电焊熔珠对棉布和聚氨酯泡沫的引燃能力研究

研究了加载电压对电焊熔珠数目和粒径分布的影响,在模拟装置上实验了电焊对棉布、聚氨酯泡沫和纸张的引燃性能.结果表明,随着加载电压升高,电焊熔珠的数目逐渐减少,熔珠粒径逐渐增大,引燃能力逐渐增强.固体材料性质对电焊熔珠引燃能力也有很大影响,表面粗糙,易蓄热材料容易被点燃.电焊熔珠引燃棉布、聚氨酯泡沫和纸张的临界电压为37.5V、40V和45V.     

油品引燃时间的影响因素研究

以激光作为强辐射源对煤油,轻柴油和重柴油进行了直接引燃试验,研究了引燃时间受入射辐射热强度,油品性质和热辐射入射角度影响的关系。     

Influence of different ignition delay times on the pressure rise rate in hybrid mixture explosions in the 20-L sphere

For the development of a standardized method for measuring the explosion safety characteristics of combustible hybrid dust/vapor mixtures, the influence of the ignition delay time needs to be investigated. The ignition delay time, defined as the time between the injection of dust and the activation of the ignition source, is related to the turbulence of the mixture and thus to the pressure rise rate. The ignition source for pure vapors, however, has to be activated in a quiescent atmosphere according to the standards. Nevertheless, when measuring the explosion safety characteristics of hybrid mixtures, it is important that the dust be in suspension around the igniter. Like pure dust/air mixtures, hybrid dust/vapor/air mixtures need to be ignited in a turbulent atmosphere to keep the dust in suspension.This work will therefore investigate the influence of ignition delay times on the severity of hybrid explosions. It was generally found that at shorter ignition delay times, (dp/dt)_ex increased due to higher turbulence and decreases as the dust sinks to the bottom of the 20 L-sphere. This effect is more pronounced for hybrid mixtures with higher vapor content compared to dust content.     

Inerting effect of CaCO3 powder on flame spread of wood dust layer

The effect of CaCO₃ powder, a typical inert dust, on the flame spread characteristics of wood dust layers was studied using an experimental device to understand the ignition characteristics of and develop inert explosion-proof technology for deposited wood dust. The results showed that the flame spread velocity (FSV) of the mixed dust layer was affected by the dispersion effect of CaCO₃ powder and physical heat absorption. As the CaCO₃ powder mass fraction increased, the FSV of the dust layer first increased and then decreased, reaching a peak at a 50% mass fraction. Moreover, the front-end temperature of the flame gradually decreased, and the red spark faded. The combustion reaction of the mixed dust layer could be more completed, and the colour of the combustion residue changed from charcoal black to charcoal grey. The coupling effect of the initial temperature and wind speed can promote an increase in the FSV in the mixed dust layer. The Gauss–Amp model of the FSV of the wood dust layer and mass fraction of CaCO₃ powder showed that the peak of the FSV occurred when the mass fraction of CaCO₃ powder was between 40 and 50%. Thus, a good inerting and explosion-proof effect can be achieved by using CaCO₃ powder with a mass fraction of more than 50%; it can improve the whole inerting process. Inert explosion-proof technology should be considered when assessing fire and explosion risk of dust in real process industry situations.     

Combustion performance and emission characteristics on HCCI engine of waste plastic pyrolysis oil biodiesel blends with external PFI and vaporiser

ABSTRACT

Analysis of plastic oil obtained from waste plastic through pyrolysis process, as an alternative to biodiesel is presented in this paper. The HCCI engine is considered for experimental validation of combustion performance and emission characteristics. To accumulate pyrolysis oil as fuel, the design modifications were made in external mixture formation on the existing computerised 4-stroke, single cylinder, water cooled, direct injection kirloskar diesel engine connected with eddy current dynamometer to satisfy HCCI conditions. HCCI engine can be worked on wide assortment of fuels beginning from diesel to different blends (WPPO 5%,10%,15% and 20% by volume) of biodiesel .The designed additional device connected to the engine is utilised for fuel vaporisation and mixture arrangement. In the experimental study, the combustion results were initiate to be of 39.69 % higher Rate of Heat Release (RoHR) for biodiesel HCCI as compared with diesel HCCI. Higher brake thermal efficiency (BTE) was found 37 % without exhaust gas recirculation (EGR) at WPPO 20 % biodiesel blend. And also found 50 % and 65 % reduction in NOx emission and 18 % and 28 % reduction in smoke opacity are obtained for biodiesel vapour induction without EGR and biodiesel vapour induction with 15 % EGR as compared with diesel fuel. The CO (0.34 %), and UHC (2.15 %) emissions are increases with 15 % EGR, but the emissions are within the standard limits specified by the emissions standards.     

