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The detrimental effects of the catalyst degradation on the overall envisaged lifetime of low-temperature proton-exchange membrane fuel cells (LT-PEMFCs) represent a significant challenge towards further lowering platinum loadings and simultaneously achieving a long cycle life. The elaborated physically based modeling of the degradation processes is thus an invaluable step in elucidating causal interaction between fuel cell design, its operating conditions, and degradation phenomena. However, many parameters need to be determined based on experimental data to ensure plausible simulation results of the catalyst degradation models, which proves to be challenging with the in situ measurements. To fill this knowledge gap, this paper demonstrates the application of a mechanistically based PEMFC modeling framework, comprising real-time capable fuel cell performance, and platinum and carbon support degradation models, to model transient CO2 release rates in the LT-PEMFCs with the consistent calibration of reaction rate parameters under multiple different accelerated stress tests at once. The results confirm the credibility of the physical and chemical modeling basis of the proposed modeling framework, as well as its prediction and extrapolation capabilities. This is confirmed by an increase of only 29% of root mean square deviations values when using a model calibrated on all three data sets at once in comparison to a model calibrated on only one data set. Furthermore, the unique identifiability and interconnection of individual model calibration parameters are determined via Fisher information matrix analysis. This analysis enables optimal reduction of the set of calibration parameters, which results in the speed up of both the calibration process and the general simulation time while retaining the full extrapolation capabilities of the framework.
Andraž Kravos; Ambrož Kregar; Kurt Mayer; Viktor Hacker; Tomaž Katrašnik. Identifiability Analysis of Degradation Model Parameters from Transient CO2 Release in Low-Temperature PEM Fuel Cell under Various AST Protocols. Energies 2021, 14, 4380 .
AMA StyleAndraž Kravos, Ambrož Kregar, Kurt Mayer, Viktor Hacker, Tomaž Katrašnik. Identifiability Analysis of Degradation Model Parameters from Transient CO2 Release in Low-Temperature PEM Fuel Cell under Various AST Protocols. Energies. 2021; 14 (14):4380.
Chicago/Turabian StyleAndraž Kravos; Ambrož Kregar; Kurt Mayer; Viktor Hacker; Tomaž Katrašnik. 2021. "Identifiability Analysis of Degradation Model Parameters from Transient CO2 Release in Low-Temperature PEM Fuel Cell under Various AST Protocols." Energies 14, no. 14: 4380.
It has been shown previously that the governing equations defining continuum level processes in electrochemical cells can be mapped into appropriate extended equivalent circuits, also known as transmission line models (TLMs). Here we present a derivation which results in direct construction of a TLM from the widely used concentrated solution theory (CST) for porous electrodes originally proposed by Newman. The final result of derivation is a set of equations that directly connect the main parameters of CST for porous electrode (electrolyte conductivity, transport number, concentration, thermodynamic factor, chemical diffusion coefficient, porosity) and the main elements of corresponding TLM (resistances of active and inactive ions and chemical capacitance). The constructed TLM is applied to three standard porous electrode cases found in devices such as batteries, fuel cell and supercapacitors: insertion electrodes, faradic reaction at electrode-electrolyte interface and blocking electrodes. For all three cases, the derived TLMs are justified by a direct comparison of their output with the output of the corresponding analytical expression for impedance response of CST for porous electrodes.
Klemen Zelič; Tomaž Katrašnik; Miran Gaberšček. Derivation of Transmission Line Model from the Concentrated Solution Theory (CST) for Porous Electrodes. Journal of The Electrochemical Society 2021, 168, 070543 .
AMA StyleKlemen Zelič, Tomaž Katrašnik, Miran Gaberšček. Derivation of Transmission Line Model from the Concentrated Solution Theory (CST) for Porous Electrodes. Journal of The Electrochemical Society. 2021; 168 (7):070543.
Chicago/Turabian StyleKlemen Zelič; Tomaž Katrašnik; Miran Gaberšček. 2021. "Derivation of Transmission Line Model from the Concentrated Solution Theory (CST) for Porous Electrodes." Journal of The Electrochemical Society 168, no. 7: 070543.
Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an external input fuel is provided. Hence, complementing syngas with traditional fuels, like natural gas, becomes a necessity. In this work, an experimental methodology is proposed, aiming at the quantification of the impact of the use of both natural gas and syngas in spark ignition (SI) engines on performance and emissions. The main research questions focus on investigating brake thermal efficiency (BTE), power derating, and pollutant emission (NOx, CO, THC, CO2) formation, offering quantitative findings that present the basis for engine optimization procedures. Experimental measurements were performed on a Toyota 4Y-E engine (a 4-cylinders, 4-stroke spark ignition engine) at partial load (10 kW) under different syngas energy shares (SES) and at four different spark ignition timings (10°, 25°, 35° and 45° BTDC). Results reveal that the impact of the different fuel mixtures on BTE is negligible if compared to the influence of spark advance variation on BTE. On the other hand, power derating has proven to be a limiting factor and becomes more prominent with increasing SES. An increasing SES also resulted in an increase of CO and CO2 emissions, while NOx and THC emissions decreased with increasing SES.
