NOZZLE MIX SYSTEMS
If the chamber is under pressure, subtract it from the "available outlet pressure" and the "air pressure" before figuring percent impulse required. (Add if chamber is under suction.) If the chamber pressure were + 2 osi for the above example, (8 — 2) ÷ (16 — 2) = 6 ÷ 14 = 43%; so set the bleed for an impulse of 43% or less.
air
5D
3D
combustion chamber
± 2 osi
4 pipe dia.
10 pipe dia.
EFFECT OF PRESSURE OR SUCTION IN COMBUSTION CHAMBER ON CONTROL WITH A STRAIGHT CROSS-CONNECTED SYSTEM
Pressure or suction in the combustion chamber is communicated to both sides of the control diaphragm of the air/gas ratio regulator, through impulse air line to regulator, and through main gas line to regulator balancing tube. Since pressures on the diaphragm are balanced, air/fuel ratio will not be affected by combustion chamber pressure (or suction).
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