Papers by José R Nuñez-Alvarez
Energy Conversion and Management: X, 2025
The engine performance can change after diesel fuel is replaced with a blend of CH 4 and n-heptan... more The engine performance can change after diesel fuel is replaced with a blend of CH 4 and n-heptane at varying percentages. This study investigates the effects of fuel injection timing on the performance, efficiency, and emissions of a dual-fuel diesel engine running on a CH4 and n-heptane mixture. The analysis uses computational fluid dynamics (CFD) and AVL Fire software with advanced chemical kinetics tools, such as Chemkin, to transition from liquid to gaseous fuels. To accomplish this, the fuel injection timing was adjusted to three settings: 22 • before top dead center (BTDC), 18 • BTDC, and 14 • BTDC. Methane was blended with n-heptane at ratios of 90 %:10 %, 85 %:15 %, and 75 %:25 %. The findings from the numerical simulations demonstrated that prolonging the fuel injection duration in the dual-fuel diesel engine resulted in an escalation in the temperature within the combustion chamber and an augmentation in the maximum cylinder pressure. Additionally, both the ignition delay and the distance from top dead center to the peak ignition pressure were diminished. With the rise in peak cylinder pressure, the output torque experienced a 16 % increase. Conversely, increasing the ratio of liquid fuel in the blend resulted in a shorter ignition delay, which caused a decline in peak cylinder pressure, accompanied by a 17 % drop in output torque and a 70 % decrease in indicator power. The implementation of early fuel injection at elevated engine speeds led to an enhancement in indicator power and an improvement in emissions, culminating in a 31 % reduction in nitrogen oxides (NOx) and a 16 % decrease in soot levels.
Hoy en día somos totalmente dependientes de los combustibles fósiles en todos los aspectos; por e... more Hoy en día somos totalmente dependientes de los combustibles fósiles en todos los aspectos; por ello fomentar el uso y aplicación de las energías renovables y eficiencia energética son la mejor manera de reducir el daño provocado al planeta, frenando los efectos que ocurrirán en el futuro. La energía eléctrica generada a partir de fuentes de energía renovables presenta la ventaja de brindar una autosuficiencia que no solo conduce a una mejora del medio ambiente sino también incrementa la rentabilidad de una instalación, reduciendo los costes de energía y en general aumentando su eficiencia. Siendo conscientes de estas ventajas, este trabajo investigativo se orientó al estudio energético y económico de un proyecto que a partir de fuentes renovables de energía suministre electricidad en el esquema de generación distribuida, es decir se realizó el dimensionamiento de una Unidad de Producción de Autoconsumo (UPAC) para la Universidad Técnica de Manabí (UTM). Además, se realizó una evalu...
Educosta eBooks, 2019
El Capítulo presenta el desarrollo de un sistema informático capaz de mantener informada de forma... more El Capítulo presenta el desarrollo de un sistema informático capaz de mantener informada de forma eficaz a los tomadores de decisiones, y a la población en general, mediante el uso de un sistema de alertas por amenazas meteorológicas extremas. Para su diseño se realizó una investigación sobre los Sistemas de Alertas Tempranas (SAT) e instituciones de vigilancia de estos eventos en Cuba, así como, sobre la estructura del funcionamiento, descripción conceptual y formas de articulación de las tecnologías de la información. Se demostraron además los vínculos existentes entre los SAT y los programas de Manejo Integrado de Zonas Costeras (MIZC). Como resultado principal del capítulo se desarrolla una herramienta informática web que integra y visualiza múltiples alertas tempranas ante fenómenos climáticos extremos de corta y prolongada duración, contribuyendo a una adecuada gestión en la reducción del riesgo de desastres.
Journal of Engineering Science and Technology Review, 2020
Greater incorporation of wind energy into power systems has necessitated the development of accur... more Greater incorporation of wind energy into power systems has necessitated the development of accurate and reliable techniques for wind speed forecasting. However, although there are multiple studies, none are set up for the Colombia Caribbean coast. This is a disadvantage because the potential of wind resources in this region is greater than the hydroelectric potential of the whole country, but all this potential has yet to be developed. In this paper, based on time series, Autoregressive Integrated Moving Average (ARIMA), and Multiple Regression with Ordinary Least Squares (OLS) in the study, two models are proposed and their performance for wind speed prediction is compared. The data were collected in the meteorological station located in the experimental farm of the Atlantic University, in Barranquilla, Colombia, and variables analyzed included wind speed, wind direction, temperature, relative humidity, solar radiation, and pressure. The results of the two approaches indicated that among all the involved models, the ARIMA model has the best predicting performance. Also, it is essential to highlight that through this work, decision-makers would explore the local wind potential, allowing for the possibility of predicting future wind speed, and thus giving them the ability to plan the production and the interaction of other sources of energy.
