scholarly journals A Model for Liquid Films in Steam Turbines and Preliminary Validations

2016 ◽  
Author(s):  
Amélie Simon ◽  
Meryem Marcelet ◽  
Jean-Marc Hérard ◽  
Jean-Marc Dorey ◽  
Michel Lance
Keyword(s):  
Mass Transfer ◽  
Shallow Water Equations ◽  
Liquid Films ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Power Losses ◽  
Pressure Surface ◽  
Falling Liquid Film ◽  
Pressure Steam ◽  
Droplet Impacts

Liquid films in steam turbines, present in usual operating conditions, play a large but poorly understood part in the wetness-born troubles (power losses and erosion). More knowledge is needed to estimate their impacts and lessen their effects. The aim of this paper is to propose and verify a model to predict these liquid films. This model is based on modified Shallow-Water equations (integral formulation). It takes into account inertia, mass transfer, gravity, gas and wall frictions, pressure, surface tension, droplet impacts, rotational effects and is unsteady. A 2D code has been developed to implement this model. A part of the model has been verified with analytical solutions (Riemann problems and inclined lake at rest), has been confronted with the linear stability of falling liquid film and has been validated with the experiment of Hammitt et al. [1] which involves a sheared film under low-pressure steam turbine conditions.

scholarly journals Development of Automatic Equipment for Washing and Nondestructive Inspection of Stud Bolt

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
H. S. Kwak
Keyword(s):  
High Pressures ◽  
Nondestructive Inspection ◽  
Operating Conditions ◽  
Energy Utilization ◽  
Steam Turbines ◽  
Cleaning Efficiency ◽  
Automatic Equipment ◽  
Element Analysis ◽  
Pressure Steam ◽  
Screw Threads

Low-pressure steam turbines in a power plant are required to operate at high temperatures and under high pressures to achieve better energy utilization and better performance. Higher operating temperatures accelerate the rate of oxidation and sludge formation, so the steam turbine is periodically inspected including strict examination of the stud bolts, and it is necessary to clean the bolts by removing sludge from their screw threads. In the conventional cleaning process, the sludge has been removed by manual cleaning, which is labor-intensive and time-consuming. Therefore, this study developed automatic equipment for washing and nondestructive inspection of stud bolts using theoretical analysis and finite element analysis (FEA). An optimal clamp load to prevent sliding of the roller was calculated, and a structural analysis of the equipment under operating conditions was conducted. An optimal washing condition to maximize cleaning efficiency was proposed using design of the experiment and verified by performing washing test of prototype.

Bottoming Cycle Performance in Large Size Combined Cycle Power Plants—Part A: Health Monitoring System

2009 ◽  
Author(s):  
Silvio Cafaro ◽  
Alberto Traverso ◽  
Aristide F. Massardo ◽  
Roberto Bittarello
Keyword(s):  
Heat Exchanger ◽  
Steam Turbine ◽  
Measurement Errors ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Direct Result ◽  
Steam Turbines ◽  
Large Size ◽  
Performance Indexes ◽  
Pressure Steam

This research is focused on the monitoring and diagnostic of the bottoming cycle (BC) of a large size combined cycle, composed by a three pressure level HRSG (Heat Recovery Steam Generator), a three expansion level steam turbine and auxiliary pumps. An original Matlab software was developed, which is composed by two parts: the first calculates HRSG performance, while the second is focused on the calculation of the steam turbines performance, at different power plant operating conditions. In the first part a complete HRSG performance analysis is carried out: it consists of the calculation of each heat exchanger performance and health. The direct result of this analysis is the definition of Non Dimensional Performance Indexes (NDPI) for each heat exchanger, which define the instant degradation of each component, through the comparison between the “actual” and the “expected” effectiveness. The second part calculates steam turbines performance. Two NDPIs are defined: one referred to the high pressure steam turbine and the other referred to the middle-low pressure steam turbine. The performance indexes are calculated comparing the actual expansion efficiency with the expected one. The NDPI previously defined will be used to monitor plant degradation, to support plant maintenance, and to assist on-line troubleshooting. Each performance parameter is coupled with an accuracy factor, which allows to determine the best parameters to be monitored and to define the related tolerance due to measurement errors. The methodology developed has been successfully applied to historical logged data (2 years) of an existing large size (400 MW) combined cycle, demonstrating the capabilities in estimating the degradation of the BC performance throughout plant life.

