| During a takeoff from outside earth surface in a vacuum-like environment, the heated and rapid engine plume impacts and induces vibrations to the launching pad. The mechanical and heat impacts from engine plume will disturb the launch pad’s load balance, and thus affecting the accuracy and position of the lander’s takeoff trajectory, which could lead to the failure of takeoff and of the mission itself. To alleviate the adverse effects of the engine plume, an exhaust plume conduction device needs to be installed on the launching pad. Based on the variations in the conduction device’s design, it will divert the plume differently. Due to the proximity of the engine nozzle to the launching pad, the fast-expanding nature of plume in vacuum, and the shock wave generated from plume colliding with the launching platform, the nozzle opening might be blocked.Blockage of the nozzle opening will lead to elevated pressure in the nozzle and reduced Mach number, which in turn, reduces the thrust power and negatively impact the launch stability. This paper adopts CFD/DSMC coupling approach and numerically simulates the changes in thermal and mechanical responses with different conduction devices. Our study aims to create an ideal plume conduction device in the limited space between launching platform and the lander to alleviate the negative impacts of plume. These findings provided valuable logistics on a lander’s launching safety. The main works include:1)Categorized engine plume into continuous and discontinuous plume zones. Established the continuous flow model based on N-S function’s CFD in the plume zone near nozzle exit. Based on the Kn value, we established the interface between continuous and dilute gas flow zone, and future defined the interface’s speed, density, and temperature. CFD/DSMC simulation model was created,and the logical grid size, molecular density and time step were established to obtain precise calculations.2)Systemically analyzed the flat, concave groove, and cone conduction surfaces’ vacuum plume charicteristic. Conducted simulation studies on the plume conduction models. Thoroughly examined various factors in the simulation model, such as the distance and rising angles between lander and launching platform during takeoff. The simulations and analysis were carried on the various conditions as well. Overall, the plume’s distribution patterns under various conduction models were obtained.3)In order to verify the accuracy of the data reported in this paper, the plum field distribution of the example in Dr. Boyd’s study was examined, and compared the results to our simulation andexperimental results, and the relative error less than 6%. Additionally, the simulation results were compared against the results reported in Norman’s study’s vacuum cabin experimental results and Roberts’ s study’s simulation results respectively. The same experimental conditions were adopted in this paper, and obtained Mach graph similar to the results reported. To generate quantitative results, the diameter of plume-induced shock wave was measured, and the relevant error below 4%between the simulation results and experimental results.4)Various conduction surfaces were tested. The plume distributions with flat and cone-shaped conduction surfaces under high ultrasound and low density wind tunnel environment were examined. Obtained plume’s dynamically characterized results and conduction results in vacuum,which validated the simulation model’s accuracy.5)After the examination of large amount of experimental results, it revealed that when the initial distance between lander and launching platform is 200 mm, the cone-shaped conduction is the best, followed by concave groove conduction, and flat conduction shows less promising results.When gap between lander and launching platform reaches 500 mm, the shockwave completely exists nozzle opening. When considering the distance and angle changes during elevation, the cone-shaped conduction will leads to least amount of disturbance force and torque. |
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