| 摘要 |
<p>1432022 Preventing compression surge UNITED AIRCRAFT CORP 2 July 1973 [20 July 1972] 31407/73 Heading F1C An anti-surge valve in a compression discharge line is operated by a first control responsive to the mass flow through the compressor, and a second control responsive to the rate of change of static pressure at the reduced area section of the compressor diffuser, the two controls acting independently or concomitantly on an actuator for positioning the valve, and the second control acting more rapidly than the first. An aircraft cabin air conditioning compressor 12 supplies air to a duct 16 via a diffuser 52 and a check valve 18, surge at low air-flow being prevented by a blow-off valve 22 operated by a servo actuator 24 of half area type. Engine bleed air is supplied from a line 31 at full pressure to the half-area chamber 32 of the actuator 24 and at reduced pressure to the fullarea chamber 34 via a potentiometer consisting of a restrictor 26 and a vent valve 30 which is held open by a diaphragm 56 subjected to a pressure rise P t -P s occuring in the diffuser 52. When the mass flow through the compressor is reduced towards the surge condition, the resultant reduction of the diffuser pressure rise acting on the diaphragm 56 allows the vent valve 30 to close, thereby increasing the pressure in the chamber 34 whereby the actuator 24 opens the blow-off valve 22. A normally closed valve 28 for admitting engine bleed air at full pressure to the chamber 34 via lines 88, 64 is actuated by a diaphragm 72 subjected to the pressure P S directly on one side and via a restrictor 82 on the other side. In the event of a sudden reduction of mass flow through the compressor, the resultant rapid rise of the pressure P S causes a temporary inequality in the pressures on the two sides of the diaphragm 72, whereby the valve 28 is opened to provide rapid opening of the blow-off valve 22.</p> |
