齿型自转塑料纽带清洗力矩强化实验研究

为了进一步提高自转塑料纽带的清洗能力 ,对齿型自转塑料纽带和普通自转螺旋纽带的清洗力矩进行了对比实验研究 ,结果表明 ,齿型自转塑料纽带的清洗力矩比普通塑料纽带的清洗力矩平均提高 4 2 %～ 70 %。其中齿片的安装角α、齿高和齿距等结构参数对清洗力矩、纽带自转速度及纽带运转平稳性都有影响。     

传热流体动力斜齿螺旋纽带自动清洗技术

现有的热流体动力塑料光滑纽带不能用于低流速传热设备的自动清洗,为此研制了一种强化自动清洗力矩的斜齿纽带。其原理是在纽带表面上以一定间距排列反对称斜齿,被导向的传热流体对纽带的不对称反作用力形成一个旋转力矩。与现有光滑无齿的自转纽带相比,斜齿型纽带自转清洗力矩增大了75.48%～101.57%,传热系数提高了一倍,具有广阔的应用前景。因此,这种新技术很适合用在0.4m/s以上的低流速传热设备中进行自动清洗保洁和传热强化。     

换热器内自转螺旋扭带除盐防垢研究

传热设备普遍存在不同程度的结垢而导致其传热效果下降,为实现传热管的自动清洗,进行了传热管内自转扰流元件在不同流速下的传热强化及除盐保洁技术的模拟试验研究。依据结晶动力学原理设计模拟试验方案,采用38mm×3mm×2000mm不锈钢管内通NH4Cl热饱和溶液,管外加碳钢套管通冷却水冷却,传热管内分别采用钢丝螺旋结构和塑料扭带进行试验。试验结果表明,在流体雷诺数Re不超过43000的情况下,同等试验条件时,钢丝螺旋结构和塑料扭带在达到平衡时的总传热系数分别比空管提高224%和273%,且塑料扭带除盐效果优于钢丝螺旋结构,可以实现长期连续生产。     

换热器自转清洗纽带自动阻垢技术的试验研究

为了考察内置自转清洗塑料螺旋纽带的除垢、防垢和清洗效果,以生产现场工业循环水换热器为研究对象,在相同条件下,对有、无自转清洗纽带的换热器污垢粘附速率和管壁腐蚀速率做了应用性对比试验研究。研究表明:自转清洗纽带的防垢、除垢、清洗效果显著,内置纽带管换热器与普通光管换热器相比,污垢粘附速率平均下降46%;塑料纽带对管壁的额外磨损微乎其微,可免除金属纽带对管壁的磨损问题。这些研究结果为自转纽带的推广应用提供了参考依据。     

混合式球罐球壳板尺寸的计算

为了简便,先说明下面公式中的符号意义Ｒ———球壳内半径,ｍｍ;Ｄ———球壳内直径,ｍｍ;α0———极带的半球心角,°;α1———第1带的球心角,°;α2———第2带的球心角,°;αｉ———第ｉ带的球心角,°;Ｎｉ———第ｉ带的分瓣数;θ1———极带中板的球心角,°;θ2———极带侧板的球心角,°;θ3———极带边板的球心角,°。1极带板尺寸计算极带分为7块的混合式球壳结构及坐标系(如图1)。则相应的各弧曲线方程为图1　混合式球罐极板的分瓣及坐标系1—Ｘ2 Ｙ2=Ｒ2　2—Ｘ-Ｙ=0　3—Ｘ Ｙ=0　4—Ｘ2 Ｙ2=Ｒ2ｓｉｎ2(θ1/2 θ2 θ3)5—Ｘ2…     

高压水射流PDC钻头结构参数数值模拟研究

以中硬细砂岩为岩石材料,应用动态有限元法对高压水射流PDC钻头参数做了数值模拟研究。得出如下结论:(1)高压射流入射角对不同岩层存在最优值,对于中硬地层细砂岩最优入射角为40°;(2)PDC钻头钻进中钻齿所受扭矩随作用半径增大成指数规律增长,在硬地层钻进钻齿前倾角为-15°时破岩效果最佳;(3)采用直径1.8mm的高压小喷嘴射流能显著改善PDC钻头钻齿受力,避免钻齿冲击破坏,延长钻头寿命;(4)高压水射流与机械齿联合破岩时,喷嘴与钻齿相对位置对破岩效果有显著影响,喷嘴处于钻头外锥时,可均化钻齿受力,提高破岩效率。     

