Stephane Jay

• PhD
• Project Manager at IFP Energies nouvelles

In this study, we focus on the collision rate and contact time of finite-sized droplets in homogeneous , isotropic turbulence. Additionally, we concentrate on sub-Hinze-Kolmogorov droplet sizes to prevent fragmentation events. After reviewing previous studies, we theoretically establish the equivalence of spherical and cylindrical formulations of t...

This paper presents a comprehensive framework for addressing the challenges associated with turbulence linear forcing in incompressible two-phase flows. By examining existing literature on linear forcing techniques for single-phase flows, which typically yield constant turbulent production, kinetic energy, or dissipation rates, we derive a general...

Understanding, modeling, and reducing the cycle-to-cycle variability (CCV) of combustion in internal combustion engines (ICE) is a critical challenge to design engines of high efficiency and low emissions. A high level of CCV may contribute to partial burn, misfire, and knock in extreme engine cycles, which affects engine performance and eventually...

In this work, the phenomenon of cycle-to-cycle variability (CCV) of combustion in a spark ignition engine is investigated to give a deeper understanding of CCV generation. The main objective is to localize within the cylinder and all along the engine cycle the flow variabilites and identify some driving mechanisms originating in the flow structures...

Multi-cycle large-eddy simulation (LES) is performed to investigate cycle-to-cycle variations (CCV) of in-cylinder flow in a single-cylinder spark ignition optically-accessible research engine under motored conditions. The bivariate 2D empirical mode decomposition (EMD) is improved regarding the mode combination and computational efficiency of hand...

A Large-Eddy Simulation (LES) modeling framework, dedicated to ultra-lean spark-ignition engines, is proposed and validated in the present work. A direct injection research engine is retained as benchmark configuration. The LES model is initially validated using the cold gas-exchange conditions by comparing numerical results with PIV (Particle Imag...

Ultra-lean burn conditions (λ > 1.8) is seen as a way for improving efficiency and reducing emissions of spark-ignition engines. It raises fundamental issues in terms of combustion physics and its modeling, among which the significant reduction of the laminar flame speeds and increase of the laminar flame thickness, as well as an increased sensitiv...

The bivariate two dimensional empirical mode decomposition (Bivariate 2D-EMD) is extended to estimate the turbulent fluctuations and to identify cycle-to-cycle variations (CCV) of in-cylinder flow. The Bivariate 2D-EMD is an adaptive approach that is not restricted by statistical convergence criterion, hence it can be used for analyzing the nonline...

Downsized spark ignition engines running under high loads have become more and more attractive for car manufacturers because of their increased thermal efficiency and lower CO2 emissions. However, the occurrence of abnormal combustions promoted by the thermodynamic conditions encountered in such engines limits their practical operating range, espec...

In this work, both experimental and numerical investigations have been carried out in order to improve the modelling of the vaporization of wall liquid-deposits in internal combustion engines. A comprehensive model is suggested for the vaporization of liquid films in the different boiling regimes, including nucleate boiling regime, the Leidenfrost...

Downsized spark ignition (SI) engines running under high loads have become more and more attractive for car manufacturers because of their increased thermal efficiency and lower CO2 emissions. However, the occurrence of abnormal combustions promoted by the thermodynamic conditions encountered in such engines limits their practical operating range,...

The automotive industries have been concerned by the efficiency of combustiion devices and the reduction of pollutant emissions. To get accurate measurements inside an engine numerical simulation is considered as a good alternative to understand two-phase flows and two-phase combustion and to design new combustion chambers. A novel Eulerian moment...

To assist industrial engine design, 3D simulations are increasingly used as they allow evaluation of a wide range of engine configurations and operating conditions and bring a comprehension of the underlying physics comple-mentary to experiments. While the gaseous flow description has reached a certain level of maturity, the multiphase flow descrip...

Relying on two recent contributions by Massot et al. [SIAM J. Appl. Math. 70 (2010), 3203--3234] and Kah et al. [J. Comput. Phys. 231 (2012), 394--422], where a Eulerian Multi-Size Moment (EMSM) model for the simulation of polydisperse evaporating sprays has been introduced, we investigate the potential of such an approach for the robust and accura...

To assist the industrial engine design process, 3-D computational fluid dynamics simulations are widely used, bringing a comprehension of the underlying physics unattainable from experiments. However, the multiphase flow description involving a liquid fuel jet injected into the chamber is still in its early stages of development. There is a pressin...

Among the new combustion concepts envisaged to meet future regulations, the Dual Fuel (DF) concept is considered to be an attractive strategy due to its potential to reduce CO2 emissions and engine-out pollutant emissions levels. A small quantity of high-cetane fuel (Diesel) is injected in the combustion chamber in order to ignite a homogeneous mix...

In this paper three turbulent combustion models with different underlying hypothesis are compared with measurements from an extensive experimental database. The reference model is ECFM3Z, with the Tabulated Kinetics of Ignition (TKI) model for auto-ignition modeling, together with the CO reduced kinetics (CORK) model and the extended Zeldovich mode...

A major issue for the simulation of two-phase flows in engines concerns the modeling of the liquid disperse phase, either in the Lagrangian or the Eulerian approach. In the perspective of massively parallel computing, the Eulerian approach seems to be more suitable, as it uses the same algorithms as the gaseous phase solver. However taking into acc...

In this paper, we tackle the modeling and numerical simulation of dilute gas-droplet and gas-particle flows for which polydispersity description is of paramount importance. Starting from a kinetic description for point particle experiencing transport either at the carrier phase velocity for aerosols or at their own velocity for more inertial partic...

