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

The results of three turbomachines (one turbocompressor and two turbines) isentropic and exergy analyses, which operate in supercritical CO2 power plant are presented in this paper. Both observed turbines (Turbine 1 and Turbine 2) have higher improvement potential than Turbocompressor. Mechanical losses in power transmission between Turbine 1 and Turbocompressor are equal to 456.57 kW in real operation process. Turbocompressor has the highest isentropic efficiency of 96.87% and the highest exergy efficiency of 97.61% if all observed turbomachines are considered. Turbine 2 used for the electric generator drive has higher efficiencies (both isentropic and exergy) in comparison to Turbine 1, regardless of higher isentropic loss and higher exergy destruction. Increase in the ambient temperature from 5 °C up to 45 °C decreases Turbocompressor exergy efficiency for 0.31%, while the same ambient temperature increase decreases exergy efficiency of both turbines for 0.53% (Turbine 1) and for 0.52% (Turbine 2).

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%.

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.

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.

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.

This paper presents an energy analysis of a three-cylinder steam turbine from a combined cycle power plant. Observing all the cylinders from the analyzed turbine, it is found that the dominant mechanical power producer is Low Pressure Cylinder (LPC), followed by the Intermediate Pressure Cylinder (IPC), while High Pressure Cylinder (HPC) is the cylinder which produces the lowest mechanical power. Whole observed steam turbine develop 119.41 MW of useful mechanical power. Energy loss and energy efficiency of all cylinders are reverse proportional – higher energy efficiency will result with lower energy loss and vice versa. IPC is the cylinder which has the lowest energy loss (equal to 2.59 MW) and the highest energy efficiency of 93.32%. Whole observed steam turbine has energy loss equal to 23.43 MW, while its energy efficiency is equal to 83.60%, what falls in the expected range of such low power steam turbines. Steam mass flow rate through each cylinder is the main element which defines produced mechanical power and energy flows.

The goal of the paper is estimating the normalized friction torque of a joint in an industrial robotic manipulator. For this purpose a source data, given as a figure, is digitized using a tool WebPlotDigitizer in order to obtain numeric data. The numeric data is the used within the machine learning algorithm genetic programming (GP), which performs the symbolic regression in order to obtain the equation that regresses the dataset in question. The obtained model shows a coefficient of determination equal to 0.87, which indicates that the model in question may be used for the wide approximation of the normalized friction torque using the torque load, operating temperature and joint velocity as inputs.

This paper presents an energy analysis of main and auxiliary steam turbines from conventional coal fired power plant. Main turbine is composed of three cylinders connected to the same shaft which drives an electric generator, while auxiliary steam turbine is used for the boiler feedwater pump drive. The whole analyzed main steam turbine produces mechanical power equal to 312.34 MW, while in an ideal situation, it can produce mechanical power equal to 347.28 MW. The highest part of the mechanical power in the main turbine is produced in the low pressure cylinder. Auxiliary steam turbine in exploitation develops mechanical power equal to 6768.94 kW, while in an ideal situation it can develop 8029.03 kW. Whole main turbine energy efficiency is equal to almost 90% what is in the expected range for such high power turbines. The auxiliary steam turbine has an energy efficiency equal to 84.31%, which is almost 6% lower in comparison to the main turbine. Energy flows delivered to the last two feedwater heaters (HPH2 and HPH3) in the condensate/feedwater heating system are notably higher in comparison to energy flows delivered to any other condensate/feedwater heater.

In this paper, two-cylinder steam turbine, which operates in nuclear power plant is analyzed from the energy viewpoint. Along with the whole turbine, energy analysis is performed for each turbine cylinder (High Pressure Cylinder – HPC and Low Pressure Cylinder – LPC). A comparison of both cylinders shows that the dominant mechanical power producer is LPC, which also has much higher energy loss and much lower energy efficiency. Therefore, any potential improvement of this steam turbine should be based dominantly on th e LPC, which also has a dominant influence on energy analysis parameters of the whole observed turbine. The whole turbine produces real (polytropic) mechanical power equal to 1247.69 MW, has energy loss equal to 352.70 MW and energy efficiency equal to 77.96%. According to obtained energy efficiency value it can be concluded that the whole analyzed steam turbine is comparable to main marine propulsion steam turbines, while its energy efficiency is much lower in comparison to steam turbines from conventional steam power plant s which operates by using superheated steam.

This paper presents exergy analysis of the main steam condenser, which operates in nuclear power plant. The analysis is performed in four main condenser operating regimes (loads) for a variety of the ambient temperatures. It is found that the main steam condenser has the lowest exergy destruction (equal to 72091.56 kW) and the highest exergy efficiency (equal to 66.66%) at the lowest observed ambient temperature (5 °C) and for the highest of four observed loads. Also, it is noted that an increase in the ambient temperature from 20 °C to 25 °C (two the highest observed ambient temperatures) significantly decreases main steam condenser exergy efficiency for about 21%, regardless of the observed load.

This paper presents an analysis and comparison of three steam turbines and its cylinders: from the conventional steam power plant, from nuclear power plant and from the marine propulsion plant. The best parameters for the comparison of whole turbines and its cylinders are: energy loss per unit of produced mechanical power, exergy destruction per unit of produced mechanical power, energy efficiency and exergy efficiency. Steam turbine from marine propulsion plant shows the worst performance, regardless if observing each cylinder or the whole turbine – it has the highest losses per unit of produced mechanical power and the lowest efficiencies (both energy and exergy). Such results can be explained by a fact that marine steam turbine must be much more dynamic in operation in comparison to other two turbines. Also, marine steam turbine analyzed in this paper did not possess steam reheating between the cylinders as the other two observed steam turbines, what has a dominant impact on the obtained results.