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.

Monitoring of HRSG Performance in Large Size Combined Cycle Power Plants

2008 ◽  
Author(s):  
Silvio Cafaro ◽  
Alberto Traverso ◽  
Aristide F. Massardo
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Measurement Errors ◽  
Power Plants ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Performance Parameter ◽  
Matlab Code ◽  
Large Size

Monitoring of all components of large size combined cycle power plants (gas turbine, HRSG, steam turbine, auxiliaries) plays a determinant role in improving plant availability, profitability and maintenance scheduling. This paper presents a research project carried out by TPG (Thermochemical Power Group) of University of Genoa in collaboration with Ansaldo Energia S.p.A. to improve existing monitoring and diagnostics procedures and to develop innovative software tools for software-aided maintenance and customer support: the first part of research is concerned with the monitoring of a three pressure level HRSG (Heat Recovery Steam Generator), which is presented in this paper. A procedure for estimating HRSG performance in large size combined cycle power plants is presented. The work consists of the development of an original Matlab code which calculates heat exchangers’ performance, at different power plant operating conditions. The Matlab code uses some parameters (areas of heat exchangers, heat transfer coefficient, heat loss, pressure drop) coming from a detailed on-design model necessary to set some parameters for the calculation. The original Matlab code was developed with a twofold objective: to calculate the actual gas path inside the HRSG starting from the available measurements, thus obtaining the current effectiveness of all the heat exchangers in the HRSG; to estimate the expected performance of each heat exchanger to be compared with the actual ones. Once the actual effectiveness and the expected effectiveness of the heat exchanger are defined, non-dimensional performance parameters suitable for degradation assessment can be defined. Such parameters will be used to monitor plant degradation, to support plant maintenance, and to assist on-line troubleshooting. As a result of the sensitivity analysis, each performance parameter is coupled with an accuracy factor. The accuracy of each performance parameter is estimated through the sensitivity analysis, 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, showing the capabilities in estimating the degradation of the HRSG throughout plant life.

Experimental Investigation Into Thermal Behaviour of Steam Turbine Components: Part 1—Temperature Measurements With Optical Probes

2012 ◽  
Author(s):  
W. F. Mohr ◽  
P. Ruffino
Keyword(s):  
Steam Turbine ◽  
Combined Cycle ◽  
Temperature Measurements ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Standard Temperature ◽  
Pressure Steam ◽  
Rotor Surface ◽  
Base Load

The first-in-time application of intensity pyrometry to measure in-situ the hot rotor surface temperature of a standard, combined cycle, intermediate pressure steam turbine is presented. The data cover a cold-start and cooling from base load. The pyrometric temperatures are compared to standard temperature measurements on static turbine parts and an upstream steam temperature measured on a thermo well. It is reported, how the applicability of pyrometry in steam turbines was assessed. Details are given about a newly developed USC autoclave, which was used to measure steam transmittance, and about the measurement of the emissivity of the rotor metal. Further the steps taken towards a steam-pyrometer are shown; how it was developed, validated in terms of its precision and lifetime in hot steam environment, and how its integration to a standard turbine was prepared.

Rotor Life Prediction and Improvement for Steam Turbines Under Cyclic Operation

2011 ◽  
Author(s):  
Damaso Checcacci ◽  
Lorenzo Cosi ◽  
Sanjay Kumar Sah
Keyword(s):  
Steam Turbine ◽  
Turbine Rotor ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Power Utility ◽  
Simplified Approach ◽  
Cyclic Operation ◽  
Combined Cycle Plant ◽  
The Impact

The evolution of the energy market is leading to a general increase in demand for cyclic operation and rapid startup capability for steam turbines utilized in power utility plants. As a consequence, turbine manufactures must optimize designs to minimize transient stress and make available to plant operators the necessary understanding of the impact of operating conditions on parts life. In addition, if continuous duty operation is not economical for an existing plant, operators considering switching to the cyclic mode need to take into account the cost associated with reduced maintenance intervals and parts replacement. This paper presents the methodologies applied to assess and optimize steam turbine rotor life. The discussion stems from the case analysis of a 60 MW steam turbine that was operated almost uninterrupted for 10 years in a combined cycle plant and was then expected to switch to cyclic operation with approx 250 startups/year. The effects of different rotor geometries on transient thermal stress/strain conditions are presented along with the consequences of startup sequence modifications for rotor life vs. on-line time. The discussion is supported by modeling details and results from transient thermomechanical FEM analyses. The possibility of a simplified approach in the form of approximate models for the analysis of such behavior on a project basis is also addressed.

