Jean-François Hetet

Electric vehicle platform for drivability analysis

In order to lead properly an electric vehicle project, it is very important to assess and optimize the driver perception during manoeuvres such as tip-in and tip-out. This aspect of vehicle customer perception is called “drivability”. To meet these objectives, a co-simulation platform has been developed between models under LMS-AMESim® and Matlab/Simulink®. The first model represents the physical characteristics of the vehicle with LMS-AMESim® and takes into account stiffness of the driveline, motor block behaviour onto its mounting blocks, suspensions, tires and vehicle dynamics. The second model computes the torque command of the electric motor for drivability manoeuvres as well as for driving cycles with Matlab/Simulink®. This paper shows how this platform can help integration teams to tune software and hardware parameters from the early steps of the projects design. Concerning the software, any torque setpoint strategy can be integrated in order to filter the shocks amplitude during tip-in. The impact of an RST filter on the vehicle response is studied; moreover, this study shows that the vehicle range can be added to classical optimization criteria such as time response and overshoot. For the hardware side of this platform, the very good correlation of the models acceleration with track tests gives a high level of trust in the sensitivity study of most influents parameters on the drivability rating, which is assessed by some objectives criteria on vehicle acceleration.

Exergy Analysis of Complex Ship Energy Systems

With multiple primary and secondary energy converters (diesel engines, steam turbines, waste heat recovery (WHR) and oil-fired boilers, etc.) and extensive energy networks (steam, cooling water, exhaust gases, etc.), ships may be considered as complex energy systems. Understanding and optimizing such systems requires advanced holistic energy modeling. This modeling can be done in two ways: The simpler approach focuses on energy flows, and has already been tested, approved and presented; a new, more complicated approach, focusing on energy quality, i.e., exergy, is presented in this paper. Exergy analysis has rarely been applied to ships, and, as a general rule, the shipping industry is not familiar with this tool. This paper tries to fill this gap. We start by giving a short reminder of what exergy is and describe the principles of exergy modeling to explain what kind of results should be expected from such an analysis. We then apply these principles to the analysis of a large two-stroke diesel engine with its cooling and exhaust systems. Simulation results are then presented along with the exergy analysis. Finally, we propose solutions for energy and exergy saving which could be applied to marine engines and ships in general.

Influence des circuits de liaison moteur/compresseur sur le fonctionnement des moteurs Diesel à suralimentation bi-étagée

In pulsed flow, the surge line of a centrifugal compressor is highly dependent on the upstream and downstream piping systems. In this study, the shift of this surge line in the case of two two-stage turbocharged marine Diesel engines is calculated using a numerical simulation of the compressor/pipe work assembly for each engine. The linkage of two programs using the ACSL language (in a global solution procedure) allows the understanding and quantification of the connection circuits influence on the operating limits. The tendencies observed on the test bed are reproduced by the simulation, confirming the chosen methodology. This procedure also permits an analysis and understanding of the observed phenomena, especially the identification of the compressor which initiated the surge effects and the explanation of irregularities in the operating limit.

Evaluation of hot water storage strategy in internal combustion engine on different driving cycles using numerical simulations

Since the main interest worldwide of green environment companies is to reduce pollutant emissions, the automotive industry is aiming to improve engine efficiency in order to reduce fuel consumption. Recently, studies have been shifted from upgrading the engine to the auxiliary systems attached to it. Thermal management is one of the successful fields that has shown promise in minimizing fuel consumption and reducing pollutant emissions. Throughout this work, a four-cylinder turbocharged diesel engine model was developed on GT-Power. Also, a thermal code has been developed in parallel on GT-Suite, in which the different parts of the coolant and lubricant circuits were modeled and calibrated to have the best agreement with the temperature profile of the two fluids in the system. Once the model was verified, hot coolant storage, a thermal management strategy, was applied to the system to assess the fuel consumption gain. The storage tank was located downstream the thermostat and upstream the radiator with three valves to control the coolant flow. The place was chosen to avoid negative impact on the cold start-up of the engine when the tank is at the ambient temperature. This strategy was applied on different driving cycles such as the NEDC, WLTC, CADC (urban and highway), and an in-house developed driving cycle. The ambient temperature was varied between −7°C to represent the coldest winter and 20°C. The results of this study summarize the ability of the hot coolant storage strategy in reducing the fuel consumption, and show the best driving cycle that needs to be applied on along with the influence of the different ambient temperatures.

A territorial diagnostic of the french region Pays de la Loire through the prism of energy metabolism

The central focus of the research is on conducting a societal metabolism approach to the region of Pays de la Loire in France. For doing so, the Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) methodology is used where fund variables such as human activity and land use are correlated over flow variables, such as energy and gross added value following the theoretical framework of Georgescu-Roegen [1]. Thereafter the feasibility, viability and desirability of current development patterns for the region are questioned to be able to transition into alternative scenarios.

Impact of Mounting Blocks on Drivability

Precedent papers have shown that motor-block (i.e., electric motor and speed reducer) rolling motion onto its mounting blocks has an important effect on the drivability rating. The drivability aspect is crucial for an electric vehicle because of the high torque gradient at low speeds or between regenerative and motor modes. Within the context of the new European emission standard, automotive engineers have to focus their research on fuel-efficient vehicles. Therefore, many car manufacturers are directed toward zero-emission vehicles as a solution, hence the development of the electric vehicle. To lead this vehicle project from the very early design steps, it is very important to assess and optimize customer perception during vehicle use. We also need to assess the difference between the vehicle response to driver request and that expected from the driver himself. This aspect of vehicle customer perception is called drivability and is evaluated by numerous maneuvers such as tip-in and back out of the accelerator pedal (tip-out) or acceleration from a rest position (takeoff). During tip-in, the torque gradient causes oscillations of the driveline and a jerk of the vehicle. Moreover, precedent works have shown that torque excitation causes a roll motion of the motor block (i.e., the electric motor and speed reducer) onto its mounting blocks and therefore shocks on the vehicle acceleration.

Study of an optimization criterion of mounting blocks for drivability evaluation of an electric vehicle

In order to lead properly an electric vehicle project, it is very important to assess and optimize the driver perception during manoeuvres such as tip-in and tip-out. This aspect of vehicle customer perception is called “drivability”. Precedents papers have shown that the motor block (i.e. electric motor and speed reducer) rolling motion onto its mounting blocks has an important effect on the drivability rating. Moreover, this drivability aspect is crucial for an electric vehicle (because of the high torque gradient at low speeds or between regenerative and motor modes). A usual criterion used to study the impact of the motor block rolling on the drivabilty rating is the energy decoupling between roll and surge modes. This criterion, called “EcTx criterion” warrants to limit the oscillations of the longitudinal force transmitted from the motor block to the car body. As this criterion is independent of the torque command, it is used for any manoeuvre. Its application to a Key-On/Key-Off manoeuvre on conventional vehicle is well-known and enables to predict the rating of this manoeuvre. Nevertheless, questions are remaining about the appliance of this criterion to a tip-in manoeuvre. Simulations have shown that the EcTx criterion can also be used for a tip-in manoeuvre and gives a good prediction of the oscillations amplitude for the longitudinal force transmitted from the motor block to the car body. However, the driveline mode is also involved in the vehicle dynamics during a tip-in manoeuvre. Moreover, this paper shows that the oscillations of the motor block onto its mounting blocks can also damp the driveline mode oscillations thanks to a specific phase shift between the two modes. Therefore, EcTx criterion can be improved by taking into account the driveline equivalent stiffness and inertia into its calculation.