Mechanical analysis of Genoa 03 stirling engine

Due to the new technologies development based on renewable sources of energy, in recent years Stirling engines have become very important in the energetic sector. Many of them do not allow the use of fluid lubricants and, thus, the effect of friction losses is important. For this purpose, a mathematical model has been developed based on the force balance in the crankshaft using the pressure distribution in the cylinders. The aim of this work is to characterize the mechanical losses in a Genoa 03 Stirling engine using a numerical model and experimentally via the drag method. The results of this model have been compared with those obtained experimentally on Genoa 03 Stirling engine. In the experimental results, a proportional increase in friction torque due to the average pressure and the speed of the crankshaft is observed. The first of these is caused by an increase of dry friction forces and the second, by the viscous friction between the working fluid and the inner walls of the engine. Also in this paper, irreversible processes in a beta type Stirling engine have been investigated in order to highlight the impact of losses on mechanical power and its performance. This article develops the first study of the mechanical losses of Genoa 03 experimental Stirling engine, which has an output power of 3 kW. Although the model response follows the same trends as the experiments, those simplifications provide errors which become more significant as the engine speed increases.Ministerio de Economía y Competitividad ENE2013-43465-

Optimización del diseño del conducto de admisión del motor F1L2006

En el presente trabajo se describe la caracterización aerodinámica del conducto de admisión de un motor de encendido por compresión monocilíndrico con refrigeración por aire. Para ello se estudia la evolución para cada configuración operativa del coeficiente de descarga y del swirl mediante experimentación y simulación con un código de cálculo fluidodinámicoIn the present work the aerodynamic characterization of the intake duct of an air cooled single cylinder compression ignition engine is described. The discharge coefficient and swirl for each configuration is studied by means of experimentation and simulation with a computational fluid dynamics code

Análisis numérico bidimensional de cascadas de turbomaquinas térmicas con flujos compresibles viscosos

Este artículo aborda la validación de una herramienta numérica, basada en técnicas de volúmenes finitos, para el estudio de flujos bidimensionales, compresibles, viscosos, previamente desarrollada, tras su adaptación a un mallador genérico comercial. Se describen las modificaciones añadidas al código original, de manera que se contemplen de manera adecuada las irregularidades del mallado, indicando la formulación empleada. Finalmente se presentan los resultados para dos configuraciones de cascadas de turbomáquinas axiales con perfiles NACA 65010 y C4 con diferentes incidencias.In this work the adaptation of a CFD code to highly unstructured meshes generated from a commercial code has been presented. The CFD code was previously developed within this group, and it solves the Navier-Stokes equations for viscid and compressible flows with finite volume techniques (SIMPLE and PISO). The main corrections are commented and the corrected code have been applied to the analysis of turbomachinery cascades

Thermodynamic Model for Performance Analysis of a Stirling Engine Prototype

In this study, the results of simulations generated from different thermodynamic models of Stirling engines are compared, including characterizations of both instantaneous and indicated operative parameters. The aim was to develop a tool to guide the decision-making process regarding the optimization of both the performance and reliability of Stirling engines, such as the 2.9 kW GENOA 03 unit—the focus of this work. The behavior of the engine is characterized using two different approaches: an ideal isothermal model, the simplest of those available, and analysis using the ideal adiabatic model, which is more complex than the first. Some of the results obtained with the referred ideal models deviated considerably from the expected values, particularly in terms of thermal efficiency, so a set of modifications to the ideal adiabatic model are proposed. These modifications, mainly related to both heat transfer and fluid friction phenomena, are intended to overcome the limitations due to the idealization of the engine working cycle, and are expected to generate results closer to the actual behavior of the Stirling engine, despite the increase in the complexity derived from the modelling and simulation processes.Ministerio de Economía y Competitividad ENE2013-43465-

Methodology for the estimation of cylinder inner surface temperature in an air-cooled engine