Proposals to Maximize Electricity Generation From Sugar Cane in Brazil

2014 ◽  
Author(s):  
Eduardo Antonio Pina ◽  
Marcelo Modesto
Keyword(s):  
Steam Turbine ◽  
Energy Production ◽  
Combined Cycle ◽  
Back Pressure ◽  
Electricity Production ◽  
Steam Turbines ◽  
Pressure Steam ◽  
Cogeneration System ◽  
Low Efficiency ◽  
Sugarcane Industry

Brazil’s sugarcane industry has been characterized by low efficiency in energy production as it consumes large amounts of bagasse as fuel in its cogeneration system, considering its low price and abundance. The possibility of selling surplus electricity to the grid has motivated investments in improvements, such as reduction of steam demand by means of process thermal integration and double distillation systems, and employment of condensing instead of back pressure steam turbines. Four different cogeneration systems were analyzed in this work: two traditional Rankine Cycles, the first presenting back pressure steam turbine and the second featuring condensing steam turbine configuration; a BIGCC (Biomass Gasification Combined Cycle) and an altered model of the BIGCC, comprised by an extra gas turbine set operating with ethanol. Thermoeconomic analyses determining exergy based costs of electricity and ethanol for all cases were carried out. The main objective of this work is to assess the proposal to maximize electricity production from the sugarcane industry in Brazil.

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.

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.

Externally-Fired Combined Cycle Repowering of Existing Steam Plants

1993 ◽  
Author(s):  
Christian L. Vandervort ◽  
Mohammed R. Bary ◽  
Larry E. Stoddard ◽  
Steven T. Higgins
Keyword(s):  
Heat Exchanger ◽  
Steam Turbine ◽  
Gas Turbine ◽  
High Efficiency ◽  
Low Cost ◽  
Operating Experience ◽  
Capital Cost ◽  
Combined Cycle ◽  
Plant Design ◽  
Generating Capacity

The Externally-Fired Combined Cycle (EFCC) is an attractive emerging technology for powering high efficiency combined gas and steam turbine cycles with coal or other ash bearing fuels. The key near-term market for the EFCC is likely to be repowering of existing coal fueled power generation units. Repowering with an EFCC system offers utilities the ability to improve efficiency of existing plants by 25 to 60 percent, while doubling generating capacity. Repowering can be accomplished at a capital cost half that of a new facility of similar capacity. Furthermore, the EFCC concept does not require complex chemical processes, and is therefore very compatible with existing utility operating experience. In the EFCC, the heat input to the gas turbine is supplied indirectly through a ceramic heat exchanger. The heat exchanger, coupled with an atmospheric coal combustor and auxiliary components, replaces the conventional gas turbine combustor. Addition of a steam bottoming plant and exhaust cleanup system completes the combined cycle. A conceptual design has been developed for EFCC repowering of an existing reference plant which operates with a 48 MW steam turbine at a net plant efficiency of 25 percent. The repowered plant design uses a General Electric LM6000 gas turbine package in the EFCC power island. Topping the existing steam plant with the coal fueled EFCC improves efficiency to nearly 40 percent. The capital cost of this upgrade is 1,090/kW. When combined with the high efficiency, the low cost of coal, and low operation and maintenance costs, the resulting cost of electricity is competitive for base load generation.

