1,721,144 research outputs found
Indagine sperimentale sulle proprietà del moto turbolento nel cilindro di un motore diesel automobilistico mediante una innovativa tecnica anemometrica a filo caldo
No full textTesi di Dottorato di Ricerca in Energetic
A Contribution to the Analysis of Turbulence Anisotropy and Nonhomogeneity in an Open-Chamber Diesel Engine
No full textA real time zero-dimensional diagnostic model for the calculation of in-cylinder temperatures, HRR and nitrogen oxides in diesel engines
No full textA real-time zero-dimensional diagnostic combustion model has been developed and assessed to evaluate in-cylinder temperatures, HRR (heat release rate) and NOx (nitrogen oxides) in DI (Direct Injection) diesel engines under steady state and transient conditions. The approach requires very little computational time, that is, of the order of a few milliseconds, and is therefore suitable for real-time applications. It could, for example, be implemented in an ECU (Engine Control Unit) for the on-board diagnostics of combustion and emission formation processes, or it could be integrated in acquisition software installed on an engine test bench for indicated analysis. The model could also be used for post-processing analysis of previously acquired experimental data. The methodology is based on a three-zone thermodynamic model: the combustion chamber is divided into a fuel zone, an unburned gas zone and a stoichiometric burned gas zone, to which the energy and mass conservation equations are applied. The main novelty of the proposed method is that the equations can be solved in closed form, thus making the approach suitable for real-time applications. The evaluation of the temperature of burned gases allows the in-cylinder NOx concentration to be calculated, on the basis of prompt and Zeldovich thermal mechanisms. The procedure also takes into account the NOx level in the intake charge, and is therefore suitable for engines equipped with traditional short-route EGR (Exhaust Gas Recirculation) systems, and engines equipped with SCR (Selective Catalytic Reduction) and long-route EGR systems. The diagnostic model was tested on a GMPT-E Euro 5 diesel engine, under both steady-state and fast transient conditions. The experimental data were acquired at the dynamic test bench of ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino
A feed-forward approach for the real-time estimation and control of MFB50 and SOI in diesel engines
No full textFeed-forward low-throughput models have been developed to predict MFB50 and to control SOI in order to achieve a specific MFB50 target for diesel engines. The models have been assessed on a GMPT-E Euro 5 diesel engine, installed at the dynamic test bench at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino) and applied to both steady state and transient engine operating conditions. MFB50 indicates the crank angle at which 50% of the fuel mass fraction has burned, and is currently used extensively in control algorithms to optimize combustion phasing in diesel engines in real-time. MFB50 is generally used in closed-loop combustion control applications, where it is calculated by the engine control unit, cycle-by-cycle and cylinder by-cylinder, on the basis of the measured in-cylinder pressure trace, and is adjusted in order to reduce the fuel consumption, combustion noise and engine-out emissions. A feed-forward approach has been developed in this paper. This approach is capable of predicting MFB50 on the basis of several parameters, such as, the in-chamber thermodynamic conditions, the injected fuel quantities and timings, the injection pressure, the oxygen concentration and the engine speed and load. The approach has also been inverted in order to predict the start of injection required to achieve a specific MFB50 target in real time. This method can be used in model-based real-time control algorithms to adjust the engine parameters in order to prevent the occurrence of nonoptimal combustion cycles
Ignition delay prediction of multiple injections in diesel engines
No full textNew correlations have been developed to predict the ignition delay of the main and multiple pilot injections as a function of the operating conditions in diesel engines. The ignition delay was first modeled through a global-mechanism approach, which accounts for the physical and chemical contributions separately. Semi-empirical correlations were then developed to predict the ignition delay of the pilot and main pulses for model-based control applications. Interest in this kind of application has in fact increased among car manufacturers over the last few years. An experimental investigation has been set up and carried out on a Euro 5 diesel engine at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino), in order to assess the dependence of the ignition delay of each injection pulse on several parameters. The physical delay has been evaluated, with reference to the global-mechanism model, starting from a scaling law for the evaluation of the liquid length of the spray that was developed by Sandia National