Steam Mass Flow Research Articles

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

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.

Numerical simulation of the liquid film suction process through the slots of various geometry in the last stages of steam turbines

The liquid film suction process through the slot is considered. The stator blade row of the last stage of the steam turbine was used as an object of study. Based on the CFD modelling of two-phase flow in blades cascade the boundary conditions for slots modelling have been obtained. The numerical analyses of film removal were conducted in a domain including only a flow zone near the studied slot. The multi-phase VOF model was used to calculate the interaction between liquid and steam phases and model the interface evolution during the water removal process. Four different geometries of the slots were considered. For each of them, the unsteady calculations at two different operating regimes have been performed. The numerical results provide information about film suction details in a space of the slot. The behaviour of the film flow was analysed for each slot shape. The conditions of the film separation and its further breakup have been considered. For the studied slot designs efficiency analysis was performed. The results have shown how the way the liquid film moves in the slot effects on the removed water and steam mass flow rates.

Leak detection in a subcritical boiler

Thermal power plants experience cycling duty leading to the fatigue of the boiler and heat exchanger tubes. As a result, tube failures occur frequently in coal fired fleets leading to forced outages. Because the tube leaks have been the major source of unwanted shutdowns and the number of outages is increasing, present work focuses on the detection and isolation of the leak in a subcritical boiler based upon the process data from a commercial coal-fired power plant. The mass balance equation around the steam drum was analyzed using timeseries data collected from a 300 MW power plant. The ratio of the feed water mass flow rate to the steam mass flow rate was defined as a key parameter for detecting leaks. The difference in slope between the feedwater and steam mass flow rate during the normal and faulty operations was established as the upper control limit for real time monitoring. To reduce false alarm rates that arise when raw signal is directly compared against the threshold due to common process fluctuations, an optimal filter was derived for smoothing. It was found that the optimal filter reacted much more quickly to process changes than an exponential moving average filter, around 8 h earlier on average. Occurrence of relatively high false alarm rates even in the filtered responses was related to the cycling of the boiler from the base load condition. Variable threshold was established to keep false alarm rates to the minimum while maintaining the leak detection rate. Finally, the leak was located at the economizer and this could readily be isolated by investigating the magnitude of the mass flow rates ratio and the temperature at the economizer outlet.

Numerical study of the parameters of a gas turbine combustion chamber with steam injection operating on distillate fuel

Abstract Investigations of the working process in a gas turbine combustion chamber with ecological and energy steam injection operating on liquid fuel are conducted. The mathematical model of the aerodynamic processes and liquid fuel combustion in similar burning devices based on the numerical solution of the system of conservation and transport equations for a multi-component chemically reactive turbulent system is developed. The influence of the relative steam mass flow rate (the ratio of the sum of the mass flow rates of ecological and energy steam to the fuel consumption) on the combustion chamber’s emission characteristics is determined. The obtained results can be used for parameter selection and optimization of promising high-temperature gas turbine combustion chambers with steam injection operating on liquid fuels.

Numerical study of the parameters of a gas turbine combustion chamber with steam injection operating on distillate fuel

Abstract Investigations of the working process in a gas turbine combustion chamber with ecological and energy steam injection operating on liquid fuel are conducted. The mathematical model of the aerodynamic processes and liquid fuel combustion in similar burning devices based on the numerical solution of the system of conservation and transport equations for a multi-component chemically reactive turbulent system is developed. The influence of the relative steam mass flow rate (the ratio of the sum of the mass flow rates of ecological and energy steam to the fuel consumption) on the combustion chamber’s emission characteristics is determined. The obtained results can be used for parameter selection and optimization of promising high-temperature gas turbine combustion chambers with steam injection operating on liquid fuels.

