## 5 Conclusions  
In this study, both the boundary layer suction method and supersonic diffuser ejection were employed for experimental research aimed at exploring the low Re number flow behavior, as well as enhancing an optical cavity of a chemical laser system. Among all the experimental parameters, it was found that the mainstream ejection mode was the most effective boundary layer suction method, allowing for significant control of energy power and pressure within the optical cavity. Regarding the supersonic diffuser, optimal parameters were determined experimentally to enhance the chemical reaction platform's capacity to withstand high back pressure and airflow disturbances. Overall, this study focused on investigating low Reynolds flow with chemical reactions in the SCRP. The findings presented in this study have the potential for applications in improving the energy output of chemical laser systems.  
The variations in pressure in the optical cavity with a solid plate prove that the boundary layer control in the optical cavity is necessary for the efficient work of the SCRP. The comparison between the three cavity structures and test pieces shows that the mainstream ejection slot can significantly regulate the energy power by controlling the pumping volume. The other two methods, the slotted and orifice plate, were effective in controlling the growth of the boundary layer but could not apparently change the power on the cavity, especially when the pumping volume exceeded a certain threshold.  
As for the pressure recovery performance of the chemical laser system, an active gas booster supersonic diffuser with a low Re number and internal reaction exothermic flow was studied. The increase in the initial back pressure of the vacuum tank brings difficulty for the diffuser to maintain the pressure in the optical cavity, and an active booster-type supersonic diffuser was installed downstream of the optical cavity to create a low-pressure and stable environment in the optical cavity. An experimental comparison between the three pieces was also investigated, and the energy increase in SCRP docking with the 2# supersonic diffuser is biggest at 32%. All in all, both the boundary layer control method as well as the novel design of the supersonic diffuser could be good choices for the system design of chemical laser systems, which could give improvements in working conditions and energy release and give good support for the further analysis of the aero-optical effect.  
**Author Contributions:** Conceptualization, D.X.; methodology, X.G.; formal analysis, Y.G.; investigation, Z.R. and J.C.; project administration, D.X.; funding acquisition, D.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Equipment Comprehensive Research Project, grant number JK20211A010089.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
**Conflicts of Interest:** The authors declare no conflict of interest. The sponsors had no role in the design, execution, interpretation, or writing of the study.