| 摘要 |
<p>1504045 Fluid-flow compressors; gas turbine engines UNITED AIRCRAFT CORP 4 April 1975 [4 April 1974] 13960/75 Headings F1C and F1G The compressor bleed valves 16 of a gas turbine engine are controlled by a steady-state control 10 so as to be open at corrected compressor speeds of up to 60 per cent of the maximum value and to be closed at corrected compressor speed of 70 per cent and above, this control being over-ridden by a control 12 which opens the bleed valves during acceleration or deceleration. The steady-state control 10 comprises a three-dimensional cam 48 which is translated and rotated as a function of compressor speed and compressor inlet temperature. The cam 48 actuates a leak-off valve 22 connected downstream of a restrictor 31 in a line 28, 30, 32 which is connected to the compressor so as to control an actuactor 14 which operates the bleed valves 16. The line is also connected to chambers 70, 72 on opposite sides of a diaphragm 76 of the control 12, a restrictor 74 being interposed in the correction to the chamber 70 whereby change in the compressor pressure during acceleration or deceleration causes a temporary inequality in the pressures in the chambers to displace the diaphragm, thereby opening one or other of two leak-off valves 24, 26 to cause the actuator 14 to open the bleed valves 16. Diaphragms 80, 82 associated with the valves 24, 26 serve, since they are in communication with the atmosphere via the vent passages 92, 94 of the valves, to provide altitude compensation. The effect on the control 12 of the decrease in the compressor pressure which results from the opening of the bleed valves 16 is neutralized, wholly or in part, by a leak-off valve 100 located downstream of a restrictor 108 and closed by a cam 102 on the plunger of the actuator 14 when the bleed-off valves are opened. The rate of change of fuel flow rather than the rate of change of compressor pressure may be used as the controlling factor.</p> |
