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

In this paper are presented isentropic analysis results of a steam turbine, their cylinders and cylinder parts which nominal power is equal to 250 MW. The analyzed steam turbine is a complex three-cylinder turbine which operates in a CCPP (Combined Cycle Power Plant). Considering all cylinders, the dominant mechanical power producer in the observed turbine is LPC (Low Pressure Cylinder) which produces 111.80 MW of mechanical power in real (polytropic) steam expansion process (almost half of the real mechanical power produced in the whole turbine). Developed mechanical power in turbine cylinders and isentropic losses are directly proportional – higher produced mechanical power will result in higher isentropic losses and vice versa. Whole analyzed steam turbine, their cylinders and cylinder parts how very good isentropic performance and high isentropic efficiencies of around 90%. The isentropic performance of the whole analyzed steam turbine, their cylinders and cylinder parts is in the range of the steam turbines (and their cylinders) from supercritical and ultrasupercritical power plants which are proven to be the best steam turbines from isentropic point of view.

This paper presents energy and exergy analysis results of whole gas turbine set and all its components. From the energy viewpoint, combustion chamber has the lowest energy loss (21.31 MW) and the highest energy efficiency (97.20%) of all gas turbine set components. Exergy analysis shows totally opposite trend in comparison to the energy analysis. From the exergy viewpoint, turbocompressor and turbine have low exergy destruction (both around 12 MW) and very high exergy efficiencies (92.43% for turbocompressor and 96.12% for turbine) at the base ambient state. Simultaneously, at the base ambient state combustion chamber has an exergy destruction of 159 MW and low exergy efficiency of 73.29% only. The combustion chamber is the most sensitive to the ambient temperature change of all components from the gas turbine set – the ambient temperature change of 10 °C will result with combustion chamber exergy efficiency change of approximately 0.67%. Whole gas turbine set (plant) has an energy efficiency of 34.40% and exergy efficiency of 33.08%.

In this paper are presented isentropic analysis results of a steam turbine, their cylinders and cylinder parts which nominal power is equal to 250 MW. The analyzed steam turbine is a complex three-cylinder turbine which operates in a CCPP (Combined Cycle Power Plant). Considering all cylinders, the dominant mechanical power producer in the observed turbine is LPC (Low Pressure Cylinder) which produces 111.80 MW of mechanical power in real (polytropic) steam expansion process (almost half of the real mechanical power produced in the whole turbine). Developed mechanical power in turbine cylinders and isentropic losses are directly proportional – higher produced mechanical power will result in higher isentropic losses and vice versa. Whole analyzed steam turbine, their cylinders and cylinder parts show very good isentropic performance and high isentropic efficiencies of around 90%. The isentropic performance of the whole analyzed steam turbine, their cylinders and cylinder parts is in the range of the steam turbines (and their cylinders) from supercritical and ultrasupercritical power plants which are proven to be the best steam turbines from isentropic point of view.

This paper presents an exergy analysis of six pressure reduction valves which operate in a condensate/feedwater heating system of a 660 MW coal-fired steam power plant. For all observed pressure reduction valves is additionally investigated the ambient temperature change influence of their exergy parameters. Second pressure reduction valve (PRV2) has the highest exergy destruction of all observed valves (equal to 1003.36 kW at the base ambient state). The first five observed pressure reduction valves (from PRV1 to PRV5) have very high exergy efficiencies at the base ambient state, higher than 90%. The last observed valve, PRV6, has an exergy efficiency at the base ambient state notably lower in comparison to other five valves, equal to 64.90% only. The exergy variables of any pressure reduction valve are more and more influenced by the ambient temperature change when the operating parameters of working fluid which flows through the valve (fluid pressure and temperature) are closer to the ambient state.

Exergy analysis of three cylinder steam turbine segments is performed in this research. The highest mechanical power of 47389.66 kW is developed in the first segment (Seg. I, which actually represents the entire HPC – High Pressure Cylinder). Intermediate Pressure Cylinder (IPC) is the dominant mechanical power producer of all cylinders and it develops 48.95% of cumulative mechanical power produced in the whole turbine. The outlet Low Pressure Cylinder (LPC) segments (Seg. VII and IX) have the highest exergy destructions and the lowest exergy efficiency (equal to 61.27%) of all turbine segments. The best exergy performance shows IPC segments – Seg. V has the lowest exergy destruction (equal to 363.84 kW), while Seg. II has the highest exergy efficiency (equal to 94.04%) of all turbine segments. Outlet LPC segments (Seg. VII and IX) are the most sensitive to the ambient temperature change – their exergy efficiency decreases for 3.19% when the ambient temperature increases from 5 °C to 45 °C.

In the presented paper are performed energy and exergy analyses as well as a comparison of two similar steam turbines from conventional power plants. The first turbine is from an older, while the second turbine is from newer steam power plant. The dominant mechanical power producer in an older steam turbine is LPC (which produces mechanical power of almost 66 MW), while in a newer steam turbine the dominant mechanical power producer is IPC which produces power equal to 102.4 MW. Whole older steam turbine has higher energy and exergy loss in comparison to the whole newer steam turbine. Whole turbine from the newer power plant has much higher energy and exergy efficiencies in comparison to whole turbine from an older power plant. In an older steam turbine, LPC did not show the expected performance because its exergy efficiency is very low (equal to 75.49%), what is much lower than in any other cylinder from both observed turbines. The ambient temperature change sensitivity of the two observed steam turbines and their cylinders is reverse proportional to efficiencies (both energy and exergy). Steam turbine from an older power plant is much more sensitive to the ambient temperature change.

