Stefano Fontanesi

Stefano Fontanesi
Università degli Studi di Modena e Reggio Emilia | UNIMO · Department of Engineering "Enzo Ferrari"

PhD

About

128
Publications
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1,750
Citations

Publications

Publications (128)
Article
Full-text available
Ammonia/hydrogen mixtures are among the most promising solutions to decarbonize the transportation and energy sector. The implementation of these alternative energy carriers in practical systems requires developing suitable numerical tools, able to estimate their burning velocities as a function of both thermodynamic conditions and mixture quality....
Article
Knock has historically been one of the main limitations on spark ignition (SI) engine compression ratio and hence efficiency. The trend to downsizing or rightsizing in recent years, driven by ever-reducing carbon dioxide (CO2) targets, has increased the relevance of the knock limit for typical engine operating conditions. Even for scenarios where a...
Article
Knock has been studied by internal combustion engine researchers for well over a century. It remains perhaps the main limit on spark-ignition engine efficiency today. In an engine development environment, knock is typically described through quantification of the high-frequency signal content of cylinder pressure measurements. A cylinder pressure t...
Article
In this paper, a three-dimensional, multi-physics and multi-phase CFD model is presented and validated on straight single-channel configurations to analyse the influence of the channel/rib width ratio. In the first part, two cases with wide/narrow channel/rib spacing are reproduced from a literature campaign including neutron radiography (NRG) meas...
Article
In Gasoline Direct Injection (GDI) engines, the secondary break-up plays a significant role in air–fuel mixing. In fact, spray granulometry affects evaporation rate, liquid penetration and plume morphology. Operating pressures and temperatures of both liquid and gaseous phases strongly influence the droplet disruption mechanism in the combustion ch...
Article
The paper proposes a methodology to perform sloshing analyses through multidimensional Computational Fluid Dynamics (CFD), with particular focus on a lubricant tank of a high-performance sports car. Lubricant tanks are usually fed by a mixture of oil and air, which makes Volume of Fluid (VoF) models unsuitable for this kind of simulation. Hence, a...
Article
Fuel cells are considered a key technology to decarbonize the power generation sector, thanks to the absence of pollutants emissions related to the direct chemical-electric energy conversion, their high global efficiency, and the possibility for on-board electricity production, overcoming the storage limits of batteries. An example of the renewed i...
Article
In the present paper, a comprehensive, wall-adapted zonal URANS/LES methodology is shown for the multidimensional simulation of modern direct-injection engines. This work is the latest update of a zonal hybrid turbulence modeling approach, specifically developed by the authors for a flexible description of in-cylinder turbulent flow features with a...
Article
Full-text available
Turbulent combustion modelling in internal combustion engines (ICEs) is a challenging task. It is commonly synthetized by incorporating the interaction between chemical reactions and turbulent eddies into a unique term, namely turbulent flame speed sT. The task is very complex considering the variety of turbulent and chemical scales resulting from...
Article
Full-text available
The large-scale adoption of fuel cells system for sustainable power generation will require the combined use of both multidimensional models and of dedicated testing techniques, in order to evolve the current technology beyond its present status. This requires an unprecedented understanding of concurrent and interacting fluid dynamics, material and...
Conference Paper
The establishment of highly-diluted combustion strategies is one of the major challenges that the next generation of sustainable internal combustion engines must face. The desirable use of high EGR rates and of lean mixtures clashes with the tolerable combustion stability. To this aim, the development of numerical models able to reproduce the degre...
Article
Full-text available
Hydrogen-fueled fuel cells are considered one of the key strategies to tackle the achievement of fully-sustainable mobility. The transportation sector is paying significant attention to the development and industrialization of proton exchange membrane fuel cells (PEMFC) to be introduced alongside batteries, reaching the goal of complete de-carboniz...
Article
Convective heat transfer heavily affects both efficiency and reliability in many industrial problems. For this reason, its proper estimation is mandatory since the early design stage. 3D-CFD simulations represent a powerful tool for the prediction of the heat fluxes. This is even more true considering that typical operating conditions of many appli...
