The quality of fuel in the STF

For engines with FCC provides off afterburner pump FN on unforced engine operating modes, as well as the forced modes for low fuel consumption during flight at high altitudes, where due to the strong decrease in pump efficiency FN comes great fuel heating.

Reduction of heating fuel in the STP helps increase the efficiency of the pumps, reducing pressure losses on the controller and the differential pressure on the nozzles.

The fuel quality in the STP is determined not only by the degree of its contamination, but also by the presence of water and free air in it. In operation under the influence of vibrations, free air can be captured from the interface in the fuel tanks and its movement in the pipelines in an amount up to 1,5% of the volume. The presence of air and water also impairs the lubricity of the fuel and leads to increased wear of friction parts. In addition, this can lead to the occurrence of oscillatory processes in the system. To reduce the effect of air on the performance of the units in the pipelines of STF, there should be no areas in which air can accumulate.

One of the important ways to improve STF is the use of pumps with adjustable capacity in them. The possibilities for controlling the productivity of pumps are associated with controlling the speed of the pumping unit of pumps, changing the geometry of the flow part (in centrifugal pumps), etc. The methods for controlling the rotational speed can be different, for example, using a gas turbine (turbo-pump unit), a regulated hydro-converter, electric drives. Variable eccentricity and a centrifugal pump with a steam core that have been regulated by their productivity have not been extended due to insufficient resource, it is promising to use electric motors with variable speed for driving pumps. The regulation of pump capacity by controlling the speed of their drive allows to obtain a number of significant advantages: reduce fuel heating due to exclusion of fuel bypass from

output to the input of the pump; extend the life of pumps due to the fact that up to 90% of the flight time cycle variable performance pumps operate at lower pressures and low speeds in relation to their maximum values. Also facilitated the launch of GTD, as the performance of the fuel pump is not related to engine speed.

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