Simulation of methanol steam reforming in micro channel with lattice Boltzmann method

Lattice Boltzmann method is used to simulate the methanol steam reforming process in a micro channel. Lattice evolution model with dual rate kinetic parallel reaction mechanism is established. The impacts of boundary temperature, inlet velocity on reaction outlet parameters, such as methanol conversion rate, outlet concentrations of hydrogen and carbon monoxide and maximum temperature difference, are studied. It is found that under a certain boundary temperature and inlet velocity, when the methanol molar ratio, boundary temperature and inlet velocity are 1.3, 523 K and 0.1 m/s respectively, the methanol conversion ratio can reach the highest value of 94.36%, together with the concentrations of hydrogen and carbon monoxide of 0.098 9 and 0.009 5% respectively. With the increase of boundary temperature and decrease of inlet velocity, the concentration of CO will increase.     

Investigation on the reaction characteristics of methane catalytic partial oxidation in a micro-channel

The reaction characteristics of fuel-lean CH4 catalytic partial oxidation over Rh are investigated numerically in a micro-channel, by using detailed elementary mechanism, focusing on the effects of inlet temperature, equivalence ratio of CH4/O2 and added H2O on catalytic partial oxidation of CH4. The results show that over Rh surface reaction of CH4 is kinetically controlled, while that of O2 is controlled by mass transport. Duo to the high reactivity of O2, CH4 is firstly oxidized and both complete and partial oxidation products are generated. After O2 is consumed, steam reforming begins, however, CO2 reforming does not appear. Increase of the equivalence ratio of C/O leads to increase of carbon deposition at reforming zoon, as thus both conversion of CH4 and production of syngas decrease, even the reforming process is stopped. The added H2O could dramatically inhibit carbon deposition, and promote the formation of H2 and CO2.     

乳酸甲酯反应精馏水解工艺的研究

酯化水解法是乳酸精制的有效方法。采用床催化—反应精馏工艺水解乳酸甲酯,研究了进料速度、再沸器加热功率、进料温度、回流比、水酯比对水解过程的影响。实验结果表明,床催化—反应精馏工艺可以彻底水解乳酸甲酯,低进料速度、较小的回流比有利于乳酸甲酯的水解,再沸器功率、进料温度、水酯比在所研究范围内,对水解率没有影响,保持在100%。本研究为乳酸甲酯反应精馏水解工艺的工业化应用提供了一定的实验基础。。     

The Influence of Air Inlet on Ventilation Effect in Indoor SubstationTransformer Rooms

Ventilation design is the difficulty of transformer room design. Temperature field and velocity field in a transformer room was simulated by CFD method . By comparing simulation value with the experimental value in related document , the effectiveness of the mathematical model was verified. Based on it, an indoor substation transformer built was taken as the simulation object, then designed and simulated six kinds of ventilation condition by changing the location and area of air inlet, focused on the influence of air inlet on the ventilation effect by comparing the temperature field ,velocity field and temperature characteristic value in different condition. The simulation results show that when air inlet area is fixed, the air inlet should be arranged in the radiator side and its center height should be controlled in the radiator center height or slightly offset position, it should not be higher than the radiator. When the air inlet location is fixed, air inlet area should be increased along the high direction to improve ventilation effect. The conclusions can provide technical support for the ventilation design of transformer room.     

地铁用间接蒸发冷却器换热性能影响因素

为解决地铁站冷却塔设置难题,提出了一种采用低速电机驱动旋转布水装置的间接蒸发冷却器,在两种布置方式下,对其换热性能进行了单因素实验,并运用正交实验法对较优布置方式下影响换热器换热的因素进行了分析。结果表明：两种布置方式下,喷嘴与蒸发冷却器的间距、两组换热管束间距均存在最佳值,喷嘴双侧旋转布水优于单侧旋转布水;换热器平行气流布置且喷嘴双侧旋转布水为较优布置方式,此时,换热器换热量随喷水量、转速、空气速度、冷却水进口温度的增加以及喷水温度、空气温度的降低而增大,其中,冷却水进口温度对换热器换热影响最为显著,其他因素对其换热的影响从主到次顺序为：喷水量、空气温度、空气速度、喷水温度、转速、冷却水流量。     

