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Technical Paper

MFB50 On-Board Evaluation Based on a Zero-Dimensional ROHR Model

In modern Diesel engine control strategies the guideline is to perform an efficient combustion control, mainly due to the increasing request to reduce pollutant emissions. Innovative control algorithms for optimal combustion positioning require the on-board evaluation of a large number of quantities. In order to perform closed-loop combustion control, one of the most important parameters to estimate on-board is MFB50, i.e. the angular position in which 50% of fuel mass burned within an engine cycle is reached. Furthermore, MFB50 allows determining the kind of combustion that takes place in the combustion chamber, therefore knowing such quantity is crucial for newly developed low temperature combustion applications (such as HCCI, HCLI, distinguished by very low NOx emissions). The aim of this work is to develop a virtual combustion sensor, that provides MFB50 estimated value as a function of quantities that can be monitored real-time by the Electronic Control Unit (ECU).
Technical Paper

Common Rail Multi-Jet Diesel Engine Combustion Development Investigation for MFB50 On-board Estimation

Proper design of the combustion phase has always been crucial for Diesel engine control systems. Modern engine control strategies' growing complexity, mainly due to the increasing request to reduce pollutant emissions, requires on-board estimation of a growing number of quantities. In order to feedback a control strategy for optimal combustion positioning, one of the most important parameters to estimate on-board is the angular position where 50% of fuel mass burned over an engine cycle is reached (MFB50), because it provides important information about combustion effectiveness (a key factor, for example, in HCCI combustion control). In modern Diesel engines, injection patterns are designed with many degrees of freedom, such as the position and the duration of each injection, rail pressure or EGR rate. In this work a model of the combustion process has been developed in order to evaluate the energy release within the cylinder as a function of the injection parameters.
Journal Article

Instantaneous Engine Speed Measurement and Processing for MFB50 Evaluation

Evaluation of MFB50 is very useful for combustion control, since it gives an evaluation of the combustion process effectiveness. Real-time monitoring its value enables to detect for example the kind of combustion that is taking place (useful for example for HCCI applications), or could provide important information to improve real-time combustion control. While it is possible to determine the position where the 50% of mass burned inside the cylinder is reached using an in-cylinder pressure sensor, this work proposes to obtain this information from the engine speed fluctuation measurement. In-cylinder pressure sensors in fact are still not so common for on-board applications, since their cost will constitute an important portion of the whole engine control system cost.
Technical Paper

A Mean Value Model of the Exhaust System with SCR for an Automotive Diesel Engine

Nowadays requirements towards a reduction in fuel consumption and pollutant emissions of Internal Combustion Engines (ICE) keep on pushing manufacturers to improve engines performance through the enhancement of existing subsystems (e.g.: electronic fuel injection, air systems) and the introduction of specific devices (e.g.: exhaust gas recirculation systems, SCR, …). Modern systems require a combined design and application of different after-treatment devices. Mathematical models are useful tools to investigate the complexity of different system layouts, to design and to validate (HIL/SIL testing) control strategies for the after-treatment management. This study presents a mean value model of an exhaust system with SCR; it has been coupled with a common rail diesel engine combustion black box model (Neural Network based). So, dedicated models for exhaust pipes, oxidation catalyst, diesel particulate filter and selective catalytic converter are developed.
Technical Paper

A thermodynamic Mean Value Model of the intake and exhaust system of a turbocharged engine for HiL/SiL applications.

Regarding automotive applications, Internal Combustion Engines (ICE) have become very complex plants to comply with present and future requirements in reduction of fuel consumption, pollutant emissions and performance improvement. As a consequence, the development of engine control and diagnostic system is a key aspect in the powertrain design. Mathematical models are useful tools in this direction, with applications that range from the definition of optimised management systems, to Hardware- and Software-in-the-Loop testing (HiL and SiL) and to modelbased control strategies. To this extent an original library has been developed by the authors for the simulation of last generation automotive engines. Library blocks were used to assembly a sub-model of the typical intake and exhaust system of a turbocharged engine (with VGT, intercooler, EGR circuit with cooler and throttle).
Technical Paper

