1,721,015 research outputs found
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
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 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
Analysis of combustion and emissions in a EURO V Diesel engine by means of a refined quasi-dimensional multizonediagnostic model
No full textFast estimation of combustion metrics in DI diesel engines for control-oriented applications
No full textThe present work has been focused on the development of low-throughput semi-empirical models to predict the peak firing pressure, indicated mean effective pressure and brake mean effective pressure in direct injection diesel engines. The models have been calibrated and assessed on a 1.6L GM Euro 6 diesel engine, on the basis of the results of experimental tests conducted at a dynamic test bench at GMPT-E (General Motors Powertrain-Europe). Model validation was carried out over ‘‘New European Driving Cycle" and ‘‘Worldwide Harmonized Light vehicle Test Procedure" missions. The performance of the semi-empirical models has been compared, in terms of prediction accuracy, robustness, inversion efficiency and computational expense, with that of a previously developed real-time physical combustion model. The thus developed semi-empirical models are characterized by a very low computational effort, and are therefore suitable for the development of innovative feed-forward control algorithms in the Engine Control Unit
Numerical and experimental investigation on a conical poppet relief valve with flow force compensation
No full textNumerical and experimental investigations have been carried out in order to study the effect of the poppet geometry on the flow-pressure characteristic of a direct acting pressure relief valve, which is equipped with a flow deflector for flow force compensation. A dynamic 3D-CFD model was built in ANSYS Fluent™, which is capable of simulating the interaction between the fluid flow and the poppet dynamics by means of mesh deformation and of a user-defined function (UDF). This model was applied to predict the flow-pressure characteristics of the valve for different spring preload settings and deflector geometries. The simulated curves were validated using experimental data acquired at FPRL (Fluid Power Research Laboratory) at the Politecnico di Torino, and an excellent agreement was found. The CFD model was then used to predict the effect of geometric parameters of the poppet, such as the cone angle and the position of the deflector. Finally, a 0D model has been developed in order to predict the flow forces; this model requires very few calibration points using 3D-CFD simulations, and can easily be implemented in lumped parameter simulation tools. It was found that this model leads to a satisfactory prediction of the flow-pressure characteristic of the valve
Robust equivalent consumption-based controllers for a dual-mode diesel parallel HEV
No full textNew equivalent consumption minimization strategy (ECMS) tools have been developed and applied to
identify the optimal control strategy of a dual-mode parallel hybrid electric vehicle equipped with a
compression-ignition engine. In this architecture, the electric machine is coupled to the engine through
either a single-speed gearbox (torque-coupling) or a planetary gear set (speed-coupling).
One of the main novelties of the present study concerns the definition of the instantaneous equivalent
consumption (EC) function, which takes into account not only fuel consumption (FC) and the energy flow
through the electric components, but also NO
x
emissions, battery aging, and the battery SOC.
The EC function has been trained using a cross-validation machine-learning technique, based on a
genetic algorithm, where the training data set has been selected in order to maximize performances over
a testing data set. The adoption of this technique, in conjunction with the new definition of EC, have led to
the identification of very robust controllers, which provide an accurate control for different driving sce-
narios, even when the EC function is not specifically trained on the same missions over which it is tested.
To this aim, a data set of fifty driving cycles and six user-defined missions, which cover a total distance of
70–100 km, has been considered as a training driving set.
The ECMS controllers can be implemented in a vehicle control unit, and their performance has resulted
to be close to that of a dynamic programming tool, which has here been used as benchmark, over a large
set of different missions, without need for feedback control on the battery SOC or driving pattern
prediction
Layout design and energetic analysis of a complex diesel parallel hybrid electric vehicle
No full textThe present paper is focused on the design, optimization and analysis of a complex parallel hybrid electric vehicle, equipped with two electric machines on both the front and rear axles, and on the evaluation of its potential to reduce fuel consumption and NOx emissions over several driving missions. The vehicle has been compared with two conventional parallel hybrid vehicles, equipped with a single electric machine on the front axle or on the rear axle, as well as with a conventional vehicle. All the vehicles have been equipped with compression ignition engines.
The optimal layout of each vehicle was identified on the basis of the minimization of the overall powertrain costs during the whole vehicle life. These costs include the initial investment due to the production of the components as well as the operating costs related to fuel consumption and to battery depletion.
Identification of the optimal powertrain control strategy, in terms of the management of the power flows of the engine and electric machines, and of gear selection, is necessary in order to be able to fully exploit the potential of the hybrid architecture.
To this end, two global optimizers, one of a deterministic nature and another of a stochastic type, and two real-time optimizers have been developed, applied and compared.
A new mathematical technique has been developed and applied to the vehicle simulation model in order to decrease the computational time of the optimizers. First, the vehicle model equations were written in order to allow a coarse time grid to be used, then, the control variables (i.e., power flow and gear number) were discretized, and the values of the main model variables were evaluated and stored in a matrix (referred to as configuration matrix), for all the possible combinations of control variables and for each time node, before the optimization process. In this way, the optimizers can read the actual values of the relevant variables from the pre-processed data, instead of calculating them iteratively during the optimization stage. The performance of the hybrid vehicles has been evaluated over several driving missions, including the NEDC, the FTP, the AUDC, the ARDR and the AMDC, and a detailed energetic analysis has been carried out in order to clearly identify the key operating modes that contribute most to the fuel consumption and NOx emission savings of the different hybrid architectures
Development of a pressure-based technique to control IMEP and MFB50 in a 3.0L diesel engine
Full text linkA pressure-based technique for the control of IMEP (Indicated Mean Effective Pressure) and MFB50 (crank angle at which 50% of fuel mass fraction has burned) has been developed, assessed and tested by means of MiL (Model-in-the-Loop) on a 4 cylinder 3.0L Euro VI diesel engine.
The activity was carried out in the frame of a research project in collaboration with FPT Industrial.
The developed controller is of the closed-loop type. It receives, as input, the desired targets of IMEP and MFB50 for each cycle and cylinder and performs a cycle-by-cycle and cylinder-to-cylinder correction of the injected fuel quantity of the main pulse (qmain) and of the start of injection of the main pulse (SOImain), in order to reduce the deviation between the actual and target values of IMEP and MFB50, respectively. The method is referred to as “pressure-based” since it requires the measurement of the in-cylinder pressure trace for each cylinder in order to extract the actual values of IMEP and MFB50. In fact, the actual IMEP value can be estimated by integrating the pressure signal with respect to the in-cylinder volume. At the same time, the actual MFB50 value can be extracted from the heat release curve, which is obtained from the in-cylinder pressure trace by using a single-zone heat release model. The proposed control technique has been developed in Simulink environment, and has been assessed and tested on an engine emulator which is constituted by a GT-power model of the 3.0L diesel engine.
The controller has been tested in transient operation over a load ramp profile at different engine speeds and over a WHTC interval, and demonstrated to have a good potential for IMEP and MFB50 control, since it is characterized by a fast response and a limited overshoot behavior
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