Article
Soot engine-out emissions are no longer a prerogative of Diesel engines. Emission regulations related to Gasoline units aim to curb the soot emissions along with other pollutants. In this scenario, Computational Fluid Dynamics (CFD) is a very promising research and development tool to explore the influence of engine design and operational parameter...
Article
The need for Internal Combustion Engines (ICEs) to face near-future challenges of higher efficiency and reduced emissions is leading to a renewed interest towards lean-combustion. Several operational issues are associated to lean combustion, such as an abrupt increase of combustion cycle-by-cycle variability (CCV), leading to unbearable levels of I...
Article
Particulate Matter emission is an increasing concern for engine manufacturers due to the strong limits imposed by worldwide regulations. Fuel composition plays a key role in determining the extent to which soot is formed during the combustion process. The availability of advanced multidimensional computational fluid-dynamics soot models incorporati...
Article
Nowadays, the leading driver for the development of internal combustion engines is the search for increased fuel efficiency and reduced emissions. To develop and optimize new combustion systems, a high degree of accuracy is needed in 3D-CFD simulations. In particular, detailed chemical kinetics models and fuel surrogates able to represent the main...
Conference Paper
Full-text available
The growing energy demand is inevitably accompanied by a strong increase in greenhouse gas emissions, primarily carbon dioxide. The adoption of new energy vectors is therefore seen as the most promising countermeasure. In this context, hydrogen is an extremely interesting energy carrier, since it can be used as a fuel in both conventional energy sy...
Article
Large-eddy simulation has been increasingly applied to internal combustion engine flows because of their improved potential to capture the spatial and temporal evolution of turbulent flow structures compared with Reynolds-averaged Navier Stokes simulation. Furthermore, large-eddy simulation is universally recognized as capable of simulating highly...
Article
A zonal hybrid unsteady Reynolds-averaged Navier–Stokes/large eddy simulation (URANS-LES) Zonal detached-eddy simulation (ZDES) model is applied to internal combustion engine (ICE) simulation and comparisons of predicted flow morphology and variability are carried out against on the transparent combustion chamber (TCC-III) particle image velocimetr...
Article
In the industrial practice, 3D-CFD in-cylinder simulations still largely rely on RANS turbulence models and high-Reynolds wall treatments, i.e. based on wall functions. However, the use of the latter represents a potential source of error, leading to poor estimations of shear stress and heat flux at the wall. In fact, universal laws of the wall can...
Conference Paper
Full-text available
One of the aspects that are usually neglected during the design phase of an engine is the effect of the spark plug on the flow field inside the combustion chamber. Because of the difficulties in the experimental investigation of the mutual interaction between flow alteration and early flame kernel convection effect inside the engine combustion cham...
Article
Computational fluid dynamics has become a fundamental tool for the design and development of internal combustion engines. The meshing strategy plays a central role in the computational efficiency, in the management of the moving components of the engine and in the accuracy of results. The overset mesh approach, usually referred to also as chimera g...
Article
Full-text available
In the present paper, 1D and 3D CFD models of the Darmstadt research engine undergo a preliminary validation against the available experimental dataset at motored condition. The Darmstadt engine is a single-cylinder optical research unit and the chosen operating point is characterized by a revving speed equal to 800 rpm with intake temperature and...
Article
Full-text available
Multidimensional modeling of Cycle-to-Cycle Variability (CCV) has become a crucial support for the development and optimization of modern direct-injection turbocharged engines. In that sense, the only viable modeling options is represented by scale-resolving approaches such as Large Eddy Simulation (LES) or hybrid URANS/LES methods. Among other hyb...
Conference Paper
Fuel injectors featuring differentiated hole-to-hole dimensions improve the fuel distribution in the cylinder ensuring a more efficient and cleaner combustion for GDI (Gasoline Direct Injection) engines. A proper diagnostic system able to detect the actual fuel flow rate exiting each hole of a GDI nozzle is requested in order to optimize the matchi...
Article
A novel methodology for the estimation of the mass flow rate delivered by each hole of a multi-hole GDI nozzle is presented and discussed in this paper. The proposed method is based on the measurement of the impact force of each jet and it is able to evaluate the individual hole injection rate and injected mass using the relationship between the sp...
