Inner Surface Of Nozzle Research Articles

Modeling the airflow field of vortex spinning

Vortex spinning technology adopts a high-speed swirling airflow to rotate the fibers with open-ends to form yarn with real twists. The airflow behavior within the nozzle has a great effect on the yarn-formation process. In this study, a three-dimensional calculation nozzle model and corresponding three-dimensional airflow region model were established to enable the numerical calculation; airflow behavior—pressure, velocity, and the turbulent airflow field, and the streamline of airflow—was investigated in the presence of fiber bundles within the vortex spinning nozzle. Hybrid hexahedral/tetrahedral control volumes were utilized to mesh the grids in the calculation region. To consider airflow diffusion and convection in the nozzle, the Realizable k- ε turbulence model with wall function was adopted to conduct the calculation. Dynamic and static pressure values were obtained by numerical analysis to predict the action of the inner surface of nozzle and the wall resistance on the high-speed swirling airflow. The numerical simulation of dynamic airflow behavior can generate great insight into the details of airflow behavior and its distribution characteristics, and is helpful for understanding the spinning mechanism and promoting optimization of the spinning process.

Pose measurement of nozzle based on laser range finders for capturing satellite

Sensors system is considered as one of the most indispensable devices to the mission of capturing a satellite for on-orbit servicing in the space. In this paper, in order to measure the pose of nozzle, six laser range finders are installed in the capturing nozzle device for entering into and capturing nozzle, and a Geometric Axis Approximation (GAA) method is proposed to estimate the pose of satellite nozzle. Six laser range finders are arranged in the configuration of emission radiated at two planes of top and bottom. The pose measurement system is composed of the six laser range finders, applicable for real-time measurement of the ranges from inner surface of nozzle. Based on the properties of nozzle shape and finders arrangement, the GAA method is used to estimate the pose of nozzle by a connecting line between two centers of circles in the top and bottom planes. In the pose estimation of GAA method, solving the nonlinear transcendental equations can be avoided and a simple explicit model is built. Therefore, the GAA method is suitable for real time measurement. In this paper, the theoretical error of GAA method is analyzed, and in the capturing nozzle experiment system, the experiments of pose measurement are carried out. The results of experiments prove the efficiency of GAA method in pose estimation to nozzle based on laser range finders.

Residual stress reduction in the penetration nozzle weld joint by overlay welding

Stress corrosion cracking (SCC) in the penetration nozzle weld joint endangers the structural reliability of pressure vessels in nuclear and chemical industries. How to decrease the residual stress is very critical to ensure the structure integrity. In this paper, a new method, which uses overlay welding on the inner surface of nozzle, is proposed to decrease the residual stresses in the penetration joint. Finite element simulation is used to study the change of weld residual stresses before and after overlay welding. It reveals that this method can mainly decrease the residual stress in the weld root. Before overlay welding, large tensile residual stresses are generated in the weld root. After overlay weld, the tensile hoop stress in weld root has been decreased about 45%, and the radial stress has been decreased to compressive stress, which is helpful to decrease the susceptibility to SCC. With the increase of overlay welding length, the residual stress in weld root has been greatly decreased, and thus the long overlay welding is proposed in the actual welding. It also finds that this method is more suitable for thin nozzle rather than thick nozzle.