scholarly journals Comparison of Power Distribution, Losses and Efficiencies of a Steam Turbine with and without Extractions

2020 ◽  
Vol 14 (4) ◽  
pp. 480-487
Author(s):  
Vedran Mrzljak ◽  
Sandi Baressi Šegota ◽  
Hrvoje Meštrić ◽  
Zlatan Car
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Distribution ◽  
Power Losses ◽  
Base Process ◽  
Energy And Exergy ◽  
Simultaneous Decrease ◽  
Dominant Influence

The paper presents an analysis of two steam turbine operation regimes - regime with all steam extractions opened (base process) and regime with all steam extractions closed. Closing of all steam extractions significantly increases turbine real developed power for 5215.88 kW and increases turbine energy and exergy losses with simultaneous decrease of turbine energy and exergy efficiencies for more than 2%. First extracted steam mass flow rate has a dominant influence on turbine power losses (in comparison to turbine maximum power when all of steam extractions are closed). Cumulative power losses caused by steam mass flow rate extractions are the highest in the fourth turbine segment and equal to 1687.82 kW.

Exergy-Based Optimization of Sub- and Supercritical Thermal Energy Storage Systems

2014 ◽  
Author(s):  
Louis A. Tse ◽  
Reza Baghaei Lakeh ◽  
Richard E. Wirz ◽  
Adrienne S. Lavine
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Energy And Exergy

In this work, energy and exergy analyses are applied to a thermal energy storage system employing a storage medium in the two-phase or supercritical regime. First, a numerical model is developed to investigate the transient thermodynamic and heat transfer characteristics of the storage system by coupling conservation of energy with an equation of state to model the spatial and temporal variations in fluid properties during the entire working cycle of the TES tank. Second, parametric studies are conducted to determine the impact of key variables (such as heat transfer fluid mass flow rate and maximum storage temperature) on both energy and exergy efficiencies. The optimum heat transfer fluid mass flow rate during charging must balance exergy destroyed due to heat transfer and exergy destroyed due to pressure losses, which have competing effects. Similarly, the optimum maximum storage fluid temperature is evaluated to optimize exergetic efficiency. By incorporating exergy-based optimization alongside traditional energy analyses, the results of this study evaluate the optimal values for key parameters in the design and operation of TES systems, as well as highlight opportunities to minimize thermodynamic losses.

First and second thermodynamic law analyses applied to a solar dish collector

2014 ◽  
Vol 39 (4) ◽  
Author(s):  
Vahid Madadi ◽  
Touraj Tavakoli ◽  
Amir Rahimi
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Flow Rates ◽  
Energy And Exergy ◽  
Mass Flow Rates

AbstractThe energy and exergy performance of a parabolic dish collector is investigated experimentally and theoretically. The effect of receiver type, inlet temperature and mass flow rate of heat transfer fluid (HTF), receiver temperature, receiver aspect ratio and solar radiation are investigated. To evaluate the effect of the receiver aperture area on the system performance, three aperture diameters are considered. It is deduced that the fully opened receivers have the greatest exergy and thermal efficiency. The cylindrical receiver has greater energy and exergy efficiency than the conical one due to less exergy destruction. It is found that the highest exergy destruction is due to heat transfer between the sun and the receivers and counts for 35 % to 60 % of the total wasted exergy. For three selected receiver aperture diameters, the exergy efficiency is minimum for a specified HTF mass flow rate. High solar radiation allows the system to work at higher HTF inlet temperatures. To use this system in applications that need high temperatures, in cylindrical and conical receivers, the HTF mass flow rates lower than 0.05 and 0.09 kg/s are suggested, respectively. For applications that need higher amounts of energy content, higher HTF mass flow rates than the above mentioned values are recommended.

