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The automotive industry is experiencing radical changes under the pressure of institutions that are increasingly reducing the limits on CO2 and pollutant emissions from road vehicles powered by internal combustion engines (ICEs). A way to decarbonize the transport sector without disrupting current automotive production is the adoption of alternative fuels for internal combustion engines (ICEs). Hydrogen is very attractive, thanks to the zero-carbon content and very high laminar flame speed, allowing for extending the lean burn limit. Other alternative fuels are methanol and ethanol. This work deals with the conversion of a small-sized passenger car powered by a three-cylinder spark ignition (SI) engine for the use of alternative fuels. In particular, the spark timing has been optimized to improve the fuel economy under every operating condition. The optimization procedure is based on the MATLAB/Simulink® R2024a-GT-Power co-simulation analysis and minimizes the fuel consumption by varying the spark timing independently for each cylinder. In particular, at full load, the algorithm reduces the spark timing only for the cylinder in which knock is detected, reducing fuel consumption by about 2% compared to the base calibration. This approach will be adopted in future activities to understand how the use of alternative fuels affects the ignition control strategy. [ABSTRACT FROM AUTHOR]

Abstract: Nanoparticle emissions continue to catch the attention because of their adverse health effects and their impact on the environment. Internal combustion engines are the major source of particle emissions in urban areas. The legislation proposes a stronger restriction for both diesel and gasoline engines. In particular, the European particle measurement program (PMP) has introduced particle number regulation for both diesel and gasoline engines. Great efforts are then devoted to the reduction of the particle emissions; nonetheless, the mechanisms governing particle formation are still not fully understood, neither for diesel nor for gasoline engines. The aim of the paper is the experimental characterization of particles emitted from a Port Fuel Injection (PFI) gasoline engine in steady state operating conditions. In particular, the impact of engine control variables (i.e. injection time and spark advance) and emissions control technologies (i.e. exhaust gas recirculation—EGR) on particle size and number was deeply investigated. Moreover, the effect of the dilution conditions was also analyzed. The investigation was carried out at the exhaust of a 1242cc PFI spark ignition (SI) engine. The engine test bench was equipped with a full-pass engine control system dSPACE MicroAutoBox and a scanning mobility particle sizer (SMPS) for particle counting and sizing. [Copyright &y& Elsevier]

Vehicle exhaust emission tests use exhaust sampling systems that dilute the exhaust gas with ambient air. The dilution factor DF is calculated assuming that the combustion is complete, and that the engine is operated at a stoichiometric air-fuel ratio (AFR). These assumptions are not always met. This is especially true for diesel engines. This article discusses the tests to find out what the average lambda (λ) over the ARTEMIS, WLTC and NEDC driving cycles is and how this affects the result of the emission measurements. Measurements were carried out on a chassis dynamometer equipped with a standard emission measurement system used during the homologation. The λ was calculated using the Brettschneider equation. The dilution ratio DR was also determined by measuring the CO2 concentration in the raw exhaust gas. The CO2-tracer method used for this was modified. The median of the λ for a CI vehicle was 1.23–3.31, which makes the relative percentage difference between the DF and DR (ΔDF) in the range of 28–167%. For a SI vehicle homologated under the WLTP procedure, the median of the λ for the WLTC and ARTEMIS cycles was close to one and ΔDF for most cycles does not exceed 10%. In order to reduce the influence of the error of DF determination on the result of the emission measurement, it is recommended to use exhaust gas sampling systems that allow to determine the actual dilution ratio or to use the lowest possible dilution. The PAS-CVS system seems to be the most promising. [ABSTRACT FROM AUTHOR]

Highlights • Analysis of Oxy-Hydrogen (HHO) use as fuel additive in internal combustion engines. • Energetic investigation of the interactions among engine and auxiliary components. • Innovative definition of HHO nature and of Unchanged Fuel Consumption Limit (UFCL). • Validation of energy needs for HHO production based on literature data. • UFCL evaluation for different engines and operations based on literature data. Abstract The present study aims at assessing, from a theoretical point of view, the feasibility of on-board production and use of Oxy-Hydrogen (HHO) as fuel additive in internal combustion engines. From the available literature, many works deal with the experimental investigation of the benefits achieved with HHO use in both compression and spark ignition engines in terms of brake thermal efficiency improvement and emissions reduction. Nevertheless, a thorough demonstration of the feasibility of HHO on-board production and use has not been performed yet, also due to the unclear nature of the generated HHO mixture. To bridge this gap, a rigorous analysis of the energetic needs related to HHO production through electrolysis, with the internal combustion engine as unique power supply, is here described in details. An innovative assumption is proposed to achieve a generalized representation of HHO mixture and univocally determine the energetic requirements related to its production. A conventional layout is considered to define realistic restrictions for HHO use and fuel savings achievement. Several case studies, based on works available in the literature, are investigated to prove the validity of the proposed analysis and assess the feasibility of the technological approach. [ABSTRACT FROM AUTHOR]

• 1-D engine model with predictive TJI combustion is developed and validated. • Benefits of passive TJI on combustion and efficiency are assessed. • The effect of mixture leaning is assessed through model simulations. • The impact of prechamber geometry on combustion and efficiency is assessed. The increasing concern about Greenhouse Gas (GHG) emissions led the European Union to introduce increasingly stringent limits to the CO 2 from road vehicles, with an impact on the sales of passenger cars. Vehicles equipped with Spark-Ignition (SI) engines became more numerous than those equipped with Compression-Ignition (CI) engines, due to the expensive aftertreatment system needed to comply with the restrictive European emission standards. However, SI engines provide lower efficiency than CI engines, due to the low compression ratio and the operation with a stoichiometric air–fuel ratio. Lean combustion can be a solution to increase SI engines' efficiency. Nevertheless, extremely lean mixtures lead to an increase in Cycle-to-Cycle Variability (CCV). The prechamber ignition concept, also known as Turbulent Jet Ignition (TJI), is an attractive solution for lean combustion, without its drawbacks. There are two ways to implement this concept: active TJI and passive TJI. In active TJI, there is an additional fuel supply system inside the prechamber, while passive TJI operates without additional injection. Therefore, passive TJI offers advantages in terms of simplicity, easy packaging, and low cost. In this work, the effects of passive TJI on combustion and performance are investigated by simulation analyses. Particularly, a 1-D engine model was developed to simulate the TJI combustion and validated against the experimental data. Furthermore, model simulations were carried out to assess how the prechamber geometry, in terms of A/V ratio, affects the jet performance, main chamber combustion, and fuel consumption, for different λ values. The analysis was conducted in a medium-to-high speed and load operating condition, namely 4500 rpm and 13 bar of Indicated Mean Effective Pressure (IMEP), under both stoichiometric and lean mixture. Simulation results demonstrated that the best jet performance and the highest engine efficiency are obtained for medium-to-high values of prechamber volume and large diameters, both in stoichiometric and lean-burn conditions, defining a common optimum prechamber design regardless of the λ level. [ABSTRACT FROM AUTHOR]