Calculation on infrared characteristics of rocket motor nozzle by using enclosed cavity-radiative heat flux method

In order to calculate infrared characteristics of rocket motor nozzle, the enclosed cavity-radiative heat flux method was developed. Furthermore spectral transmission and absorption factors together with the equations relating to the rediative heat flux and gas temperature were deduced. For verification, rediative heat transfer of one axisymmetric cylindrical enclosed cavity filled up with homogeneous radiative medium was calculated. The calculation results agree well with those in reference. Moreover infrared characteristics of a rocket motor nozzl was calculated, and effective and net radiative heat flux of the nozzle in mid-wave infrared band 2-6 μm, long-wave infrared band 8-14 am and full wave band were analyzed. The results show that spectral radiation from the inlet and outlet of the nozzle present apparent discontinuity, and the effective radiation distribution along axial direction was dependant on wall temperature. The effective rediation is very strong on the flat and convergent section of the nozzle, but weak on the divergent section. The rediative heat flux of the nozzle with mid-wave infrared band 2-6 μm is 60 percent of that in full wave band.