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The use of oxygenated and renewable fuels is nowadays a widespread means to reduce regulated pollutant emissions produced by internal combustion engines, as well as to reduce the greenhouse impact of transportation. Besides PM, NOx and HC emissions, also the size distribution of particles emitted at the engine exhaust represent meaningful information, considering its adverse effects on the environment and human health. In this work, the results of a comprehensive investigation on the combustion characteristics and the exhaust emissions of a GDI high performance engine, fuelled with pure bio-ethanol and European gasoline, are shown. The engine is a 4-cylinder, 4-stroke, 1750 cm₃ displacement, and turbocharged. The engine was operated at different speed/load conditions and two fuel injection strategies were investigated: homogeneous charge mode and stratified charge mode.

Spectral flame emissivity and absorption measurements with high temporal and spatial resolution were performed in an optically accessible high-swirl divided-chamber Diesel system. Simultaneous determination of soot temperature, soot volume fraction and the OH radical concentration were made from the start to the end of the combustion in 153 locations equally distributed in the chamber. The engine was run at 2000 rpm and at fixed air-fuel ratio realizing 200 consecutive combustion cycles. To visualize the spatial and temporal spray and flame evolution, direct high-speed photographic sequences were taken at 8000 frames/s. The photographic sequences showed that the spray is strongly distorted and mixed by very high swirl resulting in a well premixed region where the combustion starts. The OH radicals were detected in the fuel reaction zone. Moreover OH concentration and soot volume fraction are well correlated with soot temperature.

Direct injection spark ignition engines represent an effective technology to achieve the goal of carbon dioxide emission reduction. Further reduction of the carbon footprint can be achieved by using carbon-neutral fuels. Oxygenated alcohols are well consolidated fuels for spark ignition engines providing also the advantages of knock resistance and low soot tendency production. Methanol and ethanol are possible candidates as alternative fuels to gasoline due to their similar properties. In this study a blend at 25 % v/v of ethanol in gasoline (E25) and a blend with 80% gasoline, 5 % v/v ethanol and 15% v/v of methanol (GEM) were tested. These blends were considered since E25 is already available at fuel pump in some countries. The GEM blend, instead, could represent a valid alternative in the next future. Experiments were carried out on a high performance, turbocharged 1.8 L direct injection spark ignition engine over the Worldwide Harmonized Light Vehicles Test Cycle.

In view of the new emission regulations seeking to lower the particle cut-off size down to the current 23 nm, an extensive comprehension on the nature of sub-23 nm particles is crucial. In this regard, a new challenge lies ahead considering an even more massive use of biofuels. The objective of this research study was to characterize the sub-23 nm particles and to evaluate their volatile organic fraction (VOF) from a high performance, 1.8 L gasoline direct injection (GDI) engine under the Worldwide harmonized Light vehicles Test Cycle (WLTC). Particle emissions were measured through an Engine Exhaust Particle Sizer (EEPS) capable of particle sizing and counting in the range 5.6 - 560 nm. The sampling and conditioning were performed by both a single diluter and the Dekati Engine Exhaust Diluter (DEED) a Particle Measurement Programme (PMP) compliant sample conditioning system.

Nowadays, the regulation regards only the particles larger than 23 nm. The attention is shifting towards the sub-23 nm particles because of their large presence at the exhaust of the modern engines and their negative impact on human health. The main challenge of the regulation of these particles is the definition of a proper procedure for their measure. The nature of the sub-23 nm particles is not well understood, and their measure is strongly affected by the sampling conditions leading to not reliable measure. The aim of this paper is to provide information on the emissions of sub-23 nm particles from GDI vehicles/engines. At the same time, the presence of volatiles, which mainly contribute to the formation of sub-23 nm particles, was evaluated and the effect of sampling conditions was investigated. The analysis was performed on a 1.8L GDI powered vehicle, widely used both in North America and Europe, and a 4-cylinder GDI engine, whose features are similar to those of the vehicle.

