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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.

This work fits into a research program in which the multi-cylinder diesel engine block vibration signal is used with the purpose of developing and setting up a methodology able to monitor and optimize the combustion behavior by means of non-intrusive transducer. Previously published results have demonstrated the direct relationship existing between in-cylinder pressure and engine block vibration signals in a fixed frequency band. 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, the accelerometer trace has revealed to be able to locate in the crank–angle domain important phenomena characterizing the combustion process.

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.

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.

A methodology has been developed by the authors, in which non-intrusive measurements (engine block vibration) are used for diagnostic purposes of combustion process in Diesel engines. A previous paper of the authors has been devoted to demonstrate the direct relationship between in-cylinder pressure and accelerometer signals, when the vibration transducer is placed in sensitive location. Moreover, in the engine block vibration a frequency band in which such a relationship is very strong has been selected. The aim of this work is to provide a deeper insight into the effects of injection parameters on engine block vibration, in order to investigate the possibility of detecting modification of the in-cylinder pressure evolution by means of the accelerometer signal with the final objective of optimizing the combustion process by means of non-intrusive transducer.

The present work aims at developing and setting up a methodology in which non-intrusive measurements (engine block vibration) are used for monitoring combustion characteristics (combustion diagnosis, combustion development). The engine block vibration appears as a very complex signal in which different sources can be identified, since every moving component or physical process involved in the operation of the engine produces a vibration signal (exhaust valve open/close, inlet valve open/close, fuel injection, combustion, piston slap). Aimed at monitoring the engine running condition, the information carried by the vibration signal has to be broken down into its various contributions and then they have to be related to their respective excitation sources. Concerning combustion-induced vibration, experimental measures has been at first devoted to the selection of the best location where to place the piezoelectric accelerometer.

The work aims at developing and setting up a model able to predict the diesel spray evolution to be integrated into a complete thermodynamic model of the engine. Previous papers have been devoted to realize a numerical model for the injection system, in which a lumped parameter + one-dimensional approach is employed. Such a model has been now enhanced by introducing a quasi-dimensional model for fuel break up, diffusion and penetration processes. A self-developed heating sub-model is included in the model, which enables the evaluation of the influence of the fuel properties on the evaporation process. As a result, the injection system simulation model gives indications on the spray formation process and it is used into a lumped parameter model of the combustion process. Results concerning the influence of fuel properties on the evaporation process are presented and discussed, pointing out its effect on engine performance.

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.

The research and development activities on diesel injection systems have focused some key-factors that improve the solenoid actuated injector performance, especially in the frame of the multi-event injection strategies. This paper deals with a 3-D numerical investigation that highlights the nozzle flow features of different injector layouts. A comparison between a last generation standard injector and an optimized unit characterized by an improved dynamics, different number of holes and reduced maximum lift is performed. By means of transient numerical simulations, the behavior of the fuel flows, the tendency to cavitation development and the response to the deviation from the standard operating conditions (highlighted by introducing a radial perturbation on the lift motion) are investigated.

Wide activity on Diesel vehicles control devices focuses on experimental, theoretical and numerical aspects of particulate loading and regeneration process. The study of phenomena occurring in the channels of wall flow Diesel Particulate Filters (DPF) is usually based on a one-dimensional treatment due to the channel design and the approach is generally quasi-steady, since deposition and regeneration have time scales longer than the variations in the exhaust gasses due to engine operating conditions. This 1D approach can be integrated in 1D studies of the complete exhaust gas system or coupled in 2D or even 3D investigations of the device internal fluid dynamics. In this paper, a lumped parameter (LP) model to investigate the performances of a DPF filter during the loading process is presented. The simplicity in the governing equations allows a reduction of the computational effort and thus ensures the possible use of LP model in filter control application.

This paper deals with the integrated modeling of a multiple injection common rail system. The aim of the numerical investigation is to capture the behavior of the multiple injections, in terms of electro-injector dynamic and nozzle flow development. In detail, the multiple injection investigation focuses on the transient phenomena of the injector, in order to evaluate their role on the definition of two aspects of the injection strategy, the fuel rate time evolution and their influence on the nozzle flow features. The model is based on the integration of two different commercial codes. In the simulations, a 0/1-D code has been used to analyze the complete injection system. The results obtained from the injection system simulation, in terms of injection needle lift, injection flow rate, pressure time evolution, have been used as boundary conditions for the 3-D CFD computation tool, in which the numerical investigation of the internal injector flow has been performed.

