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:10.1177/146808741244908592104141Soranna, 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