Analysis of the energy balance during World harmonized Light vehicles Test Cycle in warmed and cold conditions using a Virtual Engine

This is the author's version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087419878593.[EN] In recent years, the interests on transient operation and real driving emissions have increased because of the global concern about environmental pollution that has led to new emissions regulation and new standard testing cycles. In this framework, it is mandatory to focus the engines research on the transient operation, where a Virtual Engine has been used to perform the global energy balance of a 1.6-L diesel engine during a World harmonized Light vehicles Test Cycle. Thus, the energy repartition of the chemical energy has been described with warmed engine and cold start conditions, analyzing in detail the mechanisms affecting the engine consumption. The first analysis focuses on the ¿delay¿ effect affecting the instantaneous energy balance due to the time lag between the in-cylinder processes and pipes: as a main conclusion, it is obtained that it leads to an apparent unbalance than can reach more than 10% of the cumulated fuel energy at the beginning of the cycle, becoming later negligible. Energy split analysis in cold starting World harmonized Light vehicles Test Cycle shows that in this condition the energy accumulation in the block is a key term at the beginning (about 50%) that diminishes its weight until about 10% at the end of the cycle. In warmed conditions, energy accumulation is negligible, but the heat transfer to coolant and oil are higher than in cold starting conditions (21% vs 28%). The lower values of the mean brake efficiency at the beginning of the World harmonized Light vehicles Test Cycle (only about 20%) is affected, especially in cold starting, by the higher mechanical losses due to the higher oil viscosity and the heat rejection from the gases. The friction plays an important role only during the first half of the cycle, with a percentage of about 65% of the total mechanical losses and 10% of the total fuel energy at the end of the World harmonized Light vehicles Test Cycle. However, at the end of the cycle, it does not affect dramatically the mean brake efficiency which is about 31% both in cold starting and warmed World harmonized Light vehicles Test Cycle.The author(s) disclosed receipt of the following financial support for the research, authorship and/or publication of this article: This research has been partially funded by the European Union's Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 ("DiePeR'') and by the Spanish government under the grant agreement TRA2017-89894-R. The authors wish to thank Renault SAS, especially P. Mallet and E. Gaiffas, for supporting this research.Olmeda, P.; Martín, J.; Arnau Martínez, FJ.; Artham, S. (2020). Analysis of the energy balance during World harmonized Light vehicles Test Cycle in warmed and cold conditions using a Virtual Engine. International Journal of Engine Research. 21(6):1037-1054. https://doi.org/10.1177/1468087419878593S10371054216Tauzia, X., Maiboom, A., Karaky, H., & Chesse, P. (2018). Experimental analysis of the influence of coolant and oil temperature on combustion and emissions in an automotive diesel engine. International Journal of Engine Research, 20(2), 247-260. doi:10.1177/1468087417749391Payri, F., Olmeda, P., Martin, J., & Carreño, R. (2014). A New Tool to Perform Global Energy Balances in DI Diesel Engines. SAE International Journal of Engines, 7(1), 43-59. doi:10.4271/2014-01-0665Tauzia, X., & Maiboom, A. (2013). Experimental study of an automotive Diesel engine efficiency when running under stoichiometric conditions. Applied Energy, 105, 116-124. doi:10.1016/j.apenergy.2012.12.034Abedin, M. J., Masjuki, H. H., Kalam, M. A., Sanjid, A., Rahman, S. M. A., & Masum, B. M. (2013). Energy balance of internal combustion engines using alternative fuels. Renewable and Sustainable Energy Reviews, 26, 20-33. doi:10.1016/j.rser.2013.05.049Ajav, E. A., Singh, B., & Bhattacharya, T. K. (2000). Thermal