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压力管道中瞬变流准二维模型数值计算及应用研究

发布时间:2019-01-07 13:58
【摘要】:在热电厂或核电厂循环冷却水系统、城市供热和供水系统以及建筑内空调水系统等有压管道系统中,因阀门突然启闭或是水泵突然启停而导致管道中流速剧烈变化,常会引发水锤事故。传统水锤分析主要采用一维模型计算方法,该方法利用拟稳态摩阻模型近似计算管道瞬变流的摩阻耗散,因而无法准确模拟瞬变流的压力波衰减过程。准二维模型计算管道瞬时的二维速度场和一维压力场,并结合代数湍流模型计算瞬变流摩阻耗散,可以真实地反映瞬变流的压力波动,但现有求解方法因计算过程复杂仍无法在工程中广泛应用。因此,本文提出一维与准二维联合求解方法,该方法简化现有准二维模型计算方法的求解过程,同时可直接利用一维模型的分析策略,并与一维模型进行耦合求解,扩展准二维模型的应用范围并提高其计算效率。首先,分别阐述了一维特征线法和有限体积法,提出了改进的有限体积法,该方法的计算节点可以与特征线法的计算节点一一对应,同时验证了其准确性。基于理论分析,提出一维和准二维联合求解方法,分别建立了一维特征线法和改进的有限体积法与准二维模型联合求解的方法,并研究了这两种方法的准确性和高效性。结果表明,特征线法与准二维模型联合求解方法与现有准二维模型求解方法的计算精度相同,有限体积法与准二维模型联合求解方法的计算精度受粘性项权重系数的取值影响较大。在计算效率方面,本文所提出的计算方法比现有的准二维模型求解方法的计算效率更高,并且该方法可应用于一维交错网格。同时,提出修正的拟稳态摩阻模型。以文献中的实验数据为依据,比较分析了拟稳态摩阻模型、修正的拟稳态摩阻模型、改进的Brunone摩阻模型、Vardy-Brown摩阻模型和准二维模型的模拟结果。以准二维模型的模拟结果为依据,对修正的拟稳态摩阻模型中修正系数的选取规律进行了研究。其次,建立了基于准二维模型的离散蒸汽空穴模型和离散气体空穴模型,并以文献中的实验数据为依据,对比分析了拟稳态摩阻模型、改进的Brunone摩阻模型和准二维模型的离散蒸汽空穴模型和离散气体空穴模型的计算结果。结果表明,基于准二维模型的液柱分离模型相比一维模型的液柱分离模型的计算结果更准确,与文献中的实验结果更接近,可以准确地模拟气液两相瞬变流的压力波动过程。然后,基于事故停泵模型和压力罐模型,提出水泵-阀门-压力罐模型,并基于准二维模型的模拟结果,对传统一维模型模拟有压力罐防护的停泵水锤的准确性进行了研究。结果表明:准二维模型的压力波动的波峰和波谷值均小于一维模型的结果,并且准二维模型模拟得到的压力波动衰减速度更快。最后,基于上述准二维模型的模拟结果,利用序列二次规划法分别对三种不同连接结构的压力罐尺寸和参数进行了优化。结果表明,应用本文所绘制的最优罐体体积随管道允许最大压力和罐体连接结构参数的变化图,可简便直观地确定最优罐体体积和连接结构参数,并且在优化过程中应基于准二维模型的结果对一维模型进行修正,从而提高压力罐参数优化的准确性和适用性。本文提出一种基于一维模型与准二维模型联合求解瞬变流问题的计算方法,将该方法应用于校核一维摩阻模型、分析气液两相瞬变流流动过程、模拟事故停泵水锤及优化选择压力罐尺寸等方面,验证了该方法的准确性、高效性和适用性。本文的研究成果扩展了准二维模型的应用范围,进一步完善了瞬变流准二维模型的基本理论,对有压管道瞬变流分析具有指导意义,并为其用于实际工程的可行性提供了参考依据。
[Abstract]:In the pressure piping system, such as the circulating cooling water system of the thermal power plant or the nuclear power plant, the city heating and water supply system and the air-conditioning water system in the building, due to the sudden opening and closing of the valve or the sudden start and stop of the water pump, the flow rate in the pipeline can be changed dramatically, and the water hammer accident is often caused. The traditional water hammer analysis mainly adopts one-dimensional model calculation method, and the method uses the quasi-steady-state friction model to approximate the frictional resistance dissipation of the transient flow of the pipeline, so that the pressure wave attenuation process of the transient current can not be accurately simulated. A quasi-two-dimensional model is used to calculate the instantaneous two-dimensional velocity field and one-dimensional pressure field of the pipeline, and the transient flow friction dissipation is calculated in combination with the algebraic turbulence model, and the pressure fluctuation of the transient flow can be truly reflected, but the existing solution method can not be widely applied in the engineering due to the complex calculation process. In this paper, a one-dimensional and quasi-two-dimensional joint solution method is proposed, which simplifies the solution process of the existing quasi-two-dimensional model calculation method, and can directly utilize the analysis strategy of the one-dimensional model, and is coupled with the one-dimensional model to solve the problem. and the application range of the quasi-two-dimensional model is expanded and the calculation efficiency is improved. First, the one-dimensional characteristic line method and the finite volume method are described respectively, and the modified finite volume method is proposed. The calculation node of the method can be one-to-one correspondence with the calculation node of the characteristic line method, and the accuracy of the method is also verified. Based on the theory analysis, a two-dimensional and quasi-two-dimensional joint solution method is proposed, and the method of the one-dimensional feature line method and the improved finite volume method and the quasi-two-dimensional model are respectively established, and the accuracy and efficiency of the two methods are also studied. The