Identification of Suitable Ignition Conditions for Stable Switch from SI to HCCI of a Blowdown Supercharged Engine

In this paper, the necessary in-cylinder conditions for the transition from spark ignion (SI) to homogeneous charge compression ignition (HCCI) are analyzed. The hereby important factors for ignition time are investigated analytically. A control oriented combustion model, that is validated by experimental data, is used for sensivity analysis and a Monte-Carlo approach is taken to identify the important factors for transient HCCI and combustion mode switch. As a result, it was shown that the in-cylinder temperature plays a major role, exceeding other factors, such as the air-fuel ratio. The analytical conclusions are illustrated by numerical simulations after which the feasibility for actuation will be discussed. Final goal is to ensure a stable combustion in each cycle without crossing unstable combustion conditions

Control-Oriented Modeling and Model-Based Control of a Blowdown Supercharge (BDSC) HCCI Engine

Closed-loop control is vital for an application of HCCI engines in passenger cars. This paper introduces a simplified control-oriented model for control of combustion phasing and IMEP of a Blowdown Supercharge Engine (BDSC). Despite the complexity of this particular engine, the model has been found to match not only the steady state values in high load HCCI, but also to reproduce the transients. This model takes advantage of the knowledge of non-dynamic processes within the engine that can be derived from steady state values, while the main dynamics are achieved by dynamically modelling of cyclic coupling via in-cylinder temperature alone and mean exhaust pressure dynamics. Furthermore, a simplified combustion model has been found to be accurate enough for the region of interest. An automated tuning scheme helps to match the model to the respective target values. With this model and the tuning scheme, the model can be easily tuned for every possible case. A model-based MIMO state controller, based on Sliding-Mode Control theory has been designed and tested on a detailed 1-D simulation code

Thresholdless Lasing of Nitride Nanobeam Cavities on Silicon

We present a temperature dependent optical and quantum-optical characterization of close-to-ideal lasing in GaN-based nanobeam cavities. Measuring the photon statistics of emission allows us to prove high-beta lasing at room temperature, and thresholdless lasing at 156K. Thresholdless lasing is explained via temperature dependent carrier redistribution in the 0D/2D gain medium