A methodology for the estimation of the mean temperature of the cylinder inner surface in an air-cooled internal combustion engine is proposed. Knowledge of this temperature is necessary to determine the heat flux from the combustion chamber to the cylinder wall. Along with the heat transfer coefficient this parameter also allows almost 50% of engine heat losses to be determined. The temperature is relatively easy to determine for water-cooled engines but this is not in the case for air-cooled engines. The methodology described here combines numerical and experimental procedures. Simulations were based on FEM models and experiments were based on the use of thermocouples and infrared thermography. The methodology avoids the use of data or correlations developed for other engines, providing more reliable results than extrapolating models from one engine to another. It also prevents from taking measurements from inside the combustion chamber, reducing invasion and experiments complexity. The proposed methodology has been successfully applied to an air-cooled four-stroke direct-injection diesel engine and it allows the cylinder mean inner surface temperature and cylinder-cooling air heat transfer coefficient to be estimated.Ministerio de Eduación y Ciencia CTQ2007-68026-CO2-02/PP

Analysis of a new analytical law of Heat Release Rate (HRR) for Homogeneous Charge Compression Ignition (HCCI) combustion mode versus analytical parameters

Homogeneous charge compression ignition (HCCI) engines produce very low NO and soot emissions and alsoimprove engine efficiency when compare to conventional spark ignition engines. The combustion process bases on the self-ignition of a homogenous air-fuel mixture without an external ignition source. The gas temperature is very important to initiate the combustion and to promote the appropriate chemical kinetics. As a result, the heat release rate and heat transfer inside the combustion chamber play a significant role in the HCCI combustion mode. The high relevance of gas temperature on this combustion mode means that heat transferis considered through a dedicated heat transfer model. In this system the forced convection from hot gases to the combustion chamber walls is the dominant heat transfer mechanism. This paper focuses on the relationship between HRR in HCCI combustion mode and the four parameters that are required for an analytical function to model this heat release rate. More specifically, the influences of the fuel-air equivalence ratio, engine speed and EGR on the four parameters that control HRR are examined. The analytical HRR law is validated over a wide range of operating conditions in HCCI combustion mode and shows that these four parameters are directly related to any load condition, including engine speed, fuel rate and EGR. These parameters can therefore be used to characterize this combustion mode.Ministerio de Ciencia y Eduación CTQ2007-68026-CO2-02/PP

Nuevas técnicas metodologías para el fomento de habilidades transversales y transferencia del conocimiento en universitarios

Knowledge transference and its business potential are very much related to founders’ skills, and especially to the development of their transversal skills. Unfortunately, the time needid to achieve these skills spontaneously penalizes their possibilities. The implementation of pilot experiences in application of agile innovation methodologies such as "Lean Startup" and "Scrum" to real business projects during their incubation and acceleration process at the University of Seville has thrown interesting data about the best work dynamics during the process, with measurements of productivity, the "momentum" of the project, its "focus abilities" or qualitative assessments of those involved in the study. The results reveal a series of advantages and disadvantages derived from the application of these methodologies, which exert influence both on the individual performance and on the group of founders, that in general have turned out to be positive, since they allow to accelerate the maturation process to achieve the skills needed to increase survival ratios, or to conclude that it is not a viable project by making use of significantly less time and resources.La transferencia del conocimiento y su potencial empresarial están muy relacionadas con la capacidad del equipo promotor, y especialmente con el desarrollo de habilidades transversales. Por desgracia, el tiempo necesario para lograr estas habilidades de forma espontánea penaliza sus posibilidades. La puesta en marcha de experiencias piloto de aplicación de metodologías ágiles de innovación como “Lean Startup” y “Scrum” a proyectos empresariales reales durante su proceso de incubación y aceleración en la Universidad de Sevilla ha permitido obtener datos interesantes acerca de la dinámica de trabajo individual y grupal registrada durante el proceso, con mediciones de la productividad, el “nivel de inercia” del proyecto, su “capacidad de foco” o valoraciones cualitativas de los implicados en el estudio. Los resultados descubren una serie de ventajas e inconvenientes derivados de la aplicación de estas metodologías, que ejercen influencia tanto en el desempeño individual como del conjunto de fundadores del proyecto, y en líneas generales han resultado ser positivos, ya que permiten acelerar el proceso de maduración personal hacia la consecución de las habilidades necesarias para incrementar la supervivencia del proyecto, o bien para concluir que no es viable haciendo uso de una cantidad significativamente inferior de tiempo y recursos