balance of a single cylinder diesel engine operating on alternative fuels. Energy Conversion and Management, 41(14), 1533-1541. doi:10.1016/s0196-8904(99)00175-2DIMOPOULOS, P., BACH, C., SOLTIC, P., & BOULOUCHOS, K. (2008). Hydrogen–natural gas blends fuelling passenger car engines: Combustion, emissions and well-to-wheels assessment. International Journal of Hydrogen Energy, 33(23), 7224-7236. doi:10.1016/j.ijhydene.2008.07.012TAYMAZ, I. (2006). An experimental study of energy balance in low heat rejection diesel engine. Energy, 31(2-3), 364-371. doi:10.1016/j.energy.2005.02.004Olmeda, P., Martín, J., Novella, R., & Blanco-Cavero, D. (2018). Assessing the optimum combustion under constrained conditions. International Journal of Engine Research, 21(5), 811-823. doi:10.1177/1468087418814086Durgun, O., & Şahin, Z. (2009). Theoretical investigation of heat balance in direct injection (DI) diesel engines for neat diesel fuel and gasoline fumigation. Energy Conversion and Management, 50(1), 43-51. doi:10.1016/j.enconman.2008.09.007Jia, M., Gingrich, E., Wang, H., Li, Y., Ghandhi, J. B., & Reitz, R. D. (2015). Effect of combustion regime on in-cylinder heat transfer in internal combustion engines. International Journal of Engine Research, 17(3), 331-346. doi:10.1177/1468087415575647Jung, D., Yong, J., Choi, H., Song, H., & Min, K. (2013). Analysis of engine temperature and energy flow in diesel engine using engine thermal management. Journal of Mechanical Science and Technology, 27(2), 583-592. doi:10.1007/s12206-012-1235-4Caresana, F., Bilancia, M., & Bartolini, C. M. (2011). Numerical method for assessing the potential of smart engine thermal management: Application to a medium-upper segment passenger car. Applied Thermal Engineering, 31(16), 3559-3568. doi:10.1016/j.applthermaleng.2011.07.017Payri, F., López, J. J., Martín, J., & Carreño, R. (2018). Improvement and application of a methodology to perform the Global Energy Balance in internal combustion engines. Part 1: Global Energy Balance tool development and calibration. Energy, 152, 666-681. doi:10.1016/j.energy.2018.03.118Arrègle, J., López, J. J., Garcı́a, J. M., & Fenollosa, C. (2003). Development of a zero-dimensional Diesel combustion model. Applied Thermal Engineering, 23(11), 1319-1331. doi:10.1016/s1359-4311(03)00080-2Arrègle, J., López, J. J., Garcı́a, J. M., & Fenollosa, C. (2003). Development of a zero-dimensional Diesel combustion model. Part 1: Analysis of the quasi-steady diffusion combustion phase. Applied Thermal Engineering, 23(11), 1301-1317. doi:10.1016/s1359-4311(03)00079-6Benajes, J., Olmeda, P., Martín, J., & Carreño, R. (2014). A new methodology for uncertainties characterization in combustion diagnosis and thermodynamic modelling. Applied Thermal Engineering, 71(1), 389-399. doi:10.1016/j.applthermaleng.2014.07.010Payri, F., Olmeda, P., Martín, J., & Carreño, R. (2015). Experimental analysis of the global energy balance in a DI diesel engine. Applied Thermal Engineering, 89, 545-557. doi:10.1016/j.applthermaleng.2015.06.005Olmeda, P., Dolz, V., Arnau, F. J., & Reyes-Belmonte, M. A. (2013). Determination of heat flows inside turbochargers by means of a one dimensional lumped model. Mathematical and Computer Modelling, 57(7-8), 1847-1852. doi:10.1016/j.mcm.2011.11.078Torregrosa, A., Olmeda, P., Degraeuwe, B., & Reyes, M. (2006). A concise wall temperature model for DI Diesel engines. Applied Thermal Engineering, 26(11-12), 1320-1327. doi:10.1016/j.applthermaleng.2005.10.021Payri, R., Salvador, F. J., Gimeno, J., & Bracho, G. (2008). A NEW METHODOLOGY FOR CORRECTING THE SIGNAL CUMULATIVE PHENOMENON ON INJECTION RATE MEASUREMENTS. Experimental Techniques, 32(1), 46-49. doi:10.1111/j.1747-1567.2007.00188.xTormos, B., Martín, J., Carreño, R., & Ramírez, L. (2018). A general model to evaluate mechanical losses and auxiliary energy consumption in reciprocating internal combustion engines. Tribology International, 123, 161-179. doi:10.1016/j.triboint.2018.03.00