IOP Conference Series: Materials Science and Engineering, 2020
Transformers are essential equipment to the operation of electrical power systems, a failure caus... more Transformers are essential equipment to the operation of electrical power systems, a failure causes the lack of electricity supply to end-users, affecting the operating indicators of companies in the distribution sector. The investigation presents an identification of the faults in transformers through a fishbone diagram, an evaluation of the variables that cause the identified failure using the cross-impact matrix method and a proposal to improve the performance. The results will enable a plan to be developed for taking action with monitoring plans to avoid faults that could put the electrical asset at risk and achieve a better performance of the distribution network.
IEEE Latin America Transactions, 2019
This paper shows a novel approach for detecting ventricular heartbeats using a 1D Convolutional N... more This paper shows a novel approach for detecting ventricular heartbeats using a 1D Convolutional Neural Network (1D-CNN). The algorithm input is the raw ECG signal, i.e., no signal pre-processing nor feature extraction are involved. The output of the 1D-CNN is filtered using a combination of linear and nonlinear filters to produce the final output. The MIT-BIH arrhythmia database was used for both algorithm training/tuning and evaluation. The assessment methodology followed the interpatient paradigm, where the algorithm was trained and evaluated using independent subsets. The performance of the proposed method was evaluated for two tasks; QRS detection, and heartbeat classification. QRS detection resulted in a sensitivity of 99.0% and a positive predictivity of 96.5%. The performance assessment of the ventricular ectopic beat detection resulted in a sensitivity of 85.8% and a positive predictivity of 64.5%. Although there is still room for improvement, the results suggest that convolutional neural networks are a promising approach for building heartbeat classifiers.
International Journal of Power Electronics and Drive Systems (IJPEDS), 2022
In electrical protection, there is a method of electrical protection of buildings against atmosph... more In electrical protection, there is a method of electrical protection of buildings against atmospheric discharges called the electro-geometric method or the rolling sphere method. So far, it is possible to achieve the implementation of this method graphically, that is, representing through plans and technical drawings, the protection conditions of the analyzed structure and obtaining from these graphic representations the protection parameters with the consequent errors caused by the scales and dimensions of the work plane. In the present work, a mathematical model is obtained that allows, using specific calculations, to analyze the dynamic behavior of a protection system against atmospheric discharges without worrying about the limitations given by the scales and planes. The set of equations obtained in the model allows us to determine the different parameters that define the protection system against atmospheric discharges (lightning) without depending on the graphical representati...
Journal of Vibration Engineering & Technologies, 2025
Background and Objectives The complexity of quadrotor unmanned aerial vehicles (UAVs) in nonlinea... more Background and Objectives The complexity of quadrotor unmanned aerial vehicles (UAVs) in nonlinear environments poses significant challenges, including path tracking, dealing with uncertainties, disturbances, and actuator faults. This study aims to improve the robustness and tracking ability of quadrotors by developing and analyzing multiple advanced control methods and their combinations, with a special focus on adaptive feedback linearization and sliding mode control strategies. Methods The research develops mathematical models for quadrotor dynamics and implements four controller schemes: Standard Feedback Linearization Control (FLC), Adaptive Feedback Linearization Control (AFLC), Standard Sliding Mode Control (SMC), and Adaptive Sliding Mode Control (ASMC). Combinations of these controllers are also explored. The controllers are evaluated under simulated scenarios both with and without the presence of various disturbances and noise (white and colored noise). Key performance indicators include tracking error, stability (verified via Lyapunov functions), response time, and robustness against uncertainties. Results Simulation results demonstrate: Noise-free environments: FLC and AFLC controllers show superior trajectory tracking performance with smoother control inputs and lower angular velocities. Disturbed environments (white and colored noise): ASMC and SMC outperform other methods, maintaining position and attitude tracking effectively under uncertainty. Controller combinations: Adaptive controller combinations, particularly AFLC and ASMC, yield significant improvements in robustness and stability, effectively minimizing trajectory tracking error and unnecessary control input variations. Conclusions The integration of adaptive feedback linearization and adaptive sliding mode control offers a robust approach to quadrotor control, capable of addressing external disturbances and uncertainties. The proposed control schemes enhance tracking accuracy and system stability under both ideal and challenging conditions, making them suitable for real-world UAV applications.
