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Development of a Novel Machine Learning Methodology for the Generation of a Gasoline Surrogate Laminar Flame Speed Database under Water Injection Engine Conditions

SAE International Journal of Fuels and Lubricants

NAIS S.r.l., Italy-Claudio Forte
University of Bologna, Italy-Leonardo Pulga, Gian Marco Bianchi, Matteo Ricci, Giulio Cazzoli
  • Journal Article
  • 04-13-01-0001
Published 2019-11-19 by SAE International in United States
The water injection is one of the technologies assessed in the development of new internal combustion engines fulfilling new emission regulation and policy on Auxiliary Emission Strategy assessment. Besides all the positive aspects about the reduction of mixture temperature at top dead center and exhaust gases temperature at turbine inlet, it is well known that the water vapor acts as a mixture diluter, thus diminishing the reactants burning rate. A common methodology employed for the Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics (RANS CFD) simulation of the reciprocating internal combustion engines’ turbulent combustion relies on the flamelet approach, which requires knowledge of the Laminar Flame Speed (LFS) and thickness. Typically, these properties are calculated by means of correlation laws, but they do not keep into account the presence of water mass fraction. A more precise methodology for the definition of both the LFS and thickness is thus required. The interrogation of a previously computed look-up table of such properties during run time seems to be a suitable and more accurate method than using correlations. In order to…
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Evaluation of Water and EGR Effects on Combustion Characteristics of GDI Engines Using a Chemical Kinetics Approach

NAIS-Claudio Forte
University of Bologna-Giulio Cazzoli, Gian Marco Bianchi, Stefania Falfari, Matteo Ricci
  • Technical Paper
  • 2019-24-0019
Published 2019-09-09 by SAE International in United States
The modern spark ignition engines, due to the introduced strategies for limiting the consumption without reducing the power, are sensitive to both the detonation and the increase of the inlet turbine temperature. In order to reduce the risk of detonation, the use of dilution with the products of combustion (EGR) is an established practice that has recently improved with the use of water vapor obtained via direct or indirect injection.The application and optimization of these strategies cannot ignore the knowledge of physical quantities characterizing the combustion such as the laminar flame speed and the ignition delay, both are intrinsic property of the fuel and are function of the mixture composition (mixture fraction and dilution) and of its thermodynamic conditions.The experimental measurements of the laminar flame speed and the ignition delay available in literature, rarely report the effects of dilution by EGR or water vapor. To overcome the limitations of the experimentation is possible to predict the value of the ignition delay using numerical models based on chemical kinetics theory. The increased performance of computing systems…
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Numerical Aspects Affecting Heat Transfer in ICE Applications and Definition of a Temperature Wall Function Accounting for the Boundary Layer Compressibility

SAE International Journal of Engines

DIN-University of Bologna, Italy-Leonardo Pulga, Gian Marco Bianchi, Stefania Falfari
Nais s.r.l., Italy-Claudio Forte
  • Journal Article
  • 03-12-05-0034
Published 2019-08-22 by SAE International in United States
The heat transfer phenomena in Internal Combustion Engines (ICEs) are one of the main research topics that need to be addressed to enhance the performance in terms of power, efficiency, emissions and reliability. The present study is focused on the evaluation of the in-cylinder heat fluxes through the use of Computational Fluid Dynamic (CFD) simulations, with a wall function approach. In particular, the aim of this work is to present a new fully non-isothermal wall function obtained from the one-dimensional (1-D) energy balance equation for turbulent flows in the boundary layers, specifying all the steps and assumptions which have carried to the final fully compressible formulation. The new proposed wall function has been validated against experimental data of the General Motors (GM) Pancake Engine, representative of low Brake Mean Effective Pressure (bmep) operating point, comparing the results with other existing wall functions. With the objective of a mesh independency analysis, the wall functions considered have been tested with three different grids, varying the height of the first layer. Globally, it has been found that the…
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Water Injection Applicability to Gasoline Engines: Thermodynamic Analysis

