scholarly journals Comparison between 1-D and grey-box models of a SOFC

2019 ◽  
Vol 128 ◽  
pp. 01007
Author(s):  
Ramin Moradi ◽  
Andrea Di Carlo ◽  
Federico Testa ◽  
Luca Del Zotto ◽  
Enrico Bocci ◽  
...  
Keyword(s):  
Power Systems ◽  
Solid Electrolyte ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Box Model ◽  
System Level ◽  
Internal Temperature ◽  
Box Models ◽  
The Impact ◽  
D Model

Solid Oxide Fuel Cells (SOFCs) have shown unique performance in terms of greater electrical efficiency and thermochemical integrity with the power systems compared to gas turbines and internal combustion engines. Nonetheless, simple and reliable models still must be defined. In this paper, a comparisonbetween a grey-box model and a 1-D model of a SOFC is performed to understand the impact of the heat transfer inside the cell on the internal temperature distribution of the solid electrolyte. Hence, a significant internal temperature peak of the solid electrolyte is observed for a known difference between anode and cathode inlet temperatures. Indeed, it highlights the difference between the 1-D model andthe grey-box model regarding the thermal conditioning of the SOFC. Therefore, the results of this study can be used to investigate the reliability of the thermal results of box models in system-level simulations.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

Risk-Based Assessment of Unplanned Outage Events and Costs for Combined-Cycle-Plants

2012 ◽  
Author(s):  
Dale Grace ◽  
Thomas Christiansen
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Cash Flow ◽  
Gas Turbines ◽  
Operational Reliability ◽  
Combined Cycle ◽  
Maintenance Costs ◽  
Wide Range ◽  
Turbine Equipment ◽  
The Impact

Unexpected outages and maintenance costs reduce plant availability and can consume significant resources to restore the unit to service. Although companies may have the means to estimate cash flow requirements for scheduled maintenance and on-going operations, estimates for unplanned maintenance and its impact on revenue are more difficult to quantify, and a large fleet is needed for accurate assessment of its variability. This paper describes a study that surveyed 388 combined-cycle plants based on 164 D/E-class and 224 F-class gas turbines, for the time period of 1995 to 2009. Strategic Power Systems, Inc. (SPS®), manager of the Operational Reliability Analysis Program (ORAP®), identified the causes and durations of forced outages and unscheduled maintenance and established overall reliability and availability profiles for each class of plant in 3 five-year time periods. This study of over 3,000 unit-years of data from 50 Hz and 60 Hz combined-cycle plants provides insight into the types of events having the largest impact on unplanned outage time and cost, as well as the risks of lost revenue and unplanned maintenance costs which affect plant profitability. Outage events were assigned to one of three subsystems: the gas turbine equipment, heat recovery steam generator (HRSG) equipment, or steam turbine equipment, according to the Electric Power Research Institute’s Equipment Breakdown Structure (EBS). Costs to restore the unit to service for each main outage cause were estimated, as were net revenues lost due to unplanned outages. A statistical approach to estimated costs and lost revenues provides a risk-based means to quantify the impact of unplanned events on plant cash flow as a function of class of gas turbine, plant subsystem, and historical timeframe. This statistical estimate of the costs of unplanned outage events provides the risk-based assessment needed to define the range of probable costs of unplanned events. Results presented in this paper demonstrate that non-fuel operation and maintenance costs are increased by roughly 8% in a typical combined-cycle power plant due to unplanned maintenance events, but that a wide range of costs can occur in any single year.

Thermo-Fluid Modelling for Gas Turbines—Part I: Theoretical Foundation and Uncertainty Analysis

2009 ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Vishal Sethi ◽  
Stephen O. T. Ogaji ◽  
Pericles Pilidis ◽  
Riti Singh ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Simulation Software ◽  
System Level ◽  
Fluid Models ◽  
Performance Simulation ◽  
Turbine Performance ◽  
Aircraft System ◽  
The Impact ◽  
Made In

