【摘要】：直接空冷系統(tǒng)經(jīng)過近些年的發(fā)展,技術日趨成熟,目前正處于廣泛應用的階段。直接空冷系統(tǒng)采用環(huán)境空氣作為介質(zhì)冷卻汽輪機乏汽,空冷凝汽器作為直接空冷系統(tǒng)的核心設備,其可靠的冷卻性能是電廠穩(wěn)定、經(jīng)濟運行的關鍵。由于空冷單元布置于自然環(huán)境流場中,其換熱性能受環(huán)境風的影響較大。本文以某電廠600MW直接空冷機組單列空冷單元為例,針對直接空冷凝汽器換熱性能受環(huán)境風影響大的問題,在直接空冷平臺的邊緣加裝擴壓導流葉柵。設計了8種不同葉型的擴壓導流葉柵,利用Fluent軟件,建立加裝擴壓導流葉柵后單列空冷單元的數(shù)值模型,模擬計算得到了各空冷單元的換熱情況,分析了加裝擴壓導流葉柵對直接空冷凝汽器換熱性能的改善作用。同時研究了葉片導流角度、葉片個數(shù)以及葉柵安裝位置對直接空冷凝汽器換熱性能的影響。結果表明,加裝擴壓導流葉柵能有效地改善環(huán)境風工況下空冷單元的流場,消除空冷單元內(nèi)及風機入口處的渦旋,并且能夠降低各軸流風機入口處冷卻空氣的平均溫度,其中,越靠近迎風面的空冷單元改善效果越明顯。其次,加裝擴壓導流葉柵提升了空冷凝汽器整體的換熱性能;當環(huán)境風速較高時,優(yōu)化效果顯著;在8m/s的環(huán)境風速下,加裝擴壓導流葉柵后空冷單元整體換熱效率提高了8%。對比結果顯示,在所選的八種葉型中,NACA6412葉片所組成的葉柵對空冷凝汽器性能的提升最為顯著。在此基礎上對擴壓導流葉柵的結構參數(shù)進行優(yōu)化,得到最佳的葉片導流角度為45°;且葉片個數(shù)越多提升效果越明顯;在空冷單元中間再加裝一列葉柵,凝汽器整體換熱性能夠得到進一步的提升。
[Abstract]:With the development of direct air-cooling system in recent years, the technology of direct air-cooling system is becoming more and more mature and it is in the stage of extensive application. Direct air-cooling system uses ambient air as medium to cool steam turbine exhaust steam, air-cooled condenser as the core equipment of direct air-cooling system, and its reliable cooling performance is the key to stable and economical operation of power plant. Because the air cooling unit is arranged in the natural environmental flow field, the heat transfer performance of the unit is greatly affected by the environmental wind. Taking a single row air-cooling unit of 600MW direct air-cooling unit in a power plant as an example, in order to solve the problem that the heat transfer performance of direct air-cooled condenser is greatly affected by environmental wind, the expansion pressure guide cascade is installed on the edge of the direct air-cooling platform. Eight kinds of diffuser cascade were designed. The numerical model of single-row air-cooling element was established by using Fluent software, and the heat transfer of each air-cooling unit was obtained by simulation calculation, and the heat transfer of each air-cooling unit was obtained by using the numerical model of single-row air-cooling unit after adding the diffuser cascade. The improvement of heat transfer performance of direct air-cooled condenser with expanded pressure guide cascades is analyzed in this paper. At the same time, the influence of blade diversion angle, blade number and cascade installation position on the heat transfer performance of direct air-cooled condenser is studied. The results show that the installation of diffuser cascade can effectively improve the flow field of the air cooling unit under the ambient wind condition, eliminate the vortex in the air cooling unit and the inlet of the fan, and reduce the average temperature of the cooling air at the inlet of each axial flow fan, among which, the flow field of the air cooling unit in the air cooling unit and the inlet of the fan can be eliminated. The more close to the upwind surface, the more obvious the improvement effect of the air-cooling unit is. Secondly, the whole heat transfer performance of the air-cooled condenser is improved by adding the diffuser cascade, and the optimization effect is remarkable when the ambient wind speed is high. Under the ambient wind speed of 8m/s, the overall heat transfer efficiency of the air-cooled unit after installing the diffuser cascade is increased by 8%. The results show that the cascade composed of NACA6412 blades has the most significant improvement on the performance of air-cooled condenser among the eight selected blade profiles. On this basis, the structural parameters of the diffuser cascade are optimized, and the optimal blade diversion angle is 45 擄, and the more the blade number, the more obvious the improvement effect is. By adding a series of cascades to the air-cooled unit, the overall heat transfer of the condenser can be further improved.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621

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