ElsevierSerrano Cruz, JR.; Arnau Martínez, FJ.; García-Cuevas González, LM.; Dombrovsky, A.; Tartoussi, H. (2016). Development and validation of a radial turbine efficiency and mass flow model at design and off-design conditions. Energy Abstract Turbine performance at extreme off-design conditions is growing in importance for properly computing turbocharged reciprocating internal combustion engines behaviour during urban driving conditions at current and future homologation cycles. In these cases, the turbine operates at very low flow rates and power outputs and at very high blade to jet speed ratios during transitory periods due to turbocharger wheel inertia and the high pulsation level of engine exhaust flow. This paper presents a physically based method that is able to extrapolate radial turbines reduced mass flow and adiabatic efficiency in blade speed ratio, turbine rotational speed and stator vanes position. The model uses a very narrow range of experimental data from turbine maps to fit the necessary coefficients. By using a special experimental turbocharger gas stand, experimental data have been obtained for extremely low turbine power outputs for the sake of model validation. Even if the data used for fitting only covers the turbine normal operation zone, the extrapolation model provides very good agreement with the experiments at very high blade speed ratio points; producing also good results when extrapolating in rotational speed and stator vanes position. RPerfect gas constant (Jkg −1 K −1 ) r Rotor radius (m) sd Standard deviation (−) 12 provided by manufacturers as a standard practice. Turbine maps are necessary 13 when using 1D or 0D modelling tools to predict the whole engine behaviour. In 14 1D modelling approach the one-dimensional unsteady non-homentropic mass, 15 momentum and energy conservation laws (Euler equations) are solved. Specific 16 source terms are used to simulate the friction and heat exchange in the pipes. 17 The 1D simulation codes make possible the calculation of gas dynamics engine 18 behaviour at low computational costs. Some engine components are modelled 19 4 with a 0D approach, using specific lumped parameter models or performance 20 maps. That is the case of cylinders, injectors, valves, compressors and turbines 21 which are coupled to the 1D computational domain as it is described in [4]. 22 For that reason, turbocharged ICE designers must rely on map extrapolation 23 tools when predicting engine performance outside of turbine design operative 24 conditions [5]. It is typical in pulsating flow conditions, requiring different mod-25 elling approaches similar to the proposed in [6], where meanline one-dimensional 26 models are discussed and in [7], where non-adiabatic pressure loss boundary con-27 dition is discussed. One-dimensional tools are also used in design process for 28 fast evaluation of turbine capabilities as in [8]. In [9] a Taylor series expansion 29 is used to develop a model able of predicting mass flow parameter of radial 30 turbines. 31 CFD models for turb...

ElsevierPayri González, F.; Olmeda, P.; Arnau Martínez, FJ.; Dombrovsky, A.; Smith, L. (2014 AbstractThe behavior of small turbochargers is deeply affected by heat transfer phenomena. The external heat losses of these engines are studied and a simplified model that takes into account both radiation and convective mechanisms has been proposed. The model has been adjusted in a turbocharger test bench for two different turbochargers, later on it has been validated against experimental measurements on an engine test bench. Finally, the model has been used to estimate the most important external heat flows among the different elements of the turbocharger.

ElsevierSerrano Cruz, JR.; Olmeda González, PC.; Arnau Martínez, FJ.; 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:10.1016Energy. 86:204-218. doi:10. /j.energy.2015 Turbocharger heat transfer and mechanical losses influence in predicting engines performance by using one-dimensional simulation codes

These days many research efforts on internal combustion engines are centred on optimising turbocharger matching and performance on the engine. In the last years a number of studies have pointed out the strong effect on turbocharger behaviour of heat transfer phenomena. The main difficulty for taking into account these phenomena comes from the little information provided by turbocharger manufacturers. In this background, Original Engine Manufacturers (OEM) need general engineering tools able to provide reasonably precise results in predicting the mentioned heat transfer phenomena.Therefore, the purpose of this work is to provide a procedure, applicable to small automotive turbochargers, able to predict the heat transfer characteristics that can be used in a lumped 1D turbocharger heat transfer model. This model must be suitable to work coupled to whole-engine simulation codes (such as GT-Power or Ricardo WAVE) for being used in global engine models by the OEM. Moreover, the procedure must be capable to predict heat transfer effects using available data as external geometrical parameters of the turbocharger.To reach these several purposes, a description of the procedure to obtain correlations for heat transfer behaviour to be used in a lumped model is given. The procedure is based on several generalised correlations obtained from the evaluation of heat transfer properties of different turbochargers. The validity of the procedure is confirmed by simulations performed in GT-Power environment compared to experimental results both in a gas stand and in an engine test bench. The results of the validation show an acceptable level of accuracy using the proposed procedure. Furthermore, the advantages of the procedure are shown by comparing its results with the results of standard GT-Power simulations. In these last simulations only turbocharger maps are used without a turbocharger heat transfer model. Further analysis of these results evidences that the simple procedure of using general correlations for heat transfer properties in a lumped model is accurate enough to predict turbine outlet temperature much better than standard GT-Power model. This parameter is crucial for after treatment modelling and design as well as for two stage turbocharging.

A nalysis and M ethodo logy to C haracterize H eat T ran sfer P henom ena in A utom otive TurbochargersIn the present work a comprehensive study of turbocharger heat transfer phenomena is discussed, showing their relevance compared to gas enthalpy variations through the tur bomachinery. The study provides an experimental methodology to consider the different heat fluxes in the turbocharger and modeling them by means of a lumped capacitance heat transfer model (HTM). The input data required for the model are obtained experi mentally by a proper combination of both steady and transient tests. These tests are per formed in different test benches, in which incompressible fluids (oil) and compressible fluids (gas) are used in a given sequence. The experimental data allows developing heat transfer correlations for the different turbocharger elements. These correlations take into account all the possible heat fluxes, discriminating between internal and external heat transfer. In order to analyze the relative importance of heat transfer phenomena in the predictability of the turbocharger performance and the different related variables; model results, in hot and cold conditions, have been compared with those provided by the stand ard technique, consisting on using look up maps (LUM) of the turbocharger. The analysis of these results evidences the highly diabatic operative areas of the turbocharger and it provides clearly ground rules for using hot or cold turbocharger maps. In addition, paper discussion advises about using or not aHTM, depending on the turbocharger variables and the operative conditions that one desires to predict. Paper concludes that an accu rate prediction of gas temperatures at turbine and compressor outlet and of fluid temper atures at water and oil ports outlet is not always possible without considering heat transfer phenomena in the turbocharger.