• Energy Research

One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80°C and 90°C), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.

The use of subcooled flow boiling is a convenient option for the thermal management of downsized engines, but proper control of the phenomenon requires the accurate prediction of heat transfer at the coolant side, for which the use of computational fluid dynamics is a suitable alternative. While in most of the applications to engine cooling a single-fluid equivalent method is used, in this paper the performance of a two-fluid method is evaluated in engine-like conditions with special interest in the low-velocity range. The results indicate that the description of the process at low velocities provided by the two-fluid method is better than that given by a single-fluid model, while model calibration is simpler and more robust and the computational cost is substantially reduced.

Diesel engines are the most commonly used internal combustion engines nowadays, especially in European transportation. This preference is due to their low consumption and acceptable driveability and comfort. However, the main disadvantages of traditional direct injection Diesel engines are their high levels of noise, nitrogen oxides (NO x) and soot emissions, and the usage of fossil fuels. In order to tackle the problem of high emission levels, new combustion concepts have been recently developed. A good example is the premixed charge compression ignition (PCCI) combustion, a strategy in which early injections are used, causing a burning process in which more fuel is burned in premixed conditions, which affects combustion noise. The use of a pilot injection has become an effective tool for reducing combustion noise. The main objective of this paper is to analyze experimentally the pollutant emissions, combustion noise, and performance of a Diesel engine operating under PCCI combustion with the use of a pilot injection. In addition, a novel methodology, based on the decomposition of the in-cylinder pressure signal, was used for combustion noise analysis. The results show that while the PCCI combustion has potential to reduce significantly the NO x and soot emission levels, compared to conventional Diesel combustion strategy, combustion noise continues to be a critical issue for the implementation of this new combustion concept in passenger cars. This work has been partially supported by Ministerio de Educacin y Ciencia through Grant No. TRA2006-13782. L.F. Monico holds the Grant 2009/003 from Santiago Grisolia Program of Generalitat Valenciana.

[EN] Research efforts in the automotive sector focus on developing new combustion concepts for mitigating the emissions of nitrous oxides and soot of conventional Diesel combustion. One of the most promising concept is the Premixed Charge Compression Ignition. In this, the fuel burns in premixed conditions, avoiding the formation of soot whereas nitrous oxides are controlled using large amounts of exhaust gas recirculation. Because of the premixed combustion, high fuel-burning velocities are produced, whence combustion noise is deteriorated. In order to mitigate this drawback, different blends of gasoline and Diesel fuels are being considered due to their suitability for this combustion characteristics. The effect of these fuel blends on emissions, performance and engine noise is analysed in this paper with the aim to provide additional knowledge of the fundamental issues of this particular combustion mode. The study also includes sweeps of both the start of injection and the amount of exhaust gas recirculation, in order to evaluate further degrees of freedom in the optimisation of the engine settings. Results show that the consideration of the engine noise together with both performance and emissions, reduces dramatically the margin of variation of the combustion settings, limiting therefore the operation range of the engine. (C) 2017 Elsevier Ltd. All rights reserved. The equipment used in this work has been partially supported by the Spanish Ministerio de Economía y Competitividad through grant no DPI2015-70464-R and by FEDER project funds Dotación de infraestructuras científico técnicas para el Centro Integral de Mejora Energética y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06) framed in the operational program of unique scientific and technical infrastructure of the Spanish Ministerio de Economía y Competitividad. J. Gomez-Soriano is partially supported through contract FPI-S2-2016-1353 of the Programa de Apoyo para la Investigación y Desarrollo (PAID-01-16) of Universitat Politècnica de València.

The main goal of this work is to validate an innovative experimental facility and to establish a methodology to evaluate the influence of some of the engine parameters on local engine heat transfer behaviour under motored steady-state conditions. Instantaneous temperature measurements have been performed in order to estimate heat fluxes on a modified Diesel single cylinder combustion chamber. This study was divided into two main parts. The first one was the design and setting on of an experimental bench to reproduce Diesel conditions and perform local-instantaneous temperature measurements along the walls of the combustion chamber by means of fast response thermocouples. The second one was the development of a procedure for temperature signal treatment and local heat flux calculation based on one-dimensional Fourier analysis. A thermodynamic diagnosis model has been employed to characterise the modified engine with the new designed chamber. As a result of the measured data coherent findings have been obtained in order to understand local behaviour of heat transfer in an internal combustion engine, and the influence of engine parameters on local instantaneous temperature and heat flux, have been analysed. © 2011 Elsevier Ltd. All rights reserved.

[EN] Decarbonization requirements have extended the use of wind turbines by orders of magnitude. Due to their high stiffness-to-weight ratio, composite materials have been widely used for manufacturing the turbine blades in the recent years. As a consequence of the orthotropic mechanical properties of these materials, the structural behavior of the blade is conditioned by the orientation of the fibers. This article gives a general idea of the benefits of optimizing the composite material ply angle. Along the paper, two different structures are analyzed, a quasi-isotropic material and a structure with oblique fibers. The analysis is conducted using a reduced order model solver which couples a beam element structural solver with the blade element momentum and Theodorsen pitching airfoil theories. The solvers are validated, and then, the flutter conditions are obtained and used to limit the whole operation curve for both blades. The oblique layup structure is evidenced to increase the critical wind velocity by 10% for a defined control law and electrical system. Therefore, the importance of a correct structural analysis is demonstrated to be crucial in the design and manufacturing of the following generation of wind turbine blades. This project have been partially funded by Spanish Ministry of Uni-versity through the University Faculty Training (FPU) program with reference FPU19/02201.

[EN] An experimental measurement campaign is presented where particle image velocimetry (PIV) was used in an effort to characterize the velocity field in a turbocharger compressor when unstable operating conditions lead to flow reversing from the diffuser into the inlet pipe. Previous studies have successfully used this and similar techniques, but the most relevant results have been obtained in an open compressor where the backflow can diffuse into the ambient. In this work a glass pipe long enough to confine the full extent of the backflow has been used. Advantage was taken from the fact that this backflow is at higher temperature due to the compression process, enabling a preliminary work where a thermocouple array was used to estimate its maximum length across the compressor map. Using these results as a reference both axial and transversal velocity fields were measured. Issues associated with each one are described, along with relevant results that show how the technique correctly identifies the reversed flow, a conclusion that is supported by the comparison of the velocity average and standard deviation profiles with those of measured temperature. This work has been partially supported by Jaguar Land Rover Limited, Abbey Road, Whitley, Coventry CV3 4LF, UK. The equipment used in this work has been partially supported by the Spanish Ministerio de Economia y Competitividad through grant no DPI2015-70464-R and by FEDER - EU project funds "Dotaciem de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)" framed in the operational program of unique scientific and technical infrastructure of the Spanish Ministerio de Economia y Competitividad. J. Garcia-Tiscar was partially supported through contract FPI-S22015-1530 of the Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.