Measurements of a micro gas turbine plume and data reduction for the purpose of infrared signature modeling

An important issue concerning numerical simulation of gas turbine-propelled aircraft in infrared scenarios (usually in military applications) is the radiometric emission properties of the aircraft exhaust plume. In this paper, a detailed description of the experimental setup and the measurement results of the infrared signature properties of a micro turbine engine plume at ground level (with an altitude of approximately 1500 m above sea level) are presented. The main instruments used were a midwave (3-6 μm) infrared camera and a spectroradiometer (0.8-5.5 μm). The wideband emission properties were investigated with the camera as a function of the aspect angle between the camera´s field of view and the plume´s longitudinal axis, while maintaining a fixed engine rotational speed, as well as a function of the engine rotational speed for a fixed aspect angle of 90°. The spectral emission was investigated with the spectroradiometer as a function of three regions along the plume for a small instrument field of view and fixed engine setting. These measurements comprise the radiometric characterization of a micro gas turbine exhaust plume that, after data reduction, allows numerical modeling of this type of plume in a computer simulation. Such measurements, or the model based on it, are useful in conceptual studies regarding the infrared signatures of a turbine gas plume. It is in principle also possible to construct an infrared radiometric model of a larger-scale turbine engine´s plume based on these characteristics.