Article
Several environment agencies worldwide have identified biofuels as a viable solution to meet the stringent targets imposed by future regulations in terms of on-road transport emissions. In the last decades, petroleum-based gasoline has been increasingly blended with oxygenated fuels, mostly ethanol. Blending ethanol with gasoline has two major effe...
Article
Pollutant regulations and fuel consumption concerns are the driving guidelines for increased thermal efficiency and specific power in current internal combustion engines. The achievement of such challenging tasks in Spark Ignition units is often limited by the onset of knock, which hinders the possibility to operate the engine with the optimal comb...
Conference Paper
Despite syngas is a promising alternative fuel for internal combustion engines (ICEs), its extensive adoption has not been adequately investigated so far. The dedicated literature offers several fundamental studies dealing with H 2 /CO blends burning at high pressure and room temperature, as well as preheated mixture at low pressure. However, these...
Article
A zonal hybridization of the RNG k-ε URANS model is proposed for the simulation of turbulent flows in internal combustion engines. The hybrid formulation is able to act as URANS, DES or LES in different zones of the computational domain, which are explicitly set by the user. The resulting model has been implemented in a commercial computational flu...
Article
Experimental techniques like particle image velocimetry provide a powerful technical support for the analysis of the spatial and temporal evolution of the flow field in internal combustion engines. Such techniques can be used to investigate both ensemble-averaged flow structures and their cyclic variations. These last are among the major causes of...
Conference Paper
The accurate representation of Internal Combustion Engine (ICE) flows via CFD is an extremely complex task: it strongly depends on a combination of highly impacting factors, such as grid resolution (both local and global), choice of the turbulence model, numeric schemes and mesh motion technique. A well-founded choice must be made in order to avoid...
Article
A numerical study using large-eddy simulations (LES) to reproduce and understand sources of cycle-to-cycle variation (CCV) in spark-initiated internal combustion engines (ICEs) is presented. Two relevantly different spark-ignition (SI) units, that is, a homogeneous-charge slow-speed singlecylinder research unit (the transparent combustion chamber (...
Presentation
Full-text available
Contribution presented at the LES for Internal Combustion Engine flows (LES4ICE) 2018 Conference
Article
In this work, the refinement of a phenomenological turbulence model developed in recent years by the authors is presented in detail. As known, reliable information about the underlying turbulence intensity is a mandatory prerequisite to predict the burning rate in phenomenological combustion models. The model is embedded under the form of “user rou...
Article
In direct injection combustion systems, the spray momentum flux measurement can provide significant insight in the fuel jet development and the in-cylinder fuel-air mixing potential. The spray momentum flux can be determined by means of the impact force method, which was proved to be completely consistent when the basic measuring hypotheses are ful...
Article
Full-text available
An integrated experimental and Large-Eddy Simulation (LES) study is presented for homogeneous premixed combustion in a spark-ignition engine, called the Transparent Combustion Chamber engine. The emphasis has been on developing strategies for making quantitative comparisons between high-speed/high-resolution optical diagnostics and LES using common...
Article
Full-text available
Hydraulic manifolds are used to realize compact circuit layouts, but may introduce high pressure losses in the system because their design is usually oriented to achieving minimum size and weight more than reducing the pressure losses. The purpose of this work is to obtain the pressure losses when the internal connections within the manifold are cr...
Article
In the recent past engine knock emerged as one of the main limiting aspects for the achievement of higher efficiency targets in modern spark-ignition (SI) engines. To attain these requirements, engine operating points must be moved as close as possible to the onset of abnormal combustions, although the turbulent nature of flow field and SI combusti...
Article
The increasing limitations in engine emissions and fuel consumption have led researchers to the need to accurately predict combustion and related events in gasoline engines. In particular, knock is one of the most limiting factors for modern SI units, severely hindering thermal efficiency improvements. Modern CFD simulations are becoming an afforda...
Article
CFD and FE tools are intensively adopted by engine manufacturers in order to prevent thermo-mechanical failures reducing time and cost-to market. The capability to predict correctly the physical factors leading to damages is hence essential for their application in the industrial practice. This is even more important for last generation SI engines,...
