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Determination of heat flows inside turbochargers by means of a one dimensional lumped model

Mathematical and Computer Modelling, 2013

In the present paper a methodology to calculate the heat fluxes inside a turbocharger from diesel passenger car is presented. The heat transfer phenomenon is solved by using a one dimensional lumped model that takes into account both the heat fluxes between the different turbocharger elements, as well as the heat fluxes between the working fluids and the turbocharger elements. This heat transfer study is supported by the high temperature differences between the working fluids passing through a typical diesel turbocharger. These flows are the hot exhaust gases coming from the diesel engine exhaust passing through the turbine, the fresh air taken by the compressor, and the lubrication oil passing through the housing. The model has been updated to be used with a new generation of passenger car turbochargers using an extra element in the heat transfer phenomenon that is the water cooling circuit. This procedure allows separating the aerodynamic from the heat transfer effects, permitting study the behavior of compressor and turbine in a separated way.

Analysis and methodology to characterize heat transfer phenomena in automotive turbochargers

2015

In 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.

Importance of Heat Transfer Phenomena in Small Turbochargers for Passenger Car Applications

Nowadays turbocharging the internal combustion engine has become a key point in both the reduction of pollutant emissions and the improvement of engine performance. The matching between turbocharger and engine is difficult; some of the reasons are the highly unsteady flow and the variety of diabatic and off-design conditions the turbocharger works with. In present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be analyzed. These phenomena will be studied from the point of view of internal heat transfer between turbine and compressor and with a one-dimensional approach. A series of tests in a gas stand, with steady and pulsating hot flow in the turbine side, will be modeled to show the good agreement in turbocharger enthalpies prediction. The goodness of the model will be also shown predicting turbine and compressor outlet temperatures. An accurate prediction of these parameters is a key factor to make easier the design of intercooler and aftertreatment devices.

Heat transfer analysis in a turbocharger turbine: An experimental and computational evaluation

Applied Thermal Engineering, 2012

This paper presents the performance of a turbocharger under non-adiabatic conditions in order to assess the impact of heat transfer. A commercial turbocharger was installed on a 2.0 l diesel engine and measurements were conducted for a range of engine speeds and loads. The test results enabled to assess the impact of the engine on the temperature distribution of the bodies constituting the turbocharger, quantify the heat fluxes through the turbocharger and evaluate their effects on the deterioration of compressor performance.

Modelling of turbocharger heat transfer under stationary and transient engine operating conditions

A lumped capacity heat transfer model has been developed and compared to measurements from a turbocharger operating on a 2.2L Diesel engine under steady and transient conditions ranging from 1000-3000rpm and 2-17bar BMEP. The model parameters have been estimated based on similar devices and this study quantifies the errors associated with this approach. Turbine outlet gas temperature prediction was improved with RMSE reduced from 29.5 o C to 13 o C. A sensitivity study showed the parameters of the heat transfer model influence gas temperatures by only ±4 o C but housing temperatures by up to 80 o C. Transient simulations showed how errors in the thermal capacitance also lead to errors. This study shows the importance of undertaking a full thermal characterisation and the need for accurate adiabatic maps in turbocharger simulations.

Turbocharger heat transfer modeling under steady and transient conditions

In the field of automotive propulsion, environmental issues (need for drastic reduction of greenhouse gases) and diminishing fossil fuels supplies enhance the need to reduce fuel consumption. To reach this goal, a possible solution is downsizing. Unfortunately, the degradation of the transient performance of the engine limits the expected benefits of downsizing. Engine manufacturers try to improve turbocharger matching using simulation. However, the literature and experiments on a turbocharger test bench show that, contrary to general opinions, heat transfer can influence the turbocharger performance. Thus it seems essential to determine and correlate the different types of heat transfer phenomena occurring in a turbocharger. First a complete experimental characterization of turbocharger heat transfer is performed in steady and transient conditions. The experimental results are used to correlate turbocharger heat transfer coefficients. Then, the equivalent heat transfer resistance method is explained. The correlations obtained are then used in this method to calculate all heat transfer interactions within the turbocharger and transferred to the surroundings in steady and transient conditions. In each case, comparisons between numerical and experimental results are performed to verify the quality of the method proposed.

Impact of the Heat Transfer on the Performance Calculations of Automotive Turbocharger Compressor

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2011

Influence des transferts thermiques sur le calcul des performances des compresseurs de suralimentation-En général, les turbocompresseurs pris en compte dans les logiciels de simulation moteur sont modélisés de façon adiabatique. Cependant, les tests expérimentaux effectués au laboratoire montrent que ce n'est pas toujours le cas. L'utilisation directe des champs de fonctionnement fournis par les constructeurs de turbomachines n'est alors plus possible. Une évaluation quantitative de ces transferts, basée sur des tests réalisés sur un banc d'essais turbo à air chaud, est présentée. Puis ils sont pris en compte afin de calculer les caractéristiques réelles de fonctionnement d'un compresseur. La différence avec le modèle adiabatique apparaît très importante pour les faibles puissances compresseur. Ceci correspond aux faibles charges moteur.