Repowering and Retrofitting

2002 ◽  
Author(s):  
Andreas Pickard
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Free Market ◽  
Leading Edge ◽  
Project Planning ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Planning Stage ◽  
Reheat Steam ◽  
Plant Optimization

At the start of this new century, environmental regulations and free-market economics are becoming the key drivers for the electricity generating industry. Advances in Gas Turbine (GT) technology, allied with integration and refinement of Heat Recovery Steam Generators (HRSG) and Steam Turbine (ST) plant, have made Combined Cycle installations the most efficient of the new power station types. This potential can also be realized, to equal effect, by adding GT’s and HRSG’s to existing conventional steam power plants in a so-called ‘repowering’ process. This paper presents the economical and environmental considerations of retrofitting the steam turbine within repowering schemes. Changing the thermal cycle parameters of the plant, for example by deletion of the feed heating steambleeds or by modified live and reheat steam conditions to suit the combined cycle process, can result in off-design operation of the existing steam turbine. Retrofitting the steam turbine to match the combined cycle unit can significantly increase the overall cycle efficiency compared to repowering without the ST upgrade. The paper illustrates that repowering, including ST retrofitting, when considered as a whole at the project planning stage, has the potential for greater gain by allowing proper plant optimization. Much of the repowering in the past has been carried out without due regard to the benefits of re-matching the steam turbine. Retrospective ST upgrade of such cases can still give benefit to the plant owner, especially when it is realized that most repowering to date has retained an unmodified steam turbine (that first went into operation some decades before). The old equipment will have suffered deterioration due to aging and the steam path will be to an archaic design of poor efficiency. Retrofitting older generation plant with modern leading-edge steam-path technology has the potential for realizing those substantial advances made over the last 20 to 30 years. Some examples, given in the paper, of successfully retrofitted steam turbines applied in repowered plants will show, by specific solution, the optimization of the economics and benefit to the environment of the converted plant as a whole.

Detailed Numerical Study of the Main Sources of Loss and Flow Behavior in Low Pressure Steam Turbine Exhaust Hoods

2017 ◽  
Author(s):  
Dickson Munyoki ◽  
Markus Schatz ◽  
Damian M. Vogt
Keyword(s):  
Steam Turbine ◽  
Numerical Study ◽  
Flow Behavior ◽  
Low Pressure ◽  
Operating Conditions ◽  
Pressure Recovery ◽  
Exhaust Hood ◽  
Recovery Coefficient ◽  
Pressure Steam ◽  
Underlying Mechanisms

The performance of the axial-radial diffuser downstream of the last low-pressure steam turbine stages and the losses occurring subsequently within the exhaust hood directly influences the overall efficiency of a steam power plant. It is estimated that an improvement of the pressure recovery in the diffuser and exhaust hood by 10% translates into 1% of last stage efficiency [11]. While the design of axial-radial diffusers has been the object of quite many studies, the flow phenomena occurring within the exhaust hood have not received much attention in recent years. However, major losses occur due to dissipation within vortices and inability of the hood to properly diffuse the flow. Flow turning from radial to downward flow towards the condenser, especially at the upper part of the hood is essentially the main cause for this. This paper presents a detailed analysis of the losses within the exhaust hood flow for two operating conditions based on numerical results. In order to identify the underlying mechanisms and the locations where dissipation mainly occurs, an approach was followed, whereby the diffuser inflow is divided into different sectors and pressure recovery, dissipation and finally residual kinetic energy of the flow originating from these sectors is calculated at different locations within the hood. Based on this method, the flow from the topmost sectors at the diffuser inlet is found to cause the highest dissipation for both investigated cases. Upon hitting the exhaust hood walls, the flow on the upper part of the diffuser is deflected, forming complex vortices which are stretching into the condenser and interacting with flow originating from other sectors, thereby causing further swirling and generating additional losses. The detailed study of the flow behavior in the exhaust hood and the associated dissipation presents an opportunity for future investigations of efficient geometrical features to be introduced within the hood to improve the flow and hence the overall pressure recovery coefficient.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

Sign in / Sign up

Export Citation Format

Share Document