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Nowadays the main part of investigations in controlled auto-ignition (CAI) engines are centered on performance or some engine processes simulation, leaving aside particle number (PN) emission. The present work is focused on this last topic: PN emission analysis using two different injectors in a 2-stroke CAI engine, and a global comparison of PN emission of this engine with its homonymous 4-stroke engines at two operating conditions. The study was performed in a single-cylinder gasoline engine with 0.3 l displacement, equipped with an air-assisted direct-injection (DI) fuel injection system. Concerning the injectors evaluated, significant differences in PN emission have been found. When the I160X injector (narrow spray angle) was used, PN emissions were reduced. The spray cone angle during the injection event appears to be a key factor for PN emission reduction.

Wall-flow diesel particulate filters have become the most effective system for particulate matter abatement in Diesel engines being required for current and future emission standards fulfillment. Despite the high filtration efficiency that wall-flow DPFs exhibit their use involves a noticeable impact in fuel consumption because of the increase of the exhaust back-pressure. Additionally, the fuel economy penalty increases as the DPF becomes soot/ash loaded. This constraint demands the approach and development of new solutions to reduce the DPF pressure drop. This paper focuses on the improvement of the ratio between the pressure drop and the loading by means of pre-DPF water injection. A proper management of the water injection events is able to completely remove the dependence between these magnitudes. The test campaign and the discussion of the experimental results address how the DPF pressure drop reduction leads to benefits in engine fuel consumption.

Major accuracy for prediction tools like CFD codes require precise experimental validation. The ultraviolet and visible light absorption and scattering (UV-VIS LAS) is proposed for characterizing air-fuel mixture formation. UV-VIS LAS technique is employed to quantitatively determine spatial concentration distribution of vapor fuel, in combination with simultaneous liquid length and spray penetration measurements by means of Mie-scattering and Schlieren. Decane, Hexadecane and a 50/50 of both fuels have been chosen for this study, to evaluate mixing formation under Diesel conditions. Work has been performed at an optical engine under non-reacting atmosphere, with ambient pressures and temperatures up to 7.3 MPa and 900 K. Fuel optical properties for the two paraffines under engine conditions have been analyzed, and fuel concentration distribution has been obtained for pure fuels.

The pressure drop across the aftertreatment systems directly affects the fuel economy as a function of the flow characteristics and also the soot loading in the case of the Diesel particulate filter. However, the relative position of this system with respect to the turbine has an additional effect which is dependent on the influence of the turbine expansion ratio. When the DPF is placed upstream of the turbine, its pressure drop is not affected by the multiplicative effect of the turbine expansion ratio to set the exhaust manifold pressure. This work concentrates on the analysis of the influence that the aftertreatment pressure drop has on the engine performance depending on the DPF soot loading and the location of the aftertreatment with respect to the turbine. The interaction with the turbocharger and the EGR operation is also analyzed taking as reference a two stage turbocharger heavy duty Diesel engine.

Pure biodiesel is non-toxic, biodegradable and greenhouse gas neutral alternative fuel with potential successful future but reduced quantitative information is available about the impact of biodiesel on engine durability and long period usage effects. In this study, a commercial light duty Diesel engine installed on an engine test bench has been operated fuelled with pure biodiesel (B100 referred to the EN-14214 standard) during a period test of 300 hours in order to analyze engine performance and components behavior. A engine characterization has been completed using conventional diesel fuel (EN 590). Then, following a specific defined operation cycle and fuelled with pure biodiesel, a study over different engine components such as: engine oil, fuel filters, Diesel Particulate Filter (DPF), so on, has been done in order to obtain possible negative effects and modifications required over maintenance policies applied to them.

In-cylinder emission control strategies, such as modifications of injection pressure and injection timing, have been used by researchers in order to reduce exhaust emissions and to comply with the legislation standards. Since some years ago post-injections have been studied and are well known as being efficient for soot emissions reduction. Although is well known that diesel gaseous and particle mass emissions have been reduced progressively over the last twenty years in response to the restrictive emission legislation and due to the application of new technologies The aim of this work is to help develop and understand the effect of the post-injection on diesel exhaust particle size distributions. The approach is to use a modern, well instrumented research engine equipped with a flexible high pressure fuel injection system. The results of this work are available to help provide guidelines for strategies to achieve reductions of the particle size distributions in diesel engines.

The upcoming emission regulations for Diesel engines will become more restrictive. This has made it necessary to develop new diagnostic tools and methods that allow to obtain a more accurate knowledge about the chemical and physical phenomena that occur during the atomization, evaporation and ignition of the fuel spray. This paper describes an experimental setup for injection and combustion research. The system is based on a two-stroke direct injection Diesel engine whose cylinder head is equipped with four optical accesses. Inlet flow can be switched either to nitrogen or to ambient air. In both cases, thermodynamic properties are controlled to reproduce the actual conditions of density, temperature and pressure at the end of the compression stroke in a real engine. A high-pressure common-rail system with an electronic control unit makes it possible to modify injection parameters: pressure, timing, duration and frequency.

The objective of this paper is to describe a turbochargers test bench capable of elaborating turbochargers maps, under pulsating or continuous flow conditions. With this experimental tool it is possible to obtain information about turbocharger performance at realistic engine operative points. Consequently, the experimental tool is able to complete and validate manufacturers turbochargers maps. In order to deeply achieve these objectives, the turbocharger test bench is used in combination with a gas-dynamic code, which provides an accuracy simulation of the experimental installation. In addition, the obtained information will increase the power of modelling codes used for turbocharged engines design.

In the paper is described how to characterise the combustion process of a high speed turbocharged direct injection diesel engine (HSDI) during a transient process, which consists on a full load acceleration at constant engine speed, known as load transient. The combustion characterisation is based on the cycle to cycle combustion analysis and the Rate of Heat Release calculation (RoHR). The information presented in the paper includes, the transient recorded data at three different engine speeds joint with information about transducers characteristics and measurement frequencies. The post-processing of the obtained information and its synchronization is described in detail; a protocol of the process is finally obtained. The RoHR of every transient cycle is calculated and shown as final objective of the work.

The purpose of this paper is to present the results of a study on the exhaust junctions geometry. Twelve three-branch junctions of different geometry have been tested on a single cylinder engine. The parameters studied have been exhaust junction outlet-to-inlet diameter ratio, length, angle between inlet branches and the existence of a reed separating inlet branches. An analysis of the pressure waves amplitude (incident, reflected and transmitted) obtained from instantaneous pressure measurements in some locations around the junction has been carried out. The analysis of results shows that junction length has a low influence on its behavior. The ratio between inlet and outlet branches diameters increases both reflection and directionality (avoiding pressure wave transmission to the adjacent branch). The existence of a reed separating the inlet flows may increase directionality with moderate pressure losses if the throat area is not reduced.