| 摘要 |
A fuel control system independently meters fuel flow to a first and a second set of pilot fuel nozzles, and to a set of main fuel nozzles. A pilot coaxial metering and pressure regulating valve is coupled between a primary fuel inlet line and the first and second sets of pilot nozzles, and a main coaxial metering and pressure regulating valve is coupled between the primary fuel inlet line and the set of main fuel nozzles. Each coaxial metering and pressure regulating valve maintains a substantially constant pressure drop across the respective valve, and includes a metering window. The size of each metering window is controlled by an engine electronic control unit based on the signals transmitted by a respective LVDT, in order to precisely meter the fuel flow through the valve and to the respective sets of fuel nozzles. A control pressure regulating valve maintains a minimum pressure differential between the fuel inlet line and the downstream sides of the coaxial metering and pressure regulating valves, in order to provide sufficient pressure to operate the valves, and directs excess fuel from the fuel pump into a return line. A minimum pressure and shut-off valve is coupled between each coaxial metering and pressure regulating valve and the respective fuel nozzles, in order to maintain a minimum fuel pressure level, and to terminate fuel flow to the nozzles. A sequence valve is coupled to the minimum pressure and shut-off valves to control actuation of the valves.
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