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Technical Paper

Reacting Boundary Layers in a Homogeneous Charge Compression Ignition (HCCI) Engine

An experimental and computational study of the near-wall combustion in a Homogeneous Charge Compression Ignition (HCCI) engine has been conducted by applying laser based diagnostic techniques in combination with numerical modeling. Our major intent was to characterize the combustion in the velocity- and thermal boundary layers. The progress of the combustion was studied by using fuel tracer LIF, the result of which was compared with LDA measurements of the velocity boundary layer along with numerical simulations of the reacting boundary layer. Time resolved images of the PLIF signal were taken and ensemble averaged images were calculated. In the fuel tracer LIF experiments, acetone was seeded into the fuel as a tracer. It is clear from the experiments that a proper set of backgrounds and laser profiles are necessary to resolve the near-wall concentration profiles, even at a qualitative level.
Technical Paper

Simple Feedback Control and Mode Switching Strategies for GDI Engines

A novel approach to the control of a GDI engine is presented. The controller consists of a combination of sub-controllers, where torque feedback is a central part. The sub-controllers are with a few exceptions designed using simple linear feedback and feedforward control design methods. Special mode switch strategies are used to minimize the torque bumps during combustion mode changes. The controller has been evaluated on the European driving cycle using a dynamic simulation model, including a powertrain model and a driver model, with good results.