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Active prechamber combustion systems for SI engines represent a feasible and effective solution in reducing fuel consumption and pollutant emissions for both marine and ground heavy-duty engines. However, reliable and low-cost numerical approaches need to be developed to support and speed-up their industrial design considering their geometry complexity and the involved multiple flow length scales. This work presents a CFD methodology based on the RANS approach for the simulation of active prechamber spark-ignition engines. To reduce the computational time, the gas exchange process is computed only in the prechamber region to correctly describe the flow and mixture distributions, while the whole cylinder geometry is considered only for the power-cycle (compression, combustion and expansion). Outside the prechamber the in-cylinder flow field at IVC is estimated from the measured swirl ratio.

The present paper describes the results of a research project aimed at studying the impact of nozzle flow number on a Euro5 automotive diesel engine, featuring Closed-Loop Combustion Control. In order to optimize the trade-offs between fuel economy, combustion noise, emissions and power density for the next generation diesel engines, general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle hole size. In this context, three nozzle configurations have been characterized on a 2.0L Euro5 Common Rail Diesel engine, coupling experimental activities performed on multi-cylinder and optical single cylinder engines to analysis on spray bomb and injector test rigs. More in detail, this paper deeply describes the investigation carried out on the multi-cylinder engine, specifically devoted to the combustion evolution and engine performance analysis, varying the injector flow number.

The introduction of new light-duty vehicle emission limits to comply under real driving conditions (RDE) is pushing the diesel engine manufacturers to identify and improve the technologies and strategies for further emission reduction. The latest technology advancements on the after-treatment systems have permitted to achieve very low emission conformity factors over the RDE, and therefore, the biggest challenge of the diesel engine development is maintaining its competitiveness in the trade-off “CO2-system cost” in comparison to other propulsion systems. In this regard, diesel engines can continue to play an important role, in the short-medium term, to enable cost-effective compliance of CO2-fleet emission targets, either in conventional or hybrid propulsion systems configuration. This is especially true for large-size cars, SUVs and light commercial vehicles.

Nowadays, alcoholic fuels gain increased interest as alternative transportation biofuel even in compression ignition engines due to the fact that they contain oxygen and can be produced in a sustainable way. Furthermore, due to their lower CN (Cetane Number) they suit better for premixed combustion applications. Experimental research was conducted on a single cylinder engine provided with modern engine architecture modified for DF (Dual-Fuel) purposes. The authors have investigated the use of ethanol in a DF engine in order to exploit its well-known advantages in premixed combustion mode. The DF approach appears to be a promising solution because it permits flexible control of the premixed fuel fraction regardless from the operating conditions. This improves the exploitation of the ethanol potential according the engine working conditions.

In recent years the research on Diesel engines has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the propulsion electrified future, especially in the European market where 95gCO2/km fleet average and Euro6D RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel-based additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies.

Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on stationary engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of a pre-chamber combustion configuration in a stationary heavy-duty engine for power generation, operating at different loads, air-to-fuel ratios and spark timings.

An integrated numerical-experimental research activity has been carried out, in order to investigate the reliability of a modified, parallel version of KIVA3V, coupled with detailed kinetics, as an additional tool for the analysis of experimental results. In the proposed approach, fixed chemical species included in the reaction mechanism are used as markers for selection of the numerical methods to be used, aiming at exploiting, in every phase of the calculation, the most suitable solver. For validation purposes, pure n-Heptane was chosen as representative fuel model, both in experiments and computations. Calculated values are compared with experimental data collected on a single-cylinder diesel engine fuelled with pure n-heptane, in order to allow the direct use of a reaction mechanism for a single-component fuel.

Research activities in the development of reliable computational models for aftertreatment systems are constantly increasing in the automotive field. These investigations are essential in order to get a complete understanding of the main catalytic processes which clearly have a great impact on tailpipe emissions. In this work, a 1D chemical reaction model to simulate the catalytic activity of a Pd/Rh Three-Way Catalyst (TWC) for a Natural Gas heavy-duty engine is presented. An extensive database of tests carried out with the use of a Synthetic Gas Bench (SGB) has been collected to investigate the methane abatement pathways, linked to the lambda variation and oxide formation on palladium surface. Specific steady-state tests have shown a dynamics of the methane conversion even at fixed λ and temperature conditions, essentially due to the Pd/PdO ratio.