隔冷液温度和速度对BOG压缩机温度场及应力场影响的研究

发布时间：2018-03-12 18:37

本文选题：BOG压缩机　切入点：隔冷液　出处：《兰州交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：LNG(液化天然气)作为清洁高效的能源,由于其具有环境友好,能源效率高等方面的显著优点,已经成为了现阶段发展利用的主要能源。LNG在运输和卸载之时,会产生大量的闪蒸气,BOG压缩机作为处理这些闪蒸气的重要部件,已成为了研究的重点。因为BOG压缩机的进气温度低,因此气缸壁的温度场和应力场与常温相比会相差很大,通入隔冷液具有一定的保冷效果,防止低温向压缩机别的部位进行传递。由于BOG压缩机的进气温度为110K,处于超低温状态,因此很难进行实地的测试,本文通过CFD模拟,对BOG压缩机气缸壁进行分析,改变不同的参数条件,如隔冷液流量温度,以及加入双缸的模型,来观察它的应力场和温度场,为BOG压缩机的研制提供一定的数值依据。本文以BOG压缩机气缸体为主要的研究对象,通过Solidworks对气缸体进行1:1的建模,导入不同的边界条件,在Fluent中进行计算,将Fluent得出的温度场插值到缸体模型之中,在Workbench中将温度场和应力场结合起来,分析其变形量和热应力的大小。采用标准k-ε的湍流模型,对压缩气体(主要是甲烷)的过程,进行动网格模拟分析。一级气缸排气温度约为152K,二级气缸的排气温度为181K。观察每一个时刻气缸内温度从上到下温度相差不足1K,因此用一个固定的温度值进行简化替代。压缩为一个周期性的运动,可以用一个积分公式,计算出平均的温度。采用流固耦合和温度差值顺序耦合的方法对气缸的温度场和应力场进行研究。单级气缸模拟时发现通入隔冷液对于气缸的保冷是十分有效的,对比没有通入隔冷液时气缸底部的温度场发现,单级气缸的温度普遍上升了110K-140K。通过改变隔冷液的流速发现,气缸的应力和变形量随着隔冷液流速增加而不断减小,当隔冷液流速增大到1.5m/s时,再继续加大流速,气缸底面的温度几乎不发生改变。相反增大隔冷液的流速,会增加流动阻力,因此隔冷液流速稳定在1.5m/s附近时,气缸壁的热应力更小,对于压缩机的稳定运行更佳。在保持流速不变的前提下,通过增加隔冷液的温度发现,随着隔冷液温度的升高,气缸壁的热应力也在不断地减小,因此增大隔冷液的温度,也是减小热应力的另一个办法。在隔冷液温度由263K上升到293K的过程中,热应力由11.42MPa下降到9.74MPa。对双级气缸模拟时采用和单级气缸相同的方法,通入隔冷液对双级气缸的保冷同样是有很大的效果。和未通入隔冷液时的底面温度对比,双级气缸的温度普遍上升了70-90K。由于双级气缸在两个气缸的交界处存在一个温度的过渡区域,在此过渡的区域,会产生很大的变形量,模拟结果显示变形量约为1.41mm。因此在实际实验当中,要着重设计和观察这部分的变化,以防止发生脆裂。
[Abstract]:As a clean and efficient energy source, LNG (liquefied natural gas) has become the main energy for transportation and unloading at the present stage due to its outstanding advantages of environmental friendliness and high energy efficiency. A large number of flash steam bog compressors have been used as an important part in the treatment of these flash vapours. Because the inlet air temperature of BOG compressor is low, the temperature field and stress field of cylinder wall will differ greatly compared with normal temperature. The coolant has a certain cooling effect and prevents the transfer from low temperature to other parts of the compressor. Because the inlet temperature of BOG compressor is 110K, it is very difficult to carry out field test, so it is very difficult to carry out field test. This paper simulates it by CFD, because the inlet air temperature of BOG compressor is 110K, so it is difficult to carry out field test. By analyzing the cylinder wall of BOG compressor, the stress field and temperature field of BOG compressor are observed by changing different parameters, such as the temperature of cooling fluid flow and the model of adding two cylinders. In this paper, the cylinder block of BOG compressor is taken as the main research object, the cylinder block is modeled with 1: 1 by Solidworks, different boundary conditions are introduced, and the calculation is carried out in Fluent. The temperature field obtained by Fluent is interpolated into the cylinder block model, and the temperature field and stress field are combined in Workbench to analyze the magnitude of deformation and thermal stress. Using the standard k- 蔚 turbulence model, the process of compressed gas (mainly methane) is studied. The exhaust temperature of the first stage cylinder is about 152K, and the exhaust temperature of the secondary cylinder is 181k. it is observed that the temperature difference in the cylinder is less than 1K from top to bottom at each time, so a fixed temperature value is used to simplify it. Instead. Compress into a periodic motion, You can use an integral formula, The average temperature is calculated. The temperature field and stress field of the cylinder are studied by using the method of fluid-solid coupling and sequential coupling of temperature difference. In contrast to the temperature field at the bottom of the cylinder without cooling fluid, it is found that the temperature of the single stage cylinder generally rises by 110K-140K. by changing the velocity of the coolant, it is found that the stress and deformation of the cylinder decrease with the increase of the flow rate. When the flow rate of the coolant increases to 1.5 m / s, the temperature at the bottom of the cylinder will hardly change when the flow rate continues to increase. On the contrary, increasing the velocity of the coolant will increase the flow resistance, so when the velocity of the coolant is stable at 1.5 m / s, The thermal stress of the cylinder wall is smaller, which is better for the stable operation of the compressor. On the premise of keeping the flow rate constant, it is found that the thermal stress of the cylinder wall decreases with the increase of the temperature of the coolant. Therefore, increasing the temperature of the coolant is another way to reduce the thermal stress. In the process of increasing the temperature of the coolant from 263K to 293K, the thermal stress decreases from 11.42 MPA to 9.74 MPA. The cooling insulation liquid also has a great effect on the cooling of the two-stage cylinder. Compared with the bottom temperature when the coolant is not passed through, The temperature of the two-stage cylinder has generally increased by 70-90K. because the two-stage cylinder has a temperature transition area at the junction of the two cylinders, there will be a large amount of deformation in this transitional area. The simulation results show that the deformation is about 1.41mm. so in the actual experiment, we should design and observe the change of this part so as to prevent the brittle fracture.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE974

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