抽采瓦斯过程中煤层温度演化规律的物理模拟试验研究

 煤层瓦斯作为一种非常规天然气,对其进行开发利用具有一举多得的功效,越来越受到各国重视。为了研究煤层瓦斯解吸过程中煤层温度的演化规律,利用自主研发的多场耦合煤层气开采物理模拟试验系统,开展了不同初始瓦斯压力和不同地应力水平下抽采瓦斯的物理模拟试验。研究结果表明：(1) 煤层瓦斯解吸吸热导致煤层温度下降,且温度和流量具有很好的相关性,都表现出在抽采初期下降较快,后期下降缓慢,其中温度随时间的下降量符合对数函数关系;(2) 距抽采钻孔越近,瓦斯解吸速度及温度下降越快、温度下降量越大,且垂直钻孔方向的温度梯度大于平行钻孔方向的温度梯度;(3) 初始瓦斯压力越大,瓦斯解吸速度及煤层温度下降越快、温度下降量越大,而地应力越大,瓦斯解吸速度及温度下降越慢、温度下降量越小,表明初始瓦斯压力对解吸过程中煤层温度的影响效果较地应力更加显著。     

温度对燃气热水器热效率测试与计算的影响

通过理论热效率的计算式,分析了试验室环境温度和燃气温度变化对燃气热水器热效率的影响,通过试验测试分析了进水口冷水温度的变化对燃气热水器热效率的影响,提出燃气热水器热效率测试与计算的最佳温度状态为试验室环境温度、燃气温度、进水口冷水温度三者相等。     

A least-squares support vector machine approach to predict temperature drop accompanying a given pressure drop for the natural gas production and processing systems

Precise estimation of temperature variations throughout gas production systems can enhance designing the production amenities. Routine methods for determining the temperature profiles in gas production systems are based on the gas composition and flash calculations. However, if the gas compositions are not available, the gas production system can be modelled by employing a black-oil approach, which is also a method for calculating the oil/gas resources and for modelling the gas reservoir operation. Accordingly, for black-oil models and when the natural gas compositions are not accessible, applying robust predictive tools in this research is of high interest in natural production systems. The current study places emphasis on applying the predictive model based on the least- squares support vector machine (LSSVM) to estimate precisely the proper temperature drop associated with a given pressure drop throughout the natural gas production systems based on the black-oil approach to acquire an accurate result for the temperature drop of natural gas streams. Genetic algorithm was used to optimise hyper-parameters (γ and σ²) which are embedded in the LSSVM model. Using this method is simple and it accurately determines the temperature drop through the natural gas stream with minimum uncertainty.     

基于气温变化的冬季城市燃气日负荷预测方法

结合实例分析了日平均气温对冬季城市燃气日负荷影响的规律,得到燃气日负荷的主要影响因素为气温所处温度区间、气温变化的幅度,而与气温所处时间区间和升降趋势无关。提出了基于气温变化的燃气日负荷预测方法——温差系数法,取得了较好的预测效果。     

气象因素对城市燃气日用气量的影响

气象是城市燃气日用气量的重要影响因素.本文以我国华北某城市为例,分析了温度、湿度、风速、云量等气象因子对城市燃气日用量的影响作用,通过相关分析和因子舍选,最终确定日平均温度、日平均相对湿度、日照时数为城市燃气日用气量的关键影响因素,该研究对于城市燃气用气规律分析和负荷预测工作具有指导意义.     

含瓦斯煤渗透率理论分析与试验研究

 从孔隙率的基本定义出发,充分考虑煤基质吸附瓦斯膨胀、热弹性膨胀、受瓦斯压力压缩对其本体变形的影响,首先给出煤体孔隙率与体积应变、温度及瓦斯压力之间的函数关系,再以Kozeny-Carman方程为桥梁,建立扩容前压缩条件下综合考虑有效应力、温度及瓦斯压力共同影响的渗透率动态演化模型。相关试验数据验证表明,所建立的渗透率理论模型具有良好的适用性,能反映出一定条件下的渗透率演化趋势。试验研究表明：煤体孔隙发育程度与渗透率具有较好的一致性,渗透率随孔隙发育程度的增高而增大;当温度和瓦斯压力一定时,渗透率随有效应力的增大而减小,并且瓦斯压力越低减小趋势越明显;有效应力和瓦斯压力一定时,渗透率随温度升高而减小,但其减小幅度基本不受有效应力变化的影响;温度和有效应力一定时,渗透率随瓦斯压力的升高呈先急剧减小而后逐渐平缓的趋势。含瓦斯煤渗透率与有效应力、温度和瓦斯压力之间关系的研究,为有温度场参与的多场耦合问题的研究提供理论基础,也为高温矿井瓦斯抽放率的提高提供技术支持。     

