Search Results

This paper presents a new 0D phenomenological approach to predict the combustion process in diesel engines operated under various running conditions. The aim of this work is to develop a physical approach in order to improve the prediction of in-cylinder pressure and heat release. The main contribution of this study is the modeling of the premixed part of the diesel combustion with a further extension of the model for multi-injection strategies. In phenomenological diesel combustion models, the premixed combustion phase is usually modeled by the propagation of a turbulent flame front. However, experimental studies have shown that this phase of diesel combustion is actually a rapid combustion of part of the fuel injected and mixed with the surrounding gas. This mixture burns quasi instantaneously when favorable thermodynamic conditions are locally reached. A chemical process then controls this combustion.

Porous honeycombs filters have been widely used for diesel particulates filtration in passenger cars applications. In all current DPF applications, filter lifetime and design are dictated by the need to store non combustible ash generated at the exhaust. Therefore, improving the ash storage capacity of a filter appears as a major step towards the development of maintenance free DPF systems. This paper describes a new filter design that was developed to optimize ash storage volume. Numerical simulations and roller bench tests have been performed in order to compare the performances of this new filter to commercial honeycomb filters.

Recrystallized Silicon carbide (R-SiC) honeycombs have been widely used over the last couple of years as filtration media for diesel particulates filtration in passenger cars applications. Although such filters are very reliable thanks to SiC good properties and smart designs, existing devices can still be improved. This paper describes several new features developed for R-SiC honeycomb filters in order to increase their durability and reduce their cost. Durability improvements can be obtained through the optimization of different filter properties such as thermo-mechanical resistance and thermal diffusivity. Specific tests have been performed in order to optimize new R-SiC filters.

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.

This paper presents energy management strategies for a new hybrid pneumatic engine concept, which is specific by its configuration: It is not a vehicle but only an engine itself which is hybridized. This arrangement could provide as much as 30% of fuel saving depending on the driving cycle. Therefore different energy management strategies are proposed and compared in this paper. The first of them is called Causal Strategy and implements a rule-based control technique. A second strategy called Constant Penalty Coefficient is based on minimization of equivalent consumption, where the use of each energy source is formulated in a comparative unit. The balance between consumption of different energy source (chemical or pneumatic) is reached by introduction of an equivalence factor. The third strategy is called Variable Penalty Coefficient, where the equivalence factor is consider as variable within the amount of pneumatic energy stored in the air-tank.

This paper describes an innovative method to estimate the wall losses during the compression and combustion strokes of a gasoline engine using the cylinder pressure measurement. The estimation during the compression and combustion strokes allows to better represent the system during the combustion. A sliding mode observer is derived from a validated 0-D physical engine model and its convergence and stability are proved. The observer is validated using two different engine models: a one zone engine model and a two zones engine model with flame wall interaction. A good agreement between the estimation results and the model reference is observed, showing the interest of using closed loop strategies to estimate the wall losses in a SI engine.

The development of the Diesel Particulate Filter (DPF) cell geometry and DPF size for new applications requires specific tools to predict the pressure drop as a function of filter characteristics, mass flow and filter loading. A 1-D permeability model is most useful for this type of work. This paper presents the development of a 1-D physical model of DPF permeability. This model includes the symmetric and asymmetric channel shape and is able to simulate various functional phases of the DPF through its lifetime: with or without soot and with or without ash. This kind of model needs several physical coefficients, in order to describe the flow behavior. This work explains the determination of the physical coefficients of the 1-D model. The large disparity of the literature is shown. Therefore, it is necessary to carefully determine these coefficients.

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.

The amount of fresh air induced into the cylinder is the main parameter to be taken into account when developing the engine control laws. However, the instantaneous amount of induced air cannot be directly measured. Additionally, as the engine air ducting becomes more and more complex (high and low pressure exhaust gas recirculation, variable valve timing, pneumatic hybridization…), models used to develop engine control laws must be as predictive as possible. It has therefore been decided to use 1d aerodynamics simulation to provide accuracy to the control laws development and validation process. Commercial engine codes have been tested but did not give satisfactory results in terms of calculation time and flexibility. Additionally, in the case where no experimental data are available to determine valve discharge coefficient, simulation results were in total disagreement with the engine bench measurements.

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.