Analysis of Steam Turbine Casing for Static Loading Condition

摘要

Contact pressure analysis of turbine casing is very important in steam turbine which needs to be addressed for structural integrity. During operating condition steam turbine casings are subjected to very high pressure and temperature which results in stress and strain distribution. If the contact pressure is not achieved as per the standards then it leads to leakage of steam which causes explosion of casing. These effects are difficult to validate experimentally, since the setup is very costly. Therefore This event can be numerically simulated using Finite element Analysis techniques. In this work, the contact pressure analysis of steam turbine is validated by using the comparison of hand calculation and Finite element analysis results. The goal of this paper is to estimate the contact pressure so that there should not be any leak. Pretension in bolts are considered to achieve a firm contact between the casings. The three dimensional model of steam turbine casing were created using Hypermesh Software. The cad model created was meshed using Hypermesh Software by utilizing standard quality parameters. Boundry Condition were given on the Finite element model using Hypermesh. Contact pressure analysis were performed using Radioss Software as solver. During the last several years the primary changes to the design of steam turbines have focused on improving their efficiency, reliability and reducing operating costs. Siemens Power Generation, for example, has improved the overall efficiency and availability of its steam turbines by decreasing the steam flow energy losses in each of the steam turbines components. The steam turbine unit largely influences the efficiency and reliability of power stations. Any improvement in the design of steam turbine enables more efficient use of fuel and results in reduced cost. The high pressure steam at 5650 C and 156 bar pressure passes through the high pressure turbine. The exhaust steam from this section is returned to the boiler for reheating before being used. On leaving the boiler reheater, steam enters the intermediate pressure turbine at 5650 C and 40.2 bar pressure. From here the steam goes straight to the section of Low pressure Steam turbine expanding itself with increase in mass flow. From the intermediate pressure turbine, the steam continues its expansion in the three Low pressure turbines. The steam entering the turbine is at 3060 C and 6.32 bars. To get the most work out of the steam, the exhaust pressure is kept very low. The casing witness, energy of the steam turned into work in HP and IP-stages.