煤与瓦斯突出过程中温度变化的实验研究

从理论上分析了煤与瓦斯突出过程中温度的变化趋势,并在实验室对其进行了实验验证,认为在煤与瓦斯突出过程中,煤体温度的升高是由地应力破碎煤体使弹性能释放造成的,而温度降低则是由于瓦斯气体解吸和膨胀造成的。其变化是先升高后降低并连续变化的,根据煤体温度变化梯度可以进行瓦斯突出的预测预报。     

A simulation model for compartment fires

From the standpoint that the strict estimation of heat released in an enclosure is important to simulate enclosure fires, a new mathematical model involving the combustion efficiency, the temperature dependence of heat capacities, and the composition of burnt gas has been developed. The calculated results are in good agreement with a few experimental results for enclosure fires having different fuel areas and compartment sizes.     

Behaviour of Double Glazing in Corner Fires

The results of fifteen experiments in which a double glazing assembly was exposed to enclosure fires of increasing severity are presented. The glazing assembly was exposed to the typical two zone or one zone fire enclosure environment with consistency and repeatability within each set of three experiments conducted at each severity level, evident from the enclosure gas temperature profiles. The results presented include; enclosure local gas temperatures, local exposed glass surface temperatures, local shaded glass temperatures, total incident fluxes, convective and radiative fluxes, incident flux distributions at time of first cracking and inner and outer pane behaviours. A simple lumped model approach is developed to predict the response of the glazing to thermal insult. Total loss of glazing integrity is related graphically to the time of first crack.     

冷凝式燃气快速热水器排烟温度的探讨

根据冷凝式天然气快速热水器排烟温度与其热效率关系的理论分析,并通过试验得出冷凝式天然气快速热水器效率与其排烟温度的关系。试验结果表明冷凝式燃气快速热水器有很好的实用价值。     

Scale modeling of quasi-steady wood crib fires in enclosures

A scale modeling hypothesis for quasi-steady enclosure fires has been experimentally evaluated. The scheme utilizes geometric similarity and freeburn behavior of the source fuel to scale the source fuel element and the enclosure walls from one scale to another. The burning rate, gas and wall temperature rise, combustion product concentrations and radiative heat flux were measured in full, half and quarter-scale enclosures using wood cribs as the fuel. The good agreement of reduced data among different size enclosures strongly supported the modeling hypothesis. Relatively large scatters were observed with combustion product concentrations and radiative heat flux. In general, the scatters for the measured burning rate and gas and wall temperature rise in enclosure fires were within those observed in freeburn crib fires. The experimental results established that the modeling scheme can be used for predicting the burning rate and room environment in enclosure fires.     

Rise in structural steel temperatures during ISO 9705 room fires

An experimental programme was undertaken to study the temperature rise of protected and unprotected structural steel during a fire within a small enclosure (an ISO 9705 room). The fuel (wood crib) was placed at two locations (front and back) within the ISO room. Each location had two fire scenarios present: the first fire scenario was for recording the temperatures of protected steel members within the enclosure, and the second fire scenario was to measure the temperatures of the directly exposed members. Six steel columns and two steel beams were strategically placed, and their temperatures were measured. Other data recorded were gas temperatures and heat release rates (HRRs). Thermocouples were kept in identical locations during the tests with protected and unprotected steel members to facilitate direct comparison. Despite the natural variability in fire development in identical situations, data up to ≈20 min were found suitable for direct comparison between protected and unprotected steel members. Comparison of these results with Fire Dynamics Simulator (FDS) version 5.3.1 modelling (with prescribed HRRs) results is presented to show the usefulness of the data collected.     

