Cycle Resolved LDV Measurements on a Fired SI-Engine at High Data Rates Using a Conventional Modular LDV-System

LDV measurements were carried out on a single cylinder SI research engine. A special cylinder head has been designed allowing several alternatives for optical access. Development work has also been done in the choice of the material and preparation of the seeding particles. A number of modifications on the experimental apparatus and the optical system have been implemented to improve signal quality.

LDV measurements of two velocity components have been taken at engine speeds up to 2000 rpm with a variation of engine parameters such as load, intake valve lift and air-fuel ratio. For the first time mean data rates of 40 kHz over the entire engine cycle, peaking to 100 kHz around TDC, could be achieved at a very good S/N-ratio. LDV-data could also be observed at the flame passage and in the burned gas zone.

Turbulent flame propagation within single combustion cycles was investigated. Definitions of mean velocity and the fluctuation component were analysed and correlations between turbulence intensity and burning speed were found.