饲料逆流冷却器结构优化及冷却模型分析
发布时间：2018-08-28 08:42
【摘要】：在颗粒饲料制粒加工流程中,冷却是最后一道工序,直接影响饲料成品的质量。逆流冷却器以其占地面积小、能耗低、操作简便等优点成为目前广泛采用的颗粒饲料冷却设备。本文以饲料逆流冷却器为研究对象,针对其排料机构漏料多、风阻大,冷却器内风速场均匀性差,冷却机理的理论研究匮乏等问题,设计了改进型排料机构,有效改善了其工作性能。分析了不同排料方案下风速场的均匀性指标,为排料机构的结构优化提供参考。研究了进料过程造成的低料位对风速均匀性的影响并提出了应对措施。建立了冷却过程的数学模型并研究了各工艺参数对冷却过程的影响,为实际生产中工艺优化策略提供了有效的理论指导。本文主要研究内容如下:(1)利用SolidWorks设计了新型翻板排料机构,完成了冷却器总体结构设计,并对设备所有驱动系统进行了设计计算。(2)利用ANSYS分析了危险部件在工作状况下的应力、应变以及最大变形量,包括箱体、翻板、设备支架、撒料器四部分。结果表明,所有应力值均在材料许用应力范围内,最大变形量在设备工作许可范围内。(3)建立了6种排料方案下冷却器的CFD模型,利用Fluent分别模拟了这6种方案下冷却器内的风速场,在Matlab中进行数据处理,得出风速场在X、Y、Z三个方向上的均匀性系数。结果表明:在水平面平行于进风方向(X方向),随气流的上升,6种类型冷却器内风速均匀性都有改善;在水平面垂直于进风方向(Y方向),随气流的上升,5种方案下风速均匀性系数基本保持恒定,而本文所设计的排料机构下,风速均匀性系数初始值较低,但随着气流的上升逐渐提高,对饲料的最终含水率影响不大;在竖直方向上(Z方向),4种方案下风速均匀性随气流上升而增大,2种方案下风速均匀性出现较大波动,这是由于多层排料结构限制了风速均匀性在竖直方向上的提升。通过研究低料位工况下的风速场,发现将低料位计安装高度控制在0.3m以上可降低进料过程中低料位对风速均匀性的影响。(4)将饲料深床冷却简化为若干薄层,根据热质传递的基本理论推导了饲料冷却干燥的偏微分方程;建立了饲料的干燥性能参数比热、平衡含水率的模型及干燥介质空气的参数模型并确立了薄层干燥方程的形式;用向前差分方法对偏微分方程进行离散化处理后在Matlab软件中编制程序进行数值计算,得出给定工况下任意干燥时间、任意料层高度处饲料的含水率、温度及空气的湿度、温度;分析了空气的初始温度、湿含量、风量(风速),饲料的初始含水率、初始温度,料层高度以及停留时间对饲料冷却过程的影响。
[Abstract]:In the granulation process of pellet feed, cooling is the last process, which directly affects the quality of feed product. Countercurrent cooler has become a widely used pellet feed cooling equipment because of its advantages of small area, low energy consumption and easy operation. In this paper, the feed countercurrent cooler is taken as the research object. The improved discharging mechanism is designed in order to solve the problems such as much leakage, large air resistance, poor uniformity of wind velocity field in the cooler and lack of theoretical research on cooling mechanism. Its working performance is improved effectively. The uniformity index of wind velocity field under different discharge schemes is analyzed, which provides a reference for the structure optimization of discharging mechanism. The effect of low level of feed on the uniformity of wind speed was studied and the countermeasures were put forward. The mathematical model of the cooling process is established and the influence of various process parameters on the cooling process is studied, which provides an effective theoretical guidance for the process optimization strategy in practical production. The main contents of this paper are as follows: (1) A new type of tipping mechanism is designed by using SolidWorks, the overall structure of the cooler is designed, and all the driving systems of the equipment are designed and calculated. (2) the stress of the dangerous parts under the working condition is analyzed by using ANSYS. Strain and maximum deformation, including box, flip plate, equipment support, sprinkler four parts. The results show that all stress values are within the allowable stress range of materials, and the maximum deformation is within the working permission range of the equipment. (3) the CFD model of coolers under six discharge schemes is established. The wind velocity field in the cooler was simulated by Fluent, and the data were processed in Matlab. The uniformity coefficient of the wind velocity field in three directions was obtained. The results show that when the horizontal plane is parallel to the inlet direction (X direction), the uniformity of wind velocity in 6 types of coolers is improved with the increase of air flow. When the horizontal plane is perpendicular to the inlet direction (Y direction), the wind velocity uniformity coefficient remains basically constant under five schemes with the increase of the air flow, but the initial value of the wind speed uniformity coefficient is lower under the discharge mechanism designed in this paper. However, with the increase of air flow, the final moisture content of feed has little effect, and the uniformity of wind speed fluctuates with the increase of air flow under the vertical direction (Z direction). This is due to the multilayer layout structure which limits the vertical elevation of wind speed uniformity. By studying the wind velocity field under low material level condition, it is found that the influence of low material level on the uniformity of wind speed can be reduced by controlling the installation height of low material level meter above 0.3 m. (4) the feed deep bed cooling is simplified to several thin layers. According to the basic theory of heat and mass transfer, the partial differential equation of feed cooling and drying was deduced, and the specific heat, equilibrium moisture content model and air parameter model of drying medium were established, and the form of thin-layer drying equation was established. The forward difference method is used to discretize the partial differential equation and the program is compiled in Matlab software to calculate the moisture content, temperature, humidity and temperature of the feed at any drying time and any layer height under given working conditions. The effects of initial air temperature, moisture content, air volume (wind speed), initial moisture content, initial temperature, height of feed layer and residence time on the cooling process of feed were analyzed.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S817.12