In this paper are presented results of the energy and exergy analyses related to the steam generator from nuclear power plant at four observed operating regimes. It is shown how the optimization processes and algorithms influence observed steam generator operation. The highest steam generator energy outlet is equal to 3012.17 MW and the lowest energy loss is 0.07 MW – both of them are obtained by using Genetic Algorithm (GA). Whale Optimization Algorithm (WOA) gives fluid operating parameters which will result with the lowest steam generator exergy destruction (107.05 MW) and the highest exergy efficiency (92.709%) in comparison to all other operating regimes. During the increase in ambient temperature from 5 °C up to 45 °C the lowest decrease in steam generator exergy efficiency (equal to 2.0136%) is obtained in the second operating regime which operating parameters are defined by using WOA. Final conclusion which can be derived from the observed research is that WOA has the most beneficial influence on the steam generator operation.

This paper presents results of the Main Feedwater Pump (MFP) isentropic and exergy analyses at three power plant loads. Observed MFP is a constituent component of condensate/feedwater sub-system from conventional steam power plant. In real exploitation conditions, MFP uses mechanical power higher than 3000 kW, considering all observed power plant loads. Main isentropic and exergy parameters of the MFP at various plant loads show the same general trends (increase in power plant load simultaneously increases MFP losses and efficiencies and vice versa, from both isentropic and exergy viewpoints). Analyzed MFP has high isentropic and exergy efficiencies, considering all plant loads and ambient temperatures (at any plant load MFP isentropic efficiency is higher than 85%, while the lowest MFP exergy efficiency is equal to 89.24% at the lowest observed plant load and the highest observed ambient temperature). The change in isentropic and exergy efficiency of the MFP is small if all observed plant loads and ambient temperatures are taken into consideration.

This paper presents an exergy analysis of a two-cylinder low power steam turbine from combined cycle power plant at three operating regimes. The highest mechanical power produced in the whole turbine is 6807.24 kW in Operating regime 1. Cylinders of the observed turbine did not have the same operation dynamics in relation to produced mechanical power in all operating regimes. In each operating regime High Pressure Cylinder (HPC) has lower exergy destruction and higher exergy efficiency in comparison to Low Pressure Cylinder (LPC) due to the influence of wet steam which expands through the last LPC stages (water droplets in wet steam increases LPC exergy destruction and decreases LPC exergy efficiency). Whole turbine exergy efficiency is between 51.62% (in Operating regime 2) and 64.98% (in Operating regime 1). This range of exergy efficiencies can be expected for a low power steam turbine. An increase in the ambient temperature decreases exergy efficiency of the whole turbine and both turbine cylinders, regardless of the observed operating regime. The exergy efficiency of the LPC is low in all operating regimes, so any improvements should be based on this cylinder first.

In this paper is performed exergy analysis of steam re-heating system, through all of its components, which operate in nuclear power plant. Analyzed re-heating system consists of the moisture separator (MS) and two re-heaters (RH1 and RH2) and is observed in four different operating regimes. MS has significantly lower exergy destructions and significantly higher exergy efficiencies in comparison to both re-heaters, regardless of the observed operating regime. MS and both re-heaters did not achieve the lowest exergy destructions and the highest exergy efficiencies in the same operating regime which notably complicated possible improvements. Further research of presented re-heating system will be based on operation improvement of RH1 and RH2 – performed exergy analysis shows that MS operation in any operating regime leaves no room for further improvement.

This paper presents isentropic analysis results of the whole steam turbine (as well as turbine cylinders) from nuclear power plant. In the analyzed steam turbine, LPC (Low Pressure Cylinder) is the dominant mechanical power producer – mechanical power produced in the LPC is more than two times higher in comparison to mechanical power produced in the HPC (High Pressure Cylinder). Whole analyzed steam turbine produces real mechanical power equal to 1372.47 MW, while the highest possible mechanical power which can be produced in the whole turbine when all the losses are neglected (ideal mechanical power) equals 1686.96 MW. LPC has a notably higher isentropic efficiency than HPC, regardless of higher isentropic loss (isentropic efficiencies of the LPC and HPC are 84.41% and 74.84%, respectively). HPC has notably higher specific steam consumption and specific heat consumption in comparison to LPC. Whole turbine has an isentropic efficiency equal to 81.36%, isentropic loss equal to 314.48 MW, specific steam consumption of 9.15 kg/kWh and specific heat consumption of 3799.06 kJ/kWh, what is in the range of similar comparable steam turbines from nuclear power plants.

Exergy analysis results for the Whole observed steam Turbine and each of her cylinders at three loads are presented in this paper.
Observation of all cylinders shows that LPC (Low Pressure Cylinder) is the dominant mechanical power producer at the highest observed load, while at partial loads the dominant mechanical power producer is IPC (Intermediate Pressure Cylinder). At Load 100% Whole Turbine produces mechanical power equal to 341.11 MW. IPC is the cylinder with the lowest exergy destruction and the highest exergy efficiency (higher than 95%) at all observed loads. The exergy efficiency of the Whole Turbine (WT) continuously increases during the increase in turbine load (WT exergy efficiency is the lowest at Load 50% and equal to 91.36%, while at the Load 100% WT exergy efficiency is the highest and equal to 92.93%). Analyzed turbine is projected to operate dominantly on the Load 100% because at that load the exergy efficiencies of all cylinders and Whole Turbine are higher than 91%.