车载高压氢瓶火烧试验及不同充装介质数值比较研究

目前我国尚无车载氢瓶火烧试验标准.当气瓶充装介质为氢气进行火烧试验时,因氢气易燃易爆的特殊性而使得试验具有巨大的危险.今通过火烧试验,得到了过程中氢瓶温度以及压力变化数据,以此为基础建立了燃烧场数值仿真模型,用于模拟气瓶内部充装介质分别为氢气和空气时温度和压力的变化.模拟与试验结果比较表明:所建模型能较为准确地预测气瓶内部温度、压力的变化规律,压升过程中空气与氢气的变化规律基本类似,可为确定车载氢燃料气瓶的火烧试验方法以及控制参数提供技术支撑.     

带涡流管的新型加氢流程数值研究

加氢站对车载高压气瓶充注之前,需先对高压氢进行预冷,以防加氢过程的气体升温带来的车载气瓶的结构性损伤。提出了一种基于涡流管预冷的新型加氢流程,该流程采用涡流管取代了传统的预冷装置。并采用计算流体力学的方法对加氢流程中的关键部件涡流管开展了数值计算。计算结果表明,高压加氢流程工况下的涡流管同样具有能量分离效应。且随着加氢过程的进行,涡流管出口背压提高,能量分离效应减弱,即冷端降温减缓。该过程恰好与气瓶充气增压过程升温减缓相吻合。数值计算结果初步证明了该流程的可行性。     

长管拖车用大容积环缠绕复合材料气瓶充气及冷却过程温度变化的数值模拟研究

建立了压缩天然气车(CNGV)用大容积环缠绕复合材料气瓶的充气温升数值模型,通过计算流体力学软件Fluent17.1进行数值仿真,模拟1800 s充满20 MPa、2500 L的CNG气瓶的填充过程以及5400s的静态冷却过程。详细介绍了该有限元模型的设置过程,重点分析了气瓶内气体流向、温度分布,以及充气及冷却过程的壁面温度状况,模拟结果表明,大容积气瓶的高温区域集中在瓶尾,该工况下的充气不会使气瓶壁面温度超过许用温度。     

充装量及筒体长度对车载LNG气瓶共振频率影响的数值模拟分析

以大容积车载液化天然气(LNG)气瓶为研究对象,分析不同充装量和不同筒体长度下的各阶共振频率随这两个参数变化的规律。当筒体长度不变时,随着充装量的增加,气瓶共振频率逐渐减小,按照标准最大允许充装率90%时,气瓶一阶共振频率已减小到国标允许的40 Hz以下,使用时容易引起气瓶内胆轴向窜动引发失效。当充装率90%保持不变时,随着筒体长度的增加,气瓶共振频率也呈现减小的趋势,当筒体长度为原长的0.8倍时,气瓶共振频率便低于40 Hz,而且随着长度增加将进一步降低,产生共振可能性加大,不满足国家对车载气瓶共振频率的要求。上述研究说明,评价气瓶抗振性能时应考虑内部介质充装率的影响,建议采用最大充装率为90%的气瓶作为判定该类型气瓶共振频率是否达标的条件。另一方面,当采用增加筒体长度扩大盛液容积时要注意共振频率随筒体长度降低的问题,避免结构振动破坏。     

Dynamic modeling of the mold filling process in an injection molding machine

This paper presents the development of a nonlinear mathematical model for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non-Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile-butadiene-styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system.     

高浓度CO变换催化剂装填量的动力学计算及问题探讨

应用动力学模型,结合工业生产数据,讨论了高浓度CO气体组成中一段催化剂的装填精度问题。分析了活性系数对催化剂装填量的影响,以年产15万t甲醇的德国GSP粉煤气化工艺为例进行了动力学模拟计算。结果表明:经过工业数据校正的动力学方程可以满足催化剂装填量计算的精度;采用分段进气或废锅副产蒸汽、分段变换制取甲醇等方法,可使反应深度和床层热点温度控制在要求范围以内。     

两阶段煤炭地下气化温度场模型

引　言煤炭地下气化过程实际上是一个自热平衡过程 ,依靠煤燃烧产生的热量使地下气化炉内建立起理想的温度场 ,进而发生还原反应和分解反应 ,产出煤气 .因此 ,在地下气化过程中起关键作用的是炉内的温度场 ,尤其对于两阶段地下气化更是如此 .两阶段气化是一种循环供给空气和水蒸气的地下气化方法 ,每个循环由两个阶段组成 :第 1阶段为鼓空气燃烧蓄热 ,生产空气煤气 ;第 2阶段为鼓水蒸气生产地下水煤气 .只有在第 1阶段积蓄了足够量的热能以后 ,才能使第 2阶段水蒸气的分解反应得以顺利进行 ,从而产生高热值地下水煤气 ,同时煤层热分解的程度…     

