AP1000核电汽轮机中压阀内流动特性数值模拟

发布时间：2018-06-26 14:51

本文选题：核电汽轮机 + 中压阀门　；参考：《华北电力大学》2016年硕士论文

【摘要】：进汽阀门是汽轮机的进汽调节设备,其性能优劣决定了汽轮机运行的经济性和安全可靠性。核电机组的进汽初参数低,进汽质量流量大,中压进汽管道比高压进汽管道内的蒸汽容积流量大很多,蒸汽作用力对中压阀门产生的扭矩很大,所以阀门在动作过程中易发生卡涩故障。核电机组主蒸汽为饱和蒸汽,在中压阀内易发生湿蒸汽两相流,降低机组的运行效率,所以对于核电汽轮机中压阀内的蒸汽流动研究十分必要。本文利用FLUENT对AP1000核电汽轮机中压进汽阀内的流动特性进行了数值模拟。分别对调节阀在不同开度下的速度场、压力场进行分析,并讨论阀门压损和气动力矩随调节阀开度的变化规律。研究湿蒸汽汽水两相流在阀内的流场、压损和气动力矩随调节阀开度的变化规律,并将所得的结果与蒸汽单相流的模拟结果进行比较分析。模拟结果表明:主汽阀和调节阀全开时,阀内的压力和速度分布均匀对称。调节阀开度减小为60°或30°时,调节阀碟周围蒸汽流度变化显著,由于调节阀碟的阻挡,在其后形成了涡流。随调节阀开度的减小,调节阀处的压损占阀门总压损的比例逐渐增大。调节阀开度大致在75°以下时,调节阀处的压损大于主汽阀处的压损,当调节阀开度为30°时,主汽阀处的压损相对于调节阀处的压损可以忽略不计。调节阀开度增大过程中,气动力矩先逐渐变大,当开度达到30°左右,气动力矩达到最大值,之后气动力矩随开度增大而逐渐减小至0。湿蒸汽两相流和蒸汽单相流在阀内的流场分布相似,湿蒸汽中蒸汽与水滴之间存在相对滑移,造成摩擦损失,所以调节阀在10°、40°、90°三种开度下,两相流在阀内的最大流速均低于单相流的最大流速。调节阀同等开度下,湿蒸汽两相流的压损将近是单相流的两倍。调节阀在10°、40°、90°三种开度下,蒸汽中含水率由0.5%增加到2%时,压损均增加了一倍多,所以蒸汽含水率严重影响机组运行的经济性。两相流与单相流对阀门气动力矩的变化规律相似,调节阀同等开度下,两相流比单相流产生的气动力矩均有不同程度的增加,当调节阀开度为30°时,两相流与单相流气动力矩的差值为最大值,所以湿蒸汽使阀门更易发生卡涩故障。
[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 掳or 30 掳, 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 掳, 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 掳, 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 掳, 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 掳~ 40 掳/ 90 掳. 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 掳, 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 掳at 10 掳~ 40 掳~ 90 掳, 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 掳, The difference between two-phase flow and single-phase flow is the maximum, so wet steam makes the valve more prone to jam failure.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK263

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