Joint project High Load EGR

  Copyright: © IRT

Air path control for two-stage turbocharged gasoline engines with exhaust gas recirculation

The aim of this project is to provide a universally applicable and easy-to-use engine control system for turbocharged gasoline engines with high-load exhaust gas recirculation. The focus is on the development of innovative algorithms for controlling the exhaust gas recirculation rate and boost pressure, which enable process control of exhaust gas recirculation systems with minimal application effort.

 

Motivation

In the gasoline engine, "downsizing" has become established on the market as a means of reducing fuel consumption. In recent years, the displacement has therefore been continually reduced, but at the same time the torque has been continuously increased to meet the increasing demands for driving performance and comfort. Due to the high degrees of turbocharging required for this, the probability of knocking combustion increases, which is why it is not possible to achieve optimum combustion efficiency over a wide operating range. In addition, the large mass flows in relation to the displacement result in very high exhaust gas temperatures. High-load exhaust gas recirculation is a promising technology for reducing exhaust gas temperatures and achieving a more efficient center of combustion. With these systems, the residual gas content can be increased independently of the internal engine process and control variables via a separate exhaust gas recirculation valve and thus the inert mass of the cylinder charge.

 

In combination with external exhaust gas recirculation, multistage turbocharging systems offer great potential for resolving the conflicting goals of good responsiveness and high maximum power combined with low fuel consumption and low pollutant emissions. However, due to the complex process control and the associated high application effort, these complex air path architectures in gasoline engines are currently still the subject of research.

 

Project Goals and Methods

Copyright: © IRT Design of the air path concept with two-stage exhaust gas turbocharging and low-pressure exhaust gas recirculation

In this project, different variants of a model-predictive control system for the process control of a two-stage turbocharged gasoline engine with low-pressure exhaust gas recirculation were researched and developed. A data-based model and a physics-based model were developed to represent the system behavior within the control system. Both models were combined with a linear and in a nonlinear optimization and compared with each other with regard to model accuracy, required computing power and achievable control performance. The data-based model delivers sufficiently good control results for most applications with very little effort for model development and identification. Compared to the data-based approach, the physical model is characterized by a higher model accuracy and, in combination with a nonlinear optimization, provides the best control results with acceptable computational requirements, but requires more application effort.

 

Innovations and Perspectives

The development environment for model predictive control provided by the research centers can be used by small and medium-sized companies to test their own components for the air path of gasoline engines on the engine test bench or in the vehicle with very low cost and application effort. The application range of the control system is not limited to the air path investigated in the research project, but can be extended to include any air path architecture.

 

Acknowledgements:

The research project was carried out at the Chair of Combustion Engines Aachen at RWTH Aachen University under the direction of Prof. Dr.-Ing. Stefan Pischinger and at the Institute of Control Engineering at RWTH Aachen University under the direction of Prof. Dr.-Ing. Dirk Abel. It was financially supported by the German Federal Ministry for Economic Affairs and Energy (BMWi) via the German Federation of Industrial Research Associations (IGF) - funding no. 19381 N - on the basis of a resolution of the German Bundestag and was accompanied by a working group headed by Dr.-Ing. Thorben Walder (Dr. Ing. h.c. F. Porsche AG). The authors would like to thank the sponsors, the Forschungsvereinigung Verbrennungskraftmaschinen e.V. (Research Association for Combustion Engines) and all project participants for their support of the project.

We would also like to thank Embotech AG both for providing their algorithms for solving nonlinear programs and for actively supporting the real-time implementation.

 

Project partner
RWTH Aachen University, tme - Lehrstuhl für Thermodynamik mobiler Energiewandlungssysteme Embotech AG FVV - Forschungsvereinigung Verbrennungskraft­maschinen e.V.