Entrainment and flow performance study of a novel shark-gill bionic ejector for a PEMFC hydrogen supply system

Proton exchange membrane fuel cell (PEMFC) technology stands as the core enabling hydrogen energy technology. The ejector, key component of PEMFC anode hydrogen supply system, is primarily responsible for recovering unreacted hydrogen from the fuel cell stacks. Low entrainment ratio (ER) weakens ejector and overall performance significantly. A novel bionic ejector inspired by shark gills was proposed to improve ER. The impact of key structural parameters on ER was analyzed. The optimal parameter ranges enhancing performance effectively were identified. Results show that the bionic ejector directs primary flow more effectively, reduces fluid resistance, enhances stability, and improves overall performance, albeit with a decrease in primary flow mass flow. The optimal ranges of gill number ratio, length ratio, height ratio, and width ratio remained 0 to 0.182, 0 to 0.28, 0 to 0.4, and 0 to 0.14, respectively. Within these ranges, the ER increased by 8.92 %–16.83 %, while the primary flow mass flow decreased by 6.25 %–8.75 %. Distinct design strategies are recommended based on pressure: small gill number, gill length, gill height, gill width, and non-vertical angle are favored for low pressure; for high pressure, high gill number, long gill length, great gill height, wide gill width, and vertical angle (90°) are optimal.