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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.

Usually, the activation of DPF regeneration strategies is based on the estimation of the total particulate mass collected in the filter by means of the backpressure measure; no information concerning soot deposition profile on porous media is considered. In this paper, a numerical procedure is used to investigate the influence of soot profile on overheating during the regeneration process inside a commercial Diesel Particulate Filter. At first, the soot deposition profile, identified by a low number of parameters, is computed basing on the engine operative conditions. Then, the regeneration process is simulated. In this way, not only the amount of the total accumulated mass is taken into account, but the role of the shape of soot profile is accounted for. This allows to evaluate the correlation between the shape of collected particles layer and possible local overheating phenomena, which are very important to avoid critical thermal-structural stresses.

Diesel particulate filters are well known for their efficiency and reliability in trapping particulate matter out of diesel engines. In the last years, many efforts have been done to improve their performances, leading to the employment of new materials and architectures, as well as sophisticated regeneration and management strategies. A lumped parameter model has been developed by the authors able to ensure good accuracy and fast processing for DPF control applications. In this paper, the attention is at first addressed towards the loading process; the evolution with time of pressure drop inside the filter structure is computed and basing on the engine operative condition, a parametrization of the deposited soot layer profile is proposed, in which the effect of the flow distribution at the cross section of the filter is accounted for. The regeneration process is then investigated and temperature profile inside the filter channel is analyzed.

This paper presents a lumped parameter (LP) model to compute diesel soot morphology, in terms of radii of gyration and fractal diameters, starting from the engine operating conditions. The global soot production inside the combustion chamber is evaluated, too. Such a model represents an enhancement of a previously developed LP approach in which the loading and regeneration processes inside a Diesel Particulate Filter (DPF) are investigated. The performance of the DPF during loading is evaluated according to soot layer thickness and pressure drop; the characteristics of soot morphology and particulate deposit are accounted for during the regeneration. Results are presented and validated by means of comparison to those obtained by experimental measures and 3D CFD simulations.

Many efforts are being currently devoted to the development of diagnostic techniques based on nonintrusive measurements aimed at defining the injection parameters able to optimize the combustion process. Previous papers of the authors have demonstrated a direct relationship between in-cylinder pressure and engine block vibration signals. Besides, it was also shown sensitivity of the engine surface vibration to variation of injection parameters, when the accelerometer is placed in sensitive location of the engine block. Moreover, in the accelerometer signal, a frequency band in which such a relationship is very strict has been selected. The aim of the present work is to establish a reliable relation between the main characteristics of the in-cylinder pressure curve and the vibration trend, by means of a deeper insight into the engine block signal. The final objective is to monitor the combustion behavior by means of a non-intrusive transducer.

A diesel injection model for common rail application has been built and extended including a quasi-dimensional, multi-zone, diesel combustion-pollutant emission model (NO x ). In a commercial simulation environment, a lumped parameter electro-mechanical-hydraulic scheme is used to model the injection process. Modeling of spray formation, droplet vaporization, combustion and pollutant emission processes is then implemented in a self developed computation code, accounting for finite thermal conductibility of the liquid phase fuel. The coupling among the models allows for a detailed representation of the involved phenomena at each simulation step; at the same time, it is possible to evaluate the operation of the ensemble injection system-engine on the basis of atomization, combustion and pollutant emission. The results of the numerical prediction are compared to experimental data.

The present work investigates a multi-cylinder Diesel engine with integrated automatic transmission and gearbox, equipped with a common rail injection system for mini-car sector application. Previous research work has been devoted to examine the engine NVH characteristics; the attention has been addressed to the analysis of the direct relationship existing between in-cylinder pressure and engine block vibration signals with the final purpose of developing and setting up a methodology able to monitor and optimize the combustion process by means of non-intrusive measurements. The aim of this paper is to improve the performance of the engine in different operating conditions by means of both experimental and numerical approaches. Experimental tests have been conducted on the engine in a dynamic test bed in order to account for the actual loading conditions.

This paper presents the results of an experimental analysis on a multi-cylinder diesel engine, in which in-cylinder pressure and accelerometer transducers are used with the purpose of developing and setting up a methodology able to monitor and optimize the combustion behavior by means of non-intrusive measurements. Previously published results have demonstrated the direct relationship existing between in-cylinder pressure and engine block vibration signals, as well as the sensitivity of the engine surface vibration to variation of injection parameters when the accelerometer is placed in sensitive location of the engine block. Moreover, the accelerometer trace has revealed to be able to locate in the crank-angle domain important phenomena characterizing the combustion process (the start of pre-mixed combustion, the crank angle value corresponding to the beginning of diffusive combustion and to the in-cylinder pressure maximum value).

The performances of high pressure fuel-injection systems and their effects on diesel engine combustion are strongly influenced by the injector characteristics and the set up of the whole equipment control system. High-pressure system based on the common-rail architecture allows a multi-stage injection, which is of paramount importance in controlling combustion noise, fuel consumption, operation roughness and exhaust pollutant emissions. Common rail fuel injection equipment for automotive diesel engine, together with its control system have been analysed by using AMESim environment; both standard library elements and self-developed sub-models have been adopted. At first the different components have been considered one by one; in this way the behaviour of high pressure pump (radial-jet), pressure regulator, rail, injectors, system control (e. c. u.) has been investigated; the results have been compared with experimental measurements.

