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Technical Paper

Soot Morphology Effects on DPF Performance

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.
Technical Paper

Scavenging Efficiency and Combustion Performance in 2T Gasoline Engine

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.
Technical Paper

Scavenge Streams Analysis in High Speed 2T Gasoline Engine

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.
Technical Paper


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.
Technical Paper

Influence of Soot Profile on Overheating During Regeneration

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.
Technical Paper

Engine Intake Noise Modelling by Using a Time/Frequency Approach

A predictive technique aimed at investigating the behaviour of intake and exhaust systems of internal combustion engine and at evaluating their influence on engine breathing and radiated noise is herewith presented. Such a technique is based on coupling a time domain gas dynamic model (composed of zero-dimensional, one-dimensional and three-dimensional methods) with a frequency domain linear acoustic analysis (transfer matrix method); thus a realistic prediction of complete engine systems is realised by adopting in each region the most appropriate method, according to the main features of the phenomena involved. The whole procedure has been applied to the intake system of an automotive engine and the results regarding different operative conditions are presented.
Technical Paper

Diesel Engine Combustion Monitoring through Block Vibration Signal Analysis

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.
Technical Paper

DPF Soot Loading and Regeneration:A Lumped Parameter Approach

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.
Technical Paper

A Lumped Parameter Scheme for DPF Loading

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.