Thermo-Efficiencies of a Tubular Combustor Under Different Inlet Conditions

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Ahmet Topal ◽  
Onder Turan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Loading Condition ◽  
Inlet Temperature ◽  
Test Rig ◽  
Aerodynamic Loading ◽  
Air Inlet ◽  
Energy And Exergy ◽  
Inlet Conditions

AbstractExergy efficiencies of the gas turbine become an important issue in recent years and by the way conducted studies regarding to this subject shows that the highest exergy destruction is observed in the combustor and afterburner modules. Therefore it is beneficial to perform analyses that are specific to the combustor exergy efficiency. This study includes the energy$\left( {{\eta _{cc}}} \right)$and exergy efficiencies$\left( {{\eta _{ex}}} \right)$(thermo-efficiencies) of a tubular combustor for different inlet conditions. Both of the first law and second law efficiencies have been performed on the experimental data and efficiency trends are investigated for changing aerodynamic conditions. Combustor tests have been conducted in an atmospheric test rig and combustor air inlet temperature$\left( {{T_{03}}} \right)$, air mass flow rate$\left( {{{\dot m}_a}} \right)$and fuel mass flow rate$\left( {{{\dot m}_f}} \right)$have been set for the pre-defined conditions. Moreover, exhaust gas emissions were measured by using a gas analyzer system. In the study, highest energy and exergy efficiencies have been obtained at minimum aerodynamic loading condition as 99.0 % and 70.2 % respectively. Moreover efficiencies have the lowest value as 92.7 % and 54.0 % at the maximum aerodynamic loading condition. To summarize, this study aims to show the energy and exergy trends by changing inlet conditions of a tubular combustor in the atmospheric test rig.

scholarly journals The Leakage of Steam Mass Flow Rate through the Gland Seals – Influence on Turbine Produced Power

2020 ◽  
Vol 58 (1) ◽  
pp. 39-56
Author(s):  
Vedran Mrzljak ◽  
Jan Kudláček ◽  
Đerzija Begić-Hajdarević ◽  
Jelena Musulin
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Rates ◽  
Turbine Performance ◽  
Gland Seal ◽  
Mass Flow Rates ◽  
Marine Applications ◽  
Main Operating

In this paper is presented an analysis of gland seals operation and their influence on the performance of low power steam turbine with two cylinders and steam reheating, which can be used in marine applications. Performed analysis presents a comparison of steam turbine main operating parameters when gland seals operation is neglected (as usual in the most of the literature) and when steam mass flow rates leaked through all gland seals are taken into consideration. Steam mass flow rate leakage through all gland seals reduces produced power of the whole turbine and both of its cylinders. Operation of gland seal mounted at the inlet in the first cylinder of any steam turbine (cylinder which operates with the steam of the highest pressure) has the most notable influence on the reduction of the whole turbine produced power. Gland seal mounted at the outlet of the last turbine cylinder (cylinder which operates with the steam of the lowest pressure) did not have any influence on the reduction of steam turbine produced power. In any detail analysis of a steam turbine (especially the complex turbine with multiple cylinders), gland seals operation should be considered due to their notable influence on the turbine performance.

scholarly journals Theoretical and Experimental Investigation of a 34 Watt Radial-Inflow Steam Turbine With Partial-Admission

2020 ◽  
Author(s):  
Patrick H. Wagner ◽  
Jan Van herle ◽  
Jürg Schiffmann
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Tip Clearance ◽  
Experimental Results ◽  
Partial Admission ◽  
Blade Tip

Abstract A micro steam turbine with a tip diameter of 15 mm was designed and experimentally characterized. At the nominal mass flow rate and total-to-total pressure ratio of 2.3 kg h−1 and 2, respectively, the turbine yields a power of 34 W and a total-to-static isentropic efficiency of 37%. The steam turbine is conceived as a radial-inflow, low-reaction (15%), and partial admission (21%) machine. Since the steam mass flow rate is limited by the heat provided of the system (solid oxide fuel cell), a low-reaction and high-power-density design is preferred. The partial-admission design allows for reduced losses: The turbine rotor and stator blades are prismatic, have a radial chord length of 1 mm and a height of 0.59 mm. Since the relative rotor blade tip clearance (0.24) is high, the blade tip leakage losses are significant. Considering a fixed steam supply, this design allows to increase the blade height, and thus reducing the losses. The steam turbine drives a fan, which operates at low Mach numbers. The rotor is supported on dynamic steam-lubricated bearings; the nominal rotational speed is 175 krpm. A numerical simulation of the steam turbine is in good agreement with the experimental results. Furthermore, a novel test rig setup, featuring extremely-thin thermocouples (ϕ0.15 mm) is investigated for an operation with ambient and hot air at 220 °C. Conventional zero and one-dimensional pre-design models correlate well to the experimental results, despite the small size of the turbine blades.

