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The objective of this paper is to present and to validate a numerical model of a single-cylinder pneumatic-combustion hybrid engine. The model presented in this paper contains 0-D sub-models for non-spatially distributed components: Engine cylinder, Air tank, wall heat losses. 1-D sub-models for spatially distributed components are applied on the compressive gas flows in pipes (intake, exhaust and charging). Each pipe is discretized, using the Two-Steps Lax-Wendroff scheme (LW2) including Davis T.V.D. The boundaries conditions used at pipe ends are Method Of Characteristics (MOC) based. In the specific case of a valve, an original intermediate volume MOC based boundary condition is used. The numerical results provided by the engine model are compared with the experimental data obtained from a single cylinder prototype hybrid engine on a test bench operating in 4-stroke pneumatic pump and 4 stroke pneumatic motor modes.

Model-based tuning is a way followed by car manufacturers to reduce development costs. In this context, a new methodology has been developed in order to adapt a tur-bocharged diesel engine in the case of non-standard external conditions. Indeed, variable geometry turbine and fuel injection command laws are developed for standard conditions (20°C, altitude=0m). Turbocharger and fuel injection actuators pre-positioning maps should be adjusted regarding the inducted air mass density (influenced by the external temperature and pressure), in order to meet thermal, mechanical and pollutant emissions constraints. In order to reduce the use of climatic tests bench and extreme conditions tests in foreign countries, a model of a turbocharged diesel engine coupled to an optimization loop has been used to take into account the effect of non-standard external conditions on pre-positioning maps.

In the last decade, the drastic strengthening of engine emission regulations has conducted the automotive industry towards more and more sophisticated engine control strategies requiring more and more sensor inputs and actuator outputs. The testing and setting up of the ECUs implementing such strategies becomes more and more difficult, requiring numerous engine tests on test benches. ECUTEST is a hardware and software package from KADRA CONSULTANTS that offers the following features: Simulation of sensors including variable reluctance sensor, lambda sensor, knock sensor… Measurement of output signals (injection, ignition, EGR…) timing and amplitude. A predefined test pattern can be replayed on the ECU to perform end of line testing. A real-time model can be used for testing and setting up embedded closed loop strategies. The present paper will cover the implementation of a real-time SI engine model on ECUTEST.

Torque based engine control seems to be the trend for the future for powertrain management (automatic gearbox, hybrid vehicles). Today, torque estimation is best achieved using cylinder pressure transducers. This paper proposes a method to achieve a good accuracy of the torque using Bézier curves to reconstruct the cylinder pressure peak from the low frequency embedded pressure measurements. As is, IMEP cannot be used on a cycle to cycle basis for engine torque control, due to the very high cycle to cycle variability of SI engines. To improve the quality of the IMEP feedback data, this paper proposes a moving horizon filtering method.

To meet future pollutant emissions standards, it is crucial to be able to estimate the cycle by cycle composition of the combustion chamber charge. This charge consists of fresh air, fuel and residual gas from the previous cycle. Unfortunately, the residual gas fraction cannot be directly measured. Therefore, a model of residual gas fraction as a function of engine parameters and operating parameters has been developed. The model has been calibrated with exhaust pipe hydrocarbon measurements using a successive dilution method.

Internal combustion engines development with increased complexity due to CO2 reduction and emissions regulation, while reducing costs and duration of development projects, makes numerical simulation essential. 1D engine simulation software response for the gas exchange process is sufficiently accurate and quick. However, combustion simulation by Wiebe function is poorly predictive. The objective of this paper is to compare different approaches for 0D Spark Ignition (SI) modeling. Versions of Eddy Burn Up, Fractal and Flame Surface Density (FSD) models have been coded into GT-POWER platform, which connects thermodynamics, gas exchange and combustion sub-models. An initial flame kernel is imposed and then, the flame front propagates spherically in the combustion chamber. Flame surface is tabulated as a function of piston position and flame radius. The modeling of key features of SI combustion such as laminar flame speed and thickness and turbulence was common.

This paper describes mid-load experimental tests combining massive EGR rates and multiple injection strategies. Influence of very high EGR rates on combustion has been reviewed, and a response-surface-modeling tool has been used to present main results. Outputs from this empirical model did highlight a dramatic soot increase when oxygen concentration is reduced. The empirical model based on experimental results model was also used to define more precisely the EGR rate needed to reach US 2010 NOx target. This EGR rate being defined, some investigation has been made on dual-injection strategies combining a main injection with an early pilot injection. Both quantity and timing of pilot injection were varied, and experimental results showed large benefits of this strategy to reduce soot emissions without significant increase of NOx emissions or fuel consumption. Better results were also experienced with the addition of a close post-injection.

One way of improving electronic engine control is to get an insight into the combustion process, using a direct measurement method: this means the sensor must be put straight into the combustion chamber. The reference for analyzing combustion development is the cylinder pressure sensor. Due to the price of this sensor and the added complexity for cylinder head design and manufacturing, cylinder pressure sensors are not conceivable today for mass production. An alternative to the cylinder pressure sensor is the ionization sensor. It seems to be very promising for electronic engine control. Several publications have already demonstrated the benefits of ionization currents sensing for misfire detection, knock detection, closed loop ignition control, air-fuel ratio estimation. On the contrary, other publications have shown severe limitations of the ionization sensor. For example, fuel composition or additives can influence the ionization current.