NAIS srl-Claudio Forte
University of Bologna-Stefania Falfari, Gian Marco Bianchi, Giulio Cazzoli, Matteo Ricci
Published 2019-04-02 by SAE International in United States
The vehicle WLTP and RDE homologation test cycles are pushing the engine technology toward the implementation of different solutions aimed to the exhaust gases emission reduction. The tightening of the policy on the Auxiliary Emission Strategy (A.E.S.), including those for the engine component protection, faces the Spark Ignited (S.I.) engines with the need to replace the fuel enrichment as a means to cool down both unburnt mixture and exhaust gases to accomplish with the inlet temperature turbine (TiT) limit. Among the whole technology solutions conceived to make SI engine operating at lambda 1.0 on the whole operation map, the water injection is one of the valuable candidates. Despite the fact that the water injection has been exploited in the past, the renewed interest in it requires a deep investigation in order to outcome its potential as well as its limits. Many experimental campaigns have been performed while only few researches have deeply investigated the effect of the water injection on the air-fuel mixture under engine operating conditions. Since the experiments perform like a black box…
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A Chemical-Kinetic Approach to the Definition of the Laminar Flame Speed for the Simulation of the Combustion of Spark-Ignition Engines

NAIS-Claudio Forte
University of Bologna-Giulio Cazzoli, Gian Marco Bianchi, Stefania Falfari
Published 2017-09-04 by SAE International in United States
The laminar burning speed is an important intrinsic property of an air-fuel mixture determining key combustion characteristics such as turbulent flame propagation. It is a function of the mixture composition (mixture fraction and residual gas mass fraction) and of the thermodynamic conditions.Experimental measurements of Laminar Flame Speeds (LFS) are common in literature, but initial pressure and temperature are limited to low values due to the test conditions: typical pressure values for LFS detection are lower than 25 bar, and temperature rarely exceeds 550 K.Actual trends in spark ignition engines are to increase specific power output by downsizing and supercharging, thus the flame front involves even more higher pressure and temperature since the beginning of combustion. The most widespread models used to extrapolate the experimental data to the engine like conditions are derived from that of Metghalchi and Keck, but they often fail to correctly predict LFS values outside the experimental space.Thanks to the development of accurate chemical kinetic models together with the increase of computer performance, it is possible to numerically predict the laminar flame…
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A Control-Oriented Knock Intensity Estimator

SAE International Journal of Engines

University of Bologna-Enrico Corti, Claudio Forte, Gian Marco Bianchi, Lorenzo Zoffoli
  • Journal Article
  • 2017-24-0055
Published 2017-09-04 by SAE International in United States
The performance optimization of modern Spark Ignition engines is limited by knock occurrence: heavily downsized engines often are forced to work in the Knock-Limited Spark Advance (KLSA) range. Knock control systems monitor the combustion process, allowing to achieve a proper compromise between performance and reliability. Combustion monitoring is usually carried out by means of accelerometers or ion sensing systems, but recently the use of cylinder pressure sensors is also becoming frequent in motorsport applications. On the other hand, cylinder pressure signals are often available in the calibration stage, where SA feedback-control based on the pressure signal can be used to avoid damages to the engine during automatic calibration.A predictive real-time combustion model could help optimizing engine performance, without exceeding the allowed knock severity. Several knock models are available in the literature: most of those proposed for real-time applications are single zone or two-zone models, grounded on more complex CFD simulations. However, since the knock phenomenon is influenced by several factors, the real-time determination of KLSA requires the model to be adapted to the engine actual…
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Assessment of Advanced SGS Models for LES Analysis of ICE Wall-Bounded Flows - Part I: Basic Test Case

SAE International Journal of Engines

University of Bologna-Cristian Catellani, Gian Marco Bianchi, Stefania Falfari, Giulio Cazzoli, Claudio Forte
  • Journal Article
  • 2016-01-9041
Published 2016-03-14 by SAE International in United States
Large Eddy Simulation (LES) represents nowadays one of the most promising techniques for the evaluation of the dynamics and evolution of turbulent structures characterizing internal combustion engines (ICE). In the present paper, subdivided into two parts, the capabilities of the open-source CFD code OpenFOAM® v2.3.0 are assessed in order to evaluate its suitability for engine cold flow LES analyses. Firstly, the code dissipative attitude is evaluated through an inviscid vortex convection test to ensure that the levels of numerical dissipation are compatible with LES needs. Quality and completeness estimators for LES simulations are then proposed. In particular the Pope M parameter is used as a LES completeness indicator while the LSR parameter provides useful insights far calibrating the grid density. Other parameters such as the two-grid LESIQk index are also discussed. Then advanced SGS models such as the dynamic WALE and the Sigma models are compared with models traditionally used for LES simulations of ICE wall-bounded flows, i.e. the dynamic Smagorinsky and the WALE models. The proposed SGS models have been implemented in the open-source…
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Analysis of the Mixture Formation at Partial Load Operating Condition: The Effect of the Throttle Valve Rotational Direction