Modeling and optimization of finless and finned tube heat recovery steam generators for cogeneration plants

AbstractThis article aims to model and optimize the fire tube Heat Recovery Steam Generator (HRSG) used in a gas microturbine cogeneration of heat and power system. Here, six cases including a finless and finned tube (solid and serrated) HRSGs with the inline and staggered arrangements are optimized and compared using techno‐economic assessment. Optimization of HRSG was carried out by applying two objective functions of minimizing the total annual cost as well as maximizing the exergy efficiency. Nondominated Sorting Genetic Algorithm II is used to find out the optimal values of design variables. The TOPSIS decision‐making process is employed to choose the optimum point of the Pareto front. A 600 kW gas microturbine cogeneration plant is considered as a case study. The results revealed that the finless tube HRSG with an inline arrangement has the lower pinch and approach temperatures (3.5°C and 3.1°C, respectively), the higher steam mass flow rate (12.7%), the lower total annual cost (64 096$/year), and the higher exergy efficiency (60.6%). It is also found that using the staggered arrangement tube banks along with the solid fins in HRSG leads the total annual cost, the steam mass flow rate, and exergy efficiency increase up to 41.6%, 100%, and 12.6%, respectively. This means that the thermodynamic performance improvement will compensate the total annual cost increment. Furthermore, it is demonstrated that HRSG with solid fins and staggered arrangement with total annual costs of (90 810$/year), exergy efficiency of (73.2%), and steam mass flow rate of (4680 kg/h) has the best performance in comparison with other finned tube cases.

Thermodynamic modeling and performance evaluation of a supercritical coal-fired power plant situated in Western India

ABSTRACT Energy consumption in India is increasing drastically due to the increase in its population every year. In this severe condition, it is highly desirable to focus on the performance of existing and upcoming power plants in India using thermal performance analysis of each plant. The subcritical power plants are going to be replaced by supercritical power plants (SUPP) in the present scenario in the country. The present study deals with the thermal performance analysis of a 660 MW capacity coal-fired SUPP situated in western India. The thermodynamic modeling with empirical relation of each of its components is done and executed in MATLAB programming interface. The pure sliding pressure with variation in plant load is taken for constructing a semi-empirical model. The properties of steam are considered as per the IAPWS IF-97 standard. The results obtained from the simulation model are validated with actual operational data of the plant. The amount of coal consumption, steam mass flow rate, plant overall efficiency with variation in plant load is analyzed and compared with the operational data. The output obtained from the simulated program found to be satisfactory by comparing it with the actual operational plant data under study. The condenser rejects 36.42% of total heat to cooling water. The predicted steam generator efficiency of 86.04% is validated with actual steam generator efficiency. The simulated model of the SUPP will help those technologists and investigators who are putting their effort into improving the performance of coal-fired power plants.

Effect of water spray in exhaust passage of steam turbine on flow field of the last stage during windage

Under the windage condition, the steam in the last stage of steam turbine absorbs energy from rotor blade, which leads to overtemperature of the exhaust steam. Water spray is an effective way to lower the temperature in exhaust passage. The Euler-Lagrange particle tracking method is used to study the heat and mass transfer of the water spray in exhaust passage. The quantity of water spray under different conditions is predicted and the effect of water spray on the last stage flow field is analyzed. The results show that there is a small temperature difference between steam and liquid in the exhaust passage and a minimum evaporation of droplets for high steam velocity. The water spray quantity has a negative correlation with the inlet steam mass flow rate under different conditions and the ratio of water spray quantity to the inlet mass flow rate (water/steam ratio) has a quadratic relationship with the operating conditions. From 20%THA (Turbine Heat Acceptance) to 7%THA, the ratio of steam evaporated by water to mixture-vapor (H2O/mixture-vapor ratio) increases from 0.05% to 0.95%, and the water/steam ratio increases from 22% to 300%. The water spray has little effect on the rotor-stator clearance vortex and the separation vortex, but the height and velocity of the back flow vortex are increased. Meanwhile, the pressure of the last stage and the pressure ratio of the rotor blade increase, which result in the dissipating shaft power of the rotor blade reduces. Water spray has an effect on the flow field of the last stage, which is of great significance to correctly predict the windage conditions and study the dynamic characteristics of the rotor blade.

