Calculation of Intake Oxygen Concentration through Intake CO2 Measurement and Evaluation of Its Effect on Nitrogen Oxide Prediction Accuracy in a Heavy-Duty Diesel Engine

A new procedure, based on measurement of intake CO2 concentration and ambient humidity was developed and assessed in this study for different diesel engines in order to evaluate the oxygen concentration in the intake manifold. Steady-state and transient datasets were used for this purpose. The method is very fast to implement since it does not require any tuning procedure and it involves just one engine-related input quantity. Moreover, its accuracy is very high since it was found that the absolute error between the measured and predicted intake O2 levels is in the ±0.15% range. The method was applied to verify the performance of a previously developed NOx model under transient operating conditions. This model had previously been adopted by the authors during the IMPERIUM H2020 EU project to set up a model-based controller for a heavy-duty diesel engine. The performance of the NOx model was evaluated considering two cases in which the intake O2 concentration is either derived from engine-control unit sub-models or from the newly developed method. It was found that a significant improvement in NOx model accuracy is obtained in the latter case, and this allowed the previously developed NOx model to be further validated under transient operating conditions

Comparison of physics-based, semi-empirical and neural network-based models for model-based combustion control in a 3.0 L diesel engine

A comparison of four different control-oriented models has been carried out in this paper for the simulation of the main combustion metrics in diesel engines, i.e., combustion phasing, peak firing pressure, and brake mean effective pressure. The aim of the investigation has been to understand the potential of each approach in view of their implementation in the engine control unit (ECU) for onboard combustion control applications. The four developed control-oriented models, namely the baseline physics-based model, the artificial neural network (ANN) physics-based model, the semi-empirical model, and direct ANN model, have been assessed and compared under steady-state conditions and over the Worldwide Harmonized Heavy-duty Transient Cycle (WHTC) for a Euro VI FPT F1C 3.0 L diesel engine. Moreover, a new procedure has been introduced for the selection of the input parameters. The direct ANN model has shown the best accuracy in the estimation of the combustion metrics under both steady-state/transient operating conditions, since the root mean square errors are of the order of 0.25/1.1 deg, 0.85/9.6 bar, and 0.071/0.7 bar for combustion phasing, peak firing pressure, and brake mean effective pressure, respectively. Moreover, it requires the least computational time, that is, less than 50 µs when the model is run on a rapid prototyping device. Therefore, it can be considered the best candidate for model-based combustion control applications

A real time zero-dimensional diagnostic model for the calculation of in-cylinder temperatures, HRR and nitrogen oxides in diesel engines

A 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 real time zero-dimensional diagnostic model for the calculation of in-cylinder temperatures, HRR and nitrogen oxides in diesel engines

A 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)

Optimization of the layout and control strategy for parallel through-the-road hybrid electric vehicles

This paper describes the optimization of the layout and of the control strategy of through-the-road (TTR) parallel hybrid electric vehicles equipped with two compression-ignition engines that feature different values of maximum output power. First, a tool has been developed to define the optimal layout of each TTR vehicle. This is based on the minimization of the powertrain and fuel cost over a 10-year time span, taking into account the fuel consumption. Several performance requirements are guaranteed during the optimization, namely maximum vehicle velocity, 0-100 km/h acceleration time, gradeability and the all-electric range. A benchmark optimizer that is based on the dynamic programming theory has been developed to identify the optimal working mode and the gear number, which are the control variables of the problem. A mathematical technique, based on the pre-processing of a configuration matrix, has been developed in order to speed up the calculation time. After the layout optimization, the potential of the two identified hybrid vehicles in improving the fuel economy, compared with the conventional vehicle, has been analyzed and discussed over several driving missions, i.e., the New European Driving Cycle, the Artemis Urban Driving Cycle, the Artemis Rural Driving Cycle, the Artemis Motorway Driving Cycle and the Federal Test Procedure. The contributions related to the vehicle electrification and to the control strategy were identified separately. Finally, a real-time optimizer has also been developed, which is based on the instantaneous maximization of an equivalent powertrain efficiency

Muscle reinnervation\u2014I. Restoration of transmitter release mechanisms

Following sciatic nerve crush the restoration of neuromuscular transmission in the extensor digitorum longus muscle of rat proceeds in a well defined manner: 1. (a) as soon as the nerve-muscle contact is reformed, a subthreshold end-plate potential is recorded; no 'non-transmitting stage' is observed; 2. (b) 24hours later muscle action potentials are induced by nerve stimulation; 3. (c) miniature end-plate potentials are absent or very rare at the newly reinnervated end-plates; their frequency returns to normal in about 4 weeks; 4. (d) the frequency is also very much reduced in 30 mM K+ and hypertonic solutions and recovers slowly, in 4 and 5 weeks, respectively, while black widow spider venom is from the beginning as powerful as in normal neuromuscular junctions; 5. (e) at the early stages of reinnervation the Ca2+-dependent release mechanisms are much stronger than control cases, while the Ca2+-independent mechanisms are weaker and recover in 5 weeks. The gradual reassembly and restoration of neurotransmitter release mechanisms of the extensor digitorum longus nerve terminal indicate the complexity of pre-synaptic ending organization

