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UV-visible digital imaging and 2D chemiluminescence were applied on a single cylinder optically accessible compression ignition engine to investigate the effect of different alcohol/diesel fuel blends on the combustion mechanism. The growing request for greenhouse gas emission reduction imposes to consider the use of alternative fuels with the aim of both partially replacing the diesel fuel and reducing the fossil fuel consumption. To this purpose, the use of ABE (Acetone-Butanol-Ethanol) fermentation could represent an effective solution. Even if the different properties of alcohols compared to Diesel fuel limit the maximum blend concentration, low blend volume fractions can be used for improving combustion efficiency and exhaust emissions. The main objective of this study was to investigate the effects of the different fuel properties on the combustion evolution within the combustion chamber of a prototype optically accessible compression ignition engine.

The diesel particulate filters (DPF) are considered the most robust technologies for particle emission reduction both in terms of mass and number. On the other hand, the increase of the backpressure in the exhaust system due to the accumulation of the particles in the filter walls leads to an increase of the engine fuel consumption and engine power reduction. To limit the filter loading, and the backpressure, a periodical regeneration is needed. Because of the growing interest about particle emission both in terms of mass, number and size, it appears important to monitor the evolution of the particle mass and number concentrations and size distribution during the regeneration of the DPFs. For this matter, in the presented work the regeneration of a catalyzed filter was fully analyzed. Particular attention was dedicated to the dynamic evolution both of the thermodynamic parameters and particle emissions.

Nowadays, alcohol fuels are of increasing interest as alternative transportation biofuels even in compression ignition engines because they are oxygenated and producible in a sustainable way. In this paper, the experimental research activity was conducted on a single cylinder research engine provided with a modern architecture and properly modified in a dual-fuel (DF) configuration. Looking at ethanol the as one of the future environmental friendly biofuels experimental campaign was aimed to evaluate in detail the effect of the use of the ethanol as port injected fuel in diesel engine on the size, morphology, reactivity and chemical features of the exhaust emitted soot particles. The engine tests were chosen properly in order to represent actual working conditions of an automotive light-duty diesel engine. A proper engine Dual-Fuel calibration was set-up respecting prefixed limits on in-cylinder peak firing pressure, cylinder pressure rise, fuel efficiency and gaseous emissions.

In the present activity, dual fuel operation was investigated in a single cylinder research engine. Methane was injected in the intake manifold while the diesel was delivered via the standard injector directly into the engine. The aim is to study the effect of increasing methane concentration at constant injected diesel amount on both pollutant emissions and combustion evolution in an optically accessible engine. Emissions are in line with those previously published by other authors, it is noted no PM and constant NOx emissions. Moreover, a decrease of the brake specific CO emissions and an increase of the brake specific THC for the operating condition with the highest premixed ratio was detected. THC was mainly constituted by methane unburned hydrocarbons. Combustion resulted more or less stable. Moreover, via both UV-VIS spectroscopy and digital imaging, the spatial distribution of several species involved in the combustion process was analyzed.

Recently, it has been worth pointing out the relevance of alternative fuels in the improvement of air quality conditions and in the mitigation of global warming. In order to deal with these demands, in recent studies, it has been considered a great variety of alternative fuels. It goes without saying that the alternative fuels industry needs the best of the efficiency with a moderate layout. From this perspective, Liquefied Petroleum Gas (LPG) could represent a valid option, although it is not a renewable fuel. In terms of polluting emissions, the LPG can reduce nitrous oxides and smoke concentrations in the air, a capability that has a relevant importance for the modern pollution legislation. LPG is well known as an alternative fuel for Spark Ignition (SI) engines and, more recently, LPG systems have also been introduced in the Compression Ignition (CI) engines in dual-fuel configuration.

The present work relates to the investigation of the basic oxidation characteristics of iron and aluminium nanoparticles as well as the feasibility of their combustion under both Internal Combustion Engine (ICE)-like and real engine conditions. Based on a series of proof-of-concept experiments, combustion was found to be feasible taking place in a controllable way and bearing similarities to the respective case of conventional fuels. These studies were complimented by relevant in-situ and ex-situ/post-analysis, in order to elaborate the fundamental phenomena occurring during combustion as well as the extent and ‘quality’ of the process. The oxidation mechanisms of the two metallic fuels appear different and -as expected- the energy release during combustion of aluminium is significantly higher than that released in the case of iron.