菜籽油制备生物柴油共溶剂的选择

生物柴油作为燃油替代品可以从食用油中大量获得,从而解决将来石油匮乏问题。针对菜籽油制备生物柴油酯的交换反应中,甲醇与菜籽油呈两相不互溶的主要问题,研究了添加共溶剂,使反应体系均相来提高反应速率与效率。以所选溶剂与甲醇的混合液为溶剂,菜籽油作溶质,分别在常温和60℃下做三元溶解度试验,选出乙醇、乙醚、四氢呋喃、1,2-环氧丙烷进行下一步比较;以普通菜籽油为原料,以甲醇为酰基受体,在加入不同共溶剂的条件下,进行碱催化酯交换反应,以酯化率和反应时间为考察指标,对共溶剂进行优选,发现以乙醇为共溶剂时,酯化率比空白提高了21.0%,且高于其他溶剂。研究结果表明,甲醇与乙醇的最佳摩尔比为3∶1。     

Study on Optimum Design of Rectangular Sedimentation Tanks

In this paper,the flow velocity fields,suspended solids concentration fields and flow-through curves in rectangular sedimentation tanks with different reaction baffles location,inlet horizontal velocity and length height ratio are simulated in detail using a developed mathematical model given in Reference 2.According to the numerical results,the influence of different reaction baffles location,inlet horizontal velocity and length height ratio on the operating efficiency is analyzed.Finally,the rational reaction baffles location,inlet horizontal velocity and length height ratio are presented.     

Numerical simulation of gas solid characteristics in double inlet square cyclone separator

This paper uses RSM turbulence model to conduct the numerical simulation on the gas flow field in double inlet square separator and calculate the velocity field and pressure distribution in the seperator. At the same time, it simulates the solid particle trajectories in the separators using Lagrangian model. The results show that the velocity field and pressure distribution in double inlet square separator have good symmetry, but the flow swirl intensity is insufficient and easy to decay; different sizes and different injection locations bring significant differences for the particle trajectories; injecting small particles can be easy to form flow short-circuit phenomenon inside the separator, injecting particles near the top of separator can be easy to form top ash ring phenomenon inside the separator; these phenomena have adverse factors to the separation efficiency. When the separation cylinder corners of square separator are changed into cutting-shaped chamfers, the flow field in the separator can be improved, and the separation efficiency of separator can be effectively improved.     

Modeling and Performance Analysis of Unglazed Solar Collector/Regenerator

An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.     

Numerical Simulation of Natural Ventilation and Thermal Environment in Industrial Plant with Heat Source

Numerical simulation of typical industrial plant was conducted by computational fluid dynamics (CFD) method. The influences of distances between fresh air inlet and ground on thermal environment and distribution of pollutant concentration in working zone were discussed when the heat source intensity and pollutant source were fixed. The main features of industrial plant with heat source were analyzed. The air velocity in working zone and the radiation between the wall surfaces should be considered for comprehensive evaluation of the thermal environment of industrial plant. Heat stress index, HSI, was introduced as thermal index to evaluate the thermal environment. Results showed that lifted fresh air inlet was not only helpful to increase the ventilation rate and the air velocity which improve the thermal environment in working zone, but also to decrease the mean pollutant emission concentration in the plant. When the distances between fresh air inlet and ground increased, the ventilation rate and the air velocity in working zone increased and the HIS and pollutant concentration decreased. When the distances between fresh air inlet and ground exceeded 1.2 m, the ventilation rate and the air velocity in working zone tended to be constant.     

响应面法优化槟榔中多酚提取工艺条件的研究

采用响应曲面法,建立了温度,甲醇浓度,料液比,对槟榔多酚提取率影响的二次多项回归模型。验证了模型的有效性。响应曲面分析表明,随着温度和甲醇浓度的增加,槟榔多酚提取率呈先上升,后下降趋势,随着温度和料液比的增加槟榔多酚提取率逐渐增加。随着甲醇浓度和料液比的增加,槟榔多酚提取率也是呈先上升后下降的趋势,但二者交互作用不显著,提取温度是影响多酚提取率的主要因素,其次为料液比和甲醇浓度。综合优化得出提取温度为65.7℃,甲醇浓度为62%,料液比为1：23.5g/mL,此时槟榔多酚提取率为11.23mg/g.     

