【作者】 王涛；

【导师】 王宇钢； 徐茁；

【作者基本信息】 辽宁工业大学 ， 机械工程， 2025， 硕士

【摘要】 真空系统作为真空炉的核心组成部分,对其抽气性能进行预测是真空系统设计的重要内容。精准的抽气性能预测对于优化系统设计、降低生产成本具有重要意义。然而,实际工程应用中,抽气性能预测结果往往与实际情况存在较大偏差。偏差产生的主要原因在于:异型管路元件流导难以准确计算;真空系统抽气性能预测的计算流程较为复杂繁琐,导致实际生产中技术人员多依赖工程经验进行粗略预测。为实现异型管路元件流导的准确计算和真空系统抽气性能的准确预测,本文展开以下研究:(1)以包含异型管路元件的真空系统为研究对象,首先,对不同抽气过程的真空度和流态进行了划分和明确。然后,基于规则管道流导计算方法,推导了非等径连接管道的等效直径计算公式。并基于真空抽气过程平衡方程和流导理论,分析了不同抽气过程中流导与有效抽速的关系,计算了考虑异型管路元件流导的真空泵有效抽速。最后,在此基础上,建立了低、高真空抽气过程性能计算的数学模型。这些内容为后续章节中关于异型管路元件流导的数值模拟及抽气性能预测的实现奠定了坚实的理论基础。(2)针对低真空抽气管路中的挡板阀,提出了一种基于RANS和NS方程的流导数值模拟方法。首先,构建包含真空室、规则管道和挡板阀的动态流导测定模型,采用Fluent瞬态求解器模拟低真空抽气过程,实现挡板阀在不同压力状态下的流场模拟。然后,基于模拟得到的流场,发现流导随流态变化规律:挡板阀内气体在湍流和层流阶段的流动特性呈现显著差异。在湍流阶段,流导受限于漩涡引发的能量耗散;在层流阶段,受限于截面收缩效应导致的局部阻力。最后,通过监测挡板阀进出口压力与流率值计算不同压力状态下的流导值,并依据此结果拟合归纳挡板阀的流导计算公式,为真空系统抽气性能预测提供数据支持。同时,分析不同挡板阀流导曲线发现:挡板阀的流导值随气体压力的变化而显著变化,且公称直径对其流导值有重要影响。验证实验表明,流导模拟值与理论值吻合良好,二者平均相对偏差为4.45%,从而验证了本章模拟方法的准确性和适用性,为低真空抽气管路中的异型管路元件流导计算提供方法上的参考。(3)针对高真空抽气管路中的捕集器,提出了一种基于TPMC法的流导数值模拟方法。首先,构建捕集器模型,采用Mol Flow+软件对气体分子在捕集器中的传输过程进行模拟。然后,基于模拟得到的压力云图,分析了挡板类型和夹角对捕集器的流导值和冷凝捕集效率的影响规律。最后,基于入、出口平面压力曲线,计算了捕集器在分子流下的流导值和传输几率,为真空系统抽气性能预测提供数据支持。同时,通过分析不同结构类型捕集器的压力分布和流导值发现:挡板类型和夹角对其流导值和冷凝捕集效率有显著影响,人字型捕集器在冷凝捕集效率上表现更优,而百叶窗型捕集器在流导值上具有更高的性能,且挡板夹角的增大有助于提升流导值和冷凝捕集效率。验证实验表明,比流导和传输几率的模拟值与文献参考值相对偏差分别为0.4%和1.29%。从而验证了本章模拟方法的准确性和适用性,为高真空抽气管路中的异型管路元件流导计算提供方法上的参考。(4)针对依赖工程经验进行抽气性能预测的方法偏差较大,且抽气性能预测的理论计算流程较为复杂繁琐的问题,提出了一种考虑异型管路元件流导的真空系统抽气性能预测方法。首先,基于前文对真空系统抽气过程的理论分析,建立了低、高真空抽气过程的抽气性能预测方法,并形成计算流程。然后,依照计算流程进行程序编写,同时开发了真空系统抽气性能预测软件。通过人机交互的可视化界面,可输入相关参数并自动计算出抽气时间、极限真空度、管路流导以及有效抽速等参数。最后,通过实例运行验证了软件代码的正确性。并将软件预测结果与真空抽气实验结果进行对比,发现不同抽气阶段预测值和实验值相对误差最大为6.46%。这表明本文预测方法具有准确性和实用性,可为真空系统设计提供参考。更多还原

