距离的燃烧特性.根据壁面熄火效应随熄火距离增大而增大,提出了减小熄火效应的措施.     

采用并行计算和简化机理的HCCI发动机多维模拟

HCCI燃烧过程多维数值模拟十分耗时.采用并行计算和简化机理对HCCI燃烧过程多维CFD模拟计算进行了加速对比.研究基于16-CPU计算机集群系统,采用消息传递的并行算法(Message-Passing Interface,MPI)方式计算.结果表明,内燃机HCCI燃烧多维燃烧模拟,采用8个CPU能获得最大收益:纯流动计算加速5倍,耦合化学反应流动计算加速4倍,简化反应机理又可加速9倍.通过优化选择并行计算CPU数量和反应机理,使得HCCI发动机单个循环模拟时间由一个月缩短到一天,大大提高了汽车发动机燃烧模拟计算的效率.而且采用三维CFD耦合化学反应的模拟计算,可以解析HCCI发动机着火燃烧过程,提供详细的流动、燃烧和排放物生成的瞬态信息.     

微管内氢气燃烧变参数研究

针对微尺度燃烧的特点,在传热分析的基础上,建立了微型管内氢-空气预混合气的燃烧模型,对0.2 mm微管内氢气空气预混燃烧进行了变参数研究.结果表明:对于0.2 mm微管,适当的氢氧混合比,火焰可以实现稳定持续燃烧;燃烧室尺度越小,散热量越大,最大可达到总放热量的22%左右;当量比接近0.8时,有最高燃烧温度和最高的氢气转化率,接近100%;入口应该控制在较小流速来实现较高的燃烧效率.     

射流燃烧技术在车用汽油机上的应用研究

本介绍了射流燃烧室在车用汽油机上的应用研究。汽油机射流燃烧室具有独特的结构，在压缩和燃烧过程中燃烧室内能形成强烈的微涡流，因此它可以有效地抑制发动机的爆震，且在燃用相同辛烷值燃料时能提高发动机的压缩比，并形成快速燃烧和稀混合气燃烧。这种燃烧系统在几种常用汽油机上的应用表明，发动机性能得到了明显的改善，特别是燃料消耗率和排气污染显降低。     

高能点火及滚流强化对直喷汽油机稀燃的影响

为了清晰地观察缸内的状态,采用配备光学玻璃缸套的单缸发动机．粒子图像测速技术(PIV)用于对进气道高滚流改造进行量化评价,相比原始进气道,滚流比为原来的1.67倍．点火能量从65 m J增加到300 m J,在无油喷射状态下,高能点火的电弧更长,但长电弧有被短路的可能．长电弧持续时间更长,峰值面积约为普通点火的4倍．研究了点火能量和滚流强度在不同过量空气系数下对燃烧稳定性、稀燃极限和燃烧过程的影响．结果表明：高能点火能使稀燃极限的过量空气系数扩大0.2,而高滚流能使燃烧循环变动降低50%．在微观层面上,火焰变动存在显著差异．高能点火较大的火焰变动有助于初始火核的形成和火焰的传播．累积放热时刻(MFB 50-90)这段时间内稳定的火焰对整体燃烧稳定性起主导作用,是高能点火能扩大稀燃极限的重要原因．     

乳化油油滴着火燃烧现象的实验研究

对高温炉中乳化油油滴的着火燃烧现象，特别是微爆炸现象进行了观测研究；测量了着火延迟时间和燃烧时间，分析了氛围气温度、油滴直径、乳化剂加率以及水添加率等因素对着火延迟、燃烧时间及微爆炸过程的影响。研究结果表明：水添加率小的乳化油反而易发生微爆炸现象；增大油滴直径，减少乳化剂添加率和提高氛围气温度都有利于产生微爆炸现象。     

微小型燃烧技术

近年来燃烧技术有了长足的进步和很多新发展，出现一些崭新的燃烧技术和燃烧设备，综合分析介绍几种新型的微小型燃烧技术，包括韩国KOCAT公司设计的一种紧凑式高性能燃烧系统，微通道型燃烧装置等，为设计与改进有关的燃烧器作准备。     