Direct condensation of steam in a water tank at sub-atmospheric pressures

In the nuclear fusion reactor, ITER, the Loss of Coolant Accident (LOCA) in the Vacuum Vessel has to be managed with pressure suppression systems working at sub-atmospheric pressure. The operating conditions differ considerably from those experienced in the fission nuclear power plants such as BWR. The direct condensation at sub-atmospheric conditions is not sufficiently known, therefore, the effectiveness of systems operating at these particular conditions have to be investigated experimentally.A research program is being carried out at the University of Pisa, funded by ITER, in order to study the steam direct condensation for nuclear fusion reactor conditions. For this purpose, an experimental test facility was designed and built and an extended experimental program was performed. Video cameras were used to visualize the steam condensation at different mass flow rates.This paper deals with the elaboration of images of the steam jet flowing from a hole in the water. The steam condensation regimes depend on three governing parameters: downstream exit pressure, water temperature and steam mass flow rate per hole. Moreover, the condensation regimes are characterized by different shapes of steam jet.The image analysis permitted to determine the heat transfer coefficient in the stable condensation regime at sub-atmospheric conditions. The results obtained are compared with those correspondent at steam condensation at atmospheric pressure, emphasizing the great importance of the downstream exit pressure and the subcooling on the steam condensation.

Characteristic and regulation method of parallel turbocompound engine with steam injection for waste heat recovery

In a parallel turbocompound engine, a power turbine (PT) is fitted in the exhaust pipe in parallel with the turbocharging turbine (CT) for waste heat recovery. In this study, steam is generated using the exhaust heat and injected at the turbines inlet to improve the turbine power and engine performance. Numerical model for the engine cycle is established using commercial software GT-POWER. The model is validated against the experimental results of the turbocompound engine and precisely predicts the engine performance. Based on the model, the impacts of the CT and PT sizes on the performance of the parallel turbocompound engine are evaluated firstly. It is found that variable geometry turbine (VGT) should be applied on PT to regulate the energy distribution between the two turbines at engine off-design condition. Then the influences of steam mass flow rate on the engine BSFC, power and efficiency are investigated. The optimum values of the steam mass flow rate and PT size is closely related to the exhaust temperature. At last, the characteristic and regulation pattern of the steam injected parallel turbocompound engines are compared with series turbocompound engine. In parallel turbcompound engine, the BSFC is decreased by 2.08%–3.28% with steam injection.

Energy and exergy analysis of a novel steam injected turbocompounding system applied on the marine two-stroke diesel engine

Waste heat recovery from marine power plants has been recognized as an effective approach to reduce CO2 emissions from ships. This paper proposes a novel steam injected turbocompounding system for recovering waste heat from the large marine two-stroke diesel engine. First, a sophisticated thermodynamic model that integrates the topping in-cylinder Diesel cycle and the bottoming steam injected Brayton cycle is built based on energy and exergy analysis. Parametric studies of the bottoming steam injected Brayton cycle are then conducted with special focuses on the steam generation and injection processes, followed by a comparison between the conventional turbocompounding system and the novel steam injected version. It is concluded that parameters of generated steam are mainly restricted by the design constraints of the exhaust gas boiler and the heat source temperature. Exergy destruction during the steam injection process accounts for a large proportion of the injected steam exergy. The injected steam mass flow rate plays a significant role in determining the exergy distributions in the turbocompounding system, while the steam temperature and pressure have limited effects. Compared to the base engine, the fuel consumption could be decreased by 5.1% at the rated speed with the novel steam injected turbocompounding system, while the improvement is around 3.3% with the conventional turbocompounding system.

