Abstract
In combined cycle power plants (CCPPs), the bypass butterfly valve is a key component to facilitate regulation of exhaust gas energy available at the turbine and to not produce too much boost pressure. The conventional damper valve causes leakage, back flow into the turbine, and damage of the blade, and the existing dual-layered seal with polytetrafluoroethylene (PTFE) and metal should be frequently replaced owing to its low durability and deterioration of mechanical properties under a high temperature. This study devised a triple offset butterfly valve with a new type of seal by alternatively laminating stainless steel and graphite to improve valve performance at the high temperature (350 °C). The slope angles of the seal contact surface to prevent friction were calculated using the mathematical models of the triple offset. Thermal-structure coupled analyses by varying the number of graphite and thickness were conducted, and the seven-layer model with the graphite thickness of 0.8 mm, which shows airtightness and smooth operation, was chosen. The contact stresses behaviors of the graphite at 350 °C and at −196 °C were investigated, and it was found that the graphite is in charge of improving driving performance of the disc at the high temperature and sealing performance at the cryogenic temperature. The performance tests and the field tests of the suggested model verified its performance at the working temperature.
Highlights
As global warming and the depletion of energy resources have intensified, the growth in worldwide energy demand currently faces the difficulty of installing new power generation facilities as a result of limited funding and the strengthening of environmental regulations
Combined cycle power plants (CCPPs), which consist of gas turbines and steam turbines, are becoming more important as the global demand for electrical power increases [1,2]
It is necessary to find an effective trade-off between needs for good operation and of the disc
Summary
As global warming and the depletion of energy resources have intensified, the growth in worldwide energy demand currently faces the difficulty of installing new power generation facilities as a result of limited funding and the strengthening of environmental regulations. In order to prevent the above problems, the bypass system facilitates the regulation of the exhaust gas energy available at the turbine wheel, and allows the turbocharger to be controlled and to not produce too much boost pressure. In this system, the bypass valve, which is mounted between the. As the values above which aerodynamic stalling at the rotor blades would produce a severe fall in power modern CCPPs require an increase of exhaust pressure in order to fulfill the restrictions of pollutant output [6,7,8].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