Carlo Caligiuri; Urban Žvar Baškovič; Massimiliano Renzi; Tine Seljak; Samuel Rodman Oprešnik; Marco Baratieri; Tomaž Katrašnik. Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion. Energies 2021, 14, 3688 .
AMA StyleCarlo Caligiuri, Urban Žvar Baškovič, Massimiliano Renzi, Tine Seljak, Samuel Rodman Oprešnik, Marco Baratieri, Tomaž Katrašnik. Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion. Energies. 2021; 14 (12):3688.
Chicago/Turabian StyleCarlo Caligiuri; Urban Žvar Baškovič; Massimiliano Renzi; Tine Seljak; Samuel Rodman Oprešnik; Marco Baratieri; Tomaž Katrašnik. 2021. "Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion." Energies 14, no. 12: 3688.
Multi-scale and multi-domain mathematical models capable of modelling main electrochemical reactions, side reactions and heat generation can reduce the time and cost of lithium-ion battery development and deployment, since these processes decisively influence performance, durability and safety of batteries. Experimental evidences clearly indicate the importance of the interplay between electric and thermal boundary conditions, cell design and applied materials, side reactions as well as safety implications of batteries, which are not yet captured to a sufficient level by simulations models. As an answer to this challenge, the paper presents an advanced multi-scale battery modelling framework that can be seamlessly integrated into multi-domain models. The key hypothesis is that nanoscopic transport phenomena and resulting heat generation decisively influence the entire chain of mechanisms that can lead to the outbreak of the thermal runaway. This is confirmed by developing a multi-scale battery modelling framework that is based on the continuous modelling approach featuring more consistent virtual representation of the electrode topology and incorporating the coupled chain of models for heat generations and side reactions. As a result, the battery modelling framework intuitively yet insightfully elucidates the entire chain of phenomena from electric and thermal boundary conditions, over cell design and properties of applied materials to solid electrolyte interphase growth, its decomposition and subsequent side reactions at the anode, cathode and the electrolyte that lead to the thermal runaway. One of key results comprises multi-level main and side reaction driven heat transfer cross-talk between the anode and the cathode. Therefore, the presented advanced multi-scale battery modelling framework represents a contribution to the advanced virtual development of batteries thereby contributing to tailoring battery design to a specific application.
Tomaž Katrašnik; Igor Mele; Klemen Zelič. Multi-scale modelling of Lithium-ion batteries: From transport phenomena to the outbreak of thermal runaway. Energy Conversion and Management 2021, 236, 114036 .
AMA StyleTomaž Katrašnik, Igor Mele, Klemen Zelič. Multi-scale modelling of Lithium-ion batteries: From transport phenomena to the outbreak of thermal runaway. Energy Conversion and Management. 2021; 236 ():114036.
Chicago/Turabian StyleTomaž Katrašnik; Igor Mele; Klemen Zelič. 2021. "Multi-scale modelling of Lithium-ion batteries: From transport phenomena to the outbreak of thermal runaway." Energy Conversion and Management 236, no. : 114036.
Determination of the optimal design of experiments that enables efficient parametrisation of fuel cell (FC) model with a minimum parametrisation data-set is one of the key prerequisites for minimizing costs and effort of the parametrisation procedure. To efficiently tackle this challenge, the paper present an innovative methodology based on the electrochemical FC model, parameter sensitivity analysis and application of D-optimal design plan. Relying on this consistent methodological basis the paper answers fundamental questions: a) on a minimum required data-set to optimally parametrise the FC model and b) on the impact of reduced space of operational points on identifiability of individual calibration parameters. Results reveal that application of D-optimal DoE enables enhancement of calibration parameters information resulting in up to order of magnitude lower relative standard errors on smaller data-sets. In addition, it was shown that increased information and thus identifiability, inherently leads to improved robustness of the FC electrochemical model.
Andraž Kravos; Daniel Ritzberger; Christoph Hametner; Stefan Jakubek; Tomaž Katrašnik. Methodology for efficient parametrisation of electrochemical PEMFC model for virtual observers: Model based optimal design of experiments supported by parameter sensitivity analysis. International Journal of Hydrogen Energy 2020, 46, 13832 -13844.
AMA StyleAndraž Kravos, Daniel Ritzberger, Christoph Hametner, Stefan Jakubek, Tomaž Katrašnik. Methodology for efficient parametrisation of electrochemical PEMFC model for virtual observers: Model based optimal design of experiments supported by parameter sensitivity analysis. International Journal of Hydrogen Energy. 2020; 46 (26):13832-13844.
Chicago/Turabian StyleAndraž Kravos; Daniel Ritzberger; Christoph Hametner; Stefan Jakubek; Tomaž Katrašnik. 2020. "Methodology for efficient parametrisation of electrochemical PEMFC model for virtual observers: Model based optimal design of experiments supported by parameter sensitivity analysis." International Journal of Hydrogen Energy 46, no. 26: 13832-13844.