Numerical and Experimental Aerodynamic Investigation of a Low Pressure Steam Turbine Module

2019 ◽  
Author(s):  
Juri Bellucci ◽  
Lorenzo Peruzzi ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
Nicola Maceli
Keyword(s):  
Steam Turbine ◽  
Three Dimensional ◽  
Low Pressure ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Experimental Results ◽  
Steam Turbines ◽  
Performance Curves ◽  
Pressure Steam ◽  
Cfd Analyses

Abstract This work aims to deepen the understanding of the aerodynamic behavior and the performance of a low pressure steam turbine module. Numerical and experimental results obtained on a three-stage low pressure steam turbine (LPT) module are presented. The selected geometry is representative of the state-of-the-art of low pressure sections for small steam turbines. The test vehicle was designed and operated in different operating conditions with dry and wet steam. Different types of measurements are performed for the global performance estimation of the whole turbine and for the detailed analysis of the flow field. Steady and unsteady CFD analyses have been performed by means of viscous, three-dimensional simulations adopting a real gas, equilibrium steam model. Measured inlet/outlet boundary conditions are used for the computations. The fidelity of the computational setup is proven by comparing computational and experimental results. Main performance curves and span-wise distributions show a good agreement in terms of both shape of curves/distributions and absolute values. Finally, an attempt is done to point out where losses are generated and the physical mechanisms involved are investigated and discussed in details.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

scholarly journals On the Lifetime Estimation of SiC Power MOSFETs for Motor Drive Applications

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 324
Author(s):  
Carmelo Barbagallo ◽  
Santi Agatino Rizzo ◽  
Giacomo Scelba ◽  
Giuseppe Scarcella ◽  
Mario Cacciato
Keyword(s):  
Electric Drive ◽  
Average Power ◽  
Estimation Procedure ◽  
General Purpose ◽  
Operating Conditions ◽  
Power Losses ◽  
Power Devices ◽  
Lifetime Estimation ◽  
Power Mosfets ◽  
Mission Profile

This work presents a step-by-step procedure to estimate the lifetime of discrete SiC power MOSFETs equipping three-phase inverters of electric drives. The stress of each power device when it is subjected to thermal jumps from a few degrees up to about 80 °C was analyzed, starting from the computation of the average power losses and the commitment of the electric drive. A customizable mission profile was considered where, by accounting the working conditions of the drive, the corresponding average power losses and junction temperatures of the SiC MOSFETs composing the inverter can be computed. The tool exploits the Coffin–Manson theory, rainflow counting, and Miner’s rule for the lifetime estimation of the semiconductor power devices. Different operating scenarios were investigated, underlying their impact on the lifetime of SiC MOSFETs devices. The lifetime estimation procedure was realized with the main goal of keeping limited computational efforts, while providing an effective evaluation of the thermal effects. The method enables us to set up any generic mission profile from the electric drive model. This gives us the possibility to compare several operating scenario of the drive and predict the worse operating conditions for power devices. Finally, although the lifetime estimation tool was applied to SiC power MOSFET devices for a general-purpose application, it can be extended to any type of power switch technology.

Analysis of Vapor Evaporation Loss in Filling Gasoline into Tank

2011 ◽  
Vol 347-353 ◽  
pp. 372-375 ◽  
Author(s):  
Wei Qiu Huang ◽  
Feng Li ◽  
Shu Hua Zhao ◽  
Jing Zhong
Keyword(s):  
Mass Transfer ◽  
Experimental System ◽  
Pilot Scale ◽  
Convective Transport ◽  
Operating Conditions ◽  
Vapor Concentration ◽  
Air Mass ◽  
Evaporation Loss ◽  
Gas Space ◽  
Gasoline Evaporation

A pilot-scale experimental system of filling gasoline into a tank was built to investigate gasoline vapor-air mass transfer in the tank gas space and the vapor evaporation loss from the tank in different operating conditions. The results showed that the higher the location of filling pipe exit inside the tank, the quicker the speed of the filling gasoline, and the higher the initial vapor concentration in the tank gas space, then the more severe the vapor-air convective transport and the larger the gasoline evaporation loss rates.