高强化柴油机燃烧过程的优化研究

以某大功率柴油机为研究对象,采用仿真和试验相结合的方法,在保持动力性和经济性不变的条件下,通过燃烧过程优化研究,采用小口径直口ω形1#燃烧室和8×Ф0.42 mm的喷油嘴,将发动机最高燃烧压力从15.5 MPa降低到14.5 MPa以下,提高了发动机的可靠性;将发动机的过量空气系数从2.1降低到1.9以下,缩小了空气滤的体积,降低了整车的重量,提高了车辆的机动性和灵活性.     

能源技术在微型无人机的应用

动力装置是微型飞行器发展的关键技术之一。目前比较成熟的微型飞行器的能源技术主要有锂电池、微型内燃机和微型燃料电池，已有部分定型产品出现在微型无人机样机中。而新型能源技术，主要包括往复式仿生化学肌肉和波束推进等，正处于实验研制阶段。本文重点综述了上述几种微型无人机能源技术在国内外的研究现状，比较各自的优缺点，并提出了未来微型飞行器能源技术研究发展的趋势。     

Fuel cells for airborne usage: Energy storage comparison

The global drone market is growing every year. The number of applications is increasing: from search and rescue, security, surveillance to science and research and unmanned cargo systems.A limiting factor for drone exploitation is that for the energy storage, normally, a battery is used and this solution affects flight time. A possible solution could be the utilization of fuel cells. This paper focuses on the utilization of fuel cells power as an alternative solution for drone propulsion.The aim of the study is to determine when it is more appropriate, in terms of mass, to use a battery or a hybrid (fuel cell + battery) system to power drones. To compare the different systems, a numerical simulation model has been developed in order to choose the best power system once the drone operation profile has been defined.The model allows comparing different type of fuels and battery systems. The data to tune the model have been taken from commercial products, today already available. The simulation model considers a light-weight open-air cathode PEM (Polymer Exchange Membrane) fuel cell. The stack power output is chosen according to the mission profile and rages from 200 W to 1000 W.The presented results show that, for the considered drone segment, multirotor drones with weight of 7 kg at take-off, lithium batteries are still the best choice for time flight shorter than about 1 h. A hybrid system, appears to be interesting for longer flights. For example, it has been calculated that a hybrid quadcopter drone with a mass of 7 kg, considering a flight profile that requires 1089 Wh can be powered with a 4.4 kg hybrid system composed by a 500 W and 1.4 kg PEM fuel cell system, 1.9 kg hydrogen composite pressure vessel and a 0.8 kg lithium battery. The same amount of energy can be stored in a lithium battery with a weight of about 6.6 kg. These means a weight saving of more than 30%. The hybrid system, in term of weight, is even more convenient for flight profiles that require more energy.     

Investigations on fabrication and lifetime performance of self – air breathing direct hydrogen micro fuel cells

There is an ever – increasing demand for more powerful, compact and longer – life power modules for portable electronic devices for leisure, communication and computing. Micro fuel cells have the potential to replace battery packs for portable electronic appliances because of their high power density, longer operating and standby times, and substantially shorter recharging times. However, fuel cells have stringent operating requirements, including no fuel leakage, water formed in the electrochemical reactions, heat dissipation, robustness, easy and safe use, and reliability. Due to the large market potential, several companies are currently involved in the development of micro fuel cells. For application of fuel cells as a battery charger or in a battery replacement market, the cells require simplification in terms of their construction and operation and must have volumetric power densities equivalent to or better than those of existing battery power packs. This paper discusses results of investigation on methods and materials for direct hydrogen micro fuel cells as well as the lifetime performance of single cells and 2 W_e arrays. The paper also reviews the global technology development status for the direct hydrogen micro fuel cell and compares its salient features with other types of micro fuel cells.     

