Advancing sustainable thermal power plants: A thermodynamic-based condition monitoring model for control valves in gas turbines under thermal fluctuations

Abstract

Precise monitoring of control valve performance is essential for regulating combustion outlet temperature, minimising nitrogen oxides emissions, and maintaining stable combustion in natural gas turbines. This study examines the temperature variations of a natural gas flow control valve, taking into account changes in valve stem position and cross-sectional area within a gas turbine power plant. A unique model is introduced to regulate valve area variation and assess performance based on the correlation between upstream and downstream temperatures. The model elucidates the impact of fluctuations in the valve cross-sectional area on the downstream natural gas temperature, taking into account upstream temperature variations between 285.15 K and 305.15 K. The Joule-Thomson coefficient is obtained from thermodynamic equations by the AGA8-92DC numerical approach. The gas composition, inversion characteristics, upstream and downstream temperature differentials, and the temperature gradient relative to the valve cross-sectional area were computed for two samples of natural gas and pure methane. The results demonstrate the differences in upstream and downstream temperatures at two pressure levels (2 MPa and 5.4 MPa). The comprehension of the temperature differential between the upstream and downstream areas can act as a crucial metric for condition monitoring and assessing the efficacy of fuel injection in control valves.