by BrokenAeroVT » Sat Sep 19, 2009 12:19 am
Turbulent flow around the pot is more desirable because the boundary layer allows for greater heat transfer between the gas and the pot.
The purpose of jets is to draw in air by the Venturi Effect. Fast moving air creates vacuum that draws air into it. If the flame has no jet to draw air in, the flame will grow to increase the area of the combustion surface until it does burn up. If it grows too large, the flame cools and becomes yellow. A compact hot blue flame is more desirable.
The type of jet determines how much velocity is conserved. If the jet is just a hole in sheet aluminum, the velocity will drop 60% due to the back pressure created outside the hole. Nozzles are more efficient, keeping about 98% of their velocity for the same flow. A faster jet draws in more air.
A brilliant blue flame with a violet aura is ideal and indicates that a jet is drawing in a stoichiometric balance of air to fuel. The air to fuel ratio for methanol is 6.45 : 1. Increasing that 5 to 10% is common practice to guarantee full combustion.