Patent GB-1306094-A (GB)
IPC: F02D3/00
Filed: 1970-04-20
Abstract: 1306094 Fluid logic and switching circuits; spray carburettors BENDIX CORP 20 April 1970 [23 April 1969] 18790/70 Headings F1B F1P Fuel delivered by an engine driven pump 56 Fig.1 to a flow divider 68 connected to injection nozzles 28 downstream of a valve-controlled air inlet 30 of an I.C. aircraft engine forms the supply input 58 Fig.2 of proportional fluidic amplifiers A5, A6 having control input signals at 228, 236 and 352, 356 which are generated by further fluidic amplifiers A1 to A4 and A7 to A12 in response the exhaust gas temperature T E  in manifold 38. Supply input ducts 72 of oscillator A1, bistable A2 and monostable A3 are constantly open to ambient air pressure whilst supply ducts 76 of proportional A4, and bi-stable A7 are open to ambient air pressure only when a spool valve 78 is in the "full rich" i.e. starting position shown and which valve then closes the ambient air supply ducts 74 of A8 to A12 until the valve is moved to the "best power" i.e. cruising position. The outputs of each air-supplied amplifier are maintained at sub-atmospheric pressure by an engine-driven vacuum pump 84. In operation with valve 78 in the position shown and wherein A8 to A12 are unoperative, A1 which is an oscillator generates 180 degrees out of phase pulses of predetermined frequency and which provide control inputs thereof at 190, 192 are exposed to exhaust manifold and ambient air temperatures T E , T A , respectively. The resulting output pulses are thus phase shifted in accordance with T E /T A  and forms control inputs at 198, 200 for monostable A3. The pulsed output at 204 passes to inoperative A8, whilst pulsed output at 206 is attenuated at 212, 214 and the resulting more uniform pressure is applied to a control port 210 of proportional A4 in opposition to a reference pressure at 215 corresponding to a predetermined reference temperatures T R  i.e. a desired exhaust temperature. This reference pressure is obtained by restrictions 218, 220 in a line 216 connecting ambient air pressure pipe 76 and vacuum pipe 90. The resulting output pressure differential at 222, 230 corresponds to the difference between the actual exhaust temperature T E  and the desired temperature T R  and these pressures are directed through lines 224, 232 as signals to control ports 236, 228 of proportional A5. These signals are amplified at A5 and form the control inputs 224, 248 of A6, the output 250 of which leads to flow divider 68 and output 252 to the return reservoir 52. Proportional A4 is subjected to a further control input biasing signal at 256 obtained from output 260 of bi-stable A7 following an abrupt opening of valve 32 calling for an increase in fuel supply. The control inputs 262, 264 of A7 are each connected through restricted lines 266, 268 to ambient air pipe 76 and air inlet manifold pipe 270 but line 266 contains a capacitor 280 whereby a sudden increase in Pm in line 270 temporarily biases the output of A7 into line 258 loading to control port 256 of A4 which results in increased fuel flow. With spool valve 78 moved to "best power" position A4 and A7 become inoperative and the output pulses at 204 are attenuated at 286, 292, 296 and fed to control inputs 302, 304 of bi-stable A8. A capacitor 300 in line 288 leading to 302 causes the pressure to vary in response to rate of change of exhaust gas temperature. Thus a temperature rise increases pressure at 304 and switches A8 to output 306 which latter is fed to control inputs 310, 314 of monostable A9, A10. The outputs of A9, A10 are directed along 320, 326, to control inputs 322, 324 of monostable A11 which has outputs 330, 332 connected by line 350, 354 to further control inputs 353, 356 of proportional A5.