城市燃气负荷的气温响应特性研究

气温是影响城市燃气短期负荷的重要因素之一。通过对华北某城市燃气负荷和气温历史数据的统计,分析了城市燃气居民、商业、工业、锅炉和空调等用户用气负荷受气温变化影响的特点,提出了燃气负荷气温响应特性分析的基本思路,讨论了典型的燃气日负荷气温响应特性。     

The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires

In order to detect a fire and provide adequate fire protection to a tunnel structure, the maximum gas temperature beneath the ceiling to which the structure is exposed needs to be estimated. Theoretical analysis of maximum gas temperature beneath a tunnel ceiling based on a plume theory is given. The heat release rate, longitudinal ventilation velocity and tunnel geometry are taken into account. Two series of model-scale experimental tests were also carried out. The results of both analysis and experiments show that the maximum excess gas temperature beneath the ceiling can be divided into two regions. When the dimensionless ventilation velocity is greater than 0.19, the maximum excess gas temperature beneath the tunnel ceiling increases linearly with the heat release rate and decreases linearly with the longitudinal ventilation velocity. When the dimensionless ventilation velocity is less than 0.19, the maximum excess gas temperature beneath the ceiling varies as the two-thirds power of the dimensionless heat release rate, independent of the longitudinal ventilation velocity. In both regions, the maximum excess gas temperature varies as the −5/3 power of the vertical distance between the fire source bottom and tunnel ceiling. The investigation presented here considers only the cases when the continuous flame region is lower than the ceiling height.     

封闭空间火灾中燃料烟尘对墙体所受热通量的影响

尽管在封闭空间内已经做过很多关于气体温度和燃烧率的研究,但目前仍然缺乏封闭空间内墙体上热通量及其分布方面的信息。该热通量数据是确定墙体材料特别是玻璃的热反应及性能的必要输入参数。试验用封闭空间墙体上的热通量是通过多块薄钢片(25.4mm×25.4mm×3mm)以及钢片周围隔热材料的温度推算出来的。另外,笔者还测量了热流计附近墙体的质量损失率和温度。试验用封闭空间是ISO标准墙脚火试验的1/3,有六个开口,燃料为甲醇、IMS(工业用甲基化酒精)以及甲苯,装在大小不同的三个方形油盘里,油盘放置在封闭空间的内外拐角处。在选择燃料方面,笔者的依据是燃料燃烧产生的烟尘应越来越浓。试验发现,与以前对地板的研究结果有所不同的是,墙体上的热通量不仅仅取决于烟气温度,还取决于热释放速率的强弱以及燃料所产生的烟尘的多少。另外,对甲醇、IMS以及甲苯所产生的热通量的比较发现,对流热可以与辐射热通量(热烟气流以及封闭墙体造成)以及来自烟羽流的辐射热通量分开。     

地层条件下凝析气藏的多相渗流特性

 在进行凝析气藏的数值模拟、试井分析以及开发动态预测的过程中,需要获取具有代表性的凝析油气、油水和气水相对渗透率曲线。深层高温高压凝析气藏在开采过程中地层流体渗流伴随着复杂的相变,因此,不能用传统的油气相渗曲线来代替实际地层条件下凝析油气相对渗透率的变化规律。在地层常规物性和流体特性分析的基础上,以实际凝析气藏的凝析油、气和地层水为实验流体,用实际凝析气藏的岩石作为多孔介质,在地层温度和压力条件下研究了多相渗流特征,得到了油气、油水和气水多相渗流的相渗曲线,表明地层条件下低孔低渗岩石的油水、油气和气水两相共渗能力较弱,而对于含裂缝或孔洞的高孔高渗岩石,油水、油气和气水两相共渗区较宽,驱替效率较高。这些成果为高温高压凝析气藏的动态模拟与预测提供重要的数据和相渗曲线。     

Comparison of thermal hazards of sodium dithionite and thiourea dioxide from thermal analysis (DSC-TG), small-scale self-heating experiments and FTIR smoke gas analysis

