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

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%.

In this paper is performed an isentropic analysis of the entire Intermediate Pressure Cylinder (IPC) and all of his four Segments. Obtained results show that the first Segment (Seg. 1) is the dominant mechanical power producer of all Segments and it produces 16816.70 kW of mechanical power in the real (polytropic) expansion process. Analyzed IPC produces more than half mechanical power of the entire turbine in which he operates (in real expansion process IPC produces mechanical power equal to 58499.48 kW). Isentropic loss and isentropic efficiency of IPC Segments are reverse proportional – Seg. 3 which has the highest isentropic loss simultaneously has the lowest isentropic efficiency (equal to 82.44%), while Seg. 4 which has the lowest isentropic loss has the highest isentropic efficiency (equal to 87.26%). Entire IPC has an isentropic efficiency equal to 87.78%. Any improvements and modifications which can potentially be performed in the observed IPC should firstly be based on the turbine stages mounted inside Seg. 3.

This paper presents results of two different isentropic analysis types: conventional isentropic analysis which considers the whole steam turbine cylinder and segmental isentropic analysis which considers all cylinder parts (segments). In conventional isentropic analysis is obtained that isentropic efficiency of the analyzed turbine is 73.39%, what is in a range of expected isentropic efficiencies for such steam turbines (in the mechanical power range around 60 MW). Segmental isentropic analysis shows that the last two segments (fifth and sixth segment) of the analyzed turbine did not show proper operation (especially the fifth turbine segment which isentropic efficiency is unacceptably low and equal to 26.73% only). Such isentropic efficiency results, related to the fifth and sixth turbine segment, indicate highly problematic operation, or the most likely malfunction of at least some turbine stages in these segments. For the analyzed steam turbine can be recommended that it should be stopped as soon as possible and that turbine stages mounted in the last two segments should be checked, repaired or replaced.

In this paper is presented an exergy analysis of steam turbine (along with analysis of each cylinder and cylinder part) from ultrasupercritical power plant. Observation of all the cylinders shows that IPC (Intermediate Pressure Cylinder) is the dominant mechanical power producer (it produces mechanical power equal to 394.44 MW), it has the lowest exergy loss and simultaneously the highest exergy efficiency (equal to 95.84%). HPC (High Pressure Cylinder) has a very high exergy efficiency equal to 92.37% what confirms that ultrasupercritical steam process is very beneficial for the HPC (and whole steam turbine) operation. LPC (Low Pressure Cylinder) is a dissymmetrical dual flow cylinder, so both of its parts (left and right part) did not produce the same mechanical power, did not have the same exergy loss, but their exergy efficiency is very similar and in a range of entire LPC exergy efficiency (around 82.5%). Whole observed steam turbine produces mechanical power equal to 928.03 MW, has exergy loss equal to 93.45 MW and has exergy efficiency equal to 90.85%. The exergy efficiency of the whole analyzed steam turbine is much higher in comparison to other steam turbines from various conventional power plants.

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.

This paper presents an energy analysis of middle-power steam turbine with two cylinders (High Pressure Cylinder – HPC and Low Pressure Cylinder – LPC) and steam re-heater after the HPC (and before the LPC). Based on a steam operating parameters from the literature, performed energy analysis show that LPC develops higher power and has higher energy efficiency (81.45%) in comparison to HPC (which energy efficiency equals 80.12%). Re-heater is a heat exchanger (flue gases are used for steam heating) which has low energy loss (824.19 kW) and high energy efficiency (97.76%), what is expected energy performance of such heat exchanger. The entire analyzed turbine develops a power of 127480.60 kW and has energy loss equal to 29848.21 kW with energy efficiency of 81.03%.