This paper deals with the combustion characteristics and exhaust emissions of a diesel engine fuelled with conventional diesel fuel and a biodiesel blend, in particular a 20% v/v concentration of rapeseed methyl ester (RME) mixed with diesel fuel. The investigation was carried out on a prototype three-cylinder engine with 1000 cc of displacement for quadricycle applications. The engine is equipped with a direct common-rail injection system that reaches a maximum pressure of 1400 bar. The engine was designed to comply with Euro 4 and BS IV exhaust emission regulations without a diesel particulate filter. Both in-cylinder pressure and rate of heat release traces were analyzed at different engine speeds and loads. Gaseous emissions were measured at the exhaust. A smoke meter was used to measure the particulate matter concentration. The sizing and the counting of the particles were performed by means of an engine exhaust particle sizer spectrometer.

In recent years the use of alternative fuels for internal combustion engines has had a strong push coming from both technical and economic-environmental aspects. Among these, gaseous fuels such as liquefied petroleum gas and natural gas have occupied a segment no longer negligible in the automotive industry, thanks to their adaptability, anti-knock capacity, lower toxicity of pollutants, reduced CO2 emissions and cost effectiveness. On the other hand, diesel engines still represent the reference category among the internal combustion engines in terms of fuel consumptions. The possibility offered by the dual fuel systems, to combine the efficiency and performance of a diesel engine with the environmental advantages of gaseous fuels, has been long investigated. However the simple replacement of diesel fuel with natural gas does not allow to optimize the performance of the engine due to the high THC emissions particularly at lower loads.

In this paper, a Low Temperature Premixed Combustion (LTPC) was investigated employing a four cylinder D.I. common rail Diesel engine, used for passenger cars on the European market. Experiments were carried out setting the engine speed at 2500 rpm with a fuel amount of 26 mg/str to realize an operating condition close to the point of NEDC at 0.8 MPa of BMEP. The experimental approach was the management of the start of injection, injection pressure and EGR rates as a method to control NOx and soot production. The investigation was first carried out testing engine performances and emissions as set from the commercial engine map. Afterward, engine tests were carried out exploring performances, gaseous and smoke emissions at late start of combustion [10 to 17.5 cad ATDC], injection pressures from 80 to 120 MPa and EGR rates up to 50%.

The Real Driving Emission (RDE) procedure will measure the pollutants, such as NOx, emitted by cars while driven on the road. RDE will not replace laboratory tests, such as the current WLTP but it will be added to them. RDE is complementary to the laboratory-based procedure to check the pollutant emissions level of a light-duty vehicle in real driving conditions. This means that the car will be driven on a real road according to random acceleration and deceleration patterns conditioned by traffic flow. So, the procedure will ensure that cars deliver real emissions over on-road and so the currently observed differences between emissions measured in the laboratory and those measured on road under real-world conditions, will be reduced. However, the identification of a path on the road to check the test conditions of RDE is not easy and hardly repeatable.

The EU emission standards for new rail Diesel engines are becoming even more stringent. EGR and SCR technologies can both be used to reduce NOx emissions; however, the use of EGR is usually accompanied by an increase in PM emissions and may require a DPF. On the other hand, the use of SCR requires on-board storage of urea. Thus, it is necessary to study these trade-offs in order to understand how these technologies can best be used in rail applications to meet new emission standards. The present study assesses the application of these technologies in Diesel railcars on a quantitative basis using one and three dimensional numerical simulation tools. In particular, the study considers a 560 kW railcar engine with the use of either EGR or SCR based solutions for NOx reduction. The NOx and PM emissions performances are evaluated over the C1 homologation cycle.

In the last ten years, the number of natural gas vehicles worldwide has grown rapidly with the biggest contribution coming from the Asia-Pacific and Latin America regions. As natural gas is the cleanest fossil fuel, the exhaust emissions from natural gas spark ignition vehicles are lower than those of gasoline powered vehicles. Moreover, natural gas is less affected by price fluctuations and its resources are more evenly widespread over the globe than to oil. However, as natural gas vehicles are usually bi-fuel gasoline and natural gas, the excellent knock resistant characteristics of natural gas cannot be completely exploited. This paper shows the results of an experimental activity performed on a passenger car fuelled alternatively by gasoline and compressed natural gas (CNG). The vehicle has been tested on a chassis dynamometer over standard (NEDC) and real driving cycles (Artemis CADC), allowing to investigate a wide range of operating conditions.