The chemical degradation of the perfluorinated sulfonic acid (PFSA) ion-exchange membrane as a result of an attack from a radical species, originating as a by-product of the oxygen reduction reaction, represents a significant limiting factor in a wider adoption of low-temperature proton exchange membrane fuel cells (LT-PEMFCs). The efficient mathematical modeling of these processes is therefore a crucial step in the further development of proton exchange membrane fuel cells. Starting with an extensive kinetic modeling framework, describing the whole range of chemical processes leading to the membrane degradation, we use the mathematical method of sensitivity analysis to systematically reduce the number of both chemical species and reactions needed to efficiently and accurately describe the chemical degradation of the membrane. The analysis suggests the elimination of chemical reactions among the radical species, which is supported by the physicochemical consideration of the modeled reactions, while the degradation of Nafion backbone can be significantly simplified by lumping several individual species concentrations. The resulting reduced model features only 12 species coupled by 8 chemical reactions, compared to 19 species coupled by 23 reactions in the original model. The time complexity of the model, analyzed on the basis of its stiffness, however, is not significantly improved in the process. Nevertheless, the significant reduction in the model system size and number of parameters represents an important step in the development of a computationally efficient coupled model of various fuel cell degradation processes. Additionally, the demonstrated application of sensitivity analysis method shows a great potential for further use in the optimization of models of operation and degradation of fuel cell components.
Ambrož Kregar; Philipp Frühwirt; Daniel Ritzberger; Stefan Jakubek; Tomaž Katrašnik; Georg Gescheidt. Sensitivity Based Order Reduction of a Chemical Membrane Degradation Model for Low-Temperature Proton Exchange Membrane Fuel Cells. Energies 2020, 13, 5611 .
AMA StyleAmbrož Kregar, Philipp Frühwirt, Daniel Ritzberger, Stefan Jakubek, Tomaž Katrašnik, Georg Gescheidt. Sensitivity Based Order Reduction of a Chemical Membrane Degradation Model for Low-Temperature Proton Exchange Membrane Fuel Cells. Energies. 2020; 13 (21):5611.
Chicago/Turabian StyleAmbrož Kregar; Philipp Frühwirt; Daniel Ritzberger; Stefan Jakubek; Tomaž Katrašnik; Georg Gescheidt. 2020. "Sensitivity Based Order Reduction of a Chemical Membrane Degradation Model for Low-Temperature Proton Exchange Membrane Fuel Cells." Energies 13, no. 21: 5611.
To achieve a near zero emission footprint of combustion in power generation, introduction of fuels with low global warming potential, namely low-carbon or carbon neutral fuels and simultaneous reduction of harmful emissions through implementation of advanced combustion concepts is necessary. The study addresses this challenge experimentally by proposing a new approach which combines the benefits of highly oxygenated waste derived fuels, here represented by glycerol, and an introduction of external exhaust gasses recirculation (EGR) aimed for further reduction of NOx emissions. Thus, the recognized role of the high oxygen content in glycerol can positively influence the well-known penalties of EGR, which are commonly perceivable through elevated CO and soot emissions. The measurements were performed with an experimental gas turbine equipped with an exhaust heat regeneration system and feedback loop for 8% and 13% EGR content in compressor intake air. The proposed system layout represents a technically viable and cost-efficient approach for upgrading existent gas turbine setups with a goal to improve their emission footprint. Results confirm that with 8% and 13% EGR rate, NOx, CO and soot can be reduced simultaneously, thus improving the CO- NOx and soot- NOx trade off approximately 2-fold for each species. Additionally, underlying phenomena responsible for observed improvements while increasing EGR rate are identified as an increased soot reactivity, a competing effect of EGR related dilution and an increased primary air temperature together with spray related parameters linked to low stoichiometric ratio of glycerol.
Žiga Rosec; Tomaž Katrašnik; Urban Žvar Baškovič; Tine Seljak. Exhaust gas recirculation with highly oxygenated fuels in gas turbines. Fuel 2020, 278, 118285 .
AMA StyleŽiga Rosec, Tomaž Katrašnik, Urban Žvar Baškovič, Tine Seljak. Exhaust gas recirculation with highly oxygenated fuels in gas turbines. Fuel. 2020; 278 ():118285.
Chicago/Turabian StyleŽiga Rosec; Tomaž Katrašnik; Urban Žvar Baškovič; Tine Seljak. 2020. "Exhaust gas recirculation with highly oxygenated fuels in gas turbines." Fuel 278, no. : 118285.
