Search Results

The present paper describes the results of a cooperative research project between GM Powertrain Europe and Istituto Motori - CNR aimed at studying the capability of GM Combustion Closed-Loop Control (CLCC) in enabling seamless operation with high biodiesel blending levels in a modern diesel engine for passenger car applications. As a matter of fact, fuelling modern electronically-controlled diesel engines with high blends of biodiesel leads to a performance reduction of about 12-15% at rated power and up to 30% in the low-end torque, while increasing significantly the engine-out NOx emissions. These effects are both due to the interaction of the biodiesel properties with the control logic of the electronic control unit, which is calibrated for diesel operation. However, as the authors previously demonstrated, if engine calibration is re-tuned for biodiesel fuelling, the above mentioned drawbacks can be compensated and the biodiesel environmental inner qualities can be fully deployed.

In the present paper, the effect of the clean and cold EGR flow on the performance of a diesel engine running under conventional and Low Temperature Combustion conditions is investigated by means of experimental tests on a single-cylinder research engine. The engine layout was “ad hoc” designed to isolate the effect of the clean and cold recirculated gas flow on the combustion quality. The results have shown that the thermodynamic temperature is the main factor affecting the engine performances, while the effect of a cleaner EGR flow, in terms of lower smoke and unburned compounds (HC and CO), is negligible.

In the global scenario of encouraging the use of renewable sources, the bioethanol as fuel supply in the automotive sector is receiving increasing interest. In the present paper the results of a research activity aimed to study the impact of a bioethanol/biodiesel/mineral diesel blend on performance and emissions of an automotive diesel engine are reassumed. An experimental campaign has been devoted to characterize the engine fuelled by the ethanol based blend highlighting the advantages and issues related to the bioethanol use. Moreover, the effects of the most important injection settings on the engine performance have been detailed, applying a Design of Experiment (DoE) method, to identify the potentiality offered by a proper engine calibration to optimize the ethanol blend use.

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.

Natural gas as an internal combustion engine fuel is taking a predominant role as a mid-term solution to pollution due to combustion driven human activities both in the energy and transport sectors. Engine researchers and manufacturers are in the process of investigating and improving strategies that decrease emissions and fuel consumption, without compromising engine performance and efficiency; active pre-chamber configurations are to be accounted for as one of these. A relatively small amount of fuel (up to 10 % of the total fuel-energy requirement) is introduced in the confined volume of the pre-chamber and forms a close-to-stoichiometric mixture with fresh charge that is introduced from the main combustion chamber during the compression stroke. After spark-ignition the products of this early stage of combustion can ignite ultra-lean mixtures (with λ up to 2) through the Turbulent Jet Ignition mechanism, hence reducing fuel consumption as well as noxious emissions such as NOx.

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.

The present paper describes some results of a research project aimed at studying the impact of alternative fuels blends on the emissions and fuel consumption of an Euro 5 automotive diesel engine. Two alternative fuels were chosen for the experiments: RME and GTL. The tests were done in the three most important operating conditions for the engine emission calibration. Moreover, the NOx-PM trade-off by means of EGR sweep was performed in the same operating conditions, in order to evaluate the engine EGR tolerability when burning low sooting fuels as the RME. The investigations put in evidence that the impact of the alternative fuels on modern diesel engines remains significant. This also depends on the interaction between the alternative fuel characteristics and the engine-management strategies, as described in detail in the paper.

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.

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.

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.

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 an experimental and numerical study on the effect of the nozzle flow number (FN) on the full load performance of a modern Euro5 diesel automotive engine, in terms of torque, efficiency and exhaust emissions. The improvement of the diesel engine performance requires a continuous development of the engine components, first of all the injection system and in particular the nozzle design. One of the most crucial factors affecting performance and emissions is the nozzle flow number and its influence becomes more and more important as high performance and low emissions are continuous requirements. Indeed, reducing the nozzle flow number, due to an increase of spray-air mixing, an improvement in PM-NOx trade-off is generally expectable. On the other hand, at full load, where peak firing pressure and exhaust valve temperature become the limiting factors, critical operating conditions can be easily reached reducing the nozzle hole diameter.

