Fifty years of gas turbine fuel injection

As its title suggests, this article is devoted to developments in gas turbi ne fuel injection diving the past half-century. It describes in general ter ms the evolution of pressure atomizers front the simplex nozzle of the 1940 s to the dual-orifice injector that remained in widespread use for over 20 years until it was replaced by the various forms of airblast atomizer that dominated the scene for the next three decades. The pressure nozzles descri bed herein include simplex, duplex, dual-orifice, fall-spray, and spill-ret urn. The inherent design flexibility of the airblast concept encouraged a w ide variety of injector configurations, ranging from simple air-assist nozz les to the more sophisticated designs of today, in which part of the atomiz ing air is carried by the nozzle itself while the remainder flows through s wirlers mounted on the combustion liner. Attention is focused on the relati ve merits of the various nozzle types, both pressure and airblast, in regar d to their ability to satisfy stringent performance requirements while surv iving formally thousands of hours in the increasingly hostile environment c reated by the continuing trend toward engines of higher pressure ratio, Ref erence is made to some new developments in atomizer design and manufacture and to the ongoing rob of the fuel injector irt finding solutions to the pr oblems posed by ultralow-emissions combustors, many of which are required t o operate near the lean extinction limit on fully premixed fual-air mixture s.