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Emission regulations have become increasingly stringent in recent years. Current regulations need the development of a new worldwide driving cycle which gives greater weight to the pollutants emitted during transient phases or cold starts. Powertrains contain a large number of components such as multistage turbocharger systems; exhaust gas recirculation, after-treatment devices and sometimes an electric motor. In this context, 0D predictive models of heat transfer in the exhaust line, calibrated with experimental data, are particularly interesting. Many investigations are related to the development of precise control laws in order to optimize the light-off of after-treatment elements during the engine starting phase. A better understanding of the thermal phenomena occurring in the exhaust line is necessary. To study the heat transfer in the exhaust line of a Diesel engine during transient conditions, the temperature in the exhaust line must be known precisely.

Today turbochargers are used by car manufacturers on Diesel engines and on an increasing number of gasoline engines, especially in the scope of downsizing. This component has to be well understood and modeled as simulation is widely used at every step of the development. Indeed development cost and time have to be reduced to fulfill both customers’ wishes and more stringent emissions standards. Current turbocharger simulation codes are mostly based on look-up tables (air mass flow and efficiency) given by manufacturers. This raises two points. Firstly, the characteristics are known only in the same conditions as manufacturers’ tests. Secondly, the turbine efficiency given by turbochargers manufacturers is the product of the isentropic efficiency and the turbocharger mechanical efficiency. This global efficiency is suitable for the calculation of the power transferred to the compressor.

Pollutant emissions standards (such like EURO 6 in Europe) are increasingly severe and force a search of new in-cylinder strategies and/or aftertreatment devices / schemes at a reasonable cost. On a conventional Diesel engine an excess of air is usually used to allow very high combustion efficiencies and reasonable levels of soot which can then be after-treated in a diesel particulates filter (DPF). As a consequence, NOx emissions cannot be easily after-treated (lean NOx trap (LNT) and selective catalytic reduction (SCR) are quite expensive even if effective, solutions), as a result they are generally controlled by means of internal measures such as High Pressure (HP) or Low Pressure (LP) exhaust gas recirculation (EGR). In light of ever more stringent NOx emissions regulations, NOx aftertreatment devices seem to be becoming unavoidable.

In order to reduce greenhouse gases and respect stringent pollutant emission regulations, the modern engine is increasingly required to incorporate energy recovery systems to enhance performance and increase efficiency. This paper deals with the exhaust energy recovery through turbocompounding. Both series and parallel turbocompounds are discussed. In the first part of the document, literature on turbocompounding is introduced. Then a simulation study carried on AMESim software, using a 2L Diesel engine model is presented. The parallel turbocompounding is simulated by expanding a part of the exhaust gases in a converging nozzle instead of the turbocharger turbine. The power produced is evaluated as a function of the pressure drop in case a turbine is mounted instead of the nozzle. A global study over the entire engine map is described, and two steady state points 2000 rpm, 8 bar and 3500 rpm, 7 bar are chosen.

A new methodology for modeling engine intake has been presented; it is based on a transfer function relating pressure response and mass flow rate that makes use of the corresponding frequency spectrum obtained on the so-called “dynamic flow bench”. This new approach provides a way to obtain fast and robust results, which take into account all the phenomena inherent to compressible unsteady flows. Recently the potential of this method has been explored by incorporating it in a GT-Power model to produce a coupled frequency - time domain simulation of a naturally aspirated engine. The method exhibited promising results. One strategy utilized to combat the increasingly stringent emissions standards and reduce fuel consumption is to employ downsized turbocharged engines equipped with charge air coolers (CAC). Therefore, research and development must focus not only on naturally aspirated engines but also on turbocharged ones.

To comply with the evermore stringent polluting emission regulation, such as Euro 6c and its new homologation WTLP cycle, the use of turbochargers, already high in Diesel engines, is steeply rising in Gasoline ones. Turbochargers come into a large variety of implementations such as single/two stage(s) or even parallel. In the meantime, car manufacturers intend to decrease development cost and time by using more and more simulation over experimental measurements. However, usual turbocharger models have not followed this trend of modernity. While the heating part of the standard driving test cycle becomes a major topic, turbocharger models are still map based, built from turbocharger manufacturer’s data and measured only in hot conditions. To improve their accuracy, new turbocharger models need to take into account the thermal transfers.