Controlling method and system for compressed air supply to a pneumatic network, in particular in an aircraft
A system for supplying compressed air to a pneumatic network includes a load compressor, an air supply and a power shaft driving the load compressor. The system also includes in an air outlet of such load compressor, a connecting channel connected, on the one side, with a channel connected with the pneumatic network and, on the other side, with an air discharge conduct towards an exhaust nozzle. Air flow rate bleed valves are controlled by a processing unit via servo-loops as a function of the pressure sensors and the speed sensor.
1. A method to control a compressed air supply to a pneumatic network, wherein the compressed air supply is provided by a load compressor, and in a compressed air outlet of the load compressor, a connecting channel is connected, on one side, with a channel connected with the pneumatic network and, on another side, with an air discharge conduit connected with a gas exhaust system, the method comprising:
controlling the compressed air supply as a function of instantaneous needs of the pneumatic network by discharging all compressed air not being consumed by the pneumatic network towards the gas exhaust system, via the air discharge conduit, depending on an air pressure supplied to the pneumatic network,
operating the load compressor, at a given flight point, at a constant operation point, independent of the instantaneous needs of the pneumatic network,
controlling a valve that regulates air access into the load compressor in opening and closing positions according to an open or closed position of a valve at an inlet of the pneumatic network, and
wherein controlling the compressed air supply as a function of the instantaneous needs of the pneumatic network further comprises controlling air flow rate bleed valves, using a data processor, as a function of measurements of the air pressure supplied to the pneumatic network made by a pressure sensor arranged on the channel connected with the pneumatic network, one or more of the air flow rate bleed valves being arranged at an inlet to the load compressor and comprising the valve that regulates air access into the load compressor, one or more of the air flow rate bleed valves being arranged on the channel connected with the pneumatic network, and one or more of the air flow rate bleed valves being arranged on the air discharge conduit.
2. The method according to claim 1 , wherein controlling the compressed air supply as a function of the instantaneous needs of the pneumatic network further comprises discharging all compressed air not being consumed by the pneumatic network towards the gas exhaust system when the air pressure supplied to the pneumatic network is at a given set point pressure.
3. The method according to claim 1 , wherein the one or more air flow rate bleed valves arranged on the air discharge conduit is at least one of a proportional controlling valve positioned based on a predetermined range around a set point pressure, an anti-surge valve, and a safety valve calibrated at the set point pressure.
4. The method according to claim 1 , wherein the one or more air flow rate bleed valves arranged at the inlet to the load compressor and the one or more air flow rate bleed valves arranged on the channel connected with the pneumatic network are valves settable at either of two extreme open and closed positions.
5. The method according to claim 1 , wherein the one or more air flow rate bleed valves arranged at the inlet to the load compressor is one or more inlet guide vanes or inlet guide valves.
6. The method according to claim 1 , wherein a power shaft drives the load compressor in rotation, and the power shaft is a mechanical power shaft of one of an APU unit gas generator, a terrestrial motive unit, a machine tool, a piston engine, or an electrical engine.
7. The method according to claim 6 , further comprising controlling a speed of the mechanical power shaft of the APU unit gas generator by a measuring device for a fuel flow rate being injected into a combustion chamber of the APU unit gas generator, the fuel flow rate being adjusted so that the speed of said mechanical power shaft measured by a speed sensor corresponds to a constant set point value.
8. The method according to claim 1 , wherein the controlling the valve that regulates air access into the load compressor includes controlling the valve that regulates air access into the load compressor in only two positions, which are the open and closed positions, according to the open or closed position of the valve at the inlet of the pneumatic network.