The present paper describes an experimental study on the application of a Low Pressure EGR system, equipped with an high efficiency cooler, to a LD diesel engine operating with both conventional combustion and PCCI mode. The research activity is aimed to carry out an analysis of the potentiality of the cooling (with engine water at 90°C) and super-cooling (with external water at 20°C) of the low pressure EGR flow gas on the simultaneous reduction of fuel consumption and pollutant emissions. The effects were evaluated running the engine with diesel conventional combustion and PCCI mode in several engine operating points. The employed engine was a 4-cyliders LD CR diesel engine of two liters of displacement at the state of art of the current engine technology. The overall results identified benefits on both the fuel consumption and emissions with the use of a low pressure EGR system with respect to the “classical” high pressure EGR one.

In this paper the methane-gasoline dual fuel combustion was investigated. Gasoline was injected in the intake manifold (PFI fuel), while methane was injected in the combustion chamber (DI fuel), in order to reproduce a stratified combustion. The combustion process and the related engine performance and pollutant emissions were analyzed. The measurements were carried out in an optically accessible small single-cylinder four-stroke engine. It was equipped with the cylinder head of a commercial 250 cc engine representative of the most popular two-wheel vehicles in Europe. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, optical techniques based on 2D-digital imaging were used to follow the flame front propagation and the soot and temperature concentration in the combustion chamber.

The present paper describes the effects of some operating parameters on the performance of a single cylinder research engine when it runs under Low Temperature Combustion (LTC) conditions. Aim of the experimental work was to explore the potential of the control of each parameter on the improvement of LTC application to the modern LD diesel engines for passenger cars. In particular, the effects on LTC performance of the following operating parameters in different engine test points were analyzed: intake air temperature, exhaust EGR cooler temperature, intake pipe pressure, exhaust pipe pressure and swirl ratio. Some parameters have shown a particular influence on the improvement of EGR tolerability for maximum NOx reduction preserving fuel consumption and smoke, while others have evidenced poor sensitivity.

An increasing interest in the use of natural gas in CI engines is currently taking place, due to several reasons: it is cheaper than conventional Diesel fuel, permits a significant reduction in the amount of emitted carbon dioxide and is intrinsically cleaner, being much less prone to soot formation. In this respect, the Dual Fuel (DF) concept has already proven to be a viable solution, industrially implemented for several applications in the high duty engines category. Despite this, some issues still require a technological solution, preventing the commercialization of DF engines in wider automotive fields: the release of high amounts of unburned fuel, the risk of engine knock, the possible thermal efficiency reduction are some factors regarding the fuel combustion aspect. DF configuration examined in the present paper corresponds to Port Fuel Injection of natural gas and direct injection of the Diesel Fuel.

The present paper describes the results of an experimental activity performed on a small diesel engine for quadricycles, a category of vehicles that is spreading in Europe and is recently spreading over Indian countries. The engine is a prototype three-cylinder with 1000 cc of displacement and it 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 emission standard that is a future regulation for quadricycles. It is worth underlining that the engine can meet emission limits just with EGR system and a DOC, without DPF. Various diesel/RME blends were tested; pure diesel and biodiesel fuels were also used. The investigation was carried out at the engine speeds of 1400, 2000 and 3400 rpm and full load. Combustion characteristics of both blended and pure RME were analyzed by means of in-cylinder pressure and heat released histories.

Multi-fuel operation is one of the main topics of investigative research in the field of internal combustion engines. Spark ignition (SI) power units are relatively easily adaptable to alternative liquid-as well as gaseous-fuels, with mixture preparation being the main modification required. Numerical simulations are used on an ever wider scale in engine research in order to reduce costs associated with experimental investigations. In this sense, quasi-dimensional models provide acceptable accuracy with reduced computational efforts. Within this context, the present study puts under scrutiny the assumption of spherical flame propagation and how calibration of a two-zone combustion simulation is affected when changing fuel type. A quasi-dimensional model was calibrated based on measured in-cylinder pressure, and numerical results related to the two-zone volumes were compared to recorded flame imaging.

The present paper describes a detailed experimental analysis on the effect of the compression ratio on the performance of a single-cylinder research diesel engine operating with both conventional combustion and Low Temperature Combustion mode for low NOx emissions. The single-cylinder engine was developed with the same combustion system architecture of the four-cylinder FIAT 1.9 liter Multi-Jet. Starting from an engine configuration with a compression ratio of 16.5, the compression ratio was reduced to 14.5. For both the geometric configurations, engine performance was evaluated in terms of thermodynamic parameters, emissions and fuel consumption in some operating test points representative of the engine behavior running on the NEDC cycle.