运行参数对微型内燃机微燃烧特性影响机理分析

微型内燃机微燃烧过程对当量比和转速变化非常敏感,采用层流有限速率模型和甲醇氧化反应机理对其预混层流微燃烧过程开展仿真研究,探讨当量比和转速对微燃烧特性的影响规律及临界运行参数。在此基础上,提出采用热着火理论和化学反应动力学理论探索当量比对微燃烧特性的影响机理。结果表明仿真与实验比较吻合。当量比从0.6增加到1.1时,燃烧速率增加,压力和温度增加,压力最高值增加约1.5E+6 Pa,温度最大值增加约1 300 K,此后随当量比增加,燃烧速率减小,压力和温度减小。研究还进一步揭示了当量比影响微燃烧特性的机理: 稀燃区当量比主要通过温度变化来影响微燃烧特性,随当量比增加,燃料浓度增加,燃烧释放的总热量增加,所以温度和压力增加,燃烧速率增加;浓燃区当量比主要通过氧气量变化来影响微燃烧特性,当量比越大,氧气量越不足,基元反应速率越小,所以燃烧速率越小,温度和压力越低。转速越高,燃烧时间越短,燃烧越不充分,所以温度、压力越低。受微燃烧相对热损大、驻留时间短的特征影响,微型发动机实现完全燃烧的运行区域较窄,其实现完全燃烧的稀燃极限约0.9,最高转速约6 000 r/min。这在设计微型内燃机时值得关注。     

利用大豆油制备生物柴油的技术研究

研究了大豆油在碱催化剂(KOH)的作用下与甲醇发生转脂化反应,制备生物柴油的工艺条件,并采用气相色谱法,测定了生物柴油中脂肪酸甲酯的成分及含量。探讨了醇油摩尔比、催化剂用量、反应温度和反应时间等工艺条件对生物柴油得率的影响。正交实验结果表明,最佳反应条件为:反应温度50℃,醇油摩尔比为6∶1,催化剂添加量为1.3%,反应时间为40min,在此反应条件下,生物柴油得率高达92%。     

太阳能制冷机组通风系统中粮库温度的系统分析

针对不同的粮库内部太阳能制冷机组空调分布形式,利用CFD计算软件,采用标准k-e模型对粮库内部的大空间气流组织的非稳定特性进行三维数值模拟,分别比较了集中辐射式分布和沿四壁周向式分布两种形式的粮食表面附近的截平面的速度和温度分布,模拟结果显示:采用集中辐射式分布的模型流场扰动范围大,换热效果好,温度场分布均匀,整体降温效果好.由此可以看出流体计算技术在研究空调换热空间速度场和温度场分布的巨大作用,为空调的设计运行参数提供了重要依据,从而可以选用换热效果更好的空调分布形式.     

马齿苋总黄酮的超声波辅助提取工艺优化及其抗氧化、抗肿瘤活性研究

优化马齿苋中总黄酮的甲醇浸提-超声波辅助提取最佳工艺,并评价其体外抗氧化、抗肿瘤活性。以甲醇浓度、提取温度、料液比和超声功率为因素,以总黄酮提取率为指标,通过单因素试验与正交设计优选马齿苋总黄酮的超声波辅助提取条件;测定其对DPPH?和?OH的清除能力评价抗氧化活性;MTT法测定其对人肺癌细胞A549体外增殖的影响。结果表明：马齿苋总黄酮的最佳提取工艺为：料液比1:50,温度80℃,超声功率200 W,甲醇浓度90%,提取30 min,提取2次,总黄酮提取率为6.37%。马齿苋总黄酮对DPPH?清除率在4.0 mg/mL为89.80%,对?OH清除率在20.0 mg/mL为86.07%;其质量浓度为420 μg/mL时对细胞A549增殖的抑制率为74.62%,与阳性药组无显著性差异。该优化工艺准确可靠,提取率高;马齿苋总黄酮具有较强的抗氧化和抗肿瘤活性。     