双圆弧齿轮分度圆弦齿厚及测量齿高的计算

对于分度圆直径较大,不便采用公法线长度测量的齿轮,用测量分度圆处弦齿厚及测量齿高检测成品齿形是必要的。分度圆处弦齿厚及测量齿高的计算可用精确计算和近似计算两种方法。当螺旋角β=10～30°、齿数Ζ=10～30时,用近似法计算弦齿厚及测量齿高的最大误差为0.00001～0.001m_n,当齿数大于30时,误差更小,完全可以满足现场实际的需要。     

2种材质自旋扭带的转动与压降特性

换热管内置的自旋扭带由薄金属片或塑料片制成,为探明这2种材质扭带的转动和压降特性,选用铝和聚丙烯2种材质的自旋扭带为研究对象,对比分析结构参数和流量对这2种材质扭带转动和压降特性的影响规律。分析结果表明:2种材质扭带转速和压降随流速增大而增大;扭带的宽度和扭率越小,转速越高;扭带的宽度越大且扭率越小,则压降越大;在相同宽度和扭率条件下,聚丙烯扭带的起转流速低于铝制扭带。在相同流速及结构参数一致的条件下,铝制扭带转速高于聚丙烯扭带,而压降反之。根据试验数据拟合出内置铝制或聚丙烯扭带后换热管的压降增量和阻力系数关联式,其预测值与试验值对比的平均绝对误差分别为2.1%和2.3%。研究结果可为工程中扭带的选型提供参考。     

换热器管内自转螺旋自动清洗能力的试验研究

提出了换热器管内自转螺旋清洗能力的径向压力模型概念,自转螺旋清洗除盐能力的大小随旋转螺旋对管内壁的接触压力的增加而增大。通过对比试验得出,在立式装置中螺旋对管内壁的切削力几乎为0,在卧式装置中由于螺旋与盐液之间的密度差使得螺旋无法对中,其对管内壁的切削力增大,除垢效果明显,总的传热系数提高了113%,试验结果与理论分析一致。如增大螺旋与盐液的密度差则传热系数还可大幅提高。因此,为了进一步提高自转螺旋自动清洗及强化传热效果,可从螺旋扭带的偏心、偏重等方面着手。     

碳酸盐岩自转向酸酸岩反应动力学实验研究

酸岩反应动力学参数为正确分析酸岩反应速率规律、指导基质酸化/酸压施工设计提供了基础。利用旋转岩盘实验仪进行碳酸盐岩自转向酸酸岩反应动力学参数的测定,建立了酸岩反应动力学方程,并分析其影响因素。结果表明,自转向酸具有较低的反应速率及传质速率,其在80℃、500r/min、7.5MPa条件下,酸岩反应级数m=1.144,反应速率常数K=4.34×10-(7mol·L)-m·mol(/cm2·s),反应速率方程为J=4.34×10-7Ct1.144;其活化能Ea=34991J·mol-1,频率因子K0=6.53×10-2(mol·L)-m·mol(/cm2·s),酸岩反应动力学方程为J=6.53×10-2e-34991/RTC1.144;并通过转速～De及Re～De分析可知,影响H+有效传质系数的因素包括转速和酸液浓度。     

内插旋流片的缩放管内糖液自然对流的传热研究

The natural convection heat transfer of a 60% sucrose solution in a vertical converging-diverging tube （CD） withregularly-spaced twisted tapes （RSTT） has been investigated numerically and experimentally. The effects of wall temperatureand number of RSTT on the Nusselt number were studied in detail. The distributions of velocity and temperature inthe 60% sucrose solution were studied and the simulated results of CD with RSTT were compared with those of the smoothtube. The influence of Rayleigh number and RSTT on the Nusselt number was conducted experimentally. The results indicatethat the Nusselt number of the 60% sucrose solution obviously increased with the number of RSTT but increased inconspicuouslywith 2 and more twisted tapes. The simulation shows that the distance for achieving an optimal heat transferperformance is 46 times the diameter of the tube. The mechanism of the natural convection heat transfer enhancement of the60% sucrose solution in relationship with the CD and the RSTT was analyzed, and the change of average tangential velocitywith the axial distance was presented to demonstrate that the enhancement of heat transfer was realized mainly because of the increase in tangential velocity.     

天然气加热炉腐蚀防垢技术研究 Ⅰ.清洗与钝化

对新疆某油田采油三厂的燃气加热炉的清洗钝化及药剂配方实施方案进行了研究。结果表明,清洗剂WXT-336:30%～40%、复合缓蚀剂WXT-806:3%～5%;此清洗液在室温条件下对碳钢设备的腐蚀速率可控制在≤3.27g/(m2·h),远小于酸洗国家标准(碳钢腐蚀速率≤8.0g/(m2·h))。采用液氨调节pH值,钝化剂WXT-508可一步完成漂洗和钝化处理,形成的钝化膜膜质好。     

