基于速度滑移和温度阶跃的螺旋槽干气密封气膜流场研究

发布时间：2018-06-29 10:36

本文选题：干气密封 + 能量方程　；参考：《兰州理工大学》2014年硕士论文

【摘要】：螺旋槽干气密封被广泛应用于石化行业中,其稳定且可靠的的运行直接关系到石油化工企业的安全问题。近年来,在干气密封的密封性能方面有了更深入的研究,使干气密封的应用范围得到了极大的提高,从运行的低转速和低压力扩大到高转速和高压力。在介质压力和运转速度较高的工作状态下螺旋槽干气密封的密封端面间会产生较大的热量,从而使运行不稳定和泄漏量增大。本文通过引入螺旋槽干气密封气体流动的二阶速度滑移边界条件,对干气密封的密封端面间气膜的非线性动力学行为进行研究,求得干气密封中相应的动力学方程。同时引入温度阶跃边界条件并推导出气膜的能量微分方程。通过密封环的热弹变形理论和二阶非线性速度滑移边界条件来分析研究螺旋槽干气密封的密封性能,本文主要的研究内容和结论如下：在速度滑移边界条件下,求出螺旋槽干气密封密封端面间气膜的压力和速度,然后推导出气膜的无热耗散能量方程及有热耗散能量方程,进而利用气膜的压力、速度和能量方程,通过Maple和Matlab软件求解槽内气膜的温度分布。然后由气膜温度对密封环变形的影响,求出密封环的热变形量,从而求出干气密封密封端面间气膜的厚度。最后利用由雷诺方程推导出的泄漏量方程求得螺旋槽干气密封的理论泄漏量,并将理论泄漏量与实验测得的泄漏量作比较。研究结果表明：随着密封气体从密封环的外径流入内径,干气密封气膜的温度先升高,当气体到达槽根部附近时温度达到最高,然后再随着气体的继续流入气膜温度逐渐降低；密封环由温度引起的几何变形量与气膜温度的变化一致,然而密封端面间气膜厚度的分布与密封环的热弹变形量相反；随着密封环热弹变形量的增加,干气密封中的泄漏量也随之增大；考虑热弹变形下的泄漏量与实验测得泄漏量数值较接近；热耗散下考虑热弹变形的泄漏量最接近于实验值。根据速度滑移边界条件,求出气膜压力和气膜速度；然后推导出气膜的能量微分方程,同时引入温度阶跃边界条件,进而利用气膜的压力、速度和能量方程,通过Matlab软件数值计算得到三维坐标下气膜的温度分布。研究结果表明：随着气体从密封环外径流入内径,气膜速度的分布规律是先降低后升高,槽根部周围速度较低；随着密封气体从密封环的外径流入内径,干气密封气膜的温度先升高,当气体到达槽根部附近时温度达到最高,然后再随着气体的继续流入气膜温度逐渐降低,另外气膜厚度方向上气膜中间位置温度较高;考虑温度阶跃下的温度分布与不考虑温度阶跃下的温度分布相差较小,因此在对干气密封密封端面间气膜温度场研究时可以忽略温度阶跃对其的影响。在流体的二阶速度滑移边界条件下对雷诺方程进行推导,得出修正的广义雷诺方程,并通过PH线性化法和迭代法对修正型雷诺方程进行求解,从而推导出气膜的开启力方程。然后由气膜温度对密封环变形的影响,求出密封环的热弹变形量,从而得到干气密封密封端面间气膜的厚度。进而利用气膜刚度为开启力与气膜厚度之比求出气膜刚度。然后通过建立热弹变形下气膜刚度和气体泄漏量之间的协调函数,对刚漏比目标函数进行数值计算,从而对干气密封的螺旋角进行优化,得到特定工况下相对应的最优螺旋角。研究结果表明：随着密封气体从密封环的外径流入内径,干气密封的刚漏比先增大,当气体到达螺旋槽根部附近时达到最大值,随着气体的继续流入刚漏比减小；刚漏比随着螺旋角的变化成非线性趋势,在刚漏比最大时得到优化的最佳螺旋角。
[Abstract]:The spiral groove dry gas seal is widely used in the petrochemical industry. Its stable and reliable operation is directly related to the safety problem of petrochemical enterprises. In recent years, the sealing performance of dry gas seal has been studied more deeply, and the application range of dry gas seal has been greatly improved, from low running speed and low pressure. At high speed and high pressure, large heat is generated between the seal face of the spiral groove dry gas seal in the working state of high medium pressure and running speed, which makes the operation unstable and the leakage increase. In this paper, the seal end of dry gas seal is introduced by introducing the two order velocity slip boundary condition of the spiral groove dry gas seal gas flow. The nonlinear dynamic behavior of the air film is studied, and the corresponding dynamic equation in the dry gas seal is obtained. The temperature step boundary condition is introduced and the energy differential equation of the gas film is derived. The seal of the spiral groove dry gas seal is analyzed by the thermal elastic deformation theory of the seal ring and the two order nonlinear velocity slip boundary condition. The main contents and conclusions of this paper are as follows:
Under the velocity slip boundary condition, the pressure and velocity of the gas film between the seal face of the spiral groove dry gas seal are obtained. Then the heat dissipation energy equation and the heat dissipation equation are derived. Then the pressure, velocity and energy equation of the gas film are used to solve the temperature distribution of the gas film in the slot by Maple and Matlab software. Then the gas film is made by the gas film. The effect of temperature on the deformation of the seal ring is obtained. The thermal deformation of the seal ring is calculated, and the thickness of the gas film between the seal face of the dry gas seal is obtained. Finally, the leakage amount of the spiral groove dry gas seal is obtained by the leakage equation derived from Reynolds equation. The theoretical leakage is compared with the measured leakage. The results show that the leakage of the seal ring is compared with the measured leakage. As the airtight gas flows from the outer diameter of the seal ring into the inner diameter, the temperature of