Upgrade of a Turbocharger Speed Measurement Algorithm Based on Acoustic Emission

The present paper is about the rotational speed measurement of an automotive turbocharger, obtained starting from the analysis of acoustic emission produced by an engine, which have been acquired by a microphone placed under the vehicle hood. In the first part of the paper several upgrades to increase the overall performance of the speed extraction algorithm are presented and discussed, starting from the basic algorithm that has already demonstrated the methodology capability in a previous paper. In particular it has been considered a different signal sampling rate in order to extend the applicability of the methodology to a wider range of engines. Also a new processing procedure has been defined to increase the capability of the algorithm to tune on the frequency signal.
Journal Article

Powertrain Torsional Model Development or On-Board Indicated Torque Estimation

Effective and precise torque estimation is a great opportunity to improve actual torque-based engine management strategies. Modern ECU often already implement algorithms to estimate on-board the torque that is being produced by the engine, even if very often these estimation algorithms are based on look-up tables and maps and cannot be employed for example for diagnostic purposes. The indicated torque estimation procedure presented in this paper is based on the measurement of the engine speed fluctuations, and is mainly based on two separated steps. As a first step a torsional behavior model of the powertrain configuration is developed. The engine-driveline torsional model enables to estimate the indicated torque frequency component amplitude from the corresponding component of the instantaneous engine speed fluctuation. This estimation can be performed cycle by cycle and cylinder by cylinder.
Technical Paper

Exhaust Gas Turbocharger Speed Measurement Via Acoustic Emission Analysis

The paper presents a non-intrusive, indirect and low-cost methodology for a real time on-board measurement of an automotive turbocharger rotational speed. In the first part of the paper the feasibility to gather information on the turbocharger speed trend is demonstrated by comparing the time-frequency analysis of the acoustic signal with the direct measurement obtained by an optical sensor facing the compressor blades, mounted in the compressor housing of a spark ignited turbocharged engine. In the second part of the paper, a real time algorithm, to be implemented in the engine control unit, is proposed. The algorithm is able to tune on the turbocharger revolution frequency and to follow it in order to extract the desired speed information. The frequency range containing the turbocharger acoustic frequency can be set utilizing a raw estimation of the compressor speed, derived by its characteristic map.
Technical Paper

Common Rail Multi-Jet Diesel Engine Combustion Model Development for Control Purposes

Multi-jet injection strategies open significant opportunities for the combustion management of the modern diesel engine. Splitting up the injection process into 5 steps facilitates the proper design of the combustion phase in order to obtain the desired torque level, whilst attempting a reduction in emissions, particularly in terms of NOx. Complex 3-D models are needed in the design stage, where components such as the injector or combustion chamber shape have to be determined. Alternatively, zero-dimensional approaches are more useful when fast interpretation of experimental data is needed and an optimization of the combustion process should be obtained based on actual data. For example, zero-dimensional models allow a quick choice of optimum control settings for each engine operating condition, avoiding the need to test all the possible combinations of engine control parameters.
Technical Paper

Minimization of Particulate Raw Emissions from CR-Diesel Engines - A Key-Element to Limit the Increase in Complexity of Exhaust Gas After-Treatment

The present paper describes a study of the basic parameters, which govern particulate (soot) formation within the combustion chamber of a small displacement (1.3 liter) turbocharged European CR-diesel engine. The main tools used for the study are a real fired engine, a numerical virtual engine and a special high ambient pressure vessel for injector spray visualization. The paper describes an improved soot formation model implemented in the virtual engine setup. A comparison is presented between measured and computed combustion data at 8 different load points. The paper concludes with a discussion of the means, which can be used to minimize the particulate matter formation in the design phase of both the combustion layout and the fuel injector atomizer as well as in the design of the injection control strategies.
Technical Paper

Analysis of a Dual Mass Flywheel System for Engine Control Applications

Dual Mass Flywheel (DMF) systems are today widely adopted in compression ignition automotive powertrains, due to the well-known positive effects on vehicle drivability and fuel consumption. This work deals with the analysis of undesirable effects that the installation of a DMF may cause to engine and transmission dynamics, with the objective of understanding the causes and of determining possible solutions to be adopted. The main results of an experimental and simulation analysis, focused on the rotational dynamics of a powertrain equipped with a DMF system, are presented in the paper. A mathematical model of the physical system has been developed, validated, and used to investigate, in a simulation environment, the anomalous behavior of the powertrain that had been experimentally observed under specific conditions. Particular attention has been devoted to two aspects that are considered critical: engine cranking phase; interactions between powertrain dynamics and idle speed control.
Technical Paper

