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Brusiani F.,University of Bologna | Bianchi G.M.,University of Bologna | Di Gioia R.,Magneti Marelli Powertrain SPA
SAE International Journal of Engines | Year: 2013

Diesel engine performances are strictly correlated to the fluid dynamic characteristics of the injection system. Actual Diesel engines employ injector characterized by micro-orifices operating at injection pressure till 20MPa. These main injection characteristics resulted in the critical relation between engine performance and injector hole shape. In the present study, the authors' attention was focused on the hole geometry influence on the main injector fluid dynamic characteristics. At this purpose, three different nozzle hole shapes were considered: cylindrical, k, and ks nozzle shapes. Because of the lack of information available about ks-hole real geometry, firstly it was completely characterized by the combined use of two non-destructive techniques. Secondly, all the three nozzle layouts were characterized from the fluid dynamic point of view by a fully transient CFD multiphase simulation methodology previously validated by the authors against experimental results. The experimental characterization of the ks-hole geometry was a mandatory task to assure a good numerical simulation accuracy. From the fluid dynamic point of view, the three nozzle layouts were compared by the average fluid dynamic conditions recorded on the nozzle hole outlet sections and by the cavitating flow evolution inside the injector hole themselves. Copyright © 2013 SAE International. Source


Ponti F.,University of Bologna | Ravaglioli V.,University of Bologna | De Cesare M.,Magneti Marelli Powertrain SPA
Journal of Engineering for Gas Turbines and Power | Year: 2015

Turbocharging technique, together with engine downsizing, will play a fundamental role in the near future as a way to reach the required maximum performance while reducing engine displacement and, consequently, CO2 emissions. However, performing an optimal control of the turbocharging system is very difficult, especially for small engines fitted with a low number of cylinders. This is mainly due to the high turbocharger operating range and to the fact that the flow through compressor and turbine is highly unsteady, while only steady-flow maps are usually provided by the manufacturer. In addition, in passenger cars applications, it is usually difficult to optimize turbocharger operating conditions because of the lack of information about pressure/temperature in turbine upstream/downstream circuits and turbocharger rotational speed. This work presents a methodology suitable for instantaneous turbocharger rotational speed determination through a proper processing of the signal coming from an accelerometer mounted on the compressor diffuser or a microphone faced to the compressor. The presented approach can be used to evaluate turbocharger speed mean value and turbocharger speed fluctuation (due to unsteady flow in turbine upstream and downstream circuits), which can be correlated to the power delivered by the turbine. The whole estimation algorithm has been developed and validated for a light-duty turbocharged common-rail diesel engine mounted in a test cell. Nevertheless, the developed methodology is general and can be applied to different turbochargers, both for spark ignited and diesel applications. Copyright © 2015 by ASME. Source


Ponti F.,University of Bologna | Ravaglioli V.,University of Bologna | Moro D.,University of Bologna | De Cesare M.,Magneti Marelli Powertrain SPA
SAE Technical Papers | Year: 2012

Future regulations on pollutant emissions will impose a drastic cut on Diesel engines out-emissions. For this reason, the development of closed-loop combustion control algorithms has become a key factor in modern Diesel engine management systems. Diesel engines out-emissions can be reduced through a highly premixed combustion portion in low and medium load operating conditions. Since low-temperature premixed combustions are very sensitive to in-cylinder thermal conditions, the first aspect to be considered in newly developed Diesel engine control strategies is the control of the center of combustion. In order to achieve the target center of combustion, conventional combustion control algorithms correct the measured value varying main injection timing. A further reduction in engine-out emissions can be obtained applying an appropriate injection strategy. Modern Diesel engine injection systems allow designing injection patterns with many degrees of freedom, due to the large number of tuneable injection parameters (such as start and duration of each injection). Each variation of the injection parameters will affect and alter the whole combustion process and, consequently, pollutant emissions production. Furthermore, injection parameters variations have a strong influence on other quantities that are related to combustion process effectiveness, such as noise radiated by the engine. This work discusses the correlations existing between in cylinder pressure and the acoustic emission radiated by the engine. In order to set up the correlations that allow noise prediction starting from in-cylinder pressure measurement, several experimental tests have been performed, both in steady state and transient conditions, on a Diesel engine mounted in a test cell. Each operating condition was run both activating and deactivating pre-injections. As it is well known, in several low load conditions, pre-injections deactivation produces a decrease in pollutant emissions production (especially in particulate matter) and a simultaneous increase in engine noise. The investigation of the correlation between combustion process and engine noise can be used to set up a closed-loop algorithm for optimal combustion control based on engine noise prediction. Copyright © 2012 SAE International. Source


Ponti F.,University of Bologna | Ravaglioli V.,University of Bologna | Corti E.,University of Bologna | Moro D.,University of Bologna | Cesare M.,Magneti Marelli Powertrain SPA
SAE International Journal of Engines | Year: 2014

The optimization of turbocharging systems for automotive applications has become crucial in order to increase engine performance and meet the requirements for pollutant emissions and fuel consumption reduction. Unfortunately, performing an optimal turbocharging system control is very difficult, mainly due to the fact that the flow through compressor and turbine is highly unsteady, while only steady flow maps are usually provided by the manufacturer. For these reasons, one of the most important quantities to be used onboard for optimal turbocharger system control is the rotational speed fluctuation, since it provides information both on turbocharger operating point and on the energy of the unsteady flow in the intake and exhaust circuits. This work presents a methodology that allows determining the instantaneous turbocharger rotational speed through a proper frequency processing of the signal coming from one accelerometer mounted on the turbocharger compressor. Consequently, the developed algorithm can be used to determine both rotational speed mean value and the amplitude of speed fluctuations that are caused by unsteady flows. From this last evaluated quantity, it is also possible to obtain an estimation of power delivered by the turbine, that might be used for control and diagnostic purposes. The whole estimation algorithm has been developed and validated for a light duty turbocharged Diesel engine installed in a test cell at the University of Bologna. This paper reports the experimental layout used in this work and the accuracy obtained applying the speed fluctuations estimation procedure to the turbocharged Diesel engine under study. © 2014 SAE International. Source


Ponti F.,University of Bologna | Ravaglioli V.,University of Bologna | De Cesare M.,Magneti Marelli Powertrain SPA
Journal of Engineering for Gas Turbines and Power | Year: 2016

Optimal combustion control has become a key factor in modern automotive applications to guarantee low engine out emissions and good driveability. To meet these goals, the engine management system has to guarantee an accurate control of torque delivered by the engine and optimal combustion phasing. Both quantities can be calculated through a proper processing of in-cylinder pressure signal. However, in-cylinder pressure onboard installation is still uncommon, mainly due to problems related to pressure sensors' reliability and cost. Consequently, the increasing request for combustion control optimization spawned a great amount of research in the development of remote combustion sensing methodologies, i.e., algorithms that allow extracting useful information about combustion effectiveness via low-cost sensors, such as crankshaft speed, accelerometers, or microphones. Based on the simultaneous acquisition of two crankshaft speed signals, this paper analyses the information that can be extracted about crankshaft's torsional behavior through a proper processing of the acquired signals. In particular, the correlations existing between such information and indicated quantities (torque delivered by the engine and combustion phasing) have been analyzed. In order to maximize the signal-tonoise ratio, each speed measurement has been performed at an end of the crankshaft, i.e., in correspondence of the flywheel and the distribution wheel. The presented approach has been applied to a light-duty L4 diesel engine mounted in a test cell. Nevertheless, the methodology is general, and it can be applied to engines with a different number of cylinders, both compression ignition (CI) and spark ignition (SI). © 2016 by ASME. Source

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