Effects of Rail Pressure, Pilot Scheduling and EGR Rate on Combustion and Emissions in Conventional and PCCI Diesel Engines

In Diesel engines the optimization of engine-out emissions, combustion noise and fuel consumption requires the experimental investigation of the effects of different injection strategies as well as of a large number of engine operating variables, such as scheduling of pilot and after pulses, rail pressure, EGR rate and swirl level. Due to the high number of testing conditions involved full factorial approaches are not viable, whereas Design of Experiment techniques have demonstrated to be a valid methodology. However, the results obtained with such techniques require a subsequent critical analysis, so as to investigate the cause and effect relationships between the set of engine operating variables and the combustion process characteristics that affect pollutant formation, noise of combustion and engine efficiency. To this purpose, the zero-dimensional multizone diagnostic combustion model developed at ICEAL was applied for the combustion and emission formation analysis in two different diesel engines, for various sets of injection strategies and engine operating parameters. The experimental data were acquired at the highly dynamic test rig of ICEAL, both in a EURO V low compression ratio diesel engine with a twin-stage turbocharger, equipped with piezoelectric injectors, and in a PCCI low compression ratio diesel engine equipped with solenoid injectors. The model results were discussed and reported in the well known ϕ-T diagrams, which give a synthetic representation of the local thermodynamic charge conditions during the mixture formation and premixed diffusion combustion processes. The rail pressure increase was found to be an effective means to improve fuel-charge premixing and to lower the average local equivalence ratio of the charge during premixed combustion, so leading to a decrease in soot formation. As regards the effects of cooled high-pressure EGR on combustion, it was shown that an increase of its rate does not significantly affect the average equivalence ratio during premixed combustion, which is associated to the soot formation rate. Finally, a proper calibration of the dwell-time between pilot and main injection, so as to have the main injection pulse center-of-gravity phased in correspondence to the start of pilot burning, resulted to produce a reduction of CO and soot emissions higher than 50% with respect to baseline case, without any deterioration of NOx emissions

Innovative Multizone Premixed-Diffusion Combustion Model for Performance and Emission Analysis in Conventional and PCCI Diesel Engines

A new multizone premixed-diffusion combustion model was developed, assessed and applied to the analysis of the burning process and emission formation in two different DI diesel engines, one working with a conventional combustion system and the other with a Premixed Charge Compression Ignition (PCCI) one. The combustion chamber was split into a liquid fuel zone, an unburned gas zone, a rich mixture of fuel vapor and unburned gas, with the related premixed burned-gas zone, and several diffusive burned-gas zones. All of these are treated as homogeneous. Basically, according to a combustion mechanism close to the one of Dec, a fuel rich zone is generated first, giving rise to a premixed flame surrounding the fuel-vapor/air mixture at the liquid-jet tip. This forms a plume, which entrains the oxygen required to oxidate the combustion products at its periphery, and thus completes its oxidation in a nearly stoichiometric diffusion flame, consequent to an unburned gas induced mass dilution. The computed thermo-dynamic and thermo-chemical properties in the burned gas zones allowed the post-processing analysis of nitric oxide (NO), particulate matter (PM) and carbon monoxide (CO) formation. The model calibration was made by comparing the experimentally determined engine combustion efficiency to the combustion efficiency that was calculated by applying the energy conservation equation to the whole cylinder charge. The model was tested and assessed for two distinct commercial-type 16V, DI Common Rail (CR) diesel engines. For the conventional combustion engine, the model was applied to the heat release and emission formation analysis in a NO - PM trade-off mode, by changing the EGR mass rate. In particular, in order to estimate its effectiveness and robustness, the model was calibrated on the test condition with the highest EGR level and the calibration parameters were kept constant when lower EGR rate conditions were investigated. In addition, the model was used to analyze the combustion process at full load conditions, for different engine speeds. For the other engine, an investigation in PCCI combustion mode was carried out. The transition from conventional to PCCI mode was made by strongly increasing the EGR rate. With reference to NO emissions, the model outcomes showed an excellent agreement with experimental data for all test conditions, and good results were also obtained for the prediction of CO and PM emission levels. It was ascertained that higher local A/F ratios were required in PCCI combustion mode than in the conventional one