The use of direct injection (DI) engines allows a more precise control of the air-fuel ratio, an improvement of fuel economy, and a reduction of exhaust emissions thanks to the ultra-lean combustion due to the charge stratification. These effects can be partially obtained also with an optimized Air Direct Injection that permits to increase the turbulence at low speed and load increasing the combustion stability especially in lean condition. In this paper, a gasoline PFI (named G-PFI), gasoline PFI-methane DI dual fuel (named G-MDF) lean combustion were analyzed. The G-MDF configuration was also compared with a gasoline PFI - air DI (named G-A) configuration in order to distinguish the chemical effect of methane from the direct injection physical effect. The tests were carried out in a small displacement PFI/DI SI engine. The experimental investigation was carried out in a transparent small single-cylinder, spark ignition four-stroke engine.

A plasma ignition system was tested in a GDI engine with the target of combustion efficiency improvement without modifying engine configuration. The plasma was generated by spark discharge and successively sustained to enhance its duration up to 4 ms. The innovative ignition system was tested in an optically accessible single-cylinder DISI engine to investigate the effects of plasma on kernel stability and flame front propagation under low loads and lean mixture (λ≅1.3). The engine was equipped with the head of a commercial turbocharged engine with similar geometrical specifications (bore, stroke, compression ratio). All experiments were performed at 2000 rpm and 100 bar injection pressure. UV-visible 2D chemiluminescence was applied in order to study the flame front inception and propagation with particular interest in the early combustion stages. A bandpass filter allowed selecting luminous signal due to OH radicals.

In the present paper, results of an experimental investigation carried out in a modern Diesel engine running at different operating conditions and fuelled with commercial diesel and n-butanol-diesel blend are reported. The investigation was focused on the management of injection strategy and combustion timing (CA50) exploring the effect of intake oxygen concentration and boost pressure on engine out emissions. The aim of the paper was to compare, with respect to commercial diesel, the effects of a fuel blend with a lower cetane number and higher volatility on performance and engine out emissions. Engine tests, with baseline diesel and a blend made by the baseline low sulphur diesel with 20% in volume of n-butanol (B20), were performed comparing engine out gaseous, smoke emissions and combustion efficiency. The investigation was performed on a turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system.

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.

Diesel particulate filter (DPF) is the most effective emission control device for reducing particle emissions (both mass, PM, and number, PN) from diesel engines, however many studies reported elevated emissions of nanoparticles (<50 nm) during its regeneration. In this paper the results of an extensive literature survey is presented. During DPF active regeneration, most of the literature studies showed an increase in the number of the emitted nanoparticles of about 2-3 orders of magnitude compared to the normal operating conditions. Many factors could influence their amount, size distribution, chemical-physical nature (volatiles, semi-volatiles, solid) and the duration of the regenerative event: i.e. DPF load and thermodynamic conditions, lube and fuel sulfur content, engine operative conditions, PN sampling and measurement methodologies.

The present paper describes the results of a research activity aimed at studying the potential offered by the use of Hydrocracked fossil oil (HCK) and Hydrotreated Vegetable Oil (HVO) blends as premium fuels for next generation diesel engines. Five fuels have been tested in a light duty four cylinder diesel engine, Euro 5 version, equipped with closed loop control of the combustion. The set of fuels comprises four experimental fuels specifically formulated by blending high cetane HVO and HCK streams and oneEN590-compliant commercial diesel fuel representative of the current market fuel quality. A well consolidated procedure has been carried out to estimate, for the tested fuels, the New European Driving Cycle (NEDC) vehicle performance by means of the specific emissions at steady-state engine operating points.

Idle Speed Control plays a crucial role to reduce fuel consumption that turns in both a direct economic benefit for customers and CO\d reduction particularly important to tackle the progressive global environmental warming. Typically, control strategies available in the automotive literature solve the idle speed control problem acting both on the throttle position and the spark advance, while the Air-Fuel Ratio (AFR), that strongly affects the indicated engine torque, is kept at the stoichiometric value for the sake of emission reduction. Gasoline Direct Injection (GDI) engines, working lean and equipped with proper mechanisms to reduce NOx emissions, overcome this limitation allowing the AFR to be used for the idle speed regulation.

Biofuel usage is increasingly expanding thanks to its significant contribution to a well-to-wheel (WTW) reduction of greenhouse gas (GHG) emissions. In addition, stringent emission standards make mandatory the use of Diesel Particulate Filter (DPF) for the particulate emissions control. The different physical properties and chemical composition of biofuels impact the overall engine behaviour. In particular, the PM emissions and the related DPF regeneration strategy are clearly affected by biofuel usage due mainly to its higher oxygen content and lower low heating value (LHV). More specifically, the PM emissions and the related DPF regeneration strategy are clearly affected by biofuel usage due mainly to its higher oxygen content and lower low heating value, respectively. The particle emissions, in fact, are lower mainly because of the higher oxygen content. Subsequently less frequent regenerations are required.