基于升尺度方法的华北冬小麦区域生长模型初步研究 Ⅰ.潜在生产水平

作物生长模型是在田间尺度上开发的,而区域尺度上的作物生长信息更受决策部门的关注。作物模拟从单点研究发展到区域应用需要解决升尺度连接（Scaling-up）等一系列技术问题。本文利用以经纬度为权重的IDW空间插值法对气象数据和与温度有关的作物参数进行空间插值;根据华北冬小麦的品种地带性分布特点进行了冬小麦品种参数     

冬小麦产量形成模拟模型研究

根据小麦生理生态学理论，建立了冬小麦产量形成及最终产量模拟模型（WYSM），作为小麦生长模型的子模型。模型较为全面地考虑了孕穗期水分、低温霜冻、高温及生长后期干热风对冬小麦粒数的影响，将灌浆期分成3个阶段，引入3个品种参数，考虑每个阶段最大灌浆速率，并利用温度、水分、籽粒体内N/C比等因子进行修正，考虑源库限制，最后采用产量构成因素方法建立小麦最终产量模型。利用北京地区和河南地区不同年份和不同品种的试验资料对模型进行了验证。结果表明，WYSM模型对小麦产量构成因子及最终产量的模拟效果很好，模拟值与实测值吻合度高，粒数、粒重、产量及灌浆过程模拟的相对均方差（NRMSE）为4.2%～10.9%，相对误差（RE）绝对值的平均值为2.9%～6.7%，决定系数R2为0.88～0.99，说明模型不仅具有较强的机理性而且具有较高的预测性和适用性。     

无公害黑加仑原汁加工关键技术研究

利用无公害黑加仑果实,采取复合酶解法(果胶酶与纤维素酶的质量比为7∶3)A4B1C3D4E2处理,实际生产验证其出汁率达87.0%。采用磨间狭腔为0.050～0.075mm的胶体磨进行20min均质,能提高果汁的稳定性。采用0.20um微孔膜过滤器,过滤压力0.2～0.3MPa,可以满足常规生产要求。高温瞬时灭菌机灭菌适宜条件为进口温度18℃,杀菌温度121℃,杀菌时间5s,蒸汽进口温度142℃,冷却水进口温度15℃。适温的热处理对黑加仑果汁稳定性作用明显,而冷处理对黑加仑果汁稳定性的作用不明显,先冷处理后热处理的交替方法对黑加仑果汁稳定性作用也较明显。离子交换纤维处理后的黑加仑果汁,透明度稳定,不产生沉淀物,无褐变、变质现象,达到真正的无公害生产加工。     

A Simplified Method to Calculate the Wet Bulb Globe Temperature

The wet bulb globe temperature (WBGT) is difficult to measure and calculate in field observation and numerical simulation. To solve this problem, the air dry bulb temperature, wet bulb temperature, globe temperature, relative humidity, mean air velocity, solar radiation and wet bulb globe temperature in Guangzhou, P. R. China, first were collected during the summer (July). Next, correlation and regression analyses were used to derive a simplified model for calculating WBGT. The results show that dry bulb temperature, relative humidity, solar radiation, mean air velocity and WBGT were interrelated to some extent. These four parameters with high linear correlation can be used to predict WBGT in a simplified model with high precision. The simplified WBGT model can be used in field observation and simulation research regarding urban thermal environments.     

发动机用平板型空滤器流动阻力特性分析和改进

为减小平板型空滤器流动阻力以增大进气量,对平板型空滤器流动阻力特性开展了实验研究,获得了空滤器流动阻力随流量变化的规律和阻力构成成分。阻力随流量的增大而加速增大,滤芯阻力约占整个空滤器阻力的一半,入口流量为120 m 3/h时,总阻力为915.3 Pa,滤芯阻力为426.4 Pa。在实验获得滤芯阻力参数的基础上,提出采用多孔介质跃升模型对平板型空滤器内部流场开展三维数值仿真分析,结果表明,仿真结果与实验结果比较吻合,最大误差为5.67%。滤芯阻力同样约占整个阻力的一半,另一半阻力主要为出口处阻力,其余壁面阻力约占15%。最后,在实验和仿真分析的基础上,提出了改进模型并进行了仿真分析。结果表明,改进模型阻力有较大程度的下降,入口流量为120 m 3/h时,总阻力为588.2 Pa,较原始模型下降了32.2%;增大空滤器流通横截面积是减小阻力以增大进气量的有效手段,改进空滤器壁面的平滑性是补充措施。