Search Results

New internal combustion engines (ICE) are characterized by increasing maximum efficiency, thanks to the adoption of strategies like Atkinson cycle, downsizing, cylinder deactivation, waste heat recovery and so on. However, the best performance is confined to a limited portion of the engine map. Moreover, electric driving in urban areas is an increasingly pressing request, but battery electric vehicles use cannot be easily spread, due to limited vehicle autonomy and recharging issues. Therefore, hybrid propulsion systems are under development, in order to reduce vehicle fuel consumption, by decoupling the ICE running from road load, as well as to permit energy recovery and electric driving. This paper analyses a new-patented solution for power split hybrid propulsion system with gearbox. The system comprises an auxiliary power unit, adapted to store and/or release energy, and a planetary gear set, which is interposed between the ICE and the gearbox.

The stringent worldwide exhaust emission legislations for CO2 and pollutants require significant efforts to increase both the combustion efficiency and the emission quality of internal combustion engines. With this aim, several solutions are continuously developed to improve the combustion efficiency of spark ignition engines. Among the various solutions, EGR represents a well-established technology to improve the gasoline engine performance and the nitrogen-oxides emissions. This work presents the results of an experimental investigation on the effects of the EGR technique on combustion evolution, knock tendency, performance and emissions of a small-size turbocharged PFI SI engine, equipped with an external cooled EGR system. Measurements are carried out at different engine speeds, on a wide range of loads and EGR levels. The standard engine calibration is applied at the reference test conditions.

Diesel will continue to be an indispensable energy carrier for the car fleet CO2 emission targets in the short-term. This is particularly relevant for heavy-duty vehicles as for mid-size cars and SUVs. Looking at the latest technology achievements on the after-treatment systems, it can be stated that the concerning about the NOx emission gap between homologation test and real road use is basically solved, while the future challenge for diesel survival is to keep its competitiveness in the CO2 vs cost equation in comparison to other propulsion systems. The development of the combustion system design still represents an important leverage for further efficiency and emissions improvements while keeping the current excellent performance in terms of power density and low-end torque.

The combustion quality in modern diesel engines depends strictly on the quality of the air-fuel mixing and, in turn, from the quality of spray atomization process. So air-fuel mixing is strongly influenced by the injection pressure, geometry of the nozzle duct and the hydraulic characteristics of the injector. In this context, spray concepts alternative to the conventional multi-hole nozzles could be considered as solutions to the extremely high injection pressure increase to assure a higher and faster fuel-air mixing in the piston bowl, with the final target of increasing the fuel efficiency and reducing the engine emissions. The study concerns an experimental depiction of a spray generated through a prototype high-pressure hollow-cone nozzle, under evaporative and non-evaporative conditions, injecting the fuel in a constant-volume combustion vessel controlled in pressure and temperature up to engine-like gas densities in order to measure the spatial and temporal fuel patterns.

The detailed study of part-load conditions is essential to characterize engine-out emissions in key operating conditions. The relevance of part-load operations is further emphasized by the recent regulations such as the new WLTP standard. Combustion development at part-load operations depends on a complex interplay between moderate turbulence levels (low engine speed and tumble ratio), low in-cylinder pressure and temperature, and stoichiometric-to-lean mixture quality (to maximize fuel efficiency). From a modelling standpoint, the reduced turbulence intensity compared to full-load operations complicates the interaction between different sub-models (e.g., reconsideration of the flamelet hypothesis adopted by common combustion models). In this article, the authors focus on chemistry-based simulations for laminar flame speed of gasoline surrogates at conditions typical of part-load operations. The analysis is an extension of a previous study focused on full-load operations.

A detailed understanding of Gasoline Direct Injection (GDI) techniques applied to spark-ignition (SI) engines is necessary as they allow for many technical advantages such as increased power output, higher fuel efficiency and better cold start performances. Within this context, the extensive validation of multi-dimensional models against experimental data is a fundamental task in order to achieve an accurate reproduction of the physical phenomena characterizing the injected fuel spray. In this work, simulations of different Engine Combustion Network (ECN) Spray G conditions were performed with the Lib-ICE code, which is based on the open source OpenFOAM technology, by using a RANS Eulerian-Lagrangian approach to model the ambient gas-fuel spray interaction.

The interest in Natural Gas (NG) as alternative fuel for transportation is constantly growing, mostly due to its large availability and lower environmental impact with respect to gasoline or diesel fuel. In this scenario, the application of the Dual Fuel (DF) Diesel- Natural Gas (NG) combustion concept to light duty engines can represent an important route to increment the diffusion of natural gas use. Many studies have proven the benefits of DF with respect to conventional diesel combustion in terms of CO2, NOx, PM and PN emissions, with the main drawback of high unburned hydrocarbon, mainly at low/partial engine loads. This last aspect still prevents the application of DF mode to small displacement engines. In the present work, a 2.0 L Euro 5 compliant diesel engine, equipped with an advanced electronic closed-loop combustion control (CLCC) system, has been set up to operate in DF mode and tested on a dyno test bench.

