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Alternative fuels, such as natural and bio-gas, are attractive options for reducing greenhouse gas emissions from combustion engines. However, the naturally occurring variation in gas composition poses a challenge and may significantly impact engine performance. The gas composition affects fundamental fuel properties such as flame propagation speed and heat release rate. Deviations from the gas composition for which the engine was calibrated result in changes in the combustion phase, reducing engine efficiency and increasing fuel consumption and emissions. However, the efficiency loss can be limited by estimating the combustion phase and adapting the spark timing, which could be implemented favorably using a closed-loop control approach. In this paper, we evaluate the efficiency loss resulting from varying gas compositions and the benefits of using a closed-loop controller to adapt the spark timing to retain the nominal combustion phase.

In the perspective of a reduction of emissions and a rapid decarbonisation, especially for compression ignition engines, hydrogen plays a decisive role. The dual fuel technology is perfectly suited to the use of hydrogen, a fuel characterized by great energy potential. In fact, replacing, at the same energy content, the fossil fuel with a totally carbon free one, a significant reduction of the greenhouse gases, like carbon dioxide and total hydrocarbon, as well as of the particulate matter can be obtained. The dual fuel with indirect injection of gaseous fuel in the intake manifold, involves the problem of hydrogen autoignition. In order to avoid this difficulty, the optimal conditions for the injection of the incoming mixture into the cylinder were experimentally investigated. All combustion processes are carried out on a research engine with optical access. The engine speed has is set at 1500 rpm, while the EGR valve is deactivated.

Given the spread of natural gas engines in low-term toward decarbonization and the growing interest in gaseous mixtures as well as the use of hydrogen in Heavy-Duty (HD) engines, appropriate strategies are needed to maximize thermal efficiency and achieve near-zero emissions from these propulsor systems. In this context, some phenomena related to real-world driving operations, such as engine cut-off or misfire, can lead to inadequate control of the Air-to-Fuel ratio, key factor for Three-Way Catalyst (TWC) efficiency. Goal of the present research activity is to investigate the performance of a bio-methane-fueled HD engine and its Aftertreatment System (ATS), consisting of a Three-Way Catalyst, at different Air-to-Fuel ratio. An experimental test bench characterization, in different operating conditions of the engine workplan, was carried out to evaluate the catalyst reactivity to a defined pattern of the Air-to-Fuel ratio.

Electrification of transport, together with the decarbonization of energy production are suggested by the European Union for the future quality of air. However, in the medium period, propulsion systems will continue to dominate urban mobility, making mandatory the retrofitting of thermal engines by applying combustion modes able to reduce NOx and PM emissions while maintaining engine performances. Low Temperature Combustion (LTC) is an attractive process to meet this target. This mode relies on premixed mixture and fuel lean in-cylinder charge whatever the fuel type: from conventional through alternative fuels with a minimum carbon footprint. This combustion mode has been subject of numerous modelling approaches in the engine research community. This study provides a theoretical comparative analysis between multi-zone (MZ) and Transported probability density function (TPDF) models applied to LTC combustion process.

A possible environmental assessment of sustainable vehicular transport is based on a comparative analysis through the LCA Life Cycle Analysis methodology of the entire vehicle’s life cycle. For this purpose, it could contribute to the choices of political decision-makers and investors in the sector of large infrastructure and industrial works. Therefore, the LCA activity is of fundamental importance for the estimation and analysis of the economic and social impacts through the comparative analysis of technological solutions in scenarios of “accelerated technological evolution” and/or “sustainable mobility”. The study could be designed for different vehicle segments to evaluate their efficiency and overall environmental sustainability also related to current social and political scenarios. Couples with electric and internal combustion vehicles of the same market segment and category may be compared.

In order to reduce fuel consumption and polluting emissions from engines, alternative fuels such as hydrogen could play an important role towards carbon neutrality. Moreover, dual-fuel (DF) technology has the potential to offer significant improvements in carbon dioxide emissions for transportation and energy sectors. The dual fuel concept (natural gas/diesel or hydrogen/diesel) represents a possible solution to reduce emissions from diesel engines by using low-carbon or carbon-free gaseous fuels as an alternative fuel. Moreover, DF combustion is a possible retrofit solution to current diesel engines by installing a PFI injector in the intake manifold while diesel is injected directly into the cylinder to ignite the premixed mixture. In the present study, dual fuel operation has been investigated in a single cylinder research engine.

