Combustion Tests of a Staged Supersonic Combustor with a Strut

TLDR

The study introduces a staged supersonic combustor with a strut to avoid combustor‑inlet interaction and raise pressure in the divergent section. Experimental tests were performed in a direct‑connect wind tunnel with a Mach 2.5, 1500 K air stream, isolating the pressure rise from second‑stage combustion from that of the first stage. Using an equivalence ratio above unity—twice the allowable flow rate for first‑stage injection alone—fuel could be injected without interaction, yielding a 100 % thrust increase, while upstream second‑stage injection caused interaction and downstream injection reduced thrust due to low combustion efficiency. The paper defines symbols such as A for cross‑sectional area, F for thrust increment, and P for pressure.

Abstract

To avoid combustor ‐inlet interaction,a staged supersoniccombustorwitha strutforthee rst-stageinjection and second-stage wall injectors at its divergent section was introduced to increase the pressure in the divergent section under the limitation of the peak pressure at its minimum cross-sectional area section. The combustor was tested experimentally in a direct-connect wind-tunnel facility with a combustion heater that supplied Mach 2.5 aire ow witha total temperatureof1500 K.With thestaged injections,thepressurerisedueto thesecond-stagecombustion was isolated from that due to the e rst-stage combustion. Fuel with an equivalence ratio more than unity, twice that of the allowable e ow rate with the e rst-stage injection alone, could be injected without the interaction, and the maximum thrust increment was augmented by 100%. The effects of thesecond-stageinjector placements were also examined, and it was found that the second-stage injection farther upstream resulted in the interaction, but that the injection further downstream resulted in low thrust due to low combustion efe ciency. Nomenclature A = cross-sectional area of e ow pass dF = thrust increment dIsp = specie c impulse based on thrust increment F = thrust P = pressure P.X/ = measured wall pressure at X, mm T = temperature X = streamwise location from step Y = spanwise location from duct center Z = lateral location from duct center ° = specie c heat ratio = Crocco factor (see Ref. 10) A = equivalence ratio Subscripts i = combustor inlet o = combustor outlet 0 = stagnant condition 1 = e rst stage 2 = second stage