Editing Combustor (section)

====Double annular combustor====
One variation on the standard annular combustor is the ''double annular combustor'' (DAC). Like an annular combustor, the DAC is a continuous ring without separate combustion zones around the radius. The difference is that the combustor has two combustion zones around the ring; a pilot zone and a main zone. The pilot zone acts like that of a single annular combustor, and is the only zone operating at low power levels. At high power levels, the main zone is used as well, increasing air and mass flow through the combustor. GE's implementation of this type of combustor focuses on reducing {{NOx}} and {{CO2}} emissions.<ref>[http://www.cfm56.com/press/news/cfms+advanced+double+annular+combustor+technology/198?page_index=23 CFM'S Advanced Double Annular Combustor Technology] {{webarchive|url=https://archive.today/20120728235534/http://www.cfm56.com/press/news/cfms+advanced+double+annular+combustor+technology/198?page_index=23 |date=2012-07-28}}. Press Release. 9 Jul 1998. Accessed 6 Jan 2010.</ref> [https://engineering.purdue.edu/~propulsi/propulsion/images/jets/basics/combust.jpg A good diagram of a DAC is available from Purdue]. Extending the same principles as the double annular combustor, triple annular and "multiple annular" combustors have been proposed and even patented.<ref>Ekstedt, Edward E., et al (1994). {{US patent|5323604}} Triple annular combustor for gas turbine engine].</ref><ref>Schilling, Jan C., et al (1997). {{US patent|5630319}} Dome assembly for a multiple annular combustor].</ref>