Laboratories. It has been verified that the physical delay depends on the charge and fuel thermodynamic conditions, as well as on the injector nozzle characteristics and injection pressure. The chemical delay, for the pilot injections, has been modeled by means of an Arrhenius-like expression that takes into account the effects of the charge density, temperature and oxygen concentration evaluated at the end of the physical delay. The chemical delay of the main injection has been modeled using a similar expression that includes an additional parameter, i.e., the total injected fuel quantity of the pilot injection shots. The thermodynamic and chemical conditions of the charge at the start of the main injection are in fact influenced to a great extent by the burning process of the pilot injection shots. The control-oriented approach, which is based on semi-empirical correlations to predict the ignition delay of the pilot and main pulses, was then developed. These correlations are robust and easy to apply, and are therefore suitable for integration with low-throughput combustion control algorithms that can be implemented in the engine control unit. Finally, the global-mechanism model and the control-oriented approach have been assessed and applied for ignition delay prediction in both steady-state and transient conditions
A control-oriented approach to estimate the injected fuel mass on the basis of the measured in-cylinder pressure in multiple injection diesel engines
Full text linkA new control-oriented methodology has been developed to estimate the injected fuel quantities, in real-time, in multiple injection DI diesel engines on the basis of the measured in-cylinder pressure. The method is based on the inversion of a predictive combustion model that was previously developed by the authors, and that is capable of estimating the heat release rate and the in-cylinder pressure on the basis of the injection rate. The model equations have been rewritten in order to derive the injected mass as an output quantity, starting from use of the measured in-cylinder pressure as input.
It has been verified that the proposed method is capable of estimating the injected mass of pilot pulses with an uncertainty of the order of ±0.15 mg/cyc, and the total injected mass with an uncertainty of the order of ±0.9 mg/cyc. The main sources of uncertainty are related to the estimation of the in-cylinder heat transfer and of the isentropic coefficient c = cp/cv.
The estimation of the actual injected quantities in the combustion chamber can represent a powerful means to diagnose the behavior of the injectors during engine operation, and offers the possibility of monitoring effects, such as injector ageing and injector coking, as well as of allowing an accurate control of the pilot injected quantities to be obtained; the latter are in fact usually characterized by a large dispersion, with negative consequences on the combustion quality and emission formation.
The approach is characterized by a very low computational time, and is therefore suitable for control-oriented applications
Analysis of combustion and emissions in a EURO V Diesel engine by means of a refined quasi-dimensional multizonediagnostic model
No full textSpeed Dependence of Turbulence Properties in a High-Squish Automotive Engine Combustion System
No full textNumerical-Experimental Study and Solutions to Reduce the Dwell Time Threshold for Fusion-Free Consecutive Injections in a Multijet Solenoid-Type C.R. System
No full textAnalysis of the Exhaust Gas Recirculation System Performance in Modern Diesel Engines
No full textExhaust gas recirculation (EGR) is extensively employed in diesel combustion engines to achieve nitrogen oxides emission targets. The EGR is often cooled in order to increase the effectiveness of the strategy, even though this leads to a further undesired impact on particulate matter and hydrocarbons. Experimental tests were carried out on a diesel engine at a dynamometer rig under steady-state speed and load working conditions that were considered relevant for the New European Driving Cycle. Two different shell and tube-type EGR coolers were compared, in terms of the pressure and temperature of the exhaust and intake lines, to evaluate thermal effectiveness and induced pumping losses. All the relevant engine parameters were acquired along EGR trade-off curves, in order to perform a detailed comparison of the two coolers. The effect of intake throttling operation on increasing the EGR ratio was also investigated. A purposely designed aging procedure was run in order to characterize the deterioration of the thermal effectiveness and verify whether clogging of the EGR cooler occurred. The EGR mass flow-rate dependence on the pressure and temperature upstream of the turbine as well as the pressure downstream of the EGR control valve was modeled by means of the expression for convergent nozzles. The restricted flow-area at the valve-seat passage and the discharge coefficient were accurately determined as functions of the valve lif
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