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Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures. Several stabilization techniques were studied to increase the compressor operating range without sacrificing the compressor efficiency. The paper presents an experimental study of one of these techniques, the axial variable inlet guide vanes (VIGV). Test rigs were put up to conduct two different experiments. The first was to study the effect of pre- rotation generated by VIGVs on the overall compressor performance and the second to determine the pressure loss through the VIGVs and to analyze the flow downstream the VIGV system using LDA (laser Doppler Anemometry) measurement.

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures, and hence the measurement of the performance maps of both compressor and turbine. Automotive manufacturers use mainly numerical simulations for internal combustion engines simulations, hence the need of an accurate extrapolation model to get a complete turbine performance map. These complete maps are then used for internal combustion engines calibration. Automotive manufacturers use commercial softwares to extrapolate the turbine narrow performance maps, both mass flow characteristics and the efficiency curve.

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.

Downsizing has nowadays become the more widespread solution to achieve the quest for reaching the fuel consumption incentive. This size reduction goes with turbocharging in order to keep the engine power constant. To reduce the development costs and to meet the ever tightening regulations, car manufacturers rely more and more on computer simulations. Thus developing accurate and predictable turbocharger models functioning on a wide range of engine life cases became a major requirement in industrial projects. In the current models, compressors and turbines are represented by look-up tables, experimentally measured on a turbocharger test bench, at steady point and high inlet turbine temperature. This method results in limited maps : on the one hand the compressor surge line and on the other hand the flow resistance curve behind the compressor. Mounted on an engine, the turbocharger encounters a wider scale of functioning points.

Residual gas plays a crucial role in the combustion process of SI engines. It acts as a diluent and has a huge impact on pollutant emissions (NOx and CO emissions), engine efficiency and tendency to knock. Therefore, characterizing the residual gas fraction is an essential task for engine modelling and calibration purposes. Thus, an in-cylinder sampling technique has been developed on a spark ignition VVT engine to measure residual gas fraction. Two gas sampling valves were flush mounted to the combustion chamber walls; they are located between the 2 intake valves and between intake and exhaust valves respectively. In-cylinder gas was sampled during the compression stroke and stored in a sampling bag using a vacuum pump. The process was repeated during a large number of engine cycles in order to get a sufficient volume of gas which was then characterized with a standard gas analyzer.

Energy recovery of internal combustion engines has proved to be of primary interest to increase engine global efficiency. The motivation behind is to meet future fuel economy requirements and more stringent emissions regulations. Among all engine waste, research has shown that exhaust energy is the most promising solution due to its high availability. In this context, this paper deals with the analysis of the potential of exhaust heat recovery, especially by a turbocompound system. Turbo-compounding is already established in heavy-duty engines, in which an additional stage of expansion is made through an exhaust recovery turbine. This technique is now being studied for small displacement engines. In the first part of this document, a short history on turbocompounding is presented. Then we present a simulation study conducted on AMESim software, using a 0D 2L diesel engine model, calibrated to fit real engine test bench results.

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.

Unsteady intake wave dynamics have a first order influence on an engine's performance and fuel economy. There is an abundant literature particularly for naturally aspirated SI engines on the subject of intake manifolds and primary runner lengths aimed to achieve a tuned intake air line. A more demanding design for today's engines is to increase efficiency to meet the requirements of lower fuel consumption and CO2 emissions. Today's tendencies are downsizing the engine to meet these demands. And for drivability purposes, the engine is combined with a turbocharger coupled with a charge air cooler. However, when the engine's displacement is reduced, it will be very dependent on its boosting system. A particularly interesting point to address corresponds to the engine's operation in the low speed range and during transients where the engine has large pumping losses and poor boost pressure. This operation point can be optimized using acoustic supercharging techniques.

Usually, the simulation of a turbocharger included in a diesel engine model relies typically on the assumption of adiabaticity for the compressor. However experiments on a turbocharger test bench show that the heat transfers from the turbine to the compressor have a major influence on the compressor performances. So the manufacturers maps must be modified or used with a new method taking into account heat transfers. The methods proposed are a simple way to take into account heat transfers when the performance maps are used. They give results in relative good agreement with experimental measures in comparison to their easiness of use.

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.

Transport sector decarbonization is a key requirement to achieve Green House Gases emissions reduction. Future regulations and the large deployment of Low Emission Zones (LEZ) will lead to deep changes in this sector. The green hydrogen appears as a promising fuel, containing no carbon. H2 Internal combustion engine (H2 ICE) offers the opportunities of quick refueling, known reliability, relative low total cost of ownership. It is based on mature manufacturing processes and tools. Hence this solution can be commercialized in a near future, offering a short term pathway to decarbonization and a H2 market growth accelerator. However, hydrogen combustion in air generates NOx emissions, which should be reduced close to zero to fulfill future requirements. The HyMot project gathers seven public and industrial partners to develop an H2 engine for Light Commercial Vehicle (LCV) application offering the same performances as the replaced Diesel Engine.