Flame impingement is when a flame actually touches or engulfs the tubes or their supports. When flame impingement occurs for even a short duration, damage is done. Consequences can include failures in tubes that carry process fluids, tube supports, refractory, burners, casing and structural integrity.
What is direct flame impingement?
In the Direct Flame Impingement (DFI) process, oxy-fuel flames directly heat the moving metal strip. The resulting heat transfer can be up to ten times higher than in conventional fuel fired furnaces. Characteristic of the process is that the material temperature rises very quickly within a compact furnace body.
What does flame impingement cause?
Flame impingement ultimately leads to reduced operational efficiency due to incomplete combustion. This can drive the boiler control system to increase the firing of the furnace to meet the outlet temperature requirement, leading to problems in areas not directly affected.
What causes flame lift on boilers?
In most cases, the sequence of events that leads to flame rollout in gas boilers begins with gradual accumulation of soot or dislodged rust inside the narrow flue passages of the heat exchanger. These passageways convey combustion gases to the vent pipe where they’re exhausted out of the home.
Is direct flame impingement a fourth method of heat transfer?
There are three basic ways in which heat is transferred. They called this fourth method of heat transfer as auto exposure or direct flame impingement. This method is just an illustration of many practical experiences though not yet accepted by the scientists.
What is flame chilling?
Flame chilling. An excess of cold air in one part of the flame envelope caused by maldistribution of air around the atomizer.
Why is flame lift-off?
If the jet velocity is further increased, the flame moves downstream to a position where it stabilizes. Lift-off height is the distance between the lifted flame base and the jet exit. When the jet velocity reaches the blow-out velocity, the reaction cannot be sustained and the flame is extinguished.
What can cause a flame roll out?
How Does It Happen? Flame rollouts in gas furnaces and boilers are caused by a high concentration of combustion gases inside the combustion chamber. Normally, these inflammable gases are exhausted from the furnace through the flue passageways in the heat exchanger, then up the vent to the exterior of the home.