The first EU Renewable Energy Directive (RED) served as an effective push for world-wide research efforts on biofuels and bioliquids, i.e. liquid fuels for energy purposes other than for transport, including electricity, heating, and cooling, which are produced from biomass. In December 2018 the new RED II was published in the Official Journal of the European Union. Therefore, it is now the right time to provide a comprehensive overview of achievements and practices that were developed within the current perspective. To comply with this objective, the present study focuses on a comprehensive and systematic technical evaluation of all key aspects of the different distributed energy generation pathways using bioliquids in reciprocating engines and micro gas turbines that were overseen by these EU actions. Methodologically, the study originates from the analyses of feedstock and fuel processing technologies, which decisively influence fuel properties. The study systematically and holistically highlights the utilisation of these bioliquids in terms of fuel property specific challenges, required engine adaptations, and equipment durability, culminating in analyses of engine performance and emissions. In addition, innovative proposals and future opportunities for further technical improvements in the whole production-consumption cycle are presented, thus serving as a guideline for upcoming research and development activities in the fast-growing area of bioliquids. Additionally, the paper systematically addresses opportunities for the utilisation of waste streams, emerging from the ever increasing circular use of materials and resources. With this, the present review provides the sorely needed link between past efforts, oriented towards the exploitation of bio-based resources for power generation, and the very recent zero-waste oriented society that will require a realistic exploitation plan for residuals originating from intensive material looping.
T. Seljak; M. Buffi; A. Valera-Medina; C.T. Chong; D. Chiaramonti; T. Katrašnik. Bioliquids and their use in power generation – A technology review. Renewable and Sustainable Energy Reviews 2020, 129, 109930 .
AMA StyleT. Seljak, M. Buffi, A. Valera-Medina, C.T. Chong, D. Chiaramonti, T. Katrašnik. Bioliquids and their use in power generation – A technology review. Renewable and Sustainable Energy Reviews. 2020; 129 ():109930.
Chicago/Turabian StyleT. Seljak; M. Buffi; A. Valera-Medina; C.T. Chong; D. Chiaramonti; T. Katrašnik. 2020. "Bioliquids and their use in power generation – A technology review." Renewable and Sustainable Energy Reviews 129, no. : 109930.
The reduction and prevention of degradation effects of proton exchange membrane fuel cells calls for precise on-line monitoring and control tools such as coupled virtual observers. To present significant progress in the area of computationally fast electrochemical models used in observer applications, this paper provides the derivation of a zero-dimensional thermodynamically consistent electrochemical model for proton exchange membrane fuel cells performance modelling and control. The model is further extended to accommodate the transport of gaseous species along the channel and through gas diffusion layer, yielding a quasi-one-dimensional electrochemical model. In addition, the presented work features the determination of an optimal set of calibration parameters proposed and based on mathematical and physical rationale, which is further supported with parameter sensitivity analysis. Multiple validation steps against polarisation curves at different operational points confirm the capability of the newly developed model to replicate experimental data. Furthermore, investigation in models generalisation capabilities shows that the model exhibits very good extrapolation capabilities for operation points outside the calibrated variation space of parameters. Additionally, the newly developed model can be successfully parametrised with little effort on a small calibration data set. These features position the proposed modelling framework as a beyond state-of-the-art model for virtual observers.
Andraž Kravos; Daniel Ritzberger; Gregor Tavc̆ar; Christoph Hametner; Stefan Jakubek; Tomaz̆ Katras̆nik. Thermodynamically consistent reduced dimensionality electrochemical model for proton exchange membrane fuel cell performance modelling and control. Journal of Power Sources 2020, 454, 227930 .
AMA StyleAndraž Kravos, Daniel Ritzberger, Gregor Tavc̆ar, Christoph Hametner, Stefan Jakubek, Tomaz̆ Katras̆nik. Thermodynamically consistent reduced dimensionality electrochemical model for proton exchange membrane fuel cell performance modelling and control. Journal of Power Sources. 2020; 454 ():227930.
Chicago/Turabian StyleAndraž Kravos; Daniel Ritzberger; Gregor Tavc̆ar; Christoph Hametner; Stefan Jakubek; Tomaz̆ Katras̆nik. 2020. "Thermodynamically consistent reduced dimensionality electrochemical model for proton exchange membrane fuel cell performance modelling and control." Journal of Power Sources 454, no. : 227930.
We present a model and web-based tool for rapid and efficient prediction and rationalization of chemical membrane degradation in PEMFCs including protection mechanisms.
Philipp Frühwirt; Ambrož Kregar; Jens T. Törring; Tomaž Katrašnik; Georg Gescheidt. Holistic approach to chemical degradation of Nafion membranes in fuel cells: modelling and predictions. Physical Chemistry Chemical Physics 2020, 22, 5647 -5666.
AMA StylePhilipp Frühwirt, Ambrož Kregar, Jens T. Törring, Tomaž Katrašnik, Georg Gescheidt. Holistic approach to chemical degradation of Nafion membranes in fuel cells: modelling and predictions. Physical Chemistry Chemical Physics. 2020; 22 (10):5647-5666.
Chicago/Turabian StylePhilipp Frühwirt; Ambrož Kregar; Jens T. Törring; Tomaž Katrašnik; Georg Gescheidt. 2020. "Holistic approach to chemical degradation of Nafion membranes in fuel cells: modelling and predictions." Physical Chemistry Chemical Physics 22, no. 10: 5647-5666.
