Tianwen-1 Mars entry vehicle trajectory and atmosphere reconstruction preliminary analysis

The Tianwen-1 Mars entry vehicle successfully landed on the surface of Mars in southern Utopia Planitia on May 15,2021,at 7:18(UTC+8).To acquire valuable Martian flight data,a scientific instrumentation package consisting of a flush air data system and a multilayer temperature-sensing system was installed aboard the entry vehicle.A combined approach was applied in the entry,descent,and landing trajectory reconstruction using all available data obtained by the inertial measurement unit and the flush air data system.An aerodynamic database covering the entire flight regime was generated using computational fluid dynamics methods to assist in the reconstruction process.A preliminary analysis of the trajectory reconstruction result,along with the atmosphere reconstruction and aerodynamic performance,was conducted.The results show that the trajectory agrees closely with the nominal trajectory and the wind-relative attitude.Suspected wind occurred at the end of the trajectory.

Effects of pressure oscillation on aerodynamic characteristics in an aero-engine combustor

The effects of pressure oscillation on aerodynamic characteristics in an aero-engine combustor are investigated. A combustor test rig is designed to simulate the pressure drop characteristics of a practical annular combustor. The pressure drop characteristics are firstly measured under atmosphere condition with non-reacting flow(or cold flow), and the air mass flow proportion of each component(dome/liner) are obtained;these properties are base lines for comparison with combustion state. The combustion tests are then carried out under conditions of inlet temperature 340–450 K, fuel air ratio 0.010–0.028. The stability map and the oscillation frequencies are obtained in the tests, the results show that pressure oscillation amplitude increases with the increase of fuel air ratio. Phase trajectory reconstruction is applied to classify the pressure oscillation motion;there are three motions captured in the tests including: ‘‘disk", ‘‘ring" and ‘‘cluster". The pressure drops across the dome under strong pressure oscillation are distinctly divergent from the cold flow, and the changes of pressure drops are mainly affected by pressure oscillation amplitude, but is less influenced by pressure oscillation motion nor oscillation frequencies. Based on the mass flow conservation, the reduction of effective flow area of combustor under strong pressure oscillation is demonstrated. Liner wall temperatures are analyzed through Multiple Linear Regression(MLR)method to estimate the reduction of the air mass flow proportion of the liner cooling under strong pressure oscillation. Finally, the air mass flow proportions of each component under strong pressure oscillation are estimated, the results show that the pressure oscillation motion also has influence on air mass flow proportion.

An enhanced dead reckoning algorithm with hybrid extrapolation models(AisaSim 2016)

The traditional Dead Reckoning algorithm predicts the future motion state based on a determined polynomial predictor,and the forecasting performance would vary with different types of motion entities.This paper proposes an enhanced dead reckoning algorithm based on hybrid extrapolation models,which can be used to reduce the communication in a distributed interactive simulation.The proposed algorithm perform extrapolation using a number of candidate predictors.Its idea is based on the assumption that a complex trajectory can be decomposed into several simple trajectories.The experimental evaluations show that the enhanced Dead Reckoning algorithm provides better performance in correction data reduction and accurate estimation.