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Heavy duty truck engines are quite difficult to electrify, due to the large amount of energy required on-board, in order to achieve a range comparable to that of diesels. This paper considers a commercial 6-cylinder engine with a displacement of 12.8 L, developed in two different versions. As a standard diesel, the engine is able to deliver more than 420 kW at 1800 rpm, whereas in the CNG configuration the maximum power output is 330 kW at 1800 rpm. Maintaining the same combustion chamber design of the last version, a theoretical study is carried out in order to run the engine on Hydrogen, compressed at 700 bar. The study is based on GT-Power simulations, adopting a predictive combustion model, calibrated with experimental results. The study shows that the implementation of a combustion system running on lean mixtures of Hydrogen, permits to cancel the emissions of CO2, while maintaining the same power output of the CNG engine.

One of the main challenges related to the use of Hydrogen in Internal Combustion Engines is the trade-off between NOx emissions and brake power output: on the one hand, a lean premixed charge (Lambda ≈2.5) is generally able to provide a regular and efficient combustion, yielding near-zero NOx emissions; on the other hand, the power density tends to be very poor, due to the huge amount of air required by the thermodynamic process. As a further penalization, the injection of a gaseous fuel during the intake process has a negative impact on volumetric efficiency. Supercharging can be a solution for addressing the problem, but at the cost of an increase of complexity, cost and overall dimensions. An alternative path is represented by the 2-stroke cycle, and, in particular, by the opposed piston (OP) design. Most of the existing OP engines are compression ignited, but Spark ignition and direct fuel injection can be implemented without relevant modifications to the layout of cylinders.

The paper presents a preliminary study on a virtual 2-stroke 3-cylinder 0.9 L DI SI supercharged engine running on Hydrogen (H2), able to meet both high performance targets and ultra-low emissions limits (NOx<20 ppm). Combustion is similar to a conventional 4-stroke H2 DI engine, while the design of the cylinder and the actuation law of both intake and exhaust valves are specifically optimized for the 2-stroke cycle. In comparison to a more conventional 2-stroke loop scavenged engine, with piston-controlled ports, the use of poppet valves enables a more flexible control of the gas exchange process and to maintain the same design of a 4-stroke engine for pistons, cylinders block, crankcase and lubrication system. On the other hand, it is more difficult to avoid the short-circuit of the fresh charge, while permeability of the valves becomes quite critical at high engine speed.

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 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.

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.

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.

This paper presents the development of a parallel hybrid power unit for Formula SAE application. In particular, the system is made up of a brand new, single-cylinder 480 cc internal combustion engine developed on the basis of the Ducati “959 Superquadro” V90 2-cylinders engine. The thermal engine is assisted by a custom electric motor (30 kW), powered by a Li-Ion battery pack. The performance of the ICE has been optimized through CFD-1D simulation (a review of this activity is reported in a parallel paper). The main design goal is to get the maximum amount of mechanical energy from the fuel, considering the car typical usage: racing on a windy track. The Ducati “959 Superquadro” engine is chosen because of its high power-to-weight ratio, as well as for its V90 2-cylinder layout.

Hybridization is a mainstream technology for automobiles, and its application is rapidly expanding in other fields. Marine propulsion is one such field that could benefit from electrification of the powertrain. In particular, for boats to sail in enclosed waterways, such as harbors, channels, lagoons, a pure electric mode would be highly desirable. The main challenge to accomplish hybridization is the additional weight of the electric components, in particular the batteries. The goal of this project is to replace a conventional 4-stroke turbocharged Diesel engine with a hybrid powertrain, without any penalty in terms of weight, overall dimensions, fuel efficiency, and pollutant emissions. This can be achieved by developing a new generation of 2-Stroke Diesel engines, and coupling them to a state-of-the art electric system. For the thermal units, two alternative designs without active valve train are considered: opposed piston and loop scavenged engines.

This work reports a CFD study on a 2-stroke (2-S) opposed piston high speed direct injection (HSDI) Diesel engine. The engine main features (bore, stroke, port timings, et cetera) are defined in a previous stage of the project, while the current analysis is focused on the assembly made up of scavenge ports, manifold and cylinder. The first step of the study consists in the construction of a parametric mesh on a simplified geometry. Two geometric parameters and three different operating conditions are considered. A CFD-3D simulation by using a customized version of the KIVA-4 code is performed on a set of 243 different cases, sweeping all the most interesting combinations of geometric parameters and operating conditions. The post-processing of this huge amount of data allow us to define the most effective geometric configuration, named baseline.

The paper presents a numerical investigation, aimed to explore the potential of 2-stroke Diesel engines, able to meet Euro VI requirements, for application to medium size commercial vehicles (power rate: 80 kW at 2600 rpm, max. torque 420 Nm from 1200 to 1400 rpm). The study is based on experimental performance of a highly developed 4-stroke engine. Two different designs are considered: Loop and Uniflow scavenging, the latter obtained through an opposed piston configuration. In both cases, no poppet valves are used, and the lubrication is provided by a 4-stroke-like oil sump. The study started with the development of a 4-stroke EURO VI engine, on the basis of a previous EURO IV version. A prototype of the new engine (named 430) was built and tested.

