Future Trends in Commercial Aviation Engines’ Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 161

Radial
swirler

D=4”

Moderate swirl

Configuration 1/2

Weak Swirl

Configuration 3

Fuel nozzle with 3 swirlers ranging from weak
to moderate swirl strength; single or twin
rows of fuel jets in swirling cross streams.

Axial
swirler

Fig. 50 LDI-based combustor cross-section from Mongia ( 2011b )

swirlers) were tried; radial in ow swirler closer to exit plane of the premixing tube

gave the best results. Typical air

fl

ow distribution at the simulated max-max power
(T 3 = 1158 K and P 3 = 490 kPa) is given in Fig. 51 along with its CO and NO x EI
characteristics in Fig. 52 . Two interesting observations need to be made here. First,
its NO x /P 0.5 value ranges between 0.6 and 1.5 EI/atm 0.5 which is very competitive
with the lowest values discussed earlier concerning Figs. 37 and 44 . Second, the
mixer survived during extensive rig testing at temperatures exceeding 1328 K with
the corresponding ignition delay times less than 0.2 ms even when the mixer may
be classi

fl

ed as a premixing and not LDI which we do not agree for the reasons
outlined in the following paragraph.
First, we used liquid fuel injection at the throat of two concentric venturis
involving both radially inward and outward directions normal to cross swirling
fl

flows, JIC. Second, two separate diverging concentric passages followed axially
downstream of JIC. This was followed by continuous fuel/air mixing in a single
diverging passage until the radial swirler. The swirl strength of the three concentric
swirlers was optimized, which starting from center increased from very weak
( ) for the outer-mounted

injector swirler, as shown in Figs. 49 and 50 . The point of disagreement could be

≤ 15 ° ), to weak ( ≤ 30 ° ), and moderately strong ( ≤ 45 °

Fig. 51 Air fl flow distribution of the mixer configuration tested at the simulated max-max

operating point; from Mongia ( 2011b )