DEVELOPMENT OF A COMPUTATIONAL MODEL FOR A SIMULTANEOUS SIMULATION OF INTERNAL FLOW AND SPRAY BREAK-UP OF THE DIESEL INJECTION PROCESS

El proceso de atomización desde una vena o lámina líquida hasta multitud de gotas dispersas en un medio gaseoso ha sido un fenómeno de interés desde hace varias décadas, especialmente en el campo de los motores de combustión interna alternativos. Multitud de estudios experimentales han sido publicados al respecto, pues una buena mezcla de aire-combustible asegura una evaporación y combustión mucho más eficientes, aumentando la potencia del motor y reduciendo la cantidad de contaminantes emitidos. Con el auge de las técnicas computacionales, muchos modelos han sido desarrollados para estudiar este proceso de atomización y mezcla. Uno de los últimos modelos que han aparecido es el llamado ELSA (Eulerian-Lagrangian Spray Atomization), que utiliza un modelo Euleriano para la parte densa del chorro y cambia a un modelo Lagrangiano cuando la concentración de líquido es suficientemente pequeña, aprovechando de esta manera las ventajas de ambos. En el presente trabajo se ha desarrollado un modelo puramente Euleriano para estudiar la influencia de la geometría interna de la tobera de inyección en el proceso de atomización y mezcla. Se ha estudiado únicamente el proceso de inyección diésel. Este modelo permite resolver en un único dominio el flujo interno y el externo, evitando así las comunes simplificaciones y limitaciones de la interpolación entre ambos dominios resueltos por separado. Los resultados actuales son prometedores, el modelo predice con un error aceptable la penetración del chorro, el flujo másico y de cantidad de movimiento, los perfiles de velocidad y concentración, así como otros parámetros característicos del chorro.Martí Gómez-Aldaraví, P. (2014). DEVELOPMENT OF A COMPUTATIONAL MODEL FOR A SIMULTANEOUS SIMULATION OF INTERNAL FLOW AND SPRAY BREAK-UP OF THE DIESEL INJECTION PROCESS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43719TESISPremios Extraordinarios de tesis doctorale

Use of scoring rubrics for evaluating oral presentations in aerospace engineering education

[EN] Under the frame of Bologna system, alternative assessment methodologies gain significance in the evaluation process of the students. This article analyses the use of scoring rubrics for evaluating oral presentations of two different courses in aerospace engineering education, namelyAircraft Design and Aerodynamics II, at Universitat Politècnica de València. The score obtained at the presentation represents a significant percentage of the final grade for both courses. It has been observed that the students find difficulties to keep timing limitations overall. In addition, rubrics have proved to be a powerful tool to enhance some skills of the students, such as critical thinking and selfevaluation, although they may lead to unfairly high grades nonetheless.Tiseira Izaguirre, AO.; Martí-Aldaraví, P.; Navarro, R.; Carreres, M. (2015). Use of scoring rubrics for evaluating oral presentations in aerospace engineering education. En 1ST INTERNATIONAL CONFERENCE ON HIGHER EDUCATION ADVANCES (HEAD' 15). Editorial Universitat Politècnica de València. 50-56. https://doi.org/10.4995/HEAD15.2015.391OCS505

On the use of gamification tools for blended learning approaches in Thermodynamics courses

[EN] During the last year 2020, education in European universities has suffered a challenging transformation from an established pedagogical model to a digital one. The face-to-face formal lectures have been replaced to on-line sessions and blended learning approaches. The courses related to the Thermodynamics subject of two Bachelor of Science Degrees (Mechanical Engineering and Automatic and Industrial Electronic Engineering) have been also adapted to the blended learning approach, in this case combining the use of screencast videos, interactive slides with comments, synchronous on-line lectures and tutorials, and virtual laboratories. This recent methodology has been demonstrated to be effective due to its flexibility and ubiquitous characteristics. However, one of the difficulties is tracking the engagement and the evolution of the students due to the reduced direct interaction between them and the instructors. Among the technological tools that are used to benefit the learning process of students, gamification tools have been demonstrated to be effective and positive for academic performance. The aim of this study is to implement and evaluate the effectiveness of the gamification in the Thermodynamics courses where the proposed blended learning approach is used. One of the goals is to identify the specific competences acquired by the students after watching the audio-visual content (videos and slides). For this purpose, a Kahoot was played before starting the on-line lecture (synchronous), and according to the score, the instructor could recognize the level of understanding of the concepts. Based on the results, the instructor was able to focus more on the weaker learning objectives, capturing their attention during the session. At the end of the session the Kahoot was played again to recognize if the concepts were consolidated during the lesson. The results show that the use of this gamification tool achieved high levels of engagement and improved the attention and participation of the students.This work has been done in the framework of the innovative teaching group EICE CONMAGIA promoted by the Instituto de Ciencias de la Educación.Bracho León, GC.; Martí-Aldaraví, P.; García Tíscar, J.; Gómez Soriano, J. (2022). On the use of gamification tools for blended learning approaches in Thermodynamics courses. En Proceedings INNODOCT/21. International Conference on Innovation, Documentation and Education. Editorial Universitat Politècnica de València. 75-82. https://doi.org/10.4995/INN2021.2021.13370758

