GB1216913A - Pure fluid sensing apparatus - Google Patents

Abstract

1,216,913. Fluid-pressure servomotor systems. BENDIX CORP. April 30, 1968, No. 20381/68. Heading G3P. [Also in Divisions F1 and H4] An apparatus for sensing a variable condition of a relatively high-pressure fluid in a chamber 38 comprises pure fluid means T generating pressure oscillations of predetermined frequency which propagate through the high-pressure fluid, pure fluid sound receiving means R located in the chamber in spaced relationship with the means T and adapted to resonate at the predetermined frequency to produce corresponding output signals and pure fluid valve means A responsive to the output signals for generating an output pressure representative of the condition to be sensed, fluid control means O controlling the operation of the means T and valve A in timed relationship. The chamber 38 may be the discharge section of a combustion chamber 36 in a gas turbine and the variable condition may be temperature. The means O consists of a flip-flop oscillator having its output passages 49 and 51 connected to a vortex amplifier 80 controlling the outlet 70 from a Hartmann oscillator 64 and to a control port 138 of the valve A. A second control port 120 is connected through a duct 116 having a series of resonant chambers 122, 124, 126 with a tube 118 situated at the focal point of a reflector 112 and adapted to resonate at the frequency of the oscillator 64. Whenever a pulse is applied by the flip-flop oscillator to the port 138, a lack of pressurized fluid occurs at a control port 90 of the vortex amplifier permitting hot combustion gas to flow through the oscillator 64 and excite the gas 74 in a plug 72 into a selfoscillation to produce a series of gas pressure waves at the tube 118 to produce a pulse in the port 120 opposing that from the port 138 and causing a control jet 134 to be deflected from a passage 140 to a passage 136. The time during which the power jet is biased to passage 140 is proportional to the time taken by the pulse to travel from the generator to the receiver and to the square root of the temperature of the gas in the chamber 38. The flow through the passages 136 and 140 may be time integrated by restrictors 144, 146, 150 and 152 and by chambers 142 and 148 to provide a pressure differential P 1 -P 2 which is a function of temperature. A diaphragm 60 connected to a fuel control for the turbine is actuated by this differential to maintain the gas temperature at the required value.