Integrated study of flue gas flow and superheating process in a recovery boiler using computational fluid dynamics and 1D-process modeling

Superheaters are the last heat exchangers on the steam side in recovery boilers. They are typically made of expensive materials due to the high steam temperature and risks associated with ash-induced corrosion. Therefore, detailed knowledge about the steam properties and material temperature distribution is essential for improving the energy efficiency, cost efficiency, and safety of recovery boilers. In this work, for the first time, a comprehensive one-dimensional (1D) process model (1D-PM) for a superheated steam cycle is developed and linked with a full-scale three-dimensional (3D) computational fluid dynamics (CFD) model of the superheater region flue gas flow. The results indicate that: (1) the geometries of headers and superheater platens affect platen-wise steam mass flow rate distribution (3%–7%); and (2) the CFD solution of the 3D flue gas flow field and platen heat flux distribution coupled with the 1D-PM affect the platen-wise steam superheating temperature (45%–122%) and material temperature distribution (1%–6%). Moreover, it is also found that the commonly-used uniform heat flux distribution approach for the superheating process is not accurate, as it does not consider the effect of flue gas flow field in the superheater region. These new observations clearly demonstrate the value of the present integrated CFD/1D-PM modeling approach.

Comparison of conventional and heat balance based energy analyses of steam turbine

This paper presents a comparison of conventional and heat balance based energy analyses of steam turbine. Both analyses are compared by using measured operating parameters from low power steam turbine exploitation. The major disadvantage of conventional steam turbine energy analysis is that extracted energy flow streams are not equal in real (polytropic) and ideal (isentropic) expansion processes, while the heat balance based energy analysis successfully resolved mentioned problem. Heat balance based energy analysis require an increase of steam mass flow rates extracted from the turbine in ideal (isentropic) expansion process to ensure always the same energy flow streams to all steam consumers. Increase in steam mass flow rate extracted through each turbine extraction (heat balance based energy analysis) result with a decrease in energy power losses and with an increase in energy efficiency of whole turbine and all of its cylinders (when compared to conventional analysis). All of the obtained conclusions in this research are valid not only for the analyzed low power steam turbine, but also for any other steam turbine with steam extractions.

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

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.

A useful formulas to describe the performance of a steam condenser in off-design conditions

The article presents relations for determining the performance of a steam condenser in off-design operating conditions. To determine some steam condenser characteristics that are simplified, but useful for analyzing steam cycles of a power unit, a model validated on the basis of factory characteristics and measurement data was used. Formulas presented in the article-for given values of cooling water temperature at the condenser inlet, the cooling water mass flow rate, the inlet steam mass flow rate and reference data-determine the cooling water temperature at the outlet and the pressure in the steam condenser. The model can be used to analyze the operation of cooling systems in off-design conditions and to optimize the way the condenser works with the low-pressure (LP) part of the turbine and all steam cycles. The two proposed relations make it possible to determine the condenser performance easily and with acceptable accuracy. The correctness of the proposed relations was verified on the basis of data obtained from the condenser simulator, measurements obtained from the Distributed Control System (DCS), and data provided in the literature.

Numerical analysis of sub-atmospheric steam condensation in suppression tank with SIMMER IV code

Abstract One of the key safety components for nuclear fusion plants is the suppression tank, which is designed to protect the Vacuum Vessel (VV) against accidental pressurization events, e.g. Loss Of Coolant Accident (LOCA). In this framework the attention is focused on the Vacuum Vessel Pressure Suppression System (VVPSS), made of water tanks in which the pure steam, or eventually mixed with incondensable gases, is injected and consequently the overpressure is dumped profiting of Direct Contact Condensation (DCC). The design constraints of fusion reactor dictate that the pressure resulting (long-term) from any accidental or baking condition should be always kept lower than 0.15 MPa. The study of the phenomena evolving during DCC in LOCA conditions is the major novelty, especially in consideration of the lack of similar studies in the available literature. In this context, a wide series of experimental tests was carried out at Pisa University (UNIPI), Department of Civil and Industrial Engineering (DICI), in a Small Scale Test Facility (SSTF), designed and instrumented for investigating DCC at sub-atmospheric pressure, by varying water pool temperature, pressure and steam mass flow rate. The adoption and assessment of suitable numerical codes, to reliably simulate such a cutting-edge multiphase multicomponent scenario, have a crucial role for contributing to the phenomena understanding and for possible safety analysis of full-scale components. On this basis, a preliminary evaluation of the cartesian three-dimensional SIMMER IV code capabilities in simulating DCC at sub-atmospheric conditions was carried out, taking as reference one UNIPI test. SIMMER IV code was able to set up precise initial low-pressure boundary conditions and simulate superheated steam condensation in subcooled water pool, with condensation efficiency comparable to the experimental one. Moreover, SIMMER IV code predicted a longitudinal steam plume dimension and injected steam velocity consistent with experimental data.