Analysis of temperature and altitude effects on the Global Energy Balance during WLTC

This is the author¿s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/14680874211034292[EN] In this work, the Global Energy Balance (GEB) of a 1.6 L compression ignition engine is analyzed during WLTC using a combination of experimental measurements and simulations, by means of a Virtual Engine. The energy split considers all the relevant energy terms at two starting temperatures (20 degrees C and 7 degrees C) and two altitudes (0 and 1000 m). It is shown that reducing ambient temperature from 20 degrees C to -7 degrees C decreases brake efficiency by 1% and increases fuel consumption by 4%, mainly because of the higher friction due to the higher oil viscosity, while the effect of increasing altitude 1000 m decreases brake efficiency by 0.8% and increases fuel consumption by 2.5% in the WLTC mainly due to the change in pumping. In addition, GEB shows that ambient temperature is affecting exhaust enthalpy by 4.5%, heat rejection to coolant by 2%, and heat accumulated in the block by 2.5%, while altitude does not show any remarkable variations other than pumping and break power.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research has been partially funded by the European Union's Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 ("DiePeR'') and by the Spanish government under the grant agreement TRA2017-89894-R ("MECOEM'') and Sushma Artham was supported by FPI grant with reference PRE2018-084411. The authors wish to thank Renault SAS, especially P. Mallet and E. Gaiffas, for supporting this research.Payri, F.; Martín, J.; Arnau Martínez, FJ.; Artham, S. (2022). Analysis of temperature and altitude effects on the Global Energy Balance during WLTC. International Journal of Engine Research. 23(11):1831-1849. https://doi.org/10.1177/1468087421103429218311849231

Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine

[EN] Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to simulate several VVT strategies and develop a control system to actuate over the valves timing in order to increase diesel oxidation catalyst efficiency and reduce the exhaust pollutant emissions. A transient operating conditions comparison, taking the Worldwide Harmonized Light-Duty Vehicles Test Cycle (WLTC) as a reference, has been done by analyzing fuel economy, HC and CO pollutant emissions levels. The results conclude that the combination of an early exhaust and a late intake valve events leads to a 20% reduction in CO emissions with a fuel penalty of 6% over the low speed stage of the WLTC, during the warm-up of the oxidation catalyst. The same set-up is able to reduce HC emissions down to 16% and NO(x)emission by 13%.This research has been partially funded by the Spanish government under the grant agreement TRA2017-89894-R ("Mecoem"). Angel Aunon was supported through the "Apoyo para la investigacion y Desarrollo (PAID)" grant for doctoral studies (FPI S2 2018 1048) by Universitat Politecnica de Valencia.Serrano, J.; Arnau Martínez, FJ.; Martín, J.; Auñón-García, Á. (2020). Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine. Energies. 13(17):1-26. https://doi.org/10.3390/en13174561S1261317Arnau, F. J., Martín, J., Pla, B., & Auñón, Á. (2020). Diesel engine optimization and exhaust thermal management by means of variable valve train strategies. International Journal of Engine Research, 22(4), 1196-1213. doi:10.1177/1468087419894804Luján, J. M., Serrano, J. R., Piqueras, P., & García-Afonso, Ó. (2015). Experimental assessment of a pre-turbo aftertreatment configuration in a single stage turbocharged diesel engine. Part 2: Transient operation. Energy, 80, 614-627. doi:10.1016/j.energy.2014.12.017Lancefield, T., Methley, I., Räse, U., & Kuhn, T. (2000). The Application of Variable Event Valve Timing to a Modern Diesel Engine. SAE Technical Paper Series. doi:10.4271/2000-01-1229Gonzalez D, M. A., & Di Nunno, D. (2016). Internal Exhaust Gas Recirculation for Efficiency and Emissions in a 4-Cylinder Diesel Engine. SAE Technical Paper Series. doi:10.4271/2016-01-2184Serrano, J. R., Piqueras, P., Navarro, R., Gómez, J., Michel, M., & Thomas, B. (2016). Modelling Analysis of Aftertreatment Inlet Temperature Dependence on Exhaust Valve and Ports Design Parameters. SAE Technical Paper Series. doi:10.4271/2016-01-0670Siewert, R. M. (1971). How Individual Valve Timing Events Affect Exhaust Emissions. SAE Technical Paper Series. doi:10.4271/710609Tomoda, T., Ogawa, T., Ohki, H., Kogo, T., Nakatani, K., & Hashimoto, E. (2010). Improvement of Diesel Engine Performance by Variable Valve Train System. International Journal of Engine Research, 11(5), 331-344. doi:10.1243/14680874jer586Benajes, J., Reyes, E., & Luján, J. M. (1996). Modelling Study of the Scavenging Process in a Turbocharged Diesel Engine with Modified Valve Operation. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 210(4), 383-393. doi:10.1243/pime_proc_1996_210_210_02Deppenkemper, K., Özyalcin, C., Ehrly, M., Schoenen, M., Bergmann, D., & Pischinger, S. (2018). 1D Engine Simulation Approach for Optimizing Engine and Exhaust Aftertreatment Thermal Management for Passenger Car Diesel Engines by Means of Variable Valve Train (VVT) Applications. SAE Technical Paper Series. doi:10.4271/2018-01-0163Zammit, J. P., McGhee, M. J., Shayler, P. J., Law, T., & Pegg, I. (2015). The effects of early inlet valve closing and cylinder disablement on fuel economy and emissions of a direct injection diesel engine. Energy, 79, 100-110. doi:10.1016/j.energy.2014.10.065Pan, X., Zhao, Y., Lou, D., & Fang, L. (2020). Study of the Miller Cycle on a Turbocharged DI Gasoline Engine Regarding Fuel Economy Improvement at Part Load. Energies, 13(6), 1500. doi:10.3390/en13061500Guan, W., Pedrozo, V. B., Zhao, H., Ban, Z., & Lin, T. (2019). Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine. International Journal of Engine Research, 21(4), 578-591. doi:10.1177/1468087419846031Guan, W., Zhao, H., Ban, Z., & Lin, T. (2018). Exploring alternative combustion control strategies for low-load exhaust gas temperature management of a heavy-duty diesel engine. International Journal of Engine Research, 20(4), 381-392. doi:10.1177/1468087418755586Maniatis, P., Wagner, U., & Koch, T. (2018). A model-based and experimental approach for the determination of suitable variable valve timings for cold start in partial load operation of a passenger car single-cylinder diesel engine. International Journal of Engine Research, 20(1), 141-154. doi:10.1177/1468087418817119Kim, J., & Bae, C. (2015). An investigation on the effects of late intake valve closing and exhaust gas recirculation in a single-cylinder research diesel engine in the low-load condition. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 230(6), 771-787. doi:10.1177/0954407015595149Zhou, X., Liu, E., Sun, D., & Su, W. (2018). Study on transient emission spikes reduction of a heavy-duty diesel engine equipped with a variable intake valve closing timing mechanism and a two-stage turbocharger. International Journal of Engine Research, 20(3), 277-291. doi:10.1177/1468087417748837Gosala, D. B., Ramesh, A. K., Allen, C. M., Joshi, M. C., Taylor, A. H., Van Voorhis, M., … Stretch, D. (2017). Diesel engine aftertreatment warm-up through early exhaust valve opening and internal exhaust gas recirculation during idle operation. International Journal of Engine Research, 19(7), 758-773. doi:10.1177/1468087417730240Parvate-Patil, G. B., Hong, H., & Gordon, B. (2004). Analysis of Variable Valve Timing Events and Their Effects on Single Cylinder Diesel Engine. SAE Technical Paper Series. doi:10.4271/2004-01-2965Piano, A., Millo, F., Di Nunno, D., & Gallone, A. (2017). Numerical Analysis on the Potential of Different Variable Valve Actuation Strategies on a Light Duty Diesel Engine for Improving Exhaust System Warm Up. SAE Technical Paper Series. doi:10.4271/2017-24-0024Payri, F., Arnau, F. J., Piqueras, P., & Ruiz, M. J. (2018). Lumped Approach for Flow-Through and Wall-Flow Monolithic Reactors Modelling for Real-Time Automotive Applications. SAE Technical Paper Series. doi:10.4271/2018-01-0954Martin, J., Arnau, F., Piqueras, P., & Auñon, A. (2018). Development of an Integrated Virtual Engine Model to Simulate New Standard Testing Cycles. SAE Technical Paper Series. doi:10.4271/2018-01-1413Serrano, J. R., Arnau, F. J., García-Cuevas, L. M., Dombrovsky, A., & Tartoussi, H. (2016). Development and validation of a radial turbine efficiency and mass flow model at design and off-design conditions. Energy Conversion and Management, 128, 281-293. doi:10.1016/j.enconman.2016.09.032Galindo, J., Tiseira, A., Navarro, R., Tarí, D., Tartoussi, H., & Guilain, S. (2016). Compressor Efficiency Extrapolation for 0D-1D Engine Simulations. SAE Technical Paper Series. doi:10.4271/2016-01-0554Serrano, J. R., Olmeda, P., Arnau, F. J., & Samala, V. (2019). A holistic methodology to correct heat transfer and bearing friction losses from hot turbocharger maps in order to obtain adiabatic efficiency of the turbomachinery. International Journal of Engine Research, 21(8), 1314-1335. doi:10.1177/1468087419834194Serrano, J. R., Olmeda, P., Arnau, F. J., Dombrovsky, A., & Smith, L. (2014). Analysis and Methodology to Characterize Heat Transfer Phenomena in Automotive Turbochargers. Journal of Engineering for Gas Turbines and Power, 137(2). doi:10.1115/1.4028261Serrano, J. R., Olmeda, P., Arnau, F. J., Dombrovsky, A., & Smith, L. (2015). Turbocharger heat transfer and mechanical losses influence in predicting engines performance by using one-dimensional simulation codes. Energy, 86, 204-218. doi:10.1016/j.energy.2015.03.130Arrègle, J., López, J. J., Martín, J., & Mocholí, E. M. (2006). Development of a Mixing and Combustion Zero-Dimensional Model for Diesel Engines. SAE Technical Paper Series. doi:10.4271/2006-01-1382Payri, F., Arrègle, J., López, J. J., & Mocholí, E. (2008). Diesel NOx Modeling with a Reduction Mechanism for the Initial NOx Coming from EGR or Re-entrained Burned Gases. SAE Technical Paper Series. doi:10.4271/2008-01-1188Broatch, A., Olmeda, P., Martin, J., & Salvador-Iborra, J. (2018). Development and Validation of a Submodel for Thermal Exchanges in the Hydraulic Circuits of a Global Engine Model. SAE Technical Paper Series. doi:10.4271/2018-01-0160Guardiola, C., Pla, B., Bares, P., & Mora, J. (2018). An on-board method to estimate the light-off temperature of diesel oxidation catalysts. International Journal of Engine Research, 21(8), 1480-1492. doi:10.1177/1468087418817965Russell, A., & Epling, W. S. (2011). Diesel Oxidation Catalysts. Catalysis Reviews, 53(4), 337-423. doi:10.1080/01614940.2011.596429Guardiola, C., Pla, B., Piqueras, P., Mora, J., & Lefebvre, D. (2017). Model-based passive and active diagnostics strategies for diesel oxidation catalysts. Applied Thermal Engineering, 110, 962-971. doi:10.1016/j.applthermaleng.2016.08.207Abdelghaffar, W. A., Osman, M. M., Saeed, M. N., & Abdelfatteh, A. I. (2002). Effects of Coolant Temperature on the Performance and Emissions of a Diesel Engine. Design, Operation, and Application of Modern Internal Combustion Engines and Associated Systems. doi:10.1115/ices2002-464Torregrosa, A. J., Olmeda, P., Martín, J., & Degraeuwe, B. (2006). Experiments on the influence of inlet charge and coolant temperature on performance and emissions of a DI Diesel engine. Experimental Thermal and Fluid Science, 30(7), 633-641. doi:10.1016/j.expthermflusci.2006.01.00

