**4. Conclusions**

In this paper, experimental and theoretical research were carried out on the height of smoke layers from engine room fires under the condition of forced ventilation. The development of the cabin room fire and the process of smoke settlement under the conditions of different air supply volume and air supply inlet heights were studied by experiment method. The theoretical analysis was carried out to predict the height of the cabin fire smoke layer under different air supply conditions and verified the validity of the model.

The main conclusions are as follows:

(1) The fire experiment was carried out in the small-scale engine room. Experimental results show that the mass loss rate of the fire source increased approximately exponentially with the increase in the supply air volume. Combined with the experimental data and previous data, the empirical formulas of mass loss rate and air supply volume are given, and they are applied to the smoke layer height prediction model proposed in this study.

(2) The smoke layer height variation curve under different air supply conditions was given based on the minimum integral ratio method. Under the experimental conditions, the height of the smoke layer gradually increases with the increase in air supply volume and the height of the smoke layer gradually decreases with the increase in the height of the air supply inlet.

(3) A prediction model of smoke layer height under different forced ventilation conditions was constructed through theoretical analysis based on the conservation equations. Within the range of the experimental air supply volume and the height of the air inlet, the relative error between theoretical prediction results and experimental results was less than 11%, which could effectively predict the smoke layer height in the in-ship cabin fire. The research is of great significance to the research on the fire risk of the engine room, and provides a theoretical basis for the prediction of the fire risk of the engine room.

**Author Contributions:** Methodology, X.W.; software, W.Y.; validation, Y.Z.; formal analysis, X.W.; investigation, J.J.; resources, X.W.; data curation, Y.Z.; writing—original draft preparation, X.W.; writing—review and editing, X.C. and S.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The National Natural Science Foundation of China (Grant No.51704268) and Fundamental Research Funds for the Central Universities (No. WK2320000048).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** This work was supported by the National Natural Science Foundation of China (Grant No.51704268) and the Fundamental Research Funds for the Central Universities (No. WK2320000048).

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