Fuel-Air Ratios in a Spray, Determined between Injection and Autoignition by Pulsed Spontaneous Raman Spectroscopy

Quantitative, ensemble averaged, two dimensional maps of the fuel-air ratio in an injection jet were obtained through a series of single point Raman measurements. Pure n-heptane was injected with a commercial injection system into a special high pressure (45 bar) and high temperature (500 °C) observation chamber. The investigations were performed between injection and autoignition of the spray, and between 15 mm and 48 mm below the nozzle.

On the basis of nearly 100,000 single point measurements a computer film was produced showing that faster propagating fuel in the inner spray and at the spray tip plays an important role in mixture formation.