Compact High-Pressure Intake Silencer with Multilayer Porous Material

Intake noise has become one the main concerns in the design of highly-supercharged downsized engines, which are expected to play a significant role in the upcoming years. Apart from the low frequencies associated with engine breathing, in these engines other frequency bands are also relevant which are related to the turbocharger operation, and which may radiate from the high-pressure side from the compressor outlet to the charge air cooler. Medium frequencies may be controlled with the use of different typologies of resonators, but these are not so effective for relatively high frequencies. In this paper, the potential of the use of multi-layer porous materials to control those high frequencies is explored. The material sheets are located in the side chamber of an otherwise conventional resonator, thus providing a compact, lightweight and convenient arrangement. Several configurations have been tested in an impulse rig, without and with a superimposed mean flow, and the results have been analyzed with the help of a simple linear finite volume model accounting for the material. Then, the model has been used to explore different combinations of geometry and material properties, with the purpose of defining design guidelines for a proper choice of the device size and the material used, that may allow fulfilling the targeted value.Torregrosa, AJ.; Broatch Jacobi, JA.; Raimbault, V.; Migaud, J. (2016). Compact High-Pressure Intake Silencer with Multilayer Porous Material. SAE International Journal of Passenger Cars. Mechanical Systems. 9(3):1-8. doi:10.4271/2016-01-1819S189

Experimental methodology for turbocompressor in-duct noise evaluation based on beamforming wave decomposition

An experimental methodology is proposed to assess the noise emission of centrifugal turbocompressors like those of automotive turbochargers. A step-by-step procedure is detailed, starting from the theoretical considerations of sound measurement in flow ducts and examining specific experimental setup guidelines and signal processing routines. Special care is taken regarding some limiting factors that adversely affect the measuring of sound intensity in ducts, namely calibration, sensor placement and frequency ranges and restrictions. In order to provide illustrative examples of the proposed techniques and results, the methodology has been applied to the acoustic evaluation of a small automotive turbocharger in a flow bench. Samples of raw pressure spectra, decomposed pressure waves, calibration results, accurate surge characterization and final compressor noise maps and estimated spectrograms are provided. The analysis of selected frequency bands successfully shows how different, known noise phenomena of particular interest such as mid-frequency "whoosh noise" and low-frequency surge onset are correlated with operating conditions of the turbocharger. Comparison against external inlet orifice intensity measurements shows good correlation and improvement with respect to alternative wave decomposition techniques.The equipment used in this work has been partially supported by the Spanish Ministerio de Economia y Competitividad through grant no. TRA2012-36954 and by FEDER project funds "Dotacion 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 is partially supported through contract FPI-S2-2015-1530 of the Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.Torregrosa, AJ.; Broatch Jacobi, JA.; Margot, X.; García Tíscar, J. (2016). Experimental methodology for turbocompressor in-duct noise evaluation based on beamforming wave decomposition. Journal of Sound and Vibration. 376:60-71. https://doi.org/10.1016/j.jsv.2016.04.035S607137

Combustion noise analysis of partially premixed combustion concept using gasoline fuel in a 2-stroke engine

In the last decade, different advanced combustion concepts based on generating totally or partially premixed conditions have been investigated in CI (compression ignition) engines with the aim of achieving lower NOx (nitrous oxides) and soot emissions. Most of the drawbacks inherent to this type of combustions, such as the combustion phasing control or combustion stability, can be mitigated by combining the PPC (Partially Premixed Combustion) concept fueled by gasoline and a small 2-stroke HSDI (high speed direct ignition) engine. However, combustion noise issue remains unsolved while it is a critical aspect due to its strong influence in the customer purchasing decision and compliance of more stringent regulations. In this work, an analysis of the combustion noise generated by PPC combustion concept is performed in order to identify the most influential parameters and to define key paths for controlling the noise level. In addition, 3D CFD (Computational Fluid Dynamics) simulations have been performed to further understand the combustion noise generation mechanisms. Results evidence how the strong impact of the maximum pressure time-derivative achieved during combustion process renders all other sources of noise generation irrelevant. The trade-off between combustion noise and combustion efficiency of this PPC concept has been confirmed, while the intrinsic relation between such parameters and the engine efficiency has been also evaluated.The authors kindly recognize the technical support provided by Mr. Pascal Tribotte from RENAULT SAS in the frame of the DREAM-DELTA-68530-13-3205 Project.Broatch Jacobi, JA.; Margot, X.; Novella Rosa, R.; Gómez-Soriano, J. (2016). Combustion noise analysis of partially premixed combustion concept using gasoline fuel in a 2-stroke engine. Energy. 107:612-624. https://doi.org/10.1016/j.energy.2016.04.045S61262410

Acoustic characterization of automotive turbocompressors

The performance of different experimental techniques proposed in the literature for acoustic characterization was assessed through the study of the noise generated by the compressor of an automotive turbocharger under different working conditions in an engine test cell. The most critical restrictions of in-duct intensimetry methods regarding frequency limitations are presented and experimentally demonstrated. The results provided by those methods were correlated against a reference intensity probe. A beamforming method based on three-sensor-phased arrays appears to be the most reliable approach in the plane wave range, presenting higher accuracy than the more common two-microphone method and simple pressure level measurements. Also, preliminary results from a novel radiated noise quantification technique based on acoustic particle velocity are presented and discussed. The results indicate that further research on this topic is required.This work has been partially supported by the Spanish Ministerio de Economia y Competitividad through grant no. TRA2012-36954. The equipment used in this work has been partially supported by FEDER project funds "Dotacion 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.Torregrosa, AJ.; Broatch Jacobi, JA.; Navarro García, R.; García Tíscar, J. (2015). Acoustic characterization of automotive turbocompressors. International Journal of Engine Research. 16(1):31-37. https://doi.org/10.1177/1468087414562866S313716

