Entropy and exergy analysis of steam passing through an inlet steam turbine control valve assembly using artificial neural networks

摘要

This paper describes the entropy and exergy analysis of an inlet steam turbine control valve assembly (1STCVA) and presents a novel concept of design guidelines on the selection of an appropriate ISTCVA at a thermal power plant. The ISTCVA is an important control and safety component of a steam turbine since it controls, through damping, the amount of vapour entering the steam turbine, whereby the inlet steam quality deteriorates, and entropy is generated. The generation of the entropy of the inlet steam passing through the ISTCVA cannot be avoided completely, but it can be reduced by decreasing the damping of the steam passing through the ISTCVA. To this end, we analysed the existing ISTCVA, comprising six control valves, and developed a new ISTCVA comprising 12 control valves. Using machine learning, we created a simulation model of entropy generation and exergy loss of the steam passing through the ISTCVA, consisting of the calculation units of both the existing and the new. The results show that the entropy generation and exergy loss of water vapour passing through the new ISTCVA is lower than in the existing ISTCVA. As a result, water vapour of a higher quality enters the steam turbine; the steam turbine produces more work; and its efficiency increases.