| 1. |
- Aslanidou, Ioanna, et al.
(författare)
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Micro Gas Turbines in the Future Smart Energy System : Fleet Monitoring, Diagnostics, and System Level Requirements
- 2021
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media S.A.. - 2297-3079. ; 7
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Forskningsöversikt (refereegranskat)abstract
- The energy generation landscape is changing, pushed by stricter regulations for emissions control and green energy generation. The limitations of renewable energy sources, however, require flexible energy production sources to supplement them. Micro gas turbine based combined heat and power plants, which are used for domestic applications, can fill this gap if they become more reliable. This can be achieved with the use of an engine monitoring and diagnostics system: real-time engine condition monitoring and fault diagnostics results in reduced operating and maintenance costs and increased component and engine life. In order to allow the step change in the connection of small engines to the grid, a fleet monitoring system for micro gas turbines is required. A proposed framework combines a physics-based model and a data-driven model with machine learning capabilities for predicting system behavior, and includes a purpose-developed diagnostic tool for anomaly detection and classification for a multitude of engines. The framework has been implemented on a fleet of micro gas turbines and some of the lessons learned from the demonstration of the concept as well as key takeaways from the general literature are presented in this paper. The extension of fleet monitoring to optimal operation and production planning in relation to the needs of the grid will allow the micro gas turbines to fit in the future green energy system, connect to the grid, and trade in the energy market. The requirements on the system level for the widespread use of micro gas turbines in the energy system are addressed in the paper. A review of the current solutions in fleet monitoring and diagnostics, generally developed for larger engines, is included, with an outlook into a sustainable future.
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| 2. |
- Gambarotta, Agostino, et al.
(författare)
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Editorial : Smart Energy Systems
- 2022
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Ingår i: FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND. - : FRONTIERS MEDIA SA. - 2297-3079. ; 8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Ghumman, I. S. S., et al.
(författare)
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Frictional performance of chemically modified cottonseed-based fossil-free biolubricant oil in a sliding tribopair
- 2023
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media S.A.. - 2297-3079. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the tribological properties of a green lubricant synthesized from cottonseed oil through a two-step transesterification process are investigated, with a specific focus on the maximum throughput of the second step that involves the reaction of cottonseed methyl ester with 2-ethyl-1-hexanol alcohol and a titanium isopropoxide (TIS) catalyst. The research centers on evaluating the physiochemical characteristics of this biolubricant and comparing them with those of commercial oil (5W30) and the ISO VG40 standard. Furthermore, the influence of crucial process variables, such as temperature, pressure, reaction time, and TIS catalyst concentration, is examined by analyzing variance in experimental data. Fourier transform infrared (FTIR) analysis is employed to identify functional groups, particularly emphasizing the impact of temperature and reaction time. By optimizing the second transesterification process under specific conditions (pressure = 19.42 mmHg, temperature = 175°C, catalyst concentration = 0.63%, and reaction time = 4.0 h), a cottonseed oil-based biolubricant is successfully produced, exhibiting properties comparable to those of commercial mineral lubricants. Notably, the findings reveal significant enhancements in the coefficient of friction (CoF) with a 49% reduction and wear resistance with a maximum 19% reduction. This study contributes valuable insights into optimizing biolubricant production derived from cottonseed oil through two-step transesterification, emphasizing its novel potential in improving frictional and wear characteristics.
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| 4. |
- Kalliorinne, Kalle, et al.