Sustainability, 2025
Optimizing wind turbine control is a major challenge due to wind variability and nonlinearity. Th... more Optimizing wind turbine control is a major challenge due to wind variability and nonlinearity. This research seeks to improve the performance of wind turbines by designing and developing hybrid intelligent controllers that combine advanced artificial intelligence techniques. A control system combining deep neural networks and fuzzy logic was implemented to optimize the efficiency and operational stability of a 3.5 MW wind turbine. This study analyzed several deep learning models (LSTM, GRU, CNN, ANN, and transformers) to predict the generated power, using data from the SCADA system. The structure of the hybrid controller includes a fuzzy inference system with 28 rules based on linguistic variables that consider power, wind speed, and wind direction. Experiments showed that the hybrid-GRU controller achieved the best balance between predictive performance and computational efficiency, with an R 2 of 0.96 and 12,119.54 predictions per second. The GRU excels in overall optimization. This study confirms intelligent hybrid controllers' effectiveness in improving wind turbines' performance under various operating conditions, contributing significantly to the field of wind energy.
Energies, 2025
This paper presents research results to improve energy efficiency in one of the crude oil heating... more This paper presents research results to improve energy efficiency in one of the crude oil heating furnaces at the "Hermanos Díaz" refinery in Santiago de Cuba, Cuba. It analyzes the main process's variables and disturbances, and the multivariate dynamic behavior of the F-101 furnace temperature is characterized to evaluate different control strategies. In addition, the design of a linear regulation control law was implemented as a way to solve the limitations of the existing control of the furnace, to control the plant for the first time with a multivariable approach, demonstrating superior performance by guaranteeing decoupling between the variables, decreasing the overruns by 6%, and increasing the response speed of the system by more than 5 min. The comparison with results obtained with other control strategies allowed us to determine the better performance of the furnace by increasing its energy efficiency, evidencing the economic and environmental impact and obtaining as benefits a better dynamic behavior by reducing fuel oil consumption by 5%, equivalent to 0.74 m 3 /day, which reduces the operating costs of the plant, the temperature of the gasses by 2%, emissions of CO pollutant gas to the environment by between 3 and 5%, and increasing energy efficiency by 1.5%.
TELKOMNIKA Telecommunication Computing Electronics and Control, 2025
Production processes in modern industry demand higher levels of quality and efficiency in their p... more Production processes in modern industry demand higher levels of quality and efficiency in their products. The "Hermanos Díaz" Oil Refinery Company of Santiago de Cuba, a fundamental pillar in the economic and social development of the eastern part of the country, has a chemical water treatment plant responsible for supplying processed water to the industry's boilers. The current state of this plant supports the lack of optimal physicalchemical conditions in the water it delivers and, therefore, the gradual deterioration of the boilers. This work conceives an automation solution for the dosing, precipitation, and clarification processes of the chemical water treatment plant. Control systems were designed based on instrumentation proposals, enabling reliable measurements and practical actions. In addition, an algorithm of supervision and automatic control using a programmable programmable logic controller (PLC) is presented, making the plant capable of delivering a product in optimal conditions. Images were designed for local and remote process control using a human-machine interface (HMI) panel and a supervisory control and data acquisition (SCADA) system. Finally, an automation architecture with a decentralized periphery is proposed to ensure safety and accuracy in the system's decision-making through communication protocols.
MethodsX, 2025
This research explores implementing renewable energy technologies for power generation using mult... more This research explores implementing renewable energy technologies for power generation using multi-criteria decision-making (MCDM) methods, including AHP, FAHP, TOPSIS, and FUZZY-TOPSIS. Ten renewable energy alternatives were evaluated across seven geographic regions in Colombia, revealing preference variability depending on the method and scenario.
International Journal of Thermofluids, 2024
This study focuses on the experimental investigation of the efficiency of a humidifier-dehumidifi... more This study focuses on the experimental investigation of the efficiency of a humidifier-dehumidifier (HDH) desalination process. The system employs a closed-air cycle, utilizing a hybrid (solar-electric) air heater to increase the air temperature before entering the humidifier. Additionally, a Vapor Absorption Refrigeration (VAR) system is employed to decrease the temperature of the water before it enters the dehumidifier. The system is suitable for deployment in regions with high temperatures and humidity levels. Tests have been conducted under prevailing weather conditions. Temperature and relative humidity at various stages of the cycle are measured and recorded using a dedicated sensor. This study examines the effects of different parameters, including air mass flow rate (MFR) and air temperature at the humidifier inlet, on fresh water production (FWP), coefficient of performance (COP), and gained output ratio (GOR). The results section presents the experimental findings, which show that the maximum COP, GOR, and FWP achieved values of 2.1, 4.1, and 200 g/h, respectively. Furthermore, an increase in air MFR corresponds to an increase in both COP and FWP, while GOR values show a decrease. Based on the eco-analysis conducted for this investigation, the cost per liter (CPL) was calculated to be 0.
