Investigation on the physical properties of the charcoal briquettes prepared from wood sawdust and cotton stalk

The physical properties of the charcoal briquettes prepared from biomass waste are usually poor. In the paper, an alternative approach to the charcoal briquette preparation from the densified biomass briquette by carbonization was addressed. The carbonization process of the biomass briquettes prepared from cotton stalk (CS), wood sawdust (WS) and their blends was performed in a fixed bed at 400~600°C. The variation in the mass and volume of the biomass briquettes before and after the carbonization process and the physical properties of the resulted charcoal briquettes were investigated. The results indicate that the physical properties of the charcoal briquettes including bulk density and compression strength decreased firstly and then increased as the temperature increased. CS charcoal briquettes with better physical properties showed more volume shrinkage than WS charcoal briquettes after the carbonization process. However, the physical properties of the charcoal briquettes from the blends were poorer than expected due to the co-pyrolysis characteristics of CS and WS.     

Depletion of forest resources in Sudan: Intervention options for optimal control

Agricultural expansion and over-cutting of trees for fuelwood are important causes of deforestation in arid and semi-arid countries such as Sudan. The consequence is increased desertification and high erosion and loss of soil nutrients leading to declining agricultural productivity. However, the social costs of the deforestation externality are not taken into account in present forest management and land use planning in Sudan leading to under-pricing and over-exploitation of the country's forest resources. This study evaluated the suitability of approaches commonly used by most forest resource management agencies for prediction of the state and control of harvesting of forest resources against alternative empirical simulation models using relevant information about economic behaviour of trading agents in the fuelwood market. Results showed the clear superiority of models integrating market behaviour over current approaches in the ability to better simulate real trends of wood consumption and hence depletion rates. The study also adopted an optimal control model to derive socially optimal forest harvesting regimes. The results showed that current rates of forest resource rent recovery and reforestation efforts are very far from optimal. Results also suggest that, in addition to optimal pricing and higher reforestation efforts, promotion and availability of fuel substitutes and investment in wood energy conversion efficiencies have a strong potential for curbing the problem of deforestation in Sudan.     

Modelling and measurements of heat transfer in charcoal from pyrolysis of large wood particles

The pyrolysis rate limiting heat transfer properties of charcoal from large wood particles are studied by comparing experiments and simulations of transient heat conduction in large charcoal samples. The interior temperatures in cylindrical charcoal samples of 20±2 mm radius were measured during heating from room temperature to 700°C in an inert atmosphere. Simulations are performed for two cases of constant material properties and for two cases of temperature dependent specific heat and/or effective thermal conductivity. The material properties of charcoal used in the simulations are found in literature related to modelling of wood pyrolysis. The simulations show that a constant thermal diffusivity of approximately 0.7 mm²/s agrees better with measured data than the assumption of temperature dependent material properties. Constant material properties are preferred due to simplicity, although the correct interpretation is that the increase in specific heat and effective thermal conductivity with temperature cancel each other.     

内燃机冷启动性能测试与评价

就内燃机冷启动性能的重要性、影响因素、试验过程与评价作了较全面、详尽的论述。并针对现代社会对内燃机的要求，提出了更全面反映内燃机冷启动性能的最新指标体系。     

管内强化换热元件综合热力性能分析及评价

针对强化换热元件的综合热力性能分析和评价问题,基于过程熵产分析的统一分析方法建立了管内综合热力性能分析方程,并以管内强化传热介绍了其应用。结果表明：该方法物理意义明确,简单易用,依据其不仅可通过参数分析获得各种方式的能量综合利用效果,而且还可依据其确定合理的流动工况参数、结构参数和合理的强化形式。图7参6     

Evaluation of sorghum hybrids for biomass production in central Italy

Two field experiments were carried out in 2005 and 2006 in central Italy in order to evaluate the biomass production and quality in eight sorghum hybrids, to define their biomass partitioning among leaves, panicles and stems and to identify which were the most adapted at early harvest. Sorghum showed a high potential in terms of biomass production in central Italy, with biomass dry yield of 25 t ha⁻¹ in average, adopting low input in terms of irrigation and fertilization. The most productive hybrids were H133 (26.3 t ha⁻¹) and H952 (25.9 t ha⁻¹) among the biomass hybrids and SS506 (27.3 t ha⁻¹) among the forage hybrids. The trends of dry weight and moisture content of biomass during the different hybrids growth cycles allowed to estimate the biomass production of each hybrids, hypothesizing an early harvest at 20 August with in-field drying of biomass. Early harvest reduced dry weight of biomass from 4.6% to 21.7%, depending of hybrids; SS506 and H128 showed to be the most adapted at early harvest. HHV and LHV of biomass showed average values higher in biomass hybrids (18.4 and 17.5 MJ kg⁻¹ d.m.) than in forage hybrids (17.7 and 16.8 MJ kg⁻¹ d.m.); while, ash content average values were lower in biomass hybrids (6.8% d.m.) than in forage hybrids (7.7% d.m.). The highest values of leaves + panicles partitioning in the forage hybrids increased ash content, reducing the quality of their biomass for thermal utilization; the biomass hybrids should be therefore preferable.     