Managing peak loads in energy grids: Comparative economic analysis

One of the key issues in modern energy technology is managing the imbalance between the generated power and the load, particularly during times of peak demand. The increasing use of renewable energy sources makes this problem even more acute. Various existing technologies, including stationary battery energy storage systems (BESS), can be employed to provide additional power during peak demand times. In the future, integration of on-board batteries of the growing fleet of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) into the grid can provide power during peak demand hours (vehicle-to-grid, or V2G technology).This work provides cost estimates of managing peak energy demands using traditional technologies, such as maneuverable power plants, conventional hydroelectric, pumped storage plants and peaker generators, as well as BESS and V2G technologies. The derived estimates provide both per kWh and kW year of energy supplied to the grid. The analysis demonstrates that the use of battery storage is economically justified for short peak demand periods of <1 h. For longer durations, the most suitable technology remains the use of maneuverable steam gas power plants, gas turbine,reciprocating gas engine peaker generators, conventional hydroelectric, pumped storage plants.     

Hybrid electric vehicles and electrochemical storage systems — a technology push–pull couple

In the advance of fuel cell electric vehicles (EV), hybrid electric vehicles (HEV) can contribute to reduced emissions and energy consumption of personal cars as a short term solution. Trade-offs reveal better emission control for series hybrid vehicles, while parallel hybrid vehicles with different drive trains may significantly reduce fuel consumption as well. At present, costs and marketing considerations favor parallel hybrid vehicles making use of small, high power batteries. With ultra high power density cells in development, exceeding 1 kW/kg, high power batteries can be provided by adapting a technology closely related to consumer cell production. Energy consumption and emissions may benefit from regenerative braking and smoothing of the internal combustion engine (ICE) response as well, with limited additional battery weight. High power supercapacitors may assist the achievement of this goal. Problems to be solved in practice comprise battery management to assure equilibration of individual cell state-of-charge for long battery life without maintenance, and efficient strategies for low energy consumption.     

动力电池支撑架结构设计及散热性能分析

可再生能源的发展势必带动动力电池的发展,在促进退役动力电池循环利用方面也将取得较大成效,在动力电池发展过程中,其安全性是值得广泛关注的重点问题,为提高动力锂电池组放电时散热效率,设计电池组支撑架,采用计算机仿真的方法研究不同支撑架结构、不同工质、不同流速下18650型锂电池构成的动力电池组的热性能。通过对空气和水2种工质流体、工质流速大小、工质入口位置等参数进行组合仿真分析,结果表明,随着工质流速的增加,电池组及支撑架表面的最高温度逐渐降低,当工质流速大于10 m/s时趋于稳定;适当的工质流入口的位置可增强降温效果,在低流速状态下,空气和水分别作为冷却工质时,纵向包裹型电池支撑架比横向包裹型电池支撑架电池组中表面温度分别降低了2.64%和1.86%;在高流速状态下,空气和水分别作为冷却工质时,纵向包裹型电池支撑架比横向包裹型电池支撑架电池组中表面温度分别降低了3.15%和1.83%。动力电池支撑架结构设计可为后续电池热控制提供理论参考。     

A Life Cycle Assessment of lithium battery and hydrogen-FC powered electric bicycles: Searching for cleaner solutions to urban mobility

Smart mobility is day by day becoming one of the crucial issues to address in order to reduce environmental impacts such as global warming, acidification, photochemical smog, among others. The growing concerns about urban air quality are the driving force for cleaner and more efficient transport systems. Several new transport technologies are being developed, in particular concerning electric vehicles, considered a suitable solution to urban air pollution problems. However, these vehicles require electric and electronic devices that might give rise to a new set of environmental problems in their production, operation and disposal phases. Are electric vehicles a really cleaner solution? This paper aims at answering this question, by comparing two kinds of vehicle, a lithium battery powered electric bike and a hydrogen-fuel cell operated one, using internal combustion engine vehicles as benchmark. The fuel cell bike uses a proton exchange membrane fuel cell (PEMFC) to convert hydrogen into electricity. In this study, Life Cycle Assessment is applied to evaluate the environmental burdens of the production of these two vehicles and compare their environmental performances per 100 km travelled. The study, not only includes vehicle road operation but also embraces production and distribution of bikes, electric battery, PEMFC and energy carriers (electricity and hydrogen) over the vehicle's entire lifetime. The LCA evaluation of the vehicle production phases shows that the construction of the H-bike results more impacting than the E-bike in all the considered categories due to the presence of more complex components technology. Instead, when the boundary is shifted to the operational phases of the vehicles including the energy carriers production, the situation is reversed and the environmental performance of the H-bike results better than the one of E-bike.     

