## 5 Conclusions  
This work presented a mathematical model describing the behavior of the piston across various motion stages of the RC-DTH air hammer. Additionally, it outlined the design of the piston structure for the Type B internal flow RC-DTH air hammer. Utilizing CFD dynamic mesh technology, a numerical model for simulating the piston impact of the RC-DTH hammer was developed to assess the impact performance of the piston. An impact performance testing platform for the RC-DTH air hammer was constructed to validate the accuracy of the numerical simulation outcomes. The following conclusions were drawn from this study:  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test** & **Strain Peak/\(\mu\epsilon\)** & **Impact Work/J** & **Frequency/Hz** \\ \hline
1 & 532 & 298.4652 & 17 \\
2 & 507 & 285.7702 & 19 \\
3 & 516 & 290.3404 & 18 \\
4 & 522 & 293.3872 & 17 \\
5 & 632 & 349.2452 & 19 \\
6 & 539 & 302.0198 & 18 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Piston impact performance records.  
Figure 10: Drill system for testing the impact performance of the RC-DTH air hammers. (**a**) Schematic diagram; (**b**) field test.  
1. Enhancing the intake stroke of the upper chamber (\(F_{1}\)) and the outlet stroke of the lower chamber (\(R_{2}\)) of the RC-DTH air hammer piston effectively improves the piston's impact performance. Conversely, increasing the inlet stroke of the lower chamber (\(R_{1}\)) and the outlet stroke of the upper chamber (\(F_{2}\)) tends to diminish the piston's impact performance.
2. The mass of the piston in the RC-DTH air hammer influences its striking frequency, while having a minimal impact on the energy of each blow. As the mass of the piston increases, the impact power diminishes.
3. After optimizing the piston valve stroke parameters of the Type B RC-DTH air hammer, its impact performance improved by 20.32%. Compared to the GQ89 hammer, the Type B hammer exhibits an 84% increase in impact energy and a 74% increase in impact power. Additionally, the impact energy test conducted on the RC-DTH hammer confirms the validity of the numerical simulation results derived from the impact simulation model.  
Z.L.: Writing--original draft, Writing--review and editing, Software, Investigation. Y.L.: Writing--original draft, Writing--review and editing, Validation, Software, Investigation, Methodology. W.H.: Formal analysis, Software, Methodology. R.T.: Resources, Project administration, Supervision. J.H.: Resources, Conceptualization, Validation. Y.S.: Project administration, Supervision, Resources. H.C.: Formal analysis, Resources, Validation. Q.H.: Resources, Supervision, Validation. All authors have read and agreed to the published version of the manuscript.  
This work is financially supported by the Key Research and Development Program of the Ningxia Hui Autonomous Region (Grant No. 2022 BEG02015), which is gratefully acknowledged. The authors also thank the editor and anonymous reviewers for their valuable advice.  
Not applicable.  
Data Availability Statement: Data will be made available on request.  
Author [PERSON] and [PERSON] were employed by the company Ningxia Institute of Mineral Geological Survey, Ningxia, China. Author [PERSON] was employed by the company China national gold engineering, Beijing, China. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.