Measurement of Torque Transmissibility in Diaphragm Spring Clutch

: This article presents the latest developments of a research project aimed at studying the evolution of the transmissibility curve of dry clutches for automobile uses during the life of the component. In particular, the instruments developed for the experimental measurement of this characteristic are illustrated, separating the effects of thinning of the disc by wear from fatigue of the clutch pushplate mechanism. The instruments developed were used to collect a large quantity of experimental data which are presented and discussed.
Technical Paper

Misfire Detection Based on Engine Speed Time-Frequency Analysis

The paper presents the development of a methodology for detecting the misfire event using the time-frequency analysis of the instantaneous engine speed signal. The diagnosis of this type of malfunctioning operating condition is enforced by OBD requirements over the whole operating range of the engine, and many different approaches have been developed in the past in order to solve this problem. The novel approach presented here is based on the observation that the misfire causes an impulsive lack of torque acting on the engine crankshaft, and thus it causes the excitation of damped torsional vibrations at frequencies characteristic of the system under study. In order to enlighten the presence of this torsional vibration (and therefore detect the misfire event), information contained in the instantaneous crankshaft speed fluctuations have been processed in the time-frequency domain.
Technical Paper

Thermodynamic Analysis of Variable Valve Timing Infuence on SI Engine Efficiency

The large number of mechanical, electro-magnetic and oleo-dynamic systems for variable valve actuation developed by automotive suppliers demonstrates the great interest that is being devoted to their potential application on internal combustion engines. In the paper, a possible strategy to realize an original engine load control by means of both intake and exhaust variable valve timing (VVT) is briefly presented and the thermodynamic analysis of the performance obtainable with this solution is carried out. The peculiarity of this strategy is that it is possible to directly recirculate the desired mass of exhaust gas with less limitation with respect to the external duct architecture.
Technical Paper

Experimental Methodologies To Determine Diaphragm Spring Clutch Characteristics

The paper presents an experimental study to investigate the relationships among diaphragm spring clutch transmitted torque, thermal phenomena during clutch engagement and clutch wear. The work describes the development of a test bench presented by the Authors in a former paper. The original techniques were developed to measure the desired magnitudes and to develop the experimental methodology to investigate the relationships. The main results were obtained considering different operating conditions, dynamics of thermal phenomena and clutch wear.
Technical Paper

A Computer Code for S.I. Engine Control and Powertrain Simulation

A computer code oriented to S.I. engine control and powertrain simulation is presented. The model, developed in Matlab-Simulink® environment, predicts engine and driveline states, taking into account the dynamics of air and fuel flows into the intake manifold and the transient response of crankshaft, transmission gearing and vehicle. The model, derived from the code O.D.E.C.S. for the optimal design of engine control strategies now in use at Magneti Marelli, is suitable both for simulation analysis and to achieve optimal engine control strategies for minimum consumption with constraints on exhaust emissions and driveability via mathematical programming techniques. The model is structured as an object oriented modular framework and has been tested for simulating powertrain system and control performance with respect to any given transient and control strategy.
Technical Paper

Development and Validation of a Model for Mechanical Efficiency in a Spark Ignition Engine

A set of models for the prediction of mechanical efficiency as function of the operating conditions for an automotive spark ignition engine is presented. The models are embedded in an integrated system of models with hierarchical structure for the analysis and the optimal design of engine control strategies. The validation analysis has been performed over a set of more than 400 steady-state operating conditions, where classical engine variables and pressure cycles were measured. Models with different functional structures have been tested; parameter values and indices of statistical significance have been determined via non-linear and step-wise regression techniques. The Neural Network approach (Multi Layer Perceptrons with Back-Propagation) has been also used to evaluate the feasibility of using such an approach for fast black-box modelization.