**6. Conclusions**

A 1D gas flow analysis was performed using the MOC for a single cylinder diesel engine, and the results of comparing the average mass flow rate and the intake and exhaust pipe pressure with the results of the experiment are summarized as follows:


As a result of the experiment and verification, there was a limit to increasing the accuracy, even when applying the discharge coe fficient obtained using the average mass flow rate. This error is thought to be due to the disadvantage of 1D gas flow analysis, which cannot calculate complex geometries. In the future, it is expected that this problem can be solved by analyzing the complex geometries in 3D and using 1D–3D coupling gas flow analysis.

**Author Contributions:** Conceptualization and methodology, K.-J.K.; experimental system configuration and data curation, K.-H.K.; software, K.-J.K.; writing and validation, K.-J.K. and K.-H.K.; supervision, K.-J.K. and K.-H.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to acknowledgment the Turbo Engine Lab, Department of Mechanical System Engineering, Pukyong National University for purchasing and supporting the use of the experimental apparatus.

**Conflicts of Interest:** The authors declare no conflict of interest.