Numerical Analysis of the Heat and Mass Transfer Characteristics in an Autothermal Methane Reformer

2010 ◽  
Vol 7 (5) ◽  
Author(s):  
Joonguen Park ◽  
Shinku Lee ◽  
Sunyoung Kim ◽  
Joongmyeon Bae
Keyword(s):  
Mass Transfer ◽  
Numerical Analysis ◽  
Heat And Mass Transfer ◽  
Steam Reforming ◽  
Space Velocity ◽  
Reaction Model ◽  
Operating Conditions ◽  
Local Thermal Equilibrium ◽  
Inlet Temperature ◽  
Transfer Characteristics

This paper discusses a numerical analysis of the heat and mass transfer characteristics in an autothermal methane reformer. Assuming local thermal equilibrium between the bulk gas and the surface of the catalyst, a one-medium approach for the porous medium analysis was incorporated. Also, the mass transfer between the bulk gas and the catalyst’s surface was neglected due to the relatively low gas velocity. For the catalytic surface reaction, the Langmuir–Hinshelwood model was incorporated in which methane (CH4) is reformed to hydrogen-rich gases by the autothermal reforming (ATR) reaction. Full combustion, steam reforming, water-gas shift, and direct steam reforming reactions were included in the chemical reaction model. Mass, momentum, energy, and species balance equations were simultaneously calculated with the chemical reactions for the multiphysics analysis. By varying the four operating conditions (inlet temperature, oxygen to carbon ratio (OCR), steam to carbon ratio, and gas hourly space velocity (GHSV)), the performance of the ATR reactor was estimated by the numerical calculations. The SR reaction rate was improved by an increased inlet temperature. The reforming efficiency and the fuel conversion reached their maximum values at an OCR of 0.7. When the GHSV was increased, the reforming efficiency increased but the large pressure drop may decrease the system efficiency. From these results, we can estimate the optimal operating conditions for the production of large amounts of hydrogen from methane.

Dynamics of Developing Laminar Non-Newtonian Falling Liquid Films With Free Surface

1978 ◽  
Vol 45 (1) ◽  
pp. 19-24 ◽  
Author(s):  
V. Narayanamurthy ◽  
P. K. Sarma
Keyword(s):  
Liquid Film ◽  
Power Law ◽  
Mathematical Formulation ◽  
Liquid Films ◽  
Interfacial Shear ◽  
Newtonian Liquid ◽  
Power Law Model ◽  
Falling Liquid Film ◽  
Falling Liquid Films ◽  
Special Case

The dynamics of accelerating, laminar non-Newtonian falling liquid film is analytically solved taking into account the interfacial shear offered by the quiescent gas adjacent to the liquid film under adiabatic conditions of both the phases. The results indicate that the thickness of the liquid film for the assumed power law model of the shear deformation versus the shear stress is influenced by the index n, the modified form of (Fr/Re). The mathematical formulation of the present analysis enables to treat the problem as a general type from which the special case for Newtonian liquid films can be derived by equating the index in the power law to unity.

Using CFD to Enhance the Preliminary Design of High-Pressure Steam Turbines

2013 ◽  
Author(s):  
Juri Bellucci ◽  
Federica Sazzini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Design Tool ◽  
Tip Clearance ◽  
Large Set ◽  
Preliminary Design ◽  
Steam Turbines ◽  
High Pressure Steam ◽  
Wide Range ◽  
Pressure Steam

This paper focuses on the use of the CFD for improving a steam turbine preliminary design tool. Three-dimensional RANS analyses were carried out in order to independently investigate the effects of profile, secondary flow and tip clearance losses, on the efficiency of two high-pressure steam turbine stages. The parametric study included geometrical features such as stagger angle, aspect ratio and radius ratio, and was conducted for a wide range of flow coefficients to cover the whole operating envelope. The results are reported in terms of stage performance curves, enthalpy loss coefficients and span-wise distribution of the blade-to-blade exit angles. A detailed discussion of these results is provided in order to highlight the different aerodynamic behavior of the two geometries. Once the analysis was concluded, the tuning of a preliminary steam turbine design tool was carried out, based on a correlative approach. Due to the lack of a large set of experimental data, the information obtained from the post-processing of the CFD computations were applied to update the current correlations, in order to improve the accuracy of the efficiency evaluation for both stages. Finally, the predictions of the tuned preliminary design tool were compared with the results of the CFD computations, in terms of stage efficiency, in a broad range of flow coefficients and in different real machine layouts.

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