Energy and exergy analysis of a solid-oxide fuel cell power generation system for an aerial vehicle (ISSA- 2015–139)

This paper presents the performance of the solid-oxide fuel cell/gas turbine hybrid power generation system with heat recovery waste unit based on the energy and exergy analyses. The effect of air inlet temperature and air/fuel ratio on exergy destruction and network output is determined. For the numerical calculations, air inlet temperature and air fuel ratio are increased from 273 to 373 K and from 40 to 60, respectively. The results of the numerical calculations bring out that total exergy destruction quantity increases with the increase of air inlet temperature and air/fuel ratio. Furthermore, the maximum system overall first and second law efficiencies are obtained in the cases of air inlet temperature and air/fuel ratio equal to 273 K and 60, respectively, and these values are 62.09% and 54.91%.     

A low pressure direct gas injection system for a four stroke LPG: Diesel dual fuel engine

Internal combustion engines running on gaseous fuels produce low torque because the inducted gaseous fuel displaces air and reduces the volumetric efficiency. This can be overcome by injecting the gaseous fuel directly into the cylinder after the intake of air is completed. This work is a step in developing and demonstrating a cost effective system, as such systems are not readily available for small applications. A low-pressure gas injector was mounted on the cylinder barrel of a fully instrumented dual fuel engine. Its location is such that the injector will be exposed to the cylinder gases about 65.5 degrees before bottom dead center, where the cylinder pressure and temperature will be relatively low. An electronic controller was also developed to time the injection process to occur after the intake valve closes and also to control the duration of injection (quantity). Experiments were conducted with LPG (Liquefied petroleum gas) as the primary fuel that was injected with this new system and diesel as the pilot fuel at the rated speed of 1500 rpm with different amounts of LPG at 80% and 100% load. Comparisons of performance, combustion and emissions with the conventional manifold injection of LPG were done. The system allowed greater amounts of LPG to be used without knock as compared to manifold injection. On the whole the developed system has potential for application in small dual fuel and spark ignited gas engines and can be taken up for further optimization.     

一种快速测定化学需氧量(COD)的方法

提出用混酸来代替单一酸测定废水中的化学需氧量(COD)含量的方法。采用混酸(硫酸∶磷酸=4∶1)、重铬酸钾反应体系,氧化反应时间由标准方法的2h缩短为15min,是原来的1/8。用两种方法分别测试了标准物质所配制的废水和实际废水,经t检验和相关性分析,两种测试方法间不存在显著性差异,相关系数为0.95,相关性良好,同时实验得出本方法的检测限为5.15mg/L。本方法由于具有反应时间短,节省药剂和电费等优点,具有一定的可行性。     

火灾闪燃-现象突变模式之研究

近年来,各国消防学者鉴于多人死亡,火灾惨案不断发生,遂开始深入探讨造成火场内人员死亡之主要原因所在。结果发现：“闪燃现象”是否出现是造成人命伤亡及财物大量损失之关键因素。     

基于能值方法的甘薯燃料乙醇产业生态系统分析

发展燃料乙醇已成为替代能源战略下的成熟模式,但传统燃料乙醇生产的污染问题严重影响了燃料乙醇的生存和发展,因此建立以燃料乙醇生产为核心企业,包括由原料种植者、乙醇生产者、分解者、资源回收利用者等一系列利益相关者组成的产业生态系统,已成为燃料乙醇可持续发展的有效途径. 根据燃料乙醇生产过程中对废物处理和资源化利用情况,将其划分成传统生产方案(方案Ⅰ)、废物处理生产方案(方案Ⅱ)和产业生态系统方案(方案Ⅲ),并采用改进后的能值分析方法及指标体系对3种生产方案进行比较分析. 结果表明:与方案Ⅰ相比,通过废物处理和中水回用,方案Ⅱ的ε_EYR(能值产出率)提高了59.37%,ε_ELR(环境负荷率)降低了75.39%;延长产业链,增加循环利用方式后,方案Ⅲ比方案Ⅰ的ε_EYR提高了86.19%,ε_ELR降低了82.98%. 3种生产方案的可持续发展能力为方案Ⅰ<方案Ⅱ<方案Ⅲ.      

高里程出租车的排放控制措施

出租车排放是城市大气污染的重要来源,对高排放出租车加严管理是改善空气质量的有效手段之一.在北京市选取6辆有代表性的高里程汽油出租车,较全面地评估了维护保养、更换三元催化器对出租车油耗和排放的影响,以及三元催化器在更换后的老化情况.研究表明:常规的维护保养可显著改善车辆的燃油经济性,保养后车辆的100 km油耗比原车降低了2%～4%,但对THC和NOx排放的影响很小.原车排放越高,更换三元催化器的减排效果越显著,且更换第一级三元催化器(前三元催化器)和同时更换第一、二级三元催化器(前、后三元催化器)的减排效果差别较小.更换三元催化器后行驶里程约18.5×104 km时,有4辆出租车对CO、THC和NOx的减排比例仍保持在45%、26%和29%的平均水平,说明更换三元催化器后,在约20×104km的行驶里程内对气态污染物能保持较好的减排效果.      

