Water injection

#This application claims priority from United Kingdom Patent Application Numbers 2003094.6 and 2003095.3, both filed Mar. 4, 2020, the whole contents of which are incorporated herein by reference in their entirety.

#This disclosure concerns aircraft gas turbine engines with water injection systems, and methods of operation thereof.

#Combustion of hydrocarbon fuels in aero engine combustion systems produces a hot exhaust stream composed primarily of nitrogen, oxygen, carbon dioxide and water vapour. In addition to these major components, a quantity of soot is also produced in locally-rich flame zones, along with thermal nitrogen oxides and sulphur oxides. Unburnt hydrocarbons and carbon monoxide may also be emitted in very low concentrations, together with trace quantities of other particulates.

#Embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

#FIG. 1 shows two aircraft in flight, one of which has a pair of engines configured as set out above;

#FIG. 2 shows a general arrangement of one of the engines of FIG. 1;

#FIG. 1

#Two aircraft 101 and 102 are illustrated in FIG. 1 in formation at substantially the same flight level and in substantially the same atmospheric conditions.

#Aircraft 101 comprises two engines 103 which, due to their configuration and operating point, are forming contrails 104. Aircraft 102 comprises two engines 105 which are configured in accordance with the present disclosure, and are thus forming contrails 106 having a lower optical depth than contrails 104. As will be described herein, the engines 105 include functionality so as to allow the optical depth of any contrails they produce to be modified.