This paper presents experimental determination of the heat transfer coefficient and the friction factor in an internally rifled tube. The experiment was carried out on a laboratory stand constructed in the Department of Energy of the Cracow University of Technology. The tested tube is used in a Polish power plant in a supercritical circulating fluidized bed (CFB) boiler with the power capacity of 460 MW. Local heat transfer coefficients were determined for Reynolds numbers included in the range from ~6000 to ~50,000, and for three levels of the heating element power. Using the obtained experimental data, a relation was developed that makes it possible to determine the dimensionless Chilton−Colburn factor. The friction factor was also determined as a function of the Reynolds number ranging from 20,000 to 90,000, and a new correlation was developed that represents the friction factor in internally ribbed tubes. The local heat transfer coefficient and the friction factor obtained during t... [more]

Fused contactors and thermal magnetic circuit breakers are commonly applied protective devices in power distribution systems to protect the circuits when short-circuit faults occur. A power distribution system may contain various makes and models of protective devices, as a result, customizable simulation models for protective devices are demanded to effectively conduct system-level reliable analyses. To build the models, thermal energy-based data analysis methodologies are first applied to the protective devices’ physical properties, based on the manufacturer’s time/current data sheet. The models are further enhanced by integrating probability tools to simulate uncertainties in real-world application facts, for example, fortuity, variance, and failure rate. The customizable models are expected to aid the system-level reliability analysis, especially for the microgrid power systems.

With the development of autonomous driving technology, the requirements for machine perception have increased significantly. In particular, camera-based lane detection plays an essential role in autonomous vehicle trajectory planning. However, lane detection is subject to high complexity, and it is sensitive to illumination variation, appearance, and age of lane marking. In addition, the sheer infinite number of test cases for highly automated vehicles requires an increasing portion of test and validation to be performed in simulation and X-in-the-loop testing. To model the complexity of camera-based lane detection, physical models are often used, which consider the optical properties of the imager as well as image processing itself. This complexity results in high efforts for the simulation in terms of modelling as well as computational costs. This paper presents a Phenomenological Lane Detection Model (PLDM) to simulate camera performance. The innovation of the approach is the modell... [more]

This paper proposes a generic analysis framework for a grid supporting modular multilevel converter (MMC)-high voltage DC (HVDC) in a multi-infeed of line commutated converter (LCC) and MMC (MILM) system. MMC-HVDC can support the grid by compensating for the exact reactive power consumptions within the MMC-HVDC system and the varying power system conditions in the MILM system. Maximum active/reactive power capability (MPQC) curve and PQ loading curve comparison process is introduced to properly design a grid supporting MMC-HVDC. While the MPQC curve presents the maximum PQ range of the MMC-HVDC system based on the submodule capacitance value and the modulation index, the PQ loading curve presents the reactive power requirement from the power system that MMC-HVDC needs to compensate. Finally, the comparison of these two curves yields the proper value of submodule capacitance and the modulation index for sufficiently supporting the MILM system. The proposed framework is validated with de... [more]

In this paper, the numerical model of a centrifugal compressor low-flow stage is verified. The gaps and labyrinth seals were simulated in the numerical model. The task was to determine the optimal settings for high-quality modeling of the low-flow stages. The intergrid interface application issues, turbulence and roughness models are considered. The obtained numerical model settings are used to validate seven model stages for the range of the optimal conditional flow coefficient with Φopt = 0.008−0.018 and the conditional Mach number Mu = 0.785−0.804. The simulation results are compared with the experimental data. The high pressure stage-7 (HPS-7) stage with Φopt = 0.010 and Mu = 0.60 at different inlet pressure of 4, 10 and 40 atm is considered separately. Acceptable validation results are obtained with the recommended numerical model settings; the modeling uncertainty for the polytropic pressure coefficient δη*pol < 4% for the efficiency coefficient δη*pol exceeds the limit of 4%... [more]

The implementation of a dual electric system that is capable of operating with either constant current and variable voltage, or constant voltage and variable current appliances, is one of the possible options to solve low-intensity stochastic energy utilization problems from renewable energy sources. This research paper analyzes the potential benefit of a novel three-phase dual system power inverter over the conventional inverter used in a solar power plant. The concept of such a power inverter is explained, and the digital twin model is created in a MATLAB Simulink environment. The efficiency characteristic of the simulated inverter is compared to the efficiency characteristic of a real conventional inverter. A standalone data logging system and an additional data acquisition system were used to collect and process data from the real inverter. Comparison of the digital twin inverter and the real conventional inverter shows the potential benefit of this novel inverter technology. It is... [more]

