User Guide

11
Effects of Excess Air On Nozzle
Performance
Excess air in the system can be a trouble spot. Of course the burner
must have sufficient air to provide good mixing of air and fuel oil,
or you get incomplete combustion and smoke. Unfortunately, as
the amount of air is increased, the transfer of heat is reduced.
A delicate balance must be achieved between smoke problems
(caused by insufficient excess air) and reduced heat transfer
(caused by unnecessary excess air).
An air leak in the system also causes lost efficiency. It cools down
combustion gases, lowers temperature, and raises stack
temperature.
What Affects Droplet Size?
It is sometimes assumed that the smallest possible
droplet size is the most desirable for all
applications. While this may be true in some cases,
it doesn’t apply across the board. The safest
generalization that can be made is to find the
droplet size and distribution that produces the
quietest, most efficient combustion. Here are some
of the major factors affecting the droplet size.
•
Higher Flow Rate Nozzles usually produce larger
droplets, assuming pressure, fuel properties and spray angle
remain the same. A 10.00 GPH nozzle, for instance, will
produce larger droplets than a 5.00 GPH nozzle.
•
Wider Spray Angles produce smaller droplets
•
High Viscosity fuel produces larger droplets in the spray
at the same pressure.
•
Heating Fuel reduces its viscosity and produces smaller
droplets.
•
Increasing Fuel Pressure reduces droplet size.