Future Trends in Commercial Aviation Engines’ Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 153

Fig. 43 Second generation SV-LDI for two con gurations, left flat dome and right 5-point recess
dome; reproduced from Tacina et al. ( 2014 )

same m 1 set of mixers con guration is also used for the recessed LDI-2. In order to

offset supposedly higher NO x emission from the recessed con guration, its pilot

injector and swirler arrangement was different from that of the fl at dome. It uses

Woodward ' s expertise in pure airblast nozzle with inner swirler air (identi ed as

IAS in Table 6 ) vanes of 57 ° clockwise (CW), and outer air swirler (OAS) 57 °

CCW vanes with the attendant low swirl air atomizing pilot; and the flame front

being barely visible. In order to further reduce NO x of the recessed LDI-2, the eight
main mixers (m 2 and m 3 ) were similarly designed as pure airblast nozzles but with
45

fl

° CW/45 ° CCW arrangement in contrast to the fl flat dome with 45 ° CW/45 ° CW

swirlers. In other words, the flat dome uses higher swirl number m 2 and m 3 mixers

than the recessed dome, again to offset higher NO x of the latter. Extensive testing
was done in the NASA facility and the

fl

first paper on the results are summarized by
Tacina et al. ( 2014 ), with several more to follow to deal with many aspects of these
designs. Effective areas of the

flat and recessed modules are 1,338 and 1,326 mm 2 ,
respectively, with the corresponding combustor area expansion ratios of 9.77 and
9.85 compared to 6.1 for the 45

fl

°

LDI-1.
Tacina et al. ( 2014 ) have provided extensive database and correlation effort on the
both LDI-2 con

gurations. Here we share only one aspect of the design, namely
back-to-back comparison on EINO x /P 0.5 versus adiabatic fl ame temperature T Tflame

between the recessed dome (at T 3 = 1,024 ° F, P 3 = 253 psi, their standard deviations

˃ F, and

7 psi. The results are summarized in Fig. 44 ; here P 3 is in atmosphere and T Tflame is in
degrees Kelvin. The left part of the

=14 ° F and 7 psi), and the fl at dome at T 3 = 1,014 ° F, P 3 = 255 psi, ˃ =14 °

figure shows the entire datasets covering T Tflame
range between 1,500 and 2,100 K for the recessed dome in addition to the at dome

for T Tflame up to 1,900 K; the right part is the zoomed-in data for the both con

fl

gu-

rations for T Tflame up to only 1,900 K. Combustion ef ciency of all the data presented