Solar-powered aircraft can perform long-term flights with clean solar energy. However, the energy derived from solar irradiation is influenced by the time of year and latitude, which limits the energy acquisition ability of solar aircraft with a straight-wing configuration. Hence, unconventional configurations based on increasing wing dihedral to track the sun are proposed to improve energy acquisition at high-latitude regions in winter, which may involve power loss caused by mismatch in the photovoltaic system. However, mismatch loss is seldom considered and may cause energy to be overestimated. In this paper, the energy acquisition characteristics of a joint-wing configuration are presented based on the simulation of an energy system to investigate the mismatch power loss. The results indicate a 4~15% deviation from the frequently used estimation method and show that the mismatch loss is influenced by the curved upper surface, the severity of shading and the circuit configuration. Th... [more]

The aim of the proposed paper is the development of an electro-thermal model of semiconductor component using an indirect modelling approach. The approach is based on the integration of the component’s electrical properties considering non-linear behavior of a V-A characteristic. In this way, the identification of semiconductor material properties considering non-linear dependencies and semiconductor volume is provided. The main aim of the presented approach is simplification of the electro−thermal interaction within finite-element modelling of the semiconductor components. In this way, it is possible to omit more complex boundary definitions and the setting of the semiconductor-based physics. The proposed methodology is presented within the development of a simulation model based on a small high-frequency rectifying diode, taking into account its geometric dimensions and the internal arrangement of its structure. Simulation was performed as a transient analysis, while the results from... [more]

Road transport contributes to almost a quarter of carbon dioxide emissions in the EU. To analyze the exhaust emissions generated by vehicle flows, it is necessary to use specialized emission models, because it is infeasible to equip all vehicles on the road in the tested road sections with the Portable Emission Measurement System (PEMS). However, the currently used emission models may be inadequate to the investigated vehicle structure or may not be accurate due to the used macroscale. This state of affairs is especially related to full hybrid vehicles, since there are none of the microscale emission models that give estimated emissions values exclusively for this kind of drive system. Several automakers over the past decade have invested in hybrid vehicles with great opportunities to reduce costs through better design, learning, and economies of scale. In this work, the authors propose a methodology for creating a CO2 emission model, which takes relatively little computational time, a... [more]

A fundamental task in the dynamic simulation of parabolic trough power plants (PTPP) is to understand the behavior of the system physics and control loops in the presence of weather variations. This study provides a detailed description of the advanced controllers used in the power block (PB) of a 50 MWel parabolic trough power plant (PTPP). The PB model is achieved using APROS software based on the actual specifications of the existing power plant. To verify the behaviour of the PB model, a comparison between the simulated results and given real data is documented depending on a previous study, and the results indicate a reasonable degree of correspondence. The purpose of this study is to create reference models for the PB. Thereby, developers and engineers will have a better understanding of the state of the art of advanced control loops in these power plants. Moreover, these types of models can be used to specify the most suitable mode of operation for the power plant. In addition,... [more]

Due to the increasing penetration of renewable energies in lower voltage level, there is a need to develop new control strategies to stabilize the grid voltage. For this, an approach using deep learning to recognize electric loads in voltage profiles is presented. This is based on the idea to classify loads in the local grid environment of an inverter’s grid connection point to provide information for adaptive control strategies. The proposed concept uses power profiles to systematically generate training data. During hyper-parameter optimizations, multi-layer perceptron (MLP) and convolutional neural networks (CNN) are trained, validated, and evaluated to determine the best task configurations. The approach is demonstrated on the example recognition of two electric vehicles. Finally, the influence of the distance in a test grid from the transformer and the active load to the measurement point, respectively, onto the recognition accuracy is investigated. A larger distance between the i... [more]

This paper presents a mathematical model of the heat and mass transfer processes for a rotary-spray honey dehydrator with a heat pump and a closed air circuit. An analytical calculation model, based on the energy balance equations of the dehydrator and heat pump, was used to model the transient dehydration process of honey in a dehydrator. The presented article includes a different approach to modelling both the dryer and the heat pump assisting the drying process. The novel quality of this study lies in the use of original equations to determine the heat and mass transfer coefficients between honey and air and using an actual model of a cooling unit to model the honey dehydration process. The experimentally verified calculation algorithm enables an analysis of the effects of air flow rate, mixer rotation speed, and cooling unit power on the efficiency of the drying process. The dehydrator calculation model was used to minimize the drying time by selecting the optimal evaporative tempe... [more]