In this paper is performed energy evaluation of steam turbine from the solar-based combined cycle power plant which includes analysis of each cylinder and the whole turbine. Steam turbine has three cylinders – high, intermediate and low pressure cylinders (HPC, IPC and LPC). Observed turbine is interesting because it possesses steam cooling before its expansion through the last cylinder (LPC). Due to unknown steam mass flow rates through each cylinder, for the evaluation are used specific variables. The highest specific work is obtained in LPC, while the lowest specific work is obtained in IPC. The highest loss of a specific work is obtained in LPC (29.8 kJ/kg), followed by HPC (24.5 kJ/kg), while the lowest loss of a specific work is obtained for the IPC (19.5 kJ/kg). Regardless of higher loss in specific work, HPC has higher energy efficiency in comparison to IPC (95.08% in comparison to 95.02%), while the lowest energy efficiency of all cylinders has LPC (94.92%). For the whole observed steam turbine loss of a specific work is equal to 73.8 kJ/kg, while the energy efficiency of the whole turbine is 95.00%.

In this paper is presented energy (isentropic) analysis of high power, three-cylinder steam turbine with steam re-heating. A comparison of real (polytropic) and ideal (isentropic) steam expansion processes at nominal load show that observed turbine develops real power of 655.35 MW, while in ideal situation it can develop 716.18 MW. The highest energy loss and the lowest energy efficiency occur in the high pressure turbine cylinder (25.67 MW and 89.14%), while intermediate pressure cylinder has the highest energy efficiency and the lowest energy loss. The energy efficiency of the whole observed turbine is 91.51%, what is in the expected range for such high power steam turbines at nominal load. Further optimization of this steam turbine will be primarily based on the high pressure cylinder.

The paper present thermodynamic analysis of three-cylinder steam turbine, which operates in a combined cycle power plant. It is performed analysis of each turbine cylinder and of entire steam turbine. Comparison of steam turbine cylinders shows that intermediate pressure cylinder develops the highest real power and has the highest efficiencies while low pressure cylinder has the highest ideal (isentropic) power, the highest loses and the lowest efficiencies – therefore, improvement potential of the low pressure cylinder is the highest. Entire observed steam turbine has an energy efficiency equal to 86.58 % and exergy efficiency equal to 89.26 %, what is lower in
comparison to high power steam turbines from some conventional land-based steam power plants but also higher in comparison to low power marine steam turbines.

Developed power variation of turbo-generator (TG) steam turbine allows insight into the change of turbine energy efficiency and energy power losses. Measurements were performed in five different TG steam turbine operating points and analysis is presented in three randomly selected operating points. Turbine developed power was varied from 500 kW until the maximum power of 3850 kW in steps of 100 kW. Turbine energy efficiency increases from 500 kW to 2700 kW and maximum energy efficiency was obtained at 70.13 % of maximum turbine power (at 2700 kW) in each operating point. From 2700 kW until the maximum of 3850 kW, TG turbine energy efficiency decreases. Change in TG turbine energy efficiency is caused by an uneven intensity of increase in turbine power and steam mass flow. For all observed operating points, energy efficiency during turbine exploitation is approximately 10 % or more lower than the maximum obtained one. A continuous increase in turbine energy power losses during the developed turbine power increase are the most influenced by the continuous increase in steam mass flow through the turbine.

Turbo-generator (TG) steam turbine energy efficiency and energy power losses in a wide range of turbine loads were presented in this analysis. For TG steam turbine was investigated influence of steam specific entropy increment from the real (polytropic) steam expansion on energy power losses and energy efficiency. TG turbine energy power losses, during the all observed loads, were in the range from 646.1 kW to 685.5 kW. The most influenced parameter which defines change in TG turbine energy power losses is steam mass flow change, while for small steam mass flow changes, influence of steam specific entropy increment on steam turbine energy power losses is the most influential. Steam specific entropy incremental change can be used to estimate the change of TG steam turbine energy efficiency. Increase in steam specific entropy increment resulted with a decrease in TG turbine energy efficiency and vice versa. Analyzed steam turbine energy efficiency ranges from 53.84 % to 60.12 %, what is an expected range for low power steam turbines.