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Global automotive fuel economy and emissions pressures mean that 48 V hybridisation will become a significant presence in the passenger car market. The complexity of powertrain solutions is increasing in order to further improve fuel economy for hybrid vehicles and maintain robust emissions performance. However, this results in complex interactions between technologies which are difficult to identify through traditional development approaches, resulting in sub-optimal solutions for either vehicle attributes or cost. The results presented in this paper are from a simulation programme focussed on the optimisation of various advanced powertrain technologies on 48 V hybrid vehicle platforms. The technologies assessed include an electrically heated catalyst, an insulated turbocharger, an electric water pump and a thermal management module.

The ability to switch off the internal combustion engine (ICE) during vehicle operation is a key functionality in hybrid powertrains to achieve low fuel economy. However, this can affect driveability, namely acceleration response when an ICE re-engagement due to a driver initiated torque demand is required. The ICE re-start as well as the speed and load synchronisation with the driveline and corresponding vehicle speed can lead to high response times. To avoid this issue, the operational range where the ICE can be switched off is often compromised, in turn sacrificing fuel economy. Based on a 48V off-axis P2 hybrid powertrain comprising a lay-shaft transmission we present an up-front simulation methodology that considers the relevant parameters of the ICE like air-path, turbocharger, friction, as well as the relevant mechanical and electrical parameters on the hybrid drive side, including a simplified multi-body approach to reflect the relevant vehicle and powertrain dynamics.

There is no doubt that the modern internal combustion engine (ICE) is approaching its theoretical limits in terms of efficiency. Owed to the fact that the conversion of fuel-bound chemical energy into effectively usable power by combustion is largely defined by the fuel properties, the combustion process and the implicit phenomenon of abnormal combustion is a governing factor that limits further efficiency increases. However, the use of a knock-resistant fuel such as methane is leading to a significant raise in the average combustion pressure and total engine efficiency. In turn this requires a base engine architecture that is specially designed to cater the increased thermal and mechanical requirements so that the positive fuel properties can be fully exploited. Furthermore, an improvement of the energy balance is achieved by utilizing the kinetic energy stored in the vehicle by means of electrical recovery.

High combustion pressure in combination with high pressure gradient, as they e.g. can be evoked by high efficient combustion systems and e.g. by alternative fuels, acts as broadband excitation force which stimulates natural vibrations of piston, connecting rod and crankshaft during engine operation. Starting from the combustion chamber the assembly of piston, connecting rod and crankshaft and the main bearings represent the system of internal vibration transfer. To generate exact input and validation values for simulation models of structural dynamic and elasto-hydrodynamic coupled multi-body systems, experimental investigations are done. These are carried out on a 1.5-l inline four cylinder Euro 6 Diesel engine. The modal behaviour of the system was examined in detail in simulation and test as a basis for the investigations. In an anechoic test bench airborne and structure-borne noises and combustion pressure are measured to identify the engine´s vibrational behaviour.

The application of a turbocharger, having an electric motor/generator on the rotor was studied focusing on the electric energy recuperation on a downsized gasoline internal combustion engine (turbocharged, direct injection) using 1D-calculation approaches. Using state-of-the art optimization techniques, the settings of the valve timing was optimized to cater for a targeted pre-turbine pressure and certain level of residual gases in the combustion chamber to avoid abnormal combustion events. Subsequently, a steady-state map of the potential of electric energy recuperation was performed while considering in parallel different efficiency maps of the potential generator and a certain waste-gate actuation strategy. Moreover, the results were taken as input to a WLTP cycle simulation in order to identify any synergies with regard to fuel economy.

The impact of the number of cylinders on two downsized gasoline engines on driving habits in the same passenger-vehicle type was investigated. This was carried out with two similar vehicles, equipped with an in-line three cylinder (i3) and an in-line four cylinder (i4) engine, both having same power, torque and transient-response behaviour. Both engine types were mated to six-speed manual transmissions with same gear-ratios and dual-mass flywheel characteristics. The study was performed by letting a statistically significant number of subjects driving the same route and both vehicles consecutively. The relevant data during driving were recorded simultaneously from either vehicle integrated sensors (CAN), and secondary transducers.

A trend in vehicle propulsion of converting from power sources such as a naturally aspirated internal combustion engine to turbocharged engines (Downsizing), multi-mode combustion systems (stratified charged combustion, HCCI) or multi-power source propulsion systems such as hybrid power-trains, can be observed. The subsequent switching between these different combustion modes or power sources, and, more importantly, the incorporation of turbochargers (turbo-lag) can affect the driveability, i.e. the smoothness of torque provision during transient driving manoeuvres. So far there is a lack of methodologies that can quantify and objectively describe vehicle transient acceleration events from a driver's point of perception. Thus an approach was developed while incorporating the acceleration transducers of men, the vestibular apparatus, into a longitudinal vehicle model with a transient engine / powertrain model.

Transient operation of turbocharged engines is mostly optimised in the light of quickness of response and the provision of the demanded torque. The time from demanded boosted torque to delivered torque above the maximum torque provided by the natural aspirated torque value is known as turbo-lag. This could reveal as an issue for small gasoline turbo-charged engines with a displacement of 1.0ltr or lower. These small types of engines are moving more and more in the focus for automobile applications. To provide the required power and torque, gasoline direct injection and turbo-charging are helpful in order to enable a reduction of fuel consumption by both de-throttled operation over a large area of operation and improved thermal efficiency among others achieved by maintaining an appropriate compression ratio.

Downsizing of Gasoline Direct Injection engines is a way to reduce greenhouse emissions. A downsized engine will have a much higher specific power density, caused by a significant higher brake mean effective pressure (BMEP). This higher BMEP can be enabled by a turbocharger in combination with gasoline direct injection. In addition, good efficiency is accompanied by fast combustion, i.e. a fast heat release rate. All these factors can lead to an increased level of combustion noise excitation, which means in turn a higher level of radiated noise. Thus a study on impact factors on the combustion noise excitation was carried out on a small I4-gasoline engine, having spray-guided direct injection, combined with a turbocharger. It was found that high intake tumble levels, which e.g. are caused by the intake port geometry or different actuation strategies of the swirl control device, can lead to an increased level of noise and roughness.

The European Automotive Industry has committed to reduce the emissions. In order to comply with these CO2 requirements, the introduction of fuel efficient technologies is absolutely mandatory. Therefore ‘Downsizing’ is a known way to reduce part load fuel consumption by combining significant displacement reduction with turbocharging to achieve equivalent torque and power levels [1]. To fulfill these demands, an inline gasoline three cylinder powertrain with turbocharged direct injection (SCi Turbo) has been developed. The challenge during the development of such a powertrain is that no degradation on customer demands regarding the key criteria, among others driveability and NVH, is allowed. This paper will show the powertrain components that are affected most by these NVH attributes; this concerns mainly the engine and the power conversion system.