High temperature proton exchange membrane fuel cells (HT-PEMFCs) are a promising and emerging technology, which enable highly efficient, low-emission, small-scale electricity and heat generation. The simultaneous reduction in production costs and prolongation of service life are considered as major challenges toward their wider market adoption, which calls for the application of predictive virtual tools during their development process. To present significant progress in the addressed area, this paper introduces an innovative real-time capable system-level modeling framework based on the following: (a) a mechanistic spatially and temporally resolved model of HT-PEMFC operation, and (b) a degradation modeling framework based on interacting individual cathode platinum degradation mechanisms. Additional innovative contributions arise from a consistent consideration of the varying particle size distribution in the transient fuel cell operating regime. The degradation modeling framework interactively considers the carbon and platinum oxidation phenomena, and platinum dissolution, redeposition, detachment, and agglomeration; hence, covering the entire causal chain of these phenomena. Presented results confirm capability of the modeling framework to accurately simulate the platinum particle size redistribution. Results clearly indicate more pronounced platinum particle growth towards the end of the channel since humidity is the main precursor of oxidation reactions. In addition, innovative modeling framework elucidate contributions of agglomeration, which is more pronounced at voltage cycling, and Ostwald ripening, which is more pronounced at higher voltages, to the platinum particles growth. These functionalities position the proposed modeling framework as a beyond state-of-the-art tool for model-supported development of the advanced clean energy conversion technologies.
Ambrož Kregar; Gregor Tavčar; Andraž Kravos; Tomaž Katrašnik. Predictive system-level modeling framework for transient operation and cathode platinum degradation of high temperature proton exchange membrane fuel cells. Applied Energy 2020, 263, 114547 .
AMA StyleAmbrož Kregar, Gregor Tavčar, Andraž Kravos, Tomaž Katrašnik. Predictive system-level modeling framework for transient operation and cathode platinum degradation of high temperature proton exchange membrane fuel cells. Applied Energy. 2020; 263 ():114547.
Chicago/Turabian StyleAmbrož Kregar; Gregor Tavčar; Andraž Kravos; Tomaž Katrašnik. 2020. "Predictive system-level modeling framework for transient operation and cathode platinum degradation of high temperature proton exchange membrane fuel cells." Applied Energy 263, no. : 114547.
The paper proposes an advanced continuum level modelling framework characterized by a more consistent virtual representation of electrode topology to enhance prediction capability and generality of porous electrode theory based models. The proposed modelling framework, therefore, establishes the missing link between the mesoscopic scale with a detailed 3D representation of electrode topology and the continuum single cell scale, where interrelation to the real electrode topology was missing. This link is established by elaborating a unified approach for modelling materials with significantly different topologies of active material by virtually creating agglomerates, representing secondary particles, from primary particles. Proposed approach relies on multi-particle size distribution of primary particles and particle-to-particle connectivity. Generality of the proposed modelling framework is demonstrated by simulating LFP and NMC materials featuring significantly different electrode topologies by the same modelling framework while adapting only virtual representation of electrode topologies and intrinsic material properties. Credibility of the proposed modelling framework is confirmed through good agreement with experimental results for various discharge tests. Insightful simulation results also reveal background of the topologically driven low Li utilization at high current densities of the LFP material and topologically driven voltage response difference during the memory effect of different LFP materials.
Igor Mele; Ivo Pačnik; Klemen Zelič; Jože Moškon; Tomaž Katrašnik. Advanced Porous Electrode Modelling Framework Based on More Consistent Virtual Representation of the Electrode Topology. Journal of The Electrochemical Society 2020, 167, 060531 .
AMA StyleIgor Mele, Ivo Pačnik, Klemen Zelič, Jože Moškon, Tomaž Katrašnik. Advanced Porous Electrode Modelling Framework Based on More Consistent Virtual Representation of the Electrode Topology. Journal of The Electrochemical Society. 2020; 167 (6):060531.
Chicago/Turabian StyleIgor Mele; Ivo Pačnik; Klemen Zelič; Jože Moškon; Tomaž Katrašnik. 2020. "Advanced Porous Electrode Modelling Framework Based on More Consistent Virtual Representation of the Electrode Topology." Journal of The Electrochemical Society 167, no. 6: 060531.
The current work investigates the impact of a paraffinic fuel on combustion and emissions of a diesel engine, examining alternative injection strategies for the full exploitation of the fuel characteristics. The paraffinic fuel used was the HVO (Hydrotreated Vegetable Oil) produced by Neste Oil with the brand name NEXBTL. The study was conducted on a light-duty turbocharged and aftercooled common-rail diesel engine, with both HVO and a conventional diesel fuel. Four steady-state operating points were examined, at low and medium engine speeds (1500 and 3000 rpm) and loads (35 and 100 Nm), typical of daily driving of a passenger car. The key contribution of the study is a comprehensive analysis of the phenomena influencing the crank angle resolved in-cylinder parameters, as well as interlinking the effects of different variations of injection pressure (default and 300 bar higher), pilot injection timing (default and ± 5°CA) and main injection timing (default and ± 2°CA) on gaseous emissions and particulate matter (PM). The findings have shown that at default engine settings the use of HVO results in up to 40% reduction of engine-out PM and HC emissions without appreciable changes in NOx emissions. The significant reduction of engine-out PM levels, facilitates the adoption of measures for NOx emissions limitation. The latter are reduced by up to 20% when the main injection timing is retarded (by 2° CA in the present study), while PM emissions are still kept well below the respective diesel fuel levels.
