Plume IR emission of turboshaft engines is investigated experimentally in 1-14.5 micron band by a Barnes Spectroradiometer with CVF and two IR scanners (AGA 782 Thermovision SW and LW) in order to compare it to a computer model and therefore to identify the most important parameters. This experimental set-up is completely adequate to field measurements of infrared signature from a turboshaft engine. It is completely interfaced to a HP 9836 computer to drive the instruments and to reduce on-line both spectral and spatial IR data. The spectral results are available as a function of wavelength (also in polar diagrams) and are connected to the emission wavelengths of the plume components. Spatial results are available in pictures (128x128 elements), displayed on a H.R. Colour Monitor. A sophisticated computer program allows to increase the detail of information. Spatial results are important to understand and to investigate phenomena like turbolence, non assial symmetric emission, etc. In order to estimate the real infrared signature of a turboshaft engine the transmittance of the atmo sphere and the background emission have been measured during the field measurements. Also, absolute calibrations of spectroradiometer and scanners are conducted in our lab. Estimate of errors in terms of precision and accuracy of the measure are as well considered. Plume spatial infrared signatures of engine, for real installation on a rotorcraft, have been measured in order to adequate our computer model. This study is connected to a R&D program in the field of IR signature suppression for rotorcraft application.
"Plume Infrared Signature Measurements And Comparison With A Theoretical Model", Proc. SPIE 0685, Infrared Technology XII, (10 December 1986); doi: 10.1117/12.936498; https://doi.org/10.1117/12.936498