太阳能热发电并联管内汽液两相流不稳定性研究

发布时间：2018-11-26 14:24

【摘要】：平行加热管道中的汽液两相流不稳定性一般发生在锅炉水冷壁、蒸汽发生装置、热交换器以及沸水反应堆中。产生平行管中流量漂移的根本原因是压降与流量关系中特有的N型曲线负斜率部分的存在。消除此不稳定性最经济和有效的方法就是在加热管道的入口处加装节流管圈,以此来使得特性曲线呈现单值性增长的趋势。但是与此同时又会使得管道入口处的给水泵的耗功增加,所以计算出最为合适的节流系数就显得尤为重要。实际工程中加热管道内进出口所需压降的计算以及与进口流量的关系对于设备的设计、安全以及运行都有着至关重要的作用。压降流量特性曲线不仅是分析管道内静态流量漂移特性的依据,更是压力降性脉动和密度波脉动产生的根本所在。本文主要针对在临界压力以下的范围内,已知管道出口压力、进口温度等条件来迭代求取进口压力。并且考虑到在不同压力范围,选取合适的计算模型：低压下的分相模型以及高压下的均相模型;选取不同工况下,最为合适的截面含气率的经验公式。利用MATLAB编写整合不同情况下的水平管道和竖直管道内压降的计算程序。同时,针对平行管道内常出现的流量漂移现象,计算出最小的管道入口节流系数,通过节流系数来反算出进口所需要最为合适的节流阀的直径并通过GUI编写可视化计算截面。本文在计算程序的基础上,特定的针对实际槽式太阳能直接蒸汽发生系统中并联管内的流动加以研究验证。分析不同参数对于流量漂移特性的影响,以此来优化运行。最后研究两相平行管道内避免分层流动所需的最小质量流量,并比较不同方法的特点。
[Abstract]:The two-phase flow instability of the vapor liquid in the parallel heating pipeline generally occurs in the water wall of the boiler, the steam generating device, the heat exchanger and the boiling water reactor. The root cause of the flow drift in the parallel tube is the presence of the negative slope portion of the N-type curve that is specific to the pressure drop and the flow relationship. The most economical and effective way to eliminate this instability is to add a choke coil at the inlet of the heating pipe, so that the characteristic curve presents a tendency of single-value growth. but at the same time, the consumption of the feed pump at the inlet of the pipeline is increased, so the most suitable throttling coefficient is calculated. The calculation of the pressure drop required for the inlet and outlet of the heating pipe in the actual project and the relationship with the inlet flow are of vital importance to the design, safety and operation of the equipment. The pressure drop flow characteristic curve is not only the basis for analyzing the static flow drift characteristic in the pipeline, but also the base of the pressure drop and the pulsation of the density wave. In this paper, the pressure and inlet temperature of the pipeline are known to be used to calculate the inlet pressure in the range of the critical pressure. and taking into account the different pressure ranges, selecting a suitable calculation model: a sub-phase model at low pressure and a homogeneous model under high pressure; and selecting an empirical formula of the most suitable cross-section gas-containing rate under different working conditions. The calculation program of the pressure drop in horizontal and vertical pipes in different cases is prepared by using MATLAB. At the same time, the minimum pipeline inlet throttle coefficient is calculated for the constant flow drift phenomenon in the parallel pipeline, the diameter of the most suitable throttle valve required by the inlet is calculated by the throttle coefficient, and a visual calculation section is written through the GUI. In this paper, on the basis of the calculation program, the flow of a specific needle in the parallel tube of the actual tank type solar direct steam generation system is studied and verified. The effect of different parameters on the flow drift characteristics is analyzed to optimize the operation. Finally, the minimum mass flow required to avoid the stratified flow in two parallel pipelines is studied, and the characteristics of different methods are compared.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM615

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