Article
Conventional fossil fuels are more and more regulated in terms of both engine-out emissions and fuel consumption. Moreover, oil price and political instabilities in oil-producer countries are pushing towards the use of alternative fuels compatible with the existing units. N-Butanol is an attractive candidate as conventional gasoline replacement, gi...
Article
Engine knock is one of the most limiting factors for modern Spark-Ignition (SI) engines to achieve high efficiency targets. The stochastic nature of knock in SI units hinders the predictive capability of RANS knock models, which are based on ensemble averaged quantities. To this aim, a knock model grounded in statistics was recently developed in th...
Article
Last generation spark ignition (SI) engines are characterized by a simultaneous reduction of the engine displacement and an increase of the brake power; such conflicting targets are achieved through the adoption of several techniques such as turbocharging, direct fuel injection, variable valve timing and variable port lengths. This design approach,...
Article
It is well known that 3D CFD simulations can give detailed information about fluid and flow properties in complex 3D domains while 1D CFD simulation can provide important information at a system level, i.e. about the performance of the entire engine. The drawbacks of the two simulation methods are that the former requires high computational cost wh...
Article
It is widely recognized that spatial and temporal evolution of both macro-and micro-turbulent scales inside internal combustion engines affect air-fuel mixing, combustion and pollutants formation. Particularly, in spark ignition engines, tumbling macro-structure induces the generation of a proper turbulence level to sustain the development and prop...
Article
New SI engine generations are characterized by a simultaneous reduction of the engine displacement and an increase of the brake power; such targets are achieved through the adoption of several techniques such as turbocharging, direct fuel injection, variable valve timing and variable port lengths. This design approach, called "downsizing", leads to...
Article
Engine knock is emerging as the main limiting factor for modern spark-ignition (SI) engines, facing increasing thermal loads and seeking demanding efficiency targets. To fulfill these requirements, the engine operating point must be moved as close as possible to the onset of abnormal combustion events. The turbulent regime characterizing in-cylinde...
Article
The occurrence of knock is the most limiting hindrance for modern Spark-Ignition (SI) engines. In order to understand its origin and move the operating condition as close as possible to onset of this potentially harmful phenomenon, a joint experimental and numerical investigation is the most recommended approach. A preliminary experimental activity...
Article
Full-text available
In this work, experimental data, carried out on a twin-cylinder turbocharged engine at full load operations and referred to a spark advance of borderline knock, are used to characterize the effects of cyclic dispersion on knock phenomena. 200 consecutive in-cylinder pressure signals are processed through a refined Auto-Regressive Moving Average (AR...
Article
Full-text available
The paper proposes a methodology to improve the accuracy of Volume of Fluid (VoF) multiphase problems involving liquid/gas sloshing in fuel/lubricant tanks without penalizing the computational cost of the simulations. In order to correctly track the complex trajectory of the liquid/gas interface and the presence of liquid droplets in the gas phase,...
Article
Full-text available
One of the most critical challenges for the specific power increase of turbocharged SI engines is the low end torque, limited by two aspects. First, the big size of the compressor necessary to deliver the maximum airflow does not allow high boost pressures at low speed, due to the surge line proximity. Second, the flame front velocity may become sl...
Article
The paper reports an activity aiming at characterizing cycle-to-cycle variability (CCV) of the spark-ignition (SI) process in a high performance engine. The numerical simulation of spark-ignition and of early flame kernel evolution are major challenges, mainly due to the time scales of the spark discharge process and to the reduced spatial scales o...
Article
Engine downsizing is gaining popularity in the high performance engine market sector, where a new generation of highly downsized engines with specific power outputs around or above 150 HP/litre is emerging. High-boost and downsizing, adopted to increase power density and reduce fuel consumption, have to face the increased risks of pre-ignition, kno...
Article
Cycle-to-cycle variability is numerically simulated for high-speed, full-load operation of a turbocharged gasoline direct injection engine. Large-Eddy simulation is adopted to replicate the fluctuations of the flow field affecting the turbulent combustion. Experimental data were provided at knock onset, and large-Eddy simulation was validated for t...