Athanasios Dimitriadis; Tine Seljak; Rok Vihar; Urban Žvar Baškovič; Athanasios Dimaratos; Stella Bezergianni; Zissis Samaras; Tomaž Katrašnik. Improving PM-NOx trade-off with paraffinic fuels: A study towards diesel engine optimization with HVO. Fuel 2019, 265, 116921 .
AMA StyleAthanasios Dimitriadis, Tine Seljak, Rok Vihar, Urban Žvar Baškovič, Athanasios Dimaratos, Stella Bezergianni, Zissis Samaras, Tomaž Katrašnik. Improving PM-NOx trade-off with paraffinic fuels: A study towards diesel engine optimization with HVO. Fuel. 2019; 265 ():116921.
Chicago/Turabian StyleAthanasios Dimitriadis; Tine Seljak; Rok Vihar; Urban Žvar Baškovič; Athanasios Dimaratos; Stella Bezergianni; Zissis Samaras; Tomaž Katrašnik. 2019. "Improving PM-NOx trade-off with paraffinic fuels: A study towards diesel engine optimization with HVO." Fuel 265, no. : 116921.
System level simulations, which are gaining on importance in the product concept design process and in the “Hardware‐in‐the‐Loop” (HiL) applications, require models that feature high level of accuracy, high level of prediction capability and short computational times. This paper presents an innovative mechanistic quasi 3D model capable of real time computation of steady state and transient fuel cell operation. This model relies on a hybrid 3D analytic‐numerical model (HAN) approach, which models species transport by taking 1D numerical model for pipe gas‐flow and superimposing onto it a 2D analytic solution for concentration and velocity distribution in the plane perpendicular to the gas‐flow. The main innovative contribution of this paper comprises a significant mathematical reduction of the previously published HAN approach to a computationally optimized approach featuring a minimal amount of computational points yielding a real‐time capable model (denoted HAN‐RT), which complies with 1kHz HiL constraints while retaining HAN's quasi 3D nature. Presented results confirm that the computationally optimized HAN‐RT model displays real‐time capabilities at sampling rates above 1 kHz while producing results that agree very well with spatially resolved results generated by the 3D multiphase CFD tool and with the experimental results of steady state and transient fuel cell operation.
Gregor Tavčar; Tomaž Katrašnik. A Real Time Capable Quasi 3D System Level Model of PEM Fuel Cells. Fuel Cells 2019, 20, 17 -32.
AMA StyleGregor Tavčar, Tomaž Katrašnik. A Real Time Capable Quasi 3D System Level Model of PEM Fuel Cells. Fuel Cells. 2019; 20 (1):17-32.
Chicago/Turabian StyleGregor Tavčar; Tomaž Katrašnik. 2019. "A Real Time Capable Quasi 3D System Level Model of PEM Fuel Cells." Fuel Cells 20, no. 1: 17-32.
Phase separating Li-ion battery cell cathode materials feature a well-known phenomenon called the memory effect. It manifests itself as an abnormal change in working voltage being dependent on cell cycling history. It was only recently that plausible mechanistic reasoning of the memory effect in Li-ion batteries was proposed. However, the existing literature does still not consistently reveal a phenomenological background for the onset or absence of the memory effect. This paper provides strong experimental and theoretical evidence of the memory effect in phase separating Li-ion battery cathode materials. Specifically, the background leading to the onset or absence of the memory effect and the underlying causal chain of phenomena from the collective particle-by-particle intra-electrode phenomena to macroscopic voltage output of the battery are presented and discussed. The results, clearly reveal that no memory effect is observed and predicted for low cut off voltages, whereas the absence of the first rest in memory writing cycle does not result in the absence of the memory effect, as previously believed. In addition, excellent agreement between the simulated and measured results is shown which, on one hand confirms the credibility of the combined analyses and, on the other, provides clear causal relations from macroscopic experimental parameters to simulated phenomena on the particle level.
Klemen Zelič; Igor Mele; Ivo Pačnik; Jože Moškon; Miran Gaberšček; Tomaž Katrašnik. Revealing the Thermodynamic Background of the Memory Effect in Phase Separating Cathode Materials. Strojniški vestnik – Journal of Mechanical Engineering 2019, 65, 690 -700.
AMA StyleKlemen Zelič, Igor Mele, Ivo Pačnik, Jože Moškon, Miran Gaberšček, Tomaž Katrašnik. Revealing the Thermodynamic Background of the Memory Effect in Phase Separating Cathode Materials. Strojniški vestnik – Journal of Mechanical Engineering. 2019; 65 (11-12):690-700.
