Papers by Gianluca D'Errico
Combustion Theory and Modelling, 2015
ABSTRACT The flame stabilisation process in turbulent non-premixed flames is not fully understood... more ABSTRACT The flame stabilisation process in turbulent non-premixed flames is not fully understood and several models have been developed to describe the turbulence–chemistry interaction. This work compares the performance of the multiple Representative Interactive Flamelet (mRIF) model, the Volume Reactor Fraction Model (VRFM), and the Well-Stirred reactor (WS) model in describing such flames. The predicted ignition delay and flame lift-off length of n-heptane sprays are compared to experimental results published within the Engine Combustion Network (ECN). All of the models predict the trend of ignition delay reasonably well. At a low gas pressure (42 bar) the ignition delay is overpredicted compared to the experimental data, but the difference between the models is not significant. However, the predicted lift-off lengths differ. At high pressure (87 bar) the difference between the models is small. All models slightly underpredict the lift-off length compared to the experimental data. At low gas pressure (42 bar) the mRIF model gives the best results. The VRFM and WS models predict excessively short lift-off lengths, but the VRFM model gives better results than the WS model. The flame structures of the models are also compared. The WS model and the VRFM model yield a well defined flame stabilisation point whereas the mRIF model does not. The flame of the mRIF model is more diffuse and the model is not able to predict flame propagation. All models were able to predict the experimental trends in lift-off and ignition delay, but certain differences between them are demonstrated.
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Combustion and Flame, 2015
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SAE Technical Paper Series, 2015
ABSTRACT Prediction of in-cylinder flows and fuel-air mixing are two fundamental pre-requisites f... more ABSTRACT Prediction of in-cylinder flows and fuel-air mixing are two fundamental pre-requisites for a successful simulation of direct-injection engines. Over the years, many efforts were carried out in order to improve available turbulence and spray models. However, enhancements in physical modeling can be drastically affected by mesh structure and quality which can negatively influence the predicted structure of organized charge motions, turbulence generation and interaction between in-cylinder flows and injected sprays. This is even more relevant for modern direct injection engines where multiple injections and control of charge motions are employed in a large portion of the operating map. Currently, two different approaches for mesh generation exist: manual and automatic. The first makes generally possible to generate high-quality meshes but, at the same time, it is very time consuming and not completely free from user errors. Automatic mesh generation is very fast, but does not easily allow to align grid with flow and spray in regions of interest, for instance where fuel is delivered or where air enters the cylinder. Within this context, the authors have developed a novel approach for automatic mesh generation, where both mesh quality and flow alignment are taken into account. Such methodology has been incorporated into the Lib-ICE code, which is based on the OpenFOAM technology. On the basis of combustion chamber details and/or user specified parameters (piston bowl points, injector direction, squish height, valve lift diagram,...), body fitted, high quality grids are automatically generated to perform full-cycle or compression/combustion simulations. To assess the proposed approach, two direct-injection engines were simulated. The first is Diesel fueled and only compression and combustion phases are simulated, showing the advantages of a spray-oriented grid, compared to a conventional Cartesian one, in terms of prediction of fuel-air mixing and combustion process. The second chosen configuration is a gasoline, direct-injection engine. In this case full-cycle simulations were performed and computed flow field data were compared with optical experimental ones.
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Flow, Turbulence and Combustion, 2014
ABSTRACT Large eddy simulation is performed to investigate air entrainment and mixing in diesel s... more ABSTRACT Large eddy simulation is performed to investigate air entrainment and mixing in diesel sprays with and without combustion. The Spray A case of the Engine Combustion Network (ECN) is considered in the study, in which liquid n-Dodecane is injected at 1500 bar through a nozzle of 90 μm into a constant volume vessel with an ambient density of 22.8 kg/m3 and an ambient temperature of 900 K. Primary and secondary breakup processes of the liquid fuel are taken into account. The gas and liquid phases are modeled using Eulerian/Lagrangian coupling approach. Detailed chemical kinetics for n-Dodecane is employed to simulate the ignition process and the lifted flames. A chemistry coordinate mapping approach is used for speeding up the calculations. The effect of low temperature ignition (cool flame) on the evaporation process and on the liquid penetration length is analyzed. The effect of combustion heat release from the lifted flames on the vapor spreading in the radial direction and on the vapor transport in the streamwise direction (vapor penetration) is investigated.
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ASME 2009 Internal Combustion Engine Division Spring Technical Conference, 2009
Nowadays, Computational Fluid Dynamic (CFD) codes are widely used in different industrial fields.... more Nowadays, Computational Fluid Dynamic (CFD) codes are widely used in different industrial fields. Although hardware and numerical model improvements, the mesh generation remains one of the key points for a successful CFD simulation. Mesh quality is influenced by the adopted mesh generator tool and, after all, by the designer's experience and it becomes very important when moving meshes are required. In fact, mesh skewness, aspect ratio, and non-orthogonality have to be controlled during the deforming process since their wrong ...
