BIT team develops optimal control strategy for hydrogen engine; near-zero NOx with high power and BTE
A team from the Beijing Institute of Technology (BIT) has devised a control strategy for 2.0L direct-injection hydrogen engines that delivers near-zero emissions with high power and high brake thermal efficiency. A paper on their work is published in the journal Fuel.
Direct-injection (DI) hydrogen engines can generate high power with high thermal efficiency and a low risk of abnormal combustion. However, although hydrogen is carbon-free, eliminating many criteria pollutants, the emission of nitrogen oxides (NOx) remains at a high level in DI hydrogen engines at high loads.
Some studies have targeted reducing NOx emissions based on naturally aspirated or supercharged engines with medium power and efficiency.
In contrast, the present study focuses on a 2.0 L turbocharged direct-injection engine, achieving large power, high thermal efficiency, and near-zero emissions (below 20 ppm without any posttreatment equipment) simultaneously.
The impacts of two effective methods, lean combustion, and retarded ignition are investigated, compared, and combined. An optimal control strategy is proposed and validated under all working conditions from 1000 rpm to 3500 rpm to deal with the trade-off among the power, efficiency, and emissions.
The results indicate that lean combustion can rapidly decrease the NOx emission from 2500 ppm to approximately 100 ppm by reducing the cylinder temperature, avoiding the formation of thermal NOx.
On this basis, retarded ignition effectively reduces remaining emissions to near-zero with only a 2.5% power loss, whereas lean combustion achieves the maximum brake thermal efficiency (BTE). After optimization, a maximum torque of 221 N·m @ 2500 rpm, 73 kW @ 3500 rpm, and 41.2% BTE @ 2000 rpm and 2500 rpm can be achieved by the turbocharged direct-injection hydrogen engine with near-zero emission.—Bao et al.
Ling-zhi Bao, Bai-gang Sun, Qing-he Luo (2022) “Optimal control strategy of the turbocharged direct-injection hydrogen engine to achieve near-zero emissions with large power and high brake thermal efficiency,” Fuel, Volume 325, doi: 10.1016/j.fuel.2022.124913