In order to meet the increasingly strict emission regulations, several solutions for NOx and PM emissions reduction have been studied. Exhaust gas recirculation (EGR) technology has become one of the more used methods to accomplish the NOx emissions reduction. However, actual control strategies do not consider, in the definition of optimal EGR, its effect on particle size and density. These latter have a great importance both for the optimal functioning of after-treatment systems, but also for the adverse effects that small particles have on human health. Epidemiological studies, in fact, highlighted that the toxicity of particulate particles increases as the particle size decreases. The aim of this paper is to present a Neural Network model able to provide real time information about the characteristics of exhaust particles emitted by a Diesel engine.

This paper deals with the combustion behavior and exhaust emissions of a small compression ignition engine modified to operate in diesel/methane dual fuel mode. The engine is a three-cylinder, 1028 cm3 of displacement, equipped with a common rail injection system. The engine is provided with the production diesel oxidation catalyst. Intake manifold was modified in order to set up a gas injector managed by an external control unit. Experiments were carried out at different engine speeds and loads. For each engine operating condition, the majority of the total load was supplied by methane while a small percentage of the load was realized using diesel fuel; the latter was necessary to ignite the premixed charge of gaseous fuel. Thermodynamical analysis of the combustion phase was performed by in-cylinder pressure signal. Gas emissions and particulate matter were measured at the exhaust by commercial instruments.

This paper reports the results of an experimental investigation on the combustion characteristics and exhaust particulate emissions of a GDI high performance engine, fuelled with blends of bio-ethanol and European gasoline fuel. The engine is a 4-cylinder, 4-stroke, 1750 cm₃ displacement, and turbocharged. The engine was operated at fixed speed and load, namely 1500 rpm and 110 Nm, and fuelled with gasoline (E0), ethanol (E100) and two blends 50% v/v (E50) and 85% v/v (E85) of ethanol in gasoline. Two fuel injection strategies were investigated: homogeneous charge and stratified charge combustion mode. The study mainly focuses on the effects of fuel injection strategy and ethanol upon the emissions of particulate matter (PM), in terms of mass, number concentration and size distribution.

Fuel depletion as well as the growing concerns on environmental issues prompt to the use of more eco-friendly fuels. The compressed natural gas (CNG) is considered one of the most promising alternative fuel for engine applications because of the lower emissions. Nevertheless, recent studies highlighted the presence of ultrafine particle emissions at the exhaust of CNG engines. The present study aims to investigate the effect of CNG on particle formation and emissions when it was direct injected and when it was dual fueled with gasoline. In this latter case, the CNG was direct injected and the gasoline port fuel injected. The study was carried out on a transparent single cylinder SI engine in order to investigate the in-cylinder process by real time non-intrusive diagnostics. In-cylinder 2D chemiluminescence measurements from UV to visible were carried out.

This study was conducted to determine the effects of the fouling process on the piezoelectric injectors in a transparent common-rail diesel engine. Piezoelectric injectors are characterized by a ceramic actuator that can dilate or retract when it receives a pulse of current. The piezo element controls a valve, which creates an imbalance in the pressure that is exerted at each end of the needle, causing the needle rising or closing. Two same model injectors were tested; one was new and the other one was fouled on a vehicle. The aim of the experimental investigation was to evaluate the performance of a new and a fouled piezoelectric injector in terms of injection and flame evolution. It was evaluated how the nozzle carbon deposits affect the injection quantity and combustion. The experimental apparatus was a single-cylinder research engine equipped with a Euro 5 multi-cylinder head. A second-generation common rail injection system and 6-hole piezoelectric injectors were used too.

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.

In the urban area the internal combustion engines are the main source of CO₂, NO and particulate matter (PM) emissions. The reduction of these emissions is no more an option, but a necessity highlighted by the even stricter emission standards. In the last years, even more attention was paid to the alternative fuels. They allow both reducing the fuel consumption and the pollutant emissions. With regards to the gaseous fuels, methane is considered one of the most interesting in terms of engine application. It represents an immediate advantage over other hydrocarbon fuels because of the lower C/H ratio. In this paper the effect of the methane on the combustion process, the pollutant emissions and the engine performance was analyzed. The measurements were carried out in an optically accessible single-cylinder, Port Fuel Injection, four-stroke SI engine equipped with the cylinder head of a commercial 250 cc motorcycles engine and fuelled both with gasoline and methane.

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.

