Diagnostic investigations of turbojet injectors

The basic aim of injectors is to supply a specified amount of fuel to the turbine engine combustion chamber. The fuel should be atomized to the extent which enables its evaporation and helps to produce a homogenous mixture of fuel vapour and air, thus ensuring high efficiency of the combustion process. The article contains the review of methods and diagnostic equipment used in Aviation Overhaul Works (Lotnicze Zakady Remontowe) in assessing the suitability of turbine jet as well as turboprop and helicopter engines sprayers. Injectors are evaluated on the basis of their fuel delivery Q(p) which determines the volume of fuel sprayed in the time unit, the spray cone angle (p) and the parameter J(p) which describes the asymmetry in the circumferential spray density distribution j(). These parameters are dependent both on structural characteristics of the sprayers as well as on fuel delivery pressure p in the fuel supply pipe. In the standard diagnostic stations, the measurement of fuel delivery Q(p) is carried out only for the two fuel supply pressures, corresponding to the extreme engine ranges, that is the rotational speed of the idle running nbj and maximum rotational speed nmax. Injectors undergo the leak test at the fuel pressure 5 to 10 times bigger than the nominal value. Tolerances adopted by the producers for the measured parameters characterizing the injectors are also presented.