Knock occurrence and fuel enrichment, which is required at high engine speed and load to limit the turbine inlet temperature, are the major obstacles to further increase performance and efficiency of down-sized turbocharged spark ignited engines. A technique that has the potential to overcome these restrictions is based on the injection of a precise amount of water within the mixture charge that can allow to achieve important benefits on knock mitigation, engine efficiency, gaseous and noise emissions. One of the main objectives of this investigation is to demonstrate that water injection (WI) could be a reliable solution to advance the spark timing and make the engine run at leaner mixture ratios with strong benefits on knock tendency and important improvement on fuel efficiency.

In this paper, a parametric analysis on the main engine calibration parameters applied on gasoline Partially Premixed Combustion (PPC) is performed. Theoretically, the PPC concept permits to improve both the engine efficiencies and the NOx-soot trade-off simultaneously compared to the conventional diesel combustion. This work is based on the design of experiments (DoE), statistical approach, and investigates on the engine calibration parameters that might affect the efficiencies and the emissions of a gasoline PPC. The full factorial DoE analysis based on three levels and three factors (33 factorial design) is performed at three engine operating conditions of the Worldwide harmonized Light vehicles Test Cycles (WLTC). The pilot quantity (Qpil), the crank angle position when 50% of the total heat is released (CA50), and the exhaust gas recirculation (EGR) factors are considered. The goal is to identify an engine calibration with high efficiency and low emissions.

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.

Considering the generalized diversification of the energy mix, the use of alcohols as gasoline replacement is proposed as a viable option. Also, alternative control strategies for spark ignition engines (SI) such as lean operation and exhaust gas recirculation (EGR) are used on an ever wider scale for improving fuel economy and reducing the environmental impact of automotive engines. In order to increase the stability of these operating points, alternative ignition systems are currently investigated. Within this context, the present work deals about the use of plasma assisted ignition (PAI) in a direct injection (DI) SI engine under lean conditions and cooled EGR, with gasoline and n-butanol fueling. The PAI system was tested in an optically accessible single-cylinder DISI engine equipped with the head of a commercial turbocharged power unit with similar geometrical specifications (bore, stroke, compression ratio).

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.

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.

The present paper reassumes the results of an experimental study focused on the effects of the nozzle injector's coking varying the flow number (FN); the performance and emissions of an automotive Euro5 diesel engine have been analyzed using diesel fuel. As the improvement of the diesel engine performance requires a continuous development of the injection system and in particular of the nozzle design, in the last years the general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle holes size. The study carried out moves from the consideration that a reduction of the nozzle holes diameter could increase the impact of their coking process. For this purpose, an experimental campaign has been realized, testing the engine in steady state in three partial load operating points, representative of the European homologation driving cycle, and in full load conditions.

In recent years, due to the growing problem of environmental pollution and climate change internal combustion engine stroke volume size has been reduced. The use of down-sized engines provides benefit for reducing emissions and fuel consumption especially at the inner city driving conditions. However, when the engine demands additional power, utilizing a turbocharging system is required. This study is a joint work of Istituto Motori CNR with Automotive Laboratory of Mechanical Engineering Faculty of Istanbul Technical University (ITU) and the objective of this study was devoted to increase the understanding of various engine operating conditions on emissions, especially at low load. The trade-off between Nitrogen Oxide (NOx) and Particulate Matter (PM) emissions in a Diesel engine has been examined depending on turbocharging rates and the rate of Exhaust Gas Recirculation (EGR) applied.

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 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.

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 combustion behaviour, the mechanisms of soot formation, and the emission performance of a mixture of polyoxymethylene dimethyl ethers (POMDME) oligomers with a number of oxymethylene units ranging from 3 to 5, both neat and blended at 12.5% and 50% levels with commercial diesel fuel have been investigated. The goals were a first evaluation of the POMDME impact on the diesel injector behaviour, on the combustion process as well as on the emission performance of a light duty engine. Then a brief screening on the capability to improve the NOx-PM trade-off using POMDME by means of the exhaust gas recirculation (EGR) rate increment was also assessed.

This paper illustrates the results of an experimental study on the impact of a low cetane number (CN) oxygenated fuel on the combustion process and emissions of a light-duty (LD) single-cylinder research engine. In an earlier study, it was concluded that cyclic oxygenates consistently outperformed their straight and branched counterparts at equal oxygen content and with respect to lowering soot emissions. A clear correlation was reported linking soot and CN, with lower CN fuels leading to more favorable soot levels. It was concluded that a lower CN fuel, when realized by adding low reactive cyclic oxygenates to commercial diesel fuel, manifests in longer ignition delays and thus more premixing. Ultimately, a higher degree of premixing, in turn, was thought to suppress soot formation rates.