Zhicheng Deng

Reliability and Availability Prediction of Main Stop Valve and Control Valve Systems of Steam Turbines

A method for the reliability and the availability prediction of main stop valve and control valve systems of steam turbines is presented. The calculation models for the reliability and the availability of series, parallel and series-parallel systems of main stop valves and control valves are introduced. The reliability block diagrams, the availability block diagrams, formulas for the reliability prediction and the availability prediction of systems with 2 main stop valves and 2 control valves, 2 main stop valves and 4 control valves, 2 main stop valves and 6 control valves, 4 main stop valves and 4 control valves are given together with some examples. The mathematical model for the reliability and the availability prediction method of main stop valve and control valve systems of steam turbine is simple and the physical meaning is definite. The reliability and availability of main stop valve and control valve systems can be quantitatively already calculated and improved during the design stage. A basis is thus provided for the reliability and the availability design of main stop valve and control valve systems of steam turbines.Copyright

Heat transfer coefficient of wheel rim of large capacity steam turbines

A way of calculating the overall equivalent heat transfer coefficient of wheel rims of large capacity steam turbines is presented. The method and formula to calculate the mean forced convection heat-transfer coefficient of the surface of the blade and for the bottom wall of the blade passage, are introduced. The heat transmission from the blade to the rim was simplified by analogy to heat transmission in the fins. A fin heat transfer model was then used to calculate the equivalent heat transfer coefficient of the blade passage. The overall equivalent heat transfer coefficient of the wheel rim was then calculated using a cylindrical surface model. A practical calculation example was presented. The proposed method helps determine the heat transfer boundary conditions in finite element analyses of temperature and thermal stress fields of steam turbine rotors.

Study on Reliability Design Technology of Steam Turbine Blades

A reliability design method of steam turbine blades is presented. The method considers static stresses, dynamic stresses, endurance strength, safety ratios, vibration frequencies and excition force frequencies of blades as random variables. The strength and vibration design reliability of turbine blades is determined with the help of probabilistic design method. Some reliability calculation formulas are given together with some practical examples. With the reliability design method for steam turbine blades as given in this paper, the design reliability of steam turbian blades can be determined in the design stage. The method may provide some scientific basis for reliability design of steam turbine blades.Copyright