Pretreatment with citric acid or a mixture of nitric acid and citric acid to suppress egg white protein deposit formation on stainless steel surfaces and to ease its removal during cleaning

Fouling, adhesion of protein onto a food contact surface, is an important difficulty hindering the pasteurization processing of egg products. To explore a strategy for efficient cleaning of a food contact surface fouled by adherent egg protein, this study investigated the effects of stainless steel surface pretreatment with citric acid or a mixture of nitric acid and citric acid on the adhesion and removability of egg white protein. The 1.05% citric acid pretreatment for 120 min was effective to suppress egg white protein adhesion to a stainless steel surface at 30–80 °C. Pretreatment with nitric acid (1.05% or 4.55%) containing 1.05% citric acid was also effective at 60 °C, which is relevant as a practical pasteurization temperature of egg products. Reducing the pretreatment time from 120 to 15 min was still effective to suppress egg white protein adhesion significantly. Pretreatment with 1.05% nitric acid containing 1.05% citric acid caused higher removability of adhered protein during the cleaning process, especially at higher temperatures. These results demonstrate that pretreatment with nitric acid containing citric acid might be an excellent choice for promoting the efficient cleaning of food manufacturing equipment that has been fouled with egg products.     

Disinfecting efficacy of a plastic container covered with photocatalyst for postharvest

The simplification of the cleaning process of plastic containers used in the storage and/or distribution of fruits or vegetables is important. We coated a plastic container with an apatite-coated titanium dioxide photocatalyst (TiO₂–Ap container), and examined its disinfecting efficacy under UV irradiation from black light. The disinfecting efficacy of the TiO₂–Ap container on diluted drops evaporated from spinach (suspension) was examined. Changes in the microbial populations of the total aerobic bacteria, coliform bacteria, and moulds and yeasts in the TiO₂–Ap container were assayed at 25 °C for 24 h (UV-A intensity of 0.2 and 0.4 mW cm⁻²). The results showed that all of the microbial populations in the TiO₂–Ap container decreased with irradiation time and then reduced to uncountable levels. It was found that the increase in UV-A intensity enhanced the disinfecting efficacy.     

肩部减薄三通塑性极限面内弯矩的分析

三通在使用中受介质的腐蚀或冲刷会在肩部产生局部减薄,从而降低其使用的完整性。鉴于此,采用弹塑性有限元方法,分析了肩部减薄缺陷对三通极限载荷的影响。研究表明缺陷的轴向长度对三通的极限面内弯矩影响较小。在将常用三通几何尺寸简化为等径不等壁厚形式的基础上,建立了覆盖常用三通几何尺寸及缺陷尺寸的塑性极限面内弯矩有限元解数据库,最终拟合得到具有较高精度的塑性极限面内弯矩工程估算公式。     

柔性套管铰链接头力学分析

在合适的单元长度和铰链转角下,柔性套管可以较好地适应弯曲的井眼。在套管的提升过程中,由于提升力的作用,铰链接头的失效形式一般表现为铰链拉脱或强度不足。根据柔性套管铰链接头的结构和受力特点,对其受力进行了简化,建立了力学分析模型———受边缘力系作用的长圆筒,并给出了其变形的基本方程,得到了铰链边缘的径向位移和转角的计算公式,形成了完整的柔性套管铰链接头的力学分析模型。当铰链承受196kN的拉力时,铰链外筒的径向位移为051mm,对应的边缘转角为25°,铰链不会拉脱,强度校核满足要求。     

定向喷嘴布置对PDC钻头齿清洗能力的影响

PDC钻头齿的清洗能力对PDC钻头破岩和清岩影响很大,定向喷嘴则有利于钻头齿的清岩,研究定向喷嘴的布置具有重要意义。使用数值模拟的方法研究了定向喷嘴数量、孔径、喷速等因素对PDC钻头齿清洗效果的影响。研究结果表明,5喷嘴的PDC钻头齿清洗能力较强;钻头齿清洗能力随喷嘴孔径增大而增强;喷射角小的喷嘴射流流场不利于流体向上举升岩屑。将定向喷嘴优化并配合常规水力结构设计可以在PDC钻头预防和清除泥包方面发挥自身的优势,最终达到提高机械钻速的目的。     

Production of aviation fuel by bioethanol conversion on zeolite catalysts

The catalytic process of two-stage conversion of ethanol into jet fuel, wherein the second step is the hydrogenation of aromatic hydrocarbons obtained in the first step, has been studied. It has been shown that at 400°C and an ethanol space velocity of LHSV = 2 h^–1, aromatic hydrocarbons are produced, which are hydrogenated on a Pt/C catalyst in an autoclave at 80–100 atm and T = 200–250°C for 1.5 h with a final yield of naphthenic hydrocarbons on a fed ethanol basis of 15–20%.