Effect of turbulence model and inlet boundary condition on the Diesel spray behavior simulated by an Eulerian Spray Atomization (ESA) model

Simulating liquid spray first and second atomization is not an easy task. Many models have been developed over the past years, but Eulerian ones have proved their better performance for the dense zone of the spray. In this work a new compressible Eulerian model is used to compute the internal flow together with the spray. Up to five two-equation turbulence models have been tested and its influence is remark- able in terms of spray behavior, but also greatly affects the mass flow rate and the momentum flux. At the end, SST k x model proves to be best than the others. Additionally, different types of inlet boundary con- ditions have been also tested and analyzed. Results when compared with previously obtained experimental data show that the commonly used for external flow time-varying velocity boundary condition gives also good performance for the internal flow.This research was funded in the frame of Project "Compresion de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo Diesel" reference TRA2012-36932 from Ministerio de Economia y Competitividad (Spanish Ministry of Economy).Salvador Rubio, FJ.; Gimeno García, J.; Pastor Enguídanos, JM.; Martí Aldaraví, P. (2014). Effect of turbulence model and inlet boundary condition on the Diesel spray behavior simulated by an Eulerian Spray Atomization (ESA) model. International Journal of Multiphase Flow. 65:105-116. https://doi.org/10.1016/j.ijmultiphaseflow.2014.06.003S1051166

Improving the effective communication soft skill in higher education engineering studies: an experience through written reports

[EN] With the new paradigm of higher education, courses syllabus are not only addressed to develop the knowledge in some specific contents, but also to let the student acquire a set of the so-called transversal competences or soft skills. Amongst these, the ability of the students to communicate in an effective manner is a soft skill that will present a key role in the future careers of the students. In this paper, the experience in two courses of the Aerospace Engineering Bachelor Degree working on the effective communication through written technical reports is presented. Different enhancements have been introduced over the years, including specific sessions to present best practices for written reports, assessment using rubrics or intermediate deliveries to provide feedback to the students before they deliver the final report. The analyzed courses belong to consecutive years and are taught in both Spanish and English, which provides a wide view for understanding the impact of each feature. With the current configuration, significant improvement in the students written reports readability is obtained. Their works are more rigorous in terms of writing and format. Nevertheless, the effect of these new features on the technical content of the reports is slight. Overall, the content is transmitted by the students in a more effective manner.Carreres Talens, M.; García-Cuevas González, LM.; Martí Gómez-Aldaraví, P.; Navarro García, R. (2020). Improving the effective communication soft skill in higher education engineering studies: an experience through written reports. Editorial Universitat Politècnica de València. 219-227. https://doi.org/10.4995/INN2019.2019.10128OCS21922

Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences

A new solver capable of calculating liquid and/or gas problems has been developed, verified and validated. Compressible solvers in Computational Fluid Dynamics use both mass flux and volumetric fluxes through the cell surface to calculate derivative terms. These fluxes depend on density and velocity fields, therefore the stability of the solver is affected by "how" and "where" density and velocity are calculated or updated. In addition to verification and validation, this paper deals with how different flux updates-equations sequences change the computational solution, reaching the conclusion that for mono-phase solvers no extra-updates should be used in order to minimize computational cost, but for multi-phase solvers with high density gradients an extra-update should be implemented to improve the stability of the solver.This research was funded in the frame the project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo Diesel" reference TRA2013-36932 from Ministerio de Enonomia y Competitividad (Spanish Ministry of Economy).Payri, R.; Ruiz Rosales, S.; Gimeno, J.; Marti-Aldaravi, P. (2015). Verification of a new CFD compressible segregated and multi-phase solver with different flux updates-equations sequences. Applied Mathematical Modelling. 39(2):851-861. https://doi.org/10.1016/j.apm.2014.07.011S85186139

A new approach to compute temperature in a liquid-gas mixture. Application to study the effect of wall nozzle temperature on a Diesel injector