Análisis de la dinámica de un grupo motobomba diesel: Implicaciones en las causas de rotura

En este artículo se analizan las causas de las averías sistemáticas que se producen en un grupo motobomba. Éstas consisten en la rotura de los rotores de la bomba (6 etapas) por la sección de admisión así como del cierre. El análisis se ha desarrollado en tres etapas: a) desarrollo de un modelo dinámico de torsión, b) desarrollo de un modelo dinámico para identificación de velocidades críticas, c) validación experimental y medida de magnitudes instantáneas. El análisis ha permitido identificar de forma inequívoca la operación de la motobomba muy próxima a una resonancia a torsión del sistema, lo que ha provocado un deterioro prematuro del chavetero así como la abrasión de los rotores.In this paper the causes of a pump-engine systematic failure are analyzed. These consist of the breakage of the rotors of the pump (6 stages) by the admission section as well as of the closing. The analysis has been developed in three steps: a) development of a torsion dynamic model b) development of a dynamic model in order to identify the critics speeds, c) experimental validation and measure of instantaneous parameters. The analysis has allowed identifying the operation of the pump-motor system closely to a torsion resonance, which has caused a premature deterioration of the keyway, as well as the abrasion of the rotors

Software educacional para la simulación de motores de combustión interna alternativos

XVIII Congreso Universitario de Innovación Educativa en las Enseñanzas Técnicas. Escuela Técnica Superior de Ingenieros Industriales y de Telecomunicación. Universidad de Cantabria. Santander, 6 a 9 de julio de 2010Se describe una herramienta virtual que permite la simulación detallada del funcionamiento de un motor diesel, así como un análisis paramétrico y de sensibilidad de estos motores. Ello es debido a la continua necesidad para un ingeniero de entender y aplicar modelos matemáticos en la simulación de motores. La herramienta se ha desarrollado en lenguaje MATLAB y el empleo de la herramienta puede ayudar a realizar simulaciones en lugar de ensayos difíciles de llevar a cabo en el laboratorio. El empleo de la herramienta permite entender el funcionamiento de los motores diesel en distintas condiciones operativas. Los resultados de la simulación son visualizados mediante el uso de “graphical user interface (GUI)”. Se han obtenido muy buenos resultados por parte de los alumnos con el uso de esta herramientaThis article describes a virtual instrument that allows a detailed diesel engine simulation performance and parametric analysis of the combustion process. The stimulus for developing this computer-aided educational tool derives from the continuing need of the engineer to understand and apply mathematical models in engine simulation. Common programming language Matlab is selected to develop the software and interfaces. The application of software in teaching internal combustion engines can help students to improve their parametric analysis and make them understand diesel combustion better. Simulation and parametric analysis are visualized on the designed graphical user interface (GUI). The software has been used by students who have achieved excellent results by using this teaching tool

Desarrollo de una herramienta numérica basada en técnicas de volúmenes finitos para el estudio de flujos en un amplio rango de números de Mach

El presente trabajo describe la herramienta numérica para el estudio de problemas fluido-mecánicos bidimensionales, basada en técnicas de discretización mediante volúmenes finitos. Esta herramienta plantea las ecuaciones de Navier-Stokes, sin simplificaciones en sus términos, buscando la máxima generalidad de la misma. permitiendo la posibilidad de abarcar un amplio abanico de problemas de muy diversa naturaleza. Se presentan las técnicas y criterios empleados para el desarrollo de la herramienta, así como su validación con diferentes problemas fluido-mecánicos, relacionados con distintas características de flujo, mostrando la versatilidad del mismo