Uncertainty Propagation in Integrated Airframe Propulsion System Analysis for Hypersonic Vehicles
Air{breathing hypersonic vehicles are based on airframe{integrated SCRAMjet engine. The elongated forebody which serves as the inlet of the engine is subject to harsh aerothermodynamic loading which causes it to deform. Unpredicted deformations may produce unstart, combustor chocking or structural failure due to increased loads. This study presents a framework allowing one to assess the impact of aerothermoelastic deformations on the engine performance prediction. Aerothermoelastic deformations are calculated for trajectories and angle of attack and transferred to a SCRAMjet engine analysis. Uncertainty associated with deformation prediction is propagated to the engine performance analysis. The importance of modeling the aerodynamic heating and aerothermoelastic deformations at the cowl of the inlet is noted. The cowl deformation is the main contributor to uncertainty and sensitivity of the propulsion system analysis.
Effects of the aerothermoelastic deformation on the performance of the three-dimensional hypersonic inlet
Abstract The hypersonic inlet is more prone to deform when simultaneously subjected to aerodynamic load and harsh aerothermodynamic load. Moreover, the flow field of the hypersonic inlet is sensitive to configuration. Therefore, it is necessary to investigate the effects of the aerothermoelastic deformation on the flow structure and the performance of the hypersonic inlet. This study develops a loose coupling static aerothermoelastic analysis framework based on the CFD/CSD coupling method, and the one-way and the two-way aerothermal-aeroelastic coupling are both used in the analysis. Furthermore, the effects of the aerothermoelastic deformation on the flow structure and the performance of a three-dimensional hypersonic inlet are studied in detail. The reliabilities of the CFD method and the CFD/CSD coupling method are verified by the validation cases of DLR hypersonic inlet experimental model and the HIRENASD experimental model. The results obtained by the coupling methods are similar. However, the aerothermoelastic deformation obtained through the two-way coupling method is relatively larger, and the effects of the deformation on the inlet performance are more obvious. The maximum of the aerothermoelastic deformation exists at the leading edge of the inlet lip. The deformation changes the shock wave structure near the lip, strengthens the shock wave intensity inside the inlet, increases the length of the separated region and the temperature of the external wall, and changes the flow field of the exit. The aerothermoelastic deformation will lead to the increasing of the mass flow coefficient and the pressure rise ratio; however, it will decrease the total pressure recovery coefficient.
Thermally Induced Dynamics of Satellite Solar Panels
Thermally induced structural motions are known to affect the attitude dynamics of low Earth orbiting satellites during eclipse transitions. Motions of e exible appendages such as solar panels lead to rigid body rotations of the entire satellite because the total angular momentum of the system is conserved. These potentially large attitude disturbances may violate pointing accuracy and jitter requirements. One type of thermally induced dynamics exhibited by solar panels is thermal snap. The Upper Atmosphere Research Satellite is a prominent example of a satellite that experiences thermal snap disturbances during eclipse transitions. This paper describes recent studies of thermally induced dynamicsof solarpanels, including an analysisofsatelliteattitudedynamics resulting from thermally induced structural motions and a laboratory investigation of the thermal-structural performance of a satellite solar panel. Analytical and experimental results demonstrate thermal bending deformations with acceleration transients that have characteristic thermal snap disturbance histories in response to rapid changes in heating. The studies show that solar panel thermal snap disturbances are caused by through-the-thickness temperature differences that vary at a nonconstant rate. Finite element analysis correctly predicts the thermal snap phenomenon observed in the solar panel experiments.