[EN] Thermal effects on internal combustion engines have been always a hot topic. Its effects also on the injection system are still under research. In this work, a homogeneous model called Eulerian Spray Atomization (ESA) model is used to simulate Engine Combustion Network (ECN) Spray A conditions. A new approach is used for the thermodynamic model in Diesel spray simulations. Experimental values of the liquid enthalpy are directly used to obtain the temperature, without any need of knowing its heat capacity. This allows to accurately study heating and cooling phenomena inside the Diesel nozzle. The results show that two different boundary conditions can be applied at nozzle walls, either fixed temperature or adiabatic walls, and obtain good prediction of injection parameters. Also, the effect of fuel temperature has been investigated. For Spray A conditions, nozzle and spray parameters are the same regardless the fuel temperature, but fluid properties inside the nozzle (density, velocity...) significantly change.This research was performed in the frame of the project "Estudio de la interaccion chorro-pared en condiciones realistas de motor" reference TRA2015-67679-c2-1-R from Ministerio de Economia y Competitividad (Spanish Ministry of Economy). The equipment used in this work has been partially supported by FEDER Project funds "Dotacion de infraestructuras cientifico tectinas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", framed in the operation program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.Payri, R.; Gimeno, J.; Marti-Aldaravi, P.; Alarcón-Herrera, MY. (2017). A new approach to compute temperature in a liquid-gas mixture. Application to study the effect of wall nozzle temperature on a Diesel injector. International Journal of Heat and Fluid Flow. 68:79-86. https://doi.org/10.1016/j.ijheatfluidflow.2016.12.008S79866

Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector

In this work, lift-off length and ignition delay have been measured via chemiluminescence techniques in a wide range of conditions for a single-hole injector from the Engine Combustion Network (ECN) dataset and using a single component fuel (n-dodecane). In addition, Schlieren technique was used to characterize the ignition event using a new developed post-processing methodology capable of characterizing the "disappearance" phenomenon linked to the start of cool flames. Experiments have been carried out in a novel constant-pressure flow facility able of reproducing engine-like thermodynamic conditions. Results show that oxygen concentration seems to have a negligible impact on the start of cool flames. Empirical correlations have been obtained for the three measured parameters and they manifest similar trends of other previously published correlations for lift-off length and second stage ignition. These correlations also underline that the effect of oxygen concentration and ambient density is caught differently by chemiluminescence and Schlieren techniques, even though the absolute value of the measurements remains close. (C) 2013 Elsevier Ltd. All rights reserved.This work was sponsored by "Ministerio de Economia y Competitividad" of the Spanish Government in the frame of the Project "Comprension de la influencia de combustibles no convencionales en el proceso de inyeccion y combustion tipo diesel", Reference TRA2012-36932. Additionally, the Ph.D student Michele Bardi was financed by a grant from "Conselleria de educacio, cultura y esport" of the "Generalitat Valenciana" with Reference GRISOLIA/2010/010. This support is gratefully acknowledged by the authors.Benajes Calvo, JV.; Payri Marín, R.; Bardi, M.; Marti-Aldaravi, P. (2013). Experimental characterization of diesel ignition and lift-off length using a single-hole ECN injector. Applied Thermal Engineering. 58(1-2):554-563. https://doi.org/10.1016/j.applthermaleng.2013.04.044S554563581-

Desarrollo de un modelo computacional para el estudio simultáneo de flujo interno y atomización y mezcla del chorro diésel

[ES] Se ha desarrollado un nuevo modelo computacional en OpenFOAM capaz de calcular el flujo interno (no cavitante) y el flujo externo (en condiciones correspondientes a elevados números de Reynolds y Weber) del proceso de inyección en una misma simulación, sin necesidad de interpolación o condiciones de contorno complicadas. Se ha llevado a cabo de forma satisfactoria el proceso de verificación del mismo en casos monofásicos, tanto para líquidos como para gases, comparando con problemas que tienen solución analítica. A falta de completar la validación, los resultados preliminares en simulaciones de chorros son prometedores. Este nuevo modelo Euleriano - Euleriano tiene ciertas ventajas frente a sus competidores, ya sea en software de código abierto o comercial, pues utiliza un enfoque clásico para resolver la presión. Como resultado del trabajo realizado para su desarrollo, directo o indirecto, se han conseguido tres publicaciones en revistas internacionales[EN] new computational model has been developed in OpenFOAM. This model is able to calculate the internal flow (non-cavitating) and the external flow (under conditions corresponding to high Reynolds and Weber numbers) of the injection process in one single simulation, without need of interpolating or using complex boundary conditions. Verification process in mono-phase cases was successfully carried out, for either liquid or gas, through comparisons with problems which have analytical solution. Although validation is not completed yet, preliminary results on spray simulations are promising. This new Eulerian-Eulerian model has advantages over its competitors, either in open source or commercial software, because it uses a classical approach for solving the pressure. As result of the work, direct or indirect, done for its development, three articles have been published in international journals.Martí Gómez-Aldaraví, P. (2012). Desarrollo de un modelo computacional para el estudio simultáneo de flujo interno y atomización y mezcla del chorro diésel. http://hdl.handle.net/10251/27570Archivo delegad