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SAE Technical Paper Series, 2014
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ASME 2006 Internal Combustion Engine Division Spring Technical Conference (ICES2006), 2006
ABSTRACT This paper deals with the modelling and experimental work carried out on a BMW single cy... more ABSTRACT This paper deals with the modelling and experimental work carried out on a BMW single cylinder spark ignition hydrogen engine. The authors have enhanced a 1D thermo-fluid dynamic simulation code in order to cope with the different chemical and physical aspects due to the fuelling of a spark ignition engine with hydrogen rather than with conventional gasoline. In particular the combustion module, which is based on a quasi-dimensional approach, has been extended by introducing the possibility of predicting the burning rate of the combustion of a homogeneous mixture of hydrogen and air. A fractal approach was followed for the turbulent flame speed evaluation, while an extend database for laminar burning velocities was created applying a kinetic simulation code for one-dimensional laminar flames. The modelling of the whole intake and exhaust systems coupled to the engine has been addressed, considering port-injection fuel system, in which hydrogen has been injected at very low temperature (cryogenic conditions). The fundamental 1D fluid-dynamic equations are solved by means of second order finite difference schemes; the working fluid is considered as a mixture of ideal gases, with specific heats depending on the gas temperature and the mole fractions of species, whose correlations for each specie (including para-hydrogen) have been extended in the region of low temperature. A first validation of the enhanced model is shown in the paper, comparing the computed results with the experimental data of in-cylinder pressures, intake and exhaust instantaneous pressure histories at different locations and NO emissions discharged by the cylinder.
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SAE Technical Paper Series, 2013
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Proceedings of the Combustion Institute, 2015
ABSTRACT This paper presents an approach for modelling combustion in homogeneous charge compressi... more ABSTRACT This paper presents an approach for modelling combustion in homogeneous charge compression ignition (HCCI) conditions based on the first order conditional moment closure (CMC) method. The model is implemented into the open source C++ computational fluid dynamic (CFD) code known as OpenFOAM. Direct numerical simulations (DNSs) are used to evaluate the performance of the CFD-CMC solver. In the two-dimensional (2D) DNS cases, ignition of a lean n-heptane/air mixture with thermal inhomogeneities is simulated for nine cases, with two different mean temperatures and several different levels of thermal stratification. Results from the CFD-CMC solver are in excellent agreement with the DNS for cases which exhibit a spontaneous sequential ignition mode of combustion whereas for the cases in which a mixed mode of deflagration and spontaneous ignition exists, the CMC underpredicts the ignition delay. Further investigation using the DNS data demonstrates that this discrepancy is primarily attributed to the first order closure assumption. Conditional fluctuations are found to be more significant in the case with deflagrations. Further analysis of the DNS shows that scalar dissipation fluctuations are the cause of conditional fluctuations.
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SAE Technical Paper Series, 2005
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SAE Technical Papers, 2005
Résumé/Abstract The paper describes the development of a reduced kinetic scheme for the evaluatio... more Résumé/Abstract The paper describes the development of a reduced kinetic scheme for the evaluation of the main chemical species (particularly NO and CO) in premixed turbulent flame and its application to a quasi-dimensional combustion model for spark ignition engines. The proposed mechanism is based on the kinetic solution of three transport equations for NO, CO and H, coupled with the partial equilibrium of the so-called water-shuffle equations to derive the OH, O and H 2 concentrations. The remaining species are ...
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SAE Technical Papers, 2008
ABSTRACT This paper exploits the possibilities of achieving an efficient performance optimization... more ABSTRACT This paper exploits the possibilities of achieving an efficient performance optimization methodology to be applied to different spark ignition engine configurations. The objective of the task described here is to determine the combination of parameters which provides the highest volumetric efficiency and effective torque. The definition of general strategy requires first the identification and grouping of the geometric and operating variables to be optimized (duct diameters and lengths, valve timing, spark advance, etc…). The high number of possibilities entails critical choices to reduce, from an engineering design point of view before than from a mathematical point of view, the required computational time. Once proper thermo-fluid dynamic decisions are taken, the most efficient optimization methodology is required. The application of Design of Experiments techniques allows to screen the design space and give a first estimation of the optimal point. Then, a finer optimization strategy needs to be employed. In this paper, the Mesh-Adaptive Direct Search (MADS) method and the Genetic Algorithms are presented and applied. A critical discussion on the opportunity of employing any of those methods rather than relying only the preliminary DoE indications is proposed. Different ideal and real engine configurations are studied, from simple single cylinder to high performance complex 12-cylinder engines
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SAE Technical Papers, 2011
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SAE Technical Papers, 2012
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SAE Technical Papers, 2012
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SAE Technical Papers, 2012
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Papers by Gianluca D'Errico