本文编号：2208876
[Abstract]:In the granulation process of pellet feed, cooling is the last process, which directly affects the quality of feed product. Countercurrent cooler has become a widely used pellet feed cooling equipment because of its advantages of small area, low energy consumption and easy operation. In this paper, the feed countercurrent cooler is taken as the research object. The improved discharging mechanism is designed in order to solve the problems such as much leakage, large air resistance, poor uniformity of wind velocity field in the cooler and lack of theoretical research on cooling mechanism. Its working performance is improved effectively. The uniformity index of wind velocity field under different discharge schemes is analyzed, which provides a reference for the structure optimization of discharging mechanism. The effect of low level of feed on the uniformity of wind speed was studied and the countermeasures were put forward. The mathematical model of the cooling process is established and the influence of various process parameters on the cooling process is studied, which provides an effective theoretical guidance for the process optimization strategy in practical production. The main contents of this paper are as follows: (1) A new type of tipping mechanism is designed by using SolidWorks, the overall structure of the cooler is designed, and all the driving systems of the equipment are designed and calculated. (2) the stress of the dangerous parts under the working condition is analyzed by using ANSYS. Strain and maximum deformation, including box, flip plate, equipment support, sprinkler four parts. The results show that all stress values are within the allowable stress range of materials, and the maximum deformation is within the working permission range of the equipment. (3) the CFD model of coolers under six discharge schemes is established. The wind velocity field in the cooler was simulated by Fluent, and the data were processed in Matlab. The uniformity coefficient of the wind velocity field in three directions was obtained. The results show that when the horizontal plane is parallel to the inlet direction (X direction), the uniformity of wind velocity in 6 types of coolers is improved with the increase of air flow. When the horizontal plane is perpendicular to the inlet direction (Y direction), the wind velocity uniformity coefficient remains basically constant under five schemes with the increase of the air flow, but the initial value of the wind speed uniformity coefficient is lower under the discharge mechanism designed in this paper. However, with the increase of air flow, the final moisture content of feed has little effect, and the uniformity of wind speed fluctuates with the increase of air flow under the vertical direction (Z direction). This is due to the multilayer layout structure which limits the vertical elevation of wind speed uniformity. By studying the wind velocity field under low material level condition, it is found that the influence of low material level on the uniformity of wind speed can be reduced by controlling the installation height of low material level meter above 0.3 m. (4) the feed deep bed cooling is simplified to several thin layers. According to the basic theory of heat and mass transfer, the partial differential equation of feed cooling and drying was deduced, and the specific heat, equilibrium moisture content model and air parameter model of drying medium were established, and the form of thin-layer drying equation was established. The forward difference method is used to discretize the partial differential equation and the program is compiled in Matlab software to calculate the moisture content, temperature, humidity and temperature of the feed at any drying time and any layer height under given working conditions. The effects of initial air temperature, moisture content, air volume (wind speed), initial moisture content, initial temperature, height of feed layer and residence time on the cooling process of feed were analyzed.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S817.12
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