Eclipse Combustion Engineering Guide - Burnerparts

Tech Notes
Section
2
Sheet C-4
Nozzle Mixing Burners
Ratio Control Using Cross-Connected Proportionators
Operating Principle
Burner air passage is fixed resistance for air flow. Gas passages in the
burner are usually too large to serve as the fixed resistance, so a limiting
orifice valve is installed at the gas inlet . At setup, this valve is adjusted to
provide the correct gas flow when gas pressure (2) is equal to air pressure
(1). Low fire gas-air ratio is set with spring in Proportionator.
1
Advantages
FUEL
3
Cross
Connection
Proportionator
• Easy to set up. Once high and low fire ratios are set, everything in between
is taken care of.
• Can be used with proportioning or high-low control systems.
• No problem with mismatched valve flow curves. Proportionator is slave to
air valve and automatically matches its characteristic curve.
• Fuel-air ratio is unaffected by unforeseen changes in combustion chamber
pressure.
2
Limiting
Orifice
• Although air starvation due to a plugged filter or dirty blower wheel will
cause a loss in firing capacity, it will not cause the system to go rich. The
proportionator automatically reduces fuel flow as the air flow drops off.
• On multiple burner systems fed from a single air control valve and
proportionator, changing or shutting off the fuel flow to one burner will
not upset the fuel flow to the others. This makes initial setup easier and
eliminates the hazard of burners in a zone going rich because one of
them has been misadjusted or shut off.
• If proportionator permits, this system can be converted to an excess air
system (see page 95) with a simple proportionator spring adjustment.
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