低变钴钼系新旧催化剂两段混装工艺优化方案

简述了优化钴钼系新旧催化剂混装工艺的必要性;从测温点配置、硫化副线设置、分离器设置等方面优化了新旧催化剂混装时的升温硫化流程;从温度控制、二硫化碳氢含量控制、循环煤气中氢含量控制等方面阐述了两段混装催化剂硫化过程的控制要点;针对不同的低变工艺流程以及操作温度、运行汽气比、预防催化剂失活等因素,提出了中低低变换工艺时两段新旧催化剂的混装方式。     

车辆冷却系统腐蚀及常见影响因素分析

发动机是将某一种形式的能量转化为机械能的机器,是车辆动力的来源。程简单来说,就是通过燃烧气缸内的燃料,产生动能以推动活塞在气缸内做上下往复运动,进而带动曲柄旋转使车辆行驶。当发动机处于正常工作状态时,气缸内的气体高达2000℃。高温气体会使气缸内壁、活塞及缸盖等过热,导致发动机性能降低,甚至使发动机损坏。为了避免燃烧室周围的零部件过热,减少因零部件过热对发动机造成的不良影响,发动机设置有冷却系统。     

在方箱炉、圆筒炉中区域法计算辐射传热的数学模型及其应用

本文叙述了以区域法计算辐射传热的数学模型。在区域法中,系统被分为表面区和气体区,区域数取决于所要求的结果精度和计算时间。炉子的温度分布可通过解每区的能量平衡而得。作为Hottel和Cohen的原始开发,直接交换面积限于立方体和正方形;本文给出了在方箱炉、圆筒炉中任何两区之间直接交换面积方程式的推导。这些方程式可适用于任何大小的矩形、共轴圆筒壁、炉底环形区和其他形状。 本文提供了一个关于烃类一段蒸汽转化炉和圆筒炉的设计方法。计及反应动力学、对流传热、管内压降,采用区域法计算这些炉子的温度分布,从而预言工艺气、烟气、管表面和耐火墙表面的温度分布。计算结果与工厂实测数据相吻合。     

复合材料高压储氢气瓶快速充放氢过程中的温度效应研究

氢能的利用离不开氢的储运这个关键环节,高压储运是目前氢气储运的主要方式。高压快速充放氢会发生温度快速升高和降低问题,从而影响储运设备的使用寿命。主要研究了车载复合材料高压气瓶在快速充放氢过程中的温度效应,并对温升后的充氢量进行了计算。为了确保复合材料气瓶的温升在100℃以下,经过大量试验确定了温升不超过复合材料气瓶允许温度的快速充氢方式。     

Polymer powders mixing part I: Mixing characterization in rotating cylinders

In the production of rotomolded parts, the distribution of particle sizes in the form of polymer powder is highly important to produce parts of good quality. In the case of polymer blends, the particle size distribution becomes even more important to assure that good mixing occurs before the polymer melts. In this work, the mixing of free flowing polymer powders in a horizontal rotating cylinder has been studied. Special attention is given to the initial moments of mixing and the transition from a standstill to a fully developed rolling regime. The parameters studied include Froude number (rotational speed), cylinder loading, relative powder composition and particle sizes. For the first time, mixing dynamics are quantified using two image analyzes: grey-level co-occurrence matrix (GLCM) and Threshold methods. Using the experimental data, a model is proposed to follow the mixing dynamics and to determine the equilibrium time. The results also indicate that the Froude number is not enough to characterize the flow regime and the filling ratio must be accounted for.     

Real‐time diagnosis of gas‐assisted hot embossing process by ultrasound

An integrated high temperature ultrasonic transducer (HTUT) sensor has been utilized for diagnosis of gas‐assisted hot embossing process to fabricate V‐cut patterns real‐time, nonintrusively and nondestructively. The progression of the process, including plastic plate soften, gas introducing, cooling, and plate detachment inside the chamber, was clearly observed using ultrasound. Ultrasonic velocity could not only indicate the four steps of process, but also evaluate the replicating degree of the V‐cut patterns on surface of plastic plate under various temperature and gas pressure settings. The experimental results indicate that the heights of V‐cut patterns increase with temperature and gas pressure. POLYM. ENG. SCI., 53:2175–2182, 2013. ©2013 Society of Plastics Engineers     

On-Board Hydrogen Generation for Fuel Cell-Powered Vehicles: The Use of Methanol and Propane

Although hydrogen has been found to be the most acceptable fuel for vehicle-mounted fuel cells, the storage and transportation of the gas presents difficulties. As a result, attention has been focused on on-board conversion of more readily available fuels such as methanol. Comparisons have been made of hydrogen generation from methanol and propane. Simulations are based both on thermodynamic and kinetic data. The results show that a mixture of oxidation and steam reforming (indirect partial oxidation) produces more hydrogen than direct partial oxidation. Propane is found to produce more hydrogen per weight carried than methanol, but suffers from the disadvantage that reaction does not start at room temperature. The necessity to fuel a vehicle with an organic fuel and with water is demonstrated.     