Processes, Nov 14, 2022
The number of injector holes and the fuel-injection pressure in an internal combustion engine can... more The number of injector holes and the fuel-injection pressure in an internal combustion engine can affect engine performance and exhaust emissions. Conversion of a port-injection gasoline engine to an HCNG direct-injection engine improves engine performance and exhaust emissions. In addition, increasing the injection pressure helps to increase engine performance. In this study, AVL Fire software was used to perform simulation by certain adjustments. The injection pressure was applied in mods of 15, 20, and 25 bars, the injector holes numbers were 3 and 6, the compression ratio changed from 10:1 to 14:1, and the amount of hydrogen enrichment to natural gas was in mods of 10%, 20%, 30%, and 40%. This paper discusses the items above with regard to power, torque, combustion chamber pressure, fuel conversion efficiency, and exhaust emissions. The result determined that increasing the number of injector holes improves the performance engine and reduces CO emission so that the contour plots confirmed the balanced distribution of temperature and pressure. According to obtained results, maximum engine performance improved from 2.5% to 5% at different speeds and 30% added hydrogen, 25 bar injection pressure, and 6-hole injectors. The amount of CO decreased by approximately 30%, and NOx increased by about 10%.
Modeling and control of the hydraulic actuator in a ladle furnace
Heliyon
The dynamic behavior of the hydraulic actuator in a system for regulating the electrode's... more The dynamic behavior of the hydraulic actuator in a system for regulating the electrode's position is crucial for the operation of a Ladle Furnace. This work aims to identify, model, and control the hydraulic actuator in the Ladle Furnace of ACINOX Las Tunas. For identifying the system, input signals of Pseudo-Random Binary type and black box models were used. As a result, three models were obtained, two reflecting the process's asymmetric behavior according to the upward or downward movement. The third model approximates the process dynamic behavior around the operating point and includes the uncertainty caused by the weight variation during the electrode wear. The models obtained, with a fit greater than 85%, allow a better understanding of the study case behavior. In addition, these allowed the evaluation of the electrode's weight variation and tuning of several controllers. The optimal one was a novel non-linear PI controller of guaranteed robustness. In future works, the use of a non-linear function could be evaluated to compensate for the asymmetric behavior of the process.
International Journal of Power Electronics and Drive Systems (IJPEDS)
Three speed-control strategies for DC and AC drives are presented in this study: a proportional i... more Three speed-control strategies for DC and AC drives are presented in this study: a proportional integral derivative (PID) control strategy; an internal model control (IMC); and a state-space control by pole assignment with full state observer (ESSO). The three strategies are applied to a case study, demonstrating the potential of each one. Experimental identification was used to obtain the drive models used for the synthesis of the controllers. The three strategies showed satisfactory results when compared with the requirements imposed on the system, in addition to the good rejection of disturbances. However, the IMC strategy showed itself to be a little softer and with no maximum overshoot, which in some cases and some applications is usually a restriction.
Lubricants
A single effect LiBr–H2O absorption refrigeration system coupled with a solar collector and a sto... more A single effect LiBr–H2O absorption refrigeration system coupled with a solar collector and a storage tank was studied to develop an assessment tool using the built-in App Designer in MATLAB®. The model is developed using balances of mass, energy, and species conservation in the components of the absorption cooling system, taking into account the effect of external streams through temperature and pressure drop. The whole system, coupled with the solar energy harvesting arrangement, is modeled for 24 h of operation with changes on an hourly basis based on ambient temperature, cooling system load demand, and hourly solar irradiation, which is measured and recorded by national weather institutes sources. Test through simulations and validation procedures are carried out with acknowledged scientific articles. These show 2.65% of maximum relative error on the energy analysis with respect to cited authors. The environmental conditions used in the study were evaluated in Barranquilla, Colo...
Energy Repowering Using Photovoltaic Microgrids - A Case Study in the Province of Manabí in Ecuador
International Journal on Engineering Applications (IREA)
Currently, in Ecuador, the participation of photovoltaic energy is practically symbolic. In the p... more Currently, in Ecuador, the participation of photovoltaic energy is practically symbolic. In the province of Manabí, generation continues to be carried out through the intensive use of fossil fuel, which is expensive, inefficient, and polluting. This happens in a territory with optimal potential. Hence, the objective of the work is to demonstrate the feasibility of introducing a photovoltaic microgrid through the case study. Due to its simplicity and versatility, a methodology was applied to generalize experiences in other territories with similar geographical and climatic conditions. Field research was applied, and the method corresponds to the descriptive-deductive method, using a Geographic Information System (GIS) as a geographic information manager. The PVsyst 6.8.6 tool was used for the technical design of the installation, and the HOMER software was used for the economic feasibility analysis. The results demonstrate the relevance of introducing the photovoltaic microgrid in the distributed generation mode to increase the quality of service and the system's efficiency, reduce energy costs, promote the preservation of natural resources, and reduce CO2 emissions environment.
Journal of Engineering Science and Technology Review
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Papers by José R Nuñez-Alvarez