Steam consumption minimization using genetic algorithm optimization method: an industrial case study

ABSTRACT Condensate stabilization is a process where hydrocarbon condensate recovered from natural gas reservoirs is processed to meet the required storage, transportation, and export specifications. The process involves stabilizing of hydrocarbon liquid by separation of light hydrocarbon such as methane from the heavier hydrocarbon constituents such as propane. An industrial scale back-up condensate stabilization unit was simulated using Aspen HYSYS software and validated with the plant data. The separation process consumes significant amount of energy in form of steam. The objectives of the paper are to find the minimum steam consumption of the process and conduct sensitivity and exergy analyses on the process. The minimum steam consumption was found using genetic algorithm optimization method for both winter and summer conditions. The optimization was carried out using MATLAB software coupled with Aspen HYSYS software. The optimization involves six design variables and four constraints, such that realistic results are achieved. The results of the optimization show that savings in steam consumption is 34% as compared to the baseline process while maintaining the desired specifications. The effect of natural gas feed temperature has been investigated. The results show that steam consumption is reduced by 46% when the natural gas feed temperature changes from 17.7 to 32.7°C. Exergy analysis shows that exergy destruction of the optimized process is 37% less than the baseline process. Abbreviations: BCSU: Back-up condensate stabilization unit; GA: Genetic algorithm; MEG: Monoethylene glycol; RVP: Reid Vapor Pressure; LPG: Liquefied petroleum gas; Q ˙ : Heat rate; \\dotm Sat . Steam : Saturated steam mass flow rate; h fg : Latent heat; HP: High pressure; LP: Low pressure; LHV: Low heating value; X ˙ destroyed : Exergy destruction; s ˙ gen : Entropy generation; h 1 x ⃗ : Equality constraint; g j x ⃗ : Inequality constraint; x ⃗ : Design variables.

Karakteristik Pembakaran Difusi Campuran Solar Murni dengan Minyak Kelapa

This research was conducted to determine the effect of adding coconut oil to pure diesel oil on the characteristics of diesel oil steam diffusion combustion. The characteristics observed are flame height and fire temperature. The combustion process is carried out on a circular tube burner. The steam mass flow of fuel in this study is 0.0895 grams / second. From the results of the study the biggest results were obtained in the mixture of 90% diesel oil with 10% coconut oil, fire height of 94.51 mm and a temperature of 967˚C and the lowest yield was found in a mixture of 70% diesel oil and 30% coconut oil, namely temperature amounting to 796˚C and fire height of 68.85 mm. From this, it can be concluded that the greater the percentage of diesel oil added to the combustion process, the higher and the flame temperature will increase. This is due to the characteristics of different fuels, where diesel oil has a lower viscosity than coconut oil and has a heating value greater than coconut oil.

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

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.

Flow morphology and heat transfer analysis during high-pressure steam condensation in an inclined tube part I: Experimental investigations

In this paper, experimental investigations on the flow morphology and heat transfer in a single steam condenser tube are presented, which were performed at the thermal hydraulic test facility COSMEA (COndensation test rig for flow Morphology and hEAt transfer studies). This facility was setup to study the interrelation of condensation heat transfer with two-phase flow in a single condenser tube that is cooled by forced convection. Studies were performed for elevated pressures up to 65 bar at saturation conditions and for inlet steam mass flow of up to 1 kg/s and different inlet steam qualities. The wall heat flux is measured with distributed heat flux probe and global condensation rates were obtained from integral heat and mass balances. As a unique feature the cross-sectional phase distribution was studied via X-ray computed tomography. The data is going to be used for the validation of numerical simulations with 1D ATHLET and 3D CFD codes as presented in the second part of this paper.