车用涡轮增压器瞬态响应性评估与测试

基于车用涡轮增压器瞬态响应的影响因素,提出独立于内燃机的车用涡轮增压器瞬态响应评估指标D_x。通过数值模拟和试验的方法研究在不同终了转速下D_x随不同初始压比的变化以及转子转动惯量、涡轮效率和压气机效率对D_x影响。研究结果表明：试验结果与仿真结果吻合较好,证明该测试方法可用于涡轮增压器的瞬态性能测试以及增压器瞬态性能的影响因素研究。使用误差传播理论对试验测得的瞬态响应评估参数D_x值进行系统误差估计,试验测得的系统不确定度为1.35%。     

Evaluation of fuel options for a commercial mhd plant in India

The choice of fuels for a commercial open-cycle MHD generator is not as simple as for a conventional plant. After the commissioning operations and the power runs of the Indian pilot MHD plant, the question of early commercialization is being debated. In this context, this paper looks at the spectrum of fossil fuels available in India and evaluates their relative suitability for commercial MHD generators. The attainable plasma temperature, electrical conductivity and the available fuel energy at the combustor outlet are taken as the comparison yardsticks. Standard operating parameters for commercial installations have been assumed. The comparison, which in the Indian context has been limited to coal-based fuels and natural gas, indicates the latter as the fuel of choice followed by gasified coal.     

大型火电机组汽轮机通流状态评估技术的分析应用

对汽轮机通流状态经济性评估的基本概念进行了阐述,并对影响汽轮机通流效率的各项因素的作用机理进行了定性分析。通过汽轮机通流部分的经济性状态评估,可以利用相关的分析工具软件对影响汽轮机通流部分经济性的因素进行有效分析及计算,并为电厂大修中汽轮机内部通流检修工作确定检修的重点。以某一超临界660MW汽轮机为例,给出了汽轮机通流状态经济性评估的大修通流状态实测数据及评估结果,证明了通流状态评估技术的优越性。     

复杂阻尼结构汽轮机末级长叶片寿命评估相关研究进展及展望

目前汽轮机叶片设计和安全性考核主要采用的是以许用应力为基准的静强度准则和以安全倍率为基准的动强度准则,随着汽轮机设计制造水平的提高,尤其是近年来在超临界和超超临界大功率汽轮机中广泛采用具有复杂阻尼结构的长叶片,该方法已经表现出越来越多的局限性,建立一套从寿命损耗角度评估叶片安全性的方法十分必要。总结了近年来国内外在叶片寿命评估相关研究如静态应力分析、动态应力分析、叶片高周和低周疲劳寿命分析以及叶片水蚀疲劳分析等4个方面的研究进展,并对进一步深入研究提出了一些思路和方法。     

贝叶斯公式与模糊识别耦合方法在河流健康评价中的应用

为准确评价河流的健康程度,提出了基于贝叶斯公式与模糊识别耦合方法,分析了单个河流健康评价指标属某个等级的概率,用最大似然分类准则判定单个河流健康评价指标的评价等级,引入组合赋权法与相对隶属度综合确定各指标的权重,并将其应用于某市周边6条河流健康评价中。结果表明,除河流Ⅰ的健康评价结果为0.734之外,其他五条河流的评价结果在[0.586,0.628]之间。这表明仅有河流Ⅰ的评价等级为良,河流Ⅱ、Ⅲ、Ⅳ、Ⅴ的评价等级均为中等,河流Ⅵ的的综合评价结果为0.586,评价等级为差,评价结果与实际情况相符。可见基于贝叶斯公式与模糊识别耦合方法合理、可行,不仅提高了河流样本集的权重精确度,且更好地处理了不确定信息。     

区域水资源可持续发展评价模型的建立与应用

从可持续发展观点出发，建立了区域水资源可持续发展评价模型，并对浙江省三门县水资源进行了评价。结果表明，该模型具有简便、合理、可靠且信息量大等特点。     

Biomass productivity and wood energy of Salix species after 2 years growth in SRIC fertilized with wastewater sludge

The energy equivalent of willows in short-rotation intensive culture (SRIC) varies in terms of yield and woody biomass characteristics. Three willow species (Salix discolor Mühl., Salix petiolaris Smith and Salix viminalis L.) were planted on two sites, well-drained and poorly drained, in two different densities (20 000 and 30 000 plants per ha). Four doses of dried and granulated sludge were applied: the equivalents of 0, 100, 200 and 300 kg “available” N per ha. At the end of the second season, above-ground biomass was similar for S. discolor and S. viminalis, and greater than that of S. petiolaris on both sites and for all sludge treatments. On the well-drained site, each increment in the sludge dose significantly increased the performance of the species, regardless of plant density. Fertilized with a sludge dose equivalent to 300 kg N per ha, S. viminalis and S. discolor yielded 30.17 and 24.97 t/ha of dry matter respectively. On the poorly drained site, differences in performance were also observed between fertilized and unfertilized plots, but not among the various treatments. The calorific value of the wood of the three species being similar (19.21–19.59 kJ/g), the energy equivalent of a hectare of willows is proportional to the yield of each species. Thus the energy equivalent of S. viminalis and S. discolor is two to three times that of S. petiolaris. S. viminalis had the highest woody biomass quality, with an FVI (fuelwood value index) of 1030.58 (100%), followed by S. petiolaris with 954.25 (92.6%) and S. discolor with 849.08 (82.4%).     