results show that the method of the combination of the feature line method and the quasi-two-dimensional model is the same as that of the existing quasi-two-dimensional model, and the calculation accuracy of the finite volume method and the quasi-two-dimensional model is affected by the value of the weight coefficient of the viscous term. In terms of the computational efficiency, the computational efficiency proposed in this paper is higher than that of the existing quasi-two-dimensional model, and the method can be applied to a one-dimensional staggered grid. At the same time, a modified quasi-steady-state friction model is proposed. Based on the experimental data in the literature, the quasi-steady-state friction model, the modified quasi-steady-state friction model, the modified Brunone friction model, the Vardy-Brown friction model and the quasi-two-dimensional model are compared and analyzed. Based on the simulation results of the quasi-two-dimensional model, the selection of the correction coefficients in the modified quasi-steady-state friction model is studied. Secondly, a discrete vapor hole model and a discrete gas hole model based on the quasi-two-dimensional model are established, and the quasi-steady-state friction model is compared and analyzed based on the experimental data in the literature. The improved Brunone friction model and the quasi-two-dimensional model's discrete vapor hole model and the discrete gas hole model are calculated. The results show that the calculation results of the liquid-column separation model based on the quasi-two-dimensional model are more accurate than that of the one-dimensional model, and the pressure fluctuation process of the two-phase transient flow of the gas liquid can be accurately simulated. Then, based on the model of the accident stop pump and the model of the pressure tank, the model of the water pump-valve-pressure tank is put forward, and the accuracy of the water hammer of the stop pump with pressure tank protection is studied based on the simulation result of the quasi-two-dimensional model. The results show that the peak and trough values of the pressure fluctuation of the quasi-two-dimensional model are less than the results of the one-dimensional model, and the velocity of the pressure fluctuation obtained by the quasi-two-dimensional model is faster than that of the one-dimensional model. Finally, based on the simulation results of the quasi-two-dimensional model, the size and the parameters of the pressure tanks of the three different connecting structures are optimized by the sequence quadratic programming method. The results show that the optimal tank volume and the connection structure parameters can be determined simply and intuitively with the optimum tank volume as the pipeline allows the maximum pressure and the tank connection structure parameters to be changed. and the one-dimensional model can be modified based on the results of the quasi-two-dimensional model in the optimization process, so that the accuracy and the applicability of the pressure tank parameter optimization are improved. In this paper, a method for calculating the transient flow problem based on a one-dimensional model and a quasi-two-dimensional model is proposed, and the method is applied to the aspects of checking a one-dimensional model, analyzing the flow process of the two-phase transient flow of the gas liquid, simulating the water hammer of the accident stop pump and optimizing the size of the pressure tank, and the accuracy, the high efficiency and the applicability of the method are verified. In this paper, the application range of the quasi-two-dimensional model is extended, and the basic theory of the transient quasi-two-dimensional model is further improved.
【学位授予单位】:哈尔滨工业大学
【学位级别】:博士
【学位授予年份】:2017
【分类号】:TU991.3

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