【Abstract】 Vacuum system as the core component of vacuum furnace,its pumping performance prediction is an important part of vacuum system design.Accurate pumping performance prediction is of great significance for optimizing system design and reducing production cost.However,in actual engineering applications,the pumping performance prediction results often have a large deviation from the actual situation.The main reasons for the deviation are:it is difficult to accurately calculate the flow conductance of the shaped piping components;the calculation process of the vacuum system pumping performance prediction is complicated and cumbersome,which leads to the rough prediction of the technicians in the actual production relying on engineering experience.In order to realize the accurate calculation of the flow conductance of the shaped piping elements and the accurate prediction of the pumping performance of the vacuum system,the following studies are carried out in this paper:(1)Taking the vacuum system containing shaped piping elements as the research object,firstly,the vacuum degree and flow state of different pumping processes are divided and clarified.Then,based on the regular pipe flow conduction calculation method,the equivalent diameter calculation formula of non-equal diameter connected pipes is deduced.And based on the equilibrium equation of vacuum pumping process and the theory of flow conduction,the relationship between flow conduction and effective pumping speed in different pumping processes is analyzed,and the effective pumping speed of vacuum pump considering the flow conduction of shaped piping elements is calculated.Finally,on this basis,a mathematical model for the performance calculation of low and high vacuum pumping process was established.These contents lay a solid theoretical foundation for the realization of numerical simulation and pumping performance prediction of the flow conduction of shaped piping elements in the subsequent chapters.(2)A numerical simulation method of flow conduction based on RANS and NS equations is proposed for the baffle valve in low vacuum pumping pipeline.Firstly,a dynamic flow conduction measurement model containing vacuum chamber,regular pipe and baffle valve is constructed,and Fluent transient solver is used to simulate the low vacuum pumping process,so as to achieve the simulation of the flow field of the baffle valve under different pressure states.Then,based on the simulated flow field,it was found that the flow conductance changes with the flow pattern:the flow characteristics of the gas in the baffle valve in the turbulent and laminar flow stages show significant differences.In the turbulent stage,the flow conductance is limited by the energy dissipation caused by the vortex;in the laminar stage,it is limited by the local resistance caused by the cross-section contraction effect.Finally,the flow conductance values under different pressure conditions are calculated by monitoring the inlet and outlet pressures of the baffle valve and the values of flow rate,and the flow conductance formula of the baffle valve is fitted according to the results to provide data support for the prediction of the pumping performance of the vacuum system.At the same time,the analysis of the flow conductance curves of different baffle valves reveals that the flow conductance values of baffle valves change significantly with the change of gas pressure,and the nominal diameter has an important influence on the flow conductance values.The validation experiments show that the simulated values of the flow conductance match well with the theoretical values,and the average relative deviation of the two is 4.45%,which verifies the accuracy and applicability of the simulation method in this chapter,and provides methodological references for the calculation of the flow conductance of the profiled piping components in the low-vacuum pumping pipeline.(3)A numerical simulation method of flow conduction based on the TPMC method is proposed for the trap in a high vacuum pumping line.Firstly,the trap model is constructed and the transport process of gas molecules in the trap is simulated using Mol Flow+software.Then,based on the pressure cloud obtained from the simulation,the influence laws of baffle type and clamp angle on the flow conductance value and condensation trapping efficiency of the trap were analysed.Finally,based on the inlet and outlet plane pressure curves,the flow conductance values and transport chances of the trap under molecular flow were calculated to provide data support for the prediction of vacuum system pumping performance.Meanwhile,by analysing the pressure distributions and flow conductance values of traps of different structural types,it is found that the baffle type and the clamp angle have a significant effect on the flow conductance value and condensation trapping efficiency,and the herringbone-type trap performs better in condensation trapping efficiency,while the louver-type trap has a higher performance in flow conductance value,and the increase of the baffle angle can help to enhance the flow conductance value and condensation trapping efficiency.The validation experiments show that the relative deviations of the simulated values of specific flow conductance and transport chance from the literature reference values are 0.4%and 1.29%,respectively.Thus,the accuracy and applicability of the simulation method in this chapter are verified to provide methodological references for the calculation of the flow conductance of shaped piping elements in high vacuum pumping lines.(4)Addressing the issues of significant deviations in methods relying on engineering experience for vacuum performance prediction and the complex and cumbersome theoretical calculation process for such predictions,this paper proposes a method for predicting the vacuum performance of vacuum systems that takes into account the flow conductance of non-standard piping components.First,based on the theoretical analysis of the vacuum system pumping process discussed earlier,a method for predicting pumping performance during low-and high-vacuum pumping processes was established,along with a computational workflow.Subsequently,a programme was developed according to the workflow,and a software tool for predicting vacuum system pumping performance was created.Through a user-friendly visual interface,relevant parameters can be input,and the software automatically calculates parameters such as pumping time,ultimate vacuum level,pipeline conductance,and effective pumping rate.Finally,the correctness of the software code was verified through example runs.The software prediction results were compared with the vacuum pumping experiment results,and it was found that the maximum relative error between the predicted values and experimental values at different pumping stages was 6.46%.This indicates that the prediction method proposed in this paper is accurate and practical,and can provide a reference for the design of vacuum systems.更多还原