Sensitivity of combustion noise and NOx and soot emissions to pilot injection in PCCI Diesel engines

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.Torregrosa, AJ.; Broatch Jacobi, JA.; García Martínez, A.; Mónico Muñoz, LF. (2013). Sensitivity of combustion noise and NOx and soot emissions to pilot injection in PCCI Diesel engines. Applied Energy. 104:149-157. https://doi.org/10.1016/j.apenergy.2012.11.040S14915710

A non-linear quasi-3D model with Flux-Corrected-Transport for engine gas-exchange modelling

Modelling has proven to be an important tool in the design of manifolds and silencers for internal combustion engines. Although simple 1D models are generally sufficiently precise in the case of manifold models, they would usually fail to predict the high frequency behaviour of modern compact manifold designs and, of course, of a complex-shaped silencing system. Complete 3D models are able to account for transversal modes and other non-1D phenomena, but at a high computational cost. A suitable alternative is provided by time-domain non-linear quasi-3D models, whose computational cost is relatively low but still providing an accurate description of the high frequency behaviour of certain elements. In this paper, a quasi-3D model which makes use of a non-linear second order time and space discretization based on finite volumes is presented. As an alternative for avoiding overshoots at discontinuities, a Flux-Corrected Transport technique has been adapted to the quasi-3D method in order to achieve convergence and avoid numerical dispersion. It is shown that the combination of dissipation via damping together with the phoenical form of the anti-diffusion term provides satisfactory resultsTorregrosa, AJ.; Broatch Jacobi, JA.; Arnau Martínez, FJ.; Hernández-Marco, M. (2016). A non-linear quasi-3D model with Flux-Corrected-Transport for engine gas-exchange modelling. Journal of Computational and Applied Mathematics. 291:103-111. doi:10.1016/j.cam.2015.03.034S10311129

Simulations and measurements of automotive turbocharger compressor whoosh noise

Turbocharger noise has become a major concern in downsized automotive engine development. In this paper, the analysis is focused on the whoosh noise produced by the compressor when it is working near surge. A centrifugal compressor has been acoustically characterized on a turbocharger test rig mounted on an anechoic chamber. Three in-duct pressure signals forming a linear array are registered in order to obtain pressure components. In this way, meaningful pressure spectra and sound intensity level (SIL) compressor maps are obtained, showing an increase of SIL in the frequency window corresponding to whoosh noise. Besides, detached eddy simulations (DES) of the centrifugal compressor flow in two operating conditions near surge are performed. Good agreement is found between the experimental measurements and the CFD solutions in terms of predicted pressure spectra. Flow analysis is used to identify patterns responsible for the different features of the pressure spectra. At the simulated conditions, rotating instabilities in the compressor diffuser and inducer cause pressure oscillations in the frequency range of whoosh noise.The equipment used in this work has been partially supported by the Spanish Ministerio de Economia y Competitividad through grant no. TRA2012-36954 and by FEDER project funds "Dotacion 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.Broatch Jacobi, JA.; Galindo, J.; Navarro García, R.; García Tíscar, J.; Daglish, A.; Sharma, RK. (2015). Simulations and measurements of automotive turbocharger compressor whoosh noise. Engineering Applications of Computational Fluid Mechanics. 9(1):12-20. https://doi.org/10.1080/19942060.2015.1004788S12209

Procesos y tecnología de máquinas y motores térmicos

El presente libro está dividido en cinco bloques donde se analizan los procesos y la tecnología de construcción de los principales motores y máquinas térmicas utilizadas en la actualidad. En el primer bloque se realiza una introducción histórica a la evolución de las máquinas y los motores térmicos seguida de una clasificación y análisis de las principales aplicaciones, requerimientos y limitaciones de los mismos. El segundo bloque está dedicado a las máquinas térmicas elementales y en él se hace un estudio de los compresores volumétricos y de las turbomáquinas térmicas, siendo los primeros las máquinas de desplazamiento positivo y las segundas las máquinas dinámicas más características respectivamente. En el tercer bloque se analizan los motores térmicos basados en turbomáquinas (plantas de potencia) pues son las principales productoras de energía eléctrica en la actualidad.En el cuarto bloque se analizan los motores de combustión interna alternativos debido a que son los motores más representativos formados por máquinas térmicas de desplazamiento positivo. Finalmente, en el quinto bloque se estudian las principales emisiones contaminantes de los motores térmicos y se analizan las perspectivas futuras de los mismos.Arregle, JJP.; Galindo Lucas, J.; Pastor Soriano, JV.; Serrano Cruz, JR.; Broatch Jacobi, JA.; Lujan Martinez, JM.; Payri Marín, R.... (2020). Procesos y tecnología de máquinas y motores térmicos. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/153145EDITORIA