Explosion risks during the confined storage of bituminous coals : Calculation of gaseous hydrogen accumulation in ship holds

Bituminous coal piles stored in the open air can undergo autocatalytic heating accompanied by the emission of small but appreciable amounts of molecular hydrogen. When the coal is contained in a confined space and the temperature reaches 40°C, accumulation of hydrogen is expected. This process has been observed for a wide variety of bituminous coals. The amount of hydrogen gas expected to accumulate in the air pocket above the coal cargo in ship holds (assuming that the coal's temperature approaches 40°C during the voyage) has been calculated. The results clearly indicate that in most cases the hydrogen concentration will be appreciably above the lower explosion limit in air. Hence when bituminous coals are stored in a confined space (e.g. a ship hold), the explosive risk of hydrogen should be taken into account.     

单开口脉冲管内真实气体的流动

The real gas effect is dominant at high pressure and low temperature, and it is modeled by complex equations of state other than perfect gas law. In the vicinity of liquid-vapor critical point, the real gas exhibits unusual gas dynamic behavior. In the present work, a transient wave fields in unilateral opening pulse tube is simulated by solving the Navier-Stokes equations incorporated with the Peng-Robinson thermodynamic model. The computational fluid dynamics (CFD) results show a remarkable deviation between perfect gas model and real gas model for contact interface and shockwave. The wave diagram based on the real gas model can help to solve the problem of offset design point.     

液氢缩比贮箱蒸发特性数值模拟及实验验证

地面缩比贮箱用来模拟箭载液氢贮箱热物理过程及运行特性，包括筒段和壳段，壳段用于支撑筒段。筒段和部分壳段使用泡沫绝热，壳段结构部分裸露在环境中，成为液氢贮箱的主要漏热源。基于计算流体力学方法数值研究了液氢缩比贮箱蒸发特性，构建了基于VOF两相流模型以及Level-set界面跟踪方法的贮箱两相氢流动和相变传热传质数学框架，其中气液界面传质率基于Lee模型计算。框架中的系数、边界条件等作如下考虑：Lee模型中的液化/蒸发系数通过与实验数据对比获得；通过理论分析低温面有/无泡沫保温层的结冰特性，对暴露在环境的泡沫和铝壳表面施加对流换热或常热流边界条件；当贮箱压力达到约2个大气压(0.2 MPa)时，安全阀打开放气保持内部压力不变，基于自定义函数方法模拟阀门开闭实现控制贮箱压力的目的。与实验测量的液位下降速率和气相温度非稳态变化对比表明，构建的数值模型能够较好地模拟液氢贮箱自增压过程的复杂流动、相变传热传质特性。为模拟真实箭载液氢贮箱停放阶段的热物理过程打下基础。     

MODELLING A COMPARTMENTED FLUIDISED BED COAL GASIFIER PROCESS USING ASPEN PLUS

A process model based on the ASPEN PLUS process simulator has been developed for a novel Compartmented Fluidised Bed Coal Gasifier (CFBCG) process. A distinctive feature of the model is that a number of user-written models have been incorporated within the ASPEN frame to describe processes of hydrodynamics, coal combustion and gasification, solid circulation, entrainment and elutriation, and particle size distribution in the CFBCG and energy loss to the environment from the reactor. In general, most of the predictions of the model is in a reasonable agreement with the experimental results. However, some unmeasurable operating parameters at hot state in the experiments lead to some difficulties to verify the model in these instances against real data. Uncertainty related to volatile combustion mechanisms in fluidised beds in the literature also influences the model accuracy. Nevertheless the ASPEN based model provides a convenient vehicle for the further development of this new process, by allowing the physical insights into mechanisms, which would be difficult and expensive to investigate experimentally. The simulations indicate that the CFBCG concept is sound and further development is needed to improve the opera tibility of the process before practical implementation to produce high quality synthesis gas from the CFBCG might be considered     

氢气快充温升控制装置数值设计

高压氢气从储氢罐到氢气瓶的加注过程中存在一定的温升．从安全角度出发,本文建立了高压氢气快充温升控制设计模型,基于模型对氢气快充温升控制装置进行了数值分析,并提出了氢气快充温升控制装置的数值设计方法。研究结果可以为加氢站等对于初始温度有要求场合的设计提供参考。     

A 3‐D finite element model for gas‐assisted injection molding: Simulations and experiments

To gain a better understanding of the gas‐assisted injection molding process, we have developed a computational model for the gas assisted injection molding (GAIM) process. This model has been set up to deal with (non‐isothermal) three‐dimensional flow, in order to correctly predict the gas distribution in GAIM products. It employs a pseudo‐concentration method, in which the governing equations are solved on a fixed grid that covers the entire mold. Both the air downstream of the polymer front and the gas are represented by a fictitious fluid that does not contributeto the pressure drop in the mold. The model has been validated against both isothermal and non‐isothermal gas injected experiments. In contrast to other models that have been reported in the literature, our model yields the gas penetration from the actual process physics (not from a presupposed gas distribution). Consequently, it is able to deal with the 3‐D character of the process, as well as with primary (end of gas filling) and secondary (end of packing) gas penetration, including temperature effects and generalized Newtonian viscosity behavior.