A zonal approach for estimating pressure ratio at compressor extreme off-design conditions

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/10.1177/1468087418754899[EN] Zero-dimensional/one-dimensional computational fluid dynamics codes are used to simulate the performance of complete internal combustion engines. In such codes, the operation of a turbocharger compressor is usually addressed employing its performance map. However, simulation of engine transients may drive the compressor to work at operating conditions outside the region provided by the manufacturer map. Therefore, a method is required to extrapolate the performance map to extended off-design conditions. This work examines several extrapolating methods at the different off-design regions, namely, low-pressure ratio zone, low-speed zone and high-speed zone. The accuracy of the methods is assessed with the aid of compressor extreme off-design measurements. In this way, the best method is selected for each region and the manufacturer map is used in design conditions, resulting in a zonal extrapolating approach aiming to preserve accuracy. The transitions between extrapolated zones are corrected, avoiding discontinuities and instabilities.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Daniel Tari is partially supported through contract FPI-S2-2015-1095 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.Galindo, J.; Navarro, R.; García-Cuevas González, LM.; Tarí, D.; Tartoussi, H.; Guilain, S. (2019). 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Flow phenomena leading to surge in a centrifugal compressor. Energy, 103, 572-587. doi:10.1016/j.energy.2016.03.032Hung, K.-S., Chung, J.-C., Liu, C.-C., & Huang, J.-M. (2017). A study of off-design performance improvement for a centrifugal refrigerant compressor. Advances in Mechanical Engineering, 9(3), 168781401769622. doi:10.1177/1687814017696224Leufvén, O., & Eriksson, L. (2014). Measurement, analysis and modeling of centrifugal compressor flow for low pressure ratios. International Journal of Engine Research, 17(2), 153-168. doi:10.1177/1468087414562456Serrano, J. R., Tiseira, A., García-Cuevas, L. M., Inhestern, L. B., & Tartoussi, H. (2017). Radial turbine performance measurement under extreme off-design conditions. Energy, 125, 72-84. doi:10.1016/j.energy.2017.02.118Serrano, J. R., Olmeda, P., Tiseira, A., García-Cuevas, L. M., & Lefebvre, A. (2013). Theoretical and experimental study of mechanical losses in automotive turbochargers. 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A study on the internal convection in small turbochargers. Proposal of heat transfer convective coefficients

Nowadays turbochargers play an important role in improving internal combustion engines (ICE) performance. Usually, engine manufacturers use computer codes to predict the behaviour of both engine and turbocharger, the later by means of measured look-up maps. Using look-up maps different problems arise, being one of the most important the difference in heat transfer between the current operating condition and the conditions at which maps were measured. These effects are very important at low to medium turbocharger speeds (typical condition of urban driving conditions) where heat transfer can even be higher than mechanical power. In this work, the different convective heat transfer phenomena inside these kind of machines have been measured and analysed. Besides, general correlations for these flows, based on dimensionless numbers, are fitted and validated in three different turbochargers. The applicability of the model is shown by comparison the main results obtained when the model is used and not, improving up to 20 C the predicted turbine outlet temperature. The main advantages of applying these correlations rely on predicting fluids outlet temperatures (compressor, turbine, oil and coolant). The former is needed to feed accurately ICE model, turbine outlet temperature is important for aftertreatment device modelling while oil and coolant temperatures are important in order to design optimum cooling systems.This work has been partially supported by the Spanish Ministerio de Economa 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 Ministry of Science and Innovation of Spain.Serrano Cruz, JR.; Olmeda González, PC.; Arnau Martínez, FJ.; Reyes Belmonte, MÁ.; Tartoussi, H. (2015). A study on the internal convection in small turbochargers. Proposal of heat transfer convective coefficients. Applied Thermal Engineering. 89:587-599. https://doi.org/10.1016/j.applthermaleng.2015.06.053S5875998