Showing posts with label FUEL PUMPS. Show all posts
Showing posts with label FUEL PUMPS. Show all posts

Wednesday, February 22, 2012

Fuel requirements


Fuel requirements

107. In general, a gas turbine fuel should have the following qualities:

(1)  Be 'pumpable' and flow easily under all operating conditions.
(2) Permit engine starting at all ground  conditions and give satisfactory flight relighting characteristics.
(3)  Give efficient combustion at all conditions.
(4)  Have as high a calorific value as possible.
(5)  Produce minimal harmful effects on the combustion system or the turbine blades.
(6)  Produce minimal corrosive effects on the fuel system components.
(7) Provide adequate lubrication for the moving parts of the fuel system.
(8)  Reduce fire hazards to a minimum.

108. The pumping qualities of the fuel depend upon its viscosity or thickness, which is related to fuel temperature, Fuel must be satisfactory down to approximately -50 deg. C. As the fuel temperature falls, ice crystals may form to cause blockage of the fuel filter or the orifices in the fuel system. Fuel heating and anti-icing additives are available to alleviate this problem.

LOW PRESSURE FUEL SYSTEM

LOW PRESSURE FUEL SYSTEM


83. An L.P. system (fig.10-13) must be provided to supply the fuel to the engine at a suitable pressure, rate of flow and temperature, to ensure satisfactory engine operation. This system may include an L.P. pump to prevent vapour locking and cavitation of the fuel, and a fuel heater to prevent ice crystals forming. A fuel filter is always used in the system and in some instances the flow passes through an oil cooler (Part8). Transmitters may also be used to signal fuel pressure, flow and temperature (Part 12).

FUEL PUMPS


84. There are two basic types of fuel pump, the plunger-type pump and the constant-delivery gear-type pump; both of these are positive displacement pumps. Where low pressures are required at the fuel spray nozzles, the gear-type pump is preferred because of its lightness.