Hybrid electric vehicles are a suitable solution for the transition from fossil fuels-based transportation to electric mobility. They have the benefits of zero-emissions operation when only the electric engine is used preventing the typical range anxiety of full-electric vehicles. Also, they can have a low battery pack capacity and weight thanks to the continuous recharge from the internal combustion engine that becomes the only responsible for exhaust emissions. A practical solution to limit the combustion engine emissions is represented by the range extender configuration, where the engine works at a fixed operating point with the highest efficiency serving uniquely as a battery charger. In the face of the current world situation and future changes, research for alternative energy sources is crucial. Hydrogen can be used as an alternative fuel for common internal combustion engines; moreover, it has the great advantage of high efficiency (about 44%).

Improvement of performance and emission of future internal combustion engine for passenger cars is mandatory during the transition period toward their substitution with electric propulsion systems. In middle time, direct injection spark ignition (DISI) engines could offer a good compromise between fuel economy and exhaust emissions. However, abnormal combustion and particularly knock and super-knock are some of the most important obstacles to the improvement of SI engines efficiency. Although knock has been studied for many years and its basic characteristics are clear, phenomena involved in its occurrence are very complex and are still worth of investigation. In particular, the definition of an absolute knock intensity and the precise determination of the knock onset are arduous and many indexes and methodologies has been proposed. In this work, most used methods for knock onset detection from in- cylinder pressure signal have been considered.

The growing concerns over the pollutant emissions as well as the depletion of fossil fuel led to the research of advanced combustion mode and alternative fuels for the reduction both of fuel consumption and exhaust emissions. The dual-fuel injection system can be used to improve the engine performance and reduce the fossil fuel consumption performing simultaneously a direct-injection (DI) and a port-fuel-injection (PFI) of different fuels. Ethanol is one of the most promising alternative fuels for SI engines. It offers high anti-knock quality because of the high octane number; moreover, being an oxygenated fuel is very effective in particle emissions reduction. On the other hand, it is characterized by lower energy density mainly because of the low lower heating value (LHV). The aim of the paper is the investigation of the ethanol-gasoline dual fuel combustion on engine performance and emissions.

The improvement in engines efficiency and reduction of emissions is the permanent aim of engine industry in order to meet European standards regulation. To optimize small internal combustion engines it is necessary to improve the basic knowledge of thermo-fluid dynamic phenomena occurring during the combustion. This paper describes the combustion process in an optically accessible two-stroke spark-ignition engine used in a commercial 43 cm3 chainsaw. Two different feeding systems were tested: standard and CWI one. The engine head was modified in order to allow the visualization of the combustion using endoscopic system coupled with a high spatial resolution ICCD camera. Flame front propagation was evaluated through an image processing procedure. The image visualization and chemiluminence allowed to follow the combustion process from the spark ignition to the exhaust phase at high engine speed. All the optical data were correlated with engine parameters and exhaust emissions.

Non-intrusive measurements were carried out in an optical spark ignition GDI engine in order to characterize the chemical and physical processes involved using gasoline and bio-ethanol fuel. In particular, an optical 4 strokes small single cylinder engine for two wheel vehicles was used. It was equipped with an elongated piston with a wide sapphire window in the head and quartz cylinder. Exhaust emissions and engine performances were evaluated during the imaging and spectral measurements in order to investigate the spray characteristics and flame propagation with high spatial and temporal resolution. Several engine conditions based on homogeneous charge mixture conditions were investigated considering the effect of injection pressure and ethanol fuel too. The simultaneous use of the high injection pressure and bio-ethanol showed to be a valid answer to reduction of pollutants without worsening the performances.

This paper aims to correlate the in-cylinder soot formation and the exhaust particle emissions for different methods of gasoline/ethanol fueling in spark ignition engine. In particular, the engine was fueled with gasoline and ethanol separately and not, in this latter case both blended (E30) and dual fueled (EDF). For E30 the bend was direct injected and for EDF, the ethanol was injected in the combustion chamber and the gasoline into the intake duct. For both the injection configurations, the same percentage of ethanol in gasoline was supplied: 30%v/v. The measurements were carried out at 2000 and 4000 rpm, under full load, and stoichiometric condition, in small single cylinder optical engine. 2D-digital imaging was performed to follow the combustion process with a high spatial and temporal resolution through a full-bore optical piston. The two-color pyrometry was applied for the analysis of the in cylinder soot formation in the combustion chamber.

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.