基于FLACS的CH4/CO2/air混合气爆炸参数分析

利用FLACS软件分析初始压力、初始温度对CH4/CO2/air混合气的爆炸温度、最大爆炸压力的影响;并与计算值对比。结果表明:①初始压力对爆炸温度、爆炸前后压力比影响可以忽略。常温变压条件下二氧化碳浓度增加,爆炸温度与爆炸前后压力比基本呈线性降低。常压变温条件较复杂,二氧化碳浓度升高爆炸温度降低;初始温度对低浓度（<15%）二氧化碳混合气爆炸温度几乎没有影响,而高浓度（>15%）二氧化碳混合气爆炸温度随初始温度增加而升高;最大爆炸压力随二氧化碳浓度以及温度升高而降低。②在设定条件下,低浓度（5%~10%）二氧化碳混合气爆炸温度计算值与模拟值相对误差小于5.5%,吻合较好;最大爆炸压力计算值与模拟值相对误差在6.5%～10.5%之间。     

Nitrogen recovery from wastewater using microbial fuel cells

Nitrogen is one of major contaminants in wastewater; however, nitrogen, as bio-elements for crop growth, is the indispensable fertilizer in agriculture. In this study, two-chamber microbial fuel cells (MFCs) were first operated with microorganisms in anode chamber and potassium ferricyanide as catholyte. After being successfully startup, the two-chamber MFCs were re-constructed to three-chamber MFCs which were used to recover the NO3−−N and NH4+−N of synthetic wastewater into value-added nitrogenous fertilizer from cathode chamber and anode chamber, respectively. Ferric nitrate was used as the sole electron acceptor in cathode, which also was used to evaluate the NO3−−N recover efficiency in the case major anion of NO3− in cathode. The output voltage of these MFCs was about 600–700 mV at an external load of 500 Ω. About 47% NH4+−N in anode chamber and 83% NO3−−N in cathode chamber could be recovered. Higher current density can selectively improve the recovery efficiency of both NH4+−N and NO3−−N. The study demonstrated a nitrogen recovery process from synthetic wastewater using three-chamber MFCs.     

外源葡萄糖对麦秸厌氧发酵产沼气的影响

为进一步阐释混合厌氧发酵的内在机制,在中温(35±1)℃条件下,以麦秸为原料,以葡萄糖为外源易分解有机碳,采用批式发酵方式,进行了葡萄糖不同添加量和不同添加方式对秸秆厌氧发酵产沼气影响试验。结果表明,在试验初始添加葡萄糖可提高日产气量,但葡萄糖添加量太少对提高秸秆总固体(TS)产气量无促进作用,当葡萄糖添加量为秸秆TS质量的6%时获得最大秸秆TS产气量,为303.13 m L·g-1,继续增加葡萄糖添加量,秸秆TS产气量反而降低;在秸秆厌氧发酵日产气量下降阶段一次性或者分次添加葡萄糖对促进秸秆厌氧发酵产沼气均无效果,仅在试验初始一次性添加秸秆TS质量6%的葡萄糖时对秸秆厌氧发酵产沼气有促进作用,秸秆TS产气量较对照提高9.24%;添加葡萄糖对秸秆厌氧发酵过程产气中甲烷含量无明显影响,但提高累积产气中甲烷平均含量,且在日产气量下降后添加葡萄糖的效果更好,但这种促进效果与对照间差异并不显著。综合以上结果,在试验初始一次性添加秸秆TS质量6%的葡萄糖可以获得最佳的产气效果。     

An interval joint-probabilistic programming method for solid waste management: a case study for the city of Tianjin, China

Currently, environmental protection and resources conservation continue to be challenges faced by solid-waste managers in China. These challenges are being further compounded by rapid socioeconomic devel- opment and population growth associated with increased waste generation rates and decreased waste disposal capacities. In response to these challenges, an interval joint-probabilistic mixed-integer programming （IJMP） method is developed for supporting long-term planning of waste management activities in the city of Tianjin, which is one of the largest municipalities in the northern part of China. In the IJMP, joint probabilistic constraints are introduced into an interval-parameter mixed-integer programming framework, such that uncertainties presented in terms of interval values and random variables can be reflected. Moreover, a number of violation levels for the waste-management-capacity constraints are examined, which can facilitate in-depth analyses of tradeoffs among economic objective and system-failure risk. The results indicate that reasonable solutions have been generated. They are valuable for supporting the adjustment of the city＇s existing waste-management practices and the long- term planning of the city＇s waste-management facilities.