油田污水源热泵的用能分析与经济性评价

介绍了胜利油田东二联污水源热泵原油加热试验项目的工艺流程,并进行了用能分析和经济性评价。结果表明,热泵系统的制热系数和一次能源利用率较高,分别为6.35和1.83;热泵系统可用能利用率很低,只有27.07%;燃油价格越高,采用加热炉加热的效益越差,采用污水源热泵加热方式的经济性越好;污水温度越高,热泵制热系数越高,制热效果越好,耗电越少。     

大型汽轮机运行状态的可拓评价理论与系统开发

在建立汽轮机运行状态评价指标的基础上,提出了一种可拓评价方法.基于可拓学的物元理论,建立了汽轮机运行状态的物元模型,引入可拓集合中的关联函数与关联度,由综合关联度的大小对汽轮机运行状态进行定性和定量评价,并开发了基于SIS实时/历史数据平台的汽轮机运行状态评价系统,最后通过实例验证了该方法的实用性.研究结果表明,该方法能快速而有效地识别汽轮机运行状态,从而为状态维修决策提供科学的依据.     

Evaluation on energy and thermal performance for residential envelopes in hot summer and cold winter zone of China

As a result of rapid economic growth in the last several decades, energy issue is becoming more and more important in today’s world because of a possible energy shortage in the future; the usage of residential electricity has increased rapidly in China and building energy efficiency is included as one of the 10 key programs targeting energy efficiency improvement in the 11th Five-Year Plan. In response to the growing concerns about energy conservation in residential buildings and its implications for the environment, systematic evaluation on energy and thermal Performance for residential envelops (EETP) is put forward to assess the energy efficiency of envelop designs and to calculate the energy consumption of cooling and heating systems. Hot summer and cold winter zone of China was selected for EETP analysis because of its rigorous climatic and huge energy consumption. The correlations between EETPs and electricity consumptions in cooling season, heating season, and the whole year were built in Shanghai, Changsha, Shaoguan and Chengdu, which represent A, B, C and D subzone of hot summer and cold winter zone in China, respectively. Illustrations indicate that the algorithm is simple and effective, energy and thermal performance of residential envelopes can be evaluated easily. The maximum allowable values of EETPs were determined when just meeting the compulsory indices of Standard JGJ134-2001, the corresponding allowable EETPs were also gained when achieving different energy-saving degrees on basis of it. EETP method can suggest possible ways to improve the energy efficiency for envelope designs of new building and retrofits of existing buildings and provide governments some useful information for the establishment of new policy on energy efficiency buildings. It has important meanings to carry out sustainable residential building designs with high thermal comfort and low energy consumption.     

节能评估中输变电损耗估算与评价方法的探讨

目前业内对节能评估报告中部分内容的理解和评价深度不足,输变电损耗的估算方法与评价是普遍欠缺的.主要是解决好变压器损耗、输电线路损耗、输变电损耗率的评价等几个方面的方法问题.通过对项目输变电损耗进行具体计算分析,使估算结果最接近实际,对项目的设计实施起到更好的指导作用.     

电站群非劣开发顺序多目标决策评价方法

用动态投入产出模型作为非劣电站开发顺序的区域经济系统响应的模拟分析模型;讨论了模型求解的关键技术－投资产品向量生成技术。采用层次分析法评价非劣序的区域经济系统响应之优劣,并藉此筛选最佳权衡解。     

Evaluation of hydrogen production by wind energy for agricultural and industrial sectors

Wind power potential by itself is not a good indicator of the suitability of a region for wind power generation for different purposes. Economic attractiveness is a better indicator in this regard as it stimulates the involvement of private businesses in this sector. Naturally, the shorter is the payback period or the time required to reach profitability, the more attractive will be the project. Considering the high wind energy potential of some regions of Iran, this study evaluates the wind energy available for generating electricity as well as hydrogen by industrial and agricultural sectors in four cities of Ardebil province, namely Ardebil, Khalkhal, Namin, and Meshkinshahr, and then conducts an econometric analysis accordingly. Wind power potentials are evaluated using the energy pattern factor and Weibull distribution function based on 5-year meteorological data of the studied regions. Economic evaluations are performed based on the present worth of incomes and costs, which are estimated for two models of wind turbines with 3.5 and 100 KW rated power. Results indicate that the cities of Namin and Ardebil with wind power densities of respectively 261.68 and 258.99 W/m² have the best condition. The economic analysis conducted for turbines shows that for Ardebil, installation of the 3.5 KW and 100 KW turbines will have a payback period of 13 and 5 years, respectively. For Khalkhal, Namin, and Meshkinshahr, the only feasible option is installation of the 100 KW turbine, which would result in a payback period of respectively 10.2, 6.1 and 8.7 years. Then it is investigated how much hydrogen can be gained if these private sectors invest in producing hydrogen using nominated wind turbines.