烟气脱硫系统循环泵的气蚀机理及防治措施
发布时间：2018-08-02 08:53
【摘要】：循环泵是火电厂烟气脱硫系统中的关键设备,循环泵在运行中存在气蚀、腐蚀和磨损等问题,特别是气蚀形成的瞬时高压对循环泵的冲击非常大,是循环泵的主要破坏形式。本文通过对壁面附近的单空泡溃灭动力学过程的数值模拟,探讨循环泵气蚀问题的防治措施。由于浆液成份的复杂性,本文用水代替浆液进行模拟,并考虑水蒸气粘度随温度和压力变化(简称为非定常粘度)对计算模型进行了优化,得到了不同流场背景压力下空泡溃灭过程各特征参数的变化情况,并分析微射流及溃灭最大压力的相关影响因素。本文还模拟了水蒸气-空气混合空泡的近壁面溃灭过程,得到了不同含气量下混合空泡溃灭过程的相关特征参数。模拟结果表明:非定常粘度的水蒸气空泡溃灭过程与定常(μ=constant)粘度的空泡溃灭过程大致相同,在流场背景压力为0.1~0.6MPa的情况下,非定常粘度的水蒸气空泡溃灭过程均比粘度为常数的水蒸气空泡溃灭过程的对称性好,溃灭过程形态变化较为接近;非定常粘度的水蒸气空泡溃灭过程产生的射流速度均低于定常粘度的水蒸气空泡,而溃灭最大压力则相反;射流产生的水击压力对壁面的影响小于空泡溃灭最大压力;混合空泡射流速度与空气含量关系不明显;混合空泡的溃灭最大压力随空气含量的变化曲线近似为抛物线,在空气含量为0.5时达到最高,在2100MPa左右。通过模拟分析,提出了循环泵气蚀问题的防治措施:控制再氧化空气的通入量、增加浆液的空气溶解能力和调整浆液层的压力。吸收塔底部再氧化空气的通入量,应综合考虑循环泵的最大流量及运行负荷情况。增加浆液对空气的溶解度可以降低空气总量和空泡中空气含量,且改善浆液的抗空化的能力。
[Abstract]:Circulating pump is the key equipment in flue gas desulfurization system in thermal power plant. There are some problems such as cavitation, corrosion and wear in operation of circulating pump, especially the impact of instantaneous high pressure formed by cavitation on circulating pump is very big, which is the main failure form of circulating pump. Based on the numerical simulation of the dynamic process of single cavitation collapse near the wall, this paper discusses the prevention and cure measures of the cavitation problem of the circulating pump. Because of the complexity of the composition of the slurry, the model is optimized by using water instead of the slurry, and considering the variation of the water vapor viscosity with temperature and pressure (referred to as unsteady viscosity). The variation of characteristic parameters of cavitation collapse process under different background pressure of flow field is obtained, and the influence factors of micro-jet and maximum collapse pressure are analyzed. In this paper, the near wall collapse process of water vapor air mixed cavitation is simulated, and the relevant characteristic parameters of the mixed cavitation collapse process with different gas content are obtained. The simulation results show that the process of vapor bubble collapse with unsteady viscosity is approximately the same as that with constant viscosity, and the flow field background pressure is 0.1~0.6MPa. The process of vapor bubble collapse with unsteady viscosity is more symmetrical than that with constant viscosity, and the morphological changes of the collapse process are close to each other. The velocity of water vapor bubble collapsing with unsteady viscosity is lower than that of water vapor bubble with constant viscosity, but the maximum pressure of collapse is opposite, the influence of water hammer pressure generated by jet on the wall is less than the maximum pressure of bubble collapse. The relationship between the velocity of mixed cavitation jet and air content is not obvious, and the curve of maximum collapse pressure with air content is approximately parabola, reaching the highest at 0.5 air content, about 2100MPa. Through simulation and analysis, the measures to prevent cavitation erosion of circulating pump are put forward: controlling the flux of reoxidized air, increasing the air dissolution capacity of slurry and adjusting the pressure of slurry layer. The maximum flow rate and operating load of the circulating pump should be taken into account when reoxidizing the air at the bottom of the absorber. Increasing the solubility of slurry to air can reduce the total air content and the air content in cavitation and improve the anti-cavitation ability of the slurry.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
本文编号：2158898
[Abstract]:Circulating pump is the key equipment in flue gas desulfurization system in thermal power plant. There are some problems such as cavitation, corrosion and wear in operation of circulating pump, especially the impact of instantaneous high pressure formed by cavitation on circulating pump is very big, which is the main failure form of circulating pump. Based on the numerical simulation of the dynamic process of single cavitation collapse near the wall, this paper discusses the prevention and cure measures of the cavitation problem of the circulating pump. Because of the complexity of the composition of the slurry, the model is optimized by using water instead of the slurry, and considering the variation of the water vapor viscosity with temperature and pressure (referred to as unsteady viscosity). The variation of characteristic parameters of cavitation collapse process under different background pressure of flow field is obtained, and the influence factors of micro-jet and maximum collapse pressure are analyzed. In this paper, the near wall collapse process of water vapor air mixed cavitation is simulated, and the relevant characteristic parameters of the mixed cavitation collapse process with different gas content are obtained. The simulation results show that the process of vapor bubble collapse with unsteady viscosity is approximately the same as that with constant viscosity, and the flow field background pressure is 0.1~0.6MPa. The process of vapor bubble collapse with unsteady viscosity is more symmetrical than that with constant viscosity, and the morphological changes of the collapse process are close to each other. The velocity of water vapor bubble collapsing with unsteady viscosity is lower than that of water vapor bubble with constant viscosity, but the maximum pressure of collapse is opposite, the influence of water hammer pressure generated by jet on the wall is less than the maximum pressure of bubble collapse. The relationship between the velocity of mixed cavitation jet and air content is not obvious, and the curve of maximum collapse pressure with air content is approximately parabola, reaching the highest at 0.5 air content, about 2100MPa. Through simulation and analysis, the measures to prevent cavitation erosion of circulating pump are put forward: controlling the flux of reoxidized air, increasing the air dissolution capacity of slurry and adjusting the pressure of slurry layer. The maximum flow rate and operating load of the circulating pump should be taken into account when reoxidizing the air at the bottom of the absorber. Increasing the solubility of slurry to air can reduce the total air content and the air content in cavitation and improve the anti-cavitation ability of the slurry.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
【参考文献】
相关期刊论文 前2条
1 李疆;陈皓生;;Fluent环境中近壁面微空泡溃灭的仿真计算[J];摩擦学学报;2008年04期
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，本文编号：2158898
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