Electrification of vehicles and improved efficiency of internal combustion engines (ICE) are the main levers to reduce greenhouse gas emissions. Recent studies indicate that in 2040 thermal cars sales will still remain an important part of the market and the spark-ignition engine (SIE) is seen as the most interesting ICE technology. However, technological challenges must be tackled before meeting real driving emissions expectation due to the diversification and complexity of hybrid applications. For flow aerodynamics, mixing and combustion down to the individual engine cycle, challenges are for example associated to robustness of concepts on a cycle basis, rapid variations of engine loads observed in hybrid technologies during transients, the occurrence of extreme cycles for a wider range of operating conditions. Numerical, experimental and analyzing tools have made significant progress in recent years for the analysis of spatial and temporal scales of the unsteady in-cylinder flows. Large-Eddy Simulation (LES) is an essential tool for the design of robust concepts. While LES has been validated against well-defined experiments, the prediction of internal turbulent dynamics and combustion during a cycle is affected by epistemic uncertainties. Therefore, progress is still needed to obtain optimal and robust design. The main objective of ALEKCIA is to develop game-changing tools for augmented prediction and analysis of turbulent reactive flows with a focus on real SIE operations to better capture time-resolved events and increase understanding and control of the origins of undesired behaviors. The key hypothesis is that future progress and success is tied to the synergistic, strong combination of experimental and numerical tools at every stage of the project, which will provide advancement in the analysis of physical scales and boundary conditions (BCs). The major scientific challenges addressed by ALEKCIA are to 1/ quantify and reduce uncertainties (UQ) due to model parameters and BCs, 2/ develop new Data Assimilation (DA) approaches for coupling LES with experimental measurements, 3/ develop new decomposition methods to analyse big data generated by LES and high-speed PIV, 4/ combine them with UQ and DA methods for detailed analysis of individual SIE cycles during steady operations and fast transients. We stress that this methodology could also be used more widely for industry and energy applications. To achieve its ambitious objectives, work in ALEKCIA is structured into one management task (T0) and three technical tasks (T1 to T3). We will address non-cyclic phenomena under transient and fired operations and develop novel analysis from the acquired experimental and LES databases of a SIE performed respectively at PRISME (T1) and IFPEN (T3) laboratories. The partners of the project will also collaborate on the development of crank-angle resolved spatio-temporal EMD decomposition (T1 and T3) for engine flows to obtain an unprecedented detailed understanding of the mechanisms involved in the generation of in-cylinder flow, turbulent dynamics and their impact on combustion. The development of UQ tools to quantify and reduce uncertainties in complex LES of SIE flows is also targeted (T3). Finally, the capabilities of DA methods to calibrate realistic BCs on-the-fly is investigated by PPRIME (T2 and T3). This task is particularly relevant when assimilating experimental data (in the form of BC and in-cylinder large-scale flow patterns from EMD) obtained in extreme cycles. EMD obtained from a selected number of measured cycles presenting very slow or fast combustion rates will be coupled with UQ and DA tools for their inclusion in LES (T3). In this scenario, LES will be able to properly follow the assimilated aerodynamic behaviour of these cycles while turbulent dynamic will be modelled. Finally, the application of the developed tools will allow to identify the main key parameters controlling internal aerodynamics.

The REFINE project focuses on the experimental investigation and numerical simulation of real-fluid injection and mixing processes under sub-, trans- and super-critical conditions. The domain of interest of the present proposal concerns the propulsion with application to the automotive and aerospace science and technology where supercritical fluids may be considered as propellants. Indeed, the need for higher efficiency and lower emission levels leads to increase pressure and temperature levels, i.e. to reach supercritical properties of fluids. The objective of REFINE is to build a simple well-controlled test-bench able to study a fluid injection under sub-, trans- and super-critical conditions and to associate experimental and numerical diagnostics to deliver the finest information. An ethane injection occurs in a 5-liter high-pressure experimental test-bench. The X-ray diagnostics setting-up will be the project keystone, as it allows for delivering a non-polluted density measurement. Indeed, such diagnostics are not disrupted by the index gradient observed in corrugated flows, contrary to laser techniques. Colored background oriented Schlieren visualization is used for backup as well as a more classical shadowgraphy technique. Numerical simulations will be realized in parallel to consolidate physics understanding and for model validation.

