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The trend of powertrain electrification is quickly spreading from the automotive field into many other sectors. For ultra-light aircraft, needing a total installed propulsion power up to 150 kW, the combination of a specifically developed internal combustion engine (ICE) integrated with a state-of-the-art electric system (electric motor, inverter and battery) appears particularly promising. The dimensions and weight of ICE can be strongly reduced (downsizing), so that it can operate at higher efficiency at typical cruise conditions; a large power reserve is available for emergency maneuvers; in comparison to a full electric airplane, the hybrid powertrain makes possible to fly at zero emissions for a much longer time, or with a much heavier payload. On the other hand, the packaging of a hybrid powertrain into existing aircraft requires a specific design of the thermal engine, that must be light, compact, highly reliable and fuel efficient.

Conventional 2-Stroke Spark Ignition engines are characterized by very high power to weight ratios and low manufacturing costs, but also by very low thermal efficiencies and high pollutant emissions. The last issues can be fully addressed by adopting an external scavenging pump and a direct or semi-direct injection system. The implementation of these solutions requires a strong support from CFD simulations, in particular for the optimization of air-fuel mixing and combustion. The paper presents a theoretical study on a new 2-Stroke, three cylinders, 1.3 L, Spark Ignition engine for light aircraft. The power-unit also includes an electric motor connected in parallel with the thermal engine. The latter features a supercharger and a two-stage injection system, made up of a set of low-pressure fuel injectors installed on the transfer ports, and a high-pressure gasoline injector on the cylinder head.

The paper reviews the CFD optimization of a motorcycle engine, modified for the development of a hybrid powertrain of a Formula SAE car. In a parallel paper, the choice of the donor engine (Ducati 959 Panigale: 2-cylinder, V90, 955 cc, peak power 150 HP at 10500 rpm, peak torque 102 Nm at 9000 rpm) is thoroughly discussed, along with all the hardware modifications oriented to minimize the new powertrain dimensions, weight and cost, and guarantee full reliability in racing conditions. In the current paper, the attention is focused on two main topics: 1) CFD-1D tuning of the modified Internal Combustion Engine (ICE), in order to comply with the Formula SAE regulations, as well as to maximize the power output; 2) simulation of the vehicle in racing conditions, comparison with a conventional combustion car and a full electric vehicle.

The motor generator unit installed on the turbocharger shaft (MGU-H) provides a fundamental contribution to the amazing performances and efficiency of the last Formula 1 power units. The excess of exhaust gas energy - normally dumped through the waste-gate - can be converted into electric energy and used to push the car, by means of a second motor generator unit installed on the engine crankshaft (MGU-K). The goal of this paper is to assess pros and cons of the MGU-H technology when applied to a family of engines of different displacement, installed on a typical passenger car. The influence of engine size and cylinders layout is investigated, under the same set of hypotheses, considering both transient and steady engine operations. The baseline engine is a commercial 2.0 L, SI, 4-cylinder in-line, rated at 200 HP at 4500-5000 rpm.

The new Stage 5 European regulation for Non Road Mobile Machinery has lowered the limits on pollutant emissions for all the categories of internal combustion engines. An interesting alternative to the implementation of sophisticated after-treatment systems is to downsize the engine, and provide the extra power for peak demands with an electric motor, installed in place of the flywheel. The paper explores the potential of this concept, applied to an industrial engine, manufactured by Kohler, and delivering a maximum power of 56 kW@2600 rpm. The study is supported by a comprehensive experimental characterization of the internal combustion engine and of the electric components. A representative duty cycle is also defined, on the basis of a set of measures, taken in real operating conditions. The analysis of this reference cycle is performed by using a GT-Suite model, comparing different power split strategies.