In this two-part publication, various aspects of thermo-fluid modelling for gas turbines are described and their impact on performance calculations and emissions predictions at aircraft system level is assessed. Accurate and reliable fluid modelling is essential for any gas turbine performance simulation software as it provides a robust foundation for building advanced multi-disciplinary modelling capabilities. Caloric properties for generic and semi-generic gas turbine performance simulation codes can be calculated at various levels of fidelity; selection of the fidelity level is dependent upon the objectives of the simulation and execution time constraints. However, rigorous fluid modelling may not necessarily improve performance simulation accuracy unless all modelling assumptions and sources of uncertainty are aligned to the same level. Certain modelling aspects such as the introduction of chemical kinetics, and dissociation effects, may reduce computational speed and this is of significant importance for radical space exploration and novel propulsion cycle assessment. This paper describes and compares fluid models, based on different levels of fidelity, which have been developed for an industry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles. The latter comprises the following modules: engine performance, aircraft performance, emissions prediction, and environmental impact. The work presented aims to fill the current literature gap by: (i) investigating the common assumptions made in thermo-fluid modelling for gas turbines and their effect on caloric properties and (ii) assessing the impact of uncertainties on performance calculations and emissions predictions at aircraft system level. In Part I of this two-part publication, a comprehensive analysis of thermo-fluid modelling for gas turbines is presented and the fluid models developed are discussed in detail. Common technical models, used for calculating caloric properties, are compared while typical assumptions made in fluid modelling, and the uncertainties induced, are examined. Several analyses, which demonstrate the effects of composition, temperature and pressure on caloric properties of working mediums for gas turbines, are presented. The working mediums examined include dry air and combustion products for various fuels and H/C ratios. The errors induced by ignoring dissociation effects are also discussed.

scholarly journals Analysing the Performance of Ammonia Powertrains in the Marine Environment

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7447
Author(s):  
Thomas Buckley Imhoff ◽  
Savvas Gkantonas ◽  
Epaminondas Mastorakos
Keyword(s):  
Marine Environment ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Chemical Engineering ◽  
Feasibility Studies ◽  
Internal Combustion ◽  
Alternative Fuel ◽  
System Level ◽  
Combustion Engines ◽  
Catalytic Material

This study develops system-level models of ammonia-fuelled powertrains that reflect the characteristics of four oceangoing vessels to evaluate the efficacy of ammonia as an alternative fuel in the marine environment. Relying on thermodynamics, heat transfer, and chemical engineering, the models adequately capture the behaviour of internal combustion engines, gas turbines, fuel processing equipment, and exhaust aftertreatment components. The performance of each vessel is evaluated by comparing its maximum range and cargo capacity to a conventional vessel. Results indicate that per unit output power, ammonia-fuelled internal combustion engines are more efficient, require less catalytic material, and have lower auxiliary power requirements than ammonia gas turbines. Most merchant vessels are strong candidates for ammonia fuelling if the operators can overcome capacity losses between 4% and 9%, assuming that the updated vessels retain the same range as a conventional vessel. The study also establishes that naval vessels are less likely to adopt ammonia powertrains without significant redesigns. Ammonia as an alternative fuel in the marine sector is a compelling option if the detailed component design continues to show that the concept is practically feasible. The present data and models can help in such feasibility studies for a range of vessels and propulsion technologies.

Evaluation of Spray Performance of Pyrolysis Oil

2019 ◽  
Author(s):  
Sangsig Yun ◽  
Minji Choi ◽  
Ashwani Kumar
Keyword(s):  
Power Systems ◽  
Physical Properties ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Fossil Fuels ◽  
Chemical Properties ◽  
Pyrolysis Oil ◽  
Cheap Alternative ◽  
Industrial Gas Turbines ◽  
Pyrolysis Oils

Abstract Pyrolysis oil has become an important subject of research as it is considered to be a potential environmentally friendly and cheap alternative to conventional fossil fuels. Unfortunately, due to the significant differences of the chemical and physical properties of pyrolysis oil than that of fossil fuels, the deployment of pyrolysis oil in existing power systems such as gas turbines and internal combustion engines has been highly restricted. Thus, major research on pyrolysis oil has been conducted to overcome these challenges related to the unfavorable physical and chemical properties of pyrolysis oil. This paper reports experimental work on the effects of physical properties of the pyrolysis oil on spray performance of nozzles. Effort to evaluate the spray performance by using different types of atomizers has been made as well. Laser based diagnostics was applied to obtain qualitative comparisons spray characteristics of various pyrolysis oils. Experimental data such as the distribution of fuel droplet sizes and overall spray shapes was analyzed, which could provide valuable guidelines to design fuel nozzles. Lastly, the paper will also present NRC’s plans to accelerate the deployment of such pyrolysis oils in industrial gas turbines.