This paper deals with the numerical investigation of a Diesel engine high pressure DI system in which the influence of needle motion characteristics on the internal injector flows is evaluated; a radial perturbation of the axial needle motion has been imposed to analyze its role over the nozzle flow features. The developed model is based on the coupling of two computational tools. With the former one, AMESim code, the injector has been modeled; the results obtained from the injector simulation, in terms of injection needle lift time evolution, have been used to initialize the latter computation tool, FIRE code, in which 3D flow numerical investigation of the internal injector flows has been performed. Details of the adopted modeling strategy are presented and the results of each simulation step are shown.

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.

In this paper, the potential of noise reduction of a small single cylinder diesel engine is analysed. The attention is addressed towards the combustion-induced noise that substantially contributes to the engine radiation. Different settings of the injection equipment are investigated, since they influence to a great extent the pressure increase during the combustion process, which in turn determines the level and the spectral characteristics of the noise emission. The cylinder pressure signal is processed in time and frequency domains and is analysed in order to relate the radiation to the rate of pressure rise during the combustion process and then to the engine settings. The effect of different engine operative conditions is investigated.

The paper concerns with gas exchange and combustion process in a 2T high speed gasoline engine and presents the results of a numerical-experimental investigation, in which zero-dimensional, one dimensional and three dimensional calculation schemes are used and the tuning between numerical and experimental results is performed. The different flow patterns from which the efficiency of the scavenging strongly depends are analysed, the variation with time of the spatial distribution of the fresh charge and combustion product in the cylinder is evaluated. The combustion process is simulated and the influence of geometric parameters of the ports on the scavenging efficiency, on the emission of hydrocarbons in the exhaust system and on the performance of the combustion process is investigated.

This paper deals with the numerical investigation of a single cylinder Diesel engine equipped with an high pressure fuel injection system and it focuses on the injection system and on its effect on the combustion process. The simulations have been carried out by using AMESim environment; at first the complete system has been divided into its components and each one has been analysed by means of sub-models belonging to standard libraries and self-developed. Then, all components have been collected and the system composed of the injection system and the cylinder has been realized. The analysis of the complete system has been performed and the effect of a variation of the engine operative conditions has been investigated. The comparison between obtained results and experimental measurements has highlighted the capability of the developed tool to predict the performance of the entire engine system.

In automotive engines, combustion process substantially contributes to noise emission. The complex interaction between the excitation force (i.e. the cylinder pressure profile) and the characteristic response of the engine structure is responsible for engine block vibration and then for noise radiation. Aimed at obtaining a better understanding of the causes which mainly contribute to the combustion noise generation, a processing technique has been developed and set up, in which the trend of the mean frequency of the pressure trace in the cylinder is computed by using a sliding window of the signal. The analysis of such a trace retains great importance in the strategies devoted to control the combustion noise quantity and quality, since it allows to extract useful information to assess the contribution of the different phenomena which characterize the combustion process, in terms of their amplitude, frequency and time distribution.

In two stroke engines, the scavenging process has direct influence in the performance of combustion process and then retains great importance in the strategies oriented towards solutions characterized by improvements of fuel efficiency, engine power output and reductions of pollutant emissions. The authors have developed an integrated numerical-experimental predictive tool, based on a two-step procedure, in which zero-dimensional, one-dimensional and three-dimensional simulation models are applied. In this paper, the attention is focused on the analysis in detail of different flow patterns which contribute to determine the scavenging process in order to provide a better comprehension and then to get improvement of such complex process. Since the scavenging efficiency strongly depends on the geometry of the engine system, the effect of a variation of the geometrical parameters on the flow paths and on the distribution of the scavenge streams is investigated.

The paper deals with the implementation of a diagnosis procedure able to reveal if anomalies in the combustion process of a spark ignition engine appear and then to identify the responsible cylinder. The procedure, based on the processing of the exhaust pressure signal in both time and frequency domains, has been developed aimed at overcoming the lacks others diagnostic methodologies have exhibited when the malfunction appears during some particular engine operative conditions. At first, the effectiveness of the method has been shown by considering steady-state conditions: experimental measurements have been carried out on a spark ignition engine running in a test cell by fixing different conditions of engine speed and load. In this paper the attention has been devoted to steady conditions in which the engine operating is characterized by a large amount of irregularity; engine transient conditions have been analysed, too. The results of both steady and transient tests are presented.

An integrated numerical procedure has been developed in order to predict the noise radiation of small engine for automotive and general purpose applications. In exhaust system of single or multi-cylinder small engine, complex shape elements are always included (junction, compact chamber), where non-planar higher-order modes exist. Besides, the amplitude of pressure wave, propagating inside such exhaust systems, is generally not bounded by linear acoustic limit. For these reasons, aimed at providing realistic and accurate description of their fluid dynamic and acoustic behaviour, an integrated multi-code methodology, based on 0D, 1D and 3D models, has been set up; the investigation of the flow conditions all throughout the exhaust system, allows to predict the sound emission.