Chicago/Turabian StyleKlemen Zelič; Igor Mele; Ivo Pačnik; Jože Moškon; Miran Gaberšček; Tomaž Katrašnik. 2019. "Revealing the Thermodynamic Background of the Memory Effect in Phase Separating Cathode Materials." Strojniški vestnik – Journal of Mechanical Engineering 65, no. 11-12: 690-700.
The paper focuses on the implementation of a comprehensive and robust optimization procedure for a synthesis gas fired four-cylinder, spark ignited, 2.2 L industrial engine used in combined heat and power applications. Innovatively designed workflow is for the first time incorporating also a thorough operational stability analysis for evaluation of the engine operation durability while using off-design fuels. Design constraints of the engine operational space are set after in depth investigation of knock phenomena, cycle to cycle variations, emission formation phenomena and engine performance parameters. These are derived from experimental data, obtained from the engine, equipped with newly designed components. Throughout the paper, results obtained with synthesis gas are benchmarked to natural gas. With significant emphasis laid on analysis of lean operation conditions, as a measure to reduce environmental footprint of energy generation, a newly proposed optimum operation points reveal a possibility to obtain TA-Luft and EPA emission limits already with stoichiometric mixture. This allows to achieve a remarkably low power de-rating factor of only 16.5% and omission of any aftertreatment system. Therefore, findings of this study represent a significant improvement of current control strategies and enable further increase in specific power and thus economic attractiveness of distributed power generation techniques at enhanced durability while using low-carbon and renewable fuels.
Andraž Kravos; Tine Seljak; Samuel Rodman Oprešnik; Tomaž Katrašnik. Operational stability of a spark ignition engine fuelled by low H2 content synthesis gas: Thermodynamic analysis of combustion and pollutants formation. Fuel 2019, 261, 116457 .
AMA StyleAndraž Kravos, Tine Seljak, Samuel Rodman Oprešnik, Tomaž Katrašnik. Operational stability of a spark ignition engine fuelled by low H2 content synthesis gas: Thermodynamic analysis of combustion and pollutants formation. Fuel. 2019; 261 ():116457.
Chicago/Turabian StyleAndraž Kravos; Tine Seljak; Samuel Rodman Oprešnik; Tomaž Katrašnik. 2019. "Operational stability of a spark ignition engine fuelled by low H2 content synthesis gas: Thermodynamic analysis of combustion and pollutants formation." Fuel 261, no. : 116457.
A new mechanistically derived 0D model of a phase separating active cathode particle was designed for use in a multi particle porous electrode theory based model. The proposed 0D model was obtained by integration of dynamic equations of the spatially resolved single particle model, based on the regular solution theory. The described analytic procedure yields a thermodynamically consistent 0D model that preserves physicochemical relevance of the spatially resolved model and reduces computational times by up to six orders of magnitude. Besides its computational efficiency, the 0D model features high levels of consistency with the spatially resolved model in the low and high overpotential limit, which are most relevant for cell modelling. A transparent relation to the spatially resolved model provides validation of the suitability of previously applied intuitive approaches assigning spinodal average chemical potential to the entire particle. It also offers additional insights into the physicochemical phenomena inside a multiparticle electrode. The proposed 0D approach provides the basis for modelling advanced experimental observations covering: charge/discharge hysteresis, varying active particle population, solid solution vs. phase separating state of particles within active population, and memory effect when implemented in the multi particle phase separating porous electrode theory based model.
Klemen Zelič; Tomaž Katrašnik. Thermodynamically Consistent and Computationally Efficient 0D Lithium Intercalation Model of a Phase Separating Cathode Particle. Journal of The Electrochemical Society 2019, 166, A3242 -A3249.
AMA StyleKlemen Zelič, Tomaž Katrašnik. Thermodynamically Consistent and Computationally Efficient 0D Lithium Intercalation Model of a Phase Separating Cathode Particle. Journal of The Electrochemical Society. 2019; 166 (14):A3242-A3249.
Chicago/Turabian StyleKlemen Zelič; Tomaž Katrašnik. 2019. "Thermodynamically Consistent and Computationally Efficient 0D Lithium Intercalation Model of a Phase Separating Cathode Particle." Journal of The Electrochemical Society 166, no. 14: A3242-A3249.
