The potential of vortex amplifiers to improve mixture preparation in spark ignition engines.

Spark ignition engines are a significant source of air pollution. Emissions are
most severe in the period after the engine has been started from cold. This is because
fuel enrichment is needed to ensure reliable combustion in the cold cylinder. The
problem is compounded by the exhaust treatment catalyst not reaching operating
temperature until some minutes after starting. As the majority of car usage is for short
journeys, engines spend much of their time in this high emission operating regime.
One route to reducing emissions is to improve mixture preparation. This is
Particularly effective after a cold start as less enrichment is required to ensure
combustion. The aim of this project has been to evaluate a Vortex'Amplifier as a route
to improving mixture preparation.
The vortex amplifier is a no moving parts fluidic control device. It regulates a
large volume supply flow by imparting swirl to it with a small volume control flow.
The control flow vortex creates a region of highly turbulent flow at the device outlet
which possesses the potential to atomise a fuel spray.
The VA has been tested experimentally. The sprays produced by the vortex
amplifier were measured by a laser diffraction technique. Numerical analysis has also
been undertaken to determine the motion of droplets within the vortex chamber and the
potential of the flow to disrupt a fuel spray.
The vortex amplifier has been found to be a highly effective atomiser. It
produces sprays with a Sauter mean diameter approximately half the size of the best current technology. However the spray impacts on the walls of any pipework
downstream of the VA due to the high tangential velocities in the flow exiting the VA.
This problem currently precludes engine us'e, but suggestions for improving the
situation are contained in the recommendations for future work.