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ABSTRACT
Considering the characteristics of the hydrogen ejector for proton exchange membrane fuel cell system used in vehicles, with the aim of expanding the operating range, the ejector structure parameters are comprehensively analyzed and optimized. The results indicate that reducing the throat diameter can expand its operating range. When the working conditions change significantly, the convergent nozzle should be selected, the convergence length and throat length of the nozzle have little effect on the ejection performance. There are optimal suction chamber convergence length (8 mm), diffuser divergent angle (7.1°) and length (33.8 mm), nozzle exit position (−7 mm) in variable working conditions to achieve good ejection performance. Reducing the diameter and length of the mixing chamber is beneficial for expanding the operating range. Before ejector optimization, when the primary fluid mass flow rate is less than the design value, the ejection performance deteriorates sharply with the decrease of the flow rate. When the primary fluid mass flow rate is lower than 0.4 g/s, the non-optimization ejector is backflow, the maximum ejection ratio is about 1.8 and the maximum hydrogen ejection ratio is about 0.67 in the operating range. After optimization, the ejector performance is stable. Under the set operating conditions, the hydrogen ejection ratio is greater than 0.75, the maximum ejection ratio is 3.8, and the maximum hydrogen ejection ratio is 1.01.
Nomenclature
| D | = | diameter |
| f | = | area |
| k | = | adiabatic exponent |
| L | = | length |
| m | = | mass flow rate |
| P | = | pressure |
| q | = | converted mass velocity |
| T | = | temperature |
| w | = | velocity |
| y | = | mass fraction |
| ρ | = | density |
| π | = | relative pressure |
| θ | = | angle |
| ε | = | ejection ratio |
| Abbreviation | = | |
| NXP | = | nozzle exit position |
| PEMFC | = | proton exchange membrane fuel cell |
| RH | = | relative humidity |
| Subscript | = | |
| a | = | secondary flow entrance |
| c | = | diffuser |
| c3 | = | outlet of the mixing chamber |
| e | = | secondary flow |
| i | = | nozzle entrance |
| m | = | constant-area mixing chamber |
| max | = | maximum |
| n | = | nozzle throat |
| p | = | primary flow |
| p1 | = | outlet of the nozzle |
| s | = | suction chamber |
| H2 | = | hydrogen |
| H2O | = | water vapor |
| 1 | = | nozzle convergence section |
| 2 | = | nozzle divergence section |
Acknowledgements
The computation is completed in the HPC Platform of Huazhong University of Science and Technology.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Funding
Notes on contributors
Aihua Wu
Aihua Wu, School of energy and power engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, e-mail address: [email protected]
Zian Hao
Zian Hao, School of energy and power engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, e-mail address: [email protected]
Guogeng He
Guogeng He, School of energy and power engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, e-mail address: [email protected]
Dehua Cai
Dehua Cai, School of energy and power engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, e-mail address: [email protected]