How are pine species responding to soil drought and climate change in the Iberian Peninsula?

This study investigates the relationship between soil moisture and the growth of Pinus halepensis, P. nigra, P. sylvestris and P. uncinata, which are some of the main pine species of the Iberian Peninsula, and the response of these species to soil drought. The role played by climatic and geographic factors in the resilience of these species to drought events is also evaluated. A total of 110 locations of the four species studied were selected, with data ranging from 1950 to 2007. The results show that the species that are less dependent on soil moisture best withstood droughts, while those more dependent on it showed better adaptability. Additionally, climatic and geographic factors had a stronger influence on the species’ resilience to soil drought at higher altitudes. The results of this study can help us to better understand forest ecosystem dynamics and their reaction to droughts in Mediterranean areas, where this phenomenon will be much more severe in the future due to climate change

Diesel engine optimization and exhaust thermal management by means of variable valve train strategies

[EN] Due to the need to achieve a fast warm-up of the after-treatment system in order to fulfill the pollutant emission regulations, a growing interest has arisen to adopt variable valve timing technology for automotive engines. Several variable valve timing strategies can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to carry out a simulation study comparing several exhaust variable valve actuation strategies. A steady-state analysis has been done in order to evaluate the potential of the different strategies at different operating points. Finally, the effect on the after-treatment warm-up, fuel economy and pollutant emission levels was evaluated over the worldwide harmonized light vehicles test cycle. As a conclusion, the combination of an advanced exhaust (early exhaust valve opening and early exhaust valve closing) and a delayed intake (late intake valve opening and late intake valve closing) presented the best trade-off between exhaust temperature increment and fuel consumption, which achieved a mean temperature increment during low-speed phase of the worldwide harmonized light vehicles test cycle of 27¿°C with a fuel penalty of 6%. The exhaust valve re-opening technique offers a worse trade-off. However, the exhaust valve re-opening leads to lower nitrogen oxide (29% less) and carbon monoxide (11% less) pollutant emissions.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research has been partially funded by the European Union's Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 ("DiePeR") and by the Spanish government under the grant agreement TRA2017-89894-R. The authors want to acknowledge the "Apoyo para la investigacion y Desarrollo (PAID)," grant for doctoral studies (FPI S2 2018 1048), of Universitat Politecnica de Valencia.Arnau Martínez, FJ.; Martín, J.; Pla Moreno, B.; Auñón-García, Á. (2021). Diesel engine optimization and exhaust thermal management by means of variable valve train strategies. International Journal of Engine Research. 22(4):1196-1213. https://doi.org/10.1177/1468087419894804S1196121322

Development of an Integrated Virtual Engine Model to Simulate New Standard Testing Cycles

[EN] The combination of more strict regulation for pollutant and CO2 emissions and the new testing cycles, covering a wider range of transient conditions, makes very interesting the development of predictive tools for engine design and pre-calibration. This paper describes a new integrated Virtual Engine Model (VEMOD) that has been developed as a standalone tool to simulate new standard testing cycles. The VEMOD is based on a wave-action model that carries out the thermo-and fluid dynamics calculation of the gas in each part of the engine. In the model, the engine is represented by means of 1D ducts, while the volumes, such as cylinders and reservoirs, are considered as 0D elements. Different sub-models are included in the VEMOD to take into account all the relevant phenomena. Thus, the combustion process is calculated by the Apparent Combustion Time (ACT) 1D model, responsible for the prediction of the rate of heat release and NOx formation. Experimental correlations are used to determine the rest of pollutants. In order to predict tailpipe pollutant emissions to the ambient, different sub-models have been developed to reproduce the behavior of the aftertreatment devices (DOC and DPF) placed in the exhaust system. Dedicated friction and auxiliaries sub-models allow obtaining the brake power. The turbocharger consists of 0D compressor and turbine sub-models capable of extrapolating the available maps of both devices. The VEMOD includes coolant and lubricant circuits linked, on the one hand, with the engine block and the turbocharger through heat transfer lumped models; and on the other hand with the engine heat exchangers. A control system emulating the ECU along with vehicle and driver sub-models allow completing the engine simulation. The Virtual Engine Model has been validated with experimental tests in a 1.6 L Diesel engine using steady and transient tests in both hot and cold conditions. Engine torque was predicted with a mean error of 3 Nm and an error below 14 Nm for 90 % of the cycle duration. CO2 presented a mean error of 0.04 g/s, while during 80 % of the cycle, error was below 0.44 g/s.This research has been partially funded by the European Union’s Horizon 2020 Framework Programme for research, technological development and demonstration under grant agreement 723976 (“DiePeR”) and by the Spanish government under the grant agreement TRA2017-89894-R. The authors wish to thank Renault SAS, especially P. Mallet and E. Gaïffas, for supporting this research.Martín Díaz, J.; Arnau Martínez, FJ.; Piqueras, P.; Auñón-García, Á. (2018). Development of an Integrated Virtual Engine Model to Simulate New Standard Testing Cycles. SAE Technical Papers. https://doi.org/10.4271/2018-01-1413

