Spray Characteristics Measured in a New FLOX® Based Low Emission Combustor for Liquid Fuels Using Laser and Optical Diagnostics

Abstract

A liquid fuel combustor based on the FLOX® burner concept has been developed for application in a Micro Gas Turbine (MGT) Range Extender (REX) for next generation cars. The characterization of this combustor was performed at the High Pressure Optical Test rig (HIPOT) at DLR Stuttgart. The operability limits of the burner were mapped out for full load conditions at 3.5 bars by varying global lambda (λG) from 1.25–2.00 and bulk jet velocity (vBulk) from 80–140 m/s. Exhaust gas measurements show NOx and CO levels below 5 and 10 ppm respectively (corrected for reference 15% O2) at λG = 1.89. Optical and laser diagnostic measurement techniques have been employed to characterize the spray flames. The flames at stable burner operation points (BOPs) show a predominantly jet like flame shape irrespective of λG and vBulk. Droplets in the size range 2–40 μm have been measured close to the nozzle exit plane. Velocities conditioned on the droplet size show large droplets d > 15 μm transitioning from negative slip velocity at the exit plane to positive slip velocity at downstream location. The positive slip velocities and slow evaporation of large droplets lead to droplets travelling further into the combustion chamber and hence resulting in long flames. A comprehensive data set for the spray characteristic of the new liquid FLOX® burner is made available.

Experimental and numerical investigation of spray characteristics in a new FLOX®based combustor for liquid fuels for Micro Gas Turbine Range Extender (MGT-REX)

“…The exhaust gas results presented in Ref. 18 showed good promise where measured NO x and CO levels are below 5 and 10 ppm, respectively (corrected for reference 15% O 2 ) at a global lambda ( G ) of 1.89. However, the length of the flames is long, which would create huge challenges with regards to the size of the combustor.…”

“…The high pressure optical test rig (HIPOT) at the DLR is one such facility where the 8 nozzle liquid FLOX ® burner is being extensively tested. The operability limits of the liquid FLOX ® burner at actual operating parameters (P = 3.5 bars and T = 300 °C) of a projected MGT-REX have been mapped by Gounder et al 18 . The exhaust gas results presented in Ref.…”

“…The first results of the spray characteristics of the liquid FLOX ® burner have been presented in Ref. 18 where the effects of varying jet velocity (v Jet ), G and thermal power (P th ) on the flame shape and droplet field were investigated. The measured spray length showed large penetration depth of the spray into the combustion chamber from the nozzle exit plane.…”

“…In the present work one of the burner operation point (BOP) from Ref. 18 is chosen, for which detailed droplet data obtained from Phase Doppler Interferometry (PDI) measurements are provided for validation of CFD simulation.…”

Characterization of an Aircraft Auxiliary Power Unit Test Rig for Cycle Optimization Studies

“…This magnitude is below the limit value of 73 ppm defined for the stationary CHP units powered with liquid fuel. However, these magnitudes are still high compared to state-of-the-art [21] and novel liquid fuel combustors [22]. These combustion systems exhibit NO x emissions down to single digit levels.…”