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Combustion in SI engines strongly depends on in-cylinder turbulence characteristics. Turbulence by definition presents three-dimensional (3D) features; accordingly, 3D approaches are mainly used to investigate the in-cylinder flow and assist the engine design. However, SI engine architectures are becoming more and more complex and the generalization of technologies such as Variable Valve Timing (VVT) and Direct Injection (DI) considerably increases the number of degrees of freedom to deal with. In this context, the computing resources demanded by 3D CFD codes hugely increase and car manufacturers privilege system simulation approaches in the first phases of the design process. Accordingly, it is essential that the employed 0D/1D models well capture the main physics of the system and reproduce the impact that engine control parameters have on it.

In the present study, experiments were carried out in a single-cylinder downsized SI engine with different rates of oxygen (15% to 27% by volume in the total mixture of intake gases except fuel) and equivalence ratios (from 0.45 to 1). Therefore, the oxygen volume fraction is due to oxygen enrichment or nitrogen dilution. The study of the impact of controlling oxygen concentration on the combustion characteristics and emissions was performed at 1400 rpm, at several loads (Indicated Mean Effective Pressure (IMEP) from 400 to 1000 kPa). For each operation point, the spark advance and the intake pressure were adjusted simultaneously in order to maintain the load and obtain a minimum value of indicated Specific Fuel Consumption (SFC). The effect of oxygen concentration on the engine combustion characteristics was simulated by using the commercial software AMESim, with the combustion model developed by IFP-EN, and an adapted algorithm was used to avoid residual gas calibration.

The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap. This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR.

In spark-ignition engines, Cycle-to-Cycle Variations (CCV) limit the optimization of engine operation since they induce torque variations and the occurrence of misfire and/or knock. A mean for limiting the related negative impact of CCV on fuel consumption and emissions would be control strategies able to address them. At present, engine simulation codes used for control purposes can only describe CCV linked to variations of gas exchanges in the air loop. CCV of the in-cylinder flow motion cannot be naturally captured by classical quasi-dimensional combustion chamber models. A convenient way to mimic CCV is to impose stochastic distributions of the combustion model parameters. Nevertheless, it is not always clear if these perturbations have physical bases as well as realistic ranges of variation.

Increasingly restrictive emission standards and CO2 targets drive the need for innovative engine architectures that satisfy the design constraints in terms of performance, emissions and drivability. Downsizing is one major trend for Spark-Ignition (SI) engines. For downsized SI engines, the increased boost levels and compression ratios may lead to a higher propensity of abnormal combustions. Thus increased levels of Exhaust Gas Recirculation (EGR) are used in order to limit the appearance of knock and super-knock. The drawback of high EGR rates is the increased tendency for Cycle-to-Cycle Variations (CCV) it engenders. A possible way to reduce CCV could be the generation of an increased in-cylinder turbulence to accelerate the combustion process. To manage all these aspects, 1D simulators are increasingly used. Accordingly, adapted modeling approaches must be developed to deal with all the relevant physics impacting combustion and pollutant emissions formation.

Due to increasingly stringent regulations, reduction of pollutant emissions and consumption are currently two major goals of the car industry. One way to reach these objectives is to enhance the management of the engine in order to optimize the whole combustion process. This requires the development of complex control strategies for the air and the fuel paths, and for the combustion process. In this context, engine 0D modelling emerges as a pertinent tool for investigating and validating such strategies. Indeed, it represents a useful complement to test bench campaigns, on the condition that these 0D models are accurate enough and manage to run quite fast, eventually in real time. This paper presents the different steps of the design of a high frequency 0D simulator of a downsized turbocharged Port Fuel Injector (PFI) engine, compatible with real time constraints.

Motor fuels are today increasingly blended with oxygenate components to reduce global CO2 emissions. Among these components, biomass-derived ethanol is very popular for spark ignition engine operation as it is not only a renewable source of energy, but it also allows to increase the engine power and thermal efficiency. Indeed, ethanol has the advantage of a high latent heat of vaporization leading to the so-called “cooling effect” which allows to increase the air-mass flow rate in the engine while reducing the charge temperature. This last property of ethanol combined with its high octane index make the engine less sensitive to knock. Then, although ethanol is characterised by high combustion speeds, optimal values of spark advance can be maintained on a larger range of engine operating conditions and high compression ratios as well as increased levels of downsizing can be used, all these aspects contributing to improve fuel consumptions.

The LES technique has been applied to the simulation of 9 consecutive complete engine cycles of a single cylinder, spark-ignited 4valve engine. The simulations have been realized with the AVBP code, jointly developed by IFP and CERFACS. An extended coherent flame model approach (ECFM-LES) has been used to model spark ignition and turbulent combustion, and is shortly presented, along with the used turbulence models. The engine was fuelled with gaseous propane injected far upstream from the intake, so that fuel injection was not simulated, the fresh charge being assumed to be homogeneous. After a description of the numerical set-up, results obtained with LES are compared with experimental findings on cycle to cycle cylinder pressure evolutions. It is shown that LES indeed captures qualitatively the observed cyclic variability of the engine, even with only 9 cycles simulated.

In order to meet the CO₂ challenge, today a wide variety of solutions are developed in the automotive industry such as advanced technologies (downsizing, VVA, VCR), new combustion modes (HCCI, stratified and lean combustion), hybridization, electrification or alternative fuels. Furthermore, couplings between these solutions can be envisaged, increasing considerably the number of degrees of freedom which have to be accounted for in the development of future powertrains. Consequently, for time and cost reasons, it is not obvious to evaluate and optimize the full potential of new concepts only by the mean of experimental investigation. In this context, system simulation appears as a powerful and relevant complement to engine tests for its flexibility and its high CPU efficiency. This paper focuses on the development of a methodology combining both simulation and experimental tools to quantify the interest of innovative solutions in the very first steps of their development.

Reducing greenhouse gas emissions to limit global warming is becoming one of the key issues of the 21st century. As a growing contributor to this phenomenon, the aeronautic transport sector has recently taken drastic measures to limit its impact on CO2 and pollutants, like the aviation industry entry in the European carbon market or the ACARE objectives. However the defined targets require major improvements in existing propulsion systems, especially on the gas generator itself. Regarding small power engines for business aviation, rotorcrafts or APU, the turboshaft is today a dominant technology, despite quite high specific fuel consumption. In this context, solutions based on Diesel Internal Combustion Engines (ICE), well known for their low specific fuel consumption, could be a relevant alternative way to meet the requirements of future legislations for low and medium power applications (under 1000kW).

The powertrain simulation tools are nowadays an efficient support to optimize cost and duration of the whole engine technological developments. They can deliver optimized simulator versions for various targets such as system understanding, design investigation, non-measurable value access or virtual bench use for control and calibration. Under the condition of an accurate modelling and simulation know-how to take into account the simulator using constraints, the simulation can become an undisputable support for powertrain design as the test bed already is. The goal of this paper is to present the large range of the powertrain simulation capabilities for the specific application of a downsized turbocharged GDI engine with twin VVT embedded in a concept car. The modelling framework is first presented and different items are laid-out. A first part is dedicated to the engine air path and in particular to the modelling of gas exchange phenomena such as back-flow.