本文選題：BOG壓縮機　切入點：隔冷液　出處：《蘭州交通大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：LNG(液化天然氣)作為清潔高效的能源,由于其具有環(huán)境友好,能源效率高等方面的顯著優(yōu)點,已經(jīng)成為了現(xiàn)階段發(fā)展利用的主要能源。LNG在運輸和卸載之時,會產(chǎn)生大量的閃蒸氣,BOG壓縮機作為處理這些閃蒸氣的重要部件,已成為了研究的重點。因為BOG壓縮機的進氣溫度低,因此氣缸壁的溫度場和應(yīng)力場與常溫相比會相差很大,通入隔冷液具有一定的保冷效果,防止低溫向壓縮機別的部位進行傳遞。由于BOG壓縮機的進氣溫度為110K,處于超低溫狀態(tài),因此很難進行實地的測試,本文通過CFD模擬,對BOG壓縮機氣缸壁進行分析,改變不同的參數(shù)條件,如隔冷液流量溫度,以及加入雙缸的模型,來觀察它的應(yīng)力場和溫度場,為BOG壓縮機的研制提供一定的數(shù)值依據(jù)。本文以BOG壓縮機氣缸體為主要的研究對象,通過Solidworks對氣缸體進行1:1的建模,導(dǎo)入不同的邊界條件,在Fluent中進行計算,將Fluent得出的溫度場插值到缸體模型之中,在Workbench中將溫度場和應(yīng)力場結(jié)合起來,分析其變形量和熱應(yīng)力的大小。采用標(biāo)準(zhǔn)k-ε的湍流模型,對壓縮氣體(主要是甲烷)的過程,進行動網(wǎng)格模擬分析。一級氣缸排氣溫度約為152K,二級氣缸的排氣溫度為181K。觀察每一個時刻氣缸內(nèi)溫度從上到下溫度相差不足1K,因此用一個固定的溫度值進行簡化替代。壓縮為一個周期性的運動,可以用一個積分公式,計算出平均的溫度。采用流固耦合和溫度差值順序耦合的方法對氣缸的溫度場和應(yīng)力場進行研究。單級氣缸模擬時發(fā)現(xiàn)通入隔冷液對于氣缸的保冷是十分有效的,對比沒有通入隔冷液時氣缸底部的溫度場發(fā)現(xiàn),單級氣缸的溫度普遍上升了110K-140K。通過改變隔冷液的流速發(fā)現(xiàn),氣缸的應(yīng)力和變形量隨著隔冷液流速增加而不斷減小,當(dāng)隔冷液流速增大到1.5m/s時,再繼續(xù)加大流速,氣缸底面的溫度幾乎不發(fā)生改變。相反增大隔冷液的流速,會增加流動阻力,因此隔冷液流速穩(wěn)定在1.5m/s附近時,氣缸壁的熱應(yīng)力更小,對于壓縮機的穩(wěn)定運行更佳。在保持流速不變的前提下,通過增加隔冷液的溫度發(fā)現(xiàn),隨著隔冷液溫度的升高,氣缸壁的熱應(yīng)力也在不斷地減小,因此增大隔冷液的溫度,也是減小熱應(yīng)力的另一個辦法。在隔冷液溫度由263K上升到293K的過程中,熱應(yīng)力由11.42MPa下降到9.74MPa。對雙級氣缸模擬時采用和單級氣缸相同的方法,通入隔冷液對雙級氣缸的保冷同樣是有很大的效果。和未通入隔冷液時的底面溫度對比,雙級氣缸的溫度普遍上升了70-90K。由于雙級氣缸在兩個氣缸的交界處存在一個溫度的過渡區(qū)域,在此過渡的區(qū)域,會產(chǎn)生很大的變形量,模擬結(jié)果顯示變形量約為1.41mm。因此在實際實驗當(dāng)中,要著重設(shè)計和觀察這部分的變化,以防止發(fā)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.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TE974

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