A Space: Science & Technology Study Advances Numerical Research for Optimizing Micronozzle Performance

BEIJING, June 15, 2023 /PRNewswire/ -- Micropropulsion systems based on the microelectromechanical system (MEMS) technology have tremendous potential for micro/nanosatellites to conduct satellite-like motion. The capability to fabricate functional microscale micropropulsion components such as thruster and propellant subsystems in a single unit makes this MEMS method ideal for the development of small satellites. Micronozzles are essential functional components of the micropropulsion system that can be fabricated in microscale with MEMS fabrication techniques. They feature a micron-scale geometry, a 2D Laval configuration, a rectangular cross section, and a highly thermal conductive silicon wall due to MEMS fabrication. However, viscous loss in the flow field and heat transfer to the nozzle wall can strongly influence nozzle performance, namely, thrust force and specific impulse.

Now, a team of researchers led by Professor Xiaoqian Chen and Professor Wen Yao from the Defense Innovation Institute, Chinese Academy of Military Science, China, report numerical research on MEMS micronozzles through multiphysics coupling simulation along with design optimization based on simulation results. The study was published in Space: Science & Technology on 31 May 2023. 

To accurately understand the flow field inside the micronozzle and how the highly thermal conductive silicon wall interacts with gas flow, the researchers employed a numerical simulation that couples fluid dynamics field and solid heat transfer field. The team further investigated the influence of different structural parameters on micronozzle performance that set the stage for design optimization. The researchers chose the optimum parameter set through constrained optimization by linear approximation (CObyLA) and compared the performance of the bell-shaped design with the linear expander design under different throat Reynolds numbers.

Contrary to their expectation, the researchers discovered that the optimum linear expander design outperforms the bell-shaped one on both thrust and specific impulse. The team attributed this novel finding to the turn-back geometry, that causes compression waves pointing to the central symmetrical plane. "The accumulation of the low-velocity boundary layer near the central symmetrical plane leads to a 2% to 3% larger portion of low-velocity flow compared with the linear expander micronozzle. Thus, the linear expander is believed to be the appropriate design for the MEMS micronozzle," explains Prof. Chen.

Going ahead, the researchers plan to validate these novel findings on performance comparison between the linear expander micronozzle and the bell-shaped micronozzle. The team is on track to supplement the numerical simulations with experimental measurements for optimized, effective design of micronozzles.

Reference

Title of original paper:
Multiphysics Numerical Simulation and Geometric Optimization of a Micronozzle for the MEMS Thruster

Journal:
Space: Science & Technology  

DOI: https://doi.org/10.34133/space.0032

Media contact:
Ruoxi Tian
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SOURCE Space: Science & Technology