To explore the influence of fuel injection strategy on the combustion process, the Computational Fluid Dynamics (CFD) simulations were performed, and simulation results were validated against the experimental data measured at different rail pressures and injection timings. The experiments were conducted on a diesel engine equipped with an advanced injection system that allows full control over the injection parameters. To model the combustion process of EN590 diesel fuel, two different approaches were used: the General Gas Phase Reactions (GGPR) approach and the 3-zones Extended Coherent Flame Model (ECFM-3Z+). The calculated results, such as mean pressure and rate of heat release, were validated against experimental data in operating points with different injection parameters in order to prove the validity of spray and combustion sub-models. At the higher injected pressure, GGPR model showed better prediction capability in the premixed phase of combustion process, compared to the ECFM-3Z+ model. Nevertheless, in the rate-controlled phase of combustion process, ECFM-3Z+ model shows stronger diffusion of temperature field, due to the more detailed consideration of combustion diffusion phenomena in the ECFM-3Z+ governing equations. Furthermore, the results show that the rail pressure has a lower impact on the combustion process for injection timing after the Top Dead Centre (TDC). Both, single and multi-injection cases are found to be in a good agreement with the experimental data, while the GGPR approach was found to be suitable only for combustion delay determination and ECFM-3Z+ also for the entire combustion process.
Filip Jurić; Zvonimir Petranović; Milan Vujanović; Tomaž Katrašnik; Rok Vihar; Xuebin Wang; Neven Duić. Experimental and numerical investigation of injection timing and rail pressure impact on combustion characteristics of a diesel engine. Energy Conversion and Management 2019, 185, 730 -739.
AMA StyleFilip Jurić, Zvonimir Petranović, Milan Vujanović, Tomaž Katrašnik, Rok Vihar, Xuebin Wang, Neven Duić. Experimental and numerical investigation of injection timing and rail pressure impact on combustion characteristics of a diesel engine. Energy Conversion and Management. 2019; 185 ():730-739.
Chicago/Turabian StyleFilip Jurić; Zvonimir Petranović; Milan Vujanović; Tomaž Katrašnik; Rok Vihar; Xuebin Wang; Neven Duić. 2019. "Experimental and numerical investigation of injection timing and rail pressure impact on combustion characteristics of a diesel engine." Energy Conversion and Management 185, no. : 730-739.
High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are a promising and emerging technology that allow for highly efficient low emission small scale electricity and heat generation. Simultaneous reduction of production costs and prolongation of the service life is considered as a significant challenge towards their wider market adoptions, which calls for application of predictive virtual tools during the development process of HT-PEMFC systems. To present a significant progress in the addressed area, this paper presents an innovative modelling framework based on: a) mechanistically based spatially and temporally resolved HT-PEMFC performance model and b) modular degradation modelling framework based on interacting partial platinum degradation mechanisms. Proposed innovative tool chain thus allows for - compared to the current state of the art – more efficient and systematic model supported design of FCs and in-depth understanding of cause and effect chain from FC operation to its degradation. This merit of the proposed modelling framework arises from systematic reflection of FC control parameters in operational parameters of the FC, which are inputs to degradation modelling framework that considers in an interacting manner carbon and Pt oxidation phenomena and Pt dissolution, redeposition, detachment and agglomeration phenomena thereby adequately modelling the causal chain.
Ambrož Kregar; Gregor Tavčar; Andraž Kravos; Tomaž Katrašnik. Predictive virtual modelling framework for performance and platinum degradation modelling of high temperature PEM fuel cells. Energy Procedia 2019, 158, 1817 -1822.
AMA StyleAmbrož Kregar, Gregor Tavčar, Andraž Kravos, Tomaž Katrašnik. Predictive virtual modelling framework for performance and platinum degradation modelling of high temperature PEM fuel cells. Energy Procedia. 2019; 158 ():1817-1822.
Chicago/Turabian StyleAmbrož Kregar; Gregor Tavčar; Andraž Kravos; Tomaž Katrašnik. 2019. "Predictive virtual modelling framework for performance and platinum degradation modelling of high temperature PEM fuel cells." Energy Procedia 158, no. : 1817-1822.
The limited durability of hydrogen fuel cells is one of the main obstacles in their wider adoption as a clean alternative technology for small scale electricity production. The Ostwald ripening of catalyst material is recognized as one of the main unavoidable degradation processes deteriorating the fuel cell performance and shortening its lifetime. The paper systematically studies how the modeling approach towards the electrochemically driven Ostwald ripening in the fuel cell catalyst differs from the classical diffusion driven models and highlights how these differences affect the resulting evolution of particle size distribution. At moderately low electric potential, root-law growth of mean particle size is observed with linear relation between mean particle size and standard deviation of particle size distribution, similar to Lifshitz-Slyozov-Wagner theory, but with broader and less skewed distribution. In case of high electric potential, rapid particle growth regime is observed and qualitatively described by redeposition of platinum from a highly oversaturated solution, revealing the deficiencies of the existing platinum degradation models at describing the Ostwald ripening in the fuel cells at high electric potentials. Several improvements to the established models of platinum degradation in fuel cell catalysts are proposed, aimed at better description of the diffusion processes involved in particle growth due to Ostwald ripening.
Ambrož Kregar; Tomaž Katrašnik. Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer. Open Physics 2019, 17, 779 -789.
AMA StyleAmbrož Kregar, Tomaž Katrašnik. Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer. Open Physics. 2019; 17 (1):779-789.
Chicago/Turabian StyleAmbrož Kregar; Tomaž Katrašnik. 2019. "Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer." Open Physics 17, no. 1: 779-789.