Sodium dithionite and thiourea dioxide are two typical reducing agents commonly used in industry. This paper compared the thermal hazards of sodium dithionite and thiourea dioxide based on DSC-TG (Differential Scanning Calorimetry and Thermogravimetry) thermal analysis, small-scale self-heating experiments and FTIR smoke gas analysis. From the thermal analysis (DSC-TG), sodium dithionite starts to lose crystal water at the temperature around 60 °C which makes the sodium dithionite very unstable at relatively lower temperature. The decomposition of sodium dithionite has a close correlation with oxygen while the decomposition of thiourea dioxide has little relationship with oxygen. Small-scale self-heating experiments were designed to reflect the self-heating and spontaneous combustion properties of the characteristic dimension 20 cm. The small-scale self-heating experiments show that there is a little gap between the Critical Ambient Temperature (CAT) of sodium dithionite and thiourea dioxide. From FTIR smoke gas analysis, the smoke of thiourea dioxide (decomposition or combustion) is far more dangerous than sodium dithionite. Although the risk of spontaneous combustion for sodium dithionite is higher than thiourea dioxide, the thermal hazards of thiourea dioxide are far higher than sodium dithionite as the decomposition and combustion of thiourea dioxide would release far more heat and dangerous smokes.     

Scale modeling of inert pressurant distribution

Pressurization with inert gas, typically nitrogen, has been proposed for fire suppression in pressurizable enclosures. Implementation requires assurance of sufficiently uniform presurant distribution. A convenient procedure for scale modeling pressurant distribution is described and applied to a 1/6-scale model of an uncluttered 5-m³ enclosure. Two inexpensive methods for determining local pressurant fraction history are indicated, temperature and continuous gas analysis.     

Physical scaling of water mist fire extinguishment in industrial machinery enclosures

Froude-based scaling relationships had previously been theoretically extended to, and experimentally validated in the laboratory for, water mist suppression of fires in open environment and in enclosures, which were shown applicable to gas, liquid and solid combustible fires. Before applying these relationships to real-world settings, their applicability needs to be further evaluated for the intended protection. This paper presents such an evaluation on scaling water mist fire extinguishment in an industrial machinery enclosure. In this evaluation exercise, a full-scale water mist protection set-up tested for a 260-m³ machinery enclosure was selected as the benchmark. A ½-scale machinery enclosure test replica was then constructed, together with a ½-scale nozzle whose orifices were geometrically similar to those of the full-scale nozzle. Spray measurements indicated that the ½-scale spray closely met the scaling requirements, in terms of discharge K-factor, water mist flux, droplet velocity and droplet size distribution. Two spray fires and one pool fire, which were scaled with the respective full-scale fires, were used to challenge the water mist protection in the ½-scale enclosure. At least five replicated tests were conducted for each of the four tested fire scenarios. Overall, the instantaneous local gas temperature and oxygen concentration measured inside the ½-scale enclosure for each fire scenario agreed reasonably well with those measured at the corresponding locations inside the full-scale enclosure, meeting Froude modeling's requirement that scalar quantities be preserved in different scales. The fire extinguishment times obtained from the ½-scale tests for each fire scenario were also statistically consistent with that observed in the corresponding full-scale test. Based on the obtained results, it is concluded that, for machinery enclosures and other similar occupancies, the previously laboratory-validated scaling relationships for water mist fire suppression can be used to determine the fire extinguishing performance of a full-scale water mist protection in a ½-scale test facility.     

三轴应力条件下温度对原煤渗流特性影响的实验研究

 利用自主研发的含瓦斯煤热流固耦合三轴伺服渗流装置,测定煤样在不同有效应力、不同瓦斯压力、不同温度条件下的渗透率,探讨不同有效应力和不同瓦斯压力条件下,煤样渗透率与温度的关系。在实验研究的基础上为消除试件个体差异的影响,客观地反映温度对渗透率影响程度的大小,定义温度敏感性系数,进而研究温度对渗透率的影响程度与温度的关系。研究结果表明：(1) 当有效应力和瓦斯压力保持恒定时,随着温度的升高,煤样渗透率会逐渐降低,温度敏感性系数逐渐降低,即温度越高,温度对渗透率的影响程度越小;(2) 在相同温度条件下,有效应力、瓦斯压力越大,温度敏感性系数越低,温度对渗透率的影响程度越小。