The forthcoming introduction of the EURO VII regulation requires urgent strategies and solutions for the reduction of sub-23 nm particle emissions. Although they have been historically considered as particulate matter-free, the high interest for Natural Gas (NG) Heavy-Duty engines in the transport sector, demands their compliance with the new proposed regulations. In order to obtain high conversion of gas pollutants and a strong abatement of the emitted particles, the use of Particle Filters in NG aftertreatment (CPF) in conjunction with the Three-Way Catalyst (TWC) may represent an attractive and feasible solution. Performances of a cordierite filter were explored through an extensive experimental campaign both in Steady-State conditions and during transient engine maneuvers that involved a whole analysis of the emitted particles in terms of number and mass.

Hydrogen Internal Combustion Engines (H2-ICEs) are subject to increased attention thanks to their extremely low criteria pollutant emission and near-zero CO2 tailpipe emissions. However, to further minimize exhaust emissions and increase the efficiency of a H2-ICE, it is important to carefully control the relative air-fuel ratio of operation, i.e. Lambda (λ), which will lead in turn to an optimal combustion process. The precise λ control mainly relies upon the methodology to calculate λ on board of the engine, where the availability of reliable sensors specifically-developed for hydrogen combustion is currently limited. In this article, a comparative analysis of different methodologies for the calculation of λ is performed, comparing four methodologies: exhaust gas analysis through a Spindt-Brettschneider approach (λEMI), raw Universal Exhaust Gas Oxygen (λR-UEGO), processed Universal Exhaust Gas Oxygen (λP-UEGO) and speed-density (λSD) outputs.

The application of an alternative fuel such as hydrogen to internal combustion engines is proving to be an effective and flexible solution for reducing fuel consumption and polluting emissions from engines. An easy to use and immediate application solution is the dual fuel (DF) technology. It has the potential to offer significant improvements in carbon dioxide emissions from light compression ignition engines. The dual fuel concept (natural gas / diesel or hydrogen / diesel) represents a possible solution to reduce emissions from diesel engines by using low-carbon or carbon-free gaseous fuels as an alternative fuel. Moreover, DF combustion is a possible retrofit solution to current diesel engines by installing a PFI injector in the intake manifold while diesel is injected directly into the cylinder to ignite the premixed mixture. In the present study, dual fuel operation has been investigated in a single cylinder research engine.

Nowadays, the stricter regulations in terms of emissions have limited the use of diesel engines on urban roads. On the contrary, for marine and off-road applications the diesel engine still represents the most feasible solution for work production. In the last decades, dual fuel operation with methane supply has been widely investigated. Starting from previous studies on a research engine, where diesel-methane dual fuel combustion has been deepened both experimentally and numerically with the aid of a CFD code, the authors implemented and tested a kinetic mechanism. It is obtained from the combination of the well-established GRIMECH 3.0 and a detailed scheme for a diesel surrogate oxidation. Moreover, the Autoignition-Induced Flame Propagation model, included in the ANSYS Forte® software, is applied because it can be considered the most appropriate model to describe dual fuel combustion.

Methane supply in diesel engines operating in dual fuel mode has demonstrated to be effective for the reduction of particulate matter and nitric oxides emissions from this type of engine. In particular, methane is injected into the intake manifold to form a premixed charge with air, while a reduced amount of diesel oil is still directly injected to ignite the mixture inside the cylinder. As a matter of fact, the liquid fuel burns following the usual diffusive combustion, so activating the gaseous fuel oxidation in a premixed flame. Clearly, the whole combustion process appears to be more complex to be described in a CFD simulation, mainly because it is not always possible to select in the 3-dimensional codes a different combustion model for each fuel and, also, because other issues arise from the interaction of the two fuels.

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.

This paper investigates the FPGA resources for the implementation of in-cycle closed-loop combustion control algorithms. Closed-loop combustion control obtains feedback from fast in-cylinder pressure measurements for accurate and reliable information about the combustion progress, synchronized with the flywheel encoder. In-cycle combustion control requires accurate and fast computations for their real-time execution. A compromise between accuracy and computation complexity must be selected for an effective combustion control. The requirements on the signal processing (evaluation rate and digital resolution) are investigated. A common practice for the combustion supervision is to monitor the heat release rate. For its calculation, different methods for the computation of the cylinder volume and heat capacity ratio are compared. Combustion feedback requires of virtual sensors for the misfire detection, burnt fuel mass and pressure prediction.

