刷式密封的介质流动及刷丝尖端接触传热特性研究

发布时间：2018-05-22 08:33

本文选题：刷式密封 + 三维模型　；参考：《清华大学》2015年博士论文

【摘要】：由于优异的密封特性,刷式密封技术是提升航空发动机、地面及舰船燃气轮机等旋转机械性能的重要途径。刷丝尖端与转子的摩擦磨损及其发热问题是限制刷式密封应用的主要瓶颈。建立符合实际的数值模型,研究流场、刷丝尖端力和传热特性对提高刷式密封性能有重要意义。由于刷式密封结构和研究的复杂性,建立基本符合刷式密封结构和工作特点并加入必要简化的理论模型是研究的关键。本文建立了刷丝束截面的二维紧凑叉排管束模型,并在其基础上进一步发展了刷丝束的三维切片模型。基于刷丝束截面的二维紧凑叉排管束模型,探索了刷丝束间隙中介质的流动规律和刷式密封的密封机理。对比了周向单排与多排刷丝模型所计算的流场结果,压力计算结果与BayleyLong的转子表面压力测量结果基本吻合。研究了压差、刷丝轴向排数和管距对密封性能的影响。基于刷丝束的三维切片模型及刷丝束截面排列模型进一步研究了刷式密封的介质流动规律和密封机理。耦合CFD(计算流体力学)方法计算的气流力,采用矩平衡原理和线性叠加法提出了刷丝尖端力的计算理论,同时提出了基于ANSYS的刷丝尖端力的迭代算法。考虑刷丝尖端力、摩擦热及传热过程,建立了刷式密封的三维切片温度分析模型。计算结果得到了刷式密封的介质压力、流速、气流力、刷丝尖端摩擦力、摩擦热、温度分布特点。发现了理想接触的刷式密封中,刷丝受到的气流力、刷丝尖端力和摩擦热、温度在轴向上存在明显的非均匀性。ANSYS的仿真结果与理论计算的刷丝尖端力结果基本吻合。研究了刷丝轴向排数对泄漏率的影响,以及压差和转速对刷丝尖端温度的影响。在上述理论基础上,利用正交分析法研究了几何参数对单级刷式密封泄漏、气流力、刷丝尖端摩擦力、转矩的影响。研究了两级刷式密封的泄漏、气流力和刷丝尖端摩擦力特性。发现了上游级和下游级的压降、气流力和刷丝尖端摩擦力的级间不平衡性,并对级间不平衡性进行了优化设计。设计并搭建了刷式密封多功能实验测试系统,验证了泄漏率、转矩和温度的数值计算结果及相关计算模型和理论。提出了基于纤维热电偶测量刷丝束-转子摩擦区温度的新方法,具有对干涉和偏心工况更敏感,不会明显破坏原有的温度场等优点。
[Abstract]:Because of the excellent sealing characteristics, brush sealing technology is an important way to improve the rotating mechanical properties of aero-engine, ground gas turbine and ship gas turbine. The friction and wear between the tip of the brush wire and the rotor and its heating are the main bottlenecks restricting the application of the brush seal. It is very important to establish a numerical model to study the flow field, tip force and heat transfer characteristics to improve the performance of brush seal. Because of the complexity of the brush seal structure and research, it is the key to establish a theoretical model which basically accords with the brush seal structure and working characteristics and adds the necessary simplified theoretical model. In this paper, a two-dimensional compact forked bundle model for the cross section of the brush wire bundle is established, and the 3D slice model of the brush bundle is further developed on the basis of the model. Based on the two dimensional compact cross row bundle model of the brush wire beam section, the flow law of the medium in the gap of the brush wire bundle and the sealing mechanism of the brush seal are explored. The results of flow field calculated by circumferential single-row and multi-row brush wire models are compared. The results of pressure calculation are in good agreement with the measured results of BayleyLong rotor surface pressure. The effects of pressure difference, axial arrangement of brush wire and tube distance on sealing performance were studied. Based on the three dimensional slice model and the cross section arrangement model of brush wire bundle, the media flow law and sealing mechanism of brush seal are further studied. Coupled with the computational fluid dynamics (CFD) method, the calculation theory of the tip force of the brush wire is presented by using the moment balance principle and the linear superposition method, and the iterative algorithm of the tip force of the brush wire based on ANSYS is proposed. Considering the tip force, friction heat and heat transfer process of brush wire, a three dimensional slice temperature analysis model of brush seal was established. The characteristics of pressure, velocity, flow force, friction force at the tip of brush wire, friction heat and temperature distribution of brush seal are obtained. It is found that the airflow force, tip force, friction heat and temperature have obvious inhomogeneity in the ideal contact seal. The simulation results of ANSYS are in good agreement with the calculated results. The influence of axial row number on leakage rate and the influence of pressure difference and rotation speed on tip temperature of brush wire were studied. On the basis of the above theory, the effects of geometric parameters on the leakage of single stage brush seal, the air flow force, the friction force at the tip of the brush wire, and the torque are studied by orthogonal analysis. The characteristics of leakage, airflow force and tip friction of two-stage brush seal are studied. The imbalance between the upper stage and the downstream stage, the flow force and the friction force at the tip of the brush wire is found, and the imbalance between the stages is optimized. The multifunctional experimental test system of brush seal is designed and built to verify the numerical calculation results of leakage rate torque and temperature as well as the related calculation model and theory. A new method based on fiber thermocouple is proposed to measure the temperature of the friction zone of the brush wire-rotor, which is more sensitive to interference and eccentricity, and does not obviously destroy the original temperature field.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB42

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