Direct Constrained Computational Fluid Dynamics Based Optimization of Three-Dimensional Blading for the Exit Stage of a Large Power Steam Turbine

2002 ◽  
Vol 125 (1) ◽  
pp. 385-390 ◽  
Author(s):  
P. Lampart ◽  
S. Yershov
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Steam Turbines ◽  
Original Design ◽  
Large Power ◽  
Wide Range

The paper describes results of direct constrained optimization using Nelder-Mead’s method of deformed polyhedron and a Reynolds-averaged Navier-Stokes (RANS) solver to optimize the shape of three-dimensional blading for the exit stage of a large power steam turbine. The computations of the flowfield in the stator and rotor are compressible, viscous, and three-dimensional. Turbulence effects are taken into account using the modified model of Baldwin-Lomax. The objective function is the stage efficiency, with the exit energy considered a loss, and with constraints imposed on the mass flow rate in the form of a penalty function if the mass flow rate falls beyond the required range. The blade sections (profiles) are assumed not to change during the optimization. Two optimization tasks are reported in this paper, first—optimizing the stator straight and compound circumferential lean, and also stator and rotor stagger angles to keep the flow rate unchanged, giving a total number of optimized parameters equal to 5; second—optimizing the stator straight and compound axial sweep, also with stator and rotor stagger angles, also giving five optimized parameters. The process of optimization is carried out for a nominal load; however, due to the fact that exit stages of steam turbines operate over a wide range of flow rates away from the nominal conditions, the original and final geometries are also checked for low and high loads. The process of optimization gives new designs with new three-dimensional stacking lines of stator blades, and with significantly increased efficiencies, compared to the original design, at least for a larger part of the assumed range of load.

scholarly journals Energy Loss Analysis at the Gland Seals of a Marine Turbo-Generator Steam Turbine

2020 ◽  
Vol 14 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Lino Kocijel ◽  
Igor Poljak ◽  
Vedran Mrzljak ◽  
Zlatan Car
Keyword(s):  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Measurement Data ◽  
Energy Losses ◽  
Operating Parameters ◽  
Steam Turbines ◽  
Turbo Generator ◽  
Gland Seal

The paper presents an analysis of marine Turbo-Generator Steam Turbine (TGST) energy losses at turbine gland seals. The analyzed TGST is one of two identical Turbo-Generator Steam Turbines mounted in the steam propulsion plant of a commercial LNG carrier. Research is based on the TGST measurement data obtained during exploitation at three different loads. The turbine front gland seal is the most important element which defines TGST operating parameters, energy losses and energy efficiencies. The front gland seal should have as many chambers as possible in order to minimize the leaked steam mass flow rate, which will result in a turbine energy losses’ decrease and in an increase in energy efficiency. The steam mass flow rate leakage through the TGST rear gland seal has a low or negligible influence on turbine operating parameters, energy losses and energy efficiencies. The highest turbine energy efficiencies are noted at a high load – on which TGST operation is preferable.