A wider use of biofuels in internal combustion engines could reduce the emissions of pollutants and greenhouse gases from the transport sector. In particular, due to stringent emission regulatory programs, compression ignition engine requires interventions aimed at reducing their polluting emissions. Ethanol, a low carbon fuel generally produced from biomass, is a promising alternative fuel applicable in compression ignition engines to reduce CO2 and soot emissions. In this paper, the application of a dual fuel diesel-ethanol configuration in a light-duty compression ignition engine has been numerically investigated. Ethanol is injected into the intake port, while diesel fuel is directly injected into the combustion chamber of the analyzed engine. CFD simulations have been carried out by means of the AVL Fire 3-D code. The operation at given engine load and speed has been simulated considering different diesel injection timings.

Growing concerns about the emissions of internal combustion engines have forced the adoption of aftertreatment devices to reduce the adverse impact of diesel engines on health and environment. Diesel particulate filters are considered as an effective means to reduce the particle emissions and comply with the regulations. Research activity in this field focuses on filter configuration, materials and aging, on understanding the variation of soot layer properties during time, on defining of the optimal strategy of DPF management for on-board control applications. A model was implemented in order to simulate the filtration and regeneration processes of a wall-flow particulate filter, taking into account the emission characteristic of the engine, whose architecture and operating conditions deeply affect the size distribution of soot particles.

Pilot injections are normally used for the reduction of diesel engine emissions and combustion noise. Nonetheless, with a penalty on the indicated thermal efficiency. The cost is reduced by the minimization of the pilot mass, which on its counterpart increases the risk of pilot misfire. Pilot misfire can have a higher penalty on the indicated efficiency if it is not compensated adequately. This paper investigates how in-cycle closed-loop combustion control techniques can reduce the effects of pilot misfire events. By closed-loop combustion control, pilot misfire can be detected and counteracted in-cycle. Two injection strategies are investigated. The first is the control of the main injection, the second includes an additional second pilot injection. Based on the in-cycle misfire diagnose, two architectures are investigated. The first uses a cycle-to-cycle controller to set the main injection under each scenario.

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.

This study investigates particulate matter (PM) and regulated emissions from renewable rapeseed oil methyl ester (RME) biodiesel in pure and blended forms and contrasts that to conventional diesel fuel. Environmental and health concerns are the major motivation for combustion engines research, especially finding sustainable alternatives to fossil fuels and reducing diesel PM emissions. Fatty acid methyl esters (FAME), including RME, are renewable fuels commonly used from low level blends with diesel to full substitution. They strongly reduce the net carbon dioxide emissions. It is largely unknown how the emissions and characteristics of PM get altered by the combined effect of adding biodiesel to diesel and implementing modern engine concepts that reduce nitrogen oxides (NOx) emissions by exhaust gas recirculation (EGR).

The use of gaseous fuels in internal combustion engines is increasing, due to several reasons, first of all their low environmental impact, large availability and low cost. Nevertheless, the need to reduce emissions also from gas engines is an important aspect to be considered in order to comply with future engine emissions regulations. In this scenario, an extensive experimental activity was performed to fully characterize an heavy duty spark ignition engine, under development for Euro VI compliance and designed to run with gaseous fuels. Two separate sets of experiments were carried out, in order to analyze the engine behavior when burning LPG and CNG, respectively. To this aim, the engine was installed on a dynamic test bench, accurately instrumented to characterize the combustion evolution, performance and exhaust pollutant emissions, along the World Harmonized Transient Cycle (WHTC), the new European driving homologation cycle.

The current legislation does not take into account the limitation of sub 23 nm particles from engine. Nevertheless, the Common Rail Diesel engine emits a large number of nanoparticle, solid and volatiles, that are very dangerous for human health. In this contest, the challenge of the “dieper EU project” is to apply advanced technologies for exhaust after-treatment to existing diesel engines and to optimize the characteristics of a new generation of engines with regards to emissions, fuel consumption and drivability. Aim of the present paper is to provide useful information for the development of the after-treatment system that will have to fulfill Euro6 further steps. In order to characterize the chemical and physical nature of Particulate Matter emitted from Euro 6b Medium Duty diesel engine, the pollutants were collected and analyzed: from engine-out, downstream of the particulate filter (DPF), and at the exit of a selective catalytic reactor (SCR).