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1.
The particles with a narrow size distribution are proper products in a fluid bed granulation and coating. As well, the process efficiency is one of the most important parameters, and the wall deposition of sprayed liquid reduces it. The modality of spray volume distribution is a key parameter in the definition of particle size distribution and process efficiency. This work is done in two steps: In the first step, an experimental study on spray characteristics including spray flux distribution, spray cone angle, and discharge coefficient is conducted. Based on the experimental data, the curves of liquid volume flux versus nozzle pressure and height are obtained. The results indicate that the flux distribution changes significantly with even small pressure and height changes. In the second step, the granulation process is carried out in a semi-industrial conical fluid bed, and the particles size distribution curves and the deposited mass on the bed wall are obtained. The results show that the precise determination of the spray flux distribution is an appropriate way to predict the well-advised nozzle pressure/height in order to achieve the narrow particle size distribution and high efficiency of the process. 相似文献
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表面织构形状对牙轮钻头轴承摩擦学性能影响的实验研究 总被引:2,自引:0,他引:2
牙轮钻头滑动轴承作为钻头破岩过程中传递载荷的关键部件,在低速重载的钻井过程中易发生黏着磨损失效。为改善牙轮钻头滑动轴承的耐磨性能,利用纳秒激光雕刻技术,在牙轮钻头滑动轴承轴颈表面加工了面积比为10%、深度为20μm的圆形、矩形、三角形及复合织构;基于赫兹相似理论,设计近似模拟钻头轴承工况的环-块配对副单元实验方案,并在UMT摩擦试验机上开展织构形状对钻头滑动轴承摩擦副摩擦因数、磨损量、温升变化和微观形貌影响规律的实验研究。结果表明:仿生织构的形状及布置方式对减摩和耐磨效果影响极大,其中圆形、矩形织构的减摩和耐磨性能最优,其次为三角形织构,而复合织构反而增大了摩擦因数及磨损量;单一织构对试件磨损量及温升的影响不大,而复合织构在增加摩擦的同时温度有明显升高,不利于井下高温环境下延长牙轮钻头寿命。 相似文献
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本文重点研究了自制深锥形干扰沉降分级机在不同影响因素下对细粒煤的分级效率,结果表明:底部和中部同时给水形式的设计有利于细粒煤分级,底部与中部给水量比值对分级效率有一定影响但不明显;给料速度及浓度值越低,细粒煤分级效率越高。该装置的适宜分级条件为流量配比2∶1、给料速度0.50m/s、矿浆浓度40%时,粒级级配(0.25~0.125mm和1.0~0.5mm)分级效率接近65%,较常规分级旋流器分级效率50%~60%提高约5%~15%,实验结果表明深锥形干扰沉降分级机可有效实现细粒煤的分级。 相似文献
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针对鸡枞菌人工锥形削根速度慢、一致性差等问题,设计了锥形削根装置。该装置采用两个对称布置的四连杆机构,连杆刀片运动轨迹呈腰形,两个刀片的直线工作段形成圆锥包络,实现鸡枞菌根部锥形切削。装有摄像头的机械臂识别、抓取并精确控制鸡枞菌进入切削区域的深度,实现精准切削。试验结果表明:两个连杆刀片在0.8s内共进行12次作业,完成锥形切削;装置可在6s内实现1个鸡枞菌的抓取、切削、分级,不仅速度快,且一致性更好。以菇柄直径为12mm的鸡枞菌为例,对比人工削根形成的7棱、6棱、5棱和4棱锥,试验装置削根可分别减少7.5%,9.1%,13.9%,24.4%的根部浪费率。 相似文献
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Toxicity of smoke generated in a fire is difficult to measure accurately. That is because gas sensors for measuring rapidly varying concentrations of toxic gases are not yet developed. Simple expressions are searched for quick measurement in assessing smoke toxicity practically. Four equations on calculating fractional effective dose (FED) related to toxic effluents were reported in the literature, each based on different assumptions. FED value was proposed to be calculated based on peak carbon monoxide concentration and peak carbon dioxide concentration, and transient carbon monoxide, carbon dioxide, and oxygen concentrations. The four values were compared in this article using literature data on toxic gases from different materials measured by (i) cone calorimeter; (ii) full-scale burning tests; and (iii) tunnel full-scale tests. Measured carbon monoxide, carbon dioxide, and oxygen concentrations by standard equipment of oxygen consumption calorimeters were used to calculate the four FED values. It is found that the values of FED based on peak carbon monoxide and carbon dioxide concentrations (denoted as FED2) are similar to the average values of FED calculated from the updated equation in the literature using the oxygen consumption calorimeters. Putting the values of FED2 in fire safety design guides is then recommended. 相似文献
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耐火衬里及支撑结构设计的可靠性是保证高温反应器壳体温度小于设计温度的关键因素。针对耐火衬里结构失效导致反应器壳体温度超过设计温度的问题,提出了一种双金属焊接的密封锥结构。该结构具有支撑金属衬里的作用以及将耐火材料与金属衬里之间的膨胀空间分割成多个密闭空间以阻止高温气体的流动,进而提高隔热可靠性。采用ANSYS软件中APDL语言建立了密封锥连接结构的有限元模型,通过研究密封锥不同角度以及厚度对计算结果的影响,得出了密封锥的最佳结构参数,并满足ASME标准的应力强度评定要求。模拟结果可为此类高温反应器耐火衬里结构的设计提供参考依据。 相似文献
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Pavel P. Fedorov Vera Y. Proydakova Sergey V. Kuznetsov Valery V. Voronov Alexandr A. Pynenkov Konstantin N. Nishchev 《Journal of the American Ceramic Society》2020,103(5):3390-3400
The thermal analysis and X-ray powder diffraction studies of the Li2SO4–Na2SO4 system, including the high-temperature X-ray diffraction technique, have elucidated four phases of variable composition: three solid solutions based on the α-Li2SO4, α-Na2SO4, and α-LiNaSO4 high-temperature polymorphs, and a low-temperature β-LiNaSO4 phase. α-Na2SO4-Base solid solution disintegrates into two phases via a monotectoid phase transformation. It is quite probable that the monotectoid process is related to the conversion of the second-order phase transition to the first-order phase transition. 相似文献
10.
Eshan Ganju Monica Prezzi Rodrigo Salgado Nayyar Zia Siddiki 《International Journal of Pavement Engineering》2018,19(11):966-975
The Dynamic Cone Penetrometer (DCP) is a device that is used in the construction industry for the assessment of in situ soil compaction quality. Over the past few decades, numerous correlations have been developed between the DCP test results and soil strength and stiffness parameters. This paper proposes a comprehensive set of criteria and recommendations for quality control (QC) of compacted subgrade that take into account the inherent statistical variability of DCP test results. For the development of the QC criteria, a new statistical methodology is used to extract representative test values from the raw field DCP test data. In order to use the proposed QC criteria, soils are first classified into two broad categories (fine-grained and coarse-grained) depending on their fabric and response to compaction efforts. Test results indicate that (i) for fine-grained soils, the DCP test values have good correlation with the plasticity index (PI), which is indicative of the type and amount of clay content of the soil and (ii) for coarse-grained soils, the DCP test values have good correlation with the optimum water content of the soil, which is directly related to its in situ density. DCP blow count correlation equations are presented for both soil categories. Recommendations for field DCP testing and data analysis are also provided to highlight the significance of the statistical distribution of the DCP test results in QC testing of compacted subgrade. 相似文献