投入产出分析在可持续发展计划中的应用

如何在国民经济发展计划中体现资源环境因素的影响?如何用现实可行的方法制定出符合可持续发展要求的国民经济发展计划?是目前环境经济领域急待解决的问题。本文从物质平衡的角度,探讨可持续经济发展计划的研究方法。     

丹江口库区可持续发展能力分析

从区域可持续发展的角度出发,以湖北省丹江口库区为例,首先定性分析库区可持续发展的优势与问题,认为库区移民安置工作困难,库区可持续发展受到限制;经济增长缓慢,基础设施建设滞后;城镇化水平较低,库区社会矛盾突出;自然资源丰富与开发不足并存,库区淹没加剧土地资源稀缺;环境质量较好,生态基础脆弱。然后采用多因素综合评价模型定量分析了1999～2005年库区可持续发展的变化趋势。结果表明：库区可持续发展能力从1999年到2003年呈现明显的上升趋势,却从2004年开始缓慢下降;而人口、经济、社会、资源和环境各子系统也呈现出不同的特征。最后针对定性和定量评价结果提出相应的对策建议：做好库区移民安置,实现移民稳定就业;减少和消除移民贫困,增加基础设施建设;加快小城镇建设步伐,解决库区社会矛盾;发挥水资源优势,改善库区生态环境。     

基于灰色层次分析法的突发事件应急管理能力评价

突发事件的频发,使得对应急能力的评价备受关注。首先按照应急管理能力评价指标的选取原则,构建了突发事件应急管理能力评价指标体系。然后利用层次分析法确定各评价指标的权重系数,采用专家打分法建立评价指标集,运用灰色系统理论计算评分,进而建立了适用于突发事件应急管理能力的灰色层次分析评价模型。最后对某区域的突发事件应急管理能力进行实例分析,在定量计算的基础上,对其应急能力进行缺陷诊断,并提出措施建议,为完善应急能力提供科学有效的依据。     

城市控规单元防灾能力评价的有向加权图模型研究

为从城市具体规划建设的视角进行防灾能力评价,找到城市空间与设施的防灾薄弱环节,提升城市的防灾减灾能力,首先,在深入分析城市抗灾-救灾理念的基础上,从抗灾能力和救灾能力2个方面,建立适用于控制性详细规划层面的防灾能力评价指标体系;其次,基于防灾能力评价指标体系构建城市防灾有向加权图模型,通过PageRank算法对用地单元防灾能力值进行排序,实现防灾减灾能力的定量评价;最后,通过某市规划实例检验评价模型,针对控规单元的防灾问题提出规划提升措施。研究结果表明：所构建模型能够实现对各控规单元的防灾能力等级评价,反映城市控规单元防灾能力的分布情况,发现用地单元规划建设中的防灾减灾问题。     

Predicting Sustained Fire Spread in Tasmanian Native Grasslands

Fire is widely used in conservation management of native grasslands. Burning is often carried out under conditions that are marginal for sustained fire spread, and therefore it would be useful to be able to predict fire sustainability. There is currently no model allowing such prediction in temperate grasslands. This study aims to identify the environmental variables that determine whether fires will sustain in native grasslands in Tasmania, Australia, and develop a model for predicting fire sustainability in this vegetation. Fuel characteristics and weather conditions were recorded for 111 test fires. Logistic regression modeling identified dead fuel moisture content, fuel load, and percentage dead fuel as predictors of fire sustainability. Classification tree modeling identified dead fuel moisture and fuel load threshold values for sustaining fires. There was also evidence indicating a percentage dead fuel threshold. The logistic regression model and a model combining the results of the classification tree and the percentage dead fuel threshold accurately predicted the outcomes of a small set of experimental fires. These models are likely to have utility in predicting fire sustainability in Tasmanian grasslands and are also likely to be applicable to similar grasslands elsewhere.