In the context of reducing pollutant emissions and diversify fuel sources, the CICCO project (Compression Ignition Combustion Controlled by Ozone) aims at studying the potential of modifying air oxidizing properties by ozone addition in compression ignition engine. Indeed thanks to its oxidizing properties, ozone significantly lowers the auto-ignition temperature of fuels, including those with low Cetane number. Thus, in the case of direct injection engines (diesel engine), ozone injection at the intake would improve the critical phases of start or restart. It would also allow to adapt the fuel to the compression ratio, or to reduce the compression ratio to lower pollutant emissions directly at the source. In the case of HCCI or LTC combustion, ozone injection would enable to control cycle to cycle the ignition temperature of the fuel-air mixture and therefore enhance the ability to control engine combustion. An actuator prototype will be realized and used from the beginning of the program to demonstrate the concept of combustion controlled by ozone. This prototype will meet the criteria of energy cost and controllability. The characterization of chemical species formed during discharge (O3, O, OH, NO ...) and can occur during fuel oxidation will be studied. The effect of ozone will be analyzed on two single cylinder engines without optical or with optical access for measuring chemiluminescence and fluorescence (LIF) of the OH * radical, OH and formaldehyde. Its impact on advanced combustion modes like HCCI type will be well characterized in a first indirect injection engine. The potential of ozone addition in a standard late injection diesel engines will also be studied on a diesel optical engine. To address fuel diversification, the influence of ozone on different fuels with low Cetane value (fuel such as petrol, bio-fuel, gas, refinery intermediates between gasoline and Diesel ...) will also be studied. In parallel, the existing EADF model for 3D simulation of diesel combustion will be extended to take into account the presence of ozone in fresh gas, and will be used to carry out RANS simulations of the different engines used for experimental studies. These simulations will improve the understanding of fuel oxidation by ozone, capitalize the experimental results and identify new injection strategies, dilution and use of fuels. Finally, from the experimental and numerical results, the most promising engine adjustments will be made on a single cylinder research engine running on stabilized and transient operating points. An optimized ozonizer prototype will be used to demonstrate the feasibility to control the cycle to cycle combustion a compression ignition engine with a factory-made device.

Three-dimensional bluff-body wakes are of key importance due to their relevance to the automotive industry. Such wakes contribute to consumption and greenhouse gas emissions. Drastic European Union limitations concerning these two mechanisms conduct the car industry to think about efficient vehicles. In this project, we propose robust drag and fuel reduction solutions for road-vehicles by closed-loop control of turbulent flows working efficiently for a range of operating conditions including changing oncoming velocity and transient side winds. To achieve this goal, we combine passive, active control and closed-loop strategies by using compliant deflectors, unsteady micro-jets and Machine Learning techniques. This project aims to prove a feasibility of the control from laboratory scale up to a full-scale industrial demonstrator. The main repercussions of the project will be on the reduction of the environmental impacts of transport industry and the gain of competitiveness and employment. This project consists on experiments in wind and water tunnels, numerical simulations and control strategies. Two models will be used, the square back bluff body and a reduced scale car model. The latter is representative of SUV and is inspired from the model used in collaborative work between POAES and PRISME. Control strategies will be tested in both configurations by combining passive and active actuation i.e. fixed or moving flaps and micro jet actuators. Closed-loop control will also be developed in these situations. Control strategies will be mainly developed by PPRIME. Experiments will be done in PRISME and PPRIME. LHEEA will take in charge numerical simulations and optimization. Finally, PSA will provide the vision of an automobile manufacturer on the industrial feasibility of the developed control strategies.

The principal aims of the "Plasma ReMoVal" project are the development and the experimental validation of a 3Dxyz software dealing with the simulation of non-equilibrium non-thermal corona plasma reactors operating at atmospheric pressure (PA). Such reactors can be used for the treatment of flue gases. The software will facilitate the design of corona reactors in view of the enhancement of their efficiency at a better cost and will provide essential information for the plasma/catalyses coupling insofar as the gas mixture in contact with the catalytic sites can be identified and where the production of adapted species for the heterogeneous reactions could be maximized. The discharge phase including branching phenomena will be modelized in 3Dxyz geometry for a time duration of about a hundred of nanoseconds thanks to the use of massive parallel computation. The discharge phase simulation involves the electro-hydrodynamic model coupled to chemical and gas dynamics ones. The influence of the transfer of the momentum quantities of charged-neutral species as well as the relaxation of vibrational states into thermal energy is taken into account. The cartography of source terms of both density of radicals and gas temperature, issuing from discharge-phase models is used as the input local data of commercial software (FLUENT) dealing with reactive gas flow stressed by corona discharges. The elaboration and the validation of the software will be performed with test-reactors (point to plane and multi points to plane) filled with humid synthetic ambient air (N2, O2, H2O) operating at saturated vapor pressure. These test-reactors will be electrically supplied by a pulsed voltage in order to facilitate triggering of the fast electronic devices, themselves driving the optical diagnostic apparatus, with the "onset" of the corona microdischarges. The predicative potentiality of the software is studied with new specific reactors specially developed for this project. These reactors operate at very close conditions usually encountered in industrial applications. The gas composition and temperature, the corona reactor geometry (point to plane and wire-cylinder), the choice of the pollutant (C3H6 with or without NO), the gas flow rate and the pulse voltage frequency are some of parameters that will be studied. A particular attention will be paid to the implementation and the use of a diagnostic tool, namely the absorption of wide band radiation issuing from a Z-pinch, which allows absolute measurement of reactive species in both the discharge and the post-discharge phases. Finally, "calculation" and experimental means are developed in order to determine the lack of "basic data" needed for modeling. These data mainly concern the transport coefficient and reaction rate constants of electrons and polyatomic ions (Cluster) in humid mixtures as well as the kinetic scheme of majority molecules, such as N2 (for example) in their vibrational or metastable exitation states.