the dry gas seal gas film rises first, the temperature reaches the highest when the gas reaches the root of the trough, and then gradually decreases with the continuous flow of gas into the gas film temperature, and the geometric deformation caused by the temperature of the seal ring is consistent with the change of the gas film temperature, but the seal face is between the end face. The distribution of gas film thickness is the opposite of the thermal elastic deformation of the seal ring; with the increase of the thermal elastic deformation of the seal ring, the leakage amount in the dry gas seal increases, and the leakage of the thermal elastic deformation is close to the experimental result, and the leakage amount considering the thermal elastic deformation is closest to the experimental value under the heat dissipation.
According to the velocity slip boundary condition, the gas film pressure and gas film velocity are obtained. Then the energy differential equation of the gas film is derived. At the same time, the temperature step boundary condition is introduced. Then the pressure, velocity and energy equation of the gas film are used to calculate the temperature distribution of the gas film under the three-dimensional coordinates through the Matlab software. The results show that the temperature distribution of the gas film is obtained by the numerical calculation. When the gas flows from the outer diameter of the seal ring into the inner diameter, the distribution of gas film velocity is reduced first and then rising, and the velocity of the groove is low around the root. As the sealing gas flows from the outer diameter of the seal ring into the inner diameter, the temperature of the dry gas seal gas film rises first, and the temperature reaches the highest when the gas reaches the root of the trough, and then goes into the gas film as the gas continues to flow into the gas film. The temperature gradually decreases, and the temperature distribution in the gas film thickness is higher in the direction of the gas film thickness. Considering the temperature distribution under the temperature step, the difference between the temperature distribution and the temperature step is small. Therefore, the temperature step can be ignored when the temperature field is studied between the seal face of the dry gas seal.
The Reynolds equation is derived from the two order velocity slip boundary condition of the fluid, and the modified generalized Reynolds equation is obtained. The modified Reynolds equation is solved by PH linearization and iterative method, and the opening force equation of the gas film is derived. Then the effect of the gas film temperature on the seal ring deformation is obtained, and the thermal elastic deformation of the seal ring is obtained. The film stiffness between the air film stiffness and the film thickness is obtained by using the film stiffness as the ratio of the opening force to the gas film thickness. Then by establishing the coordination function between the film stiffness and the gas leakage, the numerical calculation of the stiffness leakage ratio objective function is carried out, thus the spiral angle of the dry gas seal is obtained. The results show that as the sealing gas flows from the outer diameter of the sealing ring into the inner diameter, the stiffness leakage ratio of the dry gas seal increases first, when the gas reaches the root of the spiral groove, the maximum value is reached, and the stiffness leakage ratio decreases with the continuous flow of the gas, and the stiffness leakage ratio changes with the spiral angle. The optimal helix angle is obtained when the maximum leakage ratio is the largest.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TH136

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