# Study on Thermal Radiation Characteristics and the Multi-Point Source Model of Hydrogen Jet Fire
## 5 Conclusions  
To address the current limitations in accurately predicting the thermal radiation from hydrogen jet fires under complex conditions, this study utilized CFD simulations to optimize the discrete weight coefficients in the multi-point source radiation model. This optimization enhanced the accuracy of the model for predicting the thermal radiation in hydrogen jet fires. Additionally, experimental investigations were conducted to examine the variations in the thermal radiation and flame dimensions under different leakage pressures, orifice diameters, and radial distances. The experimental data were used to validate and compare the performance of the optimized thermal radiation prediction model. The main conclusions are as follows.  
1. The study of the hydrogen jet flame dimensions indicated that both the flame length and width increase with higher leakage pressures and diameters. The flame length prediction model based on the Froude number is particularly suitable for medium-high-pressure hydrogen jet fires. The flame shapes under different leakage pressures and diameters exhibited a certain degree of similarity, with the ratio coefficient of the flame length to width being 5.819.
2. The thermal radiation density significantly decreased with increasing radial distance and height. The thermal radiation at various spatial positions was influenced by flame oscillations and showed an approximately linear increase with a rising leakage pressure and diameter. Additionally, increased leakage pressures and diameters elevated the flame height corresponding to the maximum thermal radiation.
3. Optimizing the heat source weight coefficients based on the flame axis temperature distribution significantly reduced the prediction error of the multi-point source radiation model by 5.6%. In six comparative scenarios, the average prediction error of the optimized model was 13.9%, compared with 19.5% for the original model, demonstrating a higher predictive accuracy.  
Conceptualization, H.Z. and X.C.; methodology, H.Z. and X.Y.; software, J.W.; validation, X.C. and Y.Z.; formal analysis, X.Y.; investigation, X.C.; resources, F.W.; data curation, H.Z.; writing--original draft preparation, H.Z.; writing--review and editing, Q.L. and H.L.; supervision, Z.H.; project administration, F.W.; funding acquisition, Q.L. and Z.H. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Science and Technology Plan Program of Yulin (CXY-2021-119), the Natural Science Basic Research Program of Shaanxi Province (2020 JM-053), and the China Petroleum Pipeline Engineering Corporation.  
The data presented in this study are available upon request from the corresponding author (Q.L.).  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author [PERSON] was employed by the company China Petroleum Pipeline Engineering Corporation, who provided funding and technical support for the work. The funder had no role in the design of the study; in the collection, analysis, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.