The optimization of the combustion process in diesel engines is one of the challenges to improve performance, emissions, fuel consumption and NVH characteristics. This work constitutes one of the last steps of a comprehensive research program in which vibration sensors are used with the purpose of developing and setting up a methodology that is able to monitor and optimize the combustion process by means of non-intrusive measurements. Previously published results have demonstrated the direct relationship that exists between in-cylinder pressure and engine block vibration signals, as well as the sensitivity of the engine surface vibration to variation of injection parameters when the accelerometer is placed in a sensitive location of the engine block.

The paper presents a non-intrusive technique in which accelerometers are used to provide information about the metric of the in-cylinder pressure development, with the final aim of using their signal as feedback in a control algorithm for the injection control unit. Previous papers by the authors have been devoted to the evaluation of the potential of using vibration transducers; the analysis in both the time and frequency domain of the accelerometer and in-cylinder pressure signals has allowed for the separation of the vibration components caused by the combustion process from those due to other sources. The combustion related vibration has then been used to characterize the in-cylinder pressure development.

This paper presents the results of an experimental study on the application of an engine block vibration transducer. The aim of the study was to accomplish a real time management of the control unit using the vibration signal as a feedback to correct the injection parameters setting. The continuously strengthened exhaust emission regulations and the constrains related to the fuel consumption and noise, vibration and harshness (NVH) characteristics, have determined increasing interest towards investigation of the potentiality of new combustion technologies and fuel blends capable of reducing particulate matter and NOx emissions. Focus has also been paid to non-intrusive techniques for the combustion process characterization by means of sensors, such as microphones and accelerometers.

To ensure compliance with emerging Diesel emission standards and demands for reduced fuel consumption, the optimization of the engine operation is imperative under both stationary and real operation conditions. This issue imposes a strict control of the combustion process that requires a closed-loop algorithm able to provide an optimal response of the engine system not only to warm-up, accelerations, changes in the slope of the road, etc., but also to engine aging and variations of fuel properties. In this paper, with the final purpose of accomplishing an innovative control strategy based on non intrusive measurement, the engine block vibration signal is used to extract useful information able to characterize the in-cylinder pressure development during the combustion process. In the previous research activity, the same methodology was applied to stationary operation of the engine.

Concerns about the harmful exhaust emissions of internal combustion engines have imposed the employment of aftertreatment devices to reduce their impacts both on health and environment. System modeling of engine and aftertreatment devices is required not only to provide an accurate assessment of the engine and aftertreatment devices performances as single elements but also to quantify the complex interaction of these components from a thermo fluid perspective. The work focuses on development of a model capable of predicting temporal and spatial evolution of thermo-fluid quantities and chemical species in a diesel oxidation catalyst (DOC). The developed model allows to investigate the influence of thermal characteristics and gas composition on the evolution of the phenomena occurring in the device which deeply reflect on the particulate filter behavior during regeneration phase.

In the last years, the increasing concern for the environmental issues of IC engines has promoted the development of new strategies capable of reducing both pollutant emissions in atmosphere and noise radiation. Engines can produce different types of noise: 1) aerodynamic noise due to intake and exhaust systems and 2) surface radiated noise. Identification and analysis of noise sources are essential to evaluate the individual contribution (injection, combustion, piston slap, turbocharger, oil pump, valves) to the overall noise with the aim of selecting appropriate control strategies. Previous paper focused on the combustion related noise emission. The research activity aimed at diagnosing and controlling the combustion process via acoustic measurements. The optimal placement of the microphone was selected, where the signal was strongly correlated to the in-cylinder pressure development during the combustion process.

Many studies have demonstrated that an efficient control of the combustion process is crucial in order to comply with increasingly emerging Diesel emission standards and demanding for reduced fuel consumption. Methodologies based on real-time techniques are imperative and even if newly sensors will be available in the near future for on-board installation inside the cylinder, non intrusive measurements are still considered very attractive. This paper presents an experimental activity devoted to analyze the noise emission from a small displacement two-cylinder Diesel engine equipped by HPCR (high pressure common rail) fuel injection system. The signals acquired during stationary operation of the engine are analyzed and processed in order to highlight the different sources contributing to the overall emission. Particular attention is devoted to the specific samples of the signal that are mainly caused by the combustion process in order to extract the combustion contribution.

The current work presents the results of an investigation on the impact of renewable fuels on the combustion and emissions of a turbocharged compression-ignition internal combustion engine. An experimental study was undertaken and the engine settings were not modified to account for the fuel's chemical and physical properties, to analyze the performance of the fuel as a potential drop-in alternative fuel. Three fuels were tested: mineral diesel, a blend of it with waste cooking oil biodiesel and a hydrogenated diesel. The analysis of the emissions at engine exhaust highlights that hydrogenated fuel allows to reduce CO, total hydrocarbon emissions, particulate matter and NOx.