## 5 Conclusions  
This paper investigated the global sensitivity and multi-objective optimization of the operational parameters of the air compressor in hydrogen energy vehicles based on experimental results. These findings hold significant value in guiding the efficient and stable operation of air compressors. The main conclusions are summarized as follows.  
1. The rotational speed exhibits the highest sensitivity to total energy consumption, while the pressure ratio showcases the most prominent sensitivity towards the isentropic efficiency and mass flow rate. Conversely, the impact of the intake temperature on energy consumption, efficiency, and flow rate is minimal.
2. The total power consumption increases with higher rotational speed and inlet temperature. Notably, with an increase in the pressure ratio, total power consumption initially rises before decreasing. Isentropic efficiency increases with higher values of rotational speed, pressure ratio, and intake temperature. As rotational speed increases, mass flow rate increases. However, with an increase in the pressure ratio and intake temperature, the mass flow rate decreases.
3. Considering high efficiency and low energy consumption, the optimal combination of operational parameters is a rotational speed of 50,000 rpm, a pressure ratio of 1.4, and an intake temperature of 18.3 \({}^{\circ}\)C. At these optimal operational parameters, the isentropic efficiency improved by 42.18%, while power consumption decreased by 44.92%.
4. Considering the high mass flow rate and low energy consumption, the optimal combination of operational parameters is a rotational speed of 80,000 rpm, a pressure ratio of 1.0, and an intake temperature of 18.8 \({}^{\circ}\)C. At these optimal operational parameters, the mass flow rate increased by 95.1%.  
Figure 14: Comparison of the optimization results with the initial sample average values.  
When considering a high flow rate, high efficiency, and low energy consumption simultaneously, the optimal combination of operational parameters is a rotational speed of 80,000 rpm, a pressure ratio of 1.8, and an intake temperature of 18.3 \({}^{\circ}\)C. Compared to the average values, at half the increase in power consumption, the mass flow rate increased by 78.88%, and the isentropic efficiency increased by 48.23%.  
The research findings mentioned above provide valuable insights into the efficient operation of the air compressor under various demands from the fuel cell stack. The comprehensive multi-factor, multi-objective research method proposed in this paper is applicable to other optimization studies concerning air compressors in HFCVs. In addition, air compressors can be affected by transient conditions, including start-stop phases, load fluctuations, sudden pressure changes, and temperature variations. To address these, advanced control systems, variable speed drives, system modeling, optimized component design, and monitoring with predictive maintenance need to be investigated further to enhance efficiency and stability.  
T.S.: conceptualization, data curation, formal analysis, writing--original draft, writing--review and editing; X.P.: project administration, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This paper is supported by the National Natural Science Foundation of China (Grant No. 52276036).  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
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.