Oscar D. Monsalve-Cifuentes

This paper presents the mathematical modeling, fluid dynamic analysis, and experimental analysis of a spiral case without guide vanes. Using a specific case of the Archimedes spiral, the model eliminates the need for fixed or moving blades to simplify the design, manufacturing, and maintenance process of the turbomachine by reducing the number of system components while preserving the fluid dynamic performance of a turbomachine operating in turbine mode. The potential flow theory is used as a mathematical basis for developing a computational code that allows the automatic generation of the curves that define the geometry of the spiral chamber, simplifying the CAD modeling process. Finally, the process is validated numerically and experimentally under different operating conditions, reaching an average error percentage between numerical and experimental analysis of 5.893% of speed and 11.089% of pressure, guaranteeing the accuracy of the model.

Hydraulic turbines have become indispensable for harnessing renewable energy sources, particularly in-pipe hydraulic turbine technology, which leverages excess energy within pipeline systems like drinking water distribution pipes to produce electrical power. Among these turbines, the propeller-type axial turbine with circular blades stands out for its efficiency. However, there is a notable lack of literature on fluid dynamics and structural behavior under various operational conditions. This study introduces a comprehensive methodology to numerically investigate the hydraulic and structural responses of turbines designed for in-pipe installation. The methodology encompasses the design of circular blades, followed by parametric studies on fluid dynamics and structural analysis. The circular blade’s performance was evaluated across different materials, incorporating static, modal, and harmonic response analyses. Results showed that the circular blade achieved a peak hydraulic efficiency of 75.5% at a flow rate of 10 l/s, generating 1.86 m of head pressure drop and 138 W of mechanical power. Structurally, it demonstrated a safety factor exceeding 1 across the entire hydraulic range without encountering resonance or fatigue issues. This research and its methodology significantly contribute to advancing the understanding of designing and assessing the fluid dynamic behavior and structural integrity of circular blades in axial propeller-type turbines for in-pipe installations, serving as a valuable resource for future studies in similar domains.

In-pipe hydraulic turbines are a promising energy-harvesting technology. Recent studies have demonstrated a strong influence of the turbine blade number on the performance of an axial propeller-type turbine. However, limited research has been dedicated to turbine diameters less than 100 mm. Therefore, this research aimed to determine the effect of the number of blades on the hydrodynamic performance of a 75.3 mm diameter axial propeller turbine for in-pipe installation. A parametric numerical study was performed by varying the angular velocity from 1600 to 3800 rpm and the number of blades from 2 to 6. Results identified an inverse correlation between the hydraulic efficiency of the turbine and its blade number and a direct correlation between the pressure head and the turbine torque. Furthermore, the performance showed hydraulic behavior comparable to those found in literature, confirming a similar hydraulic behavior as turbines with diameters exceeding 100 mm. Additionally, the turbine’s internal flow behavior was analyzed by visualizing the vortex structure using the Q-criterion. Lastly, this study provides a deeper understanding of the effect of the number of blades on the hydrodynamic performance of an axial turbine for in-pipe installation.

Thermoelectric generators are devices that transform thermal energy into electric energy. These devices play an influential role in our constantly developing civilization due to their energy conversion capabilities and advantages over other conventional methods. The material properties and thermoelectric phenomena are paramount to the design process of such devices. The design process must have a complex tool to model all the thermoelectric phenomena, such as, for example, the commercial numerical code of Ansys Mechanical. However, these numerical tools can be methodologically and computationally demanding. Thus, this study aims to develop a methodology through which to characterize thermoelectric generators by using a simplified one-dimensional numerical model that considers temperature-dependent N- and P-type material properties and convective heat losses. The proposed model’s results are compared and validated to a single thermoelectric leg and a complete thermoelectric commercial module, both modeled in Ansys Thermal-Electric. These results consider the different values for electric and thermal loads as current densities, electric resistivities, and heat transfer coefficients. The main result of this study is the correct prediction of the output voltage and output power given by the one-dimensional proposed model, which was validated against a comprehensive model and the commercial thermoelectric module’s information. Therefore, the proposed methodology of this study provides a deeper understanding of the thermoelectric energy conversion process, and it can guide the design and optimization of thermoelectric generators for practical applications.