Model of the expansion process for R245fa in an Organic Rankine Cycle (ORC)

An Organic Rankine Cycle (ORC) is considered as one of the most environmental-friendly ways to convert different kinds of low temperature energies, i.e. solar, geothermal, biomass and thermal energy of exhaust gases into electrical energy. Two important facts about the ORC must be considered: An organic fluid is selected as the working fluid and a high expansion ratio is usually presented in the machinery due to thermodynamic and efficiency factors. In the past, the pre-design of turbomachinery has been based on the usage of ideal fluid laws, but the real gas effects have a significant influence in the ORC working condition, due to its proximity to the saturation vapor line. In this article, the Equations of State (EoS) (Ideal gas, Redlich-Kwong-Soave and Peng-Robinson) have been evaluated in a typical ORC expansion in order to observe the inaccuracies of the ideal gas model with different thermodynamic variables. Finally an isothermal process followed by an isochoric process is proposed to reproduce the thermodynamic process of the organic fluid expansion by means of simpler equations. In the last point of this paper, several examples of this expansion process have been calculated, in order to analyze the proposed methodologies. It has been concluded that in typical expansion process of ORC (2.5 MPa-0.1 MPa and 1.6MPa-0.1MPa), the PR and RKS equations show deviations between 6% and 8% in specific energy. These deviations are very low compared with the ideal gas equation whose deviations are above 100 %.This work was partially funded by the "Programa de Formacion de Profesorado Universitario (F.P.U)", "Programa de Apoyo a la Investigacion y Desarrollo de la Universidad Politecnica de Valencia 2010", "Proyectos I+D para grupos de investigacion emergentes 2011" and "Programa de apoyo a la investigacion y desarrollo de la U.P.V (PAID-06-09)". The authors thanks to R. Gatzweiler for his help to improve the English grammar.Lujan Martinez, JM.; Serrano Cruz, JR.; Dolz Ruiz, V.; Sánchez Serrano, J. (2012). Model of the expansion process for R245fa in an Organic Rankine Cycle (ORC). Applied Thermal Engineering. 40:248-257. https://doi.org/10.1016/j.applthermaleng.2012.02.020S2482574

Methodology to design a bottoming Rankine cycle, as a waste energy recovering system in vehicles. Study in a HDD engine

This article describes a methodology for the optimization of a bottoming cycle as a waste heat recovering system in vehicles. The methodology is applied to two particular cases in order to evaluate the preliminary energetic and technical feasibility of the implementation of a bottoming cycle in a heavy duty diesel (HDD) engine considering two different criteria. Initially, a study of the different waste heat sources of the engine is described. In this study, the power and exergy of each heat source is quantified, in order to evaluate which sources are suitable to be used in the bottoming cycle. The optimum working fluids to run the cycles are selected (water and R245fa). Then, the ideal Rankine cycle is optimized for the two different working fluids and different sets of heat sources (all the available heat sources and the sources with high exergy respectively) throughout the engine operating range, reaching a maximum improvement of 15% of the fuel consumption of the engine. Later, a study of the minimum temperature difference between the hot and cold flow of the heat exchangers is described. The improvements in fuel consumption and the size of the installed heat exchanger are related to this temperature difference. Finally, the non-ideal behavior of the machines (pump and expander) is analyzed, obtaining a maximum improvement of 10% in brake specific fuel consumption (bsfc).This work was partially funded by the "Programa de Formacion de Profesorado Universitario (FPU)", "Programa de Apoyo a la Investigacion y Desarrollo de la Universidad Politecnica de Valencia 2010", "Proyectos I + D para grupos de investigacion emergentes 2011" and "Programa de apoyo a la investigacion y desarrollo de la U.P.V (PAID-06-09)". The authors thank J. Dahlqvist for his help in improving the English grammar.Macian Martinez, V.; Serrano Cruz, JR.; Dolz Ruiz, V.; Sánchez Serrano, J. (2013). Methodology to design a bottoming Rankine cycle, as a waste energy recovering system in vehicles. Study in a HDD engine. Applied Energy. 104:758-771. https://doi.org/10.1016/j.apenergy.2012.11.075S75877110

