Impact analysis of fuels, operating fluids and combustion parameters: focus raw emission behavior

Abstract

The future worldwide emission legislation is posing a challenge for the powertrain development especially in regards to emission reduction under real driving conditions. To achieve the targets a suitable development methodology, the usage of simulation tools and dynamic measurement equipment, as well as a detailed understanding of the physical phenomena and mechanisms are essential.

For evaluation of a powertrain under worst case boundary conditions RDE cycles and synthetic cycles are generated on the basis of real driving data from stationary and dynamic analysis and implemented on the test stand by support of a simulation model for vehicle, cycle profile and different boundary conditions. As an example combustion process and calibration strategy in regards to mixture formation, fuel/wall film interaction were investigated due to RDE sensitivity. The calibration over the complete operating map relevant for RDE requires a systematic methodology with Design of Experiments (DoE). A significant influence as well as optimization potential was identified by investigating the influence of hydraulic and chemical characteristics of both, fuel and oil on the restriction of calibration parameters with regard to the target figures combustion efficiency, emissions and combustion stability. Depending on the specific formulation and even interaction of fuel and oil there is a significant restriction in combustion parameters, compromising combustion efficiency.

The results show the influence on the particle formation based on an example with mixture formation parameters. Coming from the higher dynamic shares within real driving, new areas for optimization unfold, especially during transient engine. In order to comply with the future legislative boundary conditions, the quality and speed of the air and fuel path control must be realized with lowest possible spray-wall interaction.

The APL Group has developed a complex chain of methods and tools with the focus on RDE capability. The basis is the repeatable implementation of representative real driving conditions on powertrain and engine test beds. The so gathered data is used for further analysis in regards to operation parameters and especially the interaction between fuel and oil formulation for holistic combustion process optimization.