FUEL HEATING

96. The spill spray nozzle system, however, involves a somewhat modified type of fuel supply and control system from that used with the previous types. A means has to be provided for removing the

spill and also for controlling the amount of spill flow at various engine operating conditions. A

disadvatage of this system is that excess heat may be generated when a large volume of fuel is being recirculated to inlet. Such heat may eventually leadto a deterioration of the fuel.

FUEL HEATING

FUEL HEATING

100. On many engines, a fuel-cooled oil cooler (Part 8) is located between the L.P. fuel pump and the inlet to the fuel filter (fig. 10-13), and advantage is taken of this to transfer the heat from the oil to the fuel and thus prevent blockage of the filter element by ice particles. When heat transference by this means is insufficient, the fuel is passed through a second heat exchanger where it absorbs heat from a thermostatically controlled airflow taken from the compressor.

EFFECT OF A CHANGE OF FUEL

101. The main effect on the engine of a change from one grade of fuel to another arises from the variation of specific gravity and the number of heat units obtainable from a gallon of fuel. As the number of heat units per pound is practically the same for all fuels approved for gas turbine engines, a comparison of heat values per gallon can be obtained by comparing specific gravities.