水泵水轮机泵工况开停机过程导叶小开度区特殊流态研究

发布时间：2018-05-30 08:21

本文选题：水泵水轮机 + 开停机过程　；参考：《西安理工大学》2017年硕士论文

【摘要】：水泵水轮机在运行过程中工况转换频繁,在工况转换过程中保证机组稳定运行是至关重要的。近年来,在某些抽水蓄能电站水泵水轮机开停机过程中,当活动导叶开度很小时,导水机构会出现振动和异常噪音。为了找出引起这种不稳定现象的原因,论文对水泵水轮机泵工况开停机过程小开度区出现的不稳定现象进行了深入研究。论文以天荒坪电站水泵水轮机为研究对象,建立了从蜗壳进口至尾水管出口的三维全流道几何模型,以电站全系统过渡过程计算结果为边界条件,运用动网格技术对其开停机过程进行了详细的研究,定量分析了开停机过程中特殊流态的形成机理和流动规律。研究表明,导叶间的主流会随着开度的变化在两种流态之间偏转。即在常规流态(I型流态)与特殊流态(II型流态)之间变化。在开机过程中,当开度非常小时,主流呈现II型流态,随着开度的增大,主流开始从II型流态向I型流态偏转,当开度继续增大时,主流呈现I型流态。在停机过程中,当开度较大的时候,主流呈现I型流态,随着开度减小,主流开始从I型流态向II型流态偏转,当开度继续减小,主流呈现II型流态。在周向不同导叶之间,流态偏转的开度和偏转时间略有不同,但趋势一致。开机过程和停机过程流动的偏转过程也有差异,停机过程流动偏转持续时间长,主流在偏转过程中会往复摆动。主流的偏转会引起导叶周围流场的剧烈变化,使得活动导叶水力矩发生突变,引起导水机构产生异常振动和噪音,研究结果与电站开停机过程小开度区实际运行结果相吻合,揭示了水泵水轮机开停机过程中导水机构产生振动的原因。通过分析活动导叶在开停机过程中的应力变化规律,阐明了水泵水轮机泵工况开停机过程中小开度区出现的不稳定诱因,结果表明:导叶最大静应力发生在导叶端面与轴颈相接处,主流流态的偏转会使活动导叶的内部应力发生剧烈变化,引起机组的不稳定。
[Abstract]:The operating conditions of pump turbines change frequently during operation, so it is very important to ensure the stable operation of water pump turbines. In recent years, in some pumped storage power stations, the vibration and abnormal noise of water guide mechanism will appear when the active guide vane is very small during the opening and shutdown of pump turbine. In order to find out the causes of the instability, this paper deeply studies the instability in the small opening and down zone during the pump operating condition. Taking the pump turbine of Tianhuangping Hydropower Station as the research object, a three-dimensional full-channel geometric model from the inlet of the volute to the outlet of the draft pipe is established. The results of the whole system transition process of the power station are taken as the boundary conditions. The dynamic grid technology is used to study the on-off process in detail, and the formation mechanism and flow law of the special flow state in the on-off process are quantitatively analyzed. It is shown that the mainstream of the guide vane will deflect between the two flow states with the change of opening. That is to say, the variation between the normal flow pattern and the special flow state is between the normal flow mode and the special flow state. In the process of start-up, when the opening is very small, the mainstream presents type II flow state. With the increase of opening degree, the mainstream begins to deflect from type II flow state to mode I flow state, and when the opening degree continues to increase, the mainstream presents mode I flow state. In the process of downtime, when the opening degree is large, the mainstream presents mode I flow state. With the decrease of opening degree, the mainstream begins to deflect from mode I flow state to type II flow state, and when the opening degree continues to decrease, the mainstream presents type II flow state. The opening degree and the deflection time of the flow state deflection are slightly different between the circumferential guide vane, but the trend is the same. There are also differences in the flow deflection process between the start-up process and the shutdown process. The flow deflection duration of the shutdown process is long and the mainstream will swing back and forth during the deflection process. The deflection of the mainstream will cause drastic changes in the flow field around the guide vane, causing a sudden change in the water torque of the active guide vane, resulting in abnormal vibration and noise of the water-conducting mechanism. The results of the study are in agreement with the actual operation results of the small opening and closing zone during the power station's opening and shutdown process. The cause of the vibration of the guide water mechanism during the opening and stopping process of the pump turbine is revealed. Based on the analysis of the stress variation of the guide vane during the process of opening and stopping, the unstable inducement of the small open and down zone in the operating condition of pump turbine pump is expounded. The results show that the maximum static stress of the guide vane occurs at the junction of the end face of the guide vane and the shaft neck, and the deflection of the main flow state will make the internal stress of the moving guide vane change dramatically and cause the instability of the unit.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV743;TV734

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