The increasing significance of high-temperature gases in heat transfer, combustion, and rocket exhaust plume, restrictions motivate researchers to continuously seek more efficient and accurate models to explain the related physical phenomena. The traditional Curtis-Godson approximation (CGA) will lose accuracy in the presence of severely inhomogeneous participating combustion gases by ignoring the high sensitivity of the narrow-band halfwidth to gas temperature and pressure. In order to improve the accuracy of traditional CGA, this paper introduces a correction function to correct the narrow-band half-width along the line-of-sight direction of the combustion system, where the correction function is related to the thermodynamic state of the high-temperature gas. The infrared spectral transmissivities calculated by the line-by-line approach are used as the benchmark solution to evaluate the accuracy of our improved CGA. The results in this study can be used to efficiently calculate the radiative transfer of rocket exhaust plumes.
In order to study the anti-turbulence performance of the perfect vortex beam which carrying Orbital angular momentum(OAM), the average intensity distribution, beam spreading and scintillation characteristics of the perfect vortex beam propagating in atmospheric turbulence are simulated based on the multi-phase screen method by making use of the Von Karman spectrum. The impacts of beam parameters (OAM number, wavelength,) and atmospheric turbulence parameters (inner scale, outer scale) on the beam spreading and scintillation of perfect vortex beams are investigated. The results show that the beam parameters can be adjusted to reduce the scintillation and beam spreading effects caused by atmospheric turbulence. Perfect vortex beams with smaller OAM numbers and larger wavelengths have better resistance to turbulence. The smaller the outer scale and the larger the inner scale of the atmospheric turbulence, the better propagation performance of perfect vortex beam. The research of this paper provides an important reference for optimizing the optical communication performance of perfect vortex beams in atmospheric turbulence.
At high temperatures, typical species in the rocket exhaust plume produce spectral radiation signals in a specific spectrum due to high-temperature vibration-rotation transitions. This signal level strongly depend on the working condition of the rocket engine. In this paper, based on the statistic-narrow-band (SNB) model and the latest version of the HITEMP2010 line-by-line database, a database of spectral radiation calculation parameters for methane combustion products, H2O and CO2, is established. By comparing the experimental results and the line-by-line method, the correctness of the model verified. Based on this database, considering the atmospheric detection band of the typical rocket plume infrared radiation signals, the un-attenuated and attenuated by the long atmospheric path are predicted, (2.7 and 4.3μm band) spectral radiance of the high temperature mixed gases (H2O and CO2) at different altitude are predicted. The model prediction results compared with the experimental results, and good results obtained accurately
Alumina particles occur multiphase in aircraft plume. The superposition T-matrix method was applied to study how the monomer models of multiphase alumina affects the optical characteristics of alumina cluster. The concentric monomers (CM), uniform direction monomer (UDM) and random direction monomer (RDM). In addition, to simplify the computation, we applied Maxwell–Garnett equivalent approach to simulate equivalent homogenous monomer (EHM). According to the results, the optical characteristics of alumina clusters with CM, UDM and RDM are almost the same. The relative discrepancies of using EHM and using other three heterogeneous monomer models can not be ignored. Our research provides a suggestion for model simplification and selection. For the significant roles of alumina particles in plume radiation, our research is useful for application of detecting system.
This paper presents a stellar point source background radiation model based on IRAS catalog, which is used to simulate the stellar background radiation signals of observers at any time of observation and in the field of view at any longitude, latitude and altitude. First, the data of stellar equatorial longitude, equatorial latitude, magnitude, and radiation intensity recorded at the epoch time in IRAS catalog is used to correct the proper motion, precession and nutation, and the coordinate information of the star at the specified time in the coordinate system of equatorial celestial sphere will be obtained. Then, after a series of coordinate conversions, with the occlusion of the line of sight being taken into consideration, the coordinates of the star at the time of observation are converted into the apparent position relative to the observer in the specified scene. On this basis, the infrared irradiance of stars in the specified field of view is calculated based on the radiation intensity data recorded in the star table. The research results have some reference value for the detection and recognition of space objects.
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