The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel short-circuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems. Jet ignition, i.e., the use of prechambers to accelerate the combustion process, turned out to be an effective way to perform LTC. The present work aims at proving the feasibility of adopting passive prechambers in a high-pressure, direct injection, two-stroke engine through non-reactive computational fluid dynamics analyses. The goal of the analysis is the evaluation of the prechamber performance in terms of both scavenging efficiency of burnt gases and fuel/air mixture formation inside the prechamber volume itself, in order to guarantee the mixture ignitability. Two prechamber geometries, featuring different aspect ratios and orifice numbers, were investigated. The analyses were replicated for two different locations of the injection and for three operating conditions of the engine in terms of revolution speed and load. Upon examination of the results, the effectiveness of both prechambers was found to be strongly dependent on the injection setup.

Electrically Assisted Turbochargers (EATs) have shown the potential of solving turbo-lag issues and improving exhaust energy recovery in turbocharged engines. Ultra-High-Speed (UHS) Permanent Magnet Synchronous Machines (PMSMs) were found to be well suited for EAT use. However, data required for preliminary system modelling are hard to come by and literature typically presents electrical quantities and power losses of a single operating point. This paper presents an easy-to-use approach for developing in the Simulink ambient a simplified model capable of providing Motor-Generator Unit (MGU) efficiency maps starting from single-point data and to easily perform machine scaling taking account of rotordynamics constraints.

Two-stroke (2S) engines still play a key role in the global internal combustion engine (ICE) market when high power density, low production costs, and limited size and weight are required. However, they suffer from low efficiency and high levels of pollutant emissions, both linked to the short circuit of fuel and lubricating oil. Low- and high-pressure direct injection systems have proved to be effective in the reduction of fuel short circuiting, thus decreasing unburnt hydrocarbons and improving engine efficiency. However, the narrow time window available for fuel to be injected and homogenized with air, limited to few crank-angles, leads to insufficiently homogenized fuel-air mixtures and, as a consequence, to incomplete combustions. The use of prechambers can be a well-suited solution to avoid these issues. In fact, the faster combustion which results from the ignition process by hot turbulent jets, allows us to delay the ignition advance, thus achieving a more homogenous mixture inside the combustion chamber; furthermore, the improved mixing process which occurs inside the prechamber extends the lean flammability limit of the engine. The present paper shows the preliminary experimental results of the use of passive prechambers on a crank-scavenged Low-Pressure Direct Injection (LPDI) 2S 50 cm³ engine for motorcycle use. Analyses were carried out at full load conditions in order to understand the effects of adopting a prechamber on the engine performance, in terms of Indicating Mean Effective Pressure (IMEP), heat release, and cycle-to-cycle variation. Diameter of orifices was varied so as to achieve best performance on the investigated engine. Results prove that a faster and more effective combustion process can be achieved in the LPDI engine. Furthermore, the analysis highlights the importance of choosing the right flow-passage area of orifices, which is related to the prechamber volume, to avoid excessive in-cylinder pressure peaks or a too early pressure decrease during the expansion phase

Weather routing (WR) systems are widely adopted in the maritime transport since safety of goods and saving of fuel are crucial for shipping companies. However, the need of protecting the local coasts and reducing CO₂ emission is making WR attractive even for the market of leisure boats, especially if comfort and safety are also accounted. In the present study, a prototype of a WR system is presented. The developed tool implements the Dijkstra’s algorithm to find the fuel-optimal path while ensuring comfort and safety. A computationally efficient digital twin of a planing boat, based on a 2D+t model and a powertrain mapped model, has been implemented for the estimation of the fuel consumption and the evaluation of vertical accelerations. The methodology for the acquisition of online weather data is presented, together with the strategy for the assessment of comfort and habitability. The application of the WR tool in a typical path of the Tuscan Archipelago shows improvements in fuel usage and comfort even in moderate weather conditions. The influence of each weather variable on fuel efficiency is assessed, highlighting the requirement of an accurate dynamic modelling. Criteria for the graph design are also outlined, showing a wrong estimation of comfort and fuel usage in case of low-definition graphs. The paper proves the potential and the effectiveness of the developed tool, moving toward a greener and more comfortable navigation in local seas.

The target of motorsport has always been maximising the performance. Increasingly stringent rules on fuel usage, however, have moved the research on engine design and control rules toward efficiency enhancement. Turbocharging is a typical solution to match both targets; however, it suffers from the turbo-lag phenomenon, especially when the maximum power is limited by an air restrictor. In the present paper, an investigation on a combined solution aimed at contemporarily improving transient response and efficiency in FSAE events, both leading to a higher score, is carried out. In detail, the adoption of an anti-lag valve and an efficiency-based control schedule, markedly exploiting the wastegate actuator, is proposed in place of the classic combination blow-off valve and performance-based strategy. The analyses were carried out on the 520 cm³ single-cylinder 4-stroke turbocharged engine of the Firenze Race Team. In order to predict the potential of the proposed load control solution, a predictive combustion engine model (which design process is exhaustively described in the paper), adopting the K-k-ε turbulence model, was developed in the GT-Suite software and calibrated by means of test-bench data and 3-D CFD analyses. A vehicle model, calibrated by means of telemetry data, was finally developed to compare the proposed solution to the baseline load control system in typical race conditions, showing benefits in terms of performance, drivability, and efficiency.