推进剂管路系统深低温垫片密封性能数值分析

Numerical analysis of the sealing performance of deep cryogenic gaskets in propellant pipeline systems

为解决运载火箭在常规和极端服役工况下的密封泄漏问题,该文提出一种可预测深低温接管系统接头连接密封性能的方法。首先借助有限元仿真方法分析求解接触界面力学的宏观接触压力分布;之后利用真实粗糙表面形貌,结合接触压力分布,计算微观接触形貌,进而求解泄漏通道的平均高度;考虑介质流动特性,采用栅格模型构建泄漏率量化计算模型,最终得到作为评判密封性能标准的泄漏率。基于数值计算方法,从理论上研究了不同温度、载荷和介质压力等参数对垫片密封性能的影响规律;同时通过简化接头-接管系统结构,设计了一种可重复使用且操作方便的模拟工装实验结构,进而开展了不同载荷下的垫片密封泄漏率测试,结果表明:泄漏率的仿真值和实验值误差在一个数量级内,吻合度较高。该研究对接头-接管垫片密封结构的设计优化及工程应用具有一定的指导意义。

[Objective]The single-shot arrow tube valve system has over a hundred locations where effective sealing is essential.Under extreme operating conditions,such as frequent alternation between deep low temperatures and ambient temperatures,pressure fluctuations within the pipes,and turbulent flow fields,the sealing surfaces are prone to contact deformation due to excessive localized stresses.Consequently,it becomes challenging to maintain an appropriate sealing contact pressure,rendering the conventional gasket sealing model inadequate and considerably reducing the sealing reliability.Furthermore,deep low temperatures can alter the flow characteristics of the sealing medium,altering its flow properties inside the microscopic leakage channels.Further,the mechanical properties of gasket sealing materials vary with temperature,resulting in leakage rates exceeding acceptable levels in low-temperature environments for step gasket structures that are deemed suitable for ambient temperatures.[Methods] To address the sealing leakage issue in carrier rockets during service under conventional and extreme conditions,a method for predicting the sealing performance of the deep low-temperature joint-connection system is proposed.First,finite element simulation software is used to analyze the Mises stress under different operating conditions and conduct interface mechanical analysis of the sealing contact areas to determine the macroscopic contact pressure of the sealing interface.Subsequently,a three-dimensional white light interferometer is used to study the sealing contact interface,and the obtained rough surface topography is converted into a digital representation by numerical methods.By combining the contact pressure distribution obtained from the simulation,the microcontact surface topography is determined using the fast Fourier transform algorithm,followed by the determination of the average height of the leakage channel.Considering the flow characteristics of the medium,a grid model is employed to construct a leakage rate quantifying model.Consequently,the leakage rate is established as the criterion for evaluating the sealing performance.[Results]The influence of different parameters,such as temperature,load,and medium pressure,on gasket sealing performance was studied through numerical calculation methods.As the temperature decreased,materials gradually harden,resulting in reduced compression of gaskets under the same load at 20 K.Additionally,joints and nozzle inlets experience structural dimensional changes caused by the temperature decrease,which was one of the reasons for increased leakage rates at deep cryogenic temperatures.When the load remained constant and the operating temperature was 20 K,the medium pressure did not significantly affect the overall trend of the contact pressure curve,but it had a notable impact on the regions subjected to medium-pressure loading.Simultaneously,by simplifying the joint-connection system structure,a reusable and convenient experimental fixture was designed for the measurement test of gasket sealing leakage rates under different loads.[Conclusions]The proposed numerical method comprehensively considers the influence of gasket mechanical properties,surface topography micro-parameters,medium pressure,and torque load on gasket sealing performance,introducing a approach using leakage rate as an evaluation metric.The results demonstrate that the simulated leakage rates are of the same order of magnitude as the experimental values,exhibiting a high level of agreement.This study provides valuable guidance for the optimization of joint-connection gasket sealing design and its practical applications.