International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In this paper is performed exergy and isentropic analysis of a helium closed-cycle gas turbine plant and all its main components. In the real operating conditions, turbine produces mechanical power equal to 546.27 MW, turbocompressor consumes mechanical power of 268.74 MW and the useful mechanical power delivered for the electric generator drive is equal to 277.53 MW. The highest possible mechanical power which can theoretically be delivered for the electrical generator drive (ideal useful mechanical power) is equal to 351.89 MW. Helium gas turbine is the component in the observed plant which has the lowest exergy destruction (9.40 MW) and the highest exergy efficiency (98.31%) of all components. Precooler has the lowest exergy efficiency of all plant components, equal to 47.66% only. Due to the usage of cooling water, precooler exergy parameters are highly sensitive to the ambient temperature change. Whole analyzed plant has exergy destruction of 261.79 MW and exergy efficiency of 48.69%, what is in the same range as for the comparable closed-cycle gas turbine plants.

This paper presents exergy analysis results of a complex three cylinder steam turbine with nominal power 210 MW. The analysis is performed for each cylinder, cylinder part and whole turbine as well as for each segment of each turbine cylinder. In the observed turbine, Low Pressure Cylinder (LPC) has the highest exergy destruction (8668.15 kW) and the lowest exergy efficiency (87.19%), while Intermediate Pressure Cylinder (IPC) has the highest exergy efficiency (92.15%) of all cylinders. Exergy efficiency is the highest for each segment at each cylinder entrance and continuously decreases for all segments during steam expansion through each cylinder. In each cylinder, a segment which is the lowest influenced by the ambient temperature change is inlet segment – as steam expands through each cylinder, further segments became more and more influenced by the ambient temperature change. Steam re-heating process has a very beneficial influence on the exergy efficiency of the first two IPC segments (Seg. 3 and Seg. 4) which have the highest exergy efficiency in comparison to all other segments.

In this paper are presented results of a low-pressure steam turbine energy and exergy analysis during turbine extractions opening/closing. All possible combinations of extractions opening/closing are observed. The highest mechanical power which can be produced by this turbine (when all steam extractions are closed) is 28017.48 kW in real and 31988.20 kW in an ideal situation. For all observed steam extractions opening/closing combinations is obtained that energy efficiency and energy losses range is relatively small (from 87.56% to 87.94% for energy efficiency and from 3360.46 kW to 3970.72 kW for energy losses). Trends in energy and exergy losses (destructions) are identical for all observed extractions opening/closing combinations. Analyzed turbine efficiencies (both energy and exergy) will decrease for a maximum 1% during the steam extractions closing. Turbine steam extractions closing decrease turbine efficiencies and increases turbine losses (destructions), what is valid from both energy and exergy aspects.