Behavior of an IC Engine Turbocharger in Critical Conditions of Lubrication

Problems in the turbocharger lubrication system can cause serious deterioration in their overall performance and even their complete destruction. The paper describes several tests with different critical lubrication conditions, in order to determine the thresholds at which the operation may be appropriate. In an IC engine, these problems can be produced mainly by several factors: the decreasing in the supply pressure of the oil, a delay in the lubrication oil pressure and an intermittent lubrication interruption. A turbocharger test bench and an IC engine test bench has been used to test the turbocharger, in order to reproduce the conditions and cycles similar to the operation of the turbocharger in an IC engine (pressures, temperatures, mass flows, accelerations, etc..). Thermodynamic variables and mechanic variables measured in the tests help to identify some of the operating limits of lubrication in critical conditions. In addition, optical techniques have been combined with accelerometer measurements, in order to detect modifications in the movement of the turbocharger shaft. The main conclusions obtained from these tests are that accelerations from low rotational speed to 100krpm, without lubrication oil in the bearing system, don’t cause significant problems in the turbocharger, for 20 sec. However, the accelerations to 150krpm can cause critical problems depending on the lubrication delay and the bearing configuration. Finally, higher acceleration rates to 200krpm, without lubrication, cause the turbocharger destruction in a few seconds. By other hand, a low oil inlet pressure given by an oil column, of about 1m in height, allows to the turbo survive during accelerations from low rotational speed to 150 krpm.Galindo, J.; Serrano Cruz, JR.; Dolz Ruiz, V.; López Hidalgo, MA.; Bouffaud, F. (2013). Behavior of an IC Engine Turbocharger in Critical Conditions of Lubrication. SAE International Journal of Engines. 6(2):1-9. doi:10.4271/2013-01-0921S196

Brayton cycle for internal combustion engine exhaust gas waste heat recovery

An average passenger car engine effectively uses about one-third of the fuel combustion energy, while the two-thirds are wasted through exhaust gases and engine cooling. It is of great interest to automotive industry to recover some of this wasted energy, thus increasing the engine efficiency and lowering fuel consumption and contamination. Waste heat recovery for internal combustion engine exhaust gases using Brayton cycle machine was investigated. The principle problems of application of such a system in a passenger car were considered: compressor and expander machine selection, machine size for packaging under the hood, efficiency of the cycle, and improvement of engine efficiency. Important parameters of machines design have been determined and analyzed. An average 2-L turbocharged gasoline engine's New European Driving Cycle points were taken as inlet points for waste heat recovery system. It is theoretically estimated that the recuperated power of 1515 W can be achieved along with 5.7% improvement in engine efficiency, at the point where engine power is 26550 W.Galindo, J.; Serrano Cruz, JR.; Dolz Ruiz, V.; Kleut, P. (2015). Brayton cycle for internal combustion engine exhaust gas waste heat recovery. Advances in Mechanical Engineering. 7(6):1-9. doi:10.1177/16878140155903141976Bredel, E., Nickl, J., & Bartosch, S. (2011). Waste Heat Recovery in Drive Systems of Today and Tomorrow. MTZ worldwide, 72(4), 52-56. doi:10.1365/s38313-011-0042-0Freymann, R., Strobl, W., & Obieglo, A. (2008). The turbosteamer: A system introducing the principle of cogeneration in automotive applications. MTZ worldwide, 69(5), 20-27. doi:10.1007/bf03226909Freymann, R., Ringler, J., Seifert, M., & Horst, T. (2012). The Second Generation Turbosteamer. MTZ worldwide, 73(2), 18-23. doi:10.1365/s38313-012-0138-1Glavatskaya, Y., Podevin, P., Lemort, V., Shonda, O., & Descombes, G. (2012). Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application. Energies, 5(6), 1751-1765. doi:10.3390/en5061751Song, B., Zhuge, W., Zhao, R., Zheng, X., Zhang, Y., Yin, Y., & Zhao, Y. (2013). An investigation on the performance of a Brayton cycle waste heat recovery system for turbocharged diesel engines. Journal of Mechanical Science and Technology, 27(6), 1721-1729. doi:10.1007/s12206-013-0422-2Dolz, V., Novella, R., García, A., & Sánchez, J. (2012). HD Diesel engine equipped with a bottoming Rankine cycle as a waste heat recovery system. Part 1: Study and analysis of the waste heat energy. Applied Thermal Engineering, 36, 269-278. doi:10.1016/j.applthermaleng.2011.10.02