The ability to simulate multi-phase flows is of crucial importance for the prediction of engine performance and pollutant emissions. The flow generated by the injection of a liquid inside a combustion chamber being generally very complex, we only focus on Eulerian description of the dispersed phase in the present work. One of the main difficulties...

In the context of engine development for low fuel consumption and low emissions, combustion modeling is a challenging subject as the requirements for lower pollutant emissions mean that accurate temporal and spatial predictions of the heat release and species concentrations are needed. Among the various approaches developed recently to account for...

This work investigates the issue of describing polydispersivity in an Eulerian framework of a disperse spray with potentially mesh movement. In this perspective, the multi-fluid model and and associated numerical schemes provide robust tools (de Chaisemartin (2009)). However, there is a substantial interest for the development of a method able to a...

In the context of low consumption and low emissions engines development, combustion processes modeling is a challenging subject as the requirements for accurately controlled pollutant emissions are becoming more stringent. From a scientific point of view, it is a major source of in depth investigations as the chemical processes involved are strongl...

Development of a FPI Detailed Chemistry Tabulation Methodology for Internal Combustion Engines - In this paper the FPI (Flame Prolongation of ILDM) approach for chemistry tabulation is applied to 3D internal combustion engine simulations. The first issue is to adapt the method to a fully compressible solver with a limited database size. Tabulation...

The concerns about global warming and long-term lack of fossil fuels are strong incentives for alternative fuel research and adaptation of the internal combustion engines (ICE) to these fuels. Because it is free of any carbon compounds and can be produced from alternative sources, hydrogen is an interesting candidate for future ICE-based powertrain...

To face the demand for efficient and environmentally-friendly engines, the Diesel HCCI (Homogeneous Charge Compression Ignition) and LTC (Low Temperature Combustion) concepts have been developed in order to drastically reduce the pollutant emissions of present Diesel engines at part load while maintaining their fuel consumption attractive. To be us...

The prediction of auto-ignition delay times in HCCI engines has risen interest on detailed chemical models. This paper described a validated kinetic mechanism for the oxidation of a model Diesel fuel (n-decane and α-methylnaphthalene). The 3D model for the description of low and high temperature auto-ignition in engines is presented. The behavior o...

Among the existing concepts to help improve the efficiency of spark ignition engines on low load operating points, Controlled Auto-Ignition™ (CAI™) is an efficient way to lower both fuel consumption and pollutant emissions at part load without major modifications of the engine design. The CAI™ concept is founded on the auto-ignition of a highly dil...

The study of soot oxidation and CO formation in internal combustion engine applications is the subject of numerous recent investigations. Their modeling is particularly important for Diesel operating conditions. Models have been developed recently at IFP to account for the complicated kinetic processes involved in CO / soot production and oxidation...

Concepts of surface density are exploited to model the coupled processes of atomization, vaporization, and combustion in turbulent jet flames formed by cryogenic propellants. An Eulerian framework is used to describe the two-phase flow formed by a coaxial injector fed by liquid oxygen and gaseous hydrogen. A transport equation for the density of th...

The accuracy of predictive engine modelling for Compression Ignition (CI) combustion modes is heavily depending on the quality of the description of the auto-ignition process. The Controlled Auto-Ignition (CAI™) combustion process is a CI combustion mode using gasoline as fuel. Its modelling requires to account for the chemical characteristics of t...

Towards even cleaner Diesel engines: Contribution of 3D CFD tools - Three-dimensional Computational Fluid Dynamics (CFD) tools have become essential for research on Diesel engines. Indeed they hell) grasp the basic phenomena at stake, as combustion processes get more and more complex in order to comply with conflicting demands: more stringent emiss...

The drive for substantial CO2 reductions in gasoline engines in the light of the Kyoto Protocol and higher fuel efficiencies has increased research on downsized, turbocharged engines. Via a higher intake air pressure, an increase in specific power output can be reached on a comparatively smaller sized engine, in order to ensure high torque capabili...

A model for the auto-ignition of hydrocarbons applicable to 3D internal combustion engine calculations is proposed in this paper. The limits of classical methods using an auto-ignition delay are investigated when cool flame phenomena are present. A method based on tabulated reaction rates is presented to capture the early heat release induced by lo...

The spray formed by a coaxial injector fed with water and air is modeled and simulated in this paper. The purpose is to perform global validations of the flow structure using an interfacial surface density balance equation. The field equations are described in the context of an homogeneous flow code and special attention is paid to the modeling of...

Three-dimensional Computational Fluid Dynamics (CFD) tools have become essential for research on Diesel engines. Indeed they help grasp the basic phenomena at stake, as combustion processes get more and more complex in order to comply with conflicting demands: more stringent emission standards and customer desire for research on Diesel engines. Ind...

The accuracy of predictive engine modelling for Compression Ignition (CI) combustion modes is heavily depending on the quality of the description of the auto-ignition process. The Controlled Auto- Ignition (CAITM) combustion process is a CI combustion mode using gasoline as fuel. Its modelling requires to account for the chemical characteristics of...

To face the demand for efficient and environmentally-friendly engines, the Diesel HCCI (Homogeneous Charge Compression Ignition) and LTC (Low Temperature Combustion) concepts have been developed in order to drastically reduce the pollutant emissions of present Diesel engines at part load while maintaining their fuel consumption attractive. To be us...