Analysis of the Flame Radiation in SI Engines for Abnormal Combustion Phenomena

Frank Wytrykus, Dr.-Ing.
SMETEC GmbH, Erkelenz, Germany

Zhifeng Li , M.Sc.
Sonus Technologies, Hong Kong, China



With combustion processes in the otto-engine becoming increasingly complex, specialized optical measurement techniques have been developed to gain insight into individual events in ignition and flame propagation, as well as the intricate interplay of these events in the engine combustion process. The measurement techniques are multifold, and range from elaborate laser controlled methods to pragmatic solutions adopting optical sensors built into industrial spark plugs.

This paper illustrates how a methodical analysis could be conducted using data on light radiation captured by an optical spark plug during combustion. We will also present detailed measurement data with the complete spectrum of anomalous combustion phenomena, in particular:

- Pre-ignition
- Knocking combustion

By means of time courses of signal, we will demonstrate how the mixture is being ignited before the actual ignition process, which leads to a HCCI combustion with a powerful combustion wave. These waves could be wrongly taken for a knocking combustion. On the other hand, valuable data obtained from optical diagnostics shows how, in fact, the pre-ignition ended in a knocking combustion.

The complexity of the subject-matter shows that there is no singular, straight-forward optical combustion analysis, as the combustion process is a manifold phenomena.