1. Field of the Invention
The invention relates to a device and a method for monitoring a high-pressure pump in a fuel supply circuit of the injectors of a turbine engine such as a turbojet or a turboprop engine.
2. Description of the Related Art
In a turbine engine of this type, the supply circuit of the fuel injectors comprises a combination of a low-pressure pump and a high-pressure gear pump, with the low-pressure pump providing the feed of the high-pressure pump in order to avoid cavitation phenomena, with the high-pressure pump supplying a flow and a fuel pressure which are sufficient to provide the supply of the injectors of the combustion chamber of the turbine engine, as well as the cooling of the lubrication liquid of the turbine engine and of an IDG (Integrated Drive Generator) system and the controlling of actuators of elements with variable geometry of the turbine engine, (such as in particular guiding vanes with variable setting).
The fuel supplied by the high-pressure pump passes through an FMU (Fuel Metering Unit) which comprises a flow regulating valve connected to a pressurising and shut-off valve, which itself is connected to supply ducts of the injectors.
In the presence of an electric control for opening, the pressurising and shut-off valve remains closed hydraulically as long as the pressure of the fuel at the outlet of the regulating valve does not reach a predetermined value, for example 19 bars.
The high-pressure gear pump is driven mechanically by the turbine engine and its rotational speed is proportional to that of the turbine engine. The flow and the fuel pressure at the outlet of this pump are determined by the rotational speed of the pump. It has been observed that as the pump ages, it was necessary to increase the rotational speed of the pump in order to maintain the flow and pressure of the fuel at predetermined values.
This can make it difficult or impossible to restart the turbine engine in flight when, for any reason whatsoever, the turbine engine has been stopped and must be restarted through the sole effect of the air which flows on the compressor and turbine blades due to the displacement of the aircraft (an assistance for the starter also able to be adopted at certain points in the area of starting). The high-pressure pump is in this case driven in rotation at a relatively low speed but must however provide a pressure and a flow of fuel that are sufficient to cause the hydraulic opening of the pressurising and shut-off valve and in order to provide for proper supply of the injectors of the turbine engine.
The wear and tear of the high-pressure pump, which results in a progressive decrease of the flow of fuel at the pump outlet for a given rotational speed and a determined pressure, must be monitored so that the pump is replaced before a restarting in flight becomes impossible.
Maintenance recommendations call for a replacing of the high-pressure pump around 12,000 hours of operation and do not make it possible to optimise the life cycles of these pumps because, on the one hand, the premature wear and tear of the pumps cannot be detected and, on the other hand, pumps which are still in good operating condition sometimes need to be replaced.