Xiong Yangheng

Research of Temperature Characteristics of Non-Equilibrium Condensation in Transonic Steam Flow

The non-equilibrium phase transition model in CFX is used to simulate the non-equilibrium condensation flow in Laval nozzles. The Eulerian-Eulerian governing equation of multi-phase computational fluid dynamics model is utilized to solve the two-phase flow with k-e turbulence model. By simulating the spontaneous condensation flow in 2D and 3D models Laval nozzles with different geometries, non-equilibrium phase transition and condensation shock are captured. Our numerical results indicate that the pressure distributions and water droplet diameters are compared with the experimental ones under the same situation. It is shown that the results of 3D model agree with the experimental results better, while the pressure distribution curve of 2D model exhibits the “2D effect”, which may cause calculated errors. Finally, the temperature characteristics of non-equilibrium condensation in transonic steam flow are computed with 3D model and the influence of the inlet temperature on the condensation characteristics and position of shock wave is analyzed.© 2014 ASME

The Thermal State Numerical Simulation and the Security Analysis to the Superheaters of the Ultra-Supercritical Boiler in FCB

A successful FCB (Fast Cut Back) can increase the security of the power plant and electric grid. On the other hand, in ultra-supercritical boilers, the superheaters suffer higher temperature, higher stress and severer oxidation on steam side. In this article, a numerical simulation on the temperature and stress of the superheaters, considering the double oxide scale on steam side, respectively in the process of 100%, 50% FCB (Fast Cut Back) and 100%, 75%, 50% load shedding, is conducted. The change law of the operation state is discussed. The results show that the higher the load before the operation condition change is, the greater range temperature and stress of the scale changes in, and the stress of the scale is affected by the steam temperature and steam pressure at the same time. The highest equivalent strain appears on the interface of the double scale, and its value is close to the spalling value. The oxide scale on the steam side of superheaters has high potential risk of spalling, great attention should be paid to them.Copyright

Research and development of a high-quality thermal-stress online monitoring model for the 600 MW turbine

To monitor and control its thermal state, a rotor’s temperature and thermal stress fields must be calculated in real time. After some reasonable assumptions and simplification, iterative models of the rotor’s temperature and thermal stresses were obtained with an integral transform based on a two-dimensional axis-symmetry thermal conduction differential equation. The models can deal with some nonlinear factors such as material and boundary condition. An example is given to compare results computed by the finite element method (FEM) and one-dimensional models. The result shows that the analytical model gained has high quality and the computing course is very short. The iterative formulas could be used not only to analyze the rotor’s thermal states of turbine, but to monitor and control them online. The method adopted can be used to analyze the thermal state of other axis-symmetry objects having similar boundary conditions.