This paper presents comprehensive analytical, numerical and experimental research of the compact and integrated high-power pulse generation and forming system based on the flux compression generator and the electro-explosive forming fuse. The paper includes the analysis of the presented solution, starting from the individual components studies, i.e., the separate flux compression generator tests in field conditions and the forming fuse laboratory test, through the formulation of the extended quasi-empirical components models aimed at enabling their optimal parameters determination at the early design stage and ending with the description of the integrated system studies in field conditions. Based on detailed research, it was possible to achieve very high parameters of the generated pulses, i.e., overvoltages of up to 340 kV with the available source power reaching 25 GW. A very high convergence of the simulation and the results of experimental research has been obtained. The parameters... [more]

To achieve the climate goals of the Paris Agreement, greenhouse gas emissions from the electricity sector must be substantially reduced. We develop an agent-based model of the electricity system with heterogeneous agents who invest in power generating capacity under uncertainty. The heterogeneity is characterised by the hurdle rates the agents employ (to manage risk) and by their expectations of the future carbon prices. We analyse the impact of the heterogeneity on the transition to a low carbon electricity system. Results show that under an increasing CO2 tax scenario, the agents start investing heavily in wind, followed by nuclear and to some extent in natural gas fired power plants both with and without carbon capture and storage as well as biogas fired power plants. However, the degree to which different technologies are used depend strongly on the carbon tax expectations and the hurdle rate employed by the agents. Comparing to the case with homogeneous agents, the introduction of... [more]

Measurements of the dynamic load of conveyor belts of identical strengths were used to evaluate and compare the data for belts with and without a support system. The goal was to identify the effects of the support system in terms of a relative amount of impact energy absorbed by a conveyor belt. A dynamic model was designed based on selected parameters of the impact process. Damage to conveyor belts, caused by the absorption of impact energy, was evaluated using the applied methods of mathematical statistics.

Conditions that prevail during harsh winters and hot summers pose a serious challenge for machine designers building devices suitable for operation in extreme weather. It is essential for the designers and the users to define the principles and conditions for the safe operation of machines and devices with hydraulic drive in low ambient temperatures. Bearing in mind the above, the author tested the hydraulic motors in thermal shock conditions (cold motors were fed with a hot working medium). This enterprise required the design and construction of a specialized stand for testing hydraulic motors, including satellite motors, in thermal shock conditions. The stand was equipped with the apparatus and a system for measuring the temperature of the moving parts of the satellite motor. The experimental tests were conducted in the laboratory of the Faculty of Mechanical Engineering and Ship Technology at Gdańsk University of Technology. The paper presents the results of tests of a correctly and... [more]

As we move towards electrical networks with a growing presence of renewable generation, the representation of the electrical components becomes more important. In hydro-dominated power systems, modelling the forbidden zones of hydro plants becomes increasingly challenging as the number of plants increases. Such zones are ranges of generation that either should be avoided or are altogether unreachable. However, because representing the forbidden zones introduces a substantial computational burden, hydrothermal unit-commitment problems (HTUC) for large systems are usually formulated ignoring the forbidden zones. Nonetheless, this simplification may demand adjustments to the solution of the HTUC, because the generation of the hydro stations may fall in forbidden zones. In practice, the adjustments are usually performed based on the experience of system operators and, then, can be far from an optimal correction. In this paper, we study the impact of explicitly representing the hydro-genera... [more]

Bifacial photovoltaics (BPVs) are emerging with large momentum as promising solutions to improve energy yield and cost of PV systems. To reach its full potential, an accurate understanding of the physical characteristics of BPV technology is required. For this reason, we collected experimental data to refine a physical model of BPV. In particular, we simultaneously measured the module temperature, short circuit current (Isc), open-circuit voltage (Voc), power at the maximum power point (Pmpp), and the energy yield of a bifacial and a monofacial minimodule. Such minimodules, realised with the same geometry, cell technology, and module lamination, were tested under the same clear sky outdoor conditions, from morning to afternoon, for three days. The bifacial system experimentally shows higher module temperatures under operation, about 10 °C on a daily average of about 40 °C. Nevertheless, its energy yield is about 15% larger than the monofacial one. We propose a physical quantitative mod... [more]

The article discusses the analysis of the possible development of hazards associated with the operation of vehicles equipped with an electric drive using the example of passenger cars. The authors review the problem of the safety of people and property resulting from the occurrence of a fire in an electric passenger car, in the context of fires that have occurred in recent years. Particular attention was paid to the analysis of the state of knowledge concerning the characteristics of the fire progression in an electric car, its heat release rate curve [HRR], total heat release [THR], heat of combustion and factors affecting the fire progression. In this paper, an attempt was made to compare the fire characteristics of an electric car and a passenger car equipped with an internal combustion engine together with an estimation, using CFD simulations, of the impact on the safety of people and property in closed structures such as underground garages or road tunnels. The need for further de... [more]