scholarly journals Benefit Analysis of Long-Duration Energy Storage in Power Systems with High Renewable Energy Shares

2020 ◽  
Vol 8 ◽  
Author(s):  
Jiazi Zhang ◽  
Omar J. Guerra ◽  
Joshua Eichman ◽  
Matthew A. Pellow
Keyword(s):  
Renewable Energy ◽  
Energy Storage ◽  
Power Systems ◽  
Production Cost ◽  
Cost Model ◽  
Cost Savings ◽  
System Level ◽  
Long Duration ◽  
Storage Technologies ◽  
The Impact

The integration of high shares of variable renewable energy raises challenges for the reliability and cost-effectiveness of power systems. The value of long-duration energy storage, which helps address variability in renewable energy supply across days and seasons, is poised to grow significantly as power systems shift to larger shares of variable generation such as wind and solar. This study explores the system-level services and associated benefits of long-duration energy storage on the 2050 Western Interconnection (WI). The operation of the future WI system with 85% renewable penetration is simulated using a two-stage production cost model. The impact of long duration energy storage on systemwide operations is examined for the 2050 WI system, using a range of round-trip efficiencies corresponding to four different energy storage technologies. The analysis projects the energy storage dispatch profile, system-wide production cost savings (from both diurnal and seasonal operation), and impacts on generation mix, and change in renewable generation curtailment.

Towards Visualisation of Capacity, Bearing Thrust Load and Reaction Variation With Aerofoil Skew in a Gas Turbine

2019 ◽  
Author(s):  
Karthik Srinivasan ◽  
Soumyik K. Bhaumik ◽  
Lakshmanan Valliappan
Keyword(s):  
Gas Turbines ◽  
System Level ◽  
Skew Angle ◽  
Small Deviations ◽  
Pressure Drops ◽  
Performance Targets ◽  
Multi Stage ◽  
The Individual ◽  
The Impact ◽  
Thrust Load

Abstract The requirements in the design of aerofoils for gas turbines are not limited to only meeting the aerothermal performance. A typical scenario for a turbine is to understand the impact of aerofoil skew on capacity, reaction and bearing thrust load. A means to achieve the target capacity could be by skewing the aerofoil. This, however, changes the stage reaction which in turn impacts the bearing thrust load. In the case of a multi stage turbine, the work split between the stages impacts the ratio of pressure drops and hence the contribution of the individual aerofoil rows to the overall capacity and bearing thrust load variation. This paper deals with a generic approach to visualise the variation of capacity and bearing thrust load with aerofoil skew for a stage of interest along with the Constraints that could be potentially imposed on the stage. This methodology provides a useful mapping between parameters which are directly under the aerodynamicist’s control (i.e. aerofoil skew) to module- and system-level behaviours (i.e. capacity, bearing thrust load). It thereby allows informed choices to be made throughout the design process which deliver the turbine aerodynamic performance targets whilst respecting wider system-level constraints. Suitable optimisation within this design space will yield a design that is fundamentally robust to small deviations in skew angle. Additionally, qualitative variation of the gas path static pressure and reaction based on aerofoil skews are explained pictorially to facilitate the understanding.

scholarly journals Quantifying atmospheric transport, chemistry, and mixing using a new trajectory-box model and a global atmospheric-chemistry GCM

2009 ◽  
Vol 2 (2) ◽  
pp. 267-280 ◽  
Author(s):  
H. Riede ◽  
P. Jöckel ◽  
R. Sander
Keyword(s):  
Atmospheric Chemistry ◽  
General Circulation ◽  
Initial Conditions ◽  
Box Model ◽  
Physical Parameters ◽  
Mixing Processes ◽  
Trajectory Model ◽  
Quantification Method ◽  
The Impact ◽  
D Model

