A Comparison of the Characteristics of Planar and Axisymmetric Bluff-Body Combustors Operated under Stratified Inlet Mixture Conditions

Table 1

Operating conditions and parameters.

Case	𝛿 (%)	𝑈Fuel	𝑇max (K)	𝐿𝑓/𝐷𝑏	𝐿𝑅/𝐷𝑏	ΦGlobal	Ka
Disk
Lean	50	1.43	1860	5.6	1.43	0.147	6
Ultralean	18	1.12	1732	5.2	1.36	0.115	18.5
Near LBO	6	1	1508	4.4	1.28	0.102	47
Square
Lean	94	1.24	2050	8.5	5.5	0.031	15
Ultralean	65	1.05	1850	3.5	3.5	0.025	35
Near LBO	14	0.73	1600	1.4	1.45	0.018	72

(1) 𝛿 is percent deviation from LBO, 𝛿=(𝑚_Fuel−𝑚_Fuel,LBO)/𝑚_fuel,LBO (%), (𝑚_fuel,LBO, fuel flow at lean blowoff). 𝑈_FBO=0.95 m/s for disk and 0.64 m/s for square.
(2) 𝑇_max: maximum measured wake temperature.
(3) 𝐿_𝑓: visible flame length; 𝐿_𝑅: measured recirculation length.
(4) Central air supply velocity for disk, 𝑈_𝑐=4.87 m/s and Re_Db = 7980 for all cases, coflow velocities in annular swirl stream at 𝑆=1.0, 𝑈_𝑠=𝑊_𝑠=10.5 m/s, surrounding shielding stream velocity, 𝑈_𝑒=10 m/s. Approach airflow for square, 𝑈_∞=6.7 m/s and Re_𝐻=5800 for all cases.
(5) Φ_Global, global equivalence ratio, based on mass flows of injected fuel and, (a) air supply in the central pipe for the disk, or (b) approach airflow over the tunnel height for the square.
(6) 𝑇_max location for the disk was at (𝑥/𝐷_𝑏,𝑟/𝐷_𝑏) = (0.4, 0.45), while for the square this was at (𝑥/ℎ,𝑦/ℎ) = (0.7 to 1.0, 0.9).