發(fā)布時間：2018-06-26 14:51

  本文選題：核電汽輪機 + 中壓閥門　； 參考：《華北電力大學》2016年碩士論文

【摘要】：進汽閥門是汽輪機的進汽調節(jié)設備,其性能優(yōu)劣決定了汽輪機運行的經濟性和安全可靠性。核電機組的進汽初參數(shù)低,進汽質量流量大,中壓進汽管道比高壓進汽管道內的蒸汽容積流量大很多,蒸汽作用力對中壓閥門產生的扭矩很大,所以閥門在動作過程中易發(fā)生卡澀故障。核電機組主蒸汽為飽和蒸汽,在中壓閥內易發(fā)生濕蒸汽兩相流,降低機組的運行效率,所以對于核電汽輪機中壓閥內的蒸汽流動研究十分必要。本文利用FLUENT對AP1000核電汽輪機中壓進汽閥內的流動特性進行了數(shù)值模擬。分別對調節(jié)閥在不同開度下的速度場、壓力場進行分析,并討論閥門壓損和氣動力矩隨調節(jié)閥開度的變化規(guī)律。研究濕蒸汽汽水兩相流在閥內的流場、壓損和氣動力矩隨調節(jié)閥開度的變化規(guī)律,并將所得的結果與蒸汽單相流的模擬結果進行比較分析。模擬結果表明:主汽閥和調節(jié)閥全開時,閥內的壓力和速度分布均勻對稱。調節(jié)閥開度減小為60°或30°時,調節(jié)閥碟周圍蒸汽流度變化顯著,由于調節(jié)閥碟的阻擋,在其后形成了渦流。隨調節(jié)閥開度的減小,調節(jié)閥處的壓損占閥門總壓損的比例逐漸增大。調節(jié)閥開度大致在75°以下時,調節(jié)閥處的壓損大于主汽閥處的壓損,當調節(jié)閥開度為30°時,主汽閥處的壓損相對于調節(jié)閥處的壓損可以忽略不計。調節(jié)閥開度增大過程中,氣動力矩先逐漸變大,當開度達到30°左右,氣動力矩達到最大值,之后氣動力矩隨開度增大而逐漸減小至0。濕蒸汽兩相流和蒸汽單相流在閥內的流場分布相似,濕蒸汽中蒸汽與水滴之間存在相對滑移,造成摩擦損失,所以調節(jié)閥在10°、40°、90°三種開度下,兩相流在閥內的最大流速均低于單相流的最大流速。調節(jié)閥同等開度下,濕蒸汽兩相流的壓損將近是單相流的兩倍。調節(jié)閥在10°、40°、90°三種開度下,蒸汽中含水率由0.5%增加到2%時,壓損均增加了一倍多,所以蒸汽含水率嚴重影響機組運行的經濟性。兩相流與單相流對閥門氣動力矩的變化規(guī)律相似,調節(jié)閥同等開度下,兩相流比單相流產生的氣動力矩均有不同程度的增加,當調節(jié)閥開度為30°時,兩相流與單相流氣動力矩的差值為最大值,所以濕蒸汽使閥門更易發(fā)生卡澀故障。
[Abstract]:Intake valve is the steam inlet regulating equipment of steam turbine. Its performance determines the economy and safety reliability of steam turbine operation. For nuclear power units, the initial parameters of steam intake are low, the mass flow is large, the volume flow of steam in the medium pressure steam intake pipeline is much larger than that in the high pressure steam inlet pipeline, and the torque generated by steam force on the medium pressure valve is very large. So the valve in the course of action is prone to jam fault. Because the main steam of nuclear power unit is saturated steam, the wet steam two-phase flow is easy to occur in the middle pressure valve, which reduces the operation efficiency of the unit, so it is necessary to study the steam flow in the middle pressure valve of nuclear power turbine. In this paper, the flow characteristics in the medium pressure inlet valve of AP1000 nuclear turbine are numerically simulated by fluent. The velocity field and pressure field of the regulating valve under different opening degrees were analyzed, and the variation of valve pressure loss and aerodynamic moment with the valve opening was discussed. The flow field, pressure loss and aerodynamic torque of wet steam two-phase flow in the valve are studied. The results obtained are compared with the simulation results of the single-phase steam flow. The simulation results show that when the main steam valve and the regulating valve are fully open, the pressure and velocity distribution in the valve is uniform and symmetrical. When the opening of the control valve decreases to 60 擄or 30 擄, the steam mobility around the disc changes significantly. With the decrease of valve opening, the proportion of pressure loss to total valve pressure loss increases gradually. When the opening of the control valve is below 75 擄, the pressure loss at the regulating valve is larger than that at the main steam valve. When the opening of the control valve is 30 擄, the pressure loss of the main steam valve relative to the pressure loss at the control valve can be ignored. In the process of increasing the opening of the regulating valve, the aerodynamic torque becomes larger at first. When the opening reaches about 30 擄, the aerodynamic moment reaches the maximum value, and then decreases to 0 with the increase of opening. The distribution of the flow field in the valve is similar between the two phase flow of wet steam and the single phase flow of steam. There is relative slip between the steam and the water droplet in the wet steam, which results in friction loss. Therefore, the regulating valve is open at 10 擄~ 40 擄/ 90 擄. The maximum velocity of two phase flow in valve is lower than that of single phase flow. The pressure loss of wet steam two-phase flow is nearly twice as high as that of single-phase flow. When the water content in steam increases from 0.5% to 2 擄, the pressure loss of the regulating valve increases by more than one time when the water content in steam increases from 0.5% to 2 擄at 10 擄~ 40 擄~ 90 擄, so the water content of steam seriously affects the operation economy of the unit. The law of variation of valve aerodynamic torque between two phase flow and single phase flow is similar. At the same opening of regulating valve, the aerodynamic torque produced by two phase flow is increased to some extent than that of single phase flow. When the valve opening is 30 擄, The difference between two-phase flow and single-phase flow is the maximum, so wet steam makes the valve more prone to jam failure.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TK263

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