The paper reviews the design of the supercharging system for a strongly downsized engine, to be installed on a sport car. Design is supported by cfd-1d engine simulations, using an experimentally calibrated model. The goal of the supercharging system is to deliver the required values of boost pressure at steady operating conditions, and to maintain or improve the full size engine response during acceleration (one of the most critical issues for downsized engines). Two options have been considered: 1) two-stage turbocharging, with two small turbochargers as a high-pressure stage, and one big turbo as low pressure stage (referred to as “TRITURBO”; 2) two-stage supercharging made up of one low pressure stage turbocharger and one electric supercharger (referred to as “E-SUPER”).

Interest in 2-stroke engines has been recently renewed by several prototypes, developed for the automotive and/or the aircraft field. Loop scavenging, with piston controlled ports is particularly attractive, but the configurations successfully developed in the past for motorbike racing (in particular, the 125cc unit displacement, crankcase pump engines), are not suitable for automotive applications. Therefore, new criteria are necessary to address the scavenging system design of the new generation of 2-stroke automobile/aircraft engines. The paper reviews the transfer ports optimization of a loop scavenged 2-stroke cylinder, whose main parameters were defined in a previous study. The optimization has been carried by means of a parametric grid, considering 3 parameters (2 tilt angles, and the focus distance), and 3 different engine speeds (2000-3000-4000 rpm, assuming a Diesel engine). A set of scavenging CFD-3d simulations have been performed by using a customized version of KIVA-3V.

Two-stroke diesel engines could be a promising solution for reducing carbon dioxide (CO2) emissions from light-duty vehicles. The main objective of this study was to assess the potential of two-stroke engines in achieving a substantial reduction in CO2 emissions compared to four-stroke diesel baselines. As part of this study 1-D models were developed for loop scavenged two-stroke and opposed piston two-stroke diesel engine concepts. Based on the engine models and an in-house vehicle model, projections were made for the CO2 emissions for a representative light-duty vehicle over the New European Driving Cycle and the Worldwide Harmonized Light Vehicles Test Procedure. The loop scavenged two-stroke engine had about 5-6% lower CO2 emissions over the two driving cycles compared to a state of the art four-stroke diesel engine, while the opposed piston diesel engine had about 13-15% potential benefit.

The third generation of biodiesels, derived from microalgae, is one of the most interesting options for the replacement of fossil fuels. While the use of first generation biodiesels on different types of compression ignition engines is well documented in the open literature, much less information is available on algal fuels. As a matter of fact, the influence on combustion and pollutant emissions is not definitively assessed, depending on the combination of the specific features of both fuel and engine. The aim of this paper is to analyze the combustion process in a small industrial engine fueled by an algal Biodiesel, blended with standard Diesel fuel. The blend composition is the one typically used in most applications, i.e. 20% of biodiesel and 80% of Diesel (B20).

Among all the reciprocating internal combustion engines, gasoline two-strokes can reach the highest specific power, making this technology a natural enabler of downsizing and/or down-speeding. In addition, multi-cylinder 2-stroke engines may be an ideal match for electrical superchargers, providing very efficient power units. The paper explores through CFD-1d simulations and empirical hypotheses the potential of a 3-cylinder, 1.0 liter, GDI 2-stroke turbocharged engine featuring a patented rotary valve for the optimization of the scavenging process, the latter being of the loop type (piston-controlled ports). The lubrication system is the same of a 4-stroke engine (no crankcase pumps). The supercharging system is made up of a turbocharger and an electric compressor, serially connected. The power of the electric compressor is limited to 2 kW, in order to comply with standard automotive 12 V electric systems.

The paper compares two different design concepts for a range extender engine rated at 30 kW at 4500 rpm. The first project is a conventional 4-Stroke SI engine, 2-cylinder, 2-valve, equipped with port fuel injection. The second is a new type of 2-Stroke loop scavenged SI engine, featuring a direct gasoline injection and a patented rotary valve for enhancing the induction and scavenging processes. Both power units have been virtually designed with the help of CFD simulation. Moreover, for the 2-Stroke engine, a prototype has been also built and tested at the dynamometer bench, allowing the authors to make a reliable theoretical comparison with the well assessed 4-Stroke unit.

The basic requirements for range extender engines are low cost, compact dimensions, high specific power, good efficiency, low pollutant emission levels, excellent NVH behavior. For a power rate lower than 30 kW, it is very difficult to find an off-the-shelf engine meeting all the requirements listed above, so that a new generation of dedicated engines is under development. Following a preliminary theoretical work presented in 2012 [1], the current paper reviews the design process and the first experimental tests carried out on a novel 2-stroke GDI single-cylinder engine, rated at 30 kW at 4500 rpm, featuring a patented induction valve and a piston pump for scavenging. A prototype has been designed with the support of CFD simulations, then built and tested at the BRC laboratories, in Cherasco (Italy).

Biodiesel from Algae appears as an almost ideal solution to address the problem of decreasing availability of conventional fossil fuels, as well as to reduce the impact in terms of CO2 of internal combustion engines. In comparison to other biodiesels, algae do not compete for the land use with food cultures, and they have an excellent oil yield. Despite the significant amount of technical reports about the production process of algal biodiesel, detailed information about the application to current production engines is almost completely missing. The present paper describes the experimental campaign carried out on a current production 4-cylinder, 4-stroke naturally aspirated Diesel engine, running on standard Diesel oil and on a blend made up of 20% of oil manufactured by transesterification of Microalgae (B20). Performance and emission parameters have been measured over the whole engine operating range.