Using a Bowed Blade to Improve the Supersonic Flow Performance in the Nozzle of a Supersonic Industrial Steam Turbine

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Hong Yao ◽  
Xun Zhou ◽  
Zhongqi Wang
Keyword(s):  
Shock Wave ◽  
Supersonic Flow ◽  
Steam Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Wave Structure ◽  
Shock Wave Structure ◽  
Waste Energy ◽  
Low Mass

For solar plants, waste-energy recovery, and turbogenerators, there is a considerable amount of waste energy due to low mass flow rate. Owing to the high specific power output and large pressure ratios across the turbine, a supersonic industrial steam turbine (IST) is able to utilize the waste energy associated with low mass flow rate. Supersonic IST has fewer stages than conventional turbines and a compact and modular design, thus avoiding the excessive size and manufacturing cost of conventional IST. Given their flexible operation and ability to function with loads in the range of 50–120% of the design load, supersonic IST offers significant advantages compared to conventional IST. The strong shock-wave loss caused by supersonic flows can be reduced by decreasing the shock intensity and reducing its influence; consequently, a supersonic IST can reach higher efficiency levels. Considering the demonstrated utility of bowed blades in conventional IST, this paper presents a study of the use of bowed blades in a supersonic IST. For this purpose, first, the shock-wave structure in the supersonic flow field was analyzed and compared with experimental results. Then, four different bowed blades were designed and compared with a straight blade to study the influence of bowed blades on the shock-wave structure and wetness. The results indicate that S-shaped bowing can improve the efficiency of supersonic turbines, and the energy-loss coefficient of the stators can be decreased by 2.4% or more under various operating conditions.

scholarly journals An energy and exergy study of a solar thermal air collector

2009 ◽  
Vol 13 (1) ◽  
pp. 205-216 ◽  
Author(s):  
Ehsan Mohseni-Languri ◽  
Hessam Taherian ◽  
Reza Masoodi ◽  
John Reisel
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Second Law ◽  
Solar Air Heater ◽  
Heating Systems ◽  
Test Setup ◽  
The North ◽  
Energy And Exergy ◽  
North Of Iran

A solar flat plate air collector was manufactured in the north of Iran, and connected to a room as the model to study the possibility of using such solar heating systems in the northern parts of Iran. This collector was tested as a solar air heater to see how good it could be for warming up the test room during the winter. The experimental data obtained through accurate measurements were analyzed using second law approach to find the optimum mass flow rate, which leads to the maximum exergy efficiency. It was found that for the test setup at the test location, a mass flow rate of 0.0011 kg/s is the optimum mass flow rate for tested conditions which leads to the highest second law efficiency.

scholarly journals Thermal-Hydraulic Analysis of Coolant Flow Decrease in Fuel Channels of Smolensk-3 RBMK during GDH Blockage Event

2007 ◽  
Vol 2007 ◽  
pp. 1-7
Author(s):  
A. Lombardi Costa ◽  
M. Cherubini ◽  
F. D'Auria ◽  
W. Giannotti ◽  
A. Moskalev
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Distribution ◽  
Nuclear Power ◽  
Thermal Power ◽  
Safety Evaluation ◽  
Coolant Flow ◽  
Start Time ◽  
Excessive Heat

One of the transients that have received considerable attention in the safety evaluation of RBMK reactors is the partial break of a group distribution header (GDH). The coolant flow rate blockage in one GDH might lead to excessive heat-up of the pressure tubes and can result in multiple fuel channels (FC) ruptures. In this work, the GDH flow blockage transient has been studied considering the Smolensk-3 RBMK NPP (nuclear power plant). In the RBMK, each GDH distributes coolant to 40–43 FC. To investigate the behavior of each FC belonging to the damaged GDH and to have a more realistic trend, one (affected) GDH has been schematized with its forty-two FC, one by one. The calculations were performed using the 0-D NK (neutron kinetic) model of the RELAP5-3.3 stand-alone code. The results show that, during the event, the mass flow rate is disturbed differently according to the power distribution established for each FC in the schematization. The start time of the oscillations in mass flow rate depends strongly on the attributed power to each FC. It was also observed that, during the event, the fuel channels at higher thermal power values tend to undergo first cladding rupture leaving the reactor to scram and safeguarding all the other FCs connected to the affected GDH.

Sign in / Sign up

Export Citation Format

Share Document