(författare)
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Artificial Neural Network Architecture for Prediction of Contact Mechanical Response
- 2021
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media S.A.. - 2297-3079. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Predicting the contact mechanical response for various types of surfaces is and has long been a subject, where many researchers have made valuable contributions. This is because the surface topography has a tremendous impact on the tribological performance of many applications. The contact mechanics problem can be solved in many ways, with less accurate but fast asperity-based models on one end to highly accurate but not as fast rigorous numerical methods on the other. A mathematical model as fast as an asperity-based, yet as accurate as a rigorous numerical method is, of course, preferred. Artificial neural network (ANN)-based models are fast and can be trained to interpret how in- and output of processes are correlated. Herein, 1,536 surface topographies are generated with different properties, corresponding to three height probability density and two power spectrum functions, for which, the areal roughness parameters are calculated. A numerical contact mechanics approach was employed to obtain the response for each of the 1,536 surface topographies, and this was done using four different values of the hardness per surface and for a range of loads. From the results, 14 in situ areal roughness parameters and six contact mechanical parameters were calculated. The load, the hardness, and the areal roughness parameters for the original surfaces were assembled as input to a training set, and the in situ areal roughness parameters and the contact mechanical parameters were used as output. A suitable architecture for the ANN was developed and the training set was used to optimize its parameters. The prediction accuracy of the ANN was validated on a test set containing specimens not seen during training. The result is a quickly executing ANN, that given a surface topography represented by areal roughness parameters, can predict the contact mechanical response with reasonable accuracy. The most important contact mechanical parameters, that is, the real area of contact, the average interfacial separation, and the contact stiffness can in fact be predicted with high accuracy. As the model is only trained on six different combinations of height probability density and power spectrum functions, one can say that an output should only be trusted if the input surface can be represented with one of these.
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| 5. |
- Lemmettylä, T., et al.
(författare)
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The Development and Precision of a Custom-Made Skitester
- 2021
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media SA. - 2297-3079. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In the sport of cross-country skiing, equipment has a direct influence on results. Ski teams do extensive testing of different ski base grinds and products on a yearly basis. To achieve reliable results, the quality of methods used for testing skis needs to be taken in to account in addition to factors including the physical characteristics of testing personnel and changes in weather conditions. The aim of this study was to introduce a custom-made skitester, that was developed for testing skis on real snow, in laboratory conditions, and to evaluate its precision. The current skitester is capable of glide testing both classic and skate skis as well as kick simulation for the testing of grip waxes. In the present study, glide testing precision was completed in three different conditions. Velocity and pressure of skis were evaluated in three different temperature conditions. During kick simulation, precision was determined in one temperature condition. For glide testing, the precision of the measurement unit was able to distinguish the differences between skis with a relative variation of 0.6–1.1%. However, the track preparation process caused variation. For kick simulation, precision of the measurement unit was slightly higher (2.5%), and track preparation caused less variation. The skitester is capable of distinguishing the differences between both skate and classic cross-country skis with certain limitations.
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| 6. |
- Nordvall, Erik, et al.
(författare)
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Knowledge-based engineering and computer vision for configuration-based substation design
- 2023
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Ingår i: FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND. - : FRONTIERS MEDIA SA. - 2297-3079. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: As the increase in electrification poses new demands on power delivery, the quality of the distribution system is paramount. Substations are a critical part of power grids that allow for control and service of the electrical distribution system. Substations are currently developed in a project-based and manually intensive manner, with a high degree of manual work and lengthy lead times. Substations are primarily sold through tenders that are accompanied by an inherent need for engineering-to-order activities. Although necessary, these activities present a paradox as tender processes must be agile and fast. To remedy this shortcoming, this article outlines a knowledge capture and reuse methodology to standardize and automate the product development processes of substation design.Methods: A novel framework for substation design is presented that implements knowledge-based engineering (KBE) and artificial intelligence methods in computer vision to capture knowledge. In addition, a product configuration system is presented, utilizing high-level CAD templates. The development has followed the KBE methodology MOKA.Results: The proposed framework has been implemented on several company cases where three (simplified) are presented in this paper. The framework decreased the time to create a 3D model from a basic electric single line diagram by performing the identification and design tasks in an automated fashion.Discussion: Ultimately, the framework will allow substation design companies to increase competitiveness through automation and knowledge management and enable more tenders to be answered without losing engineering quality.
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| 7. |
- Prajapati, Deepak K., et al.
