Calculating the infrared characteristics of the rocket nozzle with the narrow-band zone model

Calculation of the infrared characteristics of a rocket nozzle is very important for the study of infrared initiating technology. The Narrow-Band Zone model is developed for that purpose. The spectral transmission and absorption factors are introduced, and the equations between radiative heat flux and the temperature of wall surfaces and gas are developed. The radiative heat transfer in one axisymmetric cylindrical enclosure filled with homogeneous radiative participating medium is computed with the Narrow-Band Zone model and compared with those in the reference documents. The comparison shows good agreement. The radiative heat transfer to the nozzle of one rocket engine is also calculated with the Narrow-Band Zone model, and the outgoing radiative energy flux and energy rate integrated in a mid-wave infrared band 2-6μm, a long-wave infrared band 8-14μm and the full wave band are analyzed. The following conclusions can be derived: the spectral radiation from the inlet and outlet of the nozzle show apparent spectral discontinuity, which appears greater in the 2.7-2.95μm than in the neighboring wave band. The spectral outgoing radiative energy flux of nozzle wall is similar to that of gray body, which decreases with wavelength in 2-4μm. The outgoing radiative energy flux on the nozzle wall is greater in the cylindrical and contracting section of nozzle, but smaller in the divergent section, which is determined by the temperature. The nozzle of the rocket engine radiates most energy in the mid-wave infrared band 2-6μm, long-wave infrared band 8-14μm and full wave band are analyzed.