Emissions from heavy-duty vehicles need to be reduced to decrease their impact on the climate and to meet future regulatory requirements. The use of a cost-optimized thermoelectric generator based on total cost of ownership is proposed for this vehicle class with natural gas engines. A holistic model environment is presented that includes all vehicle interactions. Simultaneous optimization of the heat exchanger and thermoelectric modules is required to enable high system efficiency. A generator design combining high electrical power (peak power of about 3000 W) with low negative effects was selected as a result. Numerical CFD and segmented high-temperature thermoelectric modules are used. For the first time, the possibility of an economical use of the system in the amortization period of significantly less than 2 years is available, with a fuel reduction in a conventional vehicle topology of already up to 2.8%. A significant improvement in technology maturity was achieved, and the powe... [more]

The operation of various types of turbomachines is importantly affected by sediment erosion. Francis turbines used for power generation typically suffer said effects due to the fact that they are used in sediment-laden rivers and are usually operated disregarding the long-term effect of the erosion on turbine performance. This investigation seeks to study the erosion rate for the main components of the turbines located at San Francisco hydropower plant in Pastaza, Ecuador. A sediment characterization study was performed in order to determine the properties of the particles present in Pastaza River and accurately predict their effect on the turbine flow passages. A numerical approach combining liquid−solid two-phase flow simulation and an erosion model was used to analyze the erosion rates at different operating conditions and determine wear patterns in the components. As expected, the results indicated that an increase in the erosion rate was obtained for higher intake flows. However,... [more]

Switched-mode power supplies (SMPSs) are an important component in many electrical systems. As a highly non-linear device, an unavoidable side-effect of SMPS operation is its high harmonics power. One of the ways to model the harmonic power consumption profile is in terms of a random process. This paper addresses random process modeling with a corresponding probability density function (PDF), auto-covariance function (ACF) and spectral coherence. The consumed harmonics power was evaluated under different load conditions and is based on experimental results of current consumption from SMPSs. The analysis shows that harmonics power may be modeled by a lognormal distribution that is time-domain uncorrelated, and that has spectral-domain correlation modeled by a Gaussian radial basis function. Extensive discussion on the modeling results is also provided. Moreover, random simulation approach based on the modeling results was proposed.

Designing a configuration of an efficient solid oxide fuel cell (SOFC) system and operating it under appropriate conditions are important for achieving a highly efficient SOFC system. In our previous research, the system layout of a SOFC system with anode off-gas recirculation was suggested, and the system performance was examined using a numerical model. In the present study, the system operating conditions were optimized based on the system configuration and numerical model developed in the previous paper. First, a parametric sensitivity analysis of the system performance was investigated to demonstrate the main operating parameters. Consequently, the fuel flow rate and recirculation ratio were selected. Then, the available operating conditions, which keep the system below the operating limits and satisfy the desired system performance (Ufuel > 0.7 and ηelec > 45%) were discovered. Finally, optimized operating conditions were suggested for three operating modes: optimized electrical... [more]

The aim of this work was to develop a parameterized analytical and FEM (Finite Element Method) model of a switched reluctance motor. The developed analytical model was used to assess the performance of these types of motors, and is determined to be a tool for comparing and evaluating switched reluctance motors of various designs. The aim of the work was also the systematization of knowledge related to the operation, structure and methods of determining the static electromagnetic torque generated by switched reluctance motors. The FEM model (ANSYS) was, also, made in order to verify physical phenomena occurring during operation of these motors. Four laboratory tests were executed as part of the work prototypes of switched reluctance motors built at Warsaw University of Technology. A parameterized analytical model was developed and implemented in MATLAB. The model operation tests were conducted and as a result, the characteristics describing the dependence of the electromagnetic torque a... [more]

The purpose of this study was to investigate whether small plates covering the roof and the hood of the DrivAer estate vehicle can be used as airbrakes and increase its drag as well as the downforce. The presented results were obtained with the use of the commercial computational fluid dynamics software ANSYS® Fluent. The main findings of the article are that the aerodynamic devices such as flaps covering surfaces of the vehicle can have a significant impact on drag increase and can be used not only to make the design of the car more striking but also beneficial when utilized as a part of an active aerodynamic setup.