University of Bologna-Stefania Falfari, Claudio Forte, Gian Bianchi, Giulio Cazzoli, Cristian Catellani
University of Perugia-Lucio Postrioti, Fabrizio Ottobre
Published 2015-09-06 by SAE International in United States
In the next incoming future the necessity of reducing the raw emissions leads to the challenge of an increment of the thermal engine efficiency. In particular it is necessary to increase the engine efficiency not only at full load but also at partial load conditions. In the open literature very few technical papers are available on the partial load conditions analysis. In the present paper the analysis of the effect of the throttle valve rotational direction on the mixture formation is analyzed. The engine was a PFI 4-valves motorcycle engine. The throttle valve opening angle was 17.2°, which lays between the very partial load and the partial load condition. The CFD code adopted for the analysis was the FIRE AVL code v. 2013.2. The exhaust, intake and compression phases till TDC were simulated: inlet/outlet boundary conditions from 1D simulations were imposed. The injection system operation was experimentally investigated in terms of spray shape and drop sizing and velocity for a proper tuning of the numerical model. The injection process was modelled and the final results…
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Relating Knocking Combustions Effects to Measurable Data

SAE International Journal of Engines

University of Bologna-Enrico Corti, Claudio Forte, Gian Marco Bianchi, Davide Moro
  • Journal Article
  • 2015-24-2429
Published 2015-09-06 by SAE International in United States
Knocking combustions heavily influence the efficiency of Spark Ignition engines, limiting the compression ratio and sometimes preventing the use of Maximum Brake Torque (MBT) Spark Advance (SA).A detailed analysis of knocking events can help in improving the engine performance and diagnostic strategies. An effective way is to use advanced 3D Computational Fluid Dynamics (CFD) simulation for the analysis and prediction of the combustion process. The standard 3D CFD approach based on RANS (Reynolds Averaged Navier Stokes) equations allows the analysis of the average engine cycle. However, the knocking phenomenon is heavily affected by the Cycle to Cycle Variation (CCV): the effects of CCV on knocking combustions are then taken into account, maintaining a RANS CFD approach, while representing a complex running condition, where knock intensity changes from cycle to cycle. The focus of the numerical methodology is the statistical evaluation of the local air-to-fuel and turbulence distribution at the spark plugs and their correlation with the variability of the initial stages of combustion.CFD simulations have been used to reproduce knock effect on the in-cylinder pressure…
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The Effect of the Throttle Valve Rotational Direction on the Tumble Motion at Different Partial Load Conditions

University of Bologna-Stefania Falfari, Gian Marco Bianchi, Giulio Cazzoli, Federico Brusiani, Claudio Forte, Cristian Catellani
Published 2015-04-14 by SAE International in United States
In PFI and GDI engines the tumble motion is the most important charge motion for enhancing the in-cylinder turbulence level at ignition time close to the spark plug position. In the open literature different studies were reported on the tumble motion, experimental and not. In the present paper the research activity on the tumble generation at partial load and very partial load conditions was presented. The added value of the analysis was the study of the effect of the throttle valve rotational direction on the tumble motion and the final level of turbulence at the ignition time close to the spark plug location. The focus was to determine if the throttle rotational direction was crucial for the tumble ratio and the turbulence level.The analyzed engine was a PFI 4-valves motorcycle engine. The engine geometry was formed by the intake duct and the cylinder. The CFD code was FIRE AVL code 2013.1. The intake and the compression phases till TDC were simulated: inlet boundary conditions from 1D simulations were imposed. The modelled fluid was only air…
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