Optimization of the inlet air line of an automotive turbocharger

This paper presents different aspects of air inlet behaviour near the inducer of a radial compressor and shows how the geometry can contribute to its stability and performance. Unfortunately, the space reserved for installation of an automotive turbocharger in a vehicle is constantly being reduced, so it is necessary to study the effects that elbows and abrupt changes in flow directions originate on the compressor performance. The work presented in this paper studies the effect that different 90 degrees elbows have on the compressor with respect to its ideal, straight, no-elbow configuration, in order to obtain the best possible elbow configuration. The methodology followed has been to, initially, study different geometries in computational fluid dynamics code in order to obtain the best possible configuration. Then, several 90 degrees elbows were constructed and characterized on a continuous flow test bench in order to validate the computational fluid dynamics results and to obtain optimum results. The elbows were then installed on a radial compressor and tested on a hot, continuous turbocharger test bench, where the compressor was characterized and maps were obtained with each different elbow. The results were compared with respect to the ideal, no-elbow configuration, which was taken as the base performance. After analysing the results obtained, it is possible to observe that in most of the cases, the elbows have a negative effect on the compression ratio, which tends to be reduced, especially at high rotor velocities and high air mass flow. On the other hand, the effect on the surge limit seems to be positive, as the surge line shifts to lower air mass flows, although the maximum mass flow allowed is reduced. It seems as if the compressor map shifts to the left with a reduction in compression ratio. From theoretical and experimental studies, it has been concluded that flow uniformity index and pressure loss are the most important factors affecting the performance of the compressorSerrano Cruz, JR.; Margot, X.; Tiseira Izaguirre, AO.; García-Cuevas González, LM. (2013). Optimization of the inlet air line of an automotive turbocharger. International Journal of Engine Research. 14(1):92-104. doi:10.1177/1468087412449085S92104141Soranna, F., Chow, Y.-C., Uzol, O., & Katz, J. (2005). The Effect of Inlet Guide Vanes Wake Impingement on the Flow Structure and Turbulence Around a Rotor Blade. Journal of Turbomachinery, 128(1), 82-95. doi:10.1115/1.2098755Engeda, A., Kim, Y., Aungier, R., & Direnzi, G. (2003). The Inlet Flow Structure of a Centrifugal Compressor Stage and Its Influence on the Compressor Performance. Journal of Fluids Engineering, 125(5), 779-785. doi:10.1115/1.1601255Elder, R. L., & Gill, M. E. (1985). A Discussion of the Factors Affecting Surge in Centrifugal Compressors. Journal of Engineering for Gas Turbines and Power, 107(2), 499-506. doi:10.1115/1.3239759Canova, M. (2004). Development and validation of a control-oriented library for the simulation of automotive engines. International Journal of Engine Research, 5(3), 219-228. doi:10.1243/1468087041549625Kyrtatos, N. P., Tzanos, E. I., & Papadopoulos, C. I. (2003). Diesel engine control optimization for transient operation with lean/rich switches. International Journal of Engine Research, 4(3), 219-231. doi:10.1243/146808703322223333Mattarelli, E. (2009). Virtual design of a novel two-stroke high-speed direct-injection diesel engine. International Journal of Engine Research, 10(3), 175-193. doi:10.1243/14680874jer02509Galindo, J., Serrano, J. R., Margot, X., Tiseira, A., Schorn, N., & Kindl, H. (2007). Potential of flow pre-whirl at the compressor inlet of automotive engine turbochargers to enlarge surge margin and overcome packaging limitations. International Journal of Heat and Fluid Flow, 28(3), 374-387. doi:10.1016/j.ijheatfluidflow.2006.06.002Galindo, J., Serrano, J. R., Guardiola, C., & Cervelló, C. (2006). Surge limit definition in a specific test bench for the characterization of automotive turbochargers. Experimental Thermal and Fluid Science, 30(5), 449-462. doi:10.1016/j.expthermflusci.2005.06.00

Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications

[EN] Nowadays turbocharging the internal combustion engine has become a key point in the reduction on pollutant emissions and the improvement on engine performance. The matching between the turbocharger and the engine is vital due to the highly unsteady flow the turbocharger works with. In the present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be analyzed. This phenomenon will be studied from the point of view of both the turbine and the compressor in one-dimensional modelling. The goodness of the model will be demonstrated predicting turbine and compressor outlet temperatures. An accurate prediction of these parameters will be key designing the intercooler and the after treatment devices. A series of tests in a gas stand with steady and pulsating hot flow in the turbine side will be modeled to show the good agreement in turbocharger enthalpies prediction.This paper is partially supported by the Universitat Politècnica de València PAID-06-11 2034.Serrano Cruz, JR.; Olmeda González, PC.; Arnau Martínez, FJ.; Reyes Belmonte, MA.; Lefebvre, A. (2013). Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications. SAE International Journal of Engines. 6(2):1-13. doi:10.4271/2013-01-0576S1136

Importance of Mechanical Losses Modeling in the Performance Prediction of Radial Turbochargers under Pulsating Flow Conditions

This work presents a study to characterize and quantify the mechanical losses in small automotive turbocharging systems. An experimental methodology to obtain the losses in the power transmission between the turbine and the compressor is presented. The experimental methodology is used during a measurement campaign of three different automotive turbochargers for petrol and diesel engines with displacements ranging from 1.2 l to 2.0 l and the results are presented. With this experimental data, a fast computational model is fitted and used to predict the behaviour of mechanical losses during stationary and pulsating flow conditions, showing good agreement with the experimental results. During pulsating flow conditions, the delay between compressor and turbine makes the mechanical efficiency to fluctuate. These fluctuations are shown to be critical in order to predict the turbocharger behaviour.Serrano Cruz, JR.; Olmeda González, PC.; Tiseira Izaguirre, AO.; García-Cuevas González, LM.; Lefebvre, A. (2013). Importance of Mechanical Losses Modeling in the Performance Prediction of Radial Turbochargers under Pulsating Flow Conditions. SAE International Journal of Engines. 6(2):1-10. doi:10.4271/2013-01-0577S1106

Algoritmo de encriptado empleando sistemas caóticos de orden no entero en imágenes médicas

Una de las técnicas más eficientes para proteger las imágenes médicas es aplicar algoritmos basados en dinámica no lineal. En este trabajo se presenta un esquema de encriptación y compresión de imágenes médicas. El esquema se basa en sistemas caóticos de orden fraccionario, combinados con compresión por transformada de wavelet discreta. El encriptado realiza ciclos de operaciones digitales entre las soluciones del sistema dinámico y la imagen a encriptar, agregando las características de confusión y difusión a la imagen. Los resultados experimentales y análisis estadísticos muestran desempeños adecuados para aplicación en imágenes médicas en presencia de múltiples ataques y ruido

Derecho a una buena visión en los mayores: evitar la ceguera evitable. Prevención y cuidados para una atención integral

Este documento, que constituye el nº 8 de la colección Promoción de la salud en las personas mayores, pretende abordar buena parte de los problemas de salud de este colectivo aportando criterios y metodología para la intervención a sus cuidadores y responsables de salud