A new application of the UltraBattery to hybrid fuel cell vehicles

This study involves investigation of fuel cell hybrid vehicles. The main power source in the dynamic configuration is a proton exchange membrane fuel cell. An energy performance comparison is conducted between the use of a lithium‐ion battery (Automotive Energy Supply Corporation, Japan) and the UltraBattery (Furukawa Battery Company, Japan) as auxiliary power sources. The MATLAB/Simulink for simulation is used to observe dynamic behavior and overall performance. This study describes the simulation frameworks of the proton exchange membrane fuel cell, ultracapacitor, lead–acid battery, and UltraBattery. Then, the Economic Commission for Europe 40 driving cycle is used to test and investigate the performance of the fuel cell hybrid vehicle. Four energy output models are adopted to simulate the energy demand and the energy motor output of the dual power source, namely the high‐load demand, general demand, low‐load demand, and charge models. The simulation results indicate that the lithium battery recycles 0.1% more work compared with the UltraBattery. Regarding fuel economy, the UltraBattery is only 0.1% inferior to the lithium battery. The expected cost of an UltraBattery with the same specifications is 35% less than that of a lithium battery. Considering fuel economy and cost simultaneously, the UltraBattery can compete with the lithium battery. Copyright © 2015 John Wiley & Sons, Ltd.     

An actively controlled fuel cell/battery hybrid to meet pulsed power demands

This paper presents the experimental results of an actively controlled fuel cell/battery hybrid power source topology that can be widely used in many applications, such as portable electronic devices, communication equipment, spacecraft power systems, and electric vehicles, in which the power demand is impulsive rather than constant. A step-down DC/DC power converter is incorporated to actively control the power flow between the fuel cell and the battery to achieve both high power and high energy densities. The results show that the hybrid power source can achieve much greater specific power and power density than the fuel cell alone. This paper first demonstrates that an actively controlled hybrid with a 35 W hydrogen-fueled polymer electrolyte membrane fuel cell and a lithium-ion battery pack of six cells yielded a peak power of 100 W, about three times as high as the fuel cell alone can supply, while causing a very limited (10%) weight increase to the whole system. After that, another hybrid source using a different battery array (eight cells) was investigated to further validate the control strategy and to show the flexibility and generality of the hybrid source design. The experimental data show that the hybrid source using an eight-cell battery supplied a peak power of 135 W, about four times that of the fuel cell alone. Finally, three power sources including the fuel cell alone and the two hybrids studied were compared in terms of specific power, power density, volume, weight, etc. The design presented here can be scaled to larger or smaller power capacities for a variety of applications.     

Research and development of on-board hydrogen-producing fuel cell vehicles

Combining with the characteristics of different types of electric vehicles, the on-board hydrogen-producing fuel cell vehicle design is adopted, which eliminates the problems about the high-pressure hydrogen storage and the hydrogenation process. The fuel cell is used as the main power source to drive the motor, and the lithium battery is used as the auxiliary power source to accelerate and recycle energy in order to meet the special requirements, like energy recovery, power and dynamic characteristics, of fuel cell vehicles. On the ADVISOR simulation platform based on MATLAB/Simulink environment, a hybrid drive model and a pure fuel cell drive model are built, and simulation and comparative analysis are performed. In the hybrid drive model, fuel cells and lithium batteries work in the highly efficient and safe operating areas respectively, and the output power of fuel cell has small fluctuations, improving energy utilization efficiency and extending the service life of the fuel cell. At the same time, the charge and discharge of the lithium battery can be effectively managed to ensure the safety of charging and prolong the service life of the lithium battery.