A dislocation dynamics study of the strength of stacking fault tetrahedra. Part I: interactions with screw dislocations

We present a comprehensive dislocation dynamics (DD) study of the strength of stacking fault tetrahedra (SFT) to screw dislocation glide in fcc Cu. Our methodology explicitly accounts for partial dislocation reactions in fcc crystals, which allows us to provide more detailed insights into the dislocation– SFT processes than previous DD studies. The resistance due to stacking fault surfaces to dislocation cutting has been computed using atomistic simulations and added in the form of a point stress to our DD methodology. We obtain a value of 1658.9 MPa, which translates into an extra force resolved on the glide plane that dislocations must overcome before they can penetrate SFTs. In fact, we see they do not, leading to two well differentiated regimes: (i) partial dislocation reactions, resulting in partial SFT damage, and (ii) impenetrable SFT resulting in the creation of Orowan loops. We obtain SFT strength maps as a function of dislocation glide plane-SFT intersection height, interaction orientation, and dislocation line length. In general SFTs are weaker obstacles the smaller the encountered triangular area is, which has allowed us to derive simple scaling laws with the slipped area as the only variable. These laws suffice to explain all strength curves and are used to derive a simple model of dislocation–SFT strength. The stresses required to break through obstacles in the 2.5–4.8-nm size range have been computed to be 100–300 MPa, in good agreement with some experimental estimations and molecular dynamics calculations

Atomistically informed dislocation dynamics in fcc crystals

We develop a nodal dislocation dynamics (DD) model to simulate plastic processes in fcc crystals. The model explicitly accounts for all slip systems and Burgers vectors observed in fcc systems, including stacking faults and partial dislocations. We derive simple conservation rules that describe all partial dislocation interactions rigorously and allow us to model and quantify cross-slip processes, the structure and strength of dislocation junctions, and the formation of fcc-specific structures such as stacking fault tetrahedra. The DD framework is built upon isotropic non-singular linear elasticity and supports itself on information transmitted from the atomistic scale. In this fashion, connection between the meso and micro scales is attained self-consistently, with all material parameters fitted to atomistic data. We perform a series of targeted simulations to demonstrate the capabilities of the model, including dislocation reactions and dissociations and dislocation junction strength. Additionally we map the four-dimensional stress space relevant for cross-slip and relate our findings to the plastic behavior of monocrystalline fcc metal

Scientific design of skylights

This paper intends to present a critical reality in contemporary design, the astonishing coexistence of buildings in which daylighting has been carefully considered and simulated, and others in which this issue is treated with haphazard design gestures. Although initial simulation models in the daylighting field were very much distanced from the actual practicing architect, this is no longer the case in our opinion, and also, it is a fact, that the role of apertures in all the relevant thermal exchanges that occur in buildings has been thoroughly recognized. However, many types of designs or even bioclimatic designs do not consider lighting simulations from the beginning of the design-process, and they are presented as correct if only the thermal balance meets, even at the risk of later energy waste in lighting devices and visual or physical discomfort

Prevalence of urinary incontinence among spanish older people living at home

Objective: To estimate the prevalence and characteristics of urinary incontinence (UI) in the noninstitutionalized elderly population of Madrid. Spain. Methods: We carried out a cross-sectional study in a representative sample of all community-dwelling people aged 65 or over. Subjects were interviewed in their homes. The question: Do you currently experience any difficulty in controlling your urine?... In other words, does your urine escape involuntarily? Was used to identify UI. Type of UI, use of absorbents and specific drugs were also assessed, as well as consultation behaviour. Results: 589 persons were interviewed (response rate: 71,2 %). The prevalence of UI was 15,5%. No significant difference was observed between men and women. Urge UI was the main type for men and mixed UI for women. Use of pads was referred by 20,2% of men. A total of 34,4% of subjects never went to the doctor for their problem (25,2% of men and 39,4% of women). Conclusion: Compared to other populations the overall prevalence of UI in Spanish elders living at home is relatively high. A very small difference by gender was found, although a lower response rate in women could in part explain this unexpected finding.Publicad