Abstract. We present a novel method for the quantification of transport, chemistry, and mixing along atmospheric trajectories based on a consistent model hierarchy. The hierarchy consists of the new atmospheric-chemistry trajectory-box model CAABA/MJT and the three-dimensional (3-D) global ECHAM/MESSy atmospheric-chemistry (EMAC) general circulation model. CAABA/MJT employs the atmospheric box model CAABA in a configuration using the atmospheric-chemistry submodel MECCA (M), the photochemistry submodel JVAL (J), and the new trajectory submodel TRAJECT (T), to simulate chemistry along atmospheric trajectories, which are provided offline. With the same chemistry submodels coupled to the 3-D EMAC model and consistent initial conditions and physical parameters, a unique consistency between the two models is achieved. Since only mixing processes within the 3-D model are excluded from the model consistency, comparisons of results from the two models allow to separate and quantify contributions of transport, chemistry, and mixing along the trajectory pathways. Consistency of transport between the trajectory-box model CAABA/MJT and the 3-D EMAC model is achieved via calculation of kinematic trajectories based on 3-D wind fields from EMAC using the trajectory model LAGRANTO. The combination of the trajectory-box model CAABA/MJT and the trajectory model LAGRANTO can be considered as a Lagrangian chemistry-transport model (CTM) moving isolated air parcels. The procedure for obtaining the necessary statistical basis for the quantification method is described as well as the comprehensive diagnostics with respect to chemistry. The quantification method presented here allows to investigate the characteristics of transport, chemistry, and mixing in a grid-based 3-D model. The analysis of chemical processes within the trajectory-box model CAABA/MJT is easily extendable to include, for example, the impact of different transport pathways or of mixing processes onto chemistry. Under certain prerequisites described here, the results can be used to complement observations with detailed information about the history of observed air masses.

Implementing Thermal Management Modeling Into SOFC System Level Design

2010 ◽  
Vol 8 (2) ◽  
Author(s):  
K. J. Kattke ◽  
R. J. Braun
Keyword(s):  
Power Systems ◽  
Thermal Management ◽  
System Modeling ◽  
Management Strategies ◽  
System Level ◽  
System Level Design ◽  
Gas Temperature ◽  
Process Gas ◽  
Level Design ◽  
The Impact

Effective thermal management is critical to the successful design of small (<10 kW) solid oxide fuel cell (SOFC) power systems. While separate unit processes occur within each component of the system, external heat transport from/to components must be optimally managed and taken into account in system-level design. In this paper, we present a modeling approach that captures thermal interactions among hot zone components and couples this information with system process design. The resulting thermal model is then applied to a mobile SOFC power system concept in the 1–2 kW range to enable a better understanding of how component heat loss affects process gas temperature and flow requirements throughout the flowsheet. The thermal performance of the system is examined for various thermal management strategies that involve altering the convective and radiative heat transfer in the enclosure. The impact of these measures on internal temperature distributions within the cell-stack is also presented. A comparison with the results from traditional adiabatic, zero-dimensional thermodynamic system modeling reveals that oxidant flow requirements can be overpredicted by as much as 204%, resulting in oversizing of recuperator heat duty by 221%, and that important design constraints, such as the magnitude of the maximum cell temperature gradient within the stack, are underpredicted by over 24%.

Implementing Thermal Management Modeling Into SOFC System-Level Design

2010 ◽  
Author(s):  
K. J. Kattke ◽  
R. J. Braun
Keyword(s):  
Power Systems ◽  
Thermal Management ◽  
System Modeling ◽  
Management Strategies ◽  
System Level ◽  
System Level Design ◽  
Gas Temperature ◽  
Process Gas ◽  
Level Design ◽  
The Impact

Effective thermal management is critical to the successful design of small (&lt;10 kW) solid oxide fuel cell (SOFC) power systems. While separate unit processes occur within each component of the system, external heat transport from or to components must be optimally managed and taken into account in system-level design. In this paper, we present a modeling approach that captures thermal interactions among hot zone components and couples this information with system process design. The resulting thermal model is then applied to a mobile SOFC power system concept in the 1–2 kW range to enable a better understanding of how component heat loss affects process gas temperature and flow requirements throughout the flowsheet. The thermal performance of the system is examined for various thermal management strategies that involve altering the convective and radiative heat transfer in the enclosure. The impact of these measures on internal temperature distributions within the cell-stack is also presented. A comparison with results from traditional adiabatic, zero-dimensional thermodynamic system modeling reveals that oxidant flow requirements can be over-predicted by as much as 110% and that important design constraints, such as the magnitude of the maximum cell temperature gradient within the stack, are under-predicted by over 40%.

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