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
In order to obtain the Mueller matrix of metal target, a model for measuring the Mueller matrix of metal surface is proposed in this paper. The model consists of light source, polarizing system, detecting system and detector. The Mueller matrix of any reflection direction can be measured in the plane composed of incident direction and target normal. The polarization modulation of light is realized by double wave plate rotation method. The Mueller matrix of metal target is inversed by discrete Fourier transform. In this paper, copper and aluminum are measured. In order to reduce the influence of error on the measurement results, this paper adopts the least square method to process the data. By comparing the experimental results with the model calculation, the results show that this method is an effective method to measure the Mueller matrix of metal targets. At the end of the paper, the advantages and disadvantages of the experiment and suggestions for improvement are given.
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.
The ultraviolet radiation generated by NO transition in the shock layer of hypersonic vehicle provides an important basis for target detection and recognition. In this paper, direct simulation Monte Carlo (DSMC) method is used to simulate the high temperature flow field of the Apollo aircraft. Based on the temperature, pressure, and mass fraction, SPECAIR software is used to calculate the NO(γ) spectral absorption coefficient, and combined with the line of sight (LOS) method, the ultraviolet radiation produced by the NO(γ) transition along the stagnation line at different heights is calculated. Based on the wall heat flux, the wall energy conservation equation is used to calculate the wall temperature, combined with the Planck's law to calculate the wall radiation, and the influence of the wall catalytic effect on the ultraviolet radiation is studied. The results show that with the increase of the height, the gas pressure and temperature decrease obviously, and the ultraviolet radiation from NO(γ) transition decreases. The wall heat flux calculated by the wall catalytic model is very different. The choice of the wall catalytic model is particularly important when studying the influence of the wall radiation on the ultraviolet radiation.
This article reports on the ultraviolet spectral parameters of NO molecules along the stagnation point line of the shock layer of the RAM-CII hypersonic vehicle. CFD (Computational Fluid Dynamics) Commercial Software “FASTRAN” based on Navier-Stokes (NS) Reynolds average equation is used to simulate the flow field of RAM-CII aircraft. Use ICEM software to model and mesh the aircraft flow field. The shock layer is evenly layered along the stagnation line. The NO absorption coefficient of each layer is calculated using the line-by-line method. The corresponding blackbody radiation source function is combined with the absorption coefficient to calculate the spectral emission coefficient. Discuss the impact of the length from the stagnation point, temperature and pressure on the spectral parameters. The results showed that the overall value of the absorption coefficient and emission coefficient along the stagnation point increases first and then decreases. It is analyzed that the main factor affecting the change of the shock layer absorption coefficient in the high temperature range of the shock layer is the pressure change.
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