Planar laser - induced fluorescence ( PLIF ) is used to visualize the flame structure via OH , NO , and fuel imaging in kerosene- burning gas turbine combustor flame tubes . When compared to simple gaseous hydrocarbon flames and hydrogen flames , flame tube testing complexities include spectral interferences from large fuel fragments , unknown turbulence interactions , high pressure operation , and the concomitant need for windows and remote operation . Complications of these and other factors as they apply to image analysis are considered . Because both OH and gas turbine engine fuels ( commercial and military ) can be excited and detected using OH transition lines , a narrowband and a broadband detection scheme are compared and the benefits and drawbacks of each method are examined .