Particle based models of composite anodes are useful tools for exploring the behavior of SOFC systems. As part of our efforts to develop models for understanding fuel cells, we have been building models of Ni-YSZ comp...Particle based models of composite anodes are useful tools for exploring the behavior of SOFC systems. As part of our efforts to develop models for understanding fuel cells, we have been building models of Ni-YSZ composite anodes using experimentally measured particle size distributions. The objectives of this study were to characterize the percolation threshold and conductivity of these models in comparison to simpler mono dispersed and biphasic particle size distributions from the literature. We found that the average values for the onset of percolation and the measured conductivity of the models with experimentally measured particle size distributions are similar to those for the simple distributions and the experimentally measured distributions. For all of the configurations evaluated, the onset of percolation in the Nickel phase occurred at a solid fraction of Nickel between 20% and 25%. This corresponded almost exactly to the point at which the coordination number between Nickel phase particles reached 2.2. The significant finding was that the variation in the value for the conductivity, as measured by the standard deviation of the results, was several orders of magnitude higher than for the simpler systems. We explored the validity of our assumptions, specifically the assumption of random particle placement, by building a particle model directly from FIB-SEM data. In this reconstruction, it was clear that the location of particles was not random. Particles of the same type and size had much likelihood of contact higher than would indicated by random location.展开更多
The present work is based on the third-order partial differential equation (PDE) of acoustics of viscoelastic solids for the quasi-equilibrium (QE) component of the average normal stress. This PDE includes the stress-...The present work is based on the third-order partial differential equation (PDE) of acoustics of viscoelastic solids for the quasi-equilibrium (QE) component of the average normal stress. This PDE includes the stress-relaxation time (SRT) for the material and is applicable at any value of the SRT. The notion of a smart deicing system (SDS) for blade shells (BSs) of a wind turbine is specified. The work considers the stress in a BS as the one caused by the operational load on the BS. The work develops key design issues of a prospective ice-detection system (IDS) able to supply an array of the heating elements of an SDS with the element-individual spatiotemporal data and procedures for identification of the material parameters of atmospheric-ice (AI) layer accreted on the outer surfaces of the BSs. Both the SDS and IDS flexibly allow for complex, curvilinear and space-time-varying shapes of BSs. The proposed IDS presumes monitoring of the QE components of the normal stresses in BSs. The IDS is supposed to include an array of pressure-sensing resistors, also known as force-sensing resistors (FSRs), and communication hardware, as well as the parameter-identification software package (PISP), which provides the identification on the basis of the aforementioned PDE and the data measured by the FSRs. The IDS does not have hardware components located outside the outer surfaces of, or implanted in, BSs. The FSR array and communication hardware are reliable, and both cost- and energy-efficient. The present work extends methods of structural-health/operational-load monitoring (SH/OL-M) with measurements of the operational-load-caused stress in closed solid shells and, if the prospective PISP is used, endows the methods with identification of material parameters of the shells. The identification algorithms that can underlie the PISP are computationally efficient and suitable for implementation in the real-time mode. The identification model and algorithms can deal with not only the single-layer systems such as the BS layer without the AI layer or two-layer systems but also multi-layer systems. The outcomes can be applied to not only BSs of wind turbines but also non-QE closed single- or multi-layer deformable solid shells of various engineering systems (e.g., the shells of driver or passenger compartments of ships, cars, busses, airplanes, and other vehicles). The proposed monitoring of the normal-stress QE component in the mentioned shells extends the methods of SH/OL-M. The topic for the nearest research is a better adjustment of the settings for the FSR-based measurement of the mentioned components and a calibration of the parameter-identification model and algorithms, as well as the resulting improvement of the PISP.展开更多
基金partially supported through a MURI from the United States Office of Naval Research
文摘Particle based models of composite anodes are useful tools for exploring the behavior of SOFC systems. As part of our efforts to develop models for understanding fuel cells, we have been building models of Ni-YSZ composite anodes using experimentally measured particle size distributions. The objectives of this study were to characterize the percolation threshold and conductivity of these models in comparison to simpler mono dispersed and biphasic particle size distributions from the literature. We found that the average values for the onset of percolation and the measured conductivity of the models with experimentally measured particle size distributions are similar to those for the simple distributions and the experimentally measured distributions. For all of the configurations evaluated, the onset of percolation in the Nickel phase occurred at a solid fraction of Nickel between 20% and 25%. This corresponded almost exactly to the point at which the coordination number between Nickel phase particles reached 2.2. The significant finding was that the variation in the value for the conductivity, as measured by the standard deviation of the results, was several orders of magnitude higher than for the simpler systems. We explored the validity of our assumptions, specifically the assumption of random particle placement, by building a particle model directly from FIB-SEM data. In this reconstruction, it was clear that the location of particles was not random. Particles of the same type and size had much likelihood of contact higher than would indicated by random location.
文摘The present work is based on the third-order partial differential equation (PDE) of acoustics of viscoelastic solids for the quasi-equilibrium (QE) component of the average normal stress. This PDE includes the stress-relaxation time (SRT) for the material and is applicable at any value of the SRT. The notion of a smart deicing system (SDS) for blade shells (BSs) of a wind turbine is specified. The work considers the stress in a BS as the one caused by the operational load on the BS. The work develops key design issues of a prospective ice-detection system (IDS) able to supply an array of the heating elements of an SDS with the element-individual spatiotemporal data and procedures for identification of the material parameters of atmospheric-ice (AI) layer accreted on the outer surfaces of the BSs. Both the SDS and IDS flexibly allow for complex, curvilinear and space-time-varying shapes of BSs. The proposed IDS presumes monitoring of the QE components of the normal stresses in BSs. The IDS is supposed to include an array of pressure-sensing resistors, also known as force-sensing resistors (FSRs), and communication hardware, as well as the parameter-identification software package (PISP), which provides the identification on the basis of the aforementioned PDE and the data measured by the FSRs. The IDS does not have hardware components located outside the outer surfaces of, or implanted in, BSs. The FSR array and communication hardware are reliable, and both cost- and energy-efficient. The present work extends methods of structural-health/operational-load monitoring (SH/OL-M) with measurements of the operational-load-caused stress in closed solid shells and, if the prospective PISP is used, endows the methods with identification of material parameters of the shells. The identification algorithms that can underlie the PISP are computationally efficient and suitable for implementation in the real-time mode. The identification model and algorithms can deal with not only the single-layer systems such as the BS layer without the AI layer or two-layer systems but also multi-layer systems. The outcomes can be applied to not only BSs of wind turbines but also non-QE closed single- or multi-layer deformable solid shells of various engineering systems (e.g., the shells of driver or passenger compartments of ships, cars, busses, airplanes, and other vehicles). The proposed monitoring of the normal-stress QE component in the mentioned shells extends the methods of SH/OL-M. The topic for the nearest research is a better adjustment of the settings for the FSR-based measurement of the mentioned components and a calibration of the parameter-identification model and algorithms, as well as the resulting improvement of the PISP.