(författare)
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An assessment of the effect of surface topography on coefficient of friction for lubricated non-conformal contacts
- 2024
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media S.A.. - 2297-3079. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Determining an accurate state of lubrication is of utmost importance for the precise functionality of machine elements and to achieve elongated life and durability. In this work, a homogenized mixed-lubrication model is developed to study the effect of surface topographies on the coefficient of friction. Various measured real surface topographies are integrated in the model using the roughness homogenization method. The shear-thinning behavior of the lubricant is incorporated by employing the Eyring constitutive relation. Several Stribeck curves are generated to analyze the effect of roughness lays and root mean square (RMS) roughness on the coefficient of friction. The homogenized mixed lubrication model is validated against experimental rolling/sliding ball-on-disc results, and a good agreement between simulated and experimental coefficient of friction is found.
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| 8. |
- Sahandifar, Pooya, et al.
(författare)
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Separate and Combined Effects of Geometrical and Mechanical Properties Changes Due to Aging on the Femoral Strength in Men and Women
- 2021
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers. - 2297-3079. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Aging, from 40 to +80Â years old, causes geometrical and mechanical properties changes in the proximal femur. The subperiosteal width expands faster in men compared to women during aging, while the cortical thickness varies unequally in each sector and differently between men and women. Another change which occurs during aging is bone mechanical properties such as stiffness and ultimate strains. Numerical analysis allows us to study the potential effects of each of the age-dependent changes on the fracture forces separately and combined. We investigated the effects of the geometrical and bone mechanical properties changes due to aging on the femoral strength during a common falling scenario using a transverse isotropic continuum damage model. First, the femur model was adapted from a previously developed human body model named THUMS v4.02. Then, three sets of models were developed to address each of the changes separately and combined for both sexes. We found that the fracture forces in women are on average 1500Â N less than in men of the same age. The age-dependent geometrical changes increased the fracture forces in men (25Â N/decade), whereas it reduced the fracture forces by 116Â N/decade in women. The mechanical properties changes reduced the fracture forces in men more than in women (354.5Â N/ decade vs. 225.4Â N/decade). When accounting for both geometrical and mechanical properties changes due to aging, the fracture forces decreased by 10.7% of the baseline in women per decade compared to 7.2% per decade in men.
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| 9. |
- Thorén, Per-Anders, et al.
(författare)
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High-Velocity Shear and Soft Friction at the Nanometer Scale
- 2021
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Ingår i: FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND. - : Frontiers Media SA. - 2297-3079. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- We study high-speed friction on soft polymer materials by measuring the amplitude dependence of cyclic lateral forces on the atomic force microscope (AFM) tip as it slides on the surface with fixed contact force. The resulting dynamic force quadrature curves separate the elastic and viscous contributions to the lateral force, revealing a transition from stick-slip to free-sliding motion as the velocity increases. We explain force quadratures and describe how they are measured, and we show results for a variety of soft materials. The results differ substantially from the measurements on hard materials, showing hysteresis in the force quadrature curves that we attribute to the finite relaxation time of viscoelastic surface deformation.
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| 10. |
- van der Wijngaart, Wouter, et al.
(författare)
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Electrostatic sampling of patient breath for pathogen detection : a pilot study
- 2020
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Ingår i: Frontiers in Mechanical Engineering. - : Frontiers Media SA. - 2297-3079. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Collecting samples for diagnosis of respiratory infections can be invasive and highly uncomfortable for patients; with sampling techniques ranging from nasal or throat swabs to bronchoalveolar lavage. In this work, we explore the electrostatic capture of exhaled pathogens as a non-invasive sampling method for rapid diagnosis in a primary care setting. A pilot study at primary care centers in Belgium enrolled 20 patients presenting with flu-like symptoms whose diagnosis was determined by nasopharyngeal (NP) swabs. We collected exhaled aerosol particles from infected patients using a breath electrostatic sampler (BESS) and using filters, following an extremely light procedure consisting of five normal exhales. All samples were analyzed using a commercial multiplex q-RT-PCR panel assay. Staphylococcus aureus (S. aureus) was detected from BESS samples of 7 patients; 3 of whom were in agreement with their corresponding diagnoses. The BESS method was negative for exhaled viruses. We detected viruses, but no bacteria, with the filters, but the results showed no correlation with the corresponding diagnosis. Our